110 lines
2.7 KiB
JavaScript
110 lines
2.7 KiB
JavaScript
var
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Readable = require('stream').Readable,
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util = require('util'),
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int24 = require('int24'),
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Input = require('./input.js')
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;
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function Mixer(args) {
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Readable.call(this, args);
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if (typeof args === 'undefined') args = {};
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if (args.channels != 1 && args.channels != 2) args.channels = 2;
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if (typeof args.sampleRate === 'number' || args.sampleRate < 1) args.sampleRate = 44100;
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this.buffer = new Buffer(0);
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this.bitDepth = args.bitDepth;
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if (args.bitDepth == 8) {
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this.readSample = this.buffer.readInt8;
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this.writeSample = this.buffer.writeInt8;
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this.sampleByteLength = 1;
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}
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else if (args.bitDepth == 32) {
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this.readSample = this.buffer.readInt32LE;
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this.writeSample = this.buffer.writeInt32LE;
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this.sampleByteLength = 4;
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}
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else if (args.bitDepth == 24) {
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this.readSample = function (offset) {
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return int24.readInt24LE(this.buffer, offset);
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};
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this.writeSample = function (offset, value) {
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int24.writeInt24LE(this.buffer, offset, value);
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};
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this.sampleByteLength = 3;
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}
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else {
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args.bitDepth = 16;
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this.readSample = this.buffer.readInt16LE;
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this.writeSample = this.buffer.writeInt16LE;
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this.sampleByteLength = 2;
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}
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this.channels = args.channels;
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this.sampleRate = args.sampleRate;
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this.inputs = [];
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}
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util.inherits(Mixer, Readable);
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Mixer.prototype._read = function() {
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var samples = 0;
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if (this.inputs.length){
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samples = this.inputs.map(function (input) {
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return input.availSamples() || 0;
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}).reduce(function(a,b){
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return Math.min(a,b);
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});
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}
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if (samples) {
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var mixedBuffer = new Buffer(samples * this.sampleByteLength * this.channels);
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mixedBuffer.fill(0);
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this.inputs.forEach(function (input) {
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if (this.channels == 1) {
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var inputBuffer = input.readMono(samples);
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} else {
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var inputBuffer = input.readStereo(samples);
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}
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for (var i = 0; i < samples * this.channels; i++) {
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this.writeSample.call(mixedBuffer, this.readSample.call(mixedBuffer, i * this.sampleByteLength) + Math.round(this.readSample.call(inputBuffer, i * this.sampleByteLength) / this.inputs.length), i * this.sampleByteLength);
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}
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}.bind(this));
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this.push(mixedBuffer);
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} else {
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if (this.inputs.length){
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setImmediate(this._read.bind(this));
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}
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}
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};
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Mixer.prototype.input = function (args) {
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if (typeof args === 'undefined') args = {};
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var input = new Input({
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mixer: this,
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channels: args.channels || this.channels,
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bitDepth: args.bitDepth || this.bitDepth,
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sampleRate: args.sampleRate || this.sampleRate
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});
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this.inputs.push(input);
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input.on('finish', () =>{
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this.inputs.splice(this.inputs.indexOf(input), 1);
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});
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if (this.inputs.length === 1){
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setImmediate(this._read.bind(this));
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}
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return input;
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};
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module.exports = Mixer;
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