RTCRtpCodecParameters dictionary, part of the WebRTC API, is used to describe the configuration parameters for a single media codec . In addition to being the type of the RTCRtpParameters.codecs property, it's used when calling RTCRtpTransceiver.setCodecPreferences() to configure a transceiver's codecs before beginning the offer/answer process to establish a WebRTC peer connection.

Most of the fields in this property take values which are defined and maintained by the Internet Assigned Numbers Authority (IANA). References to relevant IANA documents are provided in the see also section at the end of this article.


payloadType 可选
RTP payload type used to identify this codec.
mimeType 可选
The codec's MIME media type and subtype specified as a DOMString of the form "type/subtype" . IANA maintains a registry of valid MIME types .
clockRate 可选
An unsigned long integer value specifying the codec's clock rate in hertz (Hz). The clock rate is the rate at which the codec's RTP timestamp advances. Most codecs have specific values or ranges of values they permit; see the IANA payload format media type registry 了解细节。
channels 可选
An unsigned short integer indicating the number of channels the codec should support. For example, for audio codecs, a value of 1 specifies monaural sound while 2 indicates stereo.
sdpFmtpLine 可选
A DOMString containing the format-specific parameters field from the "a=fmtp" line in the codec's SDP , if one is present; see section 5.8 of the IETF specification for JSEP .
注意: On an RTCRtpReceiver , the format-specific parameters come from the SDP sent by the remote peer, while for RTCRtpSender , they're provided by the local description.


Real-Time Transport Protocol (RTP) Parameters
The IANA document providing registries of permitted values for the RTP parameters used by this dictionary.