Identifiers for WebRTC's Statistics API

Dictionary RTCRtpStreamStats Members

ssrc of type unsigned long

The 32-bit unsigned integer value per [RFC3550] used to identify the source of the stream of RTP packets that this stats object concerns.

kind of type DOMString

Either "audio" or "video". This MUST match the media type part of the information in the corresponding codecType member of RTCCodecStats, and MUST match the "kind" attribute of the related MediaStreamTrack.

transportId of type DOMString

It is a unique identifier that is associated to the object that was inspected to produce the RTCTransportStats associated with this RTP stream.

codecId of type DOMString

It is a unique identifier that is associated to the object that was inspected to produce the RTCCodecStats associated with this RTP stream.

Dictionary RTCCodecStats Members

payloadType of type unsigned long

Payload type as used in RTP encoding or decoding.

codecType of type RTCCodecType

"encode" or "decode", depending on whether this object represents a media format that the implementation is prepared to encode or decode.

transportId of type DOMString

The unique identifier of the transport on which this codec is being used, which can be used to look up the corresponding RTCTransportStats object.

mimeType of type DOMString

The codec MIME media type/subtype. e.g., video/vp8 or equivalent.

clockRate of type unsigned long

Represents the media sampling rate.

channels of type unsigned long

Use 2 for stereo, missing for most other cases.

sdpFmtpLine of type DOMString

The a=fmtp line in the SDP corresponding to the codec, i.e., after the colon following the PT. This defined by [JSEP] in Section 5.7.

Dictionary RTCReceivedRtpStreamStats Members

packetsReceived of type unsigned long long

Total number of RTP packets received for this SSRC. At the receiving endpoint, this is calculated as defined in [RFC3550] section 6.4.1. At the sending endpoint the packetsReceived can be calculated by subtracting the packets lost from the expected Highest Sequence Number reported in the RTCP Sender Report as discussed in Appendix A.3. in [RFC3550].

packetsLost of type long long

Total number of RTP packets lost for this SSRC. Calculated as defined in [RFC3550] section 6.4.1. Note that because of how this is estimated, it can be negative if more packets are received than sent.

jitter of type double

Packet Jitter measured in seconds for this SSRC. Calculated as defined in section 6.4.1. of [RFC3550].

packetsDiscarded of type unsigned long long

The cumulative number of RTP packets discarded by the jitter buffer due to late or early-arrival, i.e., these packets are not played out. RTP packets discarded due to packet duplication are not reported in this metric [XRBLOCK-STATS]. Calculated as defined in [RFC7002] section 3.2 and Appendix A.a.

packetsRepaired of type unsigned long long

The cumulative number of lost RTP packets repaired after applying an error-resilience mechanism [XRBLOCK-STATS]. It is measured for the primary source RTP packets and only counted for RTP packets that have no further chance of repair. To clarify, the value is upper-bound to the cumulative number of lost packets. Calculated as defined in [RFC7509] section 3.1 and Appendix A.b.

burstPacketsLost of type unsigned long long

The cumulative number of RTP packets lost during loss bursts, Appendix A (c) of [RFC6958].

burstPacketsDiscarded of type unsigned long long

The cumulative number of RTP packets discarded during discard bursts, Appendix A (b) of [RFC7003].

burstLossCount of type unsigned long

The cumulative number of bursts of lost RTP packets, Appendix A (e) of [RFC6958].

[RFC3611] recommends a Gmin (threshold) value of 16 for classifying a sequence of packet losses or discards as a burst.

burstDiscardCount of type unsigned long

The cumulative number of bursts of discarded RTP packets, Appendix A (e) of [RFC8015].

burstLossRate of type double

The fraction of RTP packets lost during bursts to the total number of RTP packets expected in the bursts. As defined in Appendix A (a) of [RFC7004], however, the actual value is reported without multiplying by 32768.

burstDiscardRate of type double

The fraction of RTP packets discarded during bursts to the total number of RTP packets expected in bursts. As defined in Appendix A (e) of [RFC7004], however, the actual value is reported without multiplying by 32768.

gapLossRate of type double

The fraction of RTP packets lost during the gap periods. Appendix A (b) of [RFC7004], however, the actual value is reported without multiplying by 32768.

gapDiscardRate of type double

The fraction of RTP packets discarded during the gap periods. Appendix A (f) of [RFC7004], however, the actual value is reported without multiplying by 32768.

framesDropped of type unsigned long

Only valid for video. The total number of frames dropped prior to decode or dropped because the frame missed its display deadline for this receiver's track. The measurement begins when the receiver is created and is a cumulative metric as defined in Appendix A (g) of [RFC7004].

partialFramesLost of type unsigned long

Only valid for video. The cumulative number of partial frames lost. The measurement begins when the receiver is created and is a cumulative metric as defined in Appendix A (j) of [RFC7004]. This metric is incremented when the frame is sent to the decoder. If the partial frame is received and recovered via retransmission or FEC before decoding, the framesReceived counter is incremented.

fullFramesLost of type unsigned long

Only valid for video. The cumulative number of full frames lost. The measurement begins when the receiver is created and is a cumulative metric as defined in Appendix A (i) of [RFC7004].

Dictionary RTCInboundRtpStreamStats Members

trackId of type DOMString

The identifier of the stats object representing the receiving track, an RTCReceiverAudioTrackAttachmentStats or RTCReceiverVideoTrackAttachmentStats.

receiverId of type DOMString

The stats ID used to look up the RTCAudioReceiverStats or RTCVideoReceiverStats object receiving this stream.

remoteId of type DOMString

The remoteId is used for looking up the remote RTCRemoteOutboundRtpStreamStats object for the same SSRC.

framesDecoded

Only valid for video. It represents the total number of frames correctly decoded for this RTP stream, i.e., frames that would be displayed if no frames are dropped.

keyFramesDecoded of type unsigned long

Only valid for video. It represents the total number of key frames, such as key frames in VP8 [RFC6386] or IDR-frames in H.264 [RFC6184], successfully decoded for this RTP media stream. This is a subset of framesDecoded. framesDecoded - keyFramesDecoded gives you the number of delta frames decoded.

frameWidth of type unsigned long

Only valid for video. Represents the width of the last decoded frame. Before the first frame is decoded this attribute is missing.

frameHeight of type unsigned long

Only valid for video. Represents the height of the last decoded frame. Before the first frame is decoded this attribute is missing.

frameBitDepth of type unsigned long

Only valid for video. Represents the bit depth per pixel of the last decoded frame. Typical values are 24, 30, or 36 bits. Before the first frame is decoded this attribute is missing.

framesPerSecond of type double

Only valid for video. The number of decoded frames in the last second.

qpSum of type unsigned long long

Only valid for video. The sum of the QP values of frames decoded by this receiver. The count of frames is in framesDecoded.

The definition of QP value depends on the codec; for VP8, the QP value is the value carried in the frame header as the syntax element "y_ac_qi", and defined in [RFC6386] section 19.2. Its range is 0..127.

Note that the QP value is only an indication of quantizer values used; many formats have ways to vary the quantizer value within the frame.

totalDecodeTime of type double

Total number of seconds that have been spent decoding the framesDecoded frames of this stream. The average decode time can be calculated by dividing this value with framesDecoded. The time it takes to decode one frame is the time passed between feeding the decoder a frame and the decoder returning decoded data for that frame.

totalInterFrameDelay of type double

Sum of the interframe delays in seconds between consecutively decoded frames, recorded just after a frame has been decoded. The interframe delay variance be calculated from totalInterFrameDelay, totalSquaredInterFrameDelay, and framesDecoded according to the formula: (totalSquaredInterFrameDelay - totalInterFrameDelay^2/ framesDecoded)/framesDecoded.

totalSquaredInterFrameDelay of type double

Sum of the squared interframe delays in seconds between consecutively decoded frames, recorded just after a frame has been decoded. See totalInterFrameDelay for details on how to calculate the interframe delay variance.

voiceActivityFlag of type boolean

Only valid for audio. Whether the last RTP packet whose frame was delivered to the RTCRtpReceiver's MediaStreamTrack for playout contained voice activity or not based on the presence of the V bit in the extension header, as defined in [RFC6464]. This is the stats-equivalent of RTCRtpSynchronizationSource.voiceActivityFlag in [[WEBRTC].

lastPacketReceivedTimestamp of type DOMHighResTimeStamp

Represents the timestamp at which the last packet was received for this SSRC. This differs from timestamp, which represents the time at which the statistics were generated by the local endpoint.

averageRtcpInterval of type double

The average RTCP interval between two consecutive compound RTCP packets. This is calculated by the sending endpoint when sending compound RTCP reports. Compound packets must contain at least a RTCP RR or SR block and an SDES packet with the CNAME item.

headerBytesReceived of type unsigned long long

Total number of RTP header and padding bytes received for this SSRC. This does not include the size of transport layer headers such as IP or UDP. headerBytesReceived + bytesReceived equals the number of bytes received as payload over the transport.

fecPacketsReceived of type unsigned long long

Total number of RTP FEC packets received for this SSRC. This counter can also be incremented when receiving FEC packets in-band with media packets (e.g., with Opus).

fecPacketsDiscarded of type unsigned long long

Total number of RTP FEC packets received for this SSRC where the error correction payload was discarded by the application. This may happen 1. if all the source packets protected by the FEC packet were received or already recovered by a separate FEC packet, or 2. if the FEC packet arrived late, i.e., outside the recovery window, and the lost RTP packets have already been skipped during playout. This is a subset of fecPacketsReceived.

bytesReceived of type unsigned long long

Total number of bytes received for this SSRC. Calculated as defined in [RFC3550] section 6.4.1.

packetsFailedDecryption of type unsigned long long

The cumulative number of RTP packets that failed to be decrypted according to the procedures in [RFC3711]. These packets are not counted by packetsDiscarded.

packetsDuplicated of type unsigned long long

The cumulative number of packets discarded because they are duplicated. Duplicate packets are not counted in packetsDiscarded.
Duplicated packets have the same RTP sequence number and content as a previously received packet. If multiple duplicates of a packet are received, all of them are counted.
An improved estimate of lost packets can be calculated by adding packetsDuplicated to packetsLost; this will always result in a positive number, but not the same number as RFC 3550 would calculate.

perDscpPacketsReceived of type record<USVString, unsigned long long>

Total number of packets received for this SSRC, per Differentiated Services code point (DSCP) [RFC2474]. DSCPs are identified as decimal integers in string form. Note that due to network remapping and bleaching, these numbers are not expected to match the numbers seen on sending. Not all OSes make this information available.

firCount of type unsigned long

Only valid for video. Count the total number of Full Intra Request (FIR) packets sent by this receiver. Calculated as defined in [RFC5104] section 4.3.1. and does not use the metric indicated in [RFC2032], because it was deprecated by [RFC4587].

pliCount of type unsigned long

Only valid for video. Count the total number of Picture Loss Indication (PLI) packets sent by this receiver. Calculated as defined in [RFC4585] section 6.3.1.

nackCount of type unsigned long

Count the total number of Negative ACKnowledgement (NACK) packets sent by this receiver. Calculated as defined in [RFC4585] section 6.2.1.

sliCount of type unsigned long

Only valid for video. Count the total number of Slice Loss Indication (SLI) packets sent by this receiver. Calculated as defined in [RFC4585] section 6.3.2.

estimatedPlayoutTimestamp of type DOMHighResTimeStamp

This is the estimated playout time of this receiver's track. The playout time is the NTP timestamp of the last playable audio sample or video frame that has a known timestamp (from an RTCP SR packet mapping RTP timestamps to NTP timestamps), extrapolated with the time elapsed since it was ready to be played out. This is the "current time" of the track in NTP clock time of the sender and can be present even if there is no audio currently playing.

This can be useful for estimating how much audio and video is out of sync for two tracks from the same source, audioTrackStats.estimatedPlayoutTimestamp - videoTrackStats.estimatedPlayoutTimestamp.

jitterBufferDelay of type double

It is the sum of the time, in seconds, each audio sample or video frame takes from the time it is received and to the time it exits the jitter buffer. This increases upon samples or frames exiting, having completed their time in the buffer (and incrementing jitterBufferEmittedCount). The average jitter buffer delay can be calculated by dividing the jitterBufferDelay with the jitterBufferEmittedCount.

Note: If multiple audio channels are used, metrics based on samples do not increment at a higher rate. "A sample" refers to having a sample in either channel - simultaneously having samples in multiple channels counts as a single sample.

jitterBufferEmittedCount of type unsigned long long

The total number of audio samples or video frames that have come out of the jitter buffer (increasing jitterBufferDelay).

Note: If multiple audio channels are used, metrics based on samples do not increment at a higher rate. "A sample" refers to having a sample in either channel - simultaneously having samples in multiple channels counts as a single sample.

totalSamplesReceived of type unsigned long long

Only valid for audio. The total number of samples that have been received on this RTP stream. This includes concealedSamples.

Note: If multiple audio channels are used, metrics based on samples do not increment at a higher rate. "A sample" refers to having a sample in either channel - simultaneously having samples in multiple channels counts as a single sample.

samplesDecodedWithSilk of type unsigned long long

Only valid for audio and when the audio codec is Opus. The total number of samples decoded by the SILK portion of the Opus codec.

samplesDecodedWithCelt of type unsigned long long

Only valid for audio and when the audio codec is Opus. The total number of samples decoded by the CELT portion of the Opus codec.

concealedSamples of type unsigned long long

Only valid for audio. The total number of samples that are concealed samples. A concealed sample is a sample that was replaced with synthesized samples generated locally before being played out. Examples of samples that have to be concealed are samples from lost packets (reported in packetsLost) or samples from packets that arrive too late to be played out (reported in packetsDiscarded).

Note: If multiple audio channels are used, metrics based on samples do not increment at a higher rate. "A sample" refers to having a sample in either channel - simultaneously having samples in multiple channels counts as a single sample.

silentConcealedSamples of type unsigned long long

Only valid for audio. The total number of concealed samples inserted that are "silent". Playing out silent samples results in silence or comfort noise. This is a subset of concealedSamples.

Note: If multiple audio channels are used, metrics based on samples do not increment at a higher rate. "A sample" refers to having a sample in either channel - simultaneously having samples in multiple channels counts as a single sample.

concealmentEvents of type unsigned long long

Only valid for audio. The number of concealment events. This counter increases every time a concealed sample is synthesized after a non-concealed sample. That is, multiple consecutive concealed samples will increase the concealedSamples count multiple times but is a single concealment event.

Note: If multiple audio channels are used, metrics based on samples do not increment at a higher rate. "A sample" refers to having a sample in either channel - simultaneously having samples in multiple channels counts as a single sample.

insertedSamplesForDeceleration of type unsigned long long

Only valid for audio. When playout is slowed down, this counter is increased by the difference between the number of samples received and the number of samples played out. If playout is slowed down by inserting samples, this will be the number of inserted samples.

Note: If multiple audio channels are used, metrics based on samples do not increment at a higher rate. "A sample" refers to having a sample in either channel - simultaneously having samples in multiple channels counts as a single sample.

removedSamplesForAcceleration of type unsigned long long

Only valid for audio. When playout is sped up, this counter is increased by the difference between the number of samples received and the number of samples played out. If speedup is achieved by removing samples, this will be the count of samples removed.

Note: If multiple audio channels are used, metrics based on samples do not increment at a higher rate. "A sample" refers to having a sample in either channel - simultaneously having samples in multiple channels counts as a single sample.

audioLevel of type double

Only valid for audio. Represents the audio level of the receiving track. For audio levels of tracks attached locally, see RTCAudioSourceStats instead.

The value is between 0..1 (linear), where 1.0 represents 0 dBov, 0 represents silence, and 0.5 represents approximately 6 dBSPL change in the sound pressure level from 0 dBov.

The audioLevel is averaged over some small interval, using the algortihm described under totalAudioEnergy. The interval used is implementation dependent.

totalAudioEnergy of type double

Only valid for audio. Represents the audio energy of the receiving track. For audio energy of tracks attached locally, see RTCAudioSourceStats instead.

This value MUST be computed as follows: for each audio sample that is received (and thus counted by totalSamplesReceived), add the sample's value divided by the highest-intensity encodable value, squared and then multiplied by the duration of the sample in seconds. In other words, duration * Math.pow(energy/maxEnergy, 2).

This can be used to obtain a root mean square (RMS) value that uses the same units as audioLevel, as defined in [RFC6464]. It can be converted to these units using the formula Math.sqrt(totalAudioEnergy/totalSamplesDuration). This calculation can also be performed using the differences between the values of two different getStats() calls, in order to compute the average audio level over any desired time interval. In other words, do Math.sqrt((energy2 - energy1)/(duration2 - duration1)).

For example, if a 10ms packet of audio is produced with an RMS of 0.5 (out of 1.0), this should add 0.5 * 0.5 * 0.01 = 0.0025 to totalAudioEnergy. If another 10ms packet with an RMS of 0.1 is received, this should similarly add 0.0001 to totalAudioEnergy. Then, Math.sqrt(totalAudioEnergy/totalSamplesDuration) becomes Math.sqrt(0.0026/0.02) = 0.36, which is the same value that would be obtained by doing an RMS calculation over the contiguous 20ms segment of audio.

Note: If multiple audio channels are used, metrics based on samples do not increment at a higher rate. "A sample" refers to having a sample in either channel - simultaneously having samples in multiple channels counts as a single sample. The "audio energy of a sample" refers to the highest energy of any channel.

totalSamplesDuration of type double

Only valid for audio. Represents the audio duration of the receiving track. For audio durations of tracks attached locally, see RTCAudioSourceStats instead.

Represents the total duration in seconds of all samples that have been received (and thus counted by totalSamplesReceived). Can be used with totalAudioEnergy to compute an average audio level over different intervals.

Note: If multiple audio channels are used, metrics based on samples do not increment at a higher rate. "A sample" refers to having a sample in either channel - simultaneously having samples in multiple channels counts as a single sample.

framesReceived of type unsigned long

Only valid for video. Represents the total number of complete frames received on this RTP stream. This metric is incremented when the complete frame is received.

decoderImplementation of type DOMString

Identifies the decoder implementation used. This is useful for diagnosing interoperability issues.

If too much information is given here, it increases the fingerprint surface. Since it is only given for active tracks, the incremental exposure is small.

Dictionary RTCRemoteInboundRtpStreamStats Members

localId of type DOMString

The localId is used for looking up the local RTCOutboundRtpStreamStats object for the same SSRC.

roundTripTime of type double

Estimated round trip time for this SSRC based on the RTCP timestamps in the RTCP Receiver Report (RR) and measured in seconds. Calculated as defined in section 6.4.1. of [RFC3550]. If no RTCP Receiver Report is received with a DLSR value other than 0, the round trip time is left undefined.

totalRoundTripTime of type double

Represents the cumulative sum of all round trip time measurements in seconds since the beginning of the session. The individual round trip time is calculated based on the RTCP timestamps in the RTCP Receiver Report (RR) [RFC3550], hence undefined roundtrip are not added. The average round trip time can be computed from totalRoundTripTime by dividing it by roundTripTimeMeasurements.

fractionLost of type double

The fraction packet loss reported for this SSRC. Calculated as defined in [RFC3550] section 6.4.1 and Appendix A.3.

reportsReceived of type unsigned long long

Represents the total number of RTCP RR blocks received for this SSRC.

roundTripTimeMeasurements of type unsigned long long

Represents the total number of RTCP RR blocks received for this SSRC that contain a valid round trip time. This counter will increment if the roundTripTime is undefined.

Dictionary RTCSentRtpStreamStats Members

packetsSent of type unsigned long long

Total number of RTP packets sent for this SSRC. Calculated as defined in [RFC3550] section 6.4.1.

bytesSent of type unsigned long long

Total number of bytes sent for this SSRC. Calculated as defined in [RFC3550] section 6.4.1.

Dictionary RTCOutboundRtpStreamStats Members

trackId of type DOMString

The identifier of the stats object representing the current track attachment to the sender of this stream, an RTCSenderAudioTrackAttachmentStats or RTCSenderVideoTrackAttachmentStats.

mediaSourceId of type DOMString

The identifier of the stats object representing the track currently attached to the sender of this stream, an RTCMediaSourceStats.

senderId of type DOMString

The stats ID used to look up the RTCAudioSenderStats or RTCVideoSenderStats object sending this stream.

remoteId of type DOMString

The remoteId is used for looking up the remote RTCRemoteInboundRtpStreamStats object for the same SSRC.

rid of type DOMString

Exposes the rid encoding parameter of this RTP stream if it has been set, otherwise it is undefined. If set this value will be present regardless if the RID RTP header extension has been negotiated.

lastPacketSentTimestamp of type DOMHighResTimeStamp

Represents the timestamp at which the last packet was sent for this SSRC. This differs from timestamp, which represents the time at which the statistics were generated by the local endpoint.

headerBytesSent of type unsigned long long

Total number of RTP header and padding bytes sent for this SSRC. This does not include the size of transport layer headers such as IP or UDP. headerBytesSent + bytesSent equals the number of bytes sent as payload over the transport.

packetsDiscardedOnSend of type unsigned long

Total number of RTP packets for this SSRC that have been discarded due to socket errors, i.e. a socket error occured when handing the packets to the socket. This might happen due to various reasons, including full buffer or no available memory.

bytesDiscardedOnSend of type unsigned long long

Total number of bytes for this SSRC that have been discarded due to socket errors, i.e. a socket error occured when handing the packets containing the bytes to the socket. This might happen due to various reasons, including full buffer or no available memory. Calculated as defined in [RFC3550] section 6.4.1.

fecPacketsSent of type unsigned long

Total number of RTP FEC packets sent for this SSRC. This counter can also be incremented when sending FEC packets in-band with media packets (e.g., with Opus).

retransmittedPacketsSent of type unsigned long long

The total number of packets that were retransmitted for this SSRC. This is a subset of packetsSent.

retransmittedBytesSent of type unsigned long long

The total number of bytes that were retransmitted for this SSRC, only including payload bytes. This is a subset of bytesSent.

targetBitrate of type double

It is the current target bitrate configured for this particular SSRC and is the Transport Independent Application Specific (TIAS) bitrate [RFC3890]. Typically, the target bitrate is a configuration parameter provided to the codec's encoder and does not count the size of the IP or other transport layers like TCP or UDP. It is measured in bits per second and the bitrate is calculated over a 1 second window.

totalEncodedBytesTarget of type unsigned long long

This value is increased by the target frame size in bytes every time a frame has been encoded. The actual frame size may be bigger or smaller than this number. This value goes up every time framesEncoded goes up.

frameWidth of type unsigned long

Only valid for video. Represents the width of the last encoded frame. The resolution of the encoded frame may be lower than the media source (see RTCVideoSourceStats.width). Before the first frame is encoded this attribute is missing.

frameHeight of type unsigned long

Only valid for video. Represents the height of the last encoded frame. The resolution of the encoded frame may be lower than the media source (see RTCVideoSourceStats.height). Before the first frame is encoded this attribute is missing.

frameBitDepth of type unsigned long

Only valid for video. Represents the bit depth per pixel of the last encoded frame. Typical values are 24, 30, or 36 bits. Before the first frame is encoded this attribute is missing.

framesPerSecond of type double

Only valid for video. The number of encoded frames during the last second. This may be lower than the media source frame rate (see RTCVideoSourceStats.framesPerSecond).

framesSent of type unsigned long

Only valid for video. Represents the total number of frames sent on this RTP stream.

hugeFramesSent of type unsigned long

Only valid for video. Represents the total number of huge frames sent by this RTP stream. Huge frames, by definition, are frames that have an encoded size at least 2.5 times the average size of the frames. The average size of the frames is defined as the target bitrate per second divided by the target FPS at the time the frame was encoded. These are usually complex to encode frames with a lot of changes in the picture. This can be used to estimate, e.g slide changes in the streamed presentation.

The multiplier of 2.5 is choosen from analyzing encoded frame sizes for a sample presentation using WebRTC standalone implementation. 2.5 is a reasonably large multiplier which still caused all slide change events to be identified as a huge frames. It, however, produced 1.4% of false positive slide change detections which is deemed reasonable.

framesEncoded of type long

Only valid for video. It represents the total number of frames successfully encoded for this RTP media stream.

keyFramesEncoded of type unsigned long

Only valid for video. It represents the total number of key frames, such as key frames in VP8 [RFC6386] or IDR-frames in H.264 [RFC6184], successfully encoded for this RTP media stream. This is a subset of framesEncoded. framesEncoded - keyFramesEncoded gives you the number of delta frames encoded.

framesDiscardedOnSend of type unsigned long

Total number of video frames that have been discarded for this SSRC due to socket errors, i.e. a socket error occured when handing the packets to the socket. This might happen due to various reasons, including full buffer or no available memory.

qpSum of type unsigned long long

Only valid for video. The sum of the QP values of frames encoded by this sender. The count of frames is in framesEncoded.

The definition of QP value depends on the codec; for VP8, the QP value is the value carried in the frame header as the syntax element "y_ac_qi", and defined in [RFC6386] section 19.2. Its range is 0..127.

Note that the QP value is only an indication of quantizer values used; many formats have ways to vary the quantizer value within the frame.

totalSamplesSent of type unsigned long long

Only valid for audio. The total number of samples that have been sent over this RTP stream.

Note: If multiple audio channels are used, metrics based on samples do not increment at a higher rate. "A sample" refers to having a sample in either channel - simultaneously having samples in multiple channels counts as a single sample.

samplesEncodedWithSilk of type unsigned long long

Only valid for audio and when the audio codec is Opus. The total number of samples encoded by the SILK portion of the Opus codec.

samplesEncodedWithCelt of type unsigned long long

Only valid for audio and when the audio codec is Opus. The total number of samples encoded by the CELT portion of the Opus codec.

voiceActivityFlag of type boolean

Only valid for audio. Whether the last RTP packet sent contained voice activity or not based on the presence of the V bit in the extension header, as defined in [RFC6464].

totalEncodeTime of type double

Total number of seconds that has been spent encoding the framesEncoded frames of this stream. The average encode time can be calculated by dividing this value with framesEncoded. The time it takes to encode one frame is the time passed between feeding the encoder a frame and the encoder returning encoded data for that frame. This does not include any additional time it may take to packetize the resulting data.

totalPacketSendDelay of type double

The total number of seconds that packets have spent buffered locally before being transmitted onto the network. The time is measured from when a packet is emitted from the RTP packetizer until it is handed over to the OS network socket. This measurement is added to totalPacketSendDelay when packetsSent is incremented.

averageRtcpInterval of type double

The average RTCP interval between two consecutive compound RTCP packets. This is calculated by the sending endpoint when sending compound RTCP reports. Compound packets must contain at least a RTCP RR or SR block and an SDES packet with the CNAME item.

qualityLimitationReason of type RTCQualityLimitationReason

Only valid for video. The current reason for limiting the resolution and/or framerate, or "none" if not limited.

qualityLimitationDurations of type record<DOMString, double>

Only valid for video. A record of the total time, in seconds, that this stream has spent in each quality limitation state. The record includes a mapping for all RTCQualityLimitationReason types, including "none".

The sum of all entries minus qualityLimidationDurations["none"] gives the total time that the stream has been limited.

qualityLimitationResolutionChanges of type unsigned long

Only valid for video. The number of times that the resolution has changed because we are quality limited (qualityLimitationReason has a value other than "none"). The counter is initially zero and increases when the resolution goes up or down. For example, if a 720p track is sent as 480p for some time and then recovers to 720p, qualityLimitationResolutionChanges will have the value 2.

perDscpPacketsSent of type record<USVString, unsigned long long>

Total number of packets sent for this SSRC, per DSCP. DSCPs are identified as decimal integers in string form.

nackCount of type unsigned long

Count the total number of Negative ACKnowledgement (NACK) packets received by this sender. Calculated as defined in [RFC4585] section 6.2.1.

firCount of type unsigned long

Only valid for video. Count the total number of Full Intra Request (FIR) packets received by this sender. Calculated as defined in [RFC5104] section 4.3.1. and does not use the metric indicated in [RFC2032], because it was deprecated by [RFC4587].

pliCount of type unsigned long

Only valid for video. Count the total number of Picture Loss Indication (PLI) packets received by this sender. Calculated as defined in [RFC4585] section 6.3.1.

sliCount of type unsigned long

Only valid for video. Count the total number of Slice Loss Indication (SLI) packets received by this sender. Calculated as defined in [RFC4585] section 6.3.2.

encoderImplementation of type DOMString

Identifies the encoder implementation used. This is useful for diagnosing interoperability issues.

If too much information is given here, it increases the fingerprint surface. Since it is only given for active tracks, the incremental exposure is small.

Dictionary RTCRemoteOutboundRtpStreamStats Members

localId of type DOMString

The localId is used for looking up the local RTCInboundRtpStreamStats object for the same SSRC.

remoteTimestamp of type DOMHighResTimeStamp

remoteTimestamp, of type DOMHighResTimeStamp [HIGHRES-TIME], represents the remote timestamp at which these statistics were sent by the remote endpoint. This differs from timestamp, which represents the time at which the statistics were generated or received by the local endpoint. The remoteTimestamp, if present, is derived from the NTP timestamp in an RTCP Sender Report (SR) block, which reflects the remote endpoint's clock. That clock may not be synchronized with the local clock.

reportsSent of type unsigned long long

Represents the total number of RTCP SR blocks sent for this SSRC.

Dictionary RTCMediaSourceStats Members

trackIdentifier of type DOMString

The value of the MediaStreamTrack's id attribute.

kind of type DOMString

The value of the MediaStreamTrack's kind attribute. This is either "audio" or "video". If it is "audio" then this stats object is of type RTCAudioSourceStats. If it is "video" then this stats object is of type RTCVideoSourceStats.

Dictionary RTCAudioSourceStats Members

audioLevel of type double

Represents the audio level of the media source. For audio levels of remotely sourced tracks, see RTCAudioReceiverStats instead.

The value is between 0..1 (linear), where 1.0 represents 0 dBov, 0 represents silence, and 0.5 represents approximately 6 dBSPL change in the sound pressure level from 0 dBov.

The audioLevel is averaged over some small interval, using the algortihm described under totalAudioEnergy. The interval used is implementation dependent.

totalAudioEnergy of type double

Represents the audio energy of the media source. For audio energy of remotely sourced tracks, see RTCAudioReceiverStats instead.

This value MUST be computed as follows: for each audio sample produced by the media source during the lifetime of this stats object, add the sample's value divided by the highest-intensity encodable value, squared and then multiplied by the duration of the sample in seconds. In other words, duration * Math.pow(energy/maxEnergy, 2).

This can be used to obtain a root mean square (RMS) value that uses the same units as audioLevel, as defined in [RFC6464]. It can be converted to these units using the formula Math.sqrt(totalAudioEnergy/totalSamplesDuration). This calculation can also be performed using the differences between the values of two different getStats() calls, in order to compute the average audio level over any desired time interval. In other words, do Math.sqrt((energy2 - energy1)/(duration2 - duration1)).

For example, if a 10ms packet of audio is produced with an RMS of 0.5 (out of 1.0), this should add 0.5 * 0.5 * 0.01 = 0.0025 to totalAudioEnergy. If another 10ms packet with an RMS of 0.1 is received, this should similarly add 0.0001 to totalAudioEnergy. Then, Math.sqrt(totalAudioEnergy/totalSamplesDuration) becomes Math.sqrt(0.0026/0.02) = 0.36, which is the same value that would be obtained by doing an RMS calculation over the contiguous 20ms segment of audio.

Note: If multiple audio channels are used, metrics based on samples do not increment at a higher rate. "A sample" refers to having a sample in either channel - simultaneously having samples in multiple channels counts as a single sample. The "audio energy of a sample" refers to the highest energy of any channel.

totalSamplesDuration of type double

Represents the audio duration of the media source. For audio durations of remotely sourced tracks, see RTCAudioReceiverStats instead.

Represents the total duration in seconds of all samples that have been produced by this source for the lifetime of this stats object. Can be used with totalAudioEnergy to compute an average audio level over different intervals.

Note: If multiple audio channels are used, metrics based on samples do not increment at a higher rate. "A sample" refers to having a sample in either channel - simultaneously having samples in multiple channels counts as a single sample.

echoReturnLoss of type double

Only present when the MediaStreamTrack is sourced from a microphone where echo cancellation is applied. Calculated in decibels, as defined in [ECHO] (2012) section 3.14.

Note: If multiple audio channels are used, metrics based on samples do not increment at a higher rate. "A sample" refers to having a sample in either channel - simultaneously having samples in multiple channels counts as a single sample. When calculating echo return loss, the channel of the least audio energy is considered for any sample.

echoReturnLossEnhancement of type double

Only present when the MediaStreamTrack is sourced from a microphone where echo cancellation is applied. Calculated in decibels, as defined in [ECHO] (2012) section 3.15.

Note: If multiple audio channels are used, metrics based on samples do not increment at a higher rate. "A sample" refers to having a sample in either channel - simultaneously having samples in multiple channels counts as a single sample. When calculating echo return loss enhancement, the channel of the least audio energy is considered for any sample.

Dictionary RTCVideoSourceStats Members

width of type unsigned long

The width, in pixels, of the last frame originating from this source. Before a frame has been produced this attribute is missing.

height of type unsigned long

The height, in pixels, of the last frame originating from this source. Before a frame has been produced this attribute is missing.

bitDepth of type unsigned long

The bit depth per pixel of the last frame originating from this source. Before a frame has been produced this attribute is missing.

frames of type frames

The total number of frames originating from this source.

framesPerSecond of type unsigned long

The number of frames originating from this source, measured during the last second. For the first second of this object's lifetime this attribute is missing.

Dictionary RTCRtpContributingSourceStats Members

contributorSsrc of type unsigned long

The SSRC identifier of the contributing source represented by this stats object, as defined by [RFC3550]. It is a 32-bit unsigned integer that appears in the CSRC list of any packets the relevant source contributed to.

inboundRtpStreamId of type DOMString

The ID of the RTCInboundRtpStreamStats object representing the inbound RTP stream that this contributing source is contributing to.

packetsContributedTo of type unsigned long

The total number of RTP packets that this contributing source contributed to. This value is incremented each time a packet is counted by RTCInboundRtpStreamStats.packetsReceived, and the packet's CSRC list (as defined by [RFC3550] section 5.1) contains the SSRC identifier of this contributing source, contributorSsrc.

audioLevel of type double

Present if the last received RTP packet that this source contributed to contained an [RFC6465] mixer-to-client audio level header extension. The value of audioLevel is between 0..1 (linear), where 1.0 represents 0 dBov, 0 represents silence, and 0.5 represents approximately 6 dBSPL change in the sound pressure level from 0 dBov.

The [RFC6465] header extension contains values in the range 0..127, in units of -dBov, where 127 represents silence. To convert these values to the linear 0..1 range of audioLevel, a value of 127 is converted to 0, and all other values are converted using the equation: f(rfc6465_level) = 10^(-rfc6465_level/20).

Dictionary RTCPeerConnectionStats Members

dataChannelsOpened of type unsigned long

Represents the number of unique DataChannels that have entered the "open" state during their lifetime.

dataChannelsClosed of type unsigned long

Represents the number of unique DataChannels that have left the "open" state during their lifetime (due to being closed by either end or the underlying transport being closed). DataChannels that transition from "connecting" to "closing" or "closed" without ever being "open" are not counted in this number.

dataChannelsRequested of type unsigned long

Represents the number of unique DataChannels returned from a successful createDataChannel() call on the RTCPeerConnection. If the underlying data transport is not established, these may be in the "connecting" state.

dataChannelsAccepted of type unsigned long

Represents the number of unique DataChannels signaled in a "datachannel" event on the RTCPeerConnection.

The total number of open data channels at any time can be calculated as dataChannelsOpened - dataChannelsClosed. This number is always positive.

The sum of dataChannelsRequested and dataChannelsAccepted is always greater than or equal to dataChannelsOpened - the difference is equal to the number of channels that have been requested, but have not reached the "open" state.

Dictionary RTCRtpTransceiverStats Members

senderId of type DOMString

The identifier of the stats object representing the RTCRtpSender associated with the RTCRtpTransceiver represented by this stats object.

receiverId of type DOMString

The identifier of the stats object representing the RTCRtpReceiver associated with the RTCRtpTransceiver represented by this stats object.

mid of type DOMString

If the RTCRtpTransceiver that this stats object represents has a mid value that is not null, this is that value, otherwise this value is undefined.

Dictionary RTCMediaHandlerStats Members

trackIdentifier of type DOMString

Represents the id property of the track.

remoteSource of type boolean

Only applicable for 'track' stats. True if the source is remote, for instance if it is sourced from another host via an RTCPeerConnection. False otherwise.

ended of type boolean

Reflects the "ended" state of the track.

kind of type DOMString

Either "audio" or "video". This reflects the "kind" attribute of the MediaStreamTrack, see [GETUSERMEDIA].

priority of type RTCPriorityType

Indicates the priority set for the track. It is specified in [RTCWEB-TRANSPORT], Section 4.

Dictionary RTCVideoHandlerStats Members

Dictionary RTCVideoSenderStats Members

mediaSourceId of type DOMString

The identifier of the stats object representing the track currently attached to this sender, an RTCMediaSourceStats.

Dictionary RTCSenderVideoTrackAttachmentStats Members

Dictionary RTCVideoReceiverStats Members

Dictionary RTCAudioHandlerStats Members

Dictionary RTCAudioSenderStats Members

mediaSourceId of type DOMString

The identifier of the stats object representing the track currently attached to this sender, an RTCMediaSourceStats.

Dictionary RTCSenderAudioTrackAttachmentStats Members

Dictionary RTCAudioReceiverStats Members

Dictionary RTCDataChannelStats Members

label of type DOMString

The "label" value of the RTCDataChannel object.

protocol of type DOMString

The "protocol" value of the RTCDataChannel object.

dataChannelIdentifier of type long

The "id" attribute of the RTCDataChannel object.

transportId of type DOMString

A stats object reference for the transport used to carry this datachannel.

state of type RTCDataChannelState

The "readyState" value of the RTCDataChannel object.

messagesSent of type unsigned long

Represents the total number of API "message" events sent.

bytesSent of type unsigned long long

Represents the total number of payload bytes sent on this RTCDatachannel, i.e., not including headers or padding.

messagesReceived of type unsigned long

Represents the total number of API "message" events received.

bytesReceived of type unsigned long long

Represents the total number of bytes received on this RTCDatachannel, i.e., not including headers or padding.

Dictionary RTCTransportStats Members

packetsSent of type unsigned long long

Represents the total number of packets sent over this transport.

packetsReceived of type unsigned long long

Represents the total number of packets received on this transport.

bytesSent of type unsigned long long

Represents the total number of payload bytes sent on this PeerConnection, i.e., not including headers or padding.

bytesReceived of type unsigned long long

Represents the total number of bytes received on this PeerConnection, i.e., not including headers or padding.

rtcpTransportStatsId of type DOMString

If RTP and RTCP are not multiplexed, this is the id of the transport that gives stats for the RTCP component, and this record has only the RTP component stats.

iceRole of type RTCIceRole

Set to the current value of the "role" attribute of the underlying RTCDtlsTransport's "transport".

dtlsState of type RTCDtlsTransportState

Set to the current value of the "state" attribute of the underlying RTCDtlsTransport.

selectedCandidatePairId of type DOMString

It is a unique identifier that is associated to the object that was inspected to produce the RTCIceCandidatePairStats associated with this transport.

localCertificateId of type DOMString

For components where DTLS is negotiated, give local certificate.

remoteCertificateId of type DOMString

For components where DTLS is negotiated, give remote certificate.

tlsVersion of type DOMString

For components where DTLS is negotiated, the TLS version agreed. Only present after DTLS negotiation is complete.

The value comes from ServerHello.supported_versions if present, otherwise from ServerHello.version. It is represented as four upper case hexadecimal digits, representing the two bytes of the version.

dtlsCipher of type DOMString

Descriptive name of the cipher suite used for the DTLS transport, as defined in the "Description" column of the IANA cipher suite registry [IANA-TLS-CIPHERS].

srtpCipher of type DOMString

Descriptive name of the protection profile used for the SRTP transport, as defined in the "Profile" column of the IANA DTLS-SRTP protection profile registry [IANA-DTLS-SRTP] and described further in [RFC5764].

tlsGroup of type DOMString

Descriptive name of the group used for the encryption, as defined in the "Description" column of the IANA TLS Supported Groups registry [IANA-TLS-GROUPS].

selectedCandidatePairChanges of type unsigned long

The number of times that the selected candidate pair of this transport has changed. Going from not having a selected candidate pair to having a selected candidate pair, or the other way around, also increases this counter. It is initially zero and becomes one when an initial candidate pair is selected.

Dictionary RTCSctpTransportStats Members

smoothedRoundTripTime of type double

The latest smoothed round-trip time value, corresponding to spinfo_srtt defined in [RFC6458] but converted to seconds. If there has been no round-trip time measurements yet, this value is undefined.

Dictionary RTCIceCandidateStats Members

transportId of type DOMString

It is a unique identifier that is associated to the object that was inspected to produce the RTCTransportStats associated with this candidate.

address of type DOMString

It is the address of the candidate, allowing for IPv4 addresses, IPv6 addresses, and fully qualified domain names (FQDNs). See [RFC5245] section 15.1 for details.

The user agent should make sure that only remote candidate addresses that the web application has configured on the corresponding RTCPeerConnection are exposed; This is especially important for peer reflexive remote candidates. By default, the user agent MUST leave the 'address' member as null in the RTCICECandidateStats dictionary of any remote candidate. Once a RTCPeerConnection instance learns on an address by the web application using addIceCandidate, the user agent can expose the 'address' member value in any remote RTCIceCandidateStats dictionary of the corresponding RTCPeerConnection that matches the newly learnt address.

port of type long

It is the port number of the candidate.

protocol of type DOMString

Valid values for transport is one of udp and tcp. Based on the "transport" defined in [RFC5245] section 15.1.

relayProtocol of type DOMString

It is the protocol used by the endpoint to communicate with the TURN server. This is only present for local candidates. Valid values are udp, tcp, or tls.

candidateType of type RTCIceCandidateType

This enumeration is defined in [WEBRTC].

priority of type long

Calculated as defined in [RFC5245] section 15.1.

url of type DOMString

For local candidates this is the URL of the ICE server from which the candidate was obtained. It is the same as the url surfaced in the RTCPeerConnectionIceEvent.

For remote candidates, this property is not present.

Dictionary RTCIceCandidatePairStats Members

transportId of type DOMString

It is a unique identifier that is associated to the object that was inspected to produce the RTCTransportStats associated with this candidate pair.

localCandidateId of type DOMString

It is a unique identifier that is associated to the object that was inspected to produce the RTCIceCandidateStats for the local candidate associated with this candidate pair.

remoteCandidateId of type DOMString

It is a unique identifier that is associated to the object that was inspected to produce the RTCIceCandidateStats for the remote candidate associated with this candidate pair.

state of type RTCStatsIceCandidatePairState

Represents the state of the checklist for the local and remote candidates in a pair.

nominated of type boolean

Related to updating the nominated flag described in Section 7.1.3.2.4 of [RFC5245].

packetsSent of type unsigned long long

Represents the total number of packets sent on this candidate pair.

packetsReceived of type unsigned long long

Represents the total number of packets received on this candidate pair.

bytesSent of type unsigned long long

Represents the total number of payload bytes sent on this candidate pair, i.e., not including headers or padding.

bytesReceived of type unsigned long long

Represents the total number of payload bytes received on this candidate pair, i.e., not including headers or padding.

lastPacketSentTimestamp of type DOMHighResTimeStamp

Represents the timestamp at which the last packet was sent on this particular candidate pair, excluding STUN packets.

lastPacketReceivedTimestamp of type DOMHighResTimeStamp

Represents the timestamp at which the last packet was received on this particular candidate pair, excluding STUN packets.

firstRequestTimestamp of type DOMHighResTimeStamp

Represents the timestamp at which the first STUN request was sent on this particular candidate pair.

lastRequestTimestamp of type DOMHighResTimeStamp

Represents the timestamp at which the last STUN request was sent on this particular candidate pair. The average interval between two consecutive connectivity checks sent can be calculated with (lastRequestTimestamp - firstRequestTimestamp) / requestsSent.

lastResponseTimestamp of type DOMHighResTimeStamp

Represents the timestamp at which the last STUN response was received on this particular candidate pair.

totalRoundTripTime of type double

Represents the sum of all round trip time measurements in seconds since the beginning of the session, based on STUN connectivity check [STUN-PATH-CHAR] responses (responsesReceived), including those that reply to requests that are sent in order to verify consent [RFC7675]. The average round trip time can be computed from totalRoundTripTime by dividing it by responsesReceived.

currentRoundTripTime of type double

Represents the latest round trip time measured in seconds, computed from both STUN connectivity checks [STUN-PATH-CHAR], including those that are sent for consent verification [RFC7675].

availableOutgoingBitrate of type double

It is calculated by the underlying congestion control by combining the available bitrate for all the outgoing RTP streams using this candidate pair. The bitrate measurement does not count the size of the IP or other transport layers like TCP or UDP. It is similar to the TIAS defined in [RFC3890], i.e., it is measured in bits per second and the bitrate is calculated over a 1 second window.

Implementations that do not calculate a sender-side estimate MUST leave this undefined. Additionally, the value MUST be undefined for candidate pairs that were never used. For pairs in use, the estimate is normally no lower than the bitrate for the packets sent at lastPacketSentTimestamp, but might be higher. For candidate pairs that are not currently in use but were used before, implementations MUST return undefined.

availableIncomingBitrate of type double

It is calculated by the underlying congestion control by combining the available bitrate for all the incoming RTP streams using this candidate pair. The bitrate measurement does not count the size of the IP or other transport layers like TCP or UDP. It is similar to the TIAS defined in [RFC3890], i.e., it is measured in bits per second and the bitrate is calculated over a 1 second window.

Implementations that do not calculate a receiver-side estimate MUST leave this undefined. Additionally, the value should be undefined for candidate pairs that were never used. For pairs in use, the estimate is normally no lower than the bitrate for the packets received at lastPacketReceivedTimestamp, but might be higher. For candidate pairs that are not currently in use but were used before, implementations MUST return undefined.

circuitBreakerTriggerCount of type unsigned long

Represents the number of times the circuit breaker is triggered for this particular 5-tuple. Ceasing transmission when a circuit breaker is triggered is defined in Section 4.5 of [RFC8083]. The field MUST return undefined for user-agents that do not implement the circuit-breaker algorithm.

requestsReceived of type unsigned long long

Represents the total number of connectivity check requests received (including retransmissions). It is impossible for the receiver to tell whether the request was sent in order to check connectivity or check consent, so all connectivity checks requests are counted here.

requestsSent of type unsigned long long

Represents the total number of connectivity check requests sent (not including retransmissions).

responsesReceived of type unsigned long long

Represents the total number of connectivity check responses received.

responsesSent of type unsigned long long

Represents the total number of connectivity check responses sent. Since we cannot distinguish connectivity check requests and consent requests, all responses are counted.

retransmissionsReceived of type unsigned long long

Represents the total number of connectivity check request retransmissions received. Retransmissions are defined as connectivity check requests with a TRANSACTION_TRANSMIT_COUNTER attribute where the "req" field is larger than 1, as defined in [RFC7982].

retransmissionsSent of type unsigned long long

Represents the total number of connectivity check request retransmissions sent.

consentRequestsSent of type unsigned long long

Represents the total number of consent requests sent.

consentExpiredTimestamp of type DOMHighResTimeStamp

Represents the timestamp at which the latest valid STUN binding response expired, as defined in [RFC7675] section 5.1. If a valid STUN binding response has not been made (responsesReceived is zero) or the latest one has not expired this value must be undefined.

packetsDiscardedOnSend of type unsigned long

Total number of packets for this candidate pair that have been discarded due to socket errors, i.e. a socket error occured when handing the packets to the socket. This might happen due to various reasons, including full buffer or no available memory.

bytesDiscardedOnSend of type unsigned long long

Total number of bytes for this candidate pair that have been discarded due to socket errors, i.e. a socket error occured when handing the packets containing the bytes to the socket. This might happen due to various reasons, including full buffer or no available memory. Calculated as defined in [RFC3550] section 6.4.1.

Dictionary RTCCertificateStats Members

fingerprint of type DOMString

The fingerprint of the certificate. Only use the fingerprint value as defined in Section 5 of [RFC4572].

fingerprintAlgorithm of type DOMString

The hash function used to compute the certificate fingerprint. For instance, "sha-256".

base64Certificate of type DOMString

The DER-encoded base-64 representation of the certificate.

issuerCertificateId of type DOMString

The issuerCertificateId refers to the stats object that contains the next certificate in the certificate chain. If the current certificate is at the end of the chain (i.e. a self-signed certificate), this will not be set.

Dictionary RTCIceServerStats Members

url of type DOMString

The URL of the ICE server (e.g. TURN or STUN server).

port of type long

It is the port number used by the client.

protocol of type DOMString

Valid values for transport is one of udp and tcp. Based on the "transport" defined in [RFC5245] section 15.1.

totalRequestsSent of type unsigned long

The total amount of requests that have been sent to this server.

totalResponsesReceived of type unsigned long

The total amount of responses received from this server.

totalRoundTripTime of type double

The sum of RTTs for all requests that have been sent where a response has been received.