[FFmpeg-user] more sound madness

[Ted Park]

Hi,

> command below seems simple enough, and works, except that the last two audio channels (those coming from the second input) are muted in the metadata.
> (Meaning, the sound data is there, but QT atom has flagged them as ‘inactive’.)

> What is the secret handshake to remap / patch / reroute / matrix / add / omit the sound channels of multiple input files to one new file?
> (I can’t imagine I’m the only one doing this kind of stuff. And at this point I really don’t care if all the channels end up in one track, or in multiple, just to have them play in QT / Premiere and alike.)
The reverse of “inactive” is “default” iirc, so they aren’t in alternate groups. The mov muxer seems to do that by default for me though.

> bouke at Boukes-iMac ~ % /Applications/ffmpeg  -i /Volumes/Data/test/C0092.MP4 -i /Volumes/Data/test/068.WAV -map 0:0 -map 0:a -map_channel 0.1.1:0.1  -map 1:a -map_channel 1.0.8:0.2 -map 1:a -map_channel 1.0.9:0.3  -c:a pcm_s24le -c:v copy -shortest /Volumes/Data/test/last2muted.mov -y

I think it would help to do the channel mapping first just to separate the options
% ffmpeg -i /Volumes/Data/test/C0092.MP4 -i /Volumes/Data/test/068.WAV -map 0:1 -map 1:0 -map 1:0 -map_channel 0.1.1:0.1 -map_channel 1.0.8:0.2 -map_channel 1.0.9:0.3 -c:a pcm_s24le -map 0:0 -c:v copy -shortest /Volumes/Data/test/last2muted.mov -y

> Stream mapping:
>  Stream #0:0 -> #0:0 (copy)
>  Stream #0:1 -> #0:1 (pcm_s16be (native) -> pcm_s24le (native))
>  Stream #1:0 -> #0:2 (pcm_s24le (native) -> pcm_s24le (native))
>  Stream #1:0 -> #0:3 (pcm_s24le (native) -> pcm_s24le (native))
> Press [q] to stop, [?] for help
> -map_channel is forwarded to lavfi similarly to -af pan=0x4|c0=c1.
> [pan @ 0x7fb020e00a00] Pure channel mapping detected: 1
> -map_channel is forwarded to lavfi similarly to -af pan=0x4|c0=c8.
> [pan @ 0x7fb020d04740] Pure channel mapping detected: 8
> -map_channel is forwarded to lavfi similarly to -af pan=0x4|c0=c9.
> [pan @ 0x7fb020f1d200] Pure channel mapping detected: 9

It shouldn’t matter if audio channels come before others. Also I am kind of suspicious of this, I don’t know if using 4 channels is normal in this situation, or how the extra channels are mapped wrt gain. Exploding the multitrack recording into separate wave files first might make things simpler.
Regards,
Ted Park