File size: 1,848 Bytes
7248b12 | 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 | // @ts-check
/**
* AudioWorkletProcessor that downsamples the mic to 16 kHz Float32 and hands
* fixed 512-sample frames (32 ms, what Silero VAD expects) straight to the VAD
* worker over a transferred MessagePort, so a busy main thread can't drop them.
*
* main -> worklet: { kind: "enable", value: boolean }, { kind: "port", port }
*/
const TARGET_RATE = 16000;
const FRAME = 512;
class MicCaptureProcessor extends AudioWorkletProcessor {
constructor() {
super();
this._step = sampleRate / TARGET_RATE;
this._sum = 0;
this._count = 0;
this._phase = 0;
this._frame = new Float32Array(FRAME);
this._fill = 0;
this._enabled = true;
/** @type {MessagePort | null} */
this._out = null;
this.port.onmessage = (e) => {
if (e.data?.kind === "enable") {
this._enabled = !!e.data.value;
this._fill = 0;
} else if (e.data?.kind === "port") {
this._out = e.data.port;
}
};
}
process(inputs) {
const input = inputs[0];
const ch = input?.[0];
if (!ch || !this._enabled || !this._out) return true;
for (let i = 0; i < ch.length; i++) {
// Box average over one output period: a cheap low-pass that handles any
// context rate (44.1 k on many Macs, 48 k elsewhere).
this._sum += ch[i];
this._count += 1;
this._phase += 1;
if (this._phase >= this._step) {
this._phase -= this._step;
this._frame[this._fill++] = this._sum / this._count;
this._sum = 0;
this._count = 0;
if (this._fill === FRAME) {
const frame = this._frame;
this._out.postMessage(frame, [frame.buffer]);
this._frame = new Float32Array(FRAME);
this._fill = 0;
}
}
}
return true;
}
}
registerProcessor("mic-capture", MicCaptureProcessor);
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