This document defines a set of WebIDL objects that allow access to the statistical information about a RTCPeerConnection.

These objects are returned from the getStats API that is specified in [[WEBRTC]].

This document is incomplete, and as such is not yet suitable for implementation. However, early experimentation is encouraged.

Introduction

Audio, video, or data packets transmitted over a peer-connection can be lost, and experience varying amounts of network delay. A web application implementing WebRTC expects to monitor the performance of the underlying network and media pipeline.

This document defines the statistic identifiers used by the web application to extract metrics from the user agent.

This specification defines the conformance criteria that applies to a single product: the user agent.

Implementations that use ECMAScript to implement the objects defined in this specification MUST implement them in a manner consistent with the ECMAScript Bindings defined in the Web IDL specification [[WEBIDL]], as this document uses that specification and terminology.

This specification does not define what objects a conforming implementation should generate. Specifications that refer to this specification have the need to specify conformance. They should put in their document text like this:

Terminology

The concepts queue a task, and fires a simple event are defined in [[!HTML5]].

The terms event, event handlers, and event handler event types are defined in [[!HTML5]].

The terms MediaStream, MediaStreamTrack, and Consumer are defined in [[!GETUSERMEDIA]].

The terms RTCPeerConnection, RTCDataChannel, RTCDtlsTransport, RTCDtlsTransportState, RTCIceTransport, RTCIceRole and RTCPriorityType are defined in [[!WEBRTC]].

The term RTP stream is defined in [[RFC7656]] section 2.1.10.

The terms RTCStats, RTCStats.timestamp, RTCStats.type, RTCStats.id, RTCCertificate, and statsended are defined in [[!WEBRTC]].

The terms performance.timeOrigin and performance.now() are defined in [[!HIGHRES-TIME]].

Basic concepts

The basic object of the stats model is the stats object. The following terms are defined to describe it:

Monitored object

An internal object that keeps a set of data values. Most monitored objects are object defined in the WebRTC API; they may be thought of as being internal properties of those objects.

Stats object
This is a set of values, copied out from a monitored object at a specific moment in time. It is returned as a WebIDL dictionary through the getStats API call.
Stats object reference

A monitored object has a stable identifier "id", which is reflected in all stats objects produced from the monitored object. Stats objects may contain references to other stats objects using this "id" value. In a stats object, these references are represented by a DOMString containing "id" value of the referenced stats object.

All stats object references have type DOMString and attribute names ending in 'Id', or they have type sequence<DOMString> and attribute names ending in 'Ids'.

Stats value
Refers to a single value within a stats object.

A monitored object changes the values it contains continuously over its lifetime, but is never visible through the getStats API call. A stats object, once returned, never changes.

The stats API is defined in [[!WEBRTC]]. It is defined to return a collection of stats objects, each of which is a dictionary inheriting directly or indirectly from the RTCStats dictionary. This API is normatively defined in [[!WEBRTC]], but is reproduced here for ease of reference.

        dictionary RTCStats {
    DOMHighResTimeStamp timestamp;
    RTCStatsType        type;
    DOMString           id;
        };
      

Timestamps are expressed with DOMHighResTimeStamp [[!HIGHRES-TIME]], and are defined as performance.timeOrigin + performance.now() at the time the information is collected.

Guidelines for design of stats objects

When introducing a new stats object, the following principles should be followed:

The new members of the stats dictionary need to be named according to standard practice (camelCase), as per [[API-DESIGN-PRINCIPLES]].

Names ending in "Id" (such as "transportId") are always a stats object reference; names ending in "Ids" (such as "trackIds") are always of type sequence<DOMString>, where each DOMString is a stats object reference.

If the natural name for a stats value would end in "id" (such as when the stats value is an in-protocol identifier for the monitored object), the recommended practice is to let the name end in "identifier", such as "ssrcIdentifier" or "dataChannelIdentifier".

Stats are sampled by Javascript. In general, an application will not have overall control over how often stats are sampled, and the implementation cannot know what the intended use of the stats is. There is, by design, no control surface for the application to influence how stats are generated.

Therefore, letting the implementation compute "average" rates is not a good idea, since that implies some averaging time interval that can't be set beforehand. Instead, the recommended approach is to count the number of measurements of a value and sum the measurements given even if the sum is meaningless in itself; the JS application can then compute averages over any desired time interval by calling getStats() twice, taking the difference of the two sums and dividing by the difference of the two counts.

For stats that are measured against time, such as byte counts, no separate counter is needed; one can instead divide by the difference in the timestamps.

Guidelines for implementing stats objects

When implementing stats objects, the following guidelines should be adhered to:

Lifetime considerations for monitored objects

The object descriptions will say what the lifetime of a monitored object from the perspective of stats is. When a monitored object is "deleted", it no longer appears in stats; until this happens, it will appear. This may or may not correspond to the actual lifetime of an object in an implementation; what matters for this specification is what appears in stats.

If a monitored object can only exist in a few instances over the lifetime of a RTCPeerConnection, it may be simplest to consider it "eternal" and never delete it from the set of objects reported on in stats. This type of object will remain visible until the RTCPeerConnection is no longer available; it is also visible in getStats() after pc.close(). This is the default when no lifetime is mentioned in its specification.

Objects that might exist in many instances over time should have a defined time at which they are deleted, at which time a statsended event is fired on their behalf. Each event that causes deletions to happen MUST fire only one statsended event, but there are cases where one action causes multiple deletion events; for instance, an ICE restart will fire only one event containing the stats for all the discarded candidates and pairs, but will also cause a later event to be fired when the currently-in-use candidate pair and its candidates are discarded.

When a monitored object is deleted, a final stats object is produced, carrying the values current at the time of deletion. This object will be made available using the statsended event on the associated RTCPeerConnection. This is important in order to report consistently on short-lived objects and to be able to consistently report totals over the lifetime of a RTCPeerConnection.

When an object is deleted, we can guarantee that no subsequent getStats() call will contain a stats object reference that references the deleted object We also guarantee that the stats id of the deleted object will never be reused for another object. This ensures that an application that collects stats objects for deleted monitored objects will always be able to uniquely identify the object pointed to in the result of any getStats() call.

Guidelines for getStats() results caching/throttling

A call to getStats() touches many components of WebRTC and may take significant time to execute. The implementation may or may not utilize caching or throttling of getStats() calls for performance benefits, however any implementation must adhere to the following:

When the state of the RTCPeerConnection visibly changes as a result of an API call, a promise resolving or an event firing, subsequent new getStats() calls must return up-to-date dictionaries for the affected objects. For example, if a track is added with addTrack() subsequent getStats() calls must resolve with a corresponding RTCMediaHandlerStats object. If you call setRemoteDescription() removing a remote track, upon the promise resolving or an associated event (stream's onremovetrack or track's onmute) firing, calling getStats() must resolve with an up-to-date RTCMediaHandlerStats object.

When the statsended event is fired, subsequent getStats() calls MUST NOT return stats for the monitored object that was reported on in the statsended event.

Maintenance procedures for stats object types

Adding new stats objects

This document, in its editors' draft form, serves as the repository for the currently defined set of stats object types including proposals for new standard types.

This document specifies the interoperable stats object types. Proposals for new object types may be made in the editors draft maintained on GitHub. New standard types may appear in future revisions of the W3C Recommendation.

If a need for a new stats object type or stats value within a stats object is found, an issue should be raised on Github, and a review process will decide on whether the stat should be added to the editors draft or not.

A pull request for a change to the editors draft may serve as guidance for the discussion, but the eventual merge is dependent on the review process.

While the WebRTC WG exist, it will serve as the review body; once it has disbanded, the W3C will have to establish appropriate review.

The level of review sought is that of the IETF process' "expert review", as defined in [[RFC5226]] section 4.1. The documentation needed includes the names of the new stats, their data types, and the definitions they are based on, specified to a level that allows interoperable implementation. The specification may consist of references to other documents.

Another specification that wishes to refer to a specific version (for instance for conformance) should refer to a dated version; these will be produced regularly when updates happen.

Retiring stats objects

At times, it makes sense to retire the definition for a stats object or a stats value. When this happens, it is not advisable to simply delete it from the spec, since there may be implementations out there that use it, and it is important that the name is reserved from re-use for another, incompatible definition.

Therefore, retired stats objects are moved to a separate section in this document. Retired stats objects are moved there in their entirety; retired stats values are moved to a "partial dictionary".

If there is no evidence that the retired object definition has ever been used (such as an object that is added to the spec and renamed, redefined or removed prior to implementation), the editors can decide to just remove the object from the spec.

RTCStatsType

The type element, of type RTCStatsType, indicates the type of the object that the RTCStats object represents. An object with a given "type" can have only one IDL dictionary type, but multiple "type" values may indicate the same IDL dictionary type; for example, "local-candidate" and "remote-candidate" both use the IDL dictionary type RTCIceCandidateStats.

This specification is normative for the allowed values of RTCStatsType.

RTCStatsType enum

enum RTCStatsType {
"codec",
"inbound-rtp",
"outbound-rtp",
"remote-inbound-rtp",
"remote-outbound-rtp",
"csrc",
"peer-connection",
"data-channel",
"stream",
"track",
"sender",
"receiver",
"transport",
"candidate-pair",
"local-candidate",
"remote-candidate",
"certificate"
};
        

The following strings are valid values for RTCStatsType:

codec

Statistics for a codec that is currently being used by RTP streams being sent or received by this RTCPeerConnection object. It is accessed by the RTCCodecStats.

inbound-rtp

Statistics for an inbound RTP stream that is currently received with this RTCPeerConnection object. It is accessed by the RTCInboundRtpStreamStats.

outbound-rtp

Statistics for an outbound RTP stream that is currently sent with this RTCPeerConnection object. It is accessed by the RTCOutboundRtpStreamStats.

remote-inbound-rtp

Statistics for the remote endpoint's inbound RTP stream corresponding to an outbound stream that is currently sent with this RTCPeerConnection object. It is measured at the remote endpoint and reported in an RTCP Receiver Report (RR) or RTCP Extended Report (XR). It is accessed by the RTCRemoteInboundRtpStreamStats.

remote-outbound-rtp

Statistics for the remote endpoint's outbound RTP stream corresponding to an inbound stream that is currently received with this RTCPeerConnection object. It is measured at the remote endpoint and reported in an RTCP Sender Report (SR). It is accessed by the RTCRemoteOutboundRtpStreamStats.

csrc

Statistics for a contributing source (CSRC) that contributed to an inbound RTP stream. It is accessed by the RTCRtpContributingSourceStats.

peer-connection

Statistics related to the RTCPeerConnection object. It is accessed by the RTCPeerConnectionStats.

data-channel

Statistics related to each RTCDataChannel id. It is accessed by the RTCDataChannelStats.

stream

Contains statistics related to a specific MediaStream. It is accessed by the RTCMediaStreamStats.

track

Contains statistics related to a specific MediaStreamTrack's attachment to an RTCRtpSender and the corresponding media-level metrics. It is accessed by either RTCSenderVideoTrackAttachmentStats or RTCSenderAudioTrackAttachmentStats, both inherited from RTCMediaHandlerStats.

The monitored "track" object is deleted when the sender it reports on has its "track" value changed to no longer refer to the same track.

sender

Contains statistics related to a specific RTCRtpSender and the corresponding media-level metrics. It is accessed by the RTCAudioSenderStats or the RTCVideoSenderStats depending on kind.

receiver

Contains statistics related to a specific receiver and the corresponding media-level metrics. It is accessed by the RTCAudioReceiverStats or the RTCVideoReceiverStats depending on kind.

transport

Transport statistics related to the RTCPeerConnection object. It is accessed by the RTCTransportStats.

candidate-pair

ICE candidate pair statistics related to the RTCIceTransport objects. It is accessed by the RTCIceCandidatePairStats.

A candidate pair that is not the current pair for a transport is deleted when the RTCIceTransport does an ICE restart, at the time the state changes to "new". The candidate pair that is the current pair for a transport is deleted after an ICE restart when the RTCIceTransport switches to using a candidate pair generated from the new candidates; this time doesn't correspond to any other externally observable event.

local-candidate

ICE local candidate statistics related to the RTCIceTransport objects. It is accessed by the RTCIceCandidateStats for the local candidate.

A local candidate is deleted when the RTCIceTransport does an ICE restart, and the candidate is no longer a member of any non-deleted candidate pair.

remote-candidate

ICE remote candidate statistics related to the RTCIceTransport objects. It is accessed by the RTCIceCandidateStats for the remote candidate.

A remote candidate is deleted when the RTCIceTransport does an ICE restart, and the candidate is no longer a member of any non-deleted candidate pair.

certificate

Information about a certificate used by an RTCIceTransport. It is accessed by the RTCCertificateStats.

Stats dictionaries

The RTP statistics hierarchy

The dictionaries for RTP statistics are structured as a hierarchy, so that those stats that make sense in many different contexts are represented just once in IDL.

The lifetime of all RTP monitored objects starts when the RTP stream is first used: When the first RTP packet is sent or received on the SSRC it represents, or when the first RTCP packet is sent or received that refers to the SSRC of the RTP stream.

RTP monitored objects are not deleted.

The hierarchy is as follows:

RTCRtpStreamStats: Stats that apply to any end of any RTP stream

RTCRtpStreamStats dictionary

dictionary RTCRtpStreamStats : RTCStats {
             unsigned long       ssrc;
             DOMString           kind;
             DOMString           transportId;
             DOMString           codecId;
             unsigned long       firCount;
             unsigned long       pliCount;
             unsigned long       nackCount;
             unsigned long       sliCount;
             unsigned long long  qpSum;
};

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 codec 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.

firCount of type unsigned long

Count the total number of Full Intra Request (FIR) packets received by the sender. This metric is only valid for video and is sent by 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

Count the total number of Picture Loss Indication (PLI) packets received by the sender. This metric is only valid for video and is sent by receiver. Calculated as defined in [[!RFC4585]] section 6.3.1.

nackCount of type unsigned long

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

sliCount of type unsigned long

Count the total number of Slice Loss Indication (SLI) packets received by the sender. This metric is only valid for video and is sent by receiver. Calculated as defined in [[!RFC4585]] section 6.3.2.

qpSum of type unsigned long long

The sum of the QP values of frames passed. The count of frames is in framesDecoded for inbound stream stats, and in framesEncoded for outbound stream stats.

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.

Only valid for video.

RTCCodecStats dictionary

dictionary RTCCodecStats : RTCStats {
             unsigned long payloadType;
             RTCCodecType  codecType;
             DOMString     transportId;
             DOMString     mimeType;
             unsigned long clockRate;
             unsigned long channels;
             DOMString     sdpFmtpLine;
             DOMString     implementation;
};

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.

implementation of type DOMString

Identifies the 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.

RTCCodecType enum

enum RTCCodecType {
    "encode",
    "decode",
};
Enumeration description
encode

The attached RTCCodecStats represents a media format that is being encoded, or that the implementation is prepared to encode.

decode

The attached RTCCodecStats represents a media format that the implementation is prepared to decode.

RTCReceivedRtpStreamStats dictionary

dictionary RTCReceivedRtpStreamStats : RTCRtpStreamStats {
             unsigned long      packetsReceived;
             long               packetsLost;
             double             jitter;
             unsigned long      packetsDiscarded;
             unsigned long      packetsRepaired;
             unsigned long      burstPacketsLost;
             unsigned long      burstPacketsDiscarded;
             unsigned long      burstLossCount;
             unsigned long      burstDiscardCount;
             double             burstLossRate;
             double             burstDiscardRate;
             double             gapLossRate;
             double             gapDiscardRate;
};

Dictionary RTCReceivedRtpStreamStats Members

packetsReceived of type unsigned 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

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

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

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

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

burstPacketsDiscarded of type unsigned 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.

RTCInboundRtpStreamStats dictionary

The RTCInboundRtpStreamStats dictionary represents the measurement metrics for the incoming RTP media stream. The timestamp reported in the statistics object is the time at which the data was sampled.

dictionary RTCInboundRtpStreamStats : RTCReceivedRtpStreamStats {
             DOMString            trackId;
             DOMString            receiverId;
             DOMString            remoteId;
             unsigned long        framesDecoded;
             DOMHighResTimeStamp  lastPacketReceivedTimestamp;
             double               averageRtcpInterval;
             unsigned long        fecPacketsReceived;
             unsigned long long   bytesReceived;
             unsigned long        packetsFailedDecryption;
             unsigned long        packetsDuplicated;
             record<USVString, unsigned long> perDscpPacketsReceived;
            };

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 SSRC, i.e., frames that would be displayed if no frames are dropped.

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 packet and an SDES packet with the CNAME item.

fecPacketsReceived of type unsigned 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).

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

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
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>

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.

RTCRemoteInboundRtpStreamStats dictionary

The RTCRemoteInboundRtpStreamStats dictionary represents the remote endpoint's measurement metrics for a particular incoming RTP stream (corresponding to an outgoing RTP stream at the sending endpoint). The timestamp reported in the statistics object is the time at which the corresponding RTCP RR was received.

dictionary RTCRemoteInboundRtpStreamStats : RTCReceivedRtpStreamStats {
             DOMString          localId;
             double             roundTripTime;
             double             fractionLost;
};

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.

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.

RTCSentRtpStreamStats dictionary

dictionary RTCSentRtpStreamStats : RTCRtpStreamStats {
             unsigned long      packetsSent;
             unsigned long      packetsDiscardedOnSend;
             unsigned long      fecPacketsSent;
             unsigned long long bytesSent;
             unsigned long long bytesDiscardedOnSend;
};

Dictionary RTCSentRtpStreamStats Members

packetsSent of type unsigned long

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

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.

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).

bytesSent of type unsigned long long

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

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.

RTCOutboundRtpStreamStats dictionary

The RTCOutboundRtpStreamStats dictionary represents the measurement metrics for the outgoing RTP stream. The timestamp reported in the statistics object is the time at which the data was sampled.

dictionary RTCOutboundRtpStreamStats : RTCSentRtpStreamStats {
             DOMString            trackId;
             DOMString            senderId;
             DOMString            remoteId;
             DOMHighResTimeStamp  lastPacketSentTimestamp;
             double               targetBitrate;
             unsigned long        framesEncoded;
             double               totalEncodeTime;
             double               averageRtcpInterval;
             RTCQualityLimitationReason                 qualityLimitationReason;
             record<DOMString, double> qualityLimitationDurations;
             record<USVString, unsigned long> perDscpPacketsSent;
};

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.
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.

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.

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.

framesEncoded of type long

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

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.

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 packet 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.

perDscpPacketsSent of type record<USVString, unsigned long>

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

RTCQualityLimitationReason enum

enum RTCQualityLimitationReason {
            "none",
            "cpu",
            "bandwidth",
            "other",
          };
Enumeration description
none

The resolution and/or framerate is not limited.

cpu

The resolution and/or framerate is primarily limited due to CPU load.

bandwidth

The resolution and/or framerate is primarily limited due to congestion cues during bandwidth estimation. Typical, congestion control algorithms use inter-arrival time, round-trip time, packet or other congestion cues to perform bandwidth estimation.

other

The resolution and/or framerate is primarily limited for a reason other than the above.

RTCRemoteOutboundRtpStreamStats dictionary

The RTCRemoteOutboundRtpStreamStats dictionary represents the remote endpoint's measurement metrics for its outgoing RTP stream (corresponding to an outgoing RTP stream at the sending endpoint). The timestamp reported in the statistics object is the time at which the corresponding RTCP SR was received.

dictionary RTCRemoteOutboundRtpStreamStats : RTCSentRtpStreamStats {
             DOMString           localId;
             DOMHighResTimeStamp remoteTimestamp;
};

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) packet, which reflects the remote endpoint's clock. That clock may not be synchronized with the local clock.

RTCRtpContributingSourceStats dictionary

The RTCRtpContributingSourceStats dictionary represents the measurement metrics for a contributing source (CSRC) that is contributing to an incoming RTP stream. Each contributing source produces a stream of RTP packets, which are combined by a mixer into a single stream of RTP packets that is ultimately received by the WebRTC endpoint. Information about the sources that contributed to this combined stream may be provided in the CSRC list or [[RFC6465]] header extension of received RTP packets. The timestamp of this stats object is the most recent time an RTP packet the source contributed to was received and counted by packetsContributedTo.

dictionary RTCRtpContributingSourceStats : RTCStats {
             unsigned long contributorSsrc;
             DOMString     inboundRtpStreamId;
             unsigned long packetsContributedTo;
             double        audioLevel;
};

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).

RTCPeerConnectionStats dictionary

dictionary RTCPeerConnectionStats : RTCStats {
            unsigned long dataChannelsOpened;
            unsigned long dataChannelsClosed;
            unsigned long dataChannelsRequested;
            unsigned long dataChannelsAccepted;
};

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.

RTCMediaStreamStats dictionary

dictionary RTCMediaStreamStats : RTCStats {
             DOMString           streamIdentifier;
             sequence<DOMString> trackIds;
};

Dictionary RTCMediaStreamStats Members

streamIdentifier of type DOMString

stream.id property

trackIds of type sequence<DOMString>

This is the id of the stats object, not the track.id.

RTCMediaHandlerStats dictionary

dictionary RTCMediaHandlerStats : RTCStats {
             DOMString           trackIdentifier;
             boolean             remoteSource;
             boolean             ended;
             DOMString           kind;
             RTCPriorityType     priority;
};

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.

RTCVideoHandlerStats dictionary

dictionary RTCVideoHandlerStats : RTCMediaHandlerStats {
             unsigned long       frameWidth;
             unsigned long       frameHeight;
             double              framesPerSecond;
};

Dictionary RTCVideoHandlerStats Members

frameWidth of type unsigned long

Represents the width of the last processed frame for this track. Before the first frame is processed this attribute is missing.

frameHeight of type unsigned long

Represents the height of the last processed frame for this track. Before the first frame is processed this attribute is missing.

framesPerSecond of type double

Represents the nominal FPS value before the degradation preference is applied. It is the number of complete frames in the last second. For sending tracks it is the current captured FPS and for the receiving tracks it is the current decoding framerate.

RTCVideoSenderStats dictionary

An RTCVideoSenderStats object represents the stats about one video sender of a RTCPeerConnection object for which one calls getStats.

It appears in the stats as soon as the sender is added by either addTrack or addTransceiver, or by media negotiation.

dictionary RTCVideoSenderStats : RTCVideoHandlerStats {
             unsigned long       framesCaptured;
             unsigned long       framesSent;
             unsigned long       hugeFramesSent;
             unsigned long       keyFramesSent;
};

Dictionary RTCVideoSenderStats Members

framesCaptured of type unsigned long

Represents the total number of frames captured, before encoding, for this RTCRtpSender (or for this MediaStreamTrack, if type is "track"). For example, if type is "sender" and this sender's track represents a camera, then this is the number of frames produced by the camera for this track while being sent by this sender, combined with the number of frames produced by all tracks previously attached to this sender while being sent by this sender. Framerates can vary due to hardware limitations or environmental factors such as lighting conditions.

framesSent of type unsigned long

Represents the total number of frames sent by this RTCRtpSender (or for this MediaStreamTrack, if type is "track").

hugeFramesSent of type unsigned long

Represents the total number of huge frames sent by this RTCRtpSender (or for this MediaStreamTrack, if type is "track"). 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. If a huge frame is also a key frame, then both counters hugeFramesSent and keyFramesSent are incremented.

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.

keyFramesSent of type unsigned long

Represents the total number of key frames sent by this RTCRtpSender (or for this MediaStreamTrack, if type is "track"), such as Infra-frames in VP8 [[RFC6386]] or I-frames in H.264 [[RFC6184]]. This is a subset of framesSent. framesSent - keyFramesSent gives you the number of delta frames sent.

RTCSenderVideoTrackAttachmentStats dictionary

An RTCSenderVideoTrackAttachmentStats object represents the stats about one attachment of a video MediaStreamTrack to the RTCPeerConnection object for which one calls getStats.

It appears in the stats as soon as it is attached (via addTrack, via addTransceiver, via replaceTrack on an RTCRtpSender object).

If a video track is attached twice (via addTransceiver or replaceTrack), there will be two RTCSenderVideoTrackAttachmentStats objects, one for each attachment. They will have the same "trackIdentifier" attribute, but different "id" attributes.

If the track is detached from the RTCPeerConnection (via removeTrack or via replaceTrack), it continues to appear, but with the "objectDeleted" member set to true.

dictionary RTCSenderVideoTrackAttachmentStats : RTCVideoSenderStats {
};

Dictionary RTCSenderVideoTrackAttachmentStats Members

RTCVideoReceiverStats dictionary

An RTCVideoReceiverStats object represents the stats about one video receiver of a RTCPeerConnection object for which one calls getStats.

It appears in the stats as soon as the RTCRtpReceiver is added by either addTrack or addTransceiver, or by media negotiation.

dictionary RTCVideoReceiverStats : RTCVideoHandlerStats {
             DOMHighResTimeStamp estimatedPlayoutTimestamp;
             double              jitterBufferDelay;
             unsigned long long  jitterBufferEmittedCount;
             unsigned long       framesReceived;
             unsigned long       keyFramesReceived;
             unsigned long       framesDecoded;
             unsigned long       framesDropped;
             unsigned long       partialFramesLost;
             unsigned long       fullFramesLost;
};

Dictionary RTCVideoReceiverStats Members

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 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 video currently playing.

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

jitterBufferDelay of type double

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

jitterBufferEmittedCount of type unsigned long long

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

framesReceived of type unsigned long

Represents the total number of complete frames received for this receiver. This metric is incremented when the complete frame is received.

keyFramesReceived of type unsigned long

Represents the total number of complete key frames received for this MediaStreamTrack, such as Infra-frames in VP8 [[RFC6386]] or I-frames in H.264 [[RFC6184]]. This is a subset of framesReceived. framesReceived - keyFramesReceived gives you the number of delta frames received. This metric is incremented when the complete key frame is received. It is not incremented if a partial key frames is received and sent for decoding, i.e., the frame could not be recovered via retransmission or FEC.

framesDecoded of type unsigned long

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

framesDropped of type unsigned long

The total number of frames dropped predecode or dropped because the frame missed its display deadline for this receiver's track. As defined in Appendix A (g) of [[!RFC7004]].

partialFramesLost of type unsigned long

The cumulative number of partial frames lost, 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

The cumulative number of full frames lost, as defined in Appendix A (i) of [[!RFC7004]].

RTCAudioHandlerStats dictionary

dictionary RTCAudioHandlerStats : RTCMediaHandlerStats {
             double              audioLevel;
             double              totalAudioEnergy;
             boolean             voiceActivityFlag;
             double              totalSamplesDuration;
};

Dictionary RTCAudioHandlerStats Members

audioLevel of type double

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 "audio level" value defined in [[RFC6464]] (as 0..127, where 0 represents 0 dBov, 126 represents -126 dBov and 127 represents silence) is obtained by the calculation given in appendix A of [[!RFC6465]]: informally, level = -round(log10(audioLevel) * 20), with audioLevel 0.0 and values above 127 mapped to 127.

The audioLevel represents the output audio level of the track; thus, if the track is sourced from an RTCReceiver, does no audio processing, has a constant level, and has a volume setting of 1.0, the audio level is expected to be the same as the audio level of the source SSRC, while if the volume setting is 0.5, the audioLevel is expected to be half that value.

For outgoing audio tracks, the audioLevel is the level of the audio being sent.

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

totalAudioEnergy of type double

This value MUST be computed as follows: for each audio sample sent/received for this object (and counted by totalSamplesSent or 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 received 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.

voiceActivityFlag of type boolean

Whether the last RTP packet sent or played out by this track contained voice activity or not based on the presence of the V bit in the extension header, as defined in [[RFC6464]].

This value indicates the voice activity in the latest RTP packet played out from a given SSRC, and is defined in the RTCRtpSynchronizationSource.voiceActivityFlag of [[WEBRTC].

totalSamplesDuration of type double

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

RTCAudioSenderStats dictionary

An RTCAudioSenderStats object represents the stats about one audio sender of a RTCPeerConnection object for which one calls getStats.

It appears in the stats as soon as the RTCRtpSender is added by either addTrack or addTransceiver, or by media negotiation.

dictionary RTCAudioSenderStats : RTCAudioHandlerStats {
             double              echoReturnLoss;
             double              echoReturnLossEnhancement;
             unsigned long long  totalSamplesSent;
};

Dictionary RTCAudioSenderStats Members

echoReturnLoss of type double

Only present while the sender is sending a track sourced from a microphone where echo cancellation is applied. Calculated in decibels, as defined in [[!ECHO]] (2012) section 3.14.

echoReturnLossEnhancement of type double

Only present while the sender is sending a track sourced from a microphone where echo cancellation is applied. Calculated in decibels, as defined in [[!ECHO]] (2012) section 3.15.

totalSamplesSent of type unsigned long long

The total number of samples that have been sent by this sender.

RTCSenderAudioTrackAttachmentStats dictionary

An RTCSenderAudioTrackAttachmentStats object represents the stats about one attachment of an audio MediaStreamTrack to the RTCPeerConnection object for which one calls getStats.

It appears in the stats as soon as it is attached (via addTrack, via addTransceiver, via replaceTrack on an RTCRtpSender object).

If an audio track is attached twice (via addTransceiver or replaceTrack), there will be two RTCSenderAudioTrackAttachmentStats objects, one for each attachment. They will have the same "trackIdentifier" attribute, but different "id" attributes.

If the track is detached from the RTCPeerConnection (via removeTrack or via replaceTrack), it continues to appear, but with the "objectDeleted" member set to true.

dictionary RTCSenderAudioTrackAttachmentStats : RTCAudioSenderStats {
};

Dictionary RTCSenderAudioTrackAttachmentStats Members

RTCAudioReceiverStats dictionary

An RTCAudioReceiverStats object represents the stats about one audio receiver of a RTCPeerConnection object for which one calls getStats.

It appears in the stats as soon as the RTCRtpReceiver is added by either addTrack or addTransceiver, or by media negotiation.

dictionary RTCAudioReceiverStats : RTCAudioHandlerStats {
             DOMHighResTimeStamp estimatedPlayoutTimestamp;
             double              jitterBufferDelay;
             unsigned long long  jitterBufferEmittedCount;
             unsigned long long  totalSamplesReceived;
             unsigned long long  concealedSamples;
             unsigned long long  concealmentEvents;
};

Dictionary RTCAudioReceiverStats Members

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 sample 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 sample takes from the time it is received and to the time it exits the jitter buffer. This increases upon samples exiting, having completed their time in the buffer (incrementing jitterBufferEmittedCount). The average jitter buffer delay can be calculated by dividing the jitterBufferDelay with the jitterBufferEmittedCount.

jitterBufferEmittedCount of type unsigned long long

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

totalSamplesReceived of type unsigned long long

The total number of samples that have been received by this receiver. This includes concealedSamples.

concealedSamples of type unsigned long long

The total number of samples that are concealed samples. A concealed sample is a sample that is based on data that was synthesized to conceal packet loss and does not represent incoming data.

concealmentEvents of type unsigned long long

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.

RTCDataChannelStats dictionary

dictionary RTCDataChannelStats : RTCStats {
             DOMString           label;
             DOMString           protocol;
             long                dataChannelIdentifier;
             DOMString           transportId;
             RTCDataChannelState state;
             unsigned long       messagesSent;
             unsigned long long  bytesSent;
             unsigned long       messagesReceived;
             unsigned long long  bytesReceived;
};

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.

RTCTransportStats dictionary

An RTCTransportStats object represents the stats corresponding to an RTCDtlsTransport and its underlying RTCIceTransport. When RTCP multiplexing is used, one transport is used for both RTP and RTCP. Otherwise, RTP and RTCP will be sent on separate transports, and rtcpTransportStatsId can be used to pair the resulting RTCTransportStats objects. Additionally, when bundling is used, a single transport will be used for all MediaStreamTracks in the bundle group. If bundling is not used, different MediaStreamTrack will use different transports. RTCP multiplexing and bundling are described in [[!WEBRTC]].

dictionary RTCTransportStats : RTCStats {
             unsigned long         packetsSent;
             unsigned long         packetsReceived;
             unsigned long long    bytesSent;
             unsigned long long    bytesReceived;
             DOMString             rtcpTransportStatsId;
             RTCIceRole            iceRole;
             RTCDtlsTransportState dtlsState;
             DOMString             selectedCandidatePairId;
             DOMString             localCertificateId;
             DOMString             remoteCertificateId;
             DOMString             tlsVersion;
             DOMString             dtlsCipher;
             DOMString             srtpCipher;
             DOMString             tlsGroup;
};

Dictionary RTCTransportStats Members

packetsSent of type unsigned long

Represents the total number of packets sent over this transport.

packetsReceived of type unsigned 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 hex 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]].

RTCIceCandidateStats dictionary

RTCIceCandidateStats reflects the properties of a candidate in Section 15.1 of [[!RFC5245]]. It corresponds to a RTCIceCandidate object.

dictionary RTCIceCandidateStats : RTCStats {
             DOMString                transportId;
             RTCNetworkType           networkType;
             DOMString?               address;
             long                     port;
             DOMString                protocol;
             RTCIceCandidateType      candidateType;
             long                     priority;
             DOMString                url;
             DOMString                relayProtocol;
             boolean                  deleted = false;
};

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.

networkType of type RTCNetworkType

Represents the type of network interface used by the base of a local candidate (the address the ICE agent sends from). Only present for local candidates; it's not possible to know what type of network interface a remote candidate is using.

This stat only tells you about the network interface used by the first "hop"; it's possible that a connection will be bottlenecked by another type of network. For example, when using Wi-Fi tethering, the networkType of the relevant candidate would be "wifi", even when the next hop is over a cellular connection.

This reveals information that would otherwise not be available to web pages, which increases the fingerprint surface.

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.

deleted of type boolean, defaulting to false

For local candidates, true indicates that the candidate has been deleted/freed as described by [[!RFC5245]]. For host candidates, this means that any network resources (typically a socket) associated with the candidate have been released. For TURN candidates, this means the TURN allocation is no longer active.

For remote candidates, this property is not present.

RTCNetworkType enum

enum RTCNetworkType {
    "bluetooth",
    "cellular",
    "ethernet",
    "wifi",
    "wimax",
    "vpn",
    "unknown"
};
Enumeration description
bluetooth

A Bluetooth connection.

cellular

A cellular connection (e.g., EDGE, HSPA, LTE, etc.).

ethernet

An Ethernet connection.

wifi

A Wi-Fi connection.

wimax

A WiMAX connection.

vpn

The connection runs over a VPN. The underlying network type is not available.

unknown

The user agent is unable or unwilling to identify the underlying connection technology.

RTCIceCandidatePairStats dictionary

dictionary RTCIceCandidatePairStats : RTCStats {
             DOMString                     transportId;
             DOMString                     localCandidateId;
             DOMString                     remoteCandidateId;
             RTCStatsIceCandidatePairState state;
             boolean                       nominated;
             unsigned long                 packetsSent;
             unsigned long                 packetsReceived;
             unsigned long long            bytesSent;
             unsigned long long            bytesReceived;
             DOMHighResTimeStamp           lastPacketSentTimestamp;
             DOMHighResTimeStamp           lastPacketReceivedTimestamp;
             DOMHighResTimeStamp           firstRequestTimestamp;
             DOMHighResTimeStamp           lastRequestTimestamp;
             DOMHighResTimeStamp           lastResponseTimestamp;
             double                        totalRoundTripTime;
             double                        currentRoundTripTime;
             double                        availableOutgoingBitrate;
             double                        availableIncomingBitrate;
             unsigned long                 circuitBreakerTriggerCount;
             unsigned long long            requestsReceived;
             unsigned long long            requestsSent;
             unsigned long long            responsesReceived;
             unsigned long long            responsesSent;
             unsigned long long            retransmissionsReceived;
             unsigned long long            retransmissionsSent;
             unsigned long long            consentRequestsSent;
             DOMHighResTimeStamp           consentExpiredTimestamp;
};

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

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

packetsReceived of type unsigned 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.

RTCStatsIceCandidatePairState enum

enum RTCStatsIceCandidatePairState {
    "frozen",
    "waiting",
    "in-progress",
    "failed",
    "succeeded"
};
Enumeration description
frozen

Defined in Section 5.7.4 of [[!RFC5245]].

waiting

Defined in Section 5.7.4 of [[!RFC5245]].

in-progress

Defined in Section 5.7.4 of [[!RFC5245]].

failed

Defined in Section 5.7.4 of [[!RFC5245]].

succeeded

Defined in Section 5.7.4 of [[!RFC5245]].

RTCCertificateStats dictionary

dictionary RTCCertificateStats : RTCStats {
             DOMString fingerprint;
             DOMString fingerprintAlgorithm;
             DOMString base64Certificate;
             DOMString issuerCertificateId;
};

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.

Obsolete stats

partial dictionary RTCIceCandidateStats {
           boolean                  isRemote;
        };
        

Obsolete RTCIceCandidateStats members

isRemote of type boolean

false indicates that this represents a local candidate; true indicates that this represents a remote candidate.

partial dictionary RTCIceCandidatePairStats {
          double totalRtt;
          double currentRtt;
          unsigned long long priority;
          };
          

Obsolete RTCIceCandidatePairStats members

totalRtt

This field got renamed to "totalRoundTripTime" in Dec 2016.

currentRtt

This field got renamed to "currentRoundTripTime" in Dec 2016.

priority

This field got removed in Feb 2018, as it cannot be represented in 53 bits. It can be recalculated if needed as defined in [[RFC5245]] section 5.7.2.

partial dictionary RTCRTPStreamStats {
             DOMString           mediaType;
             double              averageRTCPInterval;
};

Obsolete RTCRtpStreamStats members

mediaType of type DOMString

This field got renamed to "kind" in Feb 2018.

averageRTCPInterval

This field got renamed to "averageRtcpInterval" in Jan 2018.

Examples

Example of a stats application

Consider the case where the user is experiencing bad sound and the application wants to determine if the cause of it is packet loss. The following example code might be used:

var baselineReport, currentReport;
var sender = pc.getSenders()[0];

sender.getStats().then(function (report) {
    baselineReport = report;
})
.then(function() {
    return new Promise(function(resolve) {
        setTimeout(resolve, aBit); // ... wait a bit
    });
})
.then(function() {
    return sender.getStats();
})
.then(function (report) {
    currentReport = report;
    processStats();
})
.catch(function (error) {
  console.log(error.toString());
});

function processStats() {
    // compare the elements from the current report with the baseline
    for (let now of currentReport.values()) {
        if (now.type != "outbound-rtp")
            continue;

        // get the corresponding stats from the baseline report
        let base = baselineReport.get(now.id);

        if (base) {
            remoteNow = currentReport[now.remoteId];
            remoteBase = baselineReport[base.remoteId];

            var packetsSent = now.packetsSent - base.packetsSent;
            var packetsReceived = remoteNow.packetsReceived - remoteBase.packetsReceived;

            // if intervalFractionLoss is > 0.3, we've probably found the culprit
            var intervalFractionLoss = (packetsSent - packetsReceived) / packetsSent;
        }
    });
}

Security and Privacy Considerations

The data exposed by WebRTC Statistics include most of the media and network data also exposed by [[!GETUSERMEDIA]] and [[!WEBRTC]] - as such, all the privacy and security considerations of these specifications related to data exposure apply as well to this specifciation.

In addition, the properties exposed by RTCReceivedRtpStreamStats, RTCRemoteInboundRtpStreamStats, RTCSentRtpStreamStats, RTCOutboundRtpStreamStats, RTCRemoteOutboundRtpStreamStats, RTCIceCandidatePairStats, RTCTransportStats expose network-layer data not currently available to the JavaScript layer.

Beyond the risks associated with revealing IP addresses as discussed in the WebRTC 1.0 specification, some combination of the network properties uniquely exposed by this specification can be correlated with location.

For instance, the round-trip time exposed in RTCRemoteInboundRtpStreamStats can give some coarse indication on how far aparts the peers are located, and thus, if one of the peer's location is known, this may reveal information about the other peer.

When applied to isolated streams, media metrics may allow an application to infer some characteristics of the isolated stream, such as if anyone is speaking (by watching the audioLevel statistic).

The following stats are deemed to be sensitive, and MUST NOT be reported for an isolated media stream:

Change Log

This section will be removed before publication. The entries are in reverse chronological order.

Changes between 31 Mar 2017 and 14 Jun 2017

Changes between 14 Dec 2016 and 30 Mar 2017

Changes since 21 sep 2016

This list does not include infrastructure and minor editorials.

Changes since 26 May 2016

Changes since 23 October 2015

Changes since 03 February 2015

  1. [#10] Added RTCRTPStreamStats.mediaType.

Changes since 30 September 2014

  1. kept getStats() in webrtc-pc. Changed RTCStatsType from enum to DOMString.
  2. Added "datachannel" to RTCStatsType.
  3. Added fractionLost to RTCInboundRTPStreamStats.
  4. Clarified that bytesSent and bytesReceived do no include headers or paddings.

Acknowledgements

The editors wish to thank the Working Group chairs, Stefan Håkansson, and the Team Contact, Dominique Hazaël-Massieux, for their support. The editors would like to thank Bernard Aboba, Taylor Brandstetter, Henrik Boström, Jan-Ivar Bruaroey, Karthik Budigere, Cullen Jennings, and Lennart Schulte for their contributions to this specification.