[FFmpeg-trac] #11553(ffmpeg:open): Suboptimal logic in "ffmpeg_dec.c" may glitch abnormal VP9 decoding (was: BUG error code returned when decoding vp9)

[FFmpeg]

#11553: Suboptimal logic in "ffmpeg_dec.c" may glitch abnormal VP9 decoding
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             Reporter:  jasper      |                    Owner:  (none)
                 Type:  defect      |                   Status:  open
             Priority:  normal      |                Component:  ffmpeg
              Version:  git-master  |               Resolution:
             Keywords:  ffmpeg_dec  |               Blocked By:
             Blocking:              |  Reproduced by developer:  1
Analyzed by developer:  1           |
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Changes (by MasterQuestionable):

 * component:  avcodec => ffmpeg
 * keywords:  vp9 => ffmpeg_dec
 * summary:  BUG error code returned when decoding vp9 => Suboptimal logic
     in "ffmpeg_dec.c" may glitch abnormal VP9 decoding

Comment:

 ͏    It's not a bug in the decoder, but in the FFmpeg CLI tool.
 ͏    In "packet_decode" in "ffmpeg_dec.c", an "AVPacket" is sent to the
 decoder:
 ͏    |*| If "avcodec_send_packet" does not return an error: the "AVFrame"s
 are received until the decoder signals "EAGAIN".
 ͏    |*| If an error happens: no call to "avcodec_receive_frame" happens
 ͏    ; and the decoder is supposed to need new input to produce any
 output.

 ͏    This is wrong for VP9 (and maybe some other decoders), as there is a
 BSF (Bitstream Filter?) involved.
 ͏    And the BSF need not have been completely drained.

 ͏
 https://github.com/FFmpeg/FFmpeg/blob/848576b4dfdbacf42017bb81c755482dc6845cc5/fftools/ffmpeg_dec.c#L697
 ͏    https://ffmpeg.org/ffmpeg-bitstream-filters.html
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Ticket URL: <https://trac.ffmpeg.org/ticket/11553#comment:9>
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