[Matroska-devel] Spec Change (chapter start time)

Steve Lhomme steve.lhomme at free.fr
Sat Jan 8 17:55:58 CET 2005

Steve Lhomme a écrit :
> Mike Matsnev a écrit :
>> Steve Lhomme wrote:
>>> In the specs the ChapterTimeStart is mandatory at all levels. But 
>>> that has no sense for EditionFlagOrdered = 1.  I'm thinking about 
>>> removing the mandatory property. Any objections ?
>> So what's the meaning of such chapters? Can they be safely ignored?
> 1) logically grouping elements
> 2) knowning the corresponding DVD level (SS, PGC, Program, Cell, etc) of 
> this group (through the corresponding CodecPrivate)
> This way when you encounter a JumpSS you are going to jump to that 
> group. It would be much complicated with a flat list because each cell 
> (the lower level of DVDs) would need to contain the SS, PGC, Program it 
> refers to.

So, is it OK to remove the mandatory flag for ChapterTimeStart ?

I'm modified DMX to keep most of the start timecodes. But I had to 
remove the PTT level because it's just a seek point. I'm not sure if I 
can remove it totally or I have to take it back with some more changes 
in the code... Actually it's one element which StartTime is vital, but 
I'm not sure it's needed. I'll check if there are DVD commands relating 
to the PTT level, otherwise it will be totally dropped...

Also another thing we need is a better identification of segments. For 
example the VMG segment (first used when you enter a DVD) usually have a 
command JumpTT # (jump to title # x). That means jumping to another 
segment. But so far we don't know how to map the title/domain to a 
meaningfull element in Matroska. The Segment UID is an ID that should 
unique over a lot (global) of Matroska files. It could work, but only if 
you modify the value in the DVD command. IMO, that's not the way to go. 
We should have a better way to map the domain to an ID in the Segment 
Info. Hopefully something that would not be DVD specific, but more general.

Comments are welcomed !

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