openwebrx-clone/htdocs/lib/AudioEngine.js

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// this controls if the new AudioWorklet API should be used if available.
// the engine will still fall back to the ScriptProcessorNode if this is set to true but not available in the browser.
var useAudioWorklets = true;
function AudioEngine(maxBufferLength, audioReporter) {
this.audioReporter = audioReporter;
this.initStats();
this.resetStats();
var ctx = window.AudioContext || window.webkitAudioContext;
if (!ctx) {
return;
}
this.audioContext = new ctx();
this.allowed = this.audioContext.state === 'running';
this.started = false;
this.audioCodec = new ImaAdpcmCodec();
this.compression = 'none';
this.setupResampling();
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this.resampler = new Interpolator(this.resamplingFactor);
this.maxBufferSize = maxBufferLength * this.getSampleRate();
}
AudioEngine.prototype.start = function(callback) {
var me = this;
if (me.resamplingFactor === 0) return; //if failed to find a valid resampling factor...
if (me.started) {
if (callback) callback(false);
return;
}
me.audioContext.resume().then(function(){
me.allowed = me.audioContext.state === 'running';
if (!me.allowed) {
if (callback) callback(false);
return;
}
me.started = true;
me.gainNode = me.audioContext.createGain();
me.gainNode.connect(me.audioContext.destination);
if (useAudioWorklets && me.audioContext.audioWorklet) {
me.audioContext.audioWorklet.addModule('static/lib/AudioProcessor.js').then(function(){
me.audioNode = new AudioWorkletNode(me.audioContext, 'openwebrx-audio-processor', {
numberOfInputs: 0,
numberOfOutputs: 1,
outputChannelCount: [1],
processorOptions: {
maxBufferSize: me.maxBufferSize
}
});
me.audioNode.connect(me.gainNode);
me.audioNode.port.addEventListener('message', function(m){
var json = JSON.parse(m.data);
if (typeof(json.buffersize) !== 'undefined') {
me.audioReporter({
buffersize: json.buffersize
});
}
if (typeof(json.samplesProcessed) !== 'undefined') {
me.audioSamples.add(json.samplesProcessed);
}
});
me.audioNode.port.start();
if (callback) callback(true, 'AudioWorklet');
});
} else {
me.audioBuffers = [];
if (!AudioBuffer.prototype.copyToChannel) { //Chrome 36 does not have it, Firefox does
AudioBuffer.prototype.copyToChannel = function (input, channel) //input is Float32Array
{
var cd = this.getChannelData(channel);
for (var i = 0; i < input.length; i++) cd[i] = input[i];
}
}
var bufferSize;
if (me.audioContext.sampleRate < 44100 * 2)
bufferSize = 4096;
else if (me.audioContext.sampleRate >= 44100 * 2 && me.audioContext.sampleRate < 44100 * 4)
bufferSize = 4096 * 2;
else if (me.audioContext.sampleRate > 44100 * 4)
bufferSize = 4096 * 4;
function audio_onprocess(e) {
var total = 0;
var out = new Float32Array(bufferSize);
while (me.audioBuffers.length) {
var b = me.audioBuffers.shift();
// not enough space to fit all data, so splice and put back in the queue
if (total + b.length > bufferSize) {
var spaceLeft = bufferSize - total;
var tokeep = b.subarray(0, spaceLeft);
out.set(tokeep, total);
var tobuffer = b.subarray(spaceLeft, b.length);
me.audioBuffers.unshift(tobuffer);
total += spaceLeft;
break;
} else {
out.set(b, total);
total += b.length;
}
}
e.outputBuffer.copyToChannel(out, 0);
me.audioSamples.add(total);
}
//on Chrome v36, createJavaScriptNode has been replaced by createScriptProcessor
var method = 'createScriptProcessor';
if (me.audioContext.createJavaScriptNode) {
method = 'createJavaScriptNode';
}
me.audioNode = me.audioContext[method](bufferSize, 0, 1);
me.audioNode.onaudioprocess = audio_onprocess;
me.audioNode.connect(me.gainNode);
if (callback) callback(true, 'ScriptProcessorNode');
}
setInterval(me.reportStats.bind(me), 1000);
});
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};
AudioEngine.prototype.isAllowed = function() {
return this.allowed;
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};
AudioEngine.prototype.reportStats = function() {
if (this.audioNode.port) {
this.audioNode.port.postMessage(JSON.stringify({cmd:'getStats'}));
} else {
this.audioReporter({
buffersize: this.getBuffersize()
});
}
};
AudioEngine.prototype.initStats = function() {
var me = this;
var buildReporter = function(key) {
return function(v){
var report = {};
report[key] = v;
me.audioReporter(report);
}
};
this.audioBytes = new Measurement();
this.audioBytes.report(10000, 1000, buildReporter('audioByteRate'));
this.audioSamples = new Measurement();
this.audioSamples.report(10000, 1000, buildReporter('audioRate'));
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};
AudioEngine.prototype.resetStats = function() {
this.audioBytes.reset();
this.audioSamples.reset();
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};
AudioEngine.prototype.setupResampling = function() { //both at the server and the client
var output_range_max = 12000;
var output_range_min = 8000;
var targetRate = this.audioContext.sampleRate;
var i = 1;
while (true) {
var audio_server_output_rate = Math.floor(targetRate / i);
if (audio_server_output_rate < output_range_min) {
this.resamplingFactor = 0;
this.outputRate = 0;
divlog('Your audio card sampling rate (' + targetRate + ') is not supported.<br />Please change your operating system default settings in order to fix this.', 1);
break;
} else if (audio_server_output_rate >= output_range_min && audio_server_output_rate <= output_range_max) {
this.resamplingFactor = i;
this.outputRate = audio_server_output_rate;
break; //okay, we're done
}
i++;
}
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};
AudioEngine.prototype.getOutputRate = function() {
return this.outputRate;
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};
AudioEngine.prototype.getSampleRate = function() {
return this.audioContext.sampleRate;
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};
AudioEngine.prototype.pushAudio = function(data) {
if (!this.audioNode) return;
this.audioBytes.add(data.byteLength);
var buffer;
if (this.compression === "adpcm") {
//resampling & ADPCM
buffer = this.audioCodec.decode(new Uint8Array(data));
} else {
buffer = new Int16Array(data);
}
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buffer = this.resampler.process(buffer);
if (this.audioNode.port) {
// AudioWorklets supported
this.audioNode.port.postMessage(buffer);
} else {
// silently drop excess samples
if (this.getBuffersize() + buffer.length <= this.maxBufferSize) {
this.audioBuffers.push(buffer);
}
}
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};
AudioEngine.prototype.setCompression = function(compression) {
this.compression = compression;
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};
AudioEngine.prototype.setVolume = function(volume) {
this.gainNode.gain.value = volume;
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};
AudioEngine.prototype.getBuffersize = function() {
// only available when using ScriptProcessorNode
if (!this.audioBuffers) return 0;
return this.audioBuffers.map(function(b){ return b.length; }).reduce(function(a, b){ return a + b; }, 0);
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};
function ImaAdpcmCodec() {
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this.reset();
}
ImaAdpcmCodec.prototype.reset = function() {
this.stepIndex = 0;
this.predictor = 0;
this.step = 0;
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};
ImaAdpcmCodec.imaIndexTable = [ -1, -1, -1, -1, 2, 4, 6, 8, -1, -1, -1, -1, 2, 4, 6, 8 ];
ImaAdpcmCodec.imaStepTable = [
7, 8, 9, 10, 11, 12, 13, 14, 16, 17,
19, 21, 23, 25, 28, 31, 34, 37, 41, 45,
50, 55, 60, 66, 73, 80, 88, 97, 107, 118,
130, 143, 157, 173, 190, 209, 230, 253, 279, 307,
337, 371, 408, 449, 494, 544, 598, 658, 724, 796,
876, 963, 1060, 1166, 1282, 1411, 1552, 1707, 1878, 2066,
2272, 2499, 2749, 3024, 3327, 3660, 4026, 4428, 4871, 5358,
5894, 6484, 7132, 7845, 8630, 9493, 10442, 11487, 12635, 13899,
15289, 16818, 18500, 20350, 22385, 24623, 27086, 29794, 32767
];
ImaAdpcmCodec.prototype.decode = function(data) {
var output = new Int16Array(data.length * 2);
for (var i = 0; i < data.length; i++) {
output[i * 2] = this.decodeNibble(data[i] & 0x0F);
output[i * 2 + 1] = this.decodeNibble((data[i] >> 4) & 0x0F);
}
return output;
};
ImaAdpcmCodec.prototype.decodeNibble = function(nibble) {
this.stepIndex += ImaAdpcmCodec.imaIndexTable[nibble];
this.stepIndex = Math.min(Math.max(this.stepIndex, 0), 88);
var diff = this.step >> 3;
if (nibble & 1) diff += this.step >> 2;
if (nibble & 2) diff += this.step >> 1;
if (nibble & 4) diff += this.step;
if (nibble & 8) diff = -diff;
this.predictor += diff;
this.predictor = Math.min(Math.max(this.predictor, -32768), 32767);
this.step = ImaAdpcmCodec.imaStepTable[this.stepIndex];
return this.predictor;
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};
function Interpolator(factor) {
this.factor = factor;
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this.lowpass = new Lowpass(factor)
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}
Interpolator.prototype.process = function(data) {
var output = new Float32Array(data.length * this.factor);
for (var i = 0; i < data.length; i++) {
output[i * this.factor] = (data[i] + 0.5) / 32768;
}
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return this.lowpass.process(output);
};
function Lowpass(interpolation) {
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this.interpolation = interpolation;
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var transitionBandwidth = 0.05;
this.numtaps = Math.round(4 / transitionBandwidth);
if (this.numtaps % 2 == 0) this.numtaps += 1;
var cutoff = 1 / interpolation;
this.coefficients = this.getCoefficients(cutoff / 2);
this.delay = new Float32Array(this.numtaps);
for (var i = 0; i < this.numtaps; i++){
this.delay[i] = 0;
}
this.delayIndex = 0;
}
Lowpass.prototype.getCoefficients = function(cutoffRate) {
var middle = Math.floor(this.numtaps / 2);
// hamming window
var window_function = function(r){
var rate = 0.5 + r / 2;
return 0.54 - 0.46 * Math.cos(2 * Math.PI * rate);
}
var output = [];
output[middle] = 2 * Math.PI * cutoffRate * window_function(0);
for (var i = 1; i <= middle; i++) {
output[middle - i] = output[middle + i] = (Math.sin(2 * Math.PI * cutoffRate * i) / i) * window_function(i / middle);
}
return this.normalizeCoefficients(output);
};
Lowpass.prototype.normalizeCoefficients = function(input) {
var sum = 0;
var output = [];
for (var i = 0; i < input.length; i++) {
sum += input[i];
}
for (var i = 0; i < input.length; i++) {
output[i] = input[i] / sum;
}
return output;
};
Lowpass.prototype.process = function(input) {
output = new Float32Array(input.length);
for (var oi = 0; oi < input.length; oi++) {
this.delay[this.delayIndex] = input[oi];
this.delayIndex = (this.delayIndex + 1) % this.numtaps;
var acc = 0;
var index = this.delayIndex;
for (var i = 0; i < this.numtaps; ++i) {
var index = index != 0 ? index - 1 : this.numtaps - 1;
acc += this.delay[index] * this.coefficients[i];
if (isNaN(acc)) debugger;
}
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// gain by interpolation
output[oi] = this.interpolation * acc;
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}
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return output;
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};