[FFmpeg-trac] #4565(avformat:new): MP2 in AVI (possibly) wrong frame_size/blkalign

[FFmpeg]

#4565: MP2 in AVI (possibly) wrong frame_size/blkalign
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             Reporter:  darkyp       |                     Type:  defect
               Status:  new          |                 Priority:  important
            Component:  avformat     |                  Version:
             Keywords:               |  unspecified
  wav,header,mp2                     |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |
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 The background: I'm transcoding DVB MPEG2 Video stream on the Raspberry
 platform to H.264 and the audio is left as is (various types of MP2 audio)
 then both streams are muxed in the AVI container using libavformat.

 The files play fine in most players, however some will play the audio
 stutteringly. VirtualDubMod 1.5.10.1 will complain about audio being VBR
 though it is CBR. If I manually hexedit the AVI and just fix the header
 with the proper values the files will play fine and VDub will not produce
 the warning.

 I looked in the source and I think this could be a problem with
 ff_put_wav_header or a combination with av_get_audio_frame_duration. For
 MP2 audio streams blkalign = frame_size = 1152 (hard coded) while I think
 if the encoder has reported block_align ff_put_wav_header might use it for
 MP2 audio.

 Am I wrong in assuming that the wav header block align should be different
 for the following types of MP2 audio:

 Bitrate: 64000, Sample rate: 48000, Channels: 1 Frame size: 192
 Bitrate: 160000, Sample rate: 48000, Channels: 2 Frame size: 480
 Bitrate: 192000, Sample rate: 48000, Channels: 2 Frame size: 576

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Ticket URL: <https://trac.ffmpeg.org/ticket/4565>
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