[FFmpeg-trac] #11454(undetermined:new): Ogg/Theora: Bad granulepos when GOP higher than 64

[FFmpeg]

#11454: Ogg/Theora: Bad granulepos when GOP higher than 64
-------------------------------------+-------------------------------------
             Reporter:  Bernat       |                     Type:  defect
               Status:  new          |                 Priority:  normal
            Component:               |                  Version:  git-
  undetermined                       |  master
             Keywords:               |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
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 When encoding Theora video streams in an Ogg container with GOP size
 higher than 64, granulepos is wrong. The encoding is done with the right
 GOP size but the granulepos reported when decoding is wrong.

 Here's an example from a file encoded with the following command:

 {{{
 ffmpeg -i input.mp4 -c:v libtheora -c:a libvorbis -g:v 300 output.ogv
 }}}

 The output plays fine but when analyzing the frames we can find this:

 frame 192:
   granulepos: 575
   key-frame: 129
   offset: 63
   Theora API function th_packet_iskeyframe() returns false.
 frame 193:
   granulepos: 33280
   key-frame: 192
   offset: 0
   Theora API function th_packet_iskeyframe() returns false.

 So in both cases the decoder thinks these aren't key-frames and it should
 be right.

 But the granulepos of the second frame is constructed as if it was a key-
 frame. It should be like this instead:

 frame 193:
   granulepos: 576
   key-frame: 129
   offset: 64

 It looks like the encoder knows the GOP size is 300 but the code writing
 the granulepos thinks that the GOP size is 64.

 Anyway I could help please ask me.

 Thanks for your time.
 Cheers.
-- 
Ticket URL: <https://trac.ffmpeg.org/ticket/11454>
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