[FFmpeg-trac] #8343(avcodec:new): h261dec doesn't mark keyframes

FFmpeg trac at avcodec.org
Wed Oct 30 15:01:46 EET 2019

#8343: h261dec doesn't mark keyframes
             Reporter:  Lastique  |                     Type:  defect
               Status:  new       |                 Priority:  normal
            Component:  avcodec   |                  Version:  4.2
             Keywords:            |               Blocked By:
             Blocking:            |  Reproduced by developer:  0
Analyzed by developer:  0         |
 h261dec does not set AVFrame::key_frame field on keyframes. As a side
 effect, frame skipping except keyframes doesn't work (all frames are

 In H.261, keyframes are normally indicated by the Freeze Picture Release
 bit in the Picture Header of a frame, but h261dec ignores that bit.
 h261enc behavior is to set that bit on keyframes.

 The problem was discovered in a client application that uses ffmpeg
 through its C API. I'm not sure if it can be reproduced through command

 Attached is a patch that fixes the problem. The patch has been posted on


Ticket URL: <https://trac.ffmpeg.org/ticket/8343>
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