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/* pcm-worklet.js ---------------------------------------------------------
* Down-samples the input to 16 kHz mono and posts Int16Array chunks back
* to the main thread. Buffer size is 128 frames to keep latency < 10 ms.
*/
class PCMWorklet extends AudioWorkletProcessor {
constructor() {
super();
this._decimator = new Float32Array(0);
this._ratio = sampleRate / 16000; // e.g. 48k / 16k = 3
this._chunk = 0;
}
process(inputs) {
const input = inputs[0][0];
if (!input) return true;
// Down-sample on the fly
for (let i = 0; i < input.length; i += this._ratio) {
this._decimator[this._chunk++] = input[i|0];
if (this._chunk === 160) { // 10 ms at 16 kHz
// Convert to 16-bit PCM
const i16 = new Int16Array(160);
for (let j = 0; j < 160; ++j) {
const s = Math.max(-1, Math.min(1, this._decimator[j]));
i16[j] = s < 0 ? s * 0x8000 : s * 0x7FFF;
}
this.port.postMessage(i16.buffer);
this._chunk = 0;
}
}
return true;
}
}
registerProcessor("pcm-worklet", PCMWorklet);
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