The kind property of the RTCOutboundRtpStreamStats dictionary is a string indicating whether the described RTP stream contains audio or video media.
This string will always be the same as the kind of the MediaStreamTrack object carried by the stream. It will also match the media type of the codec associated with this statistics objects (i.e., the MIME type of the associated codec's RTCCodecStats.mimeType property).
The kind is always one of: