The maxFramerate property of the RTCRtpEncodingParameters dictionary specifies the maximum framerate that can be used to send the encoding, in frames per second.
The user agent is free to allocate bandwidth between the encodings, as long as the maxFramerate value is not exceeded.
The frame rate is a positive real number (RTCPeerConnection.addTransceiver() and RTCRtpSender.setParameters() will throw a RangeError exception if the value is less than 0.0). Setting the maximum frame rate to zero using RTCRtpSender.setParameters() has the effect of freezing the video on the next frame.