audio-buffer-remix   

Upmix or downmix channels in AudioBuffer or AudioBufferList by the following table:

| Input Channels | Output Channels | Rules |
|---|---|---|
| 1 (Mono) | 2 (Stereo) | output[0] = input[0]
output[1] = input[0] |
| 1 (Mono) | 4 (Quad) | output[0] = input[0]
output[1] = input[0]
output[2] = 0
output[3] = 0 |
| 1 (Mono) | 6 (5.1) | output[0] = 0
output[1] = 0
output[2] = input[0]
output[3] = 0
output[4] = 0
output[5] = 0 |
| 2 (Stereo) | 1 (Mono) | output[0] = 0.5 * (input[0] + input[1]) |
| 2 (Stereo) | 4 (Quad) | output[0] = input[0]
output[1] = input[1]
output[2] = 0
output[3] = 0 |
| 2 (Stereo) | 6 (5.1) | output[0] = input[0]
output[1] = input[1]
output[2] = 0
output[3] = 0
output[4] = 0
output[5] = 0 |
| 4 (Quad) | 1 (Mono) | output[0] = 0.25 * (input[0] + input[1] + input[2] + input[3]) |
| 4 (Quad) | 2 (Stereo) | output[0] = 0.5 (input[0] + input[2])
output[1] = 0.5 (input[1] + input[3]) |
| 4 (Quad) | 6 (5.1) | output[0] = input[0]
output[1] = input[1]
output[2] = 0
output[3] = 0
output[4] = input[2]
output[5] = input[3] |
| 6 (5.1) | 1 (Mono) | output[0] = 0.7071 (input[0] + input[1]) + input[2] + 0.5 (input[2] + input[3]) |
| 6 (5.1) | 2 (Stereo) | output[0] = input[0] + 0.7071 (input[2] + input[4])
output[1] = input[1] + 0.7071 (input[2] + input[5]) |
| 6 (5.1) | 4 (Quad) | output[0] = input[0] + 0.7071 input[2]
output[1] = input[1] + 0.7071 input[2]
output[2] = input[4]
output[3] = input[5] |
| n | m | output[n] = input[n] |

Usage


``js
const AudioBuffer = require('audio-buffer')
const remix = require('audio-buffer-remix')

let stereoBuffer = new AudioBuffer(2, 1024)

quadBuffer = remix(stereoBuffer, 4)
`

API

$3

Take source audio buffer and upmix/downmix its channels to dest with the indicated number of channels. options may provide audio context or interpretation type: 'discrete' or 'speaker', see channelInterpretation MDN reference.

Alternatively pass map − a list or object with channel mapping. Numbers as values map channels directly by numbers, null drops channel from output and function with (destChannelData, source) => {} signature expects to fill destChannelData array.

`js
const util = require('audio-buffer-utils')

let source = util.noise(util.create(1024, 2))

let dest = remix(source, {
//0 output channel - take first input channel data
0: 1,

//1 output channel - mute the data
1: null,

//2 output channel - mix 0 + 1 channels
2: (destChannel, source) => {
let left = source.getChannelData(0)
let right = source.getChannelData(1)
for (let i = 0; i < out.length; i++) {
destChannel[i] = left[i] .5 + right[i] .5
}
}
})

dest.numberOfChannels // 3
``

See also

* audio — high-level class for audio
* audio-buffer — audio buffer class for nodejs and browser
* audio-buffer-list — audio buffer class for nodejs and browser
* audio-buffer-utils — toolset for audio buffers