Being able to use active to turn on/off specific simulcast layers has been an oft requested feature from application developers, is in the spec and is supported in Chrome.

Workaround:

• set maxBitrate: 1 (use at least 1 since 0 appears to be ignored)
• and scaleResolutionDownBy: 240 for good measure (seems needed in single-layer case at least).

The downside of the workaround is it still signals the SFU that the browser tries to send data on that layer. 😕

Lack of support complicates web compat in the already complicated area of simulcast.

Lack of support complicates web compat in the already complicated area of simulcast.

Note the web compat table says Firefox supports active but this is incorrect (likely an artifact of us implementing the WebIDL but not the underlying code for it).

Its also supported (and working as expected) in safari starting with r73 (January 2019)

• Made RTCRtpSender.setParameters activate specific encodings
  https://developer.apple.com/safari/technology-preview/release-notes/#r73
  So firefox is the only one currently not supporting the active flag which is pretty nasty :)

Just chiming in here to mention that Jitsi is waiting this feature. Without it Firefox sends all simulcast streams all the time and wastes upstream bandwidth, e.g. the sender only appears in a small preview video at all receivers. So with this API Jitsi could then temporarily turn off the high and medium resolution could be marked inactive to save the send bandwidth.

Adding a note to implementer to double-check we don't send RTCP BYE when implementing this, since this appears to be an issue upstream still.

Depends on D156836

Try looks normal:

https://treeherder.mozilla.org/jobs?repo=try&revision=f337001b82d84b1c53ad54a4be31172d33fcb21c
https://treeherder.mozilla.org/jobs?repo=try&revision=e942210522400181f6ff09ea4f20bdd9460b6c0c
https://treeherder.mozilla.org/jobs?repo=try&revision=5a3657d5e35eb02402cb44334d9e4797a02edc01

Backed out for causing failures at test_peerConnection_scaleResolution_oldSetParameters.html.

Backout link: https://hg.mozilla.org/integration/autoland/rev/d62d1882c5affd1c699ae5147f97af3cc5d40e88

Pushwith failures: https://treeherder.mozilla.org/jobs?repo=autoland&resultStatus=testfailed%2Cbusted%2Cexception%2Cretry%2Cusercancel&revision=47c810ec80601ac59c5dca5d7df027b131e19e8c&selectedTaskRun=Cjgb_1WrQdW9VUAzzAiphQ.0

Failure log: https://treeherder.mozilla.org/logviewer?job_id=399526333&repo=autoland&lineNumber=5348

https://hg.mozilla.org/mozilla-central/rev/4a8af015edd8

Tracking issue for MDN work https://github.com/mdn/content/issues/23677