replaceTrack only works once

I’m looking at implementing a “switch between front and rear camera” feature.

When user taps a button to switch the camera:

• I run navigator.mediaDevices.getUserMedia with appropriate constraint
• when getUserMedia returns a stream I run replaceTrack like so:

navigator.mediaDevices.getUserMedia({
    video: { facingMode: facingMode },
    audio: true
}).then(function(stream) {
    if (p && localStream) {
        p.replaceTrack(localStream.getVideoTracks()[0], stream.getVideoTracks()[0], localStream);
        console.log("Done");
    }

    localStream = stream;
}).catch(() => {})

In the example, p is a Peer instance, and localStream is a local variable that keeps track of the current local stream. The above works, but only once. When I try to switch camera the second time, the replaceTrack doesn’t return (the console.logstatement doesn’t run), and there are no errors logged in console.

Am I using it wrong? Is there an example of an idiomatic use of replaceTrack?

[cuu508]

Thanks for the suggestion! I had previously tried to use addStream(), but couldn’t get it to work – I have a hunch that’s because of my super-simplistic messaging layer which doesn’t handle bursts of messages well.

But back to the topic, I think it would be great if there was an example of replaceTrack() usage in README, with a note about what can and should go in the third parameter.

[EdoardoEntusiasta]

I had a similar issue and managed to solve this way

First I replace the track peer.replaceTrack(self.user.stream.getVideoTracks()[0], stream.getVideoTracks()[0], self.user.stream); Then I remove the track from my current local stream mystream.removeTrack(self.user.stream.getVideoTracks()[0]) And finally add the new track to my visible stream mystream.addTrack(stream.getVideoTracks()[0])

My error was that I was removing the track from the current local stream before replacing it in the peer, receiving the infamous error: “Cannot replace a track that was never added”