Adding an AudioTrack while the MediaRecorder is in state 'recording'

Question

Im trying to add mediaTrack to the mediaStream while MediaRecorder is in state 'recording'

The code for adding a new track is the following:

activeStream.addTrack(newAudioTrack)

After that the event (onstop) was triggered. How can I avoid this?

Answer 1

You can use an AudioContext to create a fixed MediaStream that you can pass to the MediaRecorder. This allows you to change the input when recording.

const audioContext = new AudioContext();
const mediaStreamAudioDestinationNode = new MediaStreamAudioDestinationNode(audioContext);
const mediaRecorder = new MediaRecorder(mediaStreamAudioDestinationNode.stream);

Let's say you have a MediaStream called initialMediaStream. You could connect it like that:

const mediaStreamAudioSourceNode = new MediaStreamAudioSourceNode(
    audioContext,
    { mediaStream: initialMediaStream }
);

mediaStreamAudioSourceNode.connect(mediaStreamAudioDestinationNode);

You can then start recording the initialMediaStream.

mediaRecorder.start();

Later on you can replace the initialMediaStream with anotherMediaStream.

const anotherMediaStreamAudioSourceNode = new MediaStreamAudioSourceNode(
    audioContext,
    { mediaStream: anotherMediaStream }
);

anotherMediaStreamAudioSourceNode.connect(mediaStreamAudioDestinationNode);
mediaStreamAudioSourceNode.disconnect();

You could even use GainNodes to apply a cross-fade between the two streams if that's what you want.