[FFmpeg-trac] #2865(avformat:new): Front Center, Downmix Left, and Downmix Right unlabelled in QTPlayer

FFmpeg trac at avcodec.org
Thu Aug 22 03:03:10 CEST 2013

#2865: Front Center, Downmix Left, and Downmix Right unlabelled in QTPlayer
             Reporter:  cjplay93     |                    Owner:
                 Type:  enhancement  |                   Status:  new
             Priority:  wish         |                Component:  avformat
              Version:  git-master   |               Resolution:
             Keywords:  chan         |               Blocked By:
             Blocking:               |  Reproduced by developer:  0
Analyzed by developer:  0            |

Comment (by cjplay93):

 Replying to [comment:3 cehoyos]:

 > I really understand that, the problem is that DL and DR were never
 supported when writing the chan atom, adding support is relatively easy
 for caf and aiff (which does not help you) but less easy for mov (if used
 to be identical for mov and the other containers but was deliberately
 broken at some point, it will be necessary to test if there is a hidden
 feature in the brokenness that I so far didn't see or if the change can
 simply be reverted).

 The "caf" and "aiff" is a point I'd not differentiated.  I simply want
 24-bit, 48khz LE PCM inside the MOV file.  If you feel using a different
 audio format within the Quicktime output is more viable and/or simpler for
 you, then by all means I will gladly change my command to match that.
 What would your recommendation be there?

 > Concerning FC vs "mono": FFmpeg cannot discern between them (mono and
 center are the same in wav), are you only worried because QuickTime does
 not show what you expect or is the output file effectively broken if you
 produce six instead of eight channels?
 Yes, I just need QTPlayer to show the correct values, thus validating the
 output for Apple's usage.
 > > Anyway, the attached file is almost the same asset, but now with
 QTPlayer's labelling included.
 > This is extremely useful, thank you!
 > > You'll see in QTPlayer's movie inspector as well when all 8 tracks are
 turned on in Movie Properties.  That's another weird thing about the LibAV
 output is that the tracks are "turned off" upon output from FFMPEG.
 > I still believe that the typical use-case is to mux several languages
 into one mov file and you don't want them to play simultaneously. But what
 you ask is an often requested feature, help on this is welcome, initial
 tests showed that we (or at least I) don't know how exactly to enable all
 tracks. (But you could test older versions of FFmpeg.)

 Exactly what help is needed?  Programmatic or simple decisive choice?  I
 actually agree on that with your typical use case.  I have actually tried
 turning on those tracks in QTPlayer and they fail to stay on.  Even on a
 Mac and saving a new file.  Strange...  Anyway, I will help how I can.  If
 you need research into atom states/occupancies/settings, I can help there
 as I've gotten to know Atombox a bit.

Ticket URL: <https://ffmpeg.org/trac/ffmpeg/ticket/2865#comment:4>
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