[Ffmpeg-devel] problem decoding frames when first frame is B

Mathieu Monnier manao
Mon Apr 23 20:58:05 CEST 2007

 >>>>> Open GOP makes some sense when
>>>>> random access is impossible, such as broadcast, which is where it
>>>>> is primarily found.  DVD uses closed

Open gop always make sense.

>>> So it is not possible to decode the first two frames?  Is this true
>>> even with the latest svn version of ffmpeg?

It can't be decoded if the broken link flag is set to 1 in the gop 
header. I wouldn't trust a broken link flag anyway, and I would bet 
anyway that they aren't decodable

>> The first frame produced when the decoder is switched on must be
>> possible to decode somehow.  If you jump into the stream at a later
>> point you'll always have a couple of initial B-frames with one
>> reference before your starting point.  Not even FFmpeg can invent this
>> missing data.  The decoder copes with it just fine though, so there's
>> no big deal.

I think it rather seek to the following intra.

> I am building a frame accurate video decoder using ffmpeg and I need to be
> able to decode those frames. 

I don't think you can.



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