[FFmpeg-trac] #4888(avcodec:new): 62bd8deef causes a regression in HEVC decoding

FFmpeg trac at avcodec.org
Mon Sep 28 21:03:05 CEST 2015

#4888: 62bd8deef causes a regression in HEVC decoding
             Reporter:  staalebk    |                    Owner:
                 Type:  defect      |                   Status:  new
             Priority:  normal      |                Component:  avcodec
              Version:  git-master  |               Resolution:
             Keywords:              |               Blocked By:
             Blocking:              |  Reproduced by developer:  0
Analyzed by developer:  0           |

Comment (by heleppkes):

 Thinking about this some,  I think this is an unfortunate side-effect of
 fixing the parser bug that we had before.

 Without the patch, the demuxer would be unable to extract SPS/PPS/VPS from
 the stream, and thus the decoder would be incapable of actually decoding
 early frames in the stream - it would only start decoding on an IDR frame,
 which also includes the SPS/PPS/VPS again.

 Now, the demuxer can extract SPS/PPS/VPS, and as such, the decoder can
 start decoding right away - even if the first frames are missing
 references, and as such will decode corrupted.

 Unfortunately, there is no quick fix, as having the SPS/PPS/VPS is quite
 essential for many other workflows. The proper fix would be to teach the
 HEVC decoder to discard corrupted frames.

 Anyway, I'm not 100% sure this is the full explanation, but its the most
 reasonable one that comes to mind.

Ticket URL: <https://trac.ffmpeg.org/ticket/4888#comment:1>
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