simstudioai--sim/apps/sim/lib/speech/audio.ts

/**
 * Convert Float32 PCM samples to 16-bit signed integer PCM.
 * Required for ElevenLabs realtime STT (pcm_16000 format).
 */
export function floatTo16BitPCM(float32Array: Float32Array): ArrayBuffer {
  const buffer = new ArrayBuffer(float32Array.length * 2)
  const view = new DataView(buffer)
  for (let i = 0; i < float32Array.length; i++) {
    const s = Math.max(-1, Math.min(1, float32Array[i]))
    view.setInt16(i * 2, s < 0 ? s * 0x8000 : s * 0x7fff, true)
  }
  return buffer
}

/**
 * Encode an ArrayBuffer as a base64 string for WebSocket transport.
 */
export function arrayBufferToBase64(buffer: ArrayBuffer): string {
  const bytes = new Uint8Array(buffer)
  let binary = ''
  for (let i = 0; i < bytes.length; i++) {
    binary += String.fromCharCode(bytes[i])
  }
  return btoa(binary)
}