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Re: [webrtc-stats] Add stat to reflect the redundancy of FEC/RED data

From: minyuel via GitHub <sysbot+gh@w3.org>
Date: Thu, 04 Jan 2018 12:01:23 +0000
To: public-webrtc-logs@w3.org
Message-ID: <issue_comment.created-355265562-1515067282-sysbot+gh@w3.org>
Hi,

Sorry for this reply. I missed the earlier discussion until Harald brought this up again.

I would like to add a few comments.

1. In my opinion, to measure both necessity and sufficiency of FEC, we may need "Fraction of audio that is recovered from FEC" and "Fraction of FEC that is received but unused". Both of these have been implemented (but not standardized) in WebRTC: googSecondaryDecodedRate and googSecondaryDiscardedRate, respectively.

2. inband FEC of Opus is not on every packet. It is sent rather opportunistically. To quote "Packets that are determined to contain perceptually important speech information, such as onsets or transients, are encoded again at a lower bitrate and this re-encoded information is added to a subsequent packet."

3. So far, application can turn on/off FEC by SDP, but cannot control the degree of FEC, which is supposed to be adaptive to the network conditions.



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