ML & DSP Streaming

When feeding live audio to ML models (speech recognition, VAD, keyword spotting, speaker ID, audio tagging), use streamFormat: 'float32' to receive samples as Float32Array directly — no manual decoding required.

Why float32?

Without streamFormat, native platforms deliver audio as base64-encoded strings. Every consumer must decode and convert manually:

// Before: 4-pass pipeline on every audio chunk
onAudioStream: async (event) => {
  const raw = atob(event.data as string);
  const bytes = new Uint8Array(raw.length);
  for (let i = 0; i < raw.length; i++) bytes[i] = raw.charCodeAt(i);
  const view = new DataView(bytes.buffer);
  const samples = new Float32Array(bytes.length / 2);
  for (let i = 0; i < samples.length; i++) {
    samples[i] = view.getInt16(i * 2, true) / 32768;
  }
  await model.feed(Array.from(samples));
}

With streamFormat: 'float32', the native layer does the Int16→Float32 conversion and skips base64 entirely:

// After: data is already Float32Array
onAudioStream: async (event) => {
  const samples = event.data as Float32Array;
  await model.feed(Array.from(samples));
}

On web, the AudioWorklet already operates on Float32 internally. Setting streamFormat: 'float32' skips the lossy Float32→Int16 roundtrip that normally happens for file-format compatibility.

Configuration

import { useAudioRecorder } from '@siteed/expo-audio-studio';

const { startRecording } = useAudioRecorder();

await startRecording({
  sampleRate: 16000,
  channels: 1,
  encoding: 'pcm_32bit',
  interval: 100,
  streamFormat: 'float32',
  onAudioStream: async (event) => {
    const samples = event.data as Float32Array;
    // Feed directly to your ML model, VAD, ASR, etc.
    await myModel.process(samples);
  },
});

Key settings for ML consumers:

• sampleRate: 16000 — most speech models expect 16 kHz
• channels: 1 — mono audio for inference
• streamFormat: 'float32' — Float32Array on all platforms
• interval: 100 — chunk delivery interval in ms (tune to your model's needs)

Backwards compatibility

The default is 'raw', which preserves existing behavior. No changes are needed for consumers that store or upload recorded files — streamFormat only affects the data delivered to onAudioStream.

	'raw' (default)	'float32'
Native onAudioStream data	base64 string	Float32Array
Web onAudioStream data	Float32Array	Float32Array
File recording	unaffected	unaffected