getUserMedia(constrains).then(stream => {
var recorder = new MediaRecorder(stream)
})
recorder.start()
recorder.pause()
// get new stream getUserMedia(constrains_new)
// how to update recorder stream here?
recorder.resume()
Is it possible? I've try to create MediaStream and use addTrack and removeTrack methods to change stream tracks but no success (recorder stops when I try to resume it with updated stream)
Any ideas?
The short answer is no, it's not possible. The MediaStream recording spec explicitly describes this behavior: https://w3c.github.io/mediacapture-record/#dom-mediarecorder-start. It's bullet point 15.3 of that algorithm which says "If at any point, a track is added to or removed from stream’s track set, the UA MUST immediately stop gathering data ...".
But in case you only want to record audio you can probably use an AudioContext to proxy your streams. Create a MediaStreamAudioDestinationNode and use the stream that it provides for recording. Then you can feed your streams with MediaStreamAudioSourceNodes and/or MediaStreamTrackAudioSourceNodes into the audio graph and mix them in any way you desire.
Last but not least there are currently plans to add the functionality you are looking for to the spec. Maybe you just have to wait a bit. Or maybe a bit longer depending on the browser you are using. :-)