mozilla-central/third_party/libwebrtc/video/g3doc/stats.md

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<!--* freshness: {owner: 'asapersson' reviewed: '2021-04-14'} *-->
# Video stats
Overview of collected statistics for [VideoSendStream] and [VideoReceiveStream].
## VideoSendStream
[VideoSendStream::Stats] for a sending stream can be gathered via `VideoSendStream::GetStats()`.
Some statistics are collected per RTP stream (see [StreamStats]) and can be of `StreamType`: `kMedia`, `kRtx`, `kFlexfec`.
Multiple `StreamStats` objects are for example present if simulcast is used (multiple `kMedia` objects) or if RTX or FlexFEC is negotiated.
### SendStatisticsProxy
`VideoSendStream` owns a [SendStatisticsProxy] which implements
`VideoStreamEncoderObserver`,
`RtcpStatisticsCallback`,
`ReportBlockDataObserver`,
`RtcpPacketTypeCounterObserver`,
`StreamDataCountersCallback`,
`BitrateStatisticsObserver`,
`FrameCountObserver`,
`SendSideDelayObserver`
and holds a `VideoSendStream::Stats` object.
`SendStatisticsProxy` is called via these interfaces by different components (e.g. `RtpRtcp` module) to update stats.
#### StreamStats
* `type` - kMedia, kRtx or kFlexfec.
* `referenced_media_ssrc` - only present for type kRtx/kFlexfec. The SSRC for the kMedia stream that retransmissions or FEC is performed for.
Updated when a frame has been encoded, `VideoStreamEncoder::OnEncodedImage`.
* `frames_encoded `- total number of encoded frames.
* `encode_frame_rate` - number of encoded frames during the last second.
* `width` - width of last encoded frame [[rtcoutboundrtpstreamstats-framewidth]].
* `height` - height of last encoded frame [[rtcoutboundrtpstreamstats-frameheight]].
* `total_encode_time_ms` - total encode time for encoded frames.
* `qp_sum` - sum of quantizer values of encoded frames [[rtcoutboundrtpstreamstats-qpsum]].
* `frame_counts` - total number of encoded key/delta frames [[rtcoutboundrtpstreamstats-keyframesencoded]].
Updated when a RTP packet is transmitted to the network, `RtpSenderEgress::SendPacket`.
* `rtp_stats` - total number of sent bytes/packets.
* `total_bitrate_bps` - total bitrate sent in bits per second (over a one second window).
* `retransmit_bitrate_bps` - total retransmit bitrate sent in bits per second (over a one second window).
* `avg_delay_ms` - average capture-to-send delay for sent packets (over a one second window).
* `max_delay_ms` - maximum capture-to-send delay for sent packets (over a one second window).
* `total_packet_send_delay_ms` - total capture-to-send delay for sent packets [[rtcoutboundrtpstreamstats-totalpacketsenddelay]].
Updated when an incoming RTCP packet is parsed, `RTCPReceiver::ParseCompoundPacket`.
* `rtcp_packet_type_counts` - total number of received NACK/FIR/PLI packets [rtcoutboundrtpstreamstats-[nackcount], [fircount], [plicount]].
Updated when a RTCP report block packet is received, `RTCPReceiver::TriggerCallbacksFromRtcpPacket`.
* `rtcp_stats` - RTCP report block data.
* `report_block_data` - RTCP report block data.
#### Stats
* `std::map<uint32_t, StreamStats> substreams` - StreamStats mapped per SSRC.
Updated when a frame is received from the source, `VideoStreamEncoder::OnFrame`.
* `frames` - total number of frames fed to VideoStreamEncoder.
* `input_frame_rate` - number of frames fed to VideoStreamEncoder during the last second.
* `frames_dropped_by_congestion_window` - total number of dropped frames due to congestion window pushback.
* `frames_dropped_by_encoder_queue` - total number of dropped frames due to that the encoder is blocked.
Updated if a frame from the source is dropped, `VideoStreamEncoder::OnDiscardedFrame`.
* `frames_dropped_by_capturer` - total number dropped frames by the source.
Updated if a frame is dropped by `FrameDropper`, `VideoStreamEncoder::MaybeEncodeVideoFrame`.
* `frames_dropped_by_rate_limiter` - total number of dropped frames to avoid bitrate overuse.
Updated (if changed) before a frame is passed to the encoder, `VideoStreamEncoder::EncodeVideoFrame`.
* `encoder_implementation_name` - name of encoder implementation [[rtcoutboundrtpstreamstats-encoderimplementation]].
Updated after a frame has been encoded, `VideoStreamEncoder::OnEncodedImage`.
* `frames_encoded `- total number of encoded frames [[rtcoutboundrtpstreamstats-framesencoded]].
* `encode_frame_rate` - number of encoded frames during the last second [[rtcoutboundrtpstreamstats-framespersecond]].
* `total_encoded_bytes_target` - total target frame size in bytes [[rtcoutboundrtpstreamstats-totalencodedbytestarget]].
* `huge_frames_sent` - total number of huge frames sent [[rtcoutboundrtpstreamstats-hugeframessent]].
* `media_bitrate_bps` - the actual bitrate the encoder is producing.
* `avg_encode_time_ms` - average encode time for encoded frames.
* `total_encode_time_ms` - total encode time for encoded frames [[rtcoutboundrtpstreamstats-totalencodetime]].
* `frames_dropped_by_encoder`- total number of dropped frames by the encoder.
Adaptation stats.
* `bw_limited_resolution` - shows if resolution is limited due to restricted bandwidth.
* `cpu_limited_resolution` - shows if resolution is limited due to cpu.
* `bw_limited_framerate` - shows if framerate is limited due to restricted bandwidth.
* `cpu_limited_framerate` - shows if framerate is limited due to cpu.
* `quality_limitation_reason` - current reason for limiting resolution and/or framerate [[rtcoutboundrtpstreamstats-qualitylimitationreason]].
* `quality_limitation_durations_ms` - total time spent in quality limitation state [[rtcoutboundrtpstreamstats-qualitylimitationdurations]].
* `quality_limitation_resolution_changes` - total number of times that resolution has changed due to quality limitation [[rtcoutboundrtpstreamstats-qualitylimitationresolutionchanges]].
* `number_of_cpu_adapt_changes` - total number of times resolution/framerate has changed due to cpu limitation.
* `number_of_quality_adapt_changes` - total number of times resolution/framerate has changed due to quality limitation.
Updated when the encoder is configured, `VideoStreamEncoder::ReconfigureEncoder`.
* `content_type` - configured content type (UNSPECIFIED/SCREENSHARE).
Updated when the available bitrate changes, `VideoSendStreamImpl::OnBitrateUpdated`.
* `target_media_bitrate_bps` - the bitrate the encoder is configured to use.
* `suspended` - shows if video is suspended due to zero target bitrate.
## VideoReceiveStream
[VideoReceiveStream::Stats] for a receiving stream can be gathered via `VideoReceiveStream::GetStats()`.
### ReceiveStatisticsProxy
`VideoReceiveStream` owns a [ReceiveStatisticsProxy] which implements
`VideoStreamBufferControllerStatsObserver`,
`RtcpCnameCallback`,
`RtcpPacketTypeCounterObserver`,
`CallStatsObserver`
and holds a `VideoReceiveStream::Stats` object.
`ReceiveStatisticsProxy` is called via these interfaces by different components (e.g. `RtpRtcp` module) to update stats.
#### Stats
* `current_payload_type` - current payload type.
* `ssrc` - configured SSRC for the received stream.
Updated when a complete frame is received, `FrameBuffer::InsertFrame`.
* `frame_counts` - total number of key/delta frames received [[rtcinboundrtpstreamstats-keyframesdecoded]].
* `network_frame_rate` - number of frames received during the last second.
Updated when a frame is ready for decoding, `FrameBuffer::GetNextFrame`. From `VCMTiming`:
* `jitter_buffer_ms` - jitter delay in ms: this is the delay added to handle network jitter
* `max_decode_ms` - the 95th percentile observed decode time within a time window (10 sec).
* `render_delay_ms` - render delay in ms.
* `min_playout_delay_ms` - minimum playout delay in ms.
* `target_delay_ms` - target playout delay in ms. Max(`min_playout_delay_ms`, `jitter_delay_ms` + `max_decode_ms` + `render_delay_ms`).
* `current_delay_ms` - actual playout delay in ms.
* `jitter_buffer_delay_seconds` - total jitter buffer delay in seconds: this is the time spent waiting in the jitter buffer [[rtcinboundrtpstreamstats-jitterbufferdelay]].
* `jitter_buffer_emitted_count` - total number of frames that have come out from the jitter buffer [[rtcinboundrtpstreamstats-jitterbufferemittedcount]].
Updated (if changed) after a frame is passed to the decoder, `VCMGenericDecoder::Decode`.
* `decoder_implementation_name` - name of decoder implementation [[rtcinboundrtpstreamstats-decoderimplementation]].
Updated when a frame is ready for decoding, `FrameBuffer::GetNextFrame`.
* `timing_frame_info` - timestamps for a full lifetime of a frame.
* `first_frame_received_to_decoded_ms` - initial decoding latency between the first arrived frame and the first decoded frame.
* `frames_dropped` - total number of dropped frames prior to decoding or if the system is too slow [[rtcreceivedrtpstreamstats-framesdropped]].
Updated after a frame has been decoded, `VCMDecodedFrameCallback::Decoded`.
* `frames_decoded` - total number of decoded frames [[rtcinboundrtpstreamstats-framesdecoded]].
* `decode_frame_rate` - number of decoded frames during the last second [[rtcinboundrtpstreamstats-framespersecond]].
* `decode_ms` - time to decode last frame in ms.
* `total_decode_time_ms` - total decode time for decoded frames [[rtcinboundrtpstreamstats-totaldecodetime]].
* `qp_sum` - sum of quantizer values of decoded frames [[rtcinboundrtpstreamstats-qpsum]].
* `content_type` - content type (UNSPECIFIED/SCREENSHARE).
* `interframe_delay_max_ms` - max inter-frame delay within a time window between decoded frames.
Updated before a frame is sent to the renderer, `VideoReceiveStream2::OnFrame`.
* `frames_rendered` - total number of rendered frames.
* `render_frame_rate` - number of rendered frames during the last second.
* `width` - width of last frame fed to renderer [[rtcinboundrtpstreamstats-framewidth]].
* `height` - height of last frame fed to renderer [[rtcinboundrtpstreamstats-frameheight]].
* `estimated_playout_ntp_timestamp_ms` - estimated playout NTP timestamp [[rtcinboundrtpstreamstats-estimatedplayouttimestamp]].
* `sync_offset_ms` - NTP timestamp difference between the last played out audio and video frame.
* `freeze_count` - total number of detected freezes.
* `pause_count` - total number of detected pauses.
* `total_freezes_duration_ms` - total duration of freezes in ms.
* `total_pauses_duration_ms` - total duration of pauses in ms.
* `total_inter_frame_delay` - sum of inter-frame delay in seconds between rendered frames [[rtcinboundrtpstreamstats-totalinterframedelay]].
* `total_squared_inter_frame_delay` - sum of squared inter-frame delays in seconds between rendered frames [[rtcinboundrtpstreamstats-totalsquaredinterframedelay]].
`ReceiveStatisticsImpl::OnRtpPacket` is updated for received RTP packets. From `ReceiveStatistics`:
* `total_bitrate_bps` - incoming bitrate in bps.
* `rtp_stats` - RTP statistics for the received stream.
Updated when a RTCP packet is sent, `RTCPSender::ComputeCompoundRTCPPacket`.
* `rtcp_packet_type_counts` - total number of sent NACK/FIR/PLI packets [rtcinboundrtpstreamstats-[nackcount], [fircount], [plicount]].