pediatric-ai-scribe-v3/src/utils/transcribeAWS.js

// ============================================================
// TRANSCRIBE-AWS.JS — Amazon Transcribe Streaming
// No S3 required. Audio streams directly to AWS.
//
// Env vars:
//   TRANSCRIBE_PROVIDER=aws          — use this instead of Whisper
//   AWS_TRANSCRIBE_MEDICAL=true      — use Transcribe Medical (better
//                                      accuracy for clinical dictation)
//   AWS_TRANSCRIBE_SPECIALTY=PRIMARYCARE  — medical specialty
//     Options: PRIMARYCARE, CARDIOLOGY, NEUROLOGY, ONCOLOGY,
//              RADIOLOGY, UROLOGY
//   AWS_BEDROCK_REGION               — reused for Transcribe region
//   AWS_ACCESS_KEY_ID / AWS_SECRET_ACCESS_KEY — reused credentials
// ============================================================

const CHUNK_SIZE = 32768; // 32 KB per audio chunk

async function* makeAudioStream(buffer) {
  for (var i = 0; i < buffer.length; i += CHUNK_SIZE) {
    yield { AudioEvent: { AudioChunk: buffer.slice(i, i + CHUNK_SIZE) } };
    // Yield to event loop between chunks to avoid blocking
    await new Promise(function(r) { setTimeout(r, 0); });
  }
}

async function transcribeWithAWS(audioBuffer, mimeType) {
  var TranscribeModule = require('@aws-sdk/client-transcribe-streaming');
  var TranscribeStreamingClient = TranscribeModule.TranscribeStreamingClient;

  var region = process.env.AWS_BEDROCK_REGION || process.env.AWS_REGION || 'us-east-1';
  var credentials = process.env.AWS_ACCESS_KEY_ID ? {
    accessKeyId: process.env.AWS_ACCESS_KEY_ID,
    secretAccessKey: process.env.AWS_SECRET_ACCESS_KEY
  } : undefined;

  var client = new TranscribeStreamingClient({ region: region, credentials: credentials });

  // Map browser MIME type to AWS MediaEncoding
  // audio/webm;codecs=opus  → ogg-opus (same Opus codec, different container)
  // audio/ogg;codecs=opus   → ogg-opus (exact match)
  // audio/wav               → pcm
  var mediaEncoding = 'ogg-opus';
  if (mimeType && mimeType.indexOf('wav') !== -1) mediaEncoding = 'pcm';

  var useMedical = process.env.AWS_TRANSCRIBE_MEDICAL === 'true';
  var specialty = process.env.AWS_TRANSCRIBE_SPECIALTY || 'PRIMARYCARE';

  var transcript = '';

  if (useMedical) {
    var StartMedicalStreamTranscriptionCommand = TranscribeModule.StartMedicalStreamTranscriptionCommand;
    var medCmd = new StartMedicalStreamTranscriptionCommand({
      LanguageCode: 'en-US',
      MediaSampleRateHertz: 48000,
      MediaEncoding: mediaEncoding,
      Specialty: specialty,
      Type: 'DICTATION',
      AudioStream: makeAudioStream(audioBuffer)
    });
    var medResp = await client.send(medCmd);
    for await (var event of medResp.TranscriptResultStream) {
      if (event.TranscriptEvent && event.TranscriptEvent.Transcript) {
        var results = event.TranscriptEvent.Transcript.Results || [];
        for (var i = 0; i < results.length; i++) {
          var r = results[i];
          if (!r.IsPartial && r.Alternatives && r.Alternatives[0]) {
            transcript += r.Alternatives[0].Transcript + ' ';
          }
        }
      }
    }
  } else {
    var StartStreamTranscriptionCommand = TranscribeModule.StartStreamTranscriptionCommand;
    var cmd = new StartStreamTranscriptionCommand({
      LanguageCode: 'en-US',
      MediaSampleRateHertz: 48000,
      MediaEncoding: mediaEncoding,
      AudioStream: makeAudioStream(audioBuffer)
    });
    var resp = await client.send(cmd);
    for await (var ev of resp.TranscriptResultStream) {
      if (ev.TranscriptEvent && ev.TranscriptEvent.Transcript) {
        var res = ev.TranscriptEvent.Transcript.Results || [];
        for (var j = 0; j < res.length; j++) {
          var item = res[j];
          if (!item.IsPartial && item.Alternatives && item.Alternatives[0]) {
            transcript += item.Alternatives[0].Transcript + ' ';
          }
        }
      }
    }
  }

  return transcript.trim();
}

// Check if AWS Transcribe is available and configured
function isAWSTranscribeConfigured() {
  try {
    require('@aws-sdk/client-transcribe-streaming');
    return !!(process.env.AWS_BEDROCK_REGION || process.env.AWS_REGION);
  } catch (e) {
    return false;
  }
}

module.exports = { transcribeWithAWS, isAWSTranscribeConfigured };