RTCRtpSendParameters - Web APIs
degradationpreference specifies the preferred way the webrtc layer should handle optimizing bandwidth against quality in constrained-bandwidth situations; the value comes from the rtcdegradationpreference enumerated string type, and the default is balanced.

RTCRtpSender.setParameters() - Web APIs
the available options are: degradationpreference specifies the preferred way the webrtc layer should handle optimizing bandwidth against quality in constrained-bandwidth situations; the value comes from the rtcdegradationpreference enumerated string type, and the default is balanced.