Multitrack audio mapping

There are quite a few use cases which would benefit from this feature.

That mean I would like have english audio to first sound card, and for example czech audio would be at the second card. One way for that is to display each Audio device as tab in Extended settings -> Audio effects(or mapper). Show additional map options for each device based on speaker config:

Mix both stereo channels to stereo

That is the combining of the left and right channels into one mono channel. In other words, the left channel is fed to both left and right; and the right fed to both left and right.

2 × mono → stereo

MPEG4 AVC part10 (AVC1)YUV422(pc, 0bt709)_10bit__4xMono-PCM24bit

2 × stereo → stereo
6 × mono → 5.1
3 × stereo → 5.1

already used by folks across the pond for recorded files

-filter_complex '[0:1][0:2][0:3]amerge=inputs=3,pan=5.1|FL=c0|FR=c1|FC=c2|LFE=c3|BL=c4|BR=c5' -c:a eac3

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