[FFmpeg-trac] #5225(avcodec:new): AC3 decoder fault after long running transcoding

[FFmpeg]

#5225: AC3 decoder fault after long running transcoding
------------------------------------+--------------------------------------
             Reporter:  DeHackEd    |                     Type:  defect
               Status:  new         |                 Priority:  normal
            Component:  avcodec     |                  Version:  git-master
             Keywords:  ac3 ac3dec  |               Blocked By:
             Blocking:              |  Reproduced by developer:  0
Analyzed by developer:  0           |
------------------------------------+--------------------------------------
 Summary of the bug:
 I am running a video transcoder on a TV channel (multicast source) that
 runs pretty much 24/7. After a long period of time (eg: days or weeks) the
 AC3 decoder will hit some kind of error (I do not have the error at this
 time) and enter a permanent fault state. In this state the audio decoded
 is simply a single long tone even though the source material has recovered
 from whatever error it encountered in the first place.

 While in this state ffmpeg produces the same error non-stop. The output
 AAC audio has decoder errors as well, more on that later. I have seen two
 different errors so far:

 [ac3 @ 0x334b7e0] new coupling strategy must be present in block 0
 [ac3 @ 0x334b7e0] error decoding the audio block
 [ac3 @ 0x334b7e0] new coupling strategy must be present in block 0
 [ac3 @ 0x334b7e0] error decoding the audio block

 OR

 [ac3 @ 0x24b9360] exponent -1 is out-of-range
 [ac3 @ 0x24b9360] error decoding the audio block
 [ac3 @ 0x24b9360] exponent -1 is out-of-range
 [ac3 @ 0x24b9360] error decoding the audio block

 (the exponent number does vary)

 The output file produces errors from the AAC encoded audio:

 [ffmpeg/audio] aac: element type mismatch 1 != 0
 [ffmpeg/audio] aac: element type mismatch 1 != 0
 [ffmpeg/audio] aac: element type mismatch 1 != 0
 [ffmpeg/audio] aac: element type mismatch 1 != 0
 [ffmpeg/audio] aac: element type mismatch 1 != 0
 [ffmpeg/audio] aac: element type mismatch 1 != 0


 Restarting ffmpeg will return it to normal operation consistently.

 ffprobe of the source stream:

 Input #0, mpegts, from 'udp://239.x.y.z:1234':
   Duration: N/A, start: 18332.569233, bitrate: N/A
   Program 1521
     Stream #0:0[0x81e](eng): Audio: ac3 (AC-3 / 0x332D4341), 48000 Hz,
 5.1(side), fltp, 384 kb/s
     Stream #0:1[0x81f]: Video: h264 (High) ([27][0][0][0] / 0x001B),
 yuv420p, 1920x1080 [SAR 1:1 DAR 16:9], Closed Captions, 29.97 fps, 29.97
 tbr, 90k tbn, 59.94 tbc



 How to reproduce:
 {{{
 % ffmpeg -nostdin -loglevel warning -i udp://239.x.y.z:1234 -c:a
 libfdk_aac -ac 2 -c:v libx264 -vf yadif,scale=w=640:h=360 -preset
 superfast -profile:a aac_he -b:a 128k -copytb 1 -vsync 2 [other libx264
 options and non-audio settings] -threads 4 -f hls
 /var/www/html/channel.m3u8

 [output with -loglevel omitted for version information]

 ffmpeg version N-78248-gf781bf3 Copyright (c) 2000-2016 the FFmpeg
 developers
   built with gcc 5.3.0 (Gentoo 5.3.0 p1.0, pie-0.6.5)
   configuration: --extra-cflags='-I/home/build/x264 -march=sandybridge
 -mtune=sandybridge' --extra-ldflags='-L/home/build/x264 -ldl -static'
 --enable-libx264 --enable-libfdk_aac --enable-gpl --enable-nonfree
   libavutil      55. 16.101 / 55. 16.101
   libavcodec     57. 24.101 / 57. 24.101
   libavformat    57. 23.101 / 57. 23.101
   libavdevice    57.  0.101 / 57.  0.101
   libavfilter     6. 28.100 /  6. 28.100
   libswscale      4.  0.100 /  4.  0.100
   libswresample   2.  0.101 /  2.  0.101
   libpostproc    54.  0.100 / 54.  0.100

 }}}

 I will try to capture the error logs when it happens, but I cannot say how
 long that will take.

--
Ticket URL: <https://trac.ffmpeg.org/ticket/5225>
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