input objects with mono/stereo conversion

lib/input.js

@@ -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();
+}
+

lib/mixer.js

@@ -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