Decoding artifacts with ffvp9

[kagami]

Certain VP9 bit-streams show corruption when decoding with ffvp9. Decoding with libvpx-vp9 seem to be fine.

How to reproduce:

ffplay ffvp9_corruption.webm
[Corruption is visible in certain frames, starting with 4th second]

ffplay ffvp9_corruption.webm -vcodec libvpx-vp9
[No corruption here]

ffmpeg version N-72436-g403940d Copyright (c) 2000-2015 the FFmpeg developers
built with gcc 4.8.4 (Gentoo 4.8.4 p1.4, pie-0.6.1)

libvpx version v1.4.0-397-g26ab314

Sorry if it's a known bug but I've searched in bugtracker and all similar issues are closed. I also tried to pass "-threads 1" option to ffplay but it didn't help.

[Carl Eugen Hoyos]

For future tickets: Please always test ffmpeg (the application) and please provide a command line that allows to reproduce the issue together with the complete, uncut console output.

$ ffmpeg -i ffvp9_corruption.webm -qscale 2 out.avi
ffmpeg version N-72446-gdebf4d6 Copyright (c) 2000-2015 the FFmpeg developers
  built with gcc 4.7 (SUSE Linux)
  configuration: --enable-gpl
  libavutil      54. 26.100 / 54. 26.100
  libavcodec     56. 41.100 / 56. 41.100
  libavformat    56. 34.100 / 56. 34.100
  libavdevice    56.  4.100 / 56.  4.100
  libavfilter     5. 16.101 /  5. 16.101
  libswscale      3.  1.101 /  3.  1.101
  libswresample   1.  1.100 /  1.  1.100
  libpostproc    53.  3.100 / 53.  3.100
Input #0, matroska,webm, from 'ffvp9_corruption.webm':
  Metadata:
    title           : A Salty Stick-h9tJ57Qao_Y
    encoder         : Lavf56.33.101
  Duration: 00:00:08.01, start: 0.006000, bitrate: 216 kb/s
    Stream #0:0: Video: vp9 (Profile 0), yuv420p(tv), 640x360, SAR 1:1 DAR 16:9, 29.97 fps, 29.97 tbr, 1k tbn, 1k tbc (default)
    Stream #0:1: Audio: opus, 48000 Hz, stereo, fltp (default)
Please use -q:a or -q:v, -qscale is ambiguous
Output #0, avi, to 'out.avi':
  Metadata:
    INAM            : A Salty Stick-h9tJ57Qao_Y
    ISFT            : Lavf56.34.100
    Stream #0:0: Video: mpeg4 (FMP4 / 0x34504D46), yuv420p, 640x360 [SAR 1:1 DAR 16:9], q=2-31, 200 kb/s, 29.97 fps, 29.97 tbn, 29.97 tbc (default)
    Metadata:
      encoder         : Lavc56.41.100 mpeg4
    Stream #0:1: Audio: ac3 ([0] [0][0] / 0x2000), 48000 Hz, stereo, fltp, 192 kb/s (default)
    Metadata:
      encoder         : Lavc56.41.100 ac3
Stream mapping:
  Stream #0:0 -> #0:0 (vp9 (native) -> mpeg4 (native))
  Stream #0:1 -> #0:1 (opus (native) -> ac3 (native))
Press [q] to stop, [?] for help
frame=  215 fps=0.0 q=2.0 Lsize=    1794kB time=00:00:08.00 bitrate=1835.3kbits/s
video:1585kB audio:188kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 1.205822%

[Carl Eugen Hoyos]

Fixed by Ronald in 138581c4 - thank you for the report!