How do I record a MediaStream without using MediaRecorder?

Question

So I made this node js server that will act as another peer that will join a room and will gather all the streams, But I am not able to find any way of converting this stream into a webm or any audio file.

    peers[connUserSocketId].on('stream', (stream) => {
      console.log('new stream came');
      streams = [...streams, stream];
    });