[libav-bugs] [Bug 225] New: AC3 decoder doesn't grok channel layout for MOV/MP4 sources

bugzilla-daemon at aruru.libav.org bugzilla-daemon at aruru.libav.org
Sun Feb 12 18:02:53 CET 2012


http://bugzilla.libav.org/show_bug.cgi?id=225

           Summary: AC3 decoder doesn't grok channel layout for MOV/MP4
                    sources
           Product: Libav
           Version: git HEAD
          Platform: X86
        OS/Version: Mac OS
            Status: NEW
          Severity: minor
          Priority: Normal
         Component: libavcodec
        AssignedTo: bugzilla at libav.org
        ReportedBy: tdskywalker at gmail.com


If I encode a file to AC3-in-MP4 with avconv (or aother tool like e.g.
HandBrake), then avconv is unable to detect the channel layout for that AC3
track:

-------------------------------
avconv -i SpeakerID-5point1.mka -c:a ac3 -b:a 640k SpeakerID-5point1.mp4

avconv version v0.8-439-g3e23bad, Copyright (c) 2000-2012 the Libav developers
  built on Feb 12 2012 17:53:23 with llvm_gcc 4.2.1 (Based on Apple Inc. build
5658) (LLVM build 2336.1.00)
[matroska,webm @ 0x7fd94201ae00] Estimating duration from bitrate, this may be
inaccurate
Input #0, matroska,webm, from 'SpeakerID-5point1.mka':
  Duration: 00:00:37.04, start: 0.000000, bitrate: N/A
    Stream #0.0(eng): Audio: truehd, 48000 Hz, 5.1, s32
Incompatible sample format 's32' for codec 'ac3', auto-selecting format 'flt'
Output #0, mp4, to 'SpeakerID-5point1.mp4':
  Metadata:
    encoder         : Lavf54.0.0
    Stream #0.0(eng): Audio: ac3, 48000 Hz, 5.1, flt, 640 kb/s
Stream mapping:
  Stream #0:0 -> #0:0 (truehd -> ac3)
Press ctrl-c to stop encoding
End of stream indicated.54 bitrate= 640.0kbits/s    
size=    2900kB time=37.06 bitrate= 641.1kbits/s    
video:0kB audio:2895kB global headers:0kB muxing overhead 0.179289%
-------------------------------
avconv -i SpeakerID-5point1.mp4

avconv version v0.8-439-g3e23bad, Copyright (c) 2000-2012 the Libav developers
  built on Feb 12 2012 17:53:23 with llvm_gcc 4.2.1 (Based on Apple Inc. build
5658) (LLVM build 2336.1.00)
Input #0, mov,mp4,m4a,3gp,3g2,mj2, from 'SpeakerID-5point1.mp4':
  Metadata:
    major_brand     : isom
    minor_version   : 512
    compatible_brands: isomiso2mp41
    encoder         : Lavf54.0.0
  Duration: 00:00:37.05, start: 0.000000, bitrate: 641 kb/s
    Stream #0.0(eng): Audio: ac3, 48000 Hz, 6 channels, s16, 640 kb/s
At least one output file must be specified
-------------------------------

There is no such issue when the container format is MKV, however:

-------------------------------
avconv -i SpeakerID-5point1.mka -c:a ac3 -b:a 640k SpeakerID-5point1.mkv

avconv version v0.8-439-g3e23bad, Copyright (c) 2000-2012 the Libav developers
  built on Feb 12 2012 17:53:23 with llvm_gcc 4.2.1 (Based on Apple Inc. build
5658) (LLVM build 2336.1.00)
[matroska,webm @ 0x7ff6a301ae00] Estimating duration from bitrate, this may be
inaccurate
Input #0, matroska,webm, from 'SpeakerID-5point1.mka':
  Duration: 00:00:37.04, start: 0.000000, bitrate: N/A
    Stream #0.0(eng): Audio: truehd, 48000 Hz, 5.1, s32
Incompatible sample format 's32' for codec 'ac3', auto-selecting format 'flt'
Output #0, matroska, to 'SpeakerID-5point1.mkv':
  Metadata:
    encoder         : Lavf54.0.0
    Stream #0.0(eng): Audio: ac3, 48000 Hz, 5.1, flt, 640 kb/s
Stream mapping:
  Stream #0:0 -> #0:0 (truehd -> ac3)
Press ctrl-c to stop encoding
End of stream indicated.11 bitrate= 639.0kbits/s    
size=    2904kB time=37.06 bitrate= 641.9kbits/s    
video:0kB audio:2895kB global headers:0kB muxing overhead 0.296173%
-------------------------------
avconv -i SpeakerID-5point1.mkv

avconv version v0.8-439-g3e23bad, Copyright (c) 2000-2012 the Libav developers
  built on Feb 12 2012 17:53:23 with llvm_gcc 4.2.1 (Based on Apple Inc. build
5658) (LLVM build 2336.1.00)
[matroska,webm @ 0x7fed9201ae00] Estimating duration from bitrate, this may be
inaccurate
Input #0, matroska,webm, from 'SpeakerID-5point1.mkv':
  Metadata:
    ENCODER         : Lavf54.0.0
  Duration: 00:00:37.05, start: 0.000000, bitrate: 640 kb/s
    Stream #0.0(eng): Audio: ac3, 48000 Hz, 5.1, s16, 640 kb/s (default)
At least one output file must be specified
-------------------------------

Not sure whether this is a libavcodec or libavformat issue, TBH.

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