Xefir/audio-mixer
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input objects with mono/stereo conversion

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This commit is contained in:
alfred 2013-12-31 10:06:42 +00:00
parent 16b2285694
commit 126266e4d9
2 changed files with 95 additions and 2 deletions
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90
lib/input.js Normal file
View File

@ -0,0 +1,90 @@
var
Writable = require('stream').Writable,
util = require('util'),
;
function Input(args) {
this.buffer = Buffer.concat([this.buffer, chunk]);
if (typeof args === 'undefined') args = {};
if (args.channels != 1 && args.channels != 2) args.channels = 2;
if (typeof args.sampleRate !== 'number' || args.sampleRate < 1) args.sampleRate = 44100;
this.buffer = new Buffer(0);
if (args.channels == 1) this.readMono = this.read;
if (args.channels == 2) this.readStereo = this.read;
if (args.bitDepth == 8) {
this.readSample = Buffer.readInt8;
this.writeSample = Buffer.writeInt8;
this.sampleByteLength = 1;
}
else if (args.bitDepth == 32) {
this.readSample = Buffer.readInt32LE;
this.writeSample = Buffer.writeInt32LE;
this.sampleByteLength = 4;
}
else {
args.bitDepth = 16;
this.readSample = Buffer.readInt16LE;
this.writeSample = Buffer.writeInt16LE;
this.sampleByteLength = 2;
}
this.channels = args.channels;
this.bitDepth = args.bitDepth;
this.sampleRate = args.sampleRate;
}
util.inherits(Input, Writable);
Input.prototype.read = function (samples) {
var bytes = samples * (this.bitDepth / 8) * this.channels;
if (this.buffer.length < bytes) bytes = this.buffer.length;
var r = this.buffer.slice(0, bytes);
this.buffer = this.buffer.slice(bytes);
return r;
}
Input.prototype.readMono = function (samples) {
// This function will be overridden by this.read, if input already is mono.
var stereoBuffer = this.read(samples);
var monoBuffer = new Buffer(stereoBuffer.length / 2);
var s = this.availSamples(stereoBuffer.length);
for (var i = 0; i < s; i++) {
var l = this.readSample.call(stereoBuffer, i * this.sampleByteLength * 2);
var r = this.readSample.call(stereoBuffer, (i * this.sampleByteLength * 2) + this.sampleByteLength);
this.writeSample.call(monoBuffer, Math.round((l + r) / 2), i * this.sampleByteLength);
}
return monoBuffer;
}
Input.prototype.readStereo = function (samples) {
// This function will be overridden by this.read, if input already is stereo.
var monoBuffer = this.read(samples);
var stereoBuffer = new Buffer(monoBuffer.length * 2);
var s = this.availSamples(monoBuffer.length);
for (var i = 0; i < s; i++) {
var m = this.readSample.call(monoBuffer, i * this.sampleByteLength);
this.writeSample.call(stereoBuffer, m, i * this.sampleByteLength * 2);
this.writeSample.call(stereoBuffer, m, (i * this.sampleByteLength * 2) + this.sampleByteLength);
}
return stereoBuffer;
}
Input.availSamples = function (length) {
if (typeof length === 'undefined') length = this.buffer.length;
return Math.floor(length / ((this.bitDepth / 8) * this.channels));
}
Input.prototype._write = function (chunk, encoding, next) {
/*
if (!Buffer.isBuffer(chunk)) {
chunk = new Buffer(chunk, encoding);
}
*/
this.buffer = Buffer.concat([this.buffer, chunk]);
next();
}

7
lib/mixer.js
View File

@ -1,13 +1,15 @@
var
Readable = require('stream').Readable,
util = require('util')
util = require('util'),
Input = require('./input.js')
;
function Mixer(args) {
if (typeof args === 'undefined') args = {};
if (args.channels != 1 && args.channels != 2) args.channels = 2;
if (args.bitDepth != 8 && args.bitDepth != 16 && args.bitDepth != 32) args.channels = 2;
if (args.bitDepth != 8 && args.bitDepth != 16 && args.bitDepth != 32) args.bitDepth = 16;
if (typeof args.sampleRate === 'number' || args.sampleRate < 1) args.sampleRate = 44100;
this.channels = args.channels;
@ -27,6 +29,7 @@ Mixer.prototype.input = function (args) {
if (typeof args === 'undefined') args = {};
var input = new Input({
mixer: this,
channels: args.channels || this.channels,
bitDepth: args.bitDepth || this.bitDepth,
sampleRate: args.sampleRate || this.sampleRate