Getting started with remote streams

Once a RTCPeerConnection is connected to a remote peer, it is possible to stream audio and video between them. This is the point where we connect the stream we receive from getUserMedia() to the RTCPeerConnection. A media stream consists of at least one media track, and these are individually added to the RTCPeerConnection when we want to transmit the media to the remote peer.

const localStream = await getUserMedia({vide: true, audio: true});
const peerConnection = new RTCPeerConnection(iceConfig);
localStream.getTracks().forEach(track => {
    peerConnection.addTrack(track, localStream);
});

Tracks can be added to a RTCPeerConnection before it has connected to a remote peer, so it makes sense to perform this setup as early as possible instead of waiting for the connection to be completed.

Adding remote tracks

To receive the remote tracks that were added by the other peer, we register a listener on the local RTCPeerConnection listening for the track event. The RTCTrackEvent contains an array of MediaStream objects that have the same MediaStream.id values as the peer's corresponding local streams. In our example, each track is only associated with a single stream.

Note that while MediaStream IDs match on both sides of the peer connection, the same is generally not true for MediaStreamTrack IDs.

const remoteVideo = document.querySelector('#remoteVideo');

peerConnection.addEventListener('track', async (event) => {
    const [remoteStream] = event.streams;
    remoteVideo.srcObject = remoteStream;
});