[FFmpeg-trac] #5936(avcodec:new): Purple haze in mpeg4 decoding

[FFmpeg]

#5936: Purple haze in mpeg4 decoding
---------------------------------+----------------------------------
             Reporter:  te36     |                     Type:  defect
               Status:  new      |                 Priority:  normal
            Component:  avcodec  |                  Version:  2.3.6
             Keywords:           |               Blocked By:
             Blocking:           |  Reproduced by developer:  0
Analyzed by developer:  0        |
---------------------------------+----------------------------------
 Summary:

 I have ca. 3 TB/10 years of free-TV recordings created with (older
 versions) of Mencoder (aka: ffmpeg). These play back fine with older
 versions of XBMC/VLC (decoded by ffmpeg/libavcodec / mpeg4), but since
 XBMC 13.1 and VLC 2.2, ffmpeg produces purple haze that is creeping in
 from the side of the screen when the video is panning.

 How to reproduce:

 ffplay purple-haze-bug.avi
 (on upload.ffmpeg.org or ticket)
   Duration: 00:00:16.63, start: 0.000000, bitrate: 1454 kb/s
     Stream #0:0: Video: mpeg4 (Simple Profile) (FMP4 / 0x34504D46),
 yuv420p, 720x576 [SAR 64:45 DAR 16:9], 1383 kb/s, 25 fps, 25 tbr, 25 tbn,
 25 tbc
 ...

 Latest working versions:
    <=ffmpeg 2.2.x (tested 2.2.16, 2.1, 2.0)
    ffmpeg
      tag 03bb99ae1a99fa315621308b885a8fc70702c9bc Jun 1, 2014 master
 branch
    ffplay version N-63655-g03bb99a Copyright (c) 2003-2014 the FFmpeg
 developers
      built on Nov  9 2016 14:43:54 with gcc 4.9.3 (Gentoo 4.9.3 p1.5,
 pie-0.6.4)
      configuration:
      libavutil      52. 88.100 / 52. 88.100
      libavcodec     55. 66.100 / 55. 66.100
      libavformat    55. 42.100 / 55. 42.100
      libavdevice    55. 13.101 / 55. 13.101
      libavfilter     4.  5.100 /  4.  5.100
      libswscale      2.  6.100 /  2.  6.100
      libswresample   0. 19.100 /  0. 19.100

 First purple haze version:
    >=ffmpeg 2.3.0 (tested 2.3 and later).
    ffmpeg
      tag 9236f7b5a23b4907f7b2bf6346ecd88e6d76f1e0 Jun 14, 2014 master
 branch
    ffplay version N-63957-g9236f7b Copyright (c) 2003-2014 the FFmpeg
 developers
       built on Nov  9 2016 14:50:33 with gcc 4.9.3 (Gentoo 4.9.3 p1.5,
 pie-0.6.4)
       configuration:
       libavutil      52. 89.100 / 52. 89.100
       libavcodec     55. 66.101 / 55. 66.101
       libavformat    55. 43.100 / 55. 43.100
       libavdevice    55. 13.101 / 55. 13.101
       libavfilter     4.  8.100 /  4.  8.100
       libswscale      2.  6.100 /  2.  6.100
       libswresample   0. 19.100 /  0. 19.100

 I am only _guessing_ this is an avcodec issue because it looks very
 much related to mpeg4 decoding of blocks panning in from "offscreen".

 git diff 03bb99ae1a99fa315621308b885a8fc70702c9bc
 9236f7b5a23b4907f7b2bf6346ecd88e6d76f1e0
 produce 700k diff and i can not figure out what a likely cause is ;-(

 I am sure there is some problem in mencoder, but i hope that ffmpeg will
 continue to try to decode as good as possible even potentially buggy
 videos as it did in the past. Especially videos encoded with (older
 versions of) ffmpeg.

 The example video is encoded with MEncoder 1.0rc1-4.1.2, but the problem
 exists with at least up to Mencoder-1.1(which uses 0.10.2.git).

 Sorry for reporting so late, did not have the time earlier and was hoping
 somebody else would find this too.

--
Ticket URL: <https://trac.ffmpeg.org/ticket/5936>
FFmpeg <https://ffmpeg.org>
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