Corporate Loop Example

Presented here is the Corporate Loop example project from tfdvd.com reauthored in TFDVDEdit 2.

» Click here to download example files for this project.

This project plays up to four tracks continuously, such as for a trade show, allowing the user to choose which combination of tracks to play. The tracks, if played, are always played in the same sequence.

For this example we nuked the abstraction layer commands before beginning. We also used a binary bit for each title, which makes the implementation much easier than other methods.

For this project we used 7 registers, as follows:

R0  Scratch
R1  Menu number, 1, 2, or 3
R2  Button number for menu 1, 1-3
R3  Button number for menu 2, 1-6
R4  Button number for menu 3, 1-11
R5  Current track bit mask, 1, 2, 4, or 8
R6  Play list bit mask, any 0-15

This project remembers the last button number activated, not counting the links between menus, for each menu. This results in each menu showing the last button that was used for that menu when it is reentered for any reason.

The values of 1, 2, 4, and 8 are significant because they are powers of two, which also means that they each have only one bit present. In binary they are:

1  0001
2  0010
4  0100
8  1000

What we are going to do with the play list mask is to turn on the appropriate bit for each title that we want to play. This yields the following possible play lists:

0  0000  Play nothing (not used in our example)
1  0001   Play title 1
2  0010  Play title 2
3  0011  Play titles 1 and 2
4  0100  Play title 3
5  0101  Play titles 1 and 3
6  0110  Play titles 2 and 3
7  0111  Play titles 1, 2, and 3
8  1000  Play title 4
9  1001  Play titles 1 and 4
10  1010  Play titles 2 and 4
11  1011  Play titles 1, 2, and 4
12  1100  Play titles 3 and 4
13  1101  Play titles 1, 3, and 4
14  1110  Play titles 2, 3, and 4
15  1111  Play all four titles

So, for each play button in each menu, all we need to do is select the correct value from the above list, and the Boolean logic in just two PGCs will do the rest.

First Play PGC

#TFDVDEDIT Commands V1
#PreCommands from "CorporateSimple:First Play PGC:"
1:  Set r1 = 1
2:  Set r2 = 1
3:  Set r3 = 1
4:  Set r4 = 1
5:  Jump VTS 1 Menu Root

This initializes the menu and button registers to their default values, then jumps to the root menu in VTS 1. If you check the PGCs in VTS 1, only one menu will have the root designation. The other three PGCs, which are the three actual menus, are designated non-entry PGCs.

VTS 1 VTSM PGC 1 (root)

#TFDVDEDIT Commands V1
#PreCommands from "CorporateSimple:Video Title Set Menus:Title Set 1 Menus:English (4 menus):VTSM PGC 1:"
1:  if  r1 <= 1 then Link PGC 2
2:  if  r1 == 2 then Link PGC 3
3:  Link PGC 4

The root menu links to one of the three actual menus, depending on the value of r1.

VTS 1 VTSM PGC 2 (non-entry)

#TFDVDEDIT Commands V1
#PreCommands from "CorporateSimple:Video Title Set Menus:Title Set 1 Menus:English (4 menus):
VTSM PGC 2 (1 program):"
1:  Set r0 = r2
2:  Set r0 *= $400
3:  Set Button r0
4:  Set r1 = 1

This is the Title Menu, which offers three choices: to loop all of the tracks, to choose a single track, or to choose multiple tracks.

The pre commands decode the button number in r2 and highlights that button. Remember the button number must be multiplied by 1024 before storing in the system parameter, SPRM 8. Then it sets the menu number to 1, the first menu.

In DVDSP 2 we hooked up all of the buttons in all of the menus to something, even though we threw away the abstraction layer commands that were generated from doing this. This has the useful side-effect of generating a LinkTailPGC button command in each menu Nav pack, which transfers control to the PGCs post commands when the button is activated.

#PostCommands from "CorporateSimple:Video Title Set Menus:Title Set 1 Menus:English (4 menus):
VTSM PGC 2 (1 program):"
1:  Set r2 = Button
2:  Set r2 /= $400
3:  if  r2 != 1 then GoTo Line 7
4:  Set r5 = 1
5:  Set r6 = $f
6:  Jump VTS TT 1
7:  if  r2 != 2 then GoTo Line 9
8:  Link PGC 3
9:  if  r2 != 3 then GoTo Line 11
10:  Link PGC 4
11:  Jump First Play

This reads the button number that was activated back out from SPRM 8 and divides by 1024 to get the simple button number. This is done directly in r2 so that the next time we enter this menu the same button that was activated will be selected when the menu is displayed.

Then if the first button was activated, (Loop All tracks), it sets r5 to 1. This means start at track 1, which is designated by the binary value 0001.

R6 is set to 15, all four bits on. This means play all four tracks.

It then jumps to the first title within the current VTS, which is VTS 1. This is because DVDSP 2 always puts all 4:3 menus in VTS 1. Since the track we want is also in the same VTS, we can jump there directly instead of navigating through the Video Manager domain which we will do when the target track is not in VTS 1.

If button 2 or 3 was activated, we link to another menu. The Jump to First Play is a safety valve in case the register had a value we didnt expect. It would be better practice to create a debugging menu for this purpose, so you could know for sure that you had a scripting error.

VTS 1 VTSM PGC 3 (non-entry)

#TFDVDEDIT Commands V1
#PreCommands from "CorporateSimple:Video Title Set Menus:Title Set 1 Menus:English (4 menus):
VTSM PGC 3 (1 program):"
1:  Set r0 = r3
2:  Set r0 *= $400
3:  Set Button r0
4:  Set r1 = 2

This menu offers to loop each one of the four tracks, link to a multiple track loop menu, or return to the title menu.

It uses r3 to choose which button to highlight, and sets r1 to indicate we are on the second menu.

#PostCommands from "CorporateSimple:Video Title Set Menus:Title Set 1 Menus:English (4 menus):
VTSM PGC 3 (1 program):"
1:  Set r0 = Button
2:  Set r0 /= $400
3:  if  r0 != 5 then GoTo Line 5
4:  Link PGC 4
5:  if  r0 != 6 then GoTo Line 7
6:  Link PGC 2
7:  Set r3 = r0
8:  if  r0 != 1 then GoTo Line 12
9:  Set r5 = 1
10:  Set r6 = 1
11:  Jump VTS TT 1
12:  if  r0 != 2 then GoTo Line 16
13:  Set r5 = 2
14:  Set r6 = 2
15:  Jump VMG PGC 2
16:  if  r0 != 3 then GoTo Line 20
17:  Set r5 = 4
18:  Set r6 = 4
19:  Jump VMG PGC 2
20:  if  r0 != 4 then GoTo Line 24
21:  Set r5 = 8
22:  Set r6 = 8
23:  Jump VMG PGC 2
24:  Jump First Play

When the user activates a button, control is transferred to the post commands. Here we test which button was hit by using r0, not r3. This is so we do not destroy the current contents of r3 if we choose to link to another menu. That way, this menu will always remember the last single track that was played from this menu, or be set to the default of Track 1.

First we check for the link to the multiple tracks menu, or to return to the previous (Title) menu. Once we are sure that it is neither of these, we go ahead and set r3 for the next time.

Then for each of the possible four tracks, we set both r5 and r6 to the same value: 0001, 0010, 0100, or 1000. This will result in a single track looping forever or until the user hits a button on the remote. (We expect the Menu or Title button). We then link to the first of the Boolean logic PGCs.

VMG PGC 2

#TFDVDEDIT Commands V1
#PreCommands from "CorporateSimple:Manager Menus:English (3 menus):VMG PGC 2:"
1:  Set r0 = 1
2:  if  r5 & r0 then Jump TT 1
3:  Set r0 = 2
4:  if  r5 & r0 then Jump TT 2
5:  Set r0 = 4
6:  if  r5 & r0 then Jump TT 3
7:  Set r0 = 8
8:  if  r5 & r0 then Jump TT 4
9:  Jump First Play

Each pair of commands tests for the presence of a single bit in the current track register. It does so by doing a Boolean logical and with the value representing the bit we want to test for.

Because of restrictions in the DVD Spec on the format of commands, we must first put the value to be tested in another register; we cannot test directly for the value 1, for example, when combined with the Jump TT command.

So, what does r0 & r5 mean? It means, does at least one bit in the same position exist in both registers. It doesnt matter which register is named first or second, r0 & r5 means the same thing as r5 & r0.

Since we are concerned with only only four tracks, we can ignore the zeros that are in the high order bits of the two registers. Also since we know that only one bit can be present in each register (we deliberately set it up that way), the only possible legal values for r5 are:

0001
0010
0100
1000

The logical and says that the bit in each position is compared with the same bit in the other register, and if both bits are on, the resulting bit is set on. So we can see that in the very restricted case we are testing, the & comparison has the same result as the == comparison. We will give more examples in VMG PGC 3 when we get to it.

So, after testing the current track register, we jump to one of the Tracks. Each track is set up in exactly the same way, it plays through once and then control is passed to its post commands. Each track has exactly one and only one post command, and no other commands of any type.

VTS 1 PGC 1 TT1

VTS 4 PGC 1 TT1

#TFDVDEDIT Commands V1
#PostCommands from "CorporateSimple:Video Title Sets:VTS 1:PGC 1 TT 1:"
1:  Call VMG PGC 3 resume C1

This transfers control to the Video Manager routing PGC, and saves the current resume point, cell 1 of the track.

VMG PGC 3 (non-entry)

#TFDVDEDIT Commands V1
#PreCommands from "CorporateSimple:Manager Menus:English (3 menus):VMG PGC 3:"
1:  Set r5 *= 2
2:  if  r5 <= r6 then GoTo Line 4
3:  Set r5 = 1
4:  if  r5 & r6 then Link PGC 2
5:  GoTo Line 1

This is the other Boolean logic PGC. Its purpose is to check the tracks in sequence starting from the track just played and find the next track to play.

First we multiply the current track value (remember, 1, 2, 4 or 8) by two. This is what is known in Boolean programming as shifting the register left by one position. Here are the possible results:

Before     Shifted left

0001         0010
0010         0100
0100         1000
1000         10000

The next command compares the result to the play list mask, which can only have a value from 1 to 15. Since the play list mask must have contained the track just played, this command will branch (goto line 4) only if the result is possibly within the highest track number in the play list.

For example, if the play list is 0011 (play tracks 1 and 2) and the current track was 0001, it is becomes 0010 and that is less than 0011, so it branches. If the current track was 0010, it becomes 0100 and that is greater than 0011, so it does not branch.

If it did not branch, the current track is set to 0001, to start the testing all over again.

The next line does a logical and of the current track and the play list. If the bit in the current track is on in the play list, it links to PGC 2 and plays that track. If not, it repeats the entire command list.

Since we know the play list contains at least one bit, the loop is guaranteed to find a bit every time, even if it is the same bit it just played. (A single track was selected).

This concludes the Boolean logic. Once you understand these methods, they can be applied to many DVD authoring problems.

VTS 2 VTSM PGC 1

VTS 4 VTSM PGC 1

The remaining Video Title Set Menu PGCs are all identical, and are used to direct navigation back to the right place when the user hits the Menu Key on the remote. Note that these are all root menus.

#TFDVDEDIT Commands V1
#PreCommands from "CorporateSimple:Video Title Set Menus:Title Set 4 Menus:English (1 menu):VTSM PGC 1:"
1:  Jump VMG PGC 4

Since the DVD Spec prohibits direct jumps between Video Title Sets, we jump to the Video Manager in order to jump back to the root menu of VTS 1.

VMG PGC 4

#TFDVDEDIT Commands V1
#PreCommands from "CorporateSimple:Manager Menus:English (4 menus):VMG PGC 4:"
1:  Jump VTS 1 Menu Root

The only remaining PGC in the project is the Video Manager Title Menu, which is where navigation is directed when the user hits the Title Key on the remote.

VGM PGC 1

#TFDVDEDIT Commands V1
#PreCommands from "CorporateSimple:Manager Menus:English (4 menus):VMG PGC 1:"
1:  Set r1 = 1
2:  Jump VTS 1 Menu Root

We add the wrinkle here to set the current menu register r3 to the first menu, the Title Menu. Thus the Title Key on the remote will always take you back home, and the Menu Key on the remote will take you to the last menu visited.

Also notice that the Menu Key will toggle between playing the selected titles and returning to the menu where those titles were selected. That is because of the Call VMG PGC 3 resume C1 command that was executed after the playing of each track that command sets up the SPRMs to return execution to that track and cell when the Menu Key is hit. This example is much simpler than the abstraction layer version would have been, because only one set of variables are used, the memory variables are always self-consistent and represent a valid state of execution, and the commands are able to branch (jump, call, link, or goto) exactly the area they wish to.

Although this example uses seven registers, it could have compressed r1 through r4 into a single register if registers had been at a premium, using Boolean methods of bit extraction and replacement. A later example will illustrate these methods.

Larry

DVD Studio Pro 2.0 Abstraction Layer

The DVD Studio Pro 2.0 Abstraction layer uses a highly structured template approach. Many of the command sequences are identical in every project, or only differ in the values tested for at the end of the sequence.

Registers

The abstraction layer uses eight general registers (GPRMs) to keep track of things, registers 0 thru 7. It uses the other 8 GPRMs , registers 8 thru 15, for user scripts. The user scripts in DVDSP 2 refer to these registers as GPRM 0 thru GPRM 7, but they are actually r8 thru r15 in the DVD Spec commands.

R0 and r1 are used as scratch registers, which means that command sequences use them to decode what is in other registers so that the other registers are not destroyed. Register 1 is also sometimes used as a parameter passed from one PGC to another. Neither of these registers is ever relied upon between video plays. This means that TFDVDEdit 2 authors are free to use these registers as scratch or parameter registers also.

R2 is used as a parameter. Much of the code that tests r2 is never reached by the projects that I have checked. This would imply that DVDAfterEdit authors could use r2 to retain values between video plays, as long as their code is the first code executed after the play, and they clear it before going to abstraction layer code.

R3 is usually the Title Number.
R4 is probably the Sub picture stream number.
R5 is usually the Chapter Number.

R6 is the GetLastItem register. The abstraction layer code sets r6 to a unique value before playing video. Its use will be covered as we encounter it in the command sequences.

R7 is often set to be the same as r6. No code that tests r7 has been found yet.

All of the conclusions above and below are subject to change as we learn more about the abstraction layer.

First Play PGC

The first play PGC jumps to the asset that the user selected in DVDSP 2, after setting some register values that the abstraction layer will test.

Manager Menus

Every DVDSP 2 project has exactly eight Manager Menus, which are always used in the same way. Often a menu will be blank (contain no commands) if the feature supported by that menu is not used. So far there are no examples of code in PGCs 3, 5, or 7, though there are links to those PGCs that are never executed, since the register tested never contains the appropriate value to cause the link.

VMG PGC 1

This PGC is often similar to the first play PGC.

VMG PGC 2

This PGC is always the same in every project, except for the number of Titles in the project. A project with 6 Titles would read thus:

#Selected from PlayAllProject:Manager Menus:English (8 menus):VMG PGC 2:
1: Set r1 = 0
2: Set r2 = 0
3: if r3 & $ff00 then GoTo Line 5
4: GoTo Line 8
5: Set r5 = r3
6: Set r5 /= $100
7: Set r3 &= $ff
8: if r3 >= 6 then Link PGC 3
9: Set r0 = 1
10: if r0 == r3 then Jump TT 1
11: Set r0 = 2
12: if r0 == r3 then Jump TT 2
13: Set r0 = 3
14: if r0 == r3 then Jump TT 3
15: Set r0 = 4
16: if r0 == r3 then Jump TT 4
17: Set r0 = 5
18: if r0 == r3 then Jump TT 5
19: Jump First Play


We will examine this PGC in detail:

1: Set r1 = 0
2: Set r2 = 0


These instructions clear parameters that might be checked later.

3: if r3 & $ff00 then GoTo Line 5
4: GoTo Line 8


Line 3 tests to see if there is anything in the high-order byte of r3. If there is, it does further decoding at line 5. If there is not, it assumes that r5 and r3 are already fully prepared by the code that came here, and goes to the code which follows the decoding.

5: Set r5 = r3
6: Set r5 /= $100


This moves the high byte of r3 to r5, putting it in the low byte.

7: Set r3 &= $ff


This isolates the Title Number to be a value between 0 and 255.

8: if r3 >= 6 then Link PGC 3


This says if the title number is too large, go to PGC 3, which is empty. Presumably PGC3 could contain error recovery code, or could do something useful with values greater than 99 but less than 256, since the DVD Spec allows only 99 titles.

9: Set r0 = 1
10: if r0 == r3 then Jump TT 1
11: Set r0 = 2
12: if r0 == r3 then Jump TT 2
13: Set r0 = 3
14: if r0 == r3 then Jump TT 3
15: Set r0 = 4
16: if r0 == r3 then Jump TT 4
17: Set r0 = 5
18: if r0 == r3 then Jump TT 5


Each pair of commands checks for a particular Title Number in r3 and jumps to that Title if the number matches.

19: Jump First Play


One possible value of r3 is unaccounted for zero. In that case the DVD starts over at the First Play.

VMG PGC 4

This PGC jumps to a particular VTSM PGC depending on the value of r1. Sometimes there is only one interesting PGC, so r1 is not tested in that case. Often this PGC is called by the Post Commands of a Title. It can also be linked to from VMG PGC 8. Here is an example:

#Selected from PlayAllProject:Manager Menus:English (8 menus):VMG PGC 4:
1: Set r5 = 0
2: Set r2 = 0
3: if r1 >= 4 then GoTo Line 5
4: Jump VTS 1 VTS TT 1 Menu Root
5: Jump VTS 5 VTS TT 1 Menu Root
6: Jump First Play


Obviously the Jump First Play can never be reached. There is likely a more complex situation that could result it being used.

VMG PGC 6

This PGC is very similar to PGC 4, but uses r2 to determine the branch. Here is an example:

#Selected from PlayAllProject:Manager Menus:English (8 menus):VMG PGC 6:
1: Set r5 = 0
2: Set r1 = 0
3: if r2 >= $c then GoTo Line 5
4: Jump VTS 1 VTS TT 1 Menu Root
5: Jump VTS 5 VTS TT 1 Menu Root
6: Jump First Play


VMG PGC 8

This is the longest script in the abstraction layer, but we have not found a link to it yet in the simple projects we have examined. I deleted it from a project and verified to make sure that it wasnt referenced.

It is identical in all projects except for some of the values tested. It is particularly interesting for its splitting up of r2 into subfields, so we will examine it in detail.

#Selected from PlayAllProject:Manager Menus:English (8 menus):VMG PGC 8:
1: Set r0 = r2
2: Set r2 = 0


This moves the value of r2 to r0 in order to test it, and clears r2. The clearing of r2 is probably so that the same parameter would not be processed again if we came back here.

3: if r0 != $fff0 then GoTo Line 5
4: Link Resume


This tests for a single value in order to do a resume.

5: Set r3 = r0
6: Set r3 &= $f800
7: if r3 != $f800 then GoTo Line 15


This uses r3 as a scratch register to test r0, which originally came from r2. Then the lower 11 bits of r3 are masked off, so that we can test the higher 5 bits. If they are not all on, we skip over a fairly long section of code.

8: Set r3 = 0
9: Set r2 = r0
10: Set r2 &= $7ff
11: if r2 >= $c then Link PGC 7
12: Link PGC 6
13: Nop
14: Nop


We take the 11 bits that were masked off and isolate them into r2. Then if the value in them is greater than 12, we link to PGC 7. Otherwise we link to PGC 6. (Ignore the Nops). Since we havent seen an example of PGC 7 yet, we are missing a lot of the details.

15: Set r3 = r0
16: Set r3 &= $c000
17: if r3 != $c000 then GoTo Line 30


We now test to see if the high order 2 bits are on. Notice that we tested for the high order 5 bits earlier, which would have taken precedence.

18: Set r3 = 0
19: Set r3 = r0
20: Set r3 &= $3f80
21: Set r3 /= $80
22: Set r5 = r0
23: Set r5 &= $7f
24: Set r5 += 1
25: Link PGC 2
26: Nop
27: Nop
28: Nop
29: Nop


We isolate 7 bits in the middle, and move them to the lower part of r3. That must be a Title Number, since it takes 7 bits to show a value from 1 to 99. (We also noticed a Title Number in r3 in another PGC, earlier).

We then isolate the Chapter Number and put it in r5, and link to PGC 2. Notice that the value in the register was actually the chapter number minus one, since it added one to it.

If we look back at PGC 2, we will see that it uses the value in r3 to decide which Title to jump to. If we look ahead to the Title Set PGCs, we will see they use r5 to decide which Chapter to jump to.

30: Set r3 = 0
31: Set r1 = r0
32: Set r1 &= $ffe0
33: Set r1 /= $20
34: Set r4 = r0
35: Set r4 &= $1f
36: Set r4 += 1
37: if r1 >= 4 then Link PGC 5
38: Link PGC 4


The remaining case is when the two high order bits are not both on. The value is split into the high-order 11 bits in r1 and the lower 5 bits in r4. R4 is probably the sub picture stream number. Then depending on the value in r1, it links to either PGC 5 or PGC 4.

This concludes the Video Manager PGCs for now. Next will be an analysis of the Video Title Set Menu PGCs.

Editing in DVDAfterEdit

You can edit most items in the right-hand pane of the window simply by clicking on their current value to get a text editing field, and typing a new value. Editing actions such as copy and paste work within these text fields as you expect.

In addition, some items within expandable groups have additional editing actions, to allow you to manipulate the groups as a whole, or to manipulate several items at once. The following kinds of items have additional editing actions: Prohibited User Ops, ISRC, Button Highlights, Colors, Color Schemes, Button Navigations, and Pre/Post/Cell Commands.

Using the Clipboard

This section applies to Prohibited User Ops, ISRC, Button Highlights, Colors, Color Schemes and Button Navigations. These are called copyable items, because they can all be copied to the clipboard, and of course pasted again later. Pre/Post/Cell Commands work a little differently, and are discussed in a separate section.

You place a copyable item on the clipboard by selecting it and choosing Copy from the Edit menu. You paste it by selecting any item of the same type and choosing Paste Over from the Edit menu.

Copying Multiple Items

You can also copy multiple Colors, Color Schemes and Button Navigations to the clipboard. First, select the ones you want (they must all be in the same item list): click to select, shift-click to select multiple items and command-click to select or unselect individual items. Note that the selection does not have to be contiguous, meaning you can have selected items with unselected items between them in the list. Then choose Copy from the Edit menu to place all of the selected items on the clipboard.

To paste multiple items, first select the items to you want to change. Again, they must all be in the same item list, but they don't have to be contiguous. Then choose Paste Over from the Edit menu, and the selected items are replaced in turn by the items on the clipboard. The first selected item is replaced by the first selected clipboard item, and so on. If there are fewer items selected than are on the clipboard, the excess clipboard items don't have any effect. If there are more items selected, the excess selected items aren't changed.

Copying Item Groups

Colors, Color Schemes and Button Navigations are arranged in groups (of 16, 3 and 36 items, respectively). You can copy and paste the entire group by selecting just the group item (that is, the one that expands to show the individual Colors, Color Schemes or Button Navigations) and using Copy and Paste Over from the Edit menu. Copying an entire group is no different from copying all of the component items. So, you can copy a group and paste over another group, or over individual items (remember: excess items are ignored when pasting), and you can copy all of the individual items and paste over a group item.

There is just one special consideration to keep in mind when doing this. You can only paste over a group item if there are enough individual items on the clipboard. This means you can only paste a Colors group item if you copied all 16 Colors in some other group (or if you copied a Colors group item, which amounts to the same thing). Similarly, you have to copy all 3 Color Schemes to be able to paste over a Color Schemes group item, and copy all 36 Button Navigations to paste over a Button Navigations group.

Paste Into

When you copy items from the right pane of the window to the clipboard, you can paste them into certain items in the left pane. Colors and Prohibited User Ops can replace similar items in program chains (PGCs) and dummy PGCs, while all of the kinds of copyable items can be pasted into navpacks. Simply select a right-pane item, choose Copy from the Edit menu, then select the PGC or navpack you want and choose Paste Into from the Edit menu.

For Colors, Color Schemes and Button Navigations, Paste Into works with item groups, which were discussed in the previous section. You have to select the entire group (the group item, or all of the items in the group) in order to be able to use Paste Into.

Paste Repeated

Sometimes you might want to paste a clipboard item more than once. For example, you might want to copy a single Color to the clipboard, then use it to replace all 16 Colors in a group. Or, you might want to copy a Color Schemes group, and paste it into multiple navpacks.

Paste Repeated on the Edit menu allows you to do these things. It can be used whenever Paste Over or Paste Into is allowed, if you have more items selected than are on the clipboard. When you choose Paste Repeated from the Edit menu, items from the clipboard are pasted over or into what is selected until they are all used. Then the items on the clipboard are used again for the next selected items, and again for the next, until all of the selected items have been changed.

Paste Deeply Into

Sometimes you might want to paste a clipboard item from a Nav Pack into all of the Nav Packs for (another) cell. Paste Deeply Into allows you to do this.

For copying and pasting of Nav Pack information, you must copy the information from a single Nav Pack. Then you can select a contiguous range of Nav Packs, and Paste Repeated into them as described above. For Paste Deeply Into, you may choose one or more cells, without having to open up the individual Nav Packs and select them, and then paste (Deeply) the Nav Pack info into all Nav Packs in those cells. You may also choose one or more Programs in order to Paste Deeply Into all Nav Packs in all cells of the Programs chosen. This function capability is NOT implemented at the PGC level or above.

For Button Highlight Information, Pasting Deeply Into will set the Button Highlight Status on the first Nav Pack of each cell to "All New Info", and subsequent cells to "Use Previous Vobu".

Pre/Post/Cell Commands

Pre/Post/Cell Commands can be copied and pasted in much the same way as other copyable items, but since they can also be deleted and inserted, you have more editing actions available to you: Paste After, Edit Command, Insert Command and Delete Command, as well as unlimited Undo and Redo.

Copy, Cut and Paste

You can select one or multiple Commands (Pre, Post or Cell) in a list of commands, and choose Copy from the Edit menu to place them on the clipboard. As before, your selection does not have to be contiguous. If you choose Cut from the Edit menu instead of Copy, the selected items are deleted after being copied to the clipboard.

You paste Commands by selecting one or more Commands in a list and choosing Paste from the Edit menu. Note that the menu says Paste instead of Paste Over, because pasting Commands is more like the regular text pasting you're already familiar with: the contents of the clipboard replaces whatever is selected. Depending on how many Commands are on the clipboard and how many selected, you may end up with more or fewer Commands in the list.

The Pre, Post or Cell Commands group item can be copied to the clipboard all of the Commands in the list are copied but currently, you cannot paste over a group item, but must select the individual Commands instead. This also means that you cannot paste Commands directly into PGCs in the left pane of the window. Instead, you must navigate to the PGC you want and select the appropriate Commands in the right pane before pasting.

Paste After

In normal text editing, you can always paste text from the clipboard between any two characters by clicking between them to place a flashing insertion point. Currently, there is no way to set an insertion point between two Commands in the right pane, so you have to follow a different strategy to paste Commands between existing Commands.

First, select the Command after which you want to paste the contents of the clipboard. To paste before the first command in a list, or into an empty list, just select the Commands group item at the top of the list. Then choose Paste After from the Edit menu, and the Commands on the clipboard are inserted after the selected item. (If you happened to have selected more than one item, the clipboard contents are inserted after the last selected item.)

Pasting Non-Contiguous Selections

If you have a non-contiguous selection (that is, unselected Commands interspersed between selected ones), its not obvious where you would expect pasted Commands to be placed. What actually happens is governed by a simple rule:

The first Command on the clipboard replaces the first selected Command, and so on until there are no more Commands on the clipboard or no more selected Commands. Then, if there are any remaining Commands on the clipboard, they are pasted after the last selected Command. Or, if there are any remaining selected items, they are deleted.

In fact, this same rule applies to all pasting of Commands, because it produces the expected result if the selection is contiguous.

Paste Repeated

Paste Repeated on the Edit menu works for Commands exactly as it does for other copyable items. Keep in mind that the number of Commands never changes as a result of this action, because only the selected items are affected.

Insert and Delete

Inserting a Command into a list is a little like pasting after: select the Command you want to insert after (or the Commands group item to insert before the first command), and choose Insert Command from the Edit menu and a Nop command is placed in after the selected item.

To delete Commands, select the ones you want to remove from the list and choose Delete Command from the Edit menu. The keyboard shortcut for this action is the Delete key (either Delete key if your keyboard has two).

Insert Command and Delete Command are also available on a contextual menu. After making a selection, control-click with your mouse (or just click the right button if your mouse has more than one button), and a menu will pop up from which you can choose the desired editing action.

Edit

You can edit a Command in one of two ways: with popup menus and with the Command assembler. With popup menus, you construct the Command by choosing the various parts of it from menus, and the menus change according to what you choose. With the Command assembler, you type the whole Command in a text field.

To start popup editing, expand the Command item by clicking on its expansion icon at the left of its command number. The item doesn't exactly expand, but it replaced by a series of popup menus. You can alternatively start popup editing by selecting the Command and choosing Edit Command from the contextual menu described in the previous section. Click on some other item to return to normal.

To start the Command assembler, just click on the text of the Command itself. Press Return or click elsewhere to return to normal.

Undo and Redo

All of the editing actions that change Commands edit, insert, delete, cut, paste and paste after are undo-able. Just as copying and pasting of Commands is not exactly like normal copying and pasting, undoing and redoing of Commands is not exactly like normal undoing and redoing.

After you make a change to Commands, you can undo the change by choosing Undo from the Edit menu. If you've made a series of changes, you can undo them one by one to go back to any previous state of the Commands. Once you've undone changes, you can redo them one by one, if you wish, by choosing Redo from the Edit menu.

Undoing is unlimited: you can undo all of the actions you made since you opened the VIDEO_TS file shown in the window.

Here's how undoing Commands is different from normal undoing: undoing is separate for each list of Commands. Undo doesn't function until you select a Command list that you've changed (or any Command in it), and then it only undoes the changes you've made to that list. If you select a different list, you can only undo changes you made to that list, and so on. However, it makes no difference how often you select something else and come back to a changed list all of the changes you made in that list since opening the window will be there waiting for you to undo or redo them.

From Simple to Play All: A DVDSP 2 Abstraction Layer Example

In analyzing the DVDSP 2 abstraction layer, it is easiest to start with a very simple project. First we will step through the Simple project on paper and examine how the abstraction layer commands accomplish their navigation. Then we will add commands with DVDAfterEdit to implement a Play All button, using mostly the abstraction layer registers themselves.

This document contains two sections: an analysis of the DVDSP 2 abstraction layer, and instructions for turning a VIDEO_TS folder built from the Simple project into the Play All version.

» Click here to download example files for this project.

You may skip the first section if all you want to do is use this project as a template; the instructions alone are sufficient to achieve this goal.

First Play PGC

The Simple project contains the following First Play commands:

#DVDAfterEdit Commands V1
#Selected  from "Simple:First Play PGC:"
1:	Set r5 = $2000
2:	Set r4 = 0
3:	Set r1 = 1
4:	Jump VTS 1 VTS TT 1 Menu Root

Examining the menus for Title Set 1, we see that VTSM PGC 1 has the Menu Type designation root. So this must be the target. It says:

#DVDAfterEdit Commands V1
#Selected  from "Simple:Video Title Set Menus:Title Set 1 Menus:English (7 menus):VTSM PGC 1:"
1:	if  r5 == $4000 then Link PGC 3
2:	Set r5 = 0
3:	if  r1 != 0 then Link PGC 6
4:	if  r2 != 0 then Link PGC 5
5:	Set r0 = VTS title
6:	Set r0 *= $100
7:	Set r0 |= Part title
8:	Nop
9:	Nop
10:	Nop
11:	Nop
12:	Nop
13:	Nop
14:	Nop
15:	Nop
16:	Nop
17:	Nop
18:	Link Resume

Following through the commands, r5 is not $4000, so we do not branch. We set r5 to 0. r1 is 1, so link to PGC 6. (That will be VTSM PGC 6 in the same title set).

So far we have the following values for registers which are non-zero:

R1 1

Remember that all registers are initially zero when execution begins. PGC 6 says:

#DVDAfterEdit Commands V1 #PreCommands from "Simple:Video Title Set Menus:Title Set 1 Menus:English (7 menus):VTSM PGC 6:" 1: Set r0 = r1 2: Set r1 = 0 3: Nop 4: Nop 5: Nop 6: Nop 7: Nop 8: Nop 9: Nop 10: Nop 11: Nop 12: if r0 == 1 then Link PGC 7

We test r1 by moving it to r0 first then clearing r1. Now all registers except r0 are zero. Remember that r0 is the scratch register, so we never need to remember it for very long. We link to PGC 7.

Notice that PGC 7 actually contains a program and a cell (it has video). If we preview it, we see the Title Menu. Its pre commands are:

#DVDAfterEdit Commands V1
#PreCommands  from "Simple:Video Title Set Menus:Title Set 1 Menus:English (7 menus):VTSM PGC 7 (1 program):"
1:	Nop
2:	Nop
3:	Nop
4:	Nop
5:	Nop
6:	Set r6 = $20
7:	Set r0 = r4
8:	if  r0 != 0 then GoTo Line 10
9:	Set r0 = 1
10:	Set r0 &= $3f
11:	Set r0 *= $400
12:	Nop
13:	Set r3 = 1
14:	Set Button r0
15:	Set r1 = 0

We first save a GetLastItem value in r6. Then we move r4 to r0, and see if it had anything in it. It didnt, so we load a value of 1.

We make sure that r0 has a value between 0 and 63. (It will actually be between 1 and 36 to be valid, but we dont check this). Then we multiply it by 1024, since the spec likes to put button numbers in the high part of the word. We set the button number into SPRM 8. We set r3 and clear r1. We now have:

R3	1

We have finished the pre commands with no obstacles (we didnt link out to anyplace else), so we display the title menu with button 1 selected.

Now let us look at the title menu itself. It has one program, one cell, and two nav packs. The button navigation is identical in the two nav packs, so lets not worry about the fact that there are two.

You will see that each of the first four buttons has a LinkTailPGC command. This will cause the post commands of the current PGC to be executed if the button is activated. The fifth button (the Play All) has a Nop, because it is not yet hooked to anything. We will hook it up later, but to a different PGC.

Let us now examine the VTS Menu post commands:

#PostCommands  from "Simple:Video Title Set Menus:Title Set 1 Menus:English (7 menus):VTSM PGC 7 (1 program):"
1:	Set r3 = 0
2:	Set r0 = Button
3:	Set r0 /= $400
4:	if  r0 != 1 then GoTo Line 8
5:	Set r3 = $101
6:	Jump VMG PGC 2
7:	Nop
8:	if  r0 != 2 then GoTo Line 12
9:	Set r3 = $102
10:	Jump VMG PGC 2
11:	Nop
12:	if  r0 != 3 then GoTo Line 16
13:	Set r3 = $103
14:	Jump VMG PGC 2
15:	Nop
16:	if  r0 != 4 then GoTo Line 20
17:	Set r3 = $104
18:	Jump VMG PGC 2
19:	Nop
20:	if  r0 != 5 then GoTo Line 24
21:	Set r3 = $101
22:	Jump VMG PGC 2
23:	Nop
24:	Nop

First we clear r3. Now all of the important registers are zero again. We fetch the button number out of the SPRM. (We convert it back to 1 thru 36 by dividing by 1024).

Now we have five sets of four commands which test for buttons one through five and jump to Video Manager PGC 2 with a value containing the button number in the low part of r3 and a one in the high byte of the word.

For button five it uses button number 1, which will jump to the first title for the play all.

Now let us look at VMG PGC 2:

#PreCommands  from "Simple:Manager Menus:English (8 menus):VMG PGC 2:"
1:	Set r1 = 0
2:	Set r2 = 0
3:	if  r3 & $ff00 then GoTo Line 5
4:	GoTo Line 8
5:	Set r5 = r3
6:	Set r5 /= $100
7:	Set r3 &= $ff
8:	if  r3 >= 5 then Link PGC 3
9:	Set r0 = 1
10:	 if  r0 == r3 then Jump TT 1
11:	Set r0 = 2
12:	 if  r0 == r3 then Jump TT 2
13:	Set r0 = 3
14:	 if  r0 == r3 then Jump TT 3
15:	Set r0 = 4
16:	 if  r0 == r3 then Jump TT 4
17:	Jump First Play

Remember if we get here we have a value of $101, $102, $103, or $104 in r3.

We test r3 to see if there is anything in the high order byte. There is, so we go to line 5. We take that value and move it to r5 and divide it by 256, resulting in r5 = 1 (the one that was in the high byte). We then and off the high byte and leave just the button number in r3.

Then we have a series of tests which result in going to the appropriate title for each button, TT 1 thru TT4. Since we know we came here with a valid button number, it can never take the Jump First Play branch.

Now let us look at the Video Manager in the left pane, and then expand the Title Play Map. We see that TT1 is VTS 1, the one and only chapter, TT2 is VTS 2, etc. etc.

Now let us look at a Title. Well start with TT1:

#PreCommands from "Simple:Video Title Sets:VTS 1:PGC 1 TT 1:"
1:	Nop
2:	Nop
3:	Nop
4:	Nop
5:	Nop
6:	Set r6 = $c080
7:	Set r7 = r6
8:	Set r0 = r5
9:	Set r5 = 0
10:	Set r1 = 0
11:	Set r2 = 0
12:	if  r0 == 1 then Break

We set the GetLastItem register, r6, with a unique value. We also move the same value to r7. Line 12 is pointless since all a Break accomplishes is to skip any commands that follow and get right to the video display. At this point we have:

R3	$101
R6	$c080
R7	$c080

We now play Track 1. The other three titles pre commands are identical TT1 except for the GetLastItem value.

There are no cell or button commands in the tracks, so when the track is finished it automatically goes to the PGCs post commands.

#PostCommands from "Simple:Video Title Sets:VTS 1:PGC 1 TT 1:"
1:	Set r4 = 0
2:	Set r1 = 1
3:	Call VMG PGC 4 resume C1

We now have the following register values:

R1	1
R3	$101
R6	$c080
R7	$c080

Lets see what PGC 4 says:

#PreCommands from "Simple:Manager Menus:English (8 menus):VMG PGC 4:"
1:	Set r5 = 0

2:	Set r2 = 0
3:	if  r1 >= 2 then GoTo Line 5
4:	Jump VTS 1 VTS TT 1 Menu Root
5:	Jump VTS 4 VTS TT 1 Menu Root
6:	Jump First Play

Since r1 == 1 it will jump to the root menu for VTS 1: (Weve seen this before!)

#PreCommands from "Simple:Video Title Set Menus:Title Set 1 Menus:English (7 menus):VTSM PGC 1:"
1:	if  r5 == $4000 then Link PGC 3
2:	Set r5 = 0
3:	if  r1 != 0 then Link PGC 6
4:	if  r2 != 0 then Link PGC 5
5:	Set r0 = VTS title
6:	Set r0 *= $100
7:	Set r0 |= Part title
8:	Nop
9:	Nop
10:	Nop
11:	Nop
12:	Nop
13:	Nop
14:	Nop
15:	Nop
16:	Nop
17:	Nop
18:	Link Resume

We can see that this will go to PGC 6, because r1 is not zero. Then PGC 6 will go to PGC 7, and r1 will be cleared.

Then PGC 7 will display the title menu again, highlighting button 1 because it is the default. (r4 is not set to anything).

If we look at the post commands for TT2, TT3, and TT4, they all set r4 to their own button number. Example for TT2:

#PostCommands from "Simple:Video Title Sets:VTS 2:PGC 1 TT 2:"
1:	Set r4 = 2
2:	Set r1 = 1
3:	Call VMG PGC 4 resume C1

So when navigation finally gets to the title menu, it will highlight the button which instigated the last track play.

Some Conclusions

It seems there is a lot of jumping back and forth between domains and PGCs. But the Video Manager and Video Title Set 1 domains are very close together, because there is no video in the Video Manager domain. The PGCs for a given Title Set are also close to each other. So the play head doesnt have to move very far on all these branches between PGCs in the menu domains and PGCs in the title domains.

However, since all DVDSP 2 scripts are placed in the Video Title Set 1 Menus, then any script checking what to do after playing a track must be jumped to from the track, and then it must jump back to the next track to be played. So any scripting we do in the track areas will be more efficient, and will execute more quickly if it can jump directly to the next track, if the DVD Spec commands allow it to do so. Certainly any scripting between markers (chapters) in the same VTS will go much more quickly.

I believe we have enough information to develop a play-all script directly in DVDAfterEdit.

Insert Commands for Play All

It turns out that to make the Play All button completely functional requires us to add 1 command to the title menu PGC, one command each to the title PGCs, and a single routing dummy PGC to the Video Manager Menus, with nine commands. It requires the use of one register.

VTSM PGC 7

In the last section of the post commands insert the following command at line 21:

#Selected  from "Simple:Video Title Set Menus:Title Set 1 Menus:English (7 menus):VTSM PGC 7 (1 program):"
21:	Set r8 = 1

This commands sets the variable that means we are in play all mode, instead of the normal play one track at a time mode.

VTS 1 PGC 1 TT 1

Insert the following command at line 3 of the post commands:

#Selected  from "Simple:Video Title Sets:VTS 1:PGC 1 TT 1:"
3:	 if  r8 == r1 then Call VMG PGC 9 resume C1

Insert this same command at line 3 of the post commands for each of the titles. (TT2, TT3, and TT4).

VMG PGC 9

Insert a dummy PGC in the Video Manager Menus. It will contain the following commands:

#Selected  from "Simple:Manager Menus:English (9 menus):VMG PGC 9:"
1:	Set r0 = 1
2:	 if  r4 <= r0 then Jump TT 2
3:	Set r0 = 2
4:	 if  r4 == r0 then Jump TT 3
5:	Set r0 = 3
6:	 if  r4 == r0 then Jump TT 4
7:	Set r8 = 0
8:	Set r4 = 5
9:	Link PGC 4

The first two commands check to see if we came from TT1, and if so jumps to TT2. The next four commands do similar logic for TT2 and TT3.

When we have finished TT4, the last track, we clear the play all variable (r8). Then we set the button number to 5 so that the title menu will highlight button 5 (the play all button) to indicate that is what we did last. Then it eases back into the abstraction layer at VMG PGC 4.

Pretty simple, huh?

Gain Access To DVD@CCESS, DVDAfterEdit Style

While finishing a complete re-authoring job the other day, I came to the realization that since the DVD's PGC structure was drastically changed, none of the eight(!) DVD@CCESS links would function. Oops! I procrastinated as long as possible and finally bit the bullet -- I had to figure out how to get these to things work. After some experimentation and testing, I was able to not only restore the DVD@ccess functionality, but completely reassign which PGC's triggered which URL's. This article will show you how to quickly regain control of DVD@CCESS -- the DVDAfterEdit way!

The DVD@CCESS data entries are stored in the VMG's "Text Data" area:

[inline:1=center,data entries stored]

Each link programmed in DVDSP has it's own line in DVDAfterEdit. When a DVD@CCESS-assigned PGC is played, it triggers the command, whether it's a file path, email address, or URL (please refer to the DVDSP manual for more information regarding these functions). Navigation must actually enter the PGC - moving past the Pre-Command area - in order for the command to execute. This is why DVDSP does not permit DVD@CCESS commands to be programmed for a button.

But with DVDAfterEdit, it's easy to make it seem like a button executes the command. Just duplicate the PGC with the desired button, and set the duplicate PGC as not only the button's target, but the DVD@CCESS trigger. Since the NavPacks in the duplicate PGC's are the same as the original, all of the button-commands will remain. To get everything programmed just right may require a bit more tweaking depending on the requirements of the DVD, but it's really that simple.

To program the PGC assignments in DVDAfterEdit, simply click on the field(s) shown in the image above. Content from these fields can be copied & pasted, but entirely new DVD@CCESS entries cannot be created. While this capability may appear in a future DVDAfterEdit update, in most cases the author would probably want to modify the original assets in order to inform the user of additional DVD@CCESS functionality. So how are these assignments derived?

All Bits Revealed!

[inline:2=center,bit definitions for text data]

Above are the bit definitions for the DVD@CCESS text data. Keep in mind that these definitions came about because of research and testing, not from any actual documentation - so the diagram may not be 100% accurate. Just like everything else we edit here, please remember to test thoroughly. Oh, and don't forget to include the DVD@CCESS .exe installer on the disc like the author who's DVD I just finished re-authoring! Otherwise this restored functionality won't work for a lot of potential users...

More Examples:

XESS000200020010060000021http://www.google.com = VTSM 2 PGC 6

XESS000200000010070000020http://www.tfdvd.com = VMG PGC 7

XESS000100000300010020039http://www.dvdafteredit.com/public/102.cfm = VTS 3 PGC 1 PTT 2

Some Notes:

1. The "version info" should probably be left alone to avoid accidentally offsetting the other bits. The "2" at bit 7 is written as a "1" with DVDSP 1.XX, and you may notice that the DVDSP 2/3 DVD@CCESS .exe installer is a different version than that of DVDSP 1.XX.
2. If bits 11 and/or 12 have assigned values, then it seems as though that bits 13 and 14 are irrelevant and should be set to "00." DVDSP sometimes puts values in all four of these bits, but if the trigger PGC is a VTSM, then the VTS number doesn't really mean anything - and vice-versa.
3. I believe bits 13 and 14 are for the VTS #, but if the TT # (title) and VTS # are different and problems persist, try the TT # instead.
4. If a VMG or VTSM is the trigger, a value of "1" will appear at bit 15. So for example, if a VMG PGC is the trigger, then bits 11 - 14 are set to "0000" and bit 15 is set to "1." Generally, if a VTSM is the trigger, bit 15 is still set to "1," which seems a little redundant.
5. If the command is set to trigger at a PGC and no PTT # is specified, bits 19 - 21 will be set to "000." If chapter 1 of a track in DVDSP (or PTT 1) is set as the trigger, bits 19 - 21 are set to "001," which should have the same functionality in most cases (all cases?) as if those bits were set to "000."
6. If a command is set to trigger at a PGC with bits 19 -21 set to "000," any related PTT's with DVD@CCESS commands (at chapter points) will not execute. In order for these following commands to execute, the PGC would need to have bits 19 - 21 set to "001" for chapter 1 (instead of "000" for the beginning of the PGC). Any PTT can execute a command as long as there is no other address associated with the parent PGC with bits 19 - 21 set to "000."
7. The PTT is the lowest level of the DVD logical structure I found to trigger a DVD@ccess command. Assigning PG #'s or Cell #'s to the "unknown" value at bits 22 and 23 does not seem to have any effect. My guess is that these bits are currently reserved.
8. Bits 24 and 25 represent the total number of characters for the command, up to a total of 64. If the command/address is in excess of 64 characters, the command will be truncated from right to left. Also, if these bits are set to a value lower than the number of required characters, then the URL, email address, or file path will be incomplete and will not function correctly.
9. Each possible DVD@CCESS address can only trigger a single command.

Layer Breaks on DVD+-R

Currently there is no way to preserve a desired layer break with programs such as Toast, Nero, or Record Now. This is because they write a disc from a ViDEO_TS folder, which has no layer break information in it. So they choose the layer break algorithmically, giving preference to a non-seamless cell.

This is even less-likely to follow the author's wishes if he or she chooses to make layer 0 larger than layer 1 for Outside Track Path (OTP), since dual-layer media have no such restriction. Also of course if the disc has lots of room there are likely to be more legal candidates for the layer break.

There is a school of thought that if there are multiple non-seamless cells, it may not matter which one is chosen. But I haven't heard this viewpoint from a DVD author, only from a programmer such as myself, so I can't comment on that. At least we can hope that the current popular programs choose a non-seamless cell. Early reports were that some programs chose layer-breaks arbitrarily anywhere in the video stream.

As much as I wish we could do it, currently the only program capable of writing a dual-layer DVD+-R while preserving the desired layer break, except the original authoring program itself where the layer break was chosen, is Gear Pro Mastering Edition. This requires some calculation to figure out the offset of the desired cell, and there is no visual confirmation of the layer break as in DVDAfterEdit Mastering Edition. However if you know where your desired cell is in the video, you can use DVDAfterEdit ME to display the sector number (it is shown in the cell information of every cell on the disc).

However there is still one area that can trip you up when writing from any program that is not the one that built the VIDEO_TS folder, except for DVDAE ME. That is the desire to put each .BUP file in a different ECC block than its corresponding .IFO file. Unfortunately there is no hard and fast rule for how to do this, so each authoring system is free to choose its own algorithm. This isn't normally a problem if the .VOB file(s) between the .IFO and .BUP are at least 16 sectors long, which almost any video is, but in spec authoring systems there is no rule that there has to be a .VOB file at all in the VMG. DVD Studio Pro puts at least a dummy video in every menu domain to avoid this problem. It is 116K, and contains 1/2 second of black.

DVDAE puts the .BUP file at the next multiple of 16 if it needs to. I have heard of that Toast just adds 16 to the sector number. (I haven't tested that claim). So your results are going to fail on some players if there is a different adjustment made by the original authoring system and the burner program. That is because there are pointers in the Title Map to where the video starts. Those pointers can be ignored by the player, or not, depending on how it implements things. DVDAfterEdit fixes them, but never uses them, for example, since they were only provided as crutches to early DVD player processors with extremely limited memory, and serve no useful purpose for how we keep track of the data.

Another theory that I have is that pointing to the wrong place in the video isn't always noticeable, since it takes so many sectors to display even half a second of video, and some players may be tolerant to starting in the midst of a GOP.

DVD Studio Pro puts two files in each VIDEO_TS folder when it builds it. When that folder is written to DVD-R or DLT, those files are automatically left out. So if you burn with Toast or another burning program, be sure to remove them first. Some players get confused by the extra files.

We have considered putting writing to DVD+-R on our to-do list, but we would be committing to support for lots of different DVD burners, and haven't justified the development and support cost of such a feature yet.

It would be nice if some enterprising burner program provided a way to set the layer break via a text file in the VIDEO_TS folder or something. Then we could arrange to write such a file.

Regards,

Larry

MyDVD Play All Example

Presented here is a Sonic MyDVD project that was authored in DVDAfterEdit to implement a Play All button.

MyDVD does a play all if you activate the first menu. Activating subsequent menus plays that menu and continues to the end. Not a bad solution. We will change it to behave like the Play All examples authored with other programs.

In MyDVD, which uses a motion menu with a button for each clip, very much like iDVD, it creates a separate VTS for each clip. The motion menu is placed in the first Video Title Set Menu. I presume if there are submenus they would be placed in the next VTS, etc.

MyDVD has an abstraction layer layout somewhat similar to DVDSP 2. Each title set menu has three dummy menus, a root menu, a chapter menu, and a non-entry menu. Except they are not quite dummies they have a single frame of black. The motion menu is assigned as a fourth, non-entry menu. If the motion menu is present, the frame of black in the dummy menus is replaced by a frame of black followed by the starting frame of the motion menu.

There are a considerable number of VMG dummy PGCs. They also have a single black frame.

Here are the commands:

First Play PGC

#DVDAfterEdit Commands V1
#PreCommands from "MyDVD Play All:First Play PGC:"
1:	Jump VMG PGC 9

VMG PGC 9

#DVDAfterEdit Commands V1
#PreCommands from "MyDVD Play All:Manager Menus:English (14 menus):VMG PGC 9 (1 program):"
1:	Set r15 = 1
2:	Jump VTS 1 VTS TT 1 Menu Root

Looking at the Video Manager Title Play Map, we see that the first title is VTS 1, as might be expected.

VTS 1 VTSM PGC 1 Menu Root

#DVDAfterEdit Commands V1
#PreCommands from "MyDVD Play All:Video Title Set Menus:Title Set 1 Menus:English (4 menus):
VTSM PGC 1 (1 program):"
1:	if  r15 >= 1 then Link PGC 3
2:	Set r15 = Title
3:	Set r15 &= 0
4:	Set r15 /= 1
5:	Set r15 = 0
6:	Link PGC 4

Since r15 == 1 we will link to VTSM 1 PGC 3

VTS 1 VTSM PGC 3 (non-entry)

#DVDAfterEdit Commands V1
#PreCommands from "MyDVD Play All:Video Title Set Menus:Title Set 1 Menus:English (4 menus):
VTSM PGC 3 (1 program):"
1:	if  r15 >= 3 then GoTo Line 7
2:	if  r15 >= 2 then GoTo Line 5
3:	Set r15 = 0
4:	Link PGC 4
5:	Set r15 = 0
6:	Link PGC 4
7:	if  r15 >= 4 then GoTo Line 10
8:	Set r15 = 0
9:	Link PGC 4
10:	Set r15 = 0
11:	Link PGC 4

Since r15 == 1, we will set it to zero and link to VTSM 1 PGC 4

VTS 1 VTSM PGC 4 (non-entry)

#DVDAfterEdit Commands V1
#CellCommands from "MyDVD Play All:Video Title Set Menus:Title Set 1 Menus:English (4 menus):
VTSM PGC 4 (1 program):"
1:	Link PGC 4

Since this is the motion menu, it just plays (there are no pre commands) and when it reaches the end of the cell it plays again.

We must look at each button command to see what happens next. (The button commands are in the Nav packs; if you dont remember how to get to them see the ReelDVD Play All Example for a screen shot).

Button 1

#DVDAfterEdit Commands V1
#Selected  from "MyDVD Play All:Video Title Set Menus:Title Set 1 Menus:English (4 menus):
VTSM PGC 4 (1 program):PG 1:Cell 1 (29 nav packs):Nav pack 2:"
1:	Jump VTS TT 1 PTT 1

Button 2

#DVDAfterEdit Commands V1
#Selected  from "MyDVD Play All:Video Title Set Menus:Title Set 1 Menus:English (4 menus):
VTSM PGC 4 (1 program):PG 1:Cell 1 (29 nav packs):Nav pack 2:"
2:	Jump VMG PGC 13

Button 3

#DVDAfterEdit Commands V1
#Selected  from "MyDVD Play All:Video Title Set Menus:Title Set 1 Menus:English (4 menus):
VTSM PGC 4 (1 program):PG 1:Cell 1 (29 nav packs):Nav pack 2:"
3:	Jump VMG PGC 12

Button 4

#DVDAfterEdit Commands V1
#Selected  from "MyDVD Play All:Video Title Set Menus:Title Set 1 Menus:English (4 menus):
VTSM PGC 4 (1 program):PG 1:Cell 1 (29 nav packs):Nav pack 2:"
4:	Jump VMG PGC 11

Button 5

#DVDAfterEdit Commands V1
#Selected  from "MyDVD Play All:Video Title Set Menus:Title Set 1 Menus:English (4 menus):
VTSM PGC 4 (1 program):PG 1:Cell 1 (29 nav packs):Nav pack 2:"
5:	Jump VMG PGC 10

The first button jumps directly to the Title, since it is in the same VTS. But all of the others must route themselves through a Video Manager PGC, because of the DVD Spec limitation that you may never navigate directly from one VTS to another.

By the way, that is why the ReelDVD project is so simple since everything is in a single VTS those restrictions dont apply!

VMG PGC 13

#DVDAfterEdit Commands V1
#PreCommands from "MyDVD Play All:Manager Menus:English (14 menus):VMG PGC 13 (1 program):"
1:	Set r15 = 1
2:	Jump VTS 2 VTS TT 1 Menu Root

VMG PGC 12

#DVDAfterEdit Commands V1
#PreCommands from "MyDVD Play All:Manager Menus:English (14 menus):VMG PGC 12 (1 program):"
1:	Set r15 = 1
2:	Jump VTS 3 VTS TT 1 Menu Root

VMG PGC 11

#DVDAfterEdit Commands V1
#PreCommands from "MyDVD Play All:Manager Menus:English (14 menus):VMG PGC 11 (1 program):"
1:	Set r15 = 1
2:	Jump VTS 4 VTS TT 1 Menu Root

VMG PGC 10

#DVDAfterEdit Commands V1
#PreCommands from "MyDVD Play All:Manager Menus:English (14 menus):VMG PGC 10 (1 program):"
1:	Set r15 = 1
2:	Jump VTS 5 VTS TT 1 Menu Root

Button 1 proceeded directly to VTS TT1. (r1 is still set to 1). Each of the other command sequences sets r15 = 1 and goes to the root menu of the desired track.

Each of the root menus is identical, here is one:

VTS 2 VTSM PGC 1 (root)

#DVDAfterEdit Commands V1
#PreCommands from "MyDVD Play All:Video Title Set Menus:Title Set 2 Menus:English (3 menus):
VTSM PGC 1 (1 program):"
1:	if  r15 >= 1 then Link PGC 3
2:	Set r15 = Title
3:	Set r15 &= 0
4:	Set r15 /= 1
5:	Set r15 = 0
6:	Jump VMG PGC 2

Since r15 == 1, it links to PGC 3. Each of the non-entry menus is identical.

VTS 2 VTSM PGC 3 (non-entry)

#DVDAfterEdit Commands V1
#PreCommands from "MyDVD Play All:Video Title Set Menus:Title Set 2 Menus:English (3 menus):
VTSM PGC 3 (1 program):"
1:	if  r15 >= 2 then GoTo Line 4
2:	Set r15 = 0
3:	Jump VTS TT 1 PTT 1
4:	Set r15 = 0
5:	Jump VTS TT 1

Since r15 == 1, it will Jump VTS TT 1 PTT 1. That means to the first PTT in that VTS. Jump VTS TT 1 would seem to have the same result. So, by round-about ways we eventually played each track we wanted for each button in the motion menu.

To see what happens after playing the track, we look at the post commands for each track:

VTS 1 PGC 1 TT 1

#DVDAfterEdit Commands V1
#PostCommands from "MyDVD Play All:Video Title Sets:VTS 1:PGC 1 TT 1:"
1:	Call VMG PGC 8 resume C1

VTS 2 PGC 1 TT 1

#DVDAfterEdit Commands V1
#PostCommands from "MyDVD Play All:Video Title Sets:VTS 2:PGC 1 TT 1:"
1:	Call VMG PGC 7 resume C1

VTS 3 PGC 1 TT 1

#DVDAfterEdit Commands V1
#PostCommands from "MyDVD Play All:Video Title Sets:VTS 1:PGC 1 TT 1:"
1:	Call VMG PGC 6 resume C1

VTS 4 PGC 1 TT 1

#DVDAfterEdit Commands V1
#PostCommands from "MyDVD Play All:Video Title Sets:VTS 1:PGC 1 TT 1:"
1:	Call VMG PGC 5 resume C1

VTS 5 PGC 1 TT 1

#DVDAfterEdit Commands V1
#PostCommands from "MyDVD Play All:Video Title Sets:VTS 1:PGC 1 TT 1:"
1:	Call VMG PGC 4 resume C1

So each track has an associated Video Manager PGC which is invoked after playing the track. Well take a look the first one.

#DVDAfterEdit Commands V1
#PreCommands from "MyDVD Play All:Manager Menus:English (14 menus):VMG PGC 8 (1 program):"
1:	Set r15 = 2
2:	Jump VTS 2 VTS TT 1 Menu Root

Each PGC 8 thru 4 unconditionally jumps to the next title. So now we know how to fix them. Just use another variable to mean play all and make the jumps conditional on that variable. Clear the play all variable when entering the title menu. Set it when invoked by the play all button.

I will leave the exercise to the reader.

ReelDVD Play All Example

Presented here is a ReelDVD project that was authored in DVDAfterEdit to implement a Play All button.

» Click here to download example files for this project.

In ReelDVD everything is placed into a single Video Title Set, even the menus. We created a title menu with four buttons to play each of the tracks, and a fifth unassigned button, labeled Play All. ReelDVD placed the title menu in PGC 1, the four clips in PGCs 2 through 5, and the play all button in PGC 6.

Here are the commands

First Play PGC

#DVDAfterEdit Commands V1
#PreCommands from "ReelDVDPlayAll:First Play PGC:"
1:	Jump TT 1

The first play jumps to the title menu.

VTS 1 PGC 1 TT 1 (Title Menu)

#DVDAfterEdit Commands V1
#PreCommands from "ReelDVDPlayAll:Video Title Sets:VTS 1 (6 program chains):PGC 1 TT 1:"
1:	if  r14 != 0 then GoTo Line 3
2:	Set r15 = Subpic lang
3:	Set r14 = 1
4:	Set r0 = 0

The first three lines are ReelDVD abstraction layer commands that for this project mean nothing. We have added line 4, which clears our Play All register flag each time we enter or reenter the title menu.

Each of the buttons in the Title Menu is already set up to play the correct track, except for the Play All button.

VTS 1 PGC 2 TT 1 (PTT 2)

#DVDAfterEdit Commands V1
#PostCommands from "ReelDVDPlayAll:Video Title Sets:VTS 1 (6 program chains):PGC 2 TT 1:"
1:	if  r0 == 1 then Link PTT 3
2:	Link PTT 1

After playing Track 1, the post commands are executed. If we are in Play All mode, we continue to Track 2. If not, we go back to the Title Menu.

VTS 1 PGC 3 TT 1 (PTT 3)

#DVDAfterEdit Commands V1
#PostCommands from "ReelDVDPlayAll:Video Title Sets:VTS 1 (6 program chains):PGC 3 TT 1:"
1:	if  r0 == 1 then Link PTT 4
2:	Link PTT 1

VTS 1 PGC 4 TT 1 (PTT 4)

#DVDAfterEdit Commands V1
#PostCommands from "ReelDVDPlayAll:Video Title Sets:VTS 1 (6 program chains):PGC 4 TT 1:"
1:	if  r0 == 1 then Link PTT 5
2:	Link PTT 1

Tracks 2 and 3 do the same thing as track 1, either continue or go back to the Title Menu.

VTS 1 PGC 5 TT 1 (PTT 5)

#DVDAfterEdit Commands V1
#PostCommands from "ReelDVDPlayAll:Video Title Sets:VTS 1 (6 program chains):PGC 5 TT 1:"
1:	Link PTT 1

The last track always goes back to the Title Menu.

VTS 1 PGC 6 TT 1 (PTT 6)

#DVDAfterEdit Commands V1
#PreCommands from "ReelDVDPlayAll:Video Title Sets:VTS 1 (6 program chains):PGC 6 TT 1:"
1:	Set r0 = 1
2:	Link PTT 2

The play all button sets the Play All register on and plays the first Track.

But how did the player get to the PGC Commands? It used the button commands in the Nav packs:

[inline:1=center,Nav pack button commands]

Notice that button 1 linked to PGC 2, which had no pre commands so it just played Track 1 and then went to the post commands, which we covered earlier.

So we set the button command for button 5 (the Play All button) to link to PGC 6. This will send it to the pre commands, which set the Play All register and then plays Track 1.

Highlighting the Correct Button

For some reason ReelDVD set the Force Selection button the button 1. Here we have cleared it, so it will remember which button was highlighted last when it gets back to the Title Menu.

[inline:2=center,highlight correct button]

Thats all, folks!

Replace VTS - Function and procedure

One of DVDAfterEdit's most powerful and frequently-used functions is the ability to replace a Video Title Set. This article describes briefly how to use it, while retaining all the exisiting navigation from your project. Common uses of this procedure would be to swap out a copyright message, company ident or even an updated element.

To get started, open up the build file of your project. DVDAfterEdit displays a representation of the information contained in the information (IFO) files of the DVD. You can see the Video Title Sets of your project by unfolding the arrow of the VTS node, in the Left Pane. Using Tracer or the Preview Window in the Right Pane, find the VTS you would like to Replace, unfold it's node arrow, and select the Title PGC (PGC_TT) node:

[inline:98-Video_Title_Sets.jpg=Video Title Sets]

The Right Pane is displaying all kinds of information about the VTS, but for the time being let's concentrate on the Pre-Commands. Unfold the arrow as shown above if you can't see them. These commands control the detailed navigation of the disc. Pre-Commands are executed before the video in the PGC is played, and Post-Commands are executed after it has been displayed. If you're a DVD Studio Pro user and have written "scripts" to control navigation or the selection of audio streams, for example, your commands will be here - although they may be difficult to find or recognise!

Don't worry - we don't need to understand these commands at all for this process - we just need to make sure we don't loose them when we Replace our VTS. We do that by making sure that the VTS TT_PGC node is selected as in the illustration above, and choosing "Copy PGC Commands" from the Edit menu. So all those commands are copied into the Paste Buffer, and will stay there until we've replaced the VTS with our new one containing the DTS audio stream. Then when the Replace function has finished, we can just paste them back in again.

[inline:98-select_replace_vts.jpg=Replace Video Title Set]

Try it, making sure the Project you're working on has been backed up first. Select the VTS node instead of the PGC_TT node, control-click on it and select "Replace VTS":

You'll get a requester like the one shown below. Browse your way to the VIDEO_TS folder of the project which contains your new VOB file, in this case the VTS_01_1.VOB:

[inline:98-select_VTS-VOB.jpg=select the VTS_01_1.VOB]

As you can see, DVDAfterEdit offers you the chance to Import any commands or menus associated with the VTS VOB you have chosen, but since we are taking the VTS from a project which has nothing to do with this one, we don't either of these options, so un-check both boxes, and click "Choose". This won't take too long, but for a larger VTS it will be some minutes. The program shows you a progress indicator.

[inline:98-progress_indicator.jpg=center,progress indicator]

Once the VTS has finished importing, select it's node arrow and unfold the arrow in the Right Pane to look at it's properties:

[inline:98-audio_stream_properties.jpg=center,access audio stream properties]

Bingo! We have a new VTS. We're not quite finished yet, though - if you unfold the VTS node arrow again and select the Title PGC again, you'll see that as expected, the VTS has no Pre or Post Commands - we chose not to import them, remember.

[inline:98-no_Pre_or_Post_Commands.jpg=center,no Pre or Post Commands ]

So now we simply have to select "Paste PGC Commands" from the Edit menu (while the title PGC is still selected), and the commands we copied to the Paste Buffer before starting the Replace VTS function will slot straight in. The navigation and/or scripting for the DVD will now behave exactly as it did originally, but with a new VTS where the dummy track was. All we need to do now is Save the project and we're done!

Summary

To recap, here is this procedure in outline:

1. Open the project in TFDVDEdit and find the VTS you want to Replace with the new VOB
2. Copy the PGC Commands of the current VTS Title PGC
3. Replace the VTS, choosing not to import it's commands or menus
4. Paste the old commands into the Title PGC of the new VTS
5. Save

At this stage it's also worth using DVDAfterEdit to check all the other properties of the new VOB - aspect ratio, subtitle & audio streams and their languages and so on, just to make sure that everything is as it should be.

If your original VTS had a more complicated structure than just one title PGC, you would copy the commands from the whole project rather than just the Title PGC, and use DVDAfterEdit's Title List editor to create the correct VTS PGC structure before pasting those commands back in. This is also quite straightforward, and is covered in other articles.

Conclusion

Hopefully you can now see that DVDAfterEdit's Replace VTS function is both extremely powerful and extremely easy to use. Any VTS can be replaced, so you could insert a new version with DTS audio, for example, or a VTS with animated subpictures (overlays), or one with complicated subtitle requirements - in fact, any feature not currently supported by your authoring application can be added, allowing you to keep creative control of the rest of the project, and pass the savings in time and efficiency on to your customers rather than letting the work go elsewhere. I'm sure someone out there will come up with some truly innovative uses for this function, and I look forward to seeing them!

Sharing GPRM registers between DVDAfterEdit and your authoring application

or "Messages From Beyond The Build File"

This article describes a technique using DVDAfterEdit which will enable you to make DVD Studio Pro ( or any other authoring application ) "talk" to DVDAfterEdit, after the disc has been built. It was written several years ago, before DVD Studio Pro offered the possibility to skip past motion-menu transitions. I developed the technique for my own use to do exactly that, and wrote this article illustrating the technique. It must have been a popular request, because six months later Apple added the feature to DVDSP !

So, the article is a little out of date, but the method is still a very powerful technique with all kinds of possible uses, allowing you to pass variables from inside the authoring application, down to spec-level commands in 'Edit, and back again. There is lots of information here for people who are new to the ideas of "spec commands", the "abstraction layer" and to DVDAfterEdit in general, so I hope you will still find what follows useful and interesting.

Introduction

As DVD Authoring applications become more and more sophisticated, offering more and more clever features in ever more easy-to-use ways, the line between "Pro" and "Non-Pro" authoring applications is becoming more and more blurred. Traditionally, the "Pro" apps allow nearly unlimited control of the DVD at it's lowest level, meaning the author can do almost anything the format allows. However this usually also means the author needs a detailed understanding of the specification itself, and this is often far from user-friendly.

At the other end of the scale, "abstraction layer" (AL) systems like DVD Maestro and DVDSP hide most of this detail from the user, and have a correspondingly shallower learning curve. However their capabilities are often somewhat limited as a result, since if the writers of the AL authoring app didn't specifically decide to make it easy for you, it may be very difficult, if not impossible, to do it at all!

DVDAfterEdit's great strength is in offering spec-level control to everyone, including users of these AL programs. Even, at one extreme, allowing us to "nuke" all the abstraction-layer commands, and build up the functionality of the DVD from scratch at the spec-command level.

If you're like me, though, this isn't always what you want. Here I'm going to introduce a new technique which bridges the gap between the two extremes of either spec-level detail or easier-to-use-but-more-restrictive AL techniques. So we can take advantage of the ease-of-use and speed of implementation of the AL authoring apps, and add the high-power DVD spec commands where necessary.

The basic idea is very simple. It makes use of the fact that the "variables" we use when creating "scripts" in an AL authoring application like DVDSP are actually GPRMs - "general parameters" - ie. memory locations where we can store numbers of our choice - for example, to remember the user's answers in a quiz, say.

In DVDAfterEdit they are referred to as "registers", numbered r0 to r15. Apple have used r0 to r7 for DVDSP's abstraction-layer, but the others are available for us to use in any way we like. Incidentally, for some reason, DVDSP2 allows us to use registers r8 to r15, but calls them GPRM 0 to 7. So, GPRM 0 is r8, GPRM 1 is r9, and so on. Other applications like Scenarist correctly call r0 GPRM 0, r1 GPRM 1 and so on.

The DVD-spec commands visible in DVDAfterEdit are of course just as capable of testing and setting these variables as the scripts in DVDSP. Knowing this, all we do is set a GPRM in DVDSP to a special "code" values of our choice - "1", say, for simplicity - build the project, test that GPRM in DVDAfterEdit, and depending on the result of the test, carry out another command. The variable is set in DVDSP's script, and then "passed" over to the spec-level commands in DVDAfterEdit. Which, in theory, could change that same GPRM, or any other, and pass it back to the abstraction-layer scripting again! But more of that later. Let's look at a specific example of this idea in use, which is probably the best way to understand it. I'll assume you're using DVDSP2, but the same principles can be applied to any AL-based authoring application.

1- Skipping Menu Transistions

What are menu transitions, and why should I use them?

One of the key elements of a high-end "Pro" DVD is the quality of design of the menus and interface, and one feature that never fails to impress is a slick introduction to the disc perhaps the main menu "builds up" from different pieces in a clever animated sequence, or the menu buttons "fly in" from different areas of the screen.

This kind of effect is achieved by having a short section of video just for the menu introduction, which is known as a "Menu Transition". Having these in key areas of the disc can make all the difference between a "so-so" presentation and a really pleasing design. However, implementing these kinds of features needs a little more time and effort than straightforward motion menus.

Lets say you've designed a main menu with simple overlays, and an introduction sequence, for example if your buttons "fly in" from somewhere off the screen as part of your menu transition, there are several factors which are important:

1. You don't want the button overlays visible from the very beginning, when the buttons are whizzing around, but only when the buttons have "settled in" to their final positions on-screen.
2. When users return to the Main Menu after watching one the features of the disc, they won't want to sit through the whole introduction sequence again that would quickly become irritating.
3. You want to be able to target specific buttons on each menu, depending on where the navigation has just come from. For example, the Bonus Features button should be highlighted if you've just come back from the Bonus Features menu.

Luckily, DVDSP2 allows us to solve Problem 1 using one of it's new features - menu Loop Points. Provided none of the buttons in a menu use any of DVDSP2's fancy new features (drop zones, shapes, text, assets), you can easily set a loop point in the General tab of the menu's Property Inspector. This has 2 functions - first, when the menu has played to the end, it will loop back to the loop point, not the beginning; and second, the buttons and their overlays only become visible once the loop point is reached, which is exactly what we want. When the menu intro has finished and the buttons have settled into their final positions, the overlays appear and the buttons become active, and when the menu reaches the end, it loops back to this point, rather than play the intro again (Incidentally, when you're designing a menu to work in this way, you'll want to make sure the last frame of the video matches the first frame of the loop point; so that when the loop happens, all the user sees is a brief pause. In the same way, it's best to have the audio fade down by the time the loop point is reached, otherwise when the menu loops it will "jump in" and spoil the slick effect).

So far so good - this is all something that DVDSP 1.5x couldn't do without using tracks as menus (See below). However, Problem 2 still stands. We don't necessarily want the menu's intro to play every time the menu is accessed, especially if it's the main intro to the whole disc. There are several ways this could be solved within DVDSP, but none of them are ideal. They are:

1. Duplicate the menus. So, the first time the disc plays, your "First Play" menu, with intro transition and loop point, plays. Then, later on, if people choose to access the main menu, instead of returning to the "First Play" menu, they are taken to another copy without the intro and loop point. This works well for simple projects, but can quickly get out of hand if you are designing menu transitions for more than a few menus. Say you have a main menu with 4 sub-menus. That's 4 copies of the menu with the transitions to those menus,plus 4 without - plus another 4 copies of the main menu including the transition back again. So that's 13 menus where otherwise there would only be 5! It's easy to see how this can be very complicated to author, and take up lots of valuable space on the DVD.
2. Have the transitions as separate menus, and only navigate to them when you want them. This avoids doubling up all the menus with and without transitions, but because there are no seamless joins between menus on DVDs, there will always be a noticeable pause between the end of the transition and the start of the menu. Keeping the transitions as menus, not tracks, minimizes this pause, incidentally.
3. Use track assets with buttons-on-video as menus. This is how it had to be done in DVDSP 1.5x. Briefly, the menu clip with transition is assigned to a track asset, not a menu. You add a marker at the point where you want the menu to loop, and add buttons to this marker, so they only appear when playback reaches that marker. Then when the track gets to it's end you can set it to loop straight back to the marker. This works well, but has an important limitation - Point 3 from above isn't possible. You can't target a specific button at the marker point. So whereas all the best-authored discs will return you to the button you just pressed when you're retracing your steps through a menu system, using this method the first button will always be highlighted.

These may seem like small problems, but it's the sum total of many small but significant points like this that make a truly excellent DVD design.

2 - Looking at motion menus in DVDAfterEdit

Firstly, it's worth looking at how DVDSP2 sets up looping menus. We'll use this information to skip the transitions using DVDAfterEdit.

When a menu is built, it becomes a PGC (Program Chain), just like almost everything else on a DVD. More specifically, it becomes a Video Title Set Menu PGC, or VTSM PGC.

Set up a test project in DVDSP2 with a looping menu, and build it somewhere, so we can take a look at this.

[inline:101_set_gprm7_dvde2.jpg=center,DVD Studio Pro project as seen in DVDAfterEdit]

If you open up the project's VIDEO_TS folder using DVDAfterEdit, and unfold the arrow for the VTSMs, you'll see the DVD's VTSM Title Sets. All 4:3 aspect menus are in VTSM #1 (in DVDSP projects for a 4:3 DVD). Unfold it's arrow and the one for "English" and you'll see all the 4:3 menus for your DVD, plus some "dummy" PGCs which are put there by the abstraction layer programming. You can use DVDAfterEdit's Preview feature to figure out which menu is the one you're interested in - it'll be one of the ones with an arrow next to it. If you unfold it's arrow, you'll notice it has 2 "cells", PG 1 and PG 2.

A cell is essentially a subdivision of a video stream. There are different types of cells - chapter markers are special kinds of cells used for navigation. If you unfold the arrows for any VTS (track) in your project, you'll see the Chapters (Parts of Titles, or PTTs) are all cells. Any marker set in DVDSP2 where you un-tick the chapter box in the property inspector will show up as a cell but not as a chapter. So cells don't have to be chapters; they have other useful properties - they can have Cell Commands attached to them, for example.

Anyway, a looping menu from DVDSP2 will have 2 cells, one at the start, and one at the exact point where you set up the loop point back in DVDSP. This is the one we're going to jump directly to later, in order to skip the menu's intro. If you unfold the arrows down to the nav-pack level, you can even see that the nav-packs in PG 1 don't have button commands, whereas those in PG 2 do (assuming you've made some!), because as we saw earlier, the buttons aren't active until the loop point (PG 2) is reached.

The other thing to notice at this stage is the menu's Pre-Commands. If you select the VTSM PGC of any menu in the left-hand pane of DVDAfterEdit, in the right pane you'll see a section marked Pre-Commands and Post-Commands. These are the DVD-spec level commands which are executed before (Pre) and after (Post) each PGC is played. This is where we're going to put the command to skip past the cell containing the menu's introduction.

So, now we can look at the nitty-gritty of the method.

3 - Skipping menu intros

As we saw in the introduction, the idea is that if we want menu intros to be skipped after accessing a certain part of the disc, we set a particular GRPM of our choice to a certain "code" value using a script in DVDSP 2. Then, after building the project, we use DVDAfterEdit to test the value of this GPRM in the menu's Pre-Commands.

If the GPRM we choose has it's special value, the script will cause navigation to jump straight to the second cell of the menu, skipping the one with the intro sequence in it. If the GRPM doesn't have the value you've chosen, the intro will play as usual. I've chosen to set GRPM 7 = 1 as my special code for "yes, I want the intro to be skipped", but you could use any GPRM and value you like, provided you remember what it is.

So, in our example, we have a main menu with quite a long intro sequence to the whole disc, with the buttons eventually flying in to their final positions, at which point (the second cell, where you set the loop point in DVDSP2) the overlays appear. If the user chooses to play the "Main Feature" from this menu, but then uses the menu remote key to get back to the main menu again, we don't want them to have to sit through the whole intro again.

Stage one is to set up a script which will set our "code" variable - GPRM 7 = 1, or whatever you've chosen. I suggest you have just one script, and set it up as the Pre-Script for any menu or tracks where you want the menu intro to be skipped after they've played.

[inline:101_dvdsp_prescript.jpg=center,Set GPRM command]

So in DVDSP2, create a new script, name it "Menu Intro Skip" or something similar, and add just one command: 1 mov GPRM 7, 1 - which just sets GPRM to 1.

[inline:101_dvdsp_project.jpg=center,DVD-Studio Pro Prescript]

Now if you select any track, you'll see in the General tab of the Property Inspector that you can choose a Pre-Script in the Playback Options section. And all you have to do is choose your new script in the drop-down box.

Now, whenever the track in question is played, the Pre-Script we've chosen will be executed before it starts, and GPRM 7 will be set to "1". Then when we test GPRM 7 in the menu's Pre-Commands in DVDAfterEdit, the commands we add will ensure that because GPRM 7 equals "1", the menu intro will be skipped. If the user chooses to play a track where you haven't got your "Menu Intro Skip" script setup as it's Pre-Script, GPRM 7 won't be set to "1", and no commands are added in DVDAfterEdit, and the intro won't get skipped.

And that's it - in DVDSP 2 at least. Currently, the project isn't going to work as we want, because we haven't set up the code in DVDAfterEdit, but the ground-work is done.

The next stage is to build your project. And then test the value of SPRM 7 after the build is complete, ie. after it would normally be finished, which is why this technique is like getting messages from "beyond the build file"! So, open your newly built project in DVDAfterEdit, and as we saw earlier, unfold the VTSM arrows (VTSM 1 for 4:3 menus in a 4:3 project, VTSM 2 for 16:9 menus if your project has both) to find the main menu. Don't worry about the abstraction layer's dummy PGCs, just click on the ones with arrows next to them & use the Preview window to find the right one. It's also useful to bear in mind that the menus will be arranged in DVDAfterEdit's Left Pane in the same order as they are in the Contents>Outline window in DVDSP 2.

As we saw before, you'll see two cells in the menu, the first containing the intro, the second containing the looping part. If you select the second cell, the Preview window will display the exact I-frame where you chose your loop-point to be.

All we have to do now is make sure you've selected the VTSM PGC for your menu, so you can see the Pre and Post-Commands (these won't show up if you've selected individual cells or nav-packs):

- and add, at the END of the menu's Pre-commands: if r15 == 1 then Link PG 2

To do this, first select the last Pre-command for the VTSM PGC, in this case #15, and press Apple-K. A new command,16: NOP will appear. Then type if r15 == 1 then Link PG 2 in the command assembler :

Set DVD command

[inline:101_set_gprm_command.jpg=center,Set GPRM 7 in TFDVDEdit-2]

And press Enter.

Remember that for some peculiar reason, what DVDSP2 chooses to call GPRM 7 is actually register number 15, or r15. So we set GPRM 7 in DVDSP2, but now we test r15. If it equals "1", then the command links to PG 2, the second cell in the menu, which only contains the looping part, and the user won't see the intro which is contained in cell 1, assuming you out your loop point in the right place - bingo. Our special code variable has been "passed" to DVDAfterEdit's spec commands from beyond the build file, allowing us to add a function Apple didn't include in DVDSP2. And all with only 2 lines of code!

(We add the command to the END of the Pre-Commands, to make sure that all the others are executed. They have been added by DVDSP's abstraction-layer programming, and if we skip to the next cell before they're been executed, things may not behave as they should.)

Now we can add exactly the same command to the Pre-Commands of any other menus whose intros we also don't want to be played (if r15 = 1) in exactly the same way. If there's a menu where you always want the intro to play, obviously just don't add the command. Finally, in the Post-Commands of this menu PGC, add a new NOP command to the beginning (Select where it says Post-commands, and press Apple-K) and edit it to say Set r15 = 0, Register.

This just keeps things tidy, clearing GPRM 7 so that if the user navigates to another menu, it's intro won't be skipped. (Unless we want it to, in which case we would use set our "Menu Intro Skip" script as a Pre-Script again.)

So, just to re-cap, the Pre-Command for the looping menu checks whether r15 (GPRM 7) is set to 1. If it is, the command links to the second Cell of the menu, skipping the intro. If it isn't the menu plays normally. Either way, r15 (GPRM 7) gets reset to "0" afterwards.

Now, when designing the project in DVDSP 2, all we need to do is choose our "Menu Intro Skip" script as the Pre-Script of any track or menu whenever we want subsequent menu intros to be skipped, and keep an eye out for other places where this value needs to be manually reset. For example, if the end of the track is reached without the user pressing the remote menu key, and navigation then jumps to an "Extras" Menu, which itself has an intro which is set up to be skipped in some cases, but in this case we want the intro to be played; then we should add a script to the end of the track in DVDSP 2, to reset GPRM 7 to "0".

All of which will take some planning for very large projects! But hopefully you will have clever ideas about how to improve the method. One possibility is to have different "code" values for different menus, so if GPRM 7 = 1, the Main Menu (but no other) skips it's intro, if it's set to 2, the Main Menu Intro plays normally but the Bonus Features Menu skips it's intro... you get the idea.

Conclusion

We've seen how DVDAfterEdit can share registers r8-r15 with DVDSP2, where they're known as GPRMs 0 to 7, allowing us to "pass" commands across from the abstraction layer to PGC Pre and Post-Commands. If a GPRM is set to a certain value in DVDSP2, then we can execute a DVD-spec command in DVDAfterEdit, enabling functionality which otherwise wouldn't be available to us.

In our example, that was skipping directly to a later cell in a looping motion menu, but there's no limit in theory to what these commands might be - how about inserting a new piece of footage into the middle of a menu sequence, by jumping directly from the middle of one menu to another, say?

Or, while typing this article for the site, it's occured to me that it may well be possible to solve the intro-skip problem in another way - make all our menus tracks, as in Method C back towards the beginning of this article, with scripts storing button selections in GPRMs, and then using Pre and Post-Commands in DVDAfterEdit to ensure the right buttons are selected, even with buttons-on-video in tracks... I'll get back to you if it looks useful.

The only limit is our ability to come up with new ideas. I'm looking forward to everyone else's ideas on how to expand this!

Good luck,

Ian

Simple DVD Spec. Re-Authoring With DVDAfterEdit, Part 1

[please note that this page has many images and may load slowly]

[inline:ben-intro.jpg=right,Ben Weinrach]

While working at NAB with the DVDAfterEdit gang, I spent a lot of time talking to DVD authors. Many of them were experienced Maestro and DVDSP2 users looking for a little more control over their projects.

When I showed them the programming their favorite authoring application was doing behind the scenes, many were surprised at the complexity - especially for very simple projects. They understood that they could re-author with DVDAfterEdit, stripping away the excess commands and dummy menus, but were not quite sure where to begin.

I was able to relate with them. I explained how after working with DVDSP 1.X for over a year, I suddenly found myself having to learn a very popular spec-based authoring system in a hurry. After a while, the programming syntax and workflow became clear, and actually rather easy - at least for the types of jobs I was authoring. The amount of programming efficiency and organization is truly up to the author, which directly translates into navigation speed. Fewer commands and less jumping in and out of domains means a faster experience for the end user as well as less searching around the disc for the DVD player. When recordable DVD formats are used for delivery, this becomes even more important.

This article is going to show you how unbelievably easy and effective re-authoring with DVDAfterEdit can be. I'll demonstrate how to delete unneeded PGC's and how to wipe out all navigation commands, whether they were input by the author or added by the abstraction-layer authoring application upon build. Then we'll add the minimum Pre, Post, and Button Commands required to get the disc functioning as desired. The resulting VIDEO_TS folder will have a fraction of the commands and PGC's found in the original build. Once you have a solid grasp of these techniques, you'll find that the complete re-authoring of small projects can take just minutes and your authoring application may be downgraded to just the role of a multiplexer!

Let's briefly review the basic DVD structure

PGC (Program Chain): The basic object or building block in DVD structure. PGC's can contain instructions and/or video and audio. Menus and tracks are PGC's, and "dummy PGC's" are usually menus used to hold commands without video and audio assets. Think of a PGC as a container.

VMG (Video Manager): The upper-most level or "domain" of DVD structure; it contains various attributes of a disc that can affect playback, as well as contain menu and dummy PGC's.

First Play PGC: This PGC informs the player how to start playing a disc. Commands can be used to set GPRM's, get information about the setup of the player, and direct navigation.

VTS (Video Title Set): Usually holds a disc's program material, and can be comprised of multiple PGC's. DVD's can have multiple VTS's, much like the tracks of an audio CD. The VTS domain is under that of the VMG.

VTSM (Video Title Set Menu): Each VTS has a dedicated menu area, its own VTSM domain, which can contain multiple menu PGC's. These menus can only control the VTS PGC's in the same VTS domain as the menu. So for example, VTSM 1 can control a track in VTS 1, but not in VTS 2.

The Project

The project we are going to re-author contains a 15 frame/1 GOP First Play in VTS 5, 4 short tracks in VTS's 1 - 4, and a single menu in VTSM 1.

» Click here to download "4 Track" example files for this project, including DVDSP 2 original build and the final DVDAfterEdit build.

Here is the left pane of the DVDSP 2 build:

[inline:44_left_pane_dvdsp2.jpg=center,left pane of the DVDSP 2 build]

DVDSP2 put 8 dummy menus in the VMG, the Main Menu in VTSM 1 (if you expand the arrows further, you will see this listed as "program" in DVDAfterEdit) with 6 additional dummy menus, and 5 dummy menus in each of the other VTS's respective menu domains.

Upon further inspection, you'll notice line after line of Pre-Commands in many of these dummy PGC's (see image below). These dummy PGC's and commands are generated "behind the scenes" upon project build.

Popular abstraction-layer authoring applications (like Maestro & DVDSP 2) make programming navigation easy for the author, but create all these commands and dummy PGCs which are not required by the DVD Specification to get the disc to operate as desired. All of this extra stuff makes DVD players have to work harder, by running through a lot of commands just to search for and jump to another PGC with a lot of commands, etc., until navigation ultimately lands where needed.

We are going to delete everything we don't need (and want), while maintaining the original PGC structure and the project's functionality.

[inline:44_maintain_structre_functionality.jpg=center,maintain the original PGC structure and the project's functionality]

Step 1: Delete Dummy PGC's

Open the arrows for the VMG and select all 8 PGC's. Delete them by control-clicking and selecting the "Delete PGC" command. Notice how DVDAfterEdit keeps 1 PGC, as there needs to be at least one whether it will be used or not.

[inline:44_one_pgc_maintained.jpg=center,one PGC kept]

Next, open the arrows for VTSM 1, and delete all of the dummy PGC's. Keep PGC 7 (the Main Menu), which will automatically change to PGC 1.

Finish this step by deleting all of the PGC's in the 4 remaining VTSM domains. Each VTSM will keep 1 dummy PGC, which we'll need. The left pane should now look like this:

[inline:44_left_pane_with_dummy_pgcs.jpg=center,left pane with dummy PCG's]

Step 2: Delete All Commands

Now we need to delete all remaining Pre, Post, and Button Commands because these are now irrelevant since we no longer have all of those dummy PGC's. We could have done this step first.

In the "Edit" menu, select Project-wide Edits/Delete All Commands In Project.

[inline:44_select_project_delete.jpg=center,select Project-wide Edits/Delete]

Step 3: Change Menu Type & Entry PGC Designations

These parameters define a Menu PGC's function in the grand scheme of the disc. By changing these values, we are actually hard-wiring our DVD controller's "menu" and "title" remote keys. Although abstraction-layer authoring applications allow us to assign these remote keys to whatever we want, this "hard-wiring" is actually part of the DVD Specification.

If a VTSM is designated as an "entry PGC" with a "menu type" of "root," then when the menu remote key is activated in its respective VTS, navigation will jump to this menu. DVDSP 2 makes this root menu a dummy, in order to use its Pre-Command area to send navigation on its way. We will be using both of these techniques, but with far fewer commands.

The same scenario also applies to the VMG - when the "title" remote key is activated while in a VTS (track), navigation is directed to the VMG PGC designated as the "entry PGC."

Select VMG PGC 1, and look at the "entry PGC" line in the right pane. Notice that it's grayed-out (therefore unavailable for editing) and is set to "yes."

[inline:44_entry_pgc_yes.jpg=center,entry PGC set to yes]

Now select VTSM PGC 1. Change "entry PGC" to "yes" and "Menu Type" to "root." Now that this is a "root menu" and an "entry PGC," activating the menu remote key while playing Titles in VTS 1 will automatically call this menu PGC, first looking in the Pre-Command area for any instructions when it gets there. Since this menu is our Main Menu (FYI, DVDSP 2 seems to put all 4:3 menus in VTSM 1), the track in VTS 1 has the closest physical link to the Main Menu than any other VTS. In other words, it never needs to leave the VTS 1 domain to get to the Main Menu, unlike the VTS's in this project.

[inline:44_change_main-type_to_root.jpg=center,change Menu Type to root]

Check the other VTSM's. Notice how they are already set to "yes" and "root." DVDAfterEdit did this for us when we deleted all of the dummy PGC's. Since this project only has one menu, these VTSM's will function as dummies - but more on that in just a bit.

Step 4: Pre-Commands & Post-Commands

Since we've deleted unwanted PGC's and commands as well set up our menu designations, it's time for the bulk of our work: adding our commands (but we'll save the button commands for the last step as not all of our targets exist quite yet). There is a basic rule to keep in mind when setting up a disc's programming: navigation cannot jump between Video Title Sets - it must first enter the Video Manager domain. Here is the desired layout for this DVD:

First Play= Jump to VTS 5, then jump to the Main Menu in VTS 1. The Main Menu has 4 buttons with targets of VTS 1, VTS 2, VTS 3, and VTS 4. At the end of each VTS, navigation jumps back to the Main Menu.

Begin by programming the First Play. In the left pane, select "First Play" and insert a Pre-Command. We want the DVD to play VTS 5, so enter "Jump TT 5" as the Pre-Command. The "jump" command is used when navigation needs to leave one domain for another.

[inline:44_insert_pre-command_jump1.jpg=center,insert Pre-Command Jump TT 5]

[inline:44_insert_pre-command_jump1.jpg=center,insert Pre-Command Jump TT 5]

Once VTS 5 finishes playing, we want navigation to jump to the Main Menu. But since our Main Menu is in VTSM 1 and navigation is about to leave VTS 5, there is really only one place it can go in order to get there - the VMG. Select the program in VTS 5, and insert the Post-Command "Call VMG PGC."

[inline:44_insert_jump_menu_root.jpg=center,insert Post-Command Call VMG PGC]

VMG PGC 1 is the entry PGC in the Video Manager Domain and all navigation will be routed to this PGC including "title" remote key activation. But we want our navigation to go to the Main Menu in VTS 1, so let's give VMG PGC 1 a Pre-Command.

Select VMG PGC 1 in the left pane, and ." Now navigation will jump to the Main Menu in VTS 1 whenever navigation enters the VMG.

[inline:44_insert_two_pre-commands.jpg=center,insert the Pre-Command Jump VTS 1 Menu Root]

So now we're at the Main Menu, but we need to tell the DVD player which button navigation originated from (i.e. the button highlight). Since there is only one menu, all we need to do for this disc is move the value from SPRM 8 (which is where the last highlighted button number is stored automatically by the player) to a GPRM, which is referenced by a command to set the button highlight. Basically, we need two Pre-Commands.

Select VTSM PGC 1 and insert two Pre-Commands. For Pre-Command 1, enter "Set R0 = SPRM 8 Button." This means that GPRM register 0 is to have the same value as that of SPRM 8 - or that the value of SPRM 8 is to be moved to GPRM 0. SPRM 8 is a system parameter register that keeps track of the last selected/activated button number. Notice how DVDAfterEdit's SPRM pull-down menu conveniently displays the function of each SPRM.

[inline:44_select_set-button-gprm.jpg=center,insert two Pre-Commands]

For Pre-Command 2, select "Set Button GPRM r0." This tells the player to set the button number from the value stored in GPRM register 0 - which is the highlighted button number that we got in Pre-Command 1.

[inline:44_insert_jump-vmg-pgc.jpg=center,select Set Button GPRM r0]

That's all we need here, so let's assign commands to the other VTSM's.

We know the menu "entry PGC" and "root" designations we checked in step 3 are good to go and the menu remote key of a VTS is hard-wired to its respective VTSM. So when the "menu" remote key is activated in a playing VTS, navigation goes to its VTSM and first looks for instructions in the Pre-Command area. We need to tell navigation to jump from the VTSM to VMG PGC 1.

Insert the following Pre-Command for VTSM 2, VTSM 3, and VTSM 4: "." Now the activation of the "menu" remote key from VTS's 2, 3, & 4 will jump to the Main Menu in VTS 1 via VMG PGC 1. Remember, the "title" remote key automatically calls VMG PGC 1, so we do not need any other commands for that to work. Also remember that if VTS 1 is playing and the "menu" remote key is activated, we do not need to jump to VMG PGC 1 to get to VTSM 1. In fact, we couldn't do that if we tried, because the first stop on the navigation path would be to VTMS 1 anyway!

[inline:44_assign_end_jumps.jpg=center,Jump VMG PGC 1]

Before we move onto the Button Commands we need to assign the end jumps for the short programs in VTS's 1 through 4. Select VTS 1 PGC 1, insert a Post-Command and set it to "Call VTS menu." Once VTS 1 finishes playing, this will send navigation to the Main Menu in VTSM 1.

[inline:44_insert_call-vmg-pgc.jpg=center,assign the end jumps]

In order for navigation to get back to VTSM 1 from VTS's 2, 3, and 4, remember that we need to jump to the VMG first. So insert a Post-Command for those VTS's and set it to "Call VMG PGC 1."

[inline:44_navpack1_buttons.jpg=center,insert Post-command to Call VMG PGC 1]

Step 5: Button Commands And A Few Dummy VMG PGC's

Last but not least, we need to assign the four buttons on the Main Menu that target VTS 1 - VTS 4. Currently, the button commands found in Nav Pack 1 in VTSM 1 PGC 1 should look like this:

[inline:44_select_button_command-1.jpg=center,button commands found in Nav Pack 1]

Click the arrow next to Button Command 1 and set it to "Jump VTS TT." Since there is only a single title in VTS 1, we don't have a choice as to which one we select.

[inline:44_select_button_command-2.jpg=center,select Button Command 1]

[inline:44_insert_pre-command_jump-tt2.jpg=center,select Button Command 1]

Now, in order to jump from the Main Menu in VTS 1 to the program in VTS 2, we need to create a dummy PGC in the VMG because navigation cannot jump from VTS to VTS directly. Select VMG PGC 1, and control-click "Add Dummy PGC." Then insert the Pre-Command "Jump TT 2" into this new PGC, VMG PGC 2.

[inline:44_assign_button_command2.jpg=center,insert the Pre-Command Jump TT 2]

Create Dummy PGC's for VTS 3 and VTS 4, with Pre-Commands Jump TT 3 and Jump TT 4 respectively. Now, back at Nav Pack 1 in VTSM 1, assign Button Command 2 to "Jump VMG PGC 2" and repeat. The Button Commands should now look like this:

[inline:44_insert_pre-command_jump2.jpg=center,assign Button Command 2 to Jump VMG PGC 2]

You're finished! No more "obstruction layer" slowing things down. Go ahead - open the original and final VIDEO_TS folders and compare. Better yet, use DVDAfterEdit's "copy all PGC commands as text" function, paste into a text editor, and do a line count for each VIDEO_TS! The disc is down to the bare minimum of commands - and if we were to move the Main Menu in VTSM 1 to the VMG, we wouldn't need any dummy VMG PGC's either.

We'll actually try something like that in Simple DVD Spec. Re-authoring With DVDAfterEdit, Part 2, where instead of a project with 4 tracks, we'll re-author a similar project that has a track with 4 chapters, and an additional scene selection menu. Navigation originating from the scene selection menu will actually return there - unlike most "Hollywood" DVD's. The project will also feature greater use of GPRM's, Pre-Commands, and Post-Commands.

( We have Ian to thank (or stone, possibly?) for contributing "obstruction layer"... )

Simple DVD Spec. Re-Authoring With DVDAfterEdit, Part 2

Welcome to Part 2! Although the content is very similar, the layout of this project is very different from that of the 4 track project in Part 1, mainly, we're adding a scene selection menu, which will require a little more programming. I'll show you how to use 2 GPRM's and a decent variety of Pre- and Post-Commands to get this project working properly, and also discuss some DVD player default behavior governed by the DVD Specification. Spec. authoring gives the author more choices of how to organize and program a disc, and what is presented here is only one of several possibilities.

One quick note: this article refers to basic operations, terminology, and techniques found in Simple DVD Spec. Re-Authoring With DVDAfterEdit, Part 1. My intention is to focus on the new stuff, so please review Part 1 for more detail on certain subjects like "Title" and "Menu" remote key assignments, for example.

The "4 Chapter" project contains a 15 frame/1 GOP First Play in VTS 2, a track with 4 chapters in VTS 1, the Main Menu in the VMG, and the Scene Selection Menu in VTSM 1. There are no dummy menus (with one inconsequential exception), but there are a lot more commands. Unlike most Hollywood DVD's I've seen, navigation originating from the Scene Selection Menu on this disc returns there, even if the "Menu" remote key is activated. Activation of the "Title" remote key always returns navigation to the Main Menu with the proper button highlighted.

I chose to put the Main Menu in the VMG as it is the top-most menu in this disc's structure, while the Scene Selection Menu remains in VTS 1. Placing menus in the VMG can make programming easier and speed-up navigation as projects grow in size and complexity. Although the Scene Selection Menu could also reside in the VMG, this example will show some techniques for moving navigation between the VMG, VTSM, and VTS domains.

The file called "4CHAP.zip" contains the before and after DVDAfterEdit builds, and can be found in the member download area.

Adjusting The Layout

Here's the left pane of the DVDSP 3 build:

[inline:45_left_pane_dvdsp3.jpg=center,left pane of the DVDSP 3 build]

The first thing we need to do is move the Main Menu in VTSM 1 PGC 7 to the VMG. Select "VMG Menus" in the left pane, and then in the File menu select the "Replace Menu Vob�Ķ" command.

[inline:45_select_replace-menu-vob.jpg=center,select the "Replace Menu Vob�Ķ" command]

Choose VTS_01_0.VOB in the 4CHAP_ORIGINAL VIDEO_TS folder. VTSM menus are always located in the VTS_XX_0.VOB file, and DVD Studio Pro 3 always places 4:3 menus in VTS 1. The "Import Commands With VOB" option doesn't affect this project, since we'll be deleting them anyway. A progress bar will appear at the top of the right pane. This will finish quickly due to the size of the VOB being imported.

The like this in the left pane:

[inline:45_vmg_menus_displayed.jpg=center,VMG Menus now displayed]

Let's delete the dummy PGC's we don't need - which is almost all of them! Delete every PGC in the VMG except VMG PGC 7 (Main Menu). Notice how VMG PGC 7 has been automatically changed to VMG PGC 1. Then set its "entry PGC" parameter to "yes" so this PGC becomes the target for the "Title" remote key. As a quick reminder, I've included the two pictures below from the "4 Track" project discussed in Part 1. Please review the articlefor more information regarding these assignments.

[inline:45_4-track_project1.jpg=center,4 Track project]

[inline:45_4-track_project2.jpg=center,4 Track project]

Next, delete every PGC in VTSM 1 except for VTSM 1 PGC 8 - this is the Scene Selection Menu. Be sure to change its "entry PGC" and "Menu Type" parameters to "yes" and "root," respectively, so this PGC becomes the target for the "Menu" remote key.

Now delete all of the PGC's in VTSM 2. This remaining PGC is where our only dummy menu resides. This dummy PGC doesn't really serve any purpose for this disc because VTS 2 is the target of the First Play and has all user operations disabled. It will never call or navigate to its VTS menu.

Finally, delete all commands in the project with my favorite DVDAfterEdit 3 command, "Delete All Commands In Project." The left pane should now look like this:

[inline:45_delete_all_commands.jpg=center,Delete All Commands In Project]

GPRM Definitions

Now that the project's layout is set, it's time to dive into the fun stuff. I'm using only 2 GPRM's for this disc and their definitions follow below. I'll go into greater detail when we look at the programming for each area of the disc.

r0 = Menu Status

This GPRM is used to keep track of which menu navigation is going to and coming from. It keeps track of from where VTS 1 was activated - whether from the Main Menu or the Scene Selection Menu. It also handles what happens when the Title and Menu remote keys are activated, so navigation gets directed to the correct location. It also assists with how button highlights are determined for the Main Menu. This will be clearer in just a bit.

r1 = Scene Selection Menu button highlight

This GPRM is used to define which button will be highlighted while on the Scene Selection Menu. More detail to come...

All Commands Revealed!

The picture below shows all of the PGC's in this project and their respective commands. Feel free to insert all of these commands at any time. Details about their functions follow, PGC by PGC.

[inline:45_all_commands.jpg=center,All commands]

First Play

I use the First Play Pre-Command area to set up all of the values needed to start the disc. This can also be accomplished in various Pre- or Post-Command areas prior to the Main Menu, depending on the project. Here are the Pre-Commands:

[inline:45_first_play_pre-commands.jpg=center,First Play Pre-Commands]

GPRM 0 is set to a value of 0, and then navigation to jumps to VTS 2. Notice that the "Set" command set is being used. If you click on the command pull-down menu, you'll see several "Set" commands, including "Set GPRM." Although we are setting a GPRM, the generic "Set" is more versatile, allowing us to set several things, including values from SPRM's - which we'll do shortly. Also - in this instance - it has a cleaner look. If "Set GPRM" were used, the First Play Pre-Commands would look like this:

[inline:45_set-gprm_first-play.jpg=center,First Play Pre-Commands with GPRM set]

VTS 2: 15 Frames/1 GOP

Since navigation arrives here after the First Play, we may as well follow it. I make it a habit to start my discs with a track, and if there isn't any content that needs to display before the main menu, I use this - a VTS with 15 frames (1 GOP) of video and audio.

The only command in this PGC is a Post-Command that "calls" VMG PGC 1, which directs navigation to the Main Menu.

VTSM 2: Dummy PGC

Might as well get this out of the way - again (just being thorough...). To recap., this PGC serves no purpose except to exist - though technically I don't think it even needs to do that. As of now, we cannot delete the VTSM without deleting the entire respective VTS - which we don't want to do. So "just in case," I've inserted the "Jump VMG PGC 1" command. Before we move onto the bulk of the commands in this project, let's take a look at VTS 1.

VTS 1: Track w/4 Chapters

VTS 1 is the main "show" on this disc, and has 4 chapters. These chapters are accessed from the Scene Selection Menu by using Jump VTS_PTT as a button command. VTS 1 has the following Post-Commands, but no Pre-Commands:

[inline:45_vts1_post-commands.jpg=center,VTS 1 with Post-Commands]

Line 1: If GPRM 0 is equal to a value of 1, then navigation goes to line 3, skipping the command in line 2.

Line 2: So if GPRM 0 is not equal to a value of 1, then navigation "Calls" (or jumps) to the Main Menu, which is VMG PGC 1.

Line 3: This line instructs navigation to jump to the VTSM of VTS 1, which is the Scene Selection Menu.

Setting up VTS 1 like this prevents any unnecessary domain and/or PGC jumping. Wherever navigation originated to get to this VTS, it immediately returns. Of course Pre-Commands could be inserted depending on what is required by the disc. But keep in mind that when a PTT (chapter) in a VTS (show) is being directly accessed via the Jump VTS_PTT command, navigation visits the Pre-Command area of the PGC before jumping to the chapter - so any commands there will execute. In fact, a lot of things happen before navigation gets to the chapter via Jump VTS_PTT, according to the DVD Specification:

1) Stop the current presentation.

2) Discard the RSM [Resume] Info (if it exists), Assign '0' to SPRM 9 to stop the Nav timer.

3) Set SPRM 1 and SPRM 2 [Audio Stream & Subpicture Stream]

4) Execute the command in the Pre-Command Area of the PGC in which the PTTN [Part of Title Number] is found.

5) Start the presentation of the PTT [Part of Title a.k.a. chapter], which is specified by the PTTN and VTS_TTN [Video Title Set Title Number] within the current VTS-space.

So in order for this disc to operate correctly as programmed, no Pre-Commands have been inserted in VTS 1.

VMG: Main Menu

Here are the Pre-Commands for the VMG:

[inline:45_vmg_pre-commands.jpg=center,Pre-Commands for the VMG]

Isolated in this way, these Pre-Commands may be a little tricky to understand since they work in relation to other commands in the project. I'll review them line by line, and you may find it helpful to look at the picture above that shows all of the commands in the project.

Line 1: If GPRM 0 is equal to a value of 0, then go to line 4. Remember that GPRM 0 is used to keep track of menu-related navigation. At the First Play, since GPRM 0 is set to the value of 0, navigation moves to line 4 - skipping the commands in lines 2 and 3 the first time through.

Line 2: So if GPRM 0 is not equal to a value of 0, navigation forces a value of 2048 into SPRM 8, in order to highlight button number 2.

Line 3: Once the button is set, navigation skips to line 5.

Line 4: This command sticks a value of 1024 into SPRM 8 in order to have button number 1 highlighted.

Line 5: GPRM 0 gets reset back to a value of 0, since navigation has arrived (and will currently stay) at the Main Menu. If navigation originated from the Main Menu (or the First Play), this value is already set to 0 - so nothing changes.

The "GoTo Line" commands set up a bunch of conditions, and are configured in such a way as to control exactly what happens when navigation enters the Main Menu. So for example, if the disc is started and the show is activated by button 1 on the Main Menu, GPRM 0 will stay equal to 0. When the show is finished playing, navigation will first execute the Post-Commands in VTS 1. If navigation is directed back to the VMG/Main Menu, it checks the first line, skips to line 4, sets button 1 to highlight, and finally resets GPRM 0 to 0 (which it already is). This may seem like quite a few steps just to get button 1 to highlight, but how many steps do abstraction layer authoring applications use? They send navigation all over the place, jumping from PGC to PGC and line after line of commands, slowing the responsiveness of the DVD. These Pre-Commands also function correctly if the Title and Menu remote keys are activated. Since the Title remote key is hard wired to VMG PGC 1, whenever it's activated navigation comes here first. If you look at the disc's layout picture above, there are Pre-Commands in VTSM 1 ( which VTS 1's Menu remote key is hard wired to ) that will redirect navigation to the Main Menu if that is where it originated. For more detail on how this works, please see Part 1.

The Button Commands are simple enough:

[inline:45_vmg_button_commands.jpg=center,VMG Button Commands]

Button 1's instruction jumps navigation to VTS 1, which has no Pre-Commands. Button 2's Link TailPGC instruction jumps navigation to the Post-Command area of VMG PGC 1 - the current PGC. Since a button can generally only have a single command, this is a great alternative to jumping to a dummy menu if more instructions are required. In this case, we need to change a GPRM value and set a button (force a new value into SPRM 8) before we jump to the Scene Selection Menu, our final target. The Link TailPGC command is part of the Link Sub-Ins (Link Sub-Instruction) command set. "Link" commands are often used to move navigation within a PGC, like to a different Cell. A common example is the use of Link TopC (Link Top Cell) to loop a motion menu.

Here are the Post-Commands for the VMG PGC 1, which in this project are only accessed from button 2 of the Main Menu:

[inline:45_vmg_post-commands.jpg=center,Post-Commands VMG]

GPRM 0 gets changed to a value of 1, the button number gets set to 1, and navigation leaves the Main Menu and jumps to VTSM 1, the Scene Selection Menu. I'm using the "Set Button" command to force the value of SPRM 8 to 1024, because the first time navigation arrives at the Scene Selection Menu, button 1 should be highlighted. If this command is not used, then button 2 will be highlighted because the last selected/activated button was button 2 on the Main Menu, which would make the value of SPRM 8 equal 2048. Later I will go into some detail concerning some DVD Specification rules that govern how DVD players determine which button to highlight in certain situations.

VTSM 1/Scene Selection Menu

These are the Pre-Commands for VTSM 1:

[inline:45_vtsm_pre-commands.jpg=center,Pre-Commands for VTSM]

Line 1: If GPRM 0 is equal to a value of 1, navigation skips to line 3. There is only one instance when navigation would not skip to line 3, but move down to line 2. Pop quiz: do you know when this would happen?

Answer: if VTS 1 was activated from the Main Menu (GPRM 0 == 0) and the menu remote key was activated during the show. If you are not clear on why this is, check Part 1 of this article series! : )

Line 2: Navigation not skipping to line 3 gets sent to the Main Menu.

Line 3: This command assigns the value of SPRM 8 to GPRM 1.

Line 4: The value in GPRM 1 assigns the button highlight.

Before I explain what is happening here, let's take a quick look at the Button Commands:

[inline:45_vtsm_button_commands.jpg=center, VTSM Button Commands]

Buttons 1 - 4 jump to their respective PTT's (Parts of Title - or chapters). Button 5 sends navigation to the Main Menu.

In order to get the correct button to highlight upon arrival (or return) to the Scene Selection Menu, I'm using GPRM 1 to set the button highlight from the value in SPRM 8. When navigation gets sent to the Scene Selection Menu from the Main Menu, button 1 is highlighted because a value of 1024 was forced into SPRM 8 upon leaving the Main Menu.

If chapter 3 is played by the activation of button 3, 3072 is immediately stored in SPRM 8. When the show finishes (or the menu remote key is activated) and navigation returns, the commands instruct GPRM 1 to grab the value of SPRM 8, and set the button highlight accordingly.

No VTSM 1 Post-Commands are necessary for this example project.

Do We Really Need All Of These Commands?

The majority of commands in this project are used to 1) highlight the desired button, and 2) select the menu that the button was activated from in the first place - no matter the cause (end of show, Title or Menu remote key activation, etc.). The DVD Specification has a few default rules DVD players are supposed to follow that apply when there is no forced button selection:

a) When Force Select Button is set, the value of Force Select Button is assigned to SPRM (8).

b) When Force Select Button is not set,

b-1) If the current value of SPRM (8) is equal to or less than the number of Buttons during the period, SPRM (8) is unchanged.

b-2) If the current value of SPRM (8) is greater than the number of Buttons during the period, the value of SPRM (8) is set to the largest BTNN.

Force Select Button is usually assigned in the authoring application. DVD Studio Pro 3 refers to this as "Default Button." The parameter can also be assigned with DVDAfterEdit, and can be found on the 2nd to last line of "Button Highlights" in the Nav packs.

[inline:45_force_select_button.jpg=center,Force Select button parameters]

The 4 Chapter project does not use any Force Select Buttons - the button highlights are assigned throughout the various Pre- & Post-Commands. To see how these rules work, first take a look at this modified version of the 4 Chapter disc:

[inline:45_mod_version_4-chapter.jpg=center,modified version of the 4 Chapter disc]

Notice how nearly all of the commands to control button highlights have been removed, with only three exceptions. A "Set Button 1" Pre-Command has been added to the First Play so the correct button highlights when the DVD starts (just for safety), a "Set Button 2" command remains in the VMG Pre-Command area, as well as a "Set Button 1" command in the VMG Post-Command area. Otherwise, the Pre-Commands are only used to direct navigation when the show finishes playing, or if the Title or Menu remote keys are activated. This version of the 4 Chapter project will behave just like the more elaborate previous version in DVDAfterEdit's 3's Tracer function, and in theory, all DVD players. Let's apply the above DVD Specification rules - here they are again:

a) When Force Select Button is set, the value of Force Select Button is assigned to SPRM (8).

b) When Force Select Button is not set,

b-1) If the current value of SPRM (8) is equal to or less than the number of Buttons during the period, SPRM (8) is unchanged.

b-2) If the current value of SPRM (8) is greater than the number of Buttons during the period, the value of SPRM (8) is set to the largest BTNN.

a) Doesn't apply. SPRM 8 keeps track of that last selected/activated button, and a Force Select Button replaces whatever value was previously in that register. Though this project does have three instances of a "Set Button" Command forcing the value of SPRM 8 to change, navigation always determines which button should be highlighted, not the Force Select Button parameters. If the Force Select Button parameters were set, the highlighted button number would never change for a given menu.

One quick thing - the first two VMG Pre-Commands are only there to ensure that button 2 is highlighted if the Title remote key is activated when navigation originates from the Scene Selection Menu. If they are removed that functionality is lost, but the Force Select Button rules will highlight the correct button automatically for all other situations. Here's how it works:

b-1) To play the show from the Main Menu, button 1 needs to be activated. When this happens, a value of 1024 is immediately stored in SPRM 8. When the show finishes playing, navigation returns to the Main Menu, and sees that it has two buttons. Since the number of buttons hasn't changed, SPRM 8 is unaffected, and the DVD player highlights button 1 by referencing the value of SPRM 8.

To navigate to the Scene Selection Menu, button 2 on the Main Menu needs to be activated. When this happens, a value of 2048 is immedately stored on SPRM 8. Before navigation leaves the Main menu, however, it's instructed to change SPRM 8 to 1024, because button 1 should be highlighted upon arrival. What happens if the value of SPRM 8 isn't changed? Button 2 would be highlighted on the Scene Selection Menu upon arrival, because the DVD player would find a value of 2048 in SPRM 8. Since the Main Menu has only two buttons as compared to the five buttons on the Scene Selection Menu, the value of SPRM 8 will always be less than the maximum value of SPRM 8 that the Scene Selection Menu can accommodate (5120 is the value for button #5). So in this instance, SPRM 8 will not be affected (remember, by player default), according to rule b-1, because the Main Menu's maximum SPRM 8 value is only 2048.

Another example of how b-1 works would be if button 4 (Chapter 4) were activated on the Scene Selection Menu. Navigation would play chapter 4 then return. Since the number of buttons hasn't changed, SPRM 8 would not be affected, and button 4 would be highlighted. Now, rule b-2...

b-2) To navigate from the Scene Selection Menu to the Main Menu, button 5 needs to be activated - which will make the value of SPRM 8, 5120. When navigation reaches the Main menu, 5120 cannot be directly accommodated, as there are only two buttons. According to rule b-2, the highest button number will be highlighted - in this case button 2.

So, are all these commands that control the highlighted button numbers really necessary? Just a little while ago, I mentioned that this modified 4 Chapter disc will behave in DVD players the same way as the slightly more elaborate version - in theory. The truth is, not all DVD players are created equal - hence the ongoing issue that even replicated DVD's that are supposedly 110% perfect may not be compatible with every DVD player ever made - let alone all of the other DVD's floating around out there. For the sake of compatibility, and the fact that as DVD authors, we need to control how a disc functions as opposed to the player, these commands are... well... recommended. They don't allow the DVD player to make any decisions - it will just follow instructions - something players usually do well. As long as the instructions are good, everything should work as expected.... in theory!

Conclusion

I hope you have found these first two articles helpful, and I hope they inspire you to spec. re-author your discs. The more I re-author in DVDAfterEdit, the more necessary I believe it is. Just recently, a client of mine even noticed the difference. I updated his DVD with some new content, and then re-authored the project, eliminating all of the "obstruction layer" commands and PGC's. He commented that the disc is much more responsive than before, even in his old PowerBook - which often has problems with all kinds of DVD's.

These techniques are expanded further in Simple DVD Spec. Re-Authoring With DVDAfterEdit, Part 3, where I will show how to add a Scene Selection menu that "knows" which chapter has just been played; using composite commands and a different way of tracking button highlights.

Simple DVD Spec. Re-Authoring With DVDAfterEdit, Part 3

(Editors note: Just so you know, it is best to start with Part 1 and Part II of this series before beginning this Part 3 installment)

Adding a Second Scene Selection Menu and "Composite Commands"

Ready for some more spec. re-authoring fun? Great! The project discussed in this article is similar to the previous project, but with two significant differences. While the "show" still has four chapters and the structure is basically the same, there is now a second scene selection menu. In addition, the button highlight upon return to the scene selection menus is not handled by the last activated button like before, but is determined by the last chapter/PTT that played. This project also introduces "Composite Commands," which are used here to set a GPRM and link to another PGC, all within a single command line. Composite Commands can be extremely handy when used with buttons, since buttons can only have one command.

Using the last PTT to determine the button highlight is not very common, but some (if not all) of the more recent releases by the Criterion Collection use this technique. Though possibly a little disorienting at first, I think it makes a lot of sense, depending on the content. Once a chapter is activated from a scene selection menu, the show plays as usual. Whether the user allows the show to play through to another chapter or skips a chapter with the remote (backwards or forwards), the button that corresponds to the current playing chapter is highlighted upon return by the activation of the remote menu key. Note that if this button is on a different scene selection menu from the button that activated the show originally, the DVD player will display the correct menu! So the disc is not telling us where we started, but where we ended - or what we were just watching. This is exactly how the demo project presented here functions, though on a much smaller scale than a feature length movie with more than 20 or so chapters.

This article refers to basic operations, terminology, and techniques found in Simple DVD Spec. Re-Authoring With DVDAfterEdit, Parts 1 & 2. My intention is to focus on the new stuff, so please review the previous articles for more detail on certain subjects like "Title" and "Menu" remote key assignments, for example.

The "2 Scene Select PTT" project contains a 15 frame/1 GOP First Play in VTS 2, a track with 4 chapters in VTS 1, the Main Menu in the VMG, and Scene Selection Menus in VTSM 1 PGC 1 and VTSM 1 PGC 2. There are no dummy menus (still with one inconsequential exception).

» Click here to download before and after DVDAfterEdit build files for this "2 Scene" example project. Note that the original build is not fully programmed and will not play correctly, if at all.

Please note that as of this writing, this new demo project will not simulate 100% correctly with Tracer, as the use SPRM 7 has not been fully integrated yet.

Adjusting The Layout

Here's the left pane of the finished structure:

[inline:46_finished_left_pane.jpg=center,left pane of the finished structure]

The first thing we need to do is move the Main Menu (VTSM 1 PGC 7) to the VMG - same as before. Once imported with the "Replace Menu Vob" command, delete all of the PGC's except for PGC 7. Be sure to double check that the Main Menu PGC's "entry PGC" parameter is set to "yes," in order for the remote title key to function.

Next, delete every PGC in VTSM 1 except for PGC 8 and PGC 9 - these are the Scene Selection Menus. Again, check the newly renamed PGC 1 (which is the menu for Scenes 1-2) to make sure its "entry PGC" and "Menu Type" parameters are set to "yes" and "root," respectively, in order for this PGC to become the target for the "Menu" remote key.

Now delete all of the PGC's in VTSM 2. This remaining PGC is our only dummy menu.

And to finish the structure use my favorite step, "Delete All Commands In Project."

GPRM Definitions

Now that the project's layout is set, it's time to re-author. I'm using only 2 GPRM's for this disc and their definitions follow below. I'll go into greater detail when we look at the programming for each area of the disc.

r0 = Menu Status

This GPRM is used to keep track of which menu navigation is going to and coming from. It keeps track of from where VTS 1 was activated - whether from the Main Menu or either of the Scene Selection Menus. It also handles what happens when the title and menu remote keys are activated, so navigation gets directed to the correct location. It also assists with how button highlights are determined for the Main Menu.

r1 = Ultimately determines the button highlight for the Scene Selection Menus

This GPRM is used to define which button will be highlighted while on the Scene Selection Menus, but is a little more complicated than before. There are more possible values for r1 this time around because... well, I'll get to that shortly!

All Commands Revealed!

The picture below shows all of the PGC's in this project and their respective commands. Go ahead and insert all of these commands now. Details follow for only the PGC's that are different from those in Part 2.

[inline:46_all_commands.jpg=center,All PGC's in this project]

First Play

This is exactly the same as in Part 2...

VTS 2: 15 Frames/1 GOP

This is also exactly the same as in Part 2...

VTSM 2: Dummy PGC

Same as Part 2...

VTS 1: Track With 4 Chapters

Not quite the same as Part 2 - finally!

[inline:46_vts1_track_4chapters.jpg=center,VTS 1: Track With 4 Chapters]

Line 1: If GPRM 0 is equal to a value of 1, then navigation goes to line 3, skipping the command in line 2.

Line 2: So if GPRM 0 is not equal to a value of 1, then navigation Calls VMG PGC 1, which is the Main Menu.

Line 3: This sets GPRM 1 to a value of 5, setting a value for "end of show" status, which will be explained later.

Line 4: This line instructs navigation to jump to the root-designated VTSM of VTS 1, which is the Scenes 1-2 Selection Menu.

VMG: Main Menu

Surprise! These are the same Pre-Commands and Button Commands as before, but the post-Commands are slightly different:

[inline:46_vmg_main_menu.jpg=center, VMG Main Menu]

Line 1: GPRM 0 gets set to a value of 1.

Line 2: GPRM 1 gets set to a value of 0.

Line 3: Navigation jumps to the root menu of VTS 1, which in this disc is VTSM 1 PGC 1.

VTSM 1 PGC 1: Scenes 1-2 Selection Menu

Here are the Pre-Commands for VTSM 1 PGC 1 - all lucky thirteen lines worth. This gauntlet isn't too scary...

[inline:46_vtsm1_pre-commands_13lines.jpg=Pre-Commands for VTSM 1 PGC 1]

Line 1: If GPRM 0 is equal to a value of 1, navigation skips to line 3.

Line 2: If GPRM 0 is not equal to a value of 1, then navigation jumps to the Main Menu/VMG.

Line 3: If GPRM 1 is not equal to a value of 0, then navigation skips down to line 6.

Line 4: If GPRM 1 is equal to a value of 0, then it is set to a value of 1024 in order for button 1 to highlight.

Line 5: After GPRM 1 is set to 1024, navigation is instructed to skip down to line 13.

Line 6: If GPRM 1 is not equal to a value of 5, then navigation skips to line 9.

Line 7: If GPRM 1 is equal to a value of 5, then it is set to a value of 4.

Line 8: Once GPRM 1 is set to a value of 4, navigation jumps down to line 11.

Line 9: This sets GPRM 1 to the value stored in SPRM 7, which is the last PTT or chapter that played.

Line 10: If the value of GPRM 1 is less than 3, then navigation skips to line 12.

Line 11: If the value of GPRM 1 is equal to 3 or greater (i.e. 4), then navigation links to VTSM 1 PGC 2, which is the Scenes 3-4 Selection Menu.

Line 12: This command multiplies the value of GPRM 1 by 1024, in order to get the correct button to highlight. Notice in the pulldown menu for *= the other possible operations available.

[inline:46_command_button_hilite.jpg=command to get correct button to highlight]

Line 13: This sets the button to highlight from the value stored in GPRM 1.

There are some interesting things going on here. Here's how it works:

Scenario 1: The Show in VTS 1 is played by the activation of the "Play Movie" button on the Main Menu. If the user activates the menu remote key during playback, navigation will target VTSM 1 PGC 1 because it is the root menu of VTS 1. Since the value of the Main Menu is 0 (r0 == 0), navigation will immediately exit this PGC and jump to the Main Menu.

Scenario 2: The "Scene Selection" button on the Main Menu is activated. GPRM 0 is set to 1 because navigation is going to the Scenes 1-2 Selection Menu. GPRM 1 is set to a value of 0, in order to indicate that navigation will be entering the Scenes 1-2 Selection Menu from another menu. Once at the Pre-Command area for the Scenes 1-2 Selection menu, navigation will skip down to command line 3 because r0 = = 1. Since r1 = = 0 at this point, the value of r1 is changed to 1024. Button #1 is then set to highlight at line 13.

Scenario 3: The show is played via activation of button # 1(Chapter 1), located on the Scenes 1-2 Selection Menu. Before reaching PTT 2/Chapter 2, the menu remote key is activated. Navigation returns to the root menu of VTS 1, checks the first Pre-Command, and skips down to line 3. Since the value stored in r1 is currently 1024, navigation skips down to line 6. Obviously 1024 is not equal to 5, so navigation skips down to line 9. Here, the value of r1 is change to the value stored in SPRM 7, which is 1, for PTT 1/Chapter 1. At the next line, navigation checks if the value of r1 is less than 3, which it is. This determines which Scene Selection Menu is the final destination. The value of r1 is then multiplied by 1024, in order to get a legal button number value. Button 1 finally is set to highlight.

Scenario 4: The show is played via activation of button # 1(Chapter 1), and the menu remote key is activated between Chapters 2 and 3. Everything works just like Scenario 3, except at line 9, the value stored in SPRM 7 is now 2. Since 2 is less than 3, navigation remains in this PGC, and button 2 is set to highlight because r1 is now equal to 2048.

Scenario 5: The show is played via the activation of either button 1 or 2 on the Scenes 1-2 Selection Menu, and the menu remote key is activated between Chapters 3 and 4. Once back at line 9, r1 gets changed to a value of 3 (for PTT 3). Since 3 is not less than 3, line 11 executes and navigation links to PGC 2 - which is the Scenes 3-4 Selection Menu.

Scenario 6: The show is played via the activation of any Scene Selection Menu button, and plays until its end. In VTS 1's Post-Command area, navigation skips to line 3 because r0 = =1. At line 3, r1 is set to a value of 5, and then navigation jumps to the Pre-Command area of VTSM 1 PGC 1. Navigation gets to line 6, and since 5 = 5, r1 is then set to a value of 4. Navigation then skips down to line 11, where it links to VTSM 1 PGC 2.

Although Chapter 4 should be the last PTT that played in Scenario 6, I'm using the "end of show" value of 5 in r1 as a safety net in case the DVD player gets any ideas about changing the value of SPRM 7 after navigation leaves VTS 1. This way there are instructions for the DVD player to follow for every possible navigation scenario.

Unlike the project in Part 2, the chapter selection buttons have no relation to what button gets highlighted upon return. The user could also skip chapters while playing the show - forwards or backwards - activate the menu remote key, and the Per-Commands take care of the rest!

Here are the Button Commands for VTSM 1 PGC 1:

[inline:46_button_commands_vtsm1.jpg=center,Button Commands for VTSM 1 PGC 1]

Buttons 1 and 2 (for Chapters 1 and 2, respectively), target the corresponding PTT, just like the previous project. Button 3, which targets the Scenes 3-4 Selection Menu, is using what's called a "Composite Command." GPRM 1 is set to a value of 3, and the "link" option is enable in order to link to PGC 2. Two instructions, one command line! They're great for use with buttons, since buttons can only have a single command line. The "link" option allows for jumping - or linking - to PGC's within the same domain, PG's and Cells within the PGC, and the other DVD Spec. legal operations shown in the pulldown. Lastly, Button 4 jumps to the Main Menu.

[inline:46_link_option.jpg=link options]

[inline:46_link_to_pgc.jpg=link to PGC's]

VTSM 1 PGC 2: Scenes 3-4 Selection Menu

Here are the Pre-Commands:

[inline:46_vtsm1_pre-commands.jpg=VTSM 1 PGC 2 Pre-commands]

Line 1: If GPRM 1 is not equal to a value of 4, navigation skips to line 4.
Line 2: If GPRM 1 is equal to a value of 4, then GPRM 1 is set to a value of 2048, in order to highlight button 2.
Line 3: Once the GPRM is set in line 2, navigation skips to line 5.
Line 4: Target of line 1 - GPRM 1 is set to a value of 1024.
Line 5: Button highlight is determined by the value stored in GPRM 1.

Remember that a menu remote key activation during playback of VTS 1 cannot target this menu directly, as it is not designated as root. That being the case, fewer Pre-Commands are needed here because the PTT value has already been determined by the time navigation enters this PGC. Another thing to keep in mind is that while the PTT values for the chapters on this menu are 3 and 4, the buttons to be highlighted are 1 and 2. If the value of r1 were changed to 3072 or 4096 prior to entering this menu (by pre-Command line 12 in VTSM 1 PGC 1), these values would need to be changed again to get the correct button to highlight once navigation reached Pre-Command line 5. An alternative might be to use "Set Button" commands targeting specific buttons instead of referring to a GPRM, but this may not reduce the total number of command lines.

Here are the Button Commands:

[inline:46_vtsm1_button_commands.jpg=VTSM 1 Button Commands]

They are very similar to those of VTSM 1 PGC 1. Buttons 1 and 2 target PTT's 3 and 4 respectively, and a Composite Command is used for Button 3. This time r1 is set to 0, which is the same state as if navigation originated from the Main Menu via the activation of the Scene Selection button. Again, Button 4 jumps to the Main Menu.

Conclusion

Though not very common, this highlight via PTT technique may prove useful for various navigational needs. Hopefully, it has also shown how other SPRM's can be used to assist in determining the highlighted button number, besides that mundane SPRM 8...

Spec. Authoring Menu Transitions & A Multi Stream VTS

The Quick and Dirty Guide to Pilates, an enhanced 24-clip Playlist DVD

"The Quick and Dirty Guide to Pilates" is an exercise DVD that was created in DVD Studio Pro and then programmed with DVDAfterEdit. It was shot in 24p and compressed with BitVice. It is an exercise video that was shot from 3 angles, and allows the viewer to choose their own set of exercises, up to as many as 24 and in any order, for each exercise session. It includes a home menu, a design menu, an exercise menu, a web link menu, two alert menus, and a comprehensive set of setup menus.

The main "movie" track plays seamlessly from the home or exercise menu, and includes a startup logo and warning, introductory credits, up to 24 individual chapters, and final credits. There is also a contextual explanatory track that is invoked by buttons on video, an overall introductory track, and a contextual help track. The DVD is available for purchase at Amazon.com and through other retail distributors. A free copy will be sent to members on request. (See Recent News).

Included in the DVD ROM section is a demo version of DVDAfterEdit which allows you to trace through the navigation of the DVD to see how the playlist works. To run this demo requires a Macintosh. Inclusion of the demo on the DVD is by arrangement with Debdoot Das, the producer and director of the "Quick and Dirty Guide to" series of DVD's, of which there are more to come.

Digifilm (Debdoot's company) and I are currently working on a template project that will be available for download to Mastering Edition owners. This project will mimic the structure of the actual DVD exactly, but will have much smaller, "stand-in" assets for the tracks. It will use the menus from the actual DVD.

This template project should satisfy the needs of many exercise, concert, instructional, and corporate DVD's that can be poured into the mold of this template. Doing so completely relieves the author from all programming of the DVD, as it is already done for you. Just replace the assets with your own, and follow the short instructional video that will walk you through the process, with screenshots every step of the way. All of the navigation commands for the entire DVD are pasted in from a single text file in one step.

This brief description will be expanded as the project is completed.

Tips For DVD Studio Pro Authors

Tracer Tutorial, Part 1

This tutorial is an introduction to the Tracer interface and its basic functionality. The sample DVD project demonstrated here is that from the article "Simple DVD Spec. Re-Authoring with DVDAfterEdit 3, Part 3" by Ben Weinrach and is available in the download area. Please refer to the Tracer User Manual for more detailed information regarding the relevant topics discussed below.

When you pop a DVD into your player you are usually presented with a Copyright warning, some introductory logos, and then a main menu from which you can choose a few options. When you make choices, you are "navigating" through the DVD, and the DVD is navigating through various commands - just like a computer program. Navigating can be quite simple, or in the case of a trivia or other game, quite complex.

DVD Authoring applications give you various levels of control over the programming of this navigation, from very simple ones with fixed choices, to much more capable applications with complex "behind the scenes" abstraction layers, all the way to the most complex "Spec. Level" programs that provide access to all or most of the complete DVD Specification. None of these applications gives anything approaching the level of debugging control that is taken for granted by software engineers working in C++, Pascal, or even Basic. This can make it difficult for a DVD author to be really sure that his or her DVD will navigate correctly in all players, and to track down what is causing misbehavior.

Tracer is a tool to give you that control, in a visual and interactive environment. This tutorial will explain and demonstrate many of its features.

[inline:104_initial_tracer_window.jpg=Initial Tracer Window]

Above is the Tracer window as it first opens for the current active project, which simulates the player status of when a DVD is first inserted. Since we have just opened the DVD, Tracer displays the First Play PGC and its Pre Commands (see image above). The window is divided into several panes (or sections) containing everything we need to know about the status of the DVD's navigation. Explanations for each pane of the Tracer window follow below.

System Parameters

There are 21 System Parameters, also known as SPRMs, numbered from 0 through 20. In Tracer, most of these can be displayed in two notations: decimal or hexadecimal.

Some SPRMs represent user player settings and preferences, such as what language is "preferred" in menus (SPRM0). Another choice, or player characteristic, is the Region Code (SPRM20). Other SPRMs are the direct result of DVD navigation. Some system parameters can also be edited directly or indirectly by user operations on the remote, like the subtitle stream, for example.

SPRM14 is both a preference and a result. The preference is whether the screen is 16 x 9 or 4 x 3, and if 4 x 3, whether to choose pan and scan if available in 16 x 9 content, or letterbox. The result is how the player has chosen to play the current video, if video is playing, which depends both on the preference and on flags in the video attributes.

Those SPRMs which are preferences are saved in the general preferences file any time they are changed in Tracer. They are not saved in the project preferences.

To change the notation to decimal, click on Hex, found at the top of the SPRM pane. This will cause all of the numeric values to be displayed in hexadecimal, and change Hex to display as Decimal. To change back to hexadecimal notation, click on Decimal at the top of the SPRM pane. In addition, you may click on an individual SPRM description, which will change that particular SPRM to the opposite notation.

The SPRMs may be edited either by typing directly on the SPRM value or by choosing a popup where applicable. This is not "normal" in a DVD player, of course; the author in many cases may not change SPRM values - only create programming that reacts to them. The ability to edit SPRMs gives the author the power to test for all end-user player variables, ensuring that the DVD will function as intended.

General Parameters

There are 16 General Parameters, also known as GPRMs, numbered 0 through 15. GPRMs are registers similar to SPRMs, but are user-definable, controllable, and flexible. Generally, abstraction-layer DVD authoring applications take control of some GPRMs, in order to make programming certain kinds of functionality more easy for the user. In the command areas, in both the main and Tracer windows, they are referred to as simply r0 through r15, to save space and typing (r = register). The GPRMs may also be edited directly in the Tracer pane, and their notation changed between hexadecimal and decimal.

Resume Parameters

The Resume Parameters contain all of the information that the player saves when playback of a title is "interrupted," often by hitting the Title or Root Menu Call keys on the remote (various players use other names for these keys, such as Top Menu and Menu). This information is used to "Resume" play at the interrupted point. At this time the Resume Parameters are not editable.

Status Information

There are two lines of status information just below the Resume Parameters. The first line identifies the current location in the DVD structure, the largest unit of which is a Program Chain (PGC). PGCs are found in the following domains: First Play, Video Manager (VMG), Video Title Set Menu (VTSM), and Video Title Set (VTS). The status information displays the domain, and the relevant PGC, Title (TT), Program (PG), Cell, and Nav Pack numbers.

The second stus line identifies which category of commands are displayed, if any: Pre Commands, Post Commands, Cell Commands, or Button Commands. If there are no commands displayed, the second line will normally say "Waiting for Remote key...." When video is actively playing, this line will not display any information.

Remote

Tracer's remote offers full control over standard DVD player functionality. To simulate a DVD player's onscreen display when activating functions with potential multiple options (subtitle streams, for example), popup menus appear displaying all relevant and available choices. Additionally, some buttons will invoke a dialog box.

Many of these buttons correspond directly to "User Operations" in the DVD Spec. Most user ops can be permitted or disallowed at various times during the playing of the DVD, at the author's discretion. For example, most Hollywood DVD's force the user to watch the Copyright warning before you can start playing the movie. This is accomplished by disabling buttons that would allow the user to skip the warning and go directly to the main menu.

Buttons in Tracer are grayed out if the corresponding user op is disabled at the moment. Buttons are also (independently) italicized if their function is not appropriate or cannot do anything at the moment, even if it might be enabled. For example, if there is only one audio stream available, the remote prevents you from trying to choose another.

Rather than describe the button functions here, examples of their respective uses are given throughout the tutorial.

Trace Buttons

The Trace buttons control the execution of commands in Tracer. In a DVD player, the commands are always executed immediately when encountered; Tracer's Run mode is comparable to normal DVD player operation and playback.

The Step button executes commands one at a time, so the changes resulting from those commands in the Parameter Panes can be viewed step by step (System, General, and Resume). When a value changes, it is drawn in red for one command cycle.

The Stride button executes commands in groups, such as all of the pre commands in a PGC, and stops at each branch (Jump, Link, or Call) to another Cell, Program, PGC, or play of a group of Nav Packs with the same button highlights.

The back button steps backwards to the previously executed command.

The Show button reveals the current PGC in the main window of DVDAfterEdit 3, making the PGC available for further editing immediately.

Trace Slider

The Trace Speed Slider allows you to slow down or speed up the execution of commands as they display in the command pane.
The speed you set is remembered in the general preferences for the next use.

Preview Slider

The Preview Slider controls the video playback speed, from 1/15th to 15 times full speed.

The First Play PGC Pre Commands

Let's return to the sample project. After clearing GPRM0, the First Play jumps to Title 2. If you look in the main window and select Video Manager (VMG) in the left pane, and open up the Title Play Map in the right pane, you will see that there are two titles, one in VTS 1 and one in VTS 2. Each title is also labeled VTS_TT 1. That means it is the first (and only) title in that Video Title Set (VTS).

Strike the 'S' key, click the Step button, or choose Step from the Tracer Menu. You will see the arrow that was pointing at "1: Set r0 = 0" advance to point at the second command, "2: Jump TT 2". Nothing changes in the General Parameters since GPRM0 was previously a value of 0.

Now let's take a side trip to examine the Stop and Play keys in the Remote pane. The Stop key has the common square icon found on many set top remotes, and to its left is the Play key, the familiar hollow triangle icon. They're both near the lower left area of the remote.

Click on the Stop key. Notice that the status area now displays "Player stopped - waiting for user to start play". Now click the Play key; the First Play Pre Commands reappear. This is a simple way to start over in the Tracer window, and is also DVD Specification-compliant.

If video is playing when the Stop key is clicked, it will stop as in the previous example, but clicking the Play key will resume the video from where it was stopped. However, clicking the Stop key twice if video is playing will cause Tracer to navigate to the First Play PGC. This behavior is recommended in an addendum to the DVD Specification and is implemented in most players.

Now Step twice to execute both commands in the First Play PGC. Here is the resulting display:

[inline:104_first_play_pgc.gif=First Play PGC]

Not much has changed, except that now there is a black preview pane, and the status line displays:

"VTS 2, PGC 1 TT 2: PG 1, Cell 1, NavPack 1"

Click the Show Trace button. You will see PGC 1 TT 2 (1 program) highlighted in the left pane of the main window. If you open the triangles (drill down) to the lowest level, you will see each of the items in the status line above. Holding down the option key while clicking on a triangle will open all lower-level items.

Notice that the QuickTime Controller at the bottom of the Preview pane shows the play head at the very end of the black video. Since we used Step to get to this point, Tracer stopped after the last frame of video instead of going directly to the Post Commands. Click Step again; the following Post Command is displayed in the status information:

"Call VMG PGC 1 resume C1"

(continued...)

Tracer Tutorial, Part 2

The Title Menu Pre Commands

When you click Step again, the command area will change to the following:

1: if r0 == 0 then GoTo Line 4
2: Set Button 2
3: GoTo Line 5
4: Set Button 1
5: Set r0 = 0

These are the Pre Commands for the Title Menu. If you press the Show button, DVDAfterEdit will highlight VMG PGC 1 in the left pane of the main window, and if you click on it, you will see "entry PGC yes" in the right pane . This is the VMG entry PGC, which will always be executed when the viewer presses the Menu Call Title Key in the remote.

[inline:4=center,VMG entry PGC]

The video preview still has not changed. Try stepping backwards to the beginning of the First Play, and then forwards again to these Pre Commands. You should be starting to get the idea of how DVD navigation works. A DVD is split up into "Domains," and the commands are quite flexible within the current domain but somewhat limited on how they can travel to different domains. So far we have started in the First Play domain, jumped to the Title Domain to play half a second of black video, then called back to the Video Manager domain in order to eventually display the Main Menu.

The primary function of the above Pre Commands is to determine which button will be set to highlight upon arrival at the Main Menu. Now look at the General Parameters; notice that since GPRM0 (r0) is still 0, navigation will skip over lines 2 and 3 to Pre Command line 4, where Button 1 will be set to highlight. Line 5 will ensure that r0 is set to 0 again, so the next time navigation returns to this PGC, the DVD player will highlight button 1 unless r0 is changed somewhere else. This is a case of the author (Ben) trying to make things easy for the viewer by having the DVD player highlight the last button activated from the Main Menu (such behavior is, of course, up to the author to decide).

Now Step again; Tracer leaves the Pre Commands, and displays the video for VMG PGC 1, which is the Main Menu.

[inline:3=center,main menu]

The status line displays "Waiting for Remote Key...," which means that the Tracer is waiting for the user to activate a remote button. The Button Highlight pane to the left of the Preview pane shows the hot spot borders of all visible buttons contained within the current PGC. Notice the solid white box in the same relative position as the words "PLAY MOVIE" in the image; this indicates that the "PLAY MOVIE" button is currently selected.

Interestingly, if we were to go back to the First Play and start over, clicking Run this time instead of Step, you will see all of the above navigation take place without stopping (except to fetch data from the disk and build a QuickTime preview) at a speed determined by the setting of the Trace Speed slider. For still menus like the one in this example, the player will stop when input is required from the viewer. For motion menus, Tracer will continue playing the video as instructed by the programming, while permitting you to select and activate the buttons.

Selecting Buttons in the Title (Main) Menu

Inside the Remote pane you will see the Enter button surrounded by four directional keys. The arrow and enter keys on the keyboard are shortcuts for these, and are also available from the Tracer menu. When you press the up or down arrows, the button highlight pane will change to show the newly selected button as a solid white box. The right and left arrows are not active for this PGC, which is representative of the way Ben authored the DVD.

If you return to VMG PGC 1 in the left pane of the main window and drill down through the DVD structural levels to the (only) Nav Pack, you will see entries for Button Navigation 1 and Button Navigation 2. When expanded, you will see the button navigation information, including which button is selected when each of the four directional buttons is pressed. If you wish, you may change the entries for "Button no. to select if 'Left' pressed", etc., and when you switch back to the Tracer window the behavior will be changed.

Activating the PLAY MOVIE button

From the Main Menu of the sample project, make sure that the top button is selected, then press the Enter button found in the Remote pane. This will activate the button, just like a normal DVD player, causing the associated button command to execute. In this example, the entire movie will play through its four chapters. You may adjust the preview speed at any time by dragging the Preview slider, or by clicking on the <- Scan and Scan -> keys in the remote pane.

[inline:2=center,drag Preview slider]

In Tracer, the QuickTime movie controller at the bottom of the Preview pane (see image above) is always set to show the duration of the current PGC. For this project, the main movie resides in VTS 1 and consists of a one-sequential PGC. This PGC is broken into four parts, and each part is, at the same time, a Part of Title (PTT), a Program (PG), and a Cell. This type of simple DVD structure is common, though sometimes Programs are are not PTTs, and Programs can have more than one Cell.

As the video begins to play, you will notice that one fourth of the controller's location slider is drawn in dark gray and the rest in light gray. When the first chapter finishes, the dark portion changes to the next one-fourth of the controller length. Tracer subdivides each PGC into its unique sections contained within, all the way down to the Cell level, and even to each group of Nav Packs with similar button highlight information. This enables the user to control playback and tracing to the lowest structural level of the DVD specification.

Setting a Breakpoint

To see how the this DVD navigates from the Main Menu to the Scene Selection Menu, let's look at the commands in the Main Menu PGC and its one and only Nav Pack. When the movie has been played, the DVD navigates to the Main Menu, highlighting the first button. Now press the Show Trace button; this highlights VMG PGC 1 in the left pane of the main window (we did this earlier when examining the Title Menu Pre Commands).

Option-click on the VMG PGC 1 disclosure triangle, then click on Nav Pack 1 in order to select it. In the Button Navigation section in the right pane, you will see two Button Commands (click on the disclosure triangles if they are hidden):

1: Jump TT 1 2: Link TailPGC

These Button Commands correspond to the two Main Menu buttons. Control-click on command 2 (for button 2) and choose "Set Breakpoint" from the contextual menu. The disclosure triangle will change to red, which means that Tracer will stop if this command is encountered while emulating the DVD.

Go back to the Tracer window, and click on the down arrow found in the Remote pane (or use the arrow key). You will see the button selection change from the PLAY MOVIE button (button 1) to the SCENE SELECTION button (button 2) in the Button Highlight pane. Now press the Enter remote button. Tracer displays the following image:

[inline:1=center,choose scene selection]

Notice how Tracer stops playback at the "Set Breakpoint" location and the command-line cursor is now red. The Link TailPGC Button Command navigates to the Post Command area of the current PGC. Press the 'S' key (or click Step) and you will see the following commands in the Command pane:

1: Set r0 = 1 2: Set r1 = 0 3: Jump VTS 1 Menu Root

You may Step (or Stride) through these commands, which will navigate to the Pre Command area of VTS 1 Menu Root (VTSM PGC 1). The following commands are displayed (values are in hexadecimal notation):

1: if r0 == 1 then GoTo Line 3
2: Jump VMG PGC 1
3: if r1 != 0 then GoTo Line 6
4: Set r1 = $400
5: GoTo Line 13
6: if r1 != 5 then GoTo Line 9
7: Set r1 = 4
8: GoTo Line 11
9: Set r1 = Part title
10: if r1 < 3 then GoTo Line 12
11: Link PGC 2
12: Set r1 *= $400
13: Set Button r1

Selecting the Scene Menu and the Button to Highlight

As explained in Ben's article (http://www.dvdafteredit.com/public/107.cfm), these commands decide which of the two scene selection menus to display and which button is set to be selected. Since this is the first time we have navigated to the Scene Selection Menu, we would expect to display the first Scene Selection Menu with the first button selected, and indeed that is what happens:

[inline:5=center, display the first Scene Selection Menu]

Conclusion

You should now have enough familiarity with Tracer to navigate through the remainder of the paths in this relatively simple DVD. Experiment and observe how the logic works. If you have little experience in this kind of scripting/programming, please refer to Ben's explanations in the original article for further help. If these concepts are new to you, it is much easier to understand them when you can see how things happen step-by-step with Tracer.

One difficult aspect of DVD commands is the limitation built in to each command, particularly how they navigate from one domain to another. Examining the various types of commands listed in the popups while working in the right pane of the main project window can be quite instructive in that regard, since the popups will only show those options that are valid in the relative context being viewed. For example, commands that may be part of the DVD Specification in a VTSM PGC but are not relevant to a VMG PGC are not displayed. We will also be adding more explanations and examples to the site to further assist users. Stay tuned!

Understanding Hexadecimal, Nibble by Nibble

Why should we learn hexadecimal notation?

In DVD Spec commands, there are only 8 registers available to the author, if he or she is using an abstraction-layer authoring system such as DVD Studio Pro, or 16 if there is no abstraction layer, such as in Creator or Scenarist, or if you replace the abstraction layer and author from scratch in DVDAfterEdit.

To make better use of these registers, each register can be split up into individual "fields" to be treated individually. Since registers contain 16 bits, there could be 16 individual bit fields that each kept track of a single on/off state. (Binary bits are either on or off). Or it could be split up into 4 fields of 4 bits each. (It is quite often useful to do this).

Bit fields don't translate to decimal values very well. For example, the rightmost (lowest) bit in a register has a value of 1. The highest bit has a value of 32768. The next highest bit has a value of 16384. (Notice these are all powers of 2). Combining or doing arithmetic on groups of these bits in decimal would be very tedious and confusing. But good news! Once you understand hexadecimal, it becomes much easier.

Hexadecimal

Hexadecimal is base 16 arithmetic. This means that each digit in hex has 16 possible values, instead of 10 in decimal or 2 in binary. This is very good for three reasons:

1. Sixteen is a power of two, 2 ** 4.
2. Base 16 numbers require four bits to represent them.
3. Four bits is evenly divisible into the 16 bits in a register.

These facts all combine to make it easy to work in hexadecimal, as you will discover as you continue reading this document. If you plan to do extensive DVD Spec "scripting", it would be a good idea to buy an inexpensive hex calculator.

In hexadecimal notation, each digit is commonly referred to as a "nibble". The possible nibble values are:

[inline:51_hex_nibbles.gif=hexadecimal nibble values]

The DVD Spec uses registers that are 16 bits long. This equates to four nibbles of four bits each. This means a register can hold a value from 0 to FFFF in hex, which is 65,535 in decimal.

Two's complement arithmetic

Typically in the DVD Spec, all values are positive numbers only. But almost all microprocessors, including all of those in DVD players, use "two's complement" arithmetic, which essentially allows you to think of these values as negative values if you wish. In two's complement arithmetic -1 is represented as $FFFF (we will use $ to represent hexadecimal numbers from here on out).

As an exercise let us add one to 9999 (decimal). We add one to the lowest 9, and get 10. We write down the zero and carry the one. We add the carry to the next digit, also 9, and get a similar result. When we finish we have 10000.

Now let us add one to $FFFF. We add one to the lowest F and get $10 (16). We write down the zero and carry the one, etc. When we are finished we have $10000. But only four nibbles fit in our register, so the last carry is thrown away, and the result is zero.

So you can see that in two's complement arithmetic, -1 + 1 still equals zero. For scripting purposes, we don't really need to know much more than that, except that it would is possible to store a negative value in a register, and our good old hex calculator will tell us what that value should be, if we need to know.

Binary bits

The DVD Spec uses the Boolean operators "and", "or", and "exclusive or". These operators only make sense using binary notation. But hex is a good way to organize your binary data into manageable chunks. With a little practice it is very quick to translate a hex number into binary by drawing out the nibbles on a piece of scratch paper, thus:

$06FF:
0000 0110 1111 1111

$1ABC:
0001 1010 1011 1100

(Please refer to the table, above, to get each nibble of the 16-bit hexadecimal number).

Then you can isolate the piece of the GPRM or SPRM you are interested in by drawing a long vertical line between the appropriate bits (counting from the right as bit 0), and apply the Boolean logic to it. (I'll explain Boolean logic in a moment).

For example, button numbers are stored in SPRM's and referenced starting with button number one having a value of 1024, or $0400. Button two is $0800, button 3 $0C00, etc.

So my example of button number one would be drawn thus:

0000 01|00 0000 0000

(On paper you would make the vertical bar taller.) If you draw all of the possible buttons out you will see that the 10 bits to the right of the button number are always zero. This means that scripting can keep track of a button number and still have 10 more bits to play with in the same GPRM!

This concept is extremely powerful, and is what permits complicated navigation with only 16 GPRM's. Essentially, GPRM's are very expensive, and commands are cheap since you can have up to 128 of them in each PGC, and you can have tons of PGC's.

Boolean Logic

The three Boolean operators used in DVD Spec commands are "and", "or", and "exclusive or". These operands are usually represented by the operators "&", "|", and "^".

Boolean operators are applied one bit at a time to two operands, and each bit in an operand is compared to the same bit in the other operand. The result of the compare is stored in the destination operand. (In DVD commands, the destination is always a GPRM, or a "temporary value" (never stored) in an if statement).

"and": If both bits are true (1), the resulting bit is true.

"or": If either bit is true, the resulting bit is true.

"exclusive or": If either bit is true, but not both, the resulting bit is true.

Some examples:

$0010 & $0011 = $0010
$0011 & $1000 = $0000
$0001 | $0010 = $0011
$0000 | $abcd = $abcd
$8000 ^ $8000 = $0000
$e000 ^ $4000 = $a000

etc.

An abstraction layer example

Following is an abstraction layer example from DVDSP 1.5, which was written before DVDSP 2.0 was shipped. Although the abstraction layers for the two products are different, the principles are the same.

This example was also written before DVDAfterEdit supported the hexadecimal preference for commands. Here in this update we will show the hexadecimal. For those who have read the previous version of this document, you will see that this makes the code much easier to follow.

If you look at a typical DVDSP 1.5 project, at the Video Title Set Menus, you will see that the first 20 lines of PGC 2 are always identical.

1: Set r15 = r8
2: Set r15 ^= $E000
3: if r15 & $8000 then GoTo Line 7
4: Set r14 = r8
5: Set r14 &= 7
6: Set Stream Audio r14
7: if r15 & $4000 then GoTo Line 13
8: Set r14 = r8
9: Set r14 /= 8
10: Set r14 &= 63
11: if r14 != $3F then Set r14 |= 64
12: Set Stream Subpic r14
13: if r15 & $2000 then GoTo Line 18
14: Set r14 = r8
15: Set r14 /= 512
16: Set r14 &= 15
17: Set Stream Angle r14
18: Set r8 = 0
19: Set r15 = r13
20: if r15 == 0 then Link Resume

This code is using a single GPRM, r8, to hold three flag bits and three values. Before reading any further, notice that $E000 has three bits on, $8000 has one of those same bits on, $4000 has another, and $2000 has another. Gee, there must be a method to this madness!

Here is a picture of the bits as they are arranged in register 8:

[inline:51_bits_arranged_reg8.gif=center,bits as they are arranged in register 8]

Now to describe each command line and what it does:

1. This brings register 8 into a "work" register, r15, so that we can see what is in it without destroying register 8.
2. "Exclusive or" the register with the value $E000. This will invert the top three bits in the register and leave the lower 13 bits unchanged.
3. This tests the work register against the value $8000. If it is on, we skip over the next few lines. This means that the high-order (leftmost) bit was off originally, since we "flipped the bit" by exclusive or'ing it with a one bit in that position (the $8000 part of $E000).
4. We move the original register 8, the interesting one, into another work register, r14. We use another one because we are not through with the current value of r15, see below.
5. We "and" the value of r14 with 7. This eliminates any extra bits to left of the first three (bits 0 thru 2), yielding a result that is guaranteed to be in the range 0-7.
6. We now set the audio stream to a legal value.
7. This tests the work register against the value $4000. If it was originally off (now on), we skip to line 13.
8. We move that same register r8 to the second work register.
9. We divide the value by 8. This removes the three bits that might have contained an audio stream, and moves the next interesting 6 bits to the rightmost part of the register. Any time we divide by a power of 2 (8 = 2 ** 3), it is the same as shifting the bits in the register to the right by the power number positions.
10. We "and" the value with $3f. This isolates 6 bits of a sub picture stream. The sub picture SPRM uses values 0-31 for stream numbers, and a value of 63 to indicate a "dummy stream".
11. If the value is not 63 we "or" in another bit, 64 (bit #6). This bit "on" means display the sub picture stream. This bit off means do not display it.
12. We deposit the register (r14) into the SPRM (SPRM 2).
13. We test the work register against $2000, and skip to line 18 if it was originally off.
14. We get the interesting variable.
15. We divide it by $200, getting rid of the nine bits we have already used up.
16. We "and" it with $f, leaving a number between 0 and 15.
17. We deposit the angle (1 thru 9) into the SPRM. We assume the angle number is correct, since it was generated by the abstraction layer.
18. We have used up the register 8, which held up to three values that needed to be transferred to their SPRM's, so we clear it to zero so that the next time we won't have to repeat the steps above, since the SPRM's will keep track of it handily.
19. We get r13 so we can test it.
20. If r13 was zero, we do a Link Resume.

From here on out, the individual menus "do their thing", usually testing r13 for particular values to go to particular places.

Notice that the abstraction layer coding isn't particularly efficient in the number of instructions used, but is very efficient in its use of the bits in general parameters.

For example, the abstraction layer designer could have reversed the meaning of the three high-order bits in register 8, which would have saved the instructions which had to move the bits to another register and invert them in order to test each bit. But this sort of optimization is unimportant in typical navigation, since commands themselves execute in microseconds and there is room for 128 of them in each PGC. It is only when we actually jump to other domains and areas that navigation slows down.