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implement a ringbuffer in the audioworklet to optimize runtimes

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Jakob Ketterl
2019-10-19 18:09:50 +02:00
parent cc32e28b36
commit 00c5467a89
2 changed files with 33 additions and 45 deletions
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57
htdocs/lib/AudioProcessor.js
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@ -3,7 +3,11 @@ class OwrxAudioProcessor extends AudioWorkletProcessor {
super(options);
this.maxLength = options.processorOptions.maxLength;
this.reduceToLength = options.processorOptions.reduceToLength;
this.audio_buffers = [];
// initialize ringbuffer, make sure it aligns with the expected buffer size of 128
this.bufferSize = Math.round(sampleRate * this.maxLength / 128) * 128
this.audioBuffer = new Float32Array(this.bufferSize);
this.inPos = 0;
this.outPos = 0;
this.port.addEventListener('message', (m) => {
if (typeof(m.data) === 'string') {
const json = JSON.parse(m.data);
@ -11,48 +15,39 @@ class OwrxAudioProcessor extends AudioWorkletProcessor {
this.reportBuffers();
}
} else {
this.audio_buffers.push(new Float32Array(m.data));
// the ringbuffer size is aligned to the output buffer size, which means that the input buffers might
// need to wrap around the end of the ringbuffer, back to the start.
// it is better to have this processing here instead of in the time-critical process function.
if (this.inPos + m.data.length <= this.bufferSize) {
// we have enough space, so just copy data over.
this.audioBuffer.set(m.data, this.inPos);
} else {
// we don't have enough space, so we need to split the data.
const remaining = this.bufferSize - this.inPos;
this.audioBuffer.set(m.data.subarray(0, remaining), this.inPos);
this.audioBuffer.set(m.data.subarray(remaining));
}
this.inPos = (this.inPos + m.data.length) % this.bufferSize;
}
});
this.port.addEventListener('messageerror', console.error);
this.port.start();
}
process(inputs, outputs, parameters) {
//console.time('audio::process');
const samples = Math.min(128, this.remaining());
outputs[0].forEach((output) => {
let total = 0;
while (this.audio_buffers.length) {
const b = this.audio_buffers.shift();
const newLength = total + b.length;
const ol = output.length;
// not enough space to fit all data, so splice and put back in the queue
if (newLength > ol) {
const tokeep = b.slice(0, ol - total);
output.set(tokeep, total);
const tobuffer = b.slice(ol - total, b.length);
this.audio_buffers.unshift(tobuffer);
break;
} else {
output.set(b, total);
}
total = newLength;
}
output.set(this.audioBuffer.subarray(this.outPos, this.outPos + samples));
});
//console.timeEnd('audio::process');
this.outPos = (this.outPos + samples) % this.bufferSize;
return true;
}
bufferLength() {
return this.audio_buffers.map(function(b){ return b.length; }).reduce(function(a, b){ return a + b; }, 0);
remaining() {
const mod = (this.inPos - this.outPos) % this.bufferSize;
if (mod >= 0) return mod;
return mod + this.bufferSize;
}
reportBuffers() {
var we_have_more_than = (sec) => {
return sec * sampleRate < this.bufferLength();
};
if (we_have_more_than(this.maxLength)) while (we_have_more_than(this.reduceToLength)) {
this.audio_buffers.shift();
}
this.port.postMessage(JSON.stringify({buffersize: this.bufferLength()}));
this.port.postMessage(JSON.stringify({buffersize: this.remaining()}));
}
}