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# Audio Mixer
[](https://circleci.com/gh/mozilla/audio-mixer)
[](https://github.com/mozilla/audio-mixer/actions/workflows/test.yml)
Mixing audio data from any input channel layout to any output channel layout,
in a *matrix-multiplication* form.
```
output channel #1 ▸ │ Silence │ │ 0, 0, 0, 0 │ │ FrontRight │ ◂ input channel #1
output channel #2 ▸ │ FrontRight │ = │ R, C, 0, F │ x │ FrontCenter │ ◂ input channel #2
output channel #3 ▸ │ FrontLeft │ │ 0, C, L, F │ │ FrontLeft │ ◂ input channel #3
▴ ▴ │ LowFrequency │ ◂ input channel #4
┊ ┊ ▴
┊ ┊ ┊
out_audio mixing matrix m in_audio
```
For example, the above means there are 3 output channels and 4 input channels.
The order of output channels is _Silence, FrontRight, and FrontLeft_.
The order of input channels is _FrontRight, FrontCenter, FrontLeft, LowFrequency_.
So the output data in the _channel #2_ will be:
```
Output data of ch #2 (FrontRight) =
R x input channel #1 (FrontRight) +
C x input channel #2 (FrontCenter) +
0 x input channel #3 (FrontLeft) +
F x input channel #4 (LowFrequency)
```
where the _C, F, L, R_ are mixing coefficients.
The _Silence_ channel is a unused channel in the output device,
so its channel data will always be zero.
## License
MPL-2