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

Michael Niedermayer michaelni
Wed Feb 3 19:49:51 CET 2010

On Wed, Feb 03, 2010 at 07:40:48PM +0100, Christian Cier-Zniewski wrote:
> Michael Niedermayer schrieb:
>> 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
> Just before reading your reply I realized that the material is interlaced 
> and that it is correct to return two fields in one packet.
> Thanks for clarifying that. That is what I want. My patch is indeed wrong.
>> 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.
> Could you please explain what you mean by "on only the wrong fields"?
> Since it is ok to have the two fields per packet I have no need to change 
> the current implementation.

a packet has its timestamps associated with the start of presentation/decode
the second field is later thus timestamps associated with the second field
can never be returned as they are. (i assume this is the problem with this
Outputing 1 field per packet solves this with the old code for
h264 also returns 1 field per packet for PAFF and has to because in h264
field pictures dont have to be paired that is you can have 
frame field frame field field frame field field field frame
ive never seen such a sample but i guess thats just because the encoder
developers all are sane enough still


Michael     GnuPG fingerprint: 9FF2128B147EF6730BADF133611EC787040B0FAB

Those who are too smart to engage in politics are punished by being
governed by those who are dumber. -- Plato 
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