the connected RTCPeerConnection addTransceiver() trigger onnegotiationneeded . after negotiation,new track donot play.

[DehaiWang]

I user Chrome 86.0.4240.111.
I code as like examples "broadcast",but the speakers are more than one .

when the new speaker join in the room, the connected RTCPeerConnection in browser side addTransceiver('video') , browser side trigger onnegotiationneeded , browser side createOffer(),setLocalDescription(),sent offer to the server side.

the connected RTCPeerConnection in server side receive the offer, addTrack(), SetRemoteDescription() , CreateAnswer(), SetLocalDescription(),and send LocalDescription() to browser side.

the connected RTCPeerConnection in browser side receive the answer, setRemoteDescription(),and the new negotiation complete.

After negotiation,the connected RTCPeerConnection in browser side trigger ontrack,and js document.createElement('video'),but the new track video donot play,it is black.

[prncvrm]

anyone any leads on this?