[FFmpeg-trac] #7410(avcodec:new): mpeg4 decoding regression with multi-threading

[FFmpeg]

#7410: mpeg4 decoding regression with multi-threading
-------------------------------------+-------------------------------------
               Reporter:  cehoyos    |                  Owner:
                   Type:  defect     |                 Status:  new
               Priority:  important  |              Component:  avcodec
                Version:  git-       |               Keywords:  mpeg4
  master                             |  regression handbrake
             Blocked By:             |               Blocking:
Reproduced by developer:  0          |  Analyzed by developer:  0
-------------------------------------+-------------------------------------
 https://github.com/HandBrake/HandBrake/issues/1563
 !HandBrake user Gioni1 reported an mpeg4 decoding regression that
 manifests itself with threads >= 4, regression since d375c104, user-
 visible since 4478e9d8.
 {{{
 $ ffmpeg -threads 4 -i
 Austin.e.Ally.1x11.Compositori.e.stelle.marine_cut.avi -ss 5 -t 5 -qscale
 2 out.avi
 ffmpeg version N-91807-ga77c2df Copyright (c) 2000-2018 the FFmpeg
 developers
   built with gcc 6.4.0 (GCC)
   configuration: --enable-gpl --enable-gnutls --enable-libxml2
   libavutil      56. 19.100 / 56. 19.100
   libavcodec     58. 27.101 / 58. 27.101
   libavformat    58. 18.100 / 58. 18.100
   libavdevice    58.  4.101 / 58.  4.101
   libavfilter     7. 26.100 /  7. 26.100
   libswscale      5.  2.100 /  5.  2.100
   libswresample   3.  2.100 /  3.  2.100
   libpostproc    55.  2.100 / 55.  2.100
 [mpeg4 @ 0x40c3c80] Failed to parse extradata
 Input #0, avi, from
 'Austin.e.Ally.1x11.Compositori.e.stelle.marine_cut.avi':
   Duration: 00:00:12.12, start: 0.000000, bitrate: 1689 kb/s
     Stream #0:0: Video: mpeg4 (Simple Profile) (XVID / 0x44495658),
 yuv420p, 624x352 [SAR 1:1 DAR 39:22], 25 fps, 25 tbr, 25 tbn, 25 tbc
     Stream #0:1: Audio: mp3 (U[0][0][0] / 0x0055), 44100 Hz, stereo, fltp,
 320 kb/s
 Please use -q:a or -q:v, -qscale is ambiguous
 Stream mapping:
   Stream #0:0 -> #0:0 (mpeg4 (native) -> mpeg4 (native))
   Stream #0:1 -> #0:1 (mp3 (mp3float) -> ac3 (native))
 Press [q] to stop, [?] for help
 Output #0, avi, to 'out.avi':
   Metadata:
     ISFT            : Lavf58.18.100
     Stream #0:0: Video: mpeg4 (FMP4 / 0x34504D46), yuv420p, 624x352 [SAR
 1:1 DAR 39:22], q=2-31, 200 kb/s, 25 fps, 25 tbn, 25 tbc
     Metadata:
       encoder         : Lavc58.27.101 mpeg4
     Side data:
       cpb: bitrate max/min/avg: 0/0/200000 buffer size: 0 vbv_delay: -1
     Stream #0:1: Audio: ac3 ([0] [0][0] / 0x2000), 44100 Hz, stereo, fltp,
 192 kb/s
     Metadata:
       encoder         : Lavc58.27.101 ac3
 [NULL @ 0x40c3c80] Ignoring multiple VOL headers
 [mpeg4 @ 0x40eb100] Ignoring multiple VOL headers
 frame=  125 fps=0.0 q=2.0 Lsize=    2099kB time=00:00:05.01
 bitrate=3427.7kbits/s speed=34.6x
 video:1965kB audio:118kB subtitle:0kB other streams:0kB global headers:0kB
 muxing overhead: 0.774171%
 }}}
 The output file shows massive artefacts, works fine with `-threads 1`.

--
Ticket URL: <https://trac.ffmpeg.org/ticket/7410>
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