PSA: New standardized stats in M75

[Henrik Boström]

The standard getStats() API, meaning the promise-based API in Chrome, has several new metrics shipping in M75 - with more metrics planned for M76.

This is part of the ongoing work to make the non-standard getStats() API obsolete by "unblocking migration": https://bugs.chromium.org/p/webrtc/issues/detail?id=10428

The new metrics include:

• Acceleration/deceleration of playout speed

• insertedSamplesForDeceleration/removedSamplesForAcceleration: Meant to replace non-standard googPreemptiveExpandRate and googAccelerateRate.

• Synthesized samples produced in order to conceal packet loss

• silentConcealedSamples: Use together with concealedSamples to determine portion of concealments are occuring while the stream is audible or silent; meant to replace non-standard googSpeechExpandRate.

• Retransmitted packets/bytes

• retransmittedPacketsSent/retransmittedBytesSent: Used together with bytesSent to compare the non-retransmitted output with the expected output of the encoder; meant to replace non-standard googActualEncBitrate.

• Encoding

• totalEncodeTime: Used together with framesEncoded to calculate average encode time; meant to replace non-standard googAvgEncodeMs and the two should make googEncodeUsagePercent not needed.

• Last packet received

• lastPacketReceivedTimestamp: Can detect large unexpected delays through polling; meant to replace googInterframeDelayMax.

• Error correction (FEC)

• fecPacketsReceived/fecPacketsDiscarded: Meant to replace non-standard googSecondaryDecodedRate and googSecondaryDiscardedRate.

• Screenshare

• contentType (provisional): Meant to replace googContentType.

[Henrik Boström]

Sorry, correction - some of these metrics are in M76, not M75. Namely:

• insertedSamplesForDeceleration and removedSamplesForAcceleration
• silentConcealedSamples
• fecPacketsReceived and fecPacketsDiscarded

These are already available in Canary.

[Xiaosha Xing]

Isn't it a part of audio receiver track? Not found it though.