// 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(); this.onStartCallbacks = []; this.started = false; this.audioContext = this.buildAudioContext(); if (!this.audioContext) { return; } var me = this; this.audioContext.onstatechange = function() { if (me.audioContext.state !== 'running') return; me._start(); } var onAudio = function(audioData) { me.playbackAudio(audioData); } this.audioCodecs = { "adpcm": new ImaAdpcmCodec(onAudio), "opus": new OpusCodec(onAudio) }; this.compression = 'none'; this.setupResampling(); this.resampler = new Interpolator(this.resamplingFactor); this.hdResampler = new Interpolator(this.hdResamplingFactor); this.maxBufferSize = maxBufferLength * this.getSampleRate(); } AudioEngine.prototype.buildAudioContext = function() { var ctxClass = window.AudioContext || window.webkitAudioContext; if (!ctxClass) { return; } // known good sample rates var goodRates = [48000, 44100, 96000] // let the browser chose the sample rate, if it is good, use it var ctx = new ctxClass({latencyHint: 'playback'}); if (goodRates.indexOf(ctx.sampleRate) >= 0) { return ctx; } // if that didn't work, try if any of the good rates work if (goodRates.some(function(sr) { try { ctx = new ctxClass({sampleRate: sr, latencyHint: 'playback'}); return true; } catch (e) { return false; } }, this)) { return ctx; } // fallback: let the browser decide // this may cause playback problems down the line return new ctxClass({latencyHint: 'playback'}); } AudioEngine.prototype.resume = function(){ this.audioContext.resume(); } AudioEngine.prototype._start = function() { var me = this; // if failed to find a valid resampling factor... if (me.resamplingFactor === 0) { return; } // been started before? if (me.started) { return; } // are we allowed to play audio? if (!me.isAllowed()) { return; } me.started = true; var runCallbacks = function(workletType) { var callbacks = me.onStartCallbacks; me.onStartCallbacks = false; callbacks.forEach(function(c) { c(workletType); }); }; 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(); runCallbacks('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); runCallbacks('ScriptProcessorNode') } setInterval(me.reportStats.bind(me), 1000); }; AudioEngine.prototype.onStart = function(callback) { if (this.onStartCallbacks) { this.onStartCallbacks.push(callback); } else { callback(); } }; AudioEngine.prototype.isAllowed = function() { return this.audioContext.state === 'running'; }; 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')); }; AudioEngine.prototype.resetStats = function() { this.audioBytes.reset(); this.audioSamples.reset(); }; AudioEngine.prototype.setupResampling = function() { //both at the server and the client var targetRate = this.audioContext.sampleRate; var audio_params = this.findRate(8000, 12000); if (!audio_params) { this.resamplingFactor = 0; this.outputRate = 0; divlog('Your audio card sampling rate (' + targetRate + ') is not supported.
Please change your operating system default settings in order to fix this.', 1); } else { this.resamplingFactor = audio_params.resamplingFactor; this.outputRate = audio_params.outputRate; } var hd_audio_params = this.findRate(36000, 48000); if (!hd_audio_params) { this.hdResamplingFactor = 0; this.hdOutputRate = 0; divlog('Your audio card sampling rate (' + targetRate + ') is not supported for HD audio
Please change your operating system default settings in order to fix this.', 1); } else { this.hdResamplingFactor = hd_audio_params.resamplingFactor; this.hdOutputRate = hd_audio_params.outputRate; } }; AudioEngine.prototype.findRate = function(low, high) { var targetRate = this.audioContext.sampleRate; var i = 1; while (true) { var audio_server_output_rate = Math.floor(targetRate / i); if (audio_server_output_rate < low) { return; } else if (audio_server_output_rate >= low && audio_server_output_rate <= high) { return { resamplingFactor: i, outputRate: audio_server_output_rate } } i++; }; } AudioEngine.prototype.getOutputRate = function() { return this.outputRate; }; AudioEngine.prototype.getHdOutputRate = function() { return this.hdOutputRate; } AudioEngine.prototype.getSampleRate = function() { return this.audioContext.sampleRate; }; AudioEngine.prototype.processAudio = function(data, resampler) { if (!this.audioNode) return; this.audioBytes.add(data.byteLength); if (this.compression !== "none") { this.audioCodecs[this.compression].decodeAsync(new Uint8Array(data)); } else { this.playbackAudio(new Int16Array(data)); } } AudioEngine.prototype.playbackAudio = function(audioData) { //var buffer = this.resampler.process(audioData); if (this.audioNode.port) { // AudioWorklets supported this.audioNode.port.postMessage(audioData); } else { // silently drop excess samples if (this.getBuffersize() + buffer.length <= this.maxBufferSize) { this.audioBuffers.push(buffer); } } }; AudioEngine.prototype.pushAudio = function(data) { this.processAudio(data, this.resampler); }; AudioEngine.prototype.pushHdAudio = function(data) { this.processAudio(data, this.hdResampler); } AudioEngine.prototype.setCompression = function(compression) { this.compression = compression; }; AudioEngine.prototype.setVolume = function(volume) { this.gainNode.gain.value = volume; }; 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); }; function ImaAdpcmCodec(callback) { this.reset(); this.callback = callback; } ImaAdpcmCodec.prototype.reset = function() { this.stepIndex = 0; this.predictor = 0; this.step = 0; this.synchronized = 0; this.syncWord = "SYNC"; this.syncCounter = 0; this.skip = 0; }; 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.decodeAsync = function(data, callback) { var output = new Int16Array(data.length * 2); var index = this.skip; var oi = 0; while (index < data.length) { while (this.synchronized < 4 && index < data.length) { if (data[index] === this.syncWord.charCodeAt(this.synchronized)) { this.synchronized++; } else { this.synchronized = 0; } index++; if (this.synchronized === 4) { if (index + 4 < data.length) { var syncData = new Int16Array(data.buffer.slice(index, index + 4)); this.stepIndex = syncData[0]; this.predictor = syncData[1]; } this.syncCounter = 1000; index += 4; break; } } while (index < data.length) { if (this.syncCounter-- < 0) { this.synchronized = 0; break; } output[oi++] = this.decodeNibble(data[index] & 0x0F); output[oi++] = this.decodeNibble(data[index] >> 4); index++; } } this.skip = index - data.length; this.callback(output.slice(0, oi)); }; 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; }; function OpusCodec(callback) { this.callback = callback; this.resetDecoder(); } OpusCodec.prototype.resetDecoder = function() { var me = this; me.decoder = new AudioDecoder({ output: function(audioData) { var buffer = new Float32Array(audioData.numberOfFrames * audioData.numberOfChannels); audioData.copyTo(buffer, {planeIndex: 0}); me.callback(buffer); }, error: function(e) { console.error(e); me.resetDecoder(); } }); me.decoder.configure({ codec: "opus", sampleRate: 12000, numberOfChannels: 1 }); } OpusCodec.prototype.decodeAsync = function(data) { this.decoder.decode(new EncodedAudioChunk({ type: "key", data: data, timestamp: 0 })); }; function Interpolator(factor) { this.factor = factor; this.lowpass = new Lowpass(factor) } 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; } return this.lowpass.process(output); }; function Lowpass(interpolation) { this.interpolation = interpolation; 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; } // gain by interpolation output[oi] = this.interpolation * acc; } return output; };