[FFmpeg-trac] #6641(ffmpeg:new): Severe artifacts when decoding WMV / WMV3 (Windows Media Video 9) / VC-1 videos

[FFmpeg]

#6641: Severe artifacts when decoding WMV / WMV3 (Windows Media Video 9) / VC-1
videos
----------------------------------+---------------------------------------
             Reporter:  batou     |                     Type:  defect
               Status:  new       |                 Priority:  normal
            Component:  ffmpeg    |                  Version:  unspecified
             Keywords:  wmv vc-1  |               Blocked By:
             Blocking:            |  Reproduced by developer:  0
Analyzed by developer:  0         |
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 Summary of the bug:
 I've noticed that new versions of mpv video player cannot play WMV videos
 reliably anymore. There are always visual artifacts every minute or so
 (keyframes maybe?).

 Today I had some time and decided to investigate. Artifacting only occurs
 with VC-1 WMV videos (not older codecs). I've asked for help from mpv team
 but they sent me here since it's not an mpv issue.

 Here's an example of artifacts: Left is ffmpeg-based player (mpv) and
 right is a player that doesn't use ffmpeg:

 https://i.imgur.com/jtHTe34.jpg

 Usually, it's not as severe as this example but this bug makes WMV videos
 completely unwatchable in mpv.

 Sample video:
 http://samples.mplayerhq.hu/V-codecs/WMV9/halo2_wmp9_WMV3+audio0x162.wmv


 {{{
 $ mpv --version
 mpv 0.26.0-237-g5771f7abf4 (C) 2000-2017 mpv/MPlayer/mplayer2 projects
  built on Linux x86_64
 ffmpeg library versions:
    libavutil       55.74.100
    libavcodec      57.105.100
    libavformat     57.81.100
    libswscale      4.7.103
    libavfilter     6.102.100
    libswresample   2.8.100
 ffmpeg version: N-87204-gd8bc198d09

 }}}

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Ticket URL: <https://trac.ffmpeg.org/ticket/6641>
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