[FFmpeg-devel] frames not parsed correctly for VOB file (mpeg2)

Michael Niedermayer michaelni
Wed Feb 3 17:04:06 CET 2010

On Wed, Feb 03, 2010 at 10:52:23AM +0100, Christian Cier-Zniewski wrote:
> Christian Cier-Zniewski schrieb:
>> I have analyzed the packet data a bit further and realized that it mostly 
>> contains at least two frames, instead of a single frame which would I 
>> expect to be correct.

they are called field pictures

>> Going a bit deeper in the libraries I found out that it must be the 
>> function ff_mpeg1_find_frame_end() which does not correctly recognize the 
>> end of a frame in this VOB file.
>> Could somebody please have a look at the VOB file and state that it is 
>> indeed the aforementioned function which does not work correctly?
> Please find attached a patch which corrects the problem that 
> ff_mpeg1_find_frame_end() does not recognize the frame end in case of this 
> type of VOB file.

your patch will break timestamp handling
i suggest you look in svnlog we did had an alternative implementation
of things that did not merge field pictures but i changed it to what we
have now because it at that time appeared simpler. I had not considered
apparently that one could store timestamps on only the wrong fields.
Iam not opposed to replace the current code by what we had previously
if someone (like you) provides a patch that does this. I guess this will
involve some adapting of the old code from compute_pkt_fields() the
rest might be simple apply the diffs
And of course it would require some testing with mpeg-ps/ts and h264

Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

I do not agree with what you have to say, but I'll defend to the death your
right to say it. -- Voltaire
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