commit b23b3dd9b1dcbc9cceb5a5c34972fef7ecafedc1
author Henrik Boström <hbos@webrtc.org> Fri Oct 04 12:10:02 2024
committer WebRTC LUCI CQ <webrtc-scoped@luci-project-accounts.iam.gserviceaccount.com> Fri Oct 04 13:53:55 2024
tree 672eacadaa2f9f54a23e971b1d6a9cfe8a3cc13c
parent d9b04adbdbb5e85a86acb422977423d2c4476bcb

Improve simulcast CPU adaptation when requested_resolution API is used.

In simulcast, BW adaptation causes layers to be disabled rather than
downscaling layers. But CPU adaptation restricts the resolution of all
layers, this means that a 540p restriction on 180p:360p:720p results in
180p:360p:540p, which is fine but a) it's inconsistent with BW
adaptation and b) it's not ideal for performance, because non power of
two scaling factors means we can't use a single encoder instance to
produce all layers (the CPU adaptation could actually result in even
more CPU usage and further adaptation as a result).

This CL disables top layers by limiting `max_num_layers` based on
`restrictions_` and the layers' `requested_resolution`, the end result
is 180p:360p:- when CPU adaptation kicks in.

Note that the problem described (and therefore the solution) is
specific to the `requested_resolution` API. If instead the
`scale_resolution_down_by` API is used, all scaling is relative and we
get 135p:270p:540p, which is problematic for other reasons (180p and
360p no longer sent, middle layer no longer HW accelerated).

Bug: webrtc:366415118
Change-Id: I2e238b1b87470413c21623b21d0ce20eadf6c8c7
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/364660
Commit-Queue: Henrik Boström <hbos@webrtc.org>
Reviewed-by: Ilya Nikolaevskiy <ilnik@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#43172}