[FFmpeg-user] Tagging audio channels

Tim Nicholson nichot20 at yahoo.com
Mon Jul 16 09:13:50 CEST 2012

On 13/07/12 17:21, Carl Eugen Hoyos wrote:
> Tim Nicholson <nichot20 <at> yahoo.com> writes:
>> 4ch 1 stream version L/R L/R:-
>> http://www.datafilehost.com/download-ae6a91cd.html
> Thank you for the sample!
> (I wonder how the application is supposed to know which of 
> the two "chan" atoms should be used, the one that says 4.0 
> or the one that says LRLR? But I did not look carefully.)

I think the 4.0 comes from ffmpeg after the initial stream copy of mono
tracks, then the L/R settings, is added by quicktime which doesn't allow
adjustment of the 4.0 bit.

As it happens I find that I also need to set the track names
(trak->udta->name atom) so I think I am going to have to knock up an
atom smasher to post process the files and tweak the atoms as required...

> FFmpeg currently does not even support reading the channel 
> layout, and unfortunately, it is incompatible with the 
> internal representation.

Expecting ffmpeg to support the morass of qt atoms is somewhat
unrealistic, but I wanted to check there was no hidden feature I could
use before diving in..

> Stream-copying should be possible though, afair, I once 
> posted a patch that may work.

Interesting I will have a look.

> Carl Eugen
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