99 lines
2.8 KiB
JavaScript
99 lines
2.8 KiB
JavaScript
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/**
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* Pseudo-streaming transcription session for OpenAI-compatible Whisper
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* endpoints (faster-whisper, whisper.cpp, OpenAI, ...).
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*
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* The Whisper HTTP API cannot stream, so audio is buffered per segment and
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* transcribed on commit(). Live partials therefore only advance at segment
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* boundaries (the DictationStreamManager auto-commits every ~15s of speech).
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*
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* Implements the StreamingTranscriptionSession contract used by
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* DictationStreamManager.
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*/
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import { EventEmitter } from 'events';
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import { randomUUID } from 'crypto';
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import { transcribeAudio } from '../tts/stt.js';
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import { pcm16ToWav } from './audio.js';
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const OPENAI_COMPATIBLE_SAMPLE_RATE = 16000;
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export class OpenAICompatibleTranscriptionSession extends EventEmitter {
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/**
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* @param {{ baseURL: string, model: string, apiKey?: string, language?: string, prompt?: string }} config
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*/
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constructor(config) {
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super();
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this.config = config;
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this.requiredSampleRate = OPENAI_COMPATIBLE_SAMPLE_RATE;
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this.connected = false;
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this.segmentId = randomUUID();
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this.previousSegmentId = null;
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this.pcm16 = Buffer.alloc(0);
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}
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async connect() {
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if (!this.config.baseURL) {
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throw new Error('Custom STT server URL is not configured');
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}
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if (!this.config.model) {
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throw new Error('STT model is not configured');
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}
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this.connected = true;
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}
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appendPcm16(chunk) {
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if (!this.connected) {
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this.emit('error', new Error('STT session not connected'));
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return;
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}
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this.pcm16 = this.pcm16.length === 0 ? chunk : Buffer.concat([this.pcm16, chunk]);
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}
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commit() {
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if (!this.connected) {
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this.emit('error', new Error('STT session not connected'));
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return;
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}
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const committedId = this.segmentId;
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const previousSegmentId = this.previousSegmentId;
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const committedPcm16 = this.pcm16;
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this.previousSegmentId = committedId;
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this.segmentId = randomUUID();
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this.pcm16 = Buffer.alloc(0);
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this.emit('committed', { segmentId: committedId, previousSegmentId });
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void (async () => {
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try {
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const wav = pcm16ToWav(committedPcm16, OPENAI_COMPATIBLE_SAMPLE_RATE);
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const text = await transcribeAudio({
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audioBuffer: wav,
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mimeType: 'audio/wav',
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model: this.config.model,
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baseURL: this.config.baseURL,
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apiKey: this.config.apiKey,
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language: this.config.language,
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});
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this.emit('transcript', {
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segmentId: committedId,
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transcript: (text ?? '').trim(),
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isFinal: true,
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});
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} catch (err) {
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this.emit('error', err instanceof Error ? err : new Error(String(err)));
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}
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})();
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}
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clear() {
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this.pcm16 = Buffer.alloc(0);
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this.segmentId = randomUUID();
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}
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close() {
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this.connected = false;
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this.pcm16 = Buffer.alloc(0);
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}
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}
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