[FFmpeg-user] Specify FC instead of mono‏

Moritz Barsnick barsnick at gmx.net
Tue Oct 27 17:42:35 CET 2015

On Tue, Oct 27, 2015 at 14:17:45 +0000, Kieran O Leary wrote:
> Perhaps mediatrace would be worth a shot? https://mediaarea.net/mediatrace/

Ah, I didn't realize mediainfo could spit out details about the atoms.
It can indeed...

If the samples in the mentioned ticket

notably SD_IVTC_8channel_ProResHQ_test.mov (from ffmpeg, incorrect)
and     SD_IVTC_8channel_ProResHQ_test_withT3.7.8_labels.mov (from QT Player, correct)

expose exactly the same behavior, I can only say this with regards to
the difference of the files (ignoring the developers' analysis of
whether this can be fixed):

I believe the audio channels in question differ as such:
The "C" center channel:

00000D38        Channels (24 bytes)
00000D38         Header (8 bytes)
00000D38          Size:                             24 (0x00000018)
00000D3C          Name:                             chan
00000D40         Version:                           0 (0x00)
00000D41         Flags:                             0 (0x000000)
00000D44         ChannelLayoutTag:                  6553601 (0x00640001)
00000D48         ChannelBitmap:                     0 (0x00000000)
00000D4C         NumberChannelDescriptions:         0 (0x00000000)


00000D8C        Channels (44 bytes)
00000D8C         Header (8 bytes)
00000D8C          Size:                             44 (0x0000002C)
00000D90          Name:                             chan
00000D94         Version:                           0 (0x00)
00000D95         Flags:                             0 (0x000000)
00000D98         ChannelLayoutTag:                  0 (0x00000000)
00000D9C         ChannelBitmap:                     0 (0x00000000)
00000DA0         NumberChannelDescriptions:         1 (0x00000001)
00000DA4         ChannelLabel:                      3 (0x00000003)
00000DA8         ChannelFlags:                      0 (0x00000000)
00000DAC         Coordinates (0):                   0.000
00000DB0         Coordinates (1):                   0.000
00000DB4         Coordinates (2):                   0.000

Similar for the two other channels: QT seems to use "ChannelLabel" (3
here, 38 and 39 for the two others channels in the sample), which
ffmpeg does not. (Those two are different from your samples anyway,
ffmpeg detects them as DL and DR instead of "downmix".)

I have no idea how to fix this and won't dive into it either. ;-)


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