openwebrx-clone/htdocs/lib/AudioProcessor.js

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class OwrxAudioProcessor extends AudioWorkletProcessor {
constructor(options){
super(options);
// initialize ringbuffer, make sure it aligns with the expected buffer size of 128
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this.bufferSize = Math.round(options.processorOptions.maxBufferSize / 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);
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if (json.cmd && json.cmd === 'getBuffers') {
this.reportBuffers();
}
} else {
// 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();
}
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process(inputs, outputs) {
if (this.remaining() < 128) return true;
outputs[0].forEach((output) => {
output.set(this.audioBuffer.subarray(this.outPos, this.outPos + 128));
});
this.outPos = (this.outPos + 128) % this.bufferSize;
return true;
}
remaining() {
const mod = (this.inPos - this.outPos) % this.bufferSize;
if (mod >= 0) return mod;
return mod + this.bufferSize;
}
reportBuffers() {
this.port.postMessage(JSON.stringify({buffersize: this.remaining()}));
}
}
registerProcessor('openwebrx-audio-processor', OwrxAudioProcessor);