RTCTrackEventInit.receiver

The RTCTrackEventInit dictionary's receiver property specifies the RTCRtpReceiver associated with the event.

var trackEventInit = {
  receiver: rtpReceiver,
  track: mediaStreamTrack,
  streams: [videoStream],
  transceiver: rtpTransceiver
};

var rtpReceiver = trackEventInit.receiver;

The RTCRtpTransceiver which pairs the receiver with a sender and other properties which establish a single bidirectional SRTP stream for use by the track associated with the RTCTrackEvent.