rtcloopbackhack.js

let rtcConnection = null;
let rtcLoopbackConnection = null;
let loopbackStream = new MediaStream(); // this is the stream you will read from for actual audio output

const offerOptions = {
  offerVideo: true,
  offerAudio: true,
  offerToReceiveAudio: false,
  offerToReceiveVideo: false,
};

let offer, answer;

// initialize the RTC connections

this.rtcConnection = new RTCPeerConnection();
this.rtcLoopbackConnection = new RTCPeerConnection();

this.rtcConnection.onicecandidate = e =>
  e.candidate && this.rtcLoopbackConnection.addIceCandidate(new RTCIceCandidate(e.candidate));
this.rtcLoopbackConnection.onicecandidate = e =>
  e.candidate && this.rtcConnection.addIceCandidate(new RTCIceCandidate(e.candidate));

this.rtcLoopbackConnection.ontrack = e =>
  e.streams[0].getTracks().forEach(track => this.loopbackStream.addTrack(track));


// setup the loopback
this.rtcConnection.addStream(stream); // this stream would be the processed stream coming out of Web Audio API destination node

offer = await this.rtcConnection.createOffer(offerOptions);
await this.rtcConnection.setLocalDescription(offer);

await this.rtcLoopbackConnection.setRemoteDescription(offer);
answer = await this.rtcLoopbackConnection.createAnswer();
await this.rtcLoopbackConnection.setLocalDescription(answer);

await this.rtcConnection.setRemoteDescription(answer);

@alexciarlillo can you give me some demo which can run as webpage?

@liyoubdu sorry I do not have time to do this right now (I am just returning to work after paternity leave and have much to catch up on). But if you do come up with a single page working example please do share it back here for others to reference.