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https://github.com/block/buzz.git
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72 lines
2.7 KiB
JavaScript
72 lines
2.7 KiB
JavaScript
// AudioWorklet processor — runs in the AudioWorklet thread.
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// Accumulates PCM Float32 samples and sends 20ms batches to the main thread.
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//
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// ASSUMPTION: AudioContext runs at 48 kHz (Tauri WebView default on desktop).
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// The 960-sample buffer = exactly one 20ms Opus frame at 48 kHz. If the
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// sample rate differs (e.g. 44.1 kHz), frames will be slightly misaligned
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// with the Opus encoder. getUserMedia should request sampleRate: 48000.
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//
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// Supports push-to-talk (PTT) gating: when `this.transmitting` is false,
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// incoming audio frames are discarded and the buffer is reset. The main thread
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// sends `{ type: 'ptt', active: boolean }` messages to toggle transmission.
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// Default: transmitting=true (open mic for VAD mode compatibility).
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//
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// Note: when the worklet is disconnected, any partial buffer (< 960 samples)
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// is silently dropped. The last ~20ms of speech may be lost on huddle leave.
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// This is acceptable for voice — losing a partial syllable at disconnect is
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// imperceptible compared to the natural end-of-conversation flow.
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class SttTapProcessor extends AudioWorkletProcessor {
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constructor() {
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super();
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this.buffer = new Float32Array(960); // ~20ms at 48kHz
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this.offset = 0;
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this.transmitting = true; // default: open (VAD mode). PTT mode sets false on init.
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// Listen for PTT state changes from main thread.
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// Direction: main→worklet (receives). The worklet→main direction uses
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// this.port.postMessage for PCM data — these don't conflict.
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this.port.onmessage = (e) => {
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if (e.data && e.data.type === "ptt") {
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this.transmitting = e.data.active;
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}
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};
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}
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process(inputs) {
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const input = inputs[0]?.[0]; // mono channel
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if (!input) return true;
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// PTT gating: discard frames when not transmitting.
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// Reset buffer offset so we don't send stale audio when PTT activates.
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if (!this.transmitting) {
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this.offset = 0;
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return true;
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}
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// Accumulate samples
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const remaining = this.buffer.length - this.offset;
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const toCopy = Math.min(input.length, remaining);
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this.buffer.set(input.subarray(0, toCopy), this.offset);
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this.offset += toCopy;
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// Flush when buffer is full
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if (this.offset >= this.buffer.length) {
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// Transfer ownership for zero-copy
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this.port.postMessage(this.buffer, [this.buffer.buffer]);
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this.buffer = new Float32Array(960);
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this.offset = 0;
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// Handle leftover samples
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if (toCopy < input.length) {
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const leftover = input.subarray(toCopy);
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this.buffer.set(leftover);
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this.offset = leftover.length;
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}
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}
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return true;
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}
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}
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registerProcessor("stt-tap-processor", SttTapProcessor);
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