The payloadType property of the RTCCodecStats dictionary is a positive integer in the range from 0 to 127 that describes the format of the RTP payload used in RTP encoding or decoding.
A positive integer between 0 and 127.
The mappings of values to formats is defined in RFC3550, and more specifically in Section 6: Payload Type Definitions of RFC3551.
payloadType returned by RTCEncodedAudioFrame.getMetadata()payloadType returned by RTCEncodedVideoFrame.getMetadata()codecs.payloadType option in parameter passed to RTCRtpSender.setParameters().codecs.payloadType in object returned by RTCRtpSender.getParameters() and RTCRtpReceiver.getParameters().