1934346 - VP9 encoder natively supports simulcast under certain conditions

Status: VERIFIED FIXED

(Core :: WebRTC: Audio/Video, defect, P2)

Description

[Andreas Pehrson [:pehrsons]]

We have so far not supported VP9 simulcast. In 134, we shipped a libwebrtc update containing a native simulcast in the libwebrtc libvpx VP9 encoder. This gets used even without the SimulcastEncoderAdapter that we normally use to control simulcast. The native mode uses SVC under the hood for more efficient encoding of multiple streams, so only works when the simulcast config can be translated to a vaild svc config by the codec.

Until we ship VP9 simulcast, we should disable this new native simulcast mode.

Comment 1

[Andreas Pehrson [:pehrsons]]

Attachment: Bug 1934346 - Rename NoTrialsConfig to better reflect reality. r?#webrtc-reviewers

Comment 2

[Andreas Pehrson [:pehrsons]]

Attachment: Bug 1934346 - Introduce a pref to turn off VP9 simulcast entirely. r?#webrtc-reviewers

In https://hg.mozilla.org/mozilla-central/rev/1c2fb06af8ed666efc145146927c83126eef1f17
a new mode was introduced in libwebrtc's libvpx VP9 encoder, that allows it to
encode simulcast layers natively under some conditions. The new pref lets us
turn that mode off to not inadvertently ship partial VP9 simulcast support.

Comment 3

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/2745456250d5
Rename NoTrialsConfig to better reflect reality. r=webrtc-reviewers,ng
https://hg.mozilla.org/integration/autoland/rev/07d2451f3780
Introduce a pref to turn off VP9 simulcast entirely. r=webrtc-reviewers,bwc

Comment 4

[Andreas Pehrson [:pehrsons]]

Attachment: Bug 1934346 - Rename NoTrialsConfig to better reflect reality.

Original Revision: https://phabricator.services.mozilla.com/D231231

Comment 5

[Andreas Pehrson [:pehrsons]]

Attachment: Bug 1934346 - Introduce a pref to turn off VP9 simulcast entirely.

In https://hg.mozilla.org/mozilla-central/rev/1c2fb06af8ed666efc145146927c83126eef1f17
a new mode was introduced in libwebrtc's libvpx VP9 encoder, that allows it to
encode simulcast layers natively under some conditions. The new pref lets us
turn that mode off to not inadvertently ship partial VP9 simulcast support.

Original Revision: https://phabricator.services.mozilla.com/D231232

Comment 6

[amarc]

https://hg.mozilla.org/mozilla-central/rev/2745456250d5
https://hg.mozilla.org/mozilla-central/rev/07d2451f3780

Comment 7

[Phabricator Automation]

beta Uplift Approval Request

• User impact if declined: 134 will inadvertently ship with partial simulcast support for VP9 in WebRTC
• Code covered by automated testing: no
• Fix verified in Nightly: no
• Needs manual QE test: yes
• Steps to reproduce for manual QE testing: On https://fippo.github.io/simulcast-playground/rid-as-mid?codec=vp9 after approving the camera prompt, two videos should be visible. One local, one remote. Verify with media.webrtc.simulcast.vp9.enabled=true where no remote video is visible (simulcast is on, but broken).
• Risk associated with taking this patch: Low
• Explanation of risk level: Maintaining old behavior by turning a feature off that landed upstream in libwebrtc.
• String changes made/needed: None
• Is Android affected?: yes

Comment 8

[Pulsebot]

https://hg.mozilla.org/releases/mozilla-beta/rev/f728bc5045ae
https://hg.mozilla.org/releases/mozilla-beta/rev/bd816f87569a

Comment 9

[Giorgia Nichita, Release Desktop QA]

Reproduced this issue on Win 10 using an affected nightly build from 2024-11-29 and following the steps from Comment 7.
Verified as fixed on Firefox 135.0a1 (20241209213901) and Firefox 134.0b8 (20241209091406) on WIn 10, macOS 11 and Ubuntu 22.04.