RTCOutboundRtpStreamStats: trackId property
The trackId property of the RTCOutboundRtpStreamStats dictionary indicates the id of the RTCSenderAudioTrackAttachmentStats or RTCSenderVideoTrackAttachmentStats object representing the MediaStreamTrack which is being sent on this stream.
 
Value
A string containing the ID of the RTCSenderAudioTrackAttachmentStats or RTCSenderVideoTrackAttachmentStats object representing the track which is the source of the media being sent on this stream.
 
Specifications
Browser compatibility