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function PCMPlayer(option) {
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this.init(option);
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}
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PCMPlayer.prototype.init = function(option) {
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var defaults = {
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encoding: '16bitInt',
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channels: 1,
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sampleRate: 8000,
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flushingTime: 1000
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};
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this.option = Object.assign({}, defaults, option);
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this.samples = new Float32Array();
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this.flush = this.flush.bind(this);
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this.interval = setInterval(this.flush, this.option.flushingTime);
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this.maxValue = this.getMaxValue();
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this.typedArray = this.getTypedArray();
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this.createContext();
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};
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PCMPlayer.prototype.getMaxValue = function () {
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var encodings = {
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'8bitInt': 128,
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'16bitInt': 32768,
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'32bitInt': 2147483648,
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'32bitFloat': 1
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}
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return encodings[this.option.encoding] ? encodings[this.option.encoding] : encodings['16bitInt'];
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};
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PCMPlayer.prototype.getTypedArray = function () {
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var typedArrays = {
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'8bitInt': Int8Array,
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'16bitInt': Int16Array,
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'32bitInt': Int32Array,
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'32bitFloat': Float32Array
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}
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return typedArrays[this.option.encoding] ? typedArrays[this.option.encoding] : typedArrays['16bitInt'];
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};
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PCMPlayer.prototype.createContext = function() {
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this.audioCtx = new (window.AudioContext || window.webkitAudioContext)();
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this.gainNode = this.audioCtx.createGain();
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this.gainNode.gain.value = 1;
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this.gainNode.connect(this.audioCtx.destination);
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this.startTime = this.audioCtx.currentTime;
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};
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PCMPlayer.prototype.isTypedArray = function(data) {
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return (data.byteLength && data.buffer && data.buffer.constructor == ArrayBuffer);
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};
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PCMPlayer.prototype.feed = function(data) {
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if (!this.isTypedArray(data)) return;
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data = this.getFormatedValue(data);
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var tmp = new Float32Array(this.samples.length + data.length);
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tmp.set(this.samples, 0);
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tmp.set(data, this.samples.length);
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this.samples = tmp;
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};
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PCMPlayer.prototype.getFormatedValue = function(data) {
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var data = new this.typedArray(data.buffer),
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float32 = new Float32Array(data.length),
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i;
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for (i = 0; i < data.length; i++) {
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float32[i] = data[i] / this.maxValue;
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}
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return float32;
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};
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PCMPlayer.prototype.volume = function(volume) {
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this.gainNode.gain.value = volume;
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};
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PCMPlayer.prototype.destroy = function() {
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if (this.interval) {
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clearInterval(this.interval);
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}
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this.samples = null;
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this.audioCtx.close();
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this.audioCtx = null;
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};
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PCMPlayer.prototype.flush = function() {
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if (!this.samples.length) return;
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var bufferSource = this.audioCtx.createBufferSource(),
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length = this.samples.length / this.option.channels,
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audioBuffer = this.audioCtx.createBuffer(this.option.channels, length, this.option.sampleRate),
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audioData,
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channel,
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offset,
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i,
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decrement;
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for (channel = 0; channel < this.option.channels; channel++) {
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audioData = audioBuffer.getChannelData(channel);
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offset = channel;
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decrement = 50;
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for (i = 0; i < length; i++) {
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audioData[i] = this.samples[offset];
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/* fadein */
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if (i < 50) {
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audioData[i] = (audioData[i] * i) / 50;
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}
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/* fadeout*/
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if (i >= (length - 51)) {
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audioData[i] = (audioData[i] * decrement--) / 50;
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}
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offset += this.option.channels;
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}
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}
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if (this.startTime < this.audioCtx.currentTime) {
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this.startTime = this.audioCtx.currentTime;
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}
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console.log('start vs current '+this.startTime+' vs '+this.audioCtx.currentTime+' duration: '+audioBuffer.duration);
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bufferSource.buffer = audioBuffer;
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bufferSource.connect(this.gainNode);
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bufferSource.start(this.startTime);
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this.startTime += audioBuffer.duration;
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this.samples = new Float32Array();
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};
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