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Can one freely change the division of a title into chapters?
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aarons
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Joined: 04 Feb 2006
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PostPosted: Sat 04 Feb 2006, 13:32 Reply with quote

I've been using and learning from myDVDEdit for over a month now. I've been generally pleased with it, but frustrated by the apparent inability to modify the division of a title into chapters. I just downloaded 0.9.7, thinking from the description that it would allow me to do this. I spent about an hour trying to figure out how to do it, but nothing seems to work.

The list of new features includes
> - Add/Delete Chapter.
but it seems to only allow chapters to consist of one or more previously existing cells.

Is it possible to change the division of the title into cells so that cells, and therefore chapters, can began at an arbitrary point in the title? If it isn't possible, is there a reason other than that it hasn't been implemented yet?

I'm new to this forum, BTW. Although I prefer English, I can understand replies in French if they're not too complicated. Smile
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Jerome
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PostPosted: Sat 04 Feb 2006, 14:01 Reply with quote

By definition, a chapter can only be a program, so yes, this version can only add/remove the chapter marker of each program.

What you want is to split a cell to create a new program and than a new chapter.

I'm sorry, myDVDEdit cannot do that yet. To do it , I must modify all objets (in the VOB files) of the cell to split. versions before the 1.0 only modify the IFO files.

This fonctionnality is planned in the version 1.0. I hope this spring.

The next version 0.9.8, is planned for this month. It wasn't plan before but many important bugs are found in the 0.9.7. Version 0.9.8 should fixe them and add buttons edition fonctionnalities.

Jerome
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aarons
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PostPosted: Sun 05 Feb 2006, 00:15 Reply with quote

I'm really curious:

In the data structures of Objects as displayed by myDVDEdit, time codes and byte offsets appear to be given relative to the start of the PGC or some higher-level structure, not the start of the individual Cell within the PGC. If this is in fact the way they are actually encoded in the VOB files, they (time codes, etc.) wouldn't have to be changed.

What information, then, in the VOB files themselves would have to be changed for the grouping of Objects into Cells to be changed? Confused
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Jerome
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PostPosted: Sun 05 Feb 2006, 01:27 Reply with quote

1) Information in the MPEG stream is not the problem because they are not used by the DVD player (except by bad DVD players) to synchronize the data.
So the timeCode can be wrong, it is not realy a problem.
Data are synchronized by the SCR (System Clock Reference) in the Pack Header, DTS (Decoder Time Stamp) and PTS (Presentation Time Stamp) in the stream header.
DTS point when a picture must be decoded and PTS, when the picture must be shown.

2) So what is the problem with cells ? In PCI (Presentation Control Information) and DSI (Data Search Information).
PCI/DSI are the first 2048 bytes of each object (or VOBU).
Many important information are stored in PCI and DSI, like the VobId, cell elapsed time, and a lot of offsets to previous and next objects, used to simplify different play speeds.(offset to the object 0.5s forward/backward, 1s forward/backward, 2s forward/backward..., 30s forward/backward).
If you want to split a cell, all these offset must be updated because offset from one cell to a other a not allowed.

A other problem is subpicture. They cannot start in a cell an continue in a other. Same this buttons, and subtitles. All this must be checked.

3) Why Chapter must be a program.
Chapter are not stored in the IFO structure with a timeCode or any time information. It cannot be, and must not be. Chapters can be found with a table associate to each VTSTitle. For each chapter this table tell the corresponding PGC number and program number.

Jerome
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aarons
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PostPosted: Thu 16 Feb 2006, 08:39 Reply with quote

Thanks for your explanations, Jérôme! I really appreciate your willingness to answer users' questions in detail.

I did look into the PCI/DSI data and understand the part about forward and back searching, i.e., that (for whatever reason) offsets are not given to objects in another cell. (I would be curious to know what would happen if one were to ignore the offsets and create a new cell division, though. Would the DVD player do something strange when jumping over such a division?)

But even if one cannot change the grouping of objects into cells without altering the VOB files, the following question remains:

Can one alter the grouping of cells into programs (so as to be able to create new chapters) without altering those VOB files? In other words, is there something in the VOB file itself that differentiates a cell that starts or ends a program from one that doesn't?

I also have a minor question about your explanation. You say that "information in the MPEG stream is not the problem" but that information in the PCI and DSI is the problem. But aren't the PCI and DSI part of the MPEG stream?
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Jerome
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PostPosted: Fri 17 Feb 2006, 19:31 Reply with quote

It's really depends of many things
One cell can be use in more then one PGC.
Suppose 3 cells, cell A,B and C
PGC1 can use cell A and B, and PGC 2, cell A and C.
If some offsets in cell A are set to cell B, a play in fast speed of PGC 2 could trap the player.

Some information, like the vodId, and cell time is recorded in each object of the cell. Spliting a cell without changing this information could be fatal (depends how the player works).

Do not confuse VOB information and IFO information. A PGC is a list of PRGM, a PRGM is a list of CELL, and a cell is .... nothing but a REFERENCE to a list of objects (VOBU). If you move a cell or a PRGM or a PGC in one PGC, the VOBU doesn't change, because CELLs are only a REFERENCE to a list of VOBU.

Nothing in a cell deferentiate a cell that starts or ends a program from one that doesn't. BUT, you could have problems if the first object of the cell if not close. What that's meens:
A open cell is a cell with a open first object.
A open object is a object witch depend of the previous.
In a MPEG compression, only one frame each 0.5 second is real, all the others are calculated. the frame computing are made from the previous frame and the next frame, except in closed object wich start with a real frame and do not depend of a previous frame.
With a PGC with three cells, A, B and C. if B is a open cell and if you change the cell order to ACB, the the first frame of the B cell are calculate with a bad previous frame.

- to finish: MPEG.

VOBs files are more then MPEG streams.
A pure MPEG stream only contain video data or audio data, but not the twice. to have all this information in one file, the streams are fragmented in sectors with a header to know what kind of data is in the sector and to synchronyse it.
in DVDs the sectors have always 2048 bytes length.
all sectors are mixed and grouped (multiplexed) in a block of about 0.5s.
You add the PCI/DSI sector, and you have a object (VOBU= Video Object Unit).

Jerome
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Skeeve
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PostPosted: Fri 20 Mar 2009, 17:10 Reply with quote

I think, this can be done by using dvdauthor. I think dvdauthor is the solution to many of the problems we face here.

I don't know how fast I will be but I will try to put up some examples how to use DVD author for some of our problems.

I think it would be a good idea, if Jérôme can integrate dvdauthor into myDVDEdit. Why reinvent the wheel?
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