[Libquicktime-devel] qtinfo vs qtdump multichannel audio info

[Steven S. <sch...@gm...>]

Hi —

It appears that qtinfo’s multichannel audio handing is simplistic and isn’t looking in the correct place for information.

A 4 channel audio file (produced with Quicktime Player)  produces this output from qtinfo:

[mini:x/QuadroPopParty] sms% qtinfo 4.mov
in quicktime_get_chan
Type: Quicktime
  1 audio tracks.
    4 channels, 24 bits, sample rate 48000, length 99918240 samples, compressor lpcm.
    Sample format: 32 bit signed.
    Channel setup: [1]Front Left, [2]Front Right, [0]Unknown, [0]Unknown
    Language: eng
    supported.
  0 video tracks.
  0 text tracks.
[mini:x/QuadroPopParty] sms% qtinfo 4.mov
Type: Quicktime
  1 audio tracks.
    4 channels, 24 bits, sample rate 48000, length 99918240 samples, compressor lpcm.
    Sample format: 32 bit signed.
    Channel setup: Front Left, Front Right, Unknown, Unknown
    Language: eng
    supported.
  0 video tracks.
  0 text tracks.
[mini:x/QuadroPopParty] sms% qtinfo 4.mov
Type: Quicktime
  1 audio tracks.
    4 channels, 24 bits, sample rate 48000, length 99918240 samples, compressor lpcm.
    Sample format: 32 bit signed.
    Channel setup: Front Left, Front Right, Unknown, Unknown
    Language: eng
    supported.
  0 video tracks.
  0 text tracks.

After a morning of puzzling over this and seeing only that multichannel.c is an incomplete subset of chan.c I remembered that qtdump might help.

qtdump says about the stsd atom:

    sample table
     sample description (stsd)
      version 0
      flags 0
      total_entries 1
       format lpcm
       reserved 00 00 00 00 00 00 
       data_reference 1
       version 2
       revision 0
       vendor xxxxx
       channels 4
       sample_size 24
       samplerate                     48000.000000
       formatSpecificFlags:           0000000e
       constBytesPerAudioPacket:      12
       constLPCMFramesPerAudioPacket: 1
       channel description
        version                     0
        flags                       0
        mChannelLayoutTag:          0x00000000 [Use channel decriptions]
        mChannelBitmap:             0x00000000
        mNumberChannelDescriptions: 4
         mChannelLabel[0]: 0x00000001 [Left]
         mChannelFlags[0]: 0x00000000
         mCoordinates[0]: [0.000000 0.000000 0.000000]
         mChannelLabel[1]: 0x00000002 [Right]
         mChannelFlags[1]: 0x00000000
         mCoordinates[1]: [0.000000 0.000000 0.000000]
         mChannelLabel[2]: 0x00000021 [Rear Surround Left]
         mChannelFlags[2]: 0x00000000
         mCoordinates[2]: [0.000000 0.000000 0.000000]
         mChannelLabel[3]: 0x00000022 [Rear Surround Right]
         mChannelFlags[3]: 0x00000000
         mCoordinates[3]: [0.000000 0.000000 0.000000]

Ah ha - so the quicktime file is correct and qtinfo is wrong.

Seems that qtinfo uses the multichannel.c module rather than the quicktime_chan_dump logic of chan.c.

is there a reason multichannel.c is around instead of using the logic in chan.c?