[FFmpeg-trac] #5732(avcodec:new): Display corruption on very high-bitrate H.264 files
FFmpeg
trac at avcodec.org
Sun Jul 24 14:31:03 EEST 2016
#5732: Display corruption on very high-bitrate H.264 files
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Reporter: Sesse | Type: defect
Status: new | Priority: normal
Component: avcodec | Version: git-master
Keywords: | Blocked By:
Blocking: | Reproduced by developer: 0
Analyzed by developer: 0 |
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Hi,
I've discovered what I believe is a bug in the H.264 decoder of
libavcodec. It concerns the following file, where the video is encoded
using Intel Quick Sync Video (on a Haswell, via VA-API) at constant
quantizer:
http://storage.sesse.net/through-the-cracks.mp4
Unfortunately, the file is very big (~5.1GB), and attempts to cut it using
ffmpeg(1) resulted in something VLC wouldn't play, so I've left it alone
save for remuxing (it was originally in NUT) and audio reencoding.
The corruption happens around 13:50, in the right-hand side of the
picture. You can see it by decoding using ffmpeg(1):
{{{
ffmpeg -ss 13:50 -i /srv/storage.sesse.net/through-the-cracks.mp4 -vframes
50 out-%03d.png
}}}
and then looking at out-*.png. The errors persist from out-001.png to
out-019.png; they disappear at out-020.png (perhaps new keyframe?) and
come back at out-045.png. It looks like some kind of overflow to me,
probably due to the extreme bitrate chosen (around 170 Mbit/sec; this
content is super-hard to encode!).
The file plays perfectly in VLC if and only if I enable VA-API hardware
acceleration, so that it's decoded in hardware instead of by libavcodec's
H.264 decoder.
--
Ticket URL: <https://trac.ffmpeg.org/ticket/5732>
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