VOB timestamp reset

extra · 29th June 2009, 17:01

I have a VOB file:
http://www.dvdloc8.com/distributorcl...id=15&clipid=2

The present time stamp increases but will reset to zero and start over again near the end of the file. Does anyone know why it works like this? Is this the reason many player could not recognize correctly the play duration of a vob file? How are decoders/demuxers supposed to deal with this?

Thanks for any help!

Guest · 29th June 2009, 17:14

It's not that unusual because the leadin is often encoded separately from the main movie, etc.

extra · 29th June 2009, 19:11

In this case shouldn't the leadin and main movie have two different Stream ID? In this file, the Stream ID for video is the same, always 0xE0... Should the demuxer regard them as two different streams?

Guest · 29th June 2009, 19:32

Quote:

Originally Posted by extra

In this case shouldn't the leadin and main movie have two different Stream ID?

I'm not aware of any spec that asserts such a thing.

Quote:

Should the demuxer regard them as two different streams?

Not at the elementary video syntax level. Aren't they differentiated in the DVD structure?

extra · 30th June 2009, 15:22

Quote:

I'm not aware of any spec that asserts such a thing.

But if we stick to the spec of MPEG2 program stream, the last few packets should be displayed at the very beginning of the program, causing duplicate timestamps... I must be missing something, like a new time reference...

Quote:

Not at the elementary video syntax level. Aren't they differentiated in the DVD structure?

VOB file is 100% MPEG2 program stream compatible... so I guess it should be able to play correctly even without the DVD structure. Am I wrong?

Guest · 30th June 2009, 15:53

Quote:

Originally Posted by extra

But if we stick to the spec of MPEG2 program stream, the last few packets should be displayed at the very beginning of the program, causing duplicate timestamps... I must be missing something, like a new time reference...

I suppose you are missing the SCR, which is the timebase of the stream.

Don't forget that the timestamps (SCR, PTS, DTS) are a finite size in bits, so they can wrap back to zero in normal operation.

29th June 2009, 17:01	#1 \| Link
extra Registered User Join Date: Apr 2009 Posts: 10	VOB timestamp reset I have a VOB file: http://www.dvdloc8.com/distributorcl...id=15&clipid=2 The present time stamp increases but will reset to zero and start over again near the end of the file. Does anyone know why it works like this? Is this the reason many player could not recognize correctly the play duration of a vob file? How are decoders/demuxers supposed to deal with this? Thanks for any help!

29th June 2009, 17:14	#2 \| Link
Guest Guest Join Date: Jan 2002 Posts: 21,901	It's not that unusual because the leadin is often encoded separately from the main movie, etc.

29th June 2009, 19:11	#3 \| Link
extra Registered User Join Date: Apr 2009 Posts: 10	In this case shouldn't the leadin and main movie have two different Stream ID? In this file, the Stream ID for video is the same, always 0xE0... Should the demuxer regard them as two different streams?