RTCCodecStats
The RTCCodecStats
dictionary of the WebRTC API provides statistics about a codec used by RTP streams that are being sent or received by the associated RTCPeerConnection
object.
These statistics can be obtained by iterating the RTCStatsReport
object returned by RTCPeerConnection.getStats()
until you find an entry with the type
of codec
.
The codec statistics can be correlated with the inbound or outbound stream statistics (both local and remote) by matching their codecId
property to the codec's id
.
For example, if RTCInboundRtpStreamStats.codecId
matches an RTCCodecStats.id
in the same report, then we know that the codec is being used on this peer connection's inbound stream.
If no stream codecId
references a codec statistic, then that codec statistic object is deleted — if the codec is used again, the statistics object will be recreated with the same id
.
Codec objects may be referenced by multiple RTP streams in media sections using the same transport.
In fact, user agents are expected to consolidate information into a single "codec" entry per payload type per transport (unless sdpFmtpLine is different when sending or receiving, in which case, different codecs will be needed for encoding and decoding).
Note that other transports will use their own distinct RTCCodecStats
objects.
Instance properties
channels
Optional-
A positive number indicating the number of channels supported by the codec.
clockRate
Optional-
A positive number containing the media sampling rate.
mimeType
-
A string containing the media MIME type/subtype, such as video/VP8.
payloadType
-
A positive integer value in the range of 0 to 127 indicating the payload type used in RTP encoding or decoding.
sdpFmtpLine
Optional-
A string containing the format-specific parameters of the
"a=fmtp"
line in the codec's SDP (if present). transportId
-
A string containing the unique identifier of the transport on which this codec is being used. This can be used to match to the corresponding
RTCTransportStats
object.
Common instance properties
The following properties are common to all WebRTC statistics objects (see RTCStatsReport
for more information):
id
-
A string that uniquely identifies the object that is being monitored to produce this set of statistics.
timestamp
-
A
DOMHighResTimeStamp
object indicating the time at which the sample was taken for this statistics object. type
-
A string with the value
"codec"
, indicating the type of statistics the object contains.
Examples
Given a variable myPeerConnection
, which is an instance of RTCPeerConnection
, the code below uses await
to wait for the statistics report, and then iterates it using RTCStatsReport.forEach()
.
It then filters the dictionaries for just those reports that have the type of codec
and logs the result.
const stats = await myPeerConnection.getStats();
stats.forEach((report) => {
if (report.type === "codec") {
// Log the codec information
console.log(report);
}
});
Specifications
Specification |
---|
Identifiers for WebRTC's Statistics API # dom-rtcstatstype-codec |
Browser compatibility
BCD tables only load in the browser
See also
RTCStatsReport
codecs
option in parameter passed toRTCRtpTransceiver.setCodecPreferences()
andRTCRtpSender.setParameters()()
.codecs
property in object returned byRTCRtpSender.getParameters()
andRTCRtpReceiver.getParameters()
.