Hi, I've been working with @Aul16 on a project that requires audio-only recording using the sip_ua package. He implemented it for the Android platform in Java and after thorough testing, it works as a charm. It produces a MP3 file.

Here is some demo code that is now possible on a SIP/WebRTC audio call:

// On call start
final recorder = MediaRecorder();
await recorder.start(
  path,
  audioChannel: RecorderAudioChannel.INPUT, // or RecorderAudioChannel.OUTPUT
);
// On call stop
await recorder.stop();

Here, "on call start" means in sip_ua something like

call.peerConnection!.onAddStream = (MediaStream stream) async {
  // Add a small delay to ensure the stream is fully established
  await Future.delayed(const Duration(milliseconds: 500));
  await startRecording(); // apparently the stream parameter is not needed
}

and "on call stop" means something like

// in a SipUaHelperListener's callStateChanged
if (state.state == CallStateEnum.FAILED || state.state == CallStateEnum.ENDED) {
  stopRecording();
}

We also tested using multiple MediaRecorder instances at once, one on RecorderAudioChannel.INPUT and one on RecorderAudioChannel.OUTPUT (for the both sides of a phone call), and it apparently doesn't cause any problems.

Note that we didn't make any automated tests and that there is still no implementation for other platforms than Android.