How to precisely sync AudioBufferSourceNode.start() with AudioRecorder.start()?

[RemyNtshaykolo]

Hi,

I’m using react-native-audio-api and I’d like to know the best way to:

• Play an AudioBufferSourceNode
• Record the microphone with AudioRecorder
• Start recording exactly when the buffer starts playing (same time reference)

Here is a very simplified example. The bufferSourceNode is passed in props:

import { AudioContext, AudioManager, AudioRecorder } from "react-native-audio-api";

type StartProps = {
  audioContext: AudioContext;
  bufferSourceNode: AudioBufferSourceNode;
};

let recorder: AudioRecorder | null = null;
let recordingStarted = false;

export async function start({ audioContext, bufferSourceNode }: StartProps) {
  AudioManager.setAudioSessionOptions({
    iosCategory: "playAndRecord",
    iosMode: "spokenAudio",
    iosOptions: ["defaultToSpeaker", "allowBluetoothA2DP"],
  });

  recorder = new AudioRecorder({
    sampleRate: 44100,
    bufferLengthInSamples: 44100 * 40,
  });

  const adapter = audioContext.createRecorderAdapter();
  adapter.connect(audioContext.destination);

  bufferSourceNode.onPositionChanged = (time) => {
    if (!recordingStarted && recorder) {
      recorder.start();
      recordingStarted = true;
      console.log("Recorder started at time", time.value);
    }
  };

  bufferSourceNode.onPositionChangedInterval = 1;

  bufferSourceNode.connect(audioContext.destination);

  await audioContext.resume();

  bufferSourceNode.start();
}

This works, but using onPositionChanged looks more like a workaround than a real sync mechanism.

Do you have any best practice ?

Thank you

[mdydek]

hey, can you tell us exactly, why calling sequentially

recorder.start();
bufferSourceNode.start();

not suits you? We are aware that they are not started exactly in sync in this scenario (possible ~1ms starting time mismatch), but the difference for me is neglectable, maybe we missed something.