Currently, when only max bitrate available and min bitratea & target
bitrate are missing from encoding config, the target bitrate is decided
by the calculation from GetSimulcastConfig() according to width/height/qp.
The max bitrate doesn't play a role here other than ensure target < max.
This will make the target bitrate cap at some calculated number even
when control message gives much larger allocation through max bitrate.
In our cases, the L0 (at 180p) is capped at 80-90kbps even control
message gives L0's max bitrate over 300kbps. This under-use of bandwidth
happens to all layer other than top layer. Top layer will be compensated
with all the left bandwidth up to max at last.
Since in web api, we cannot pass down either min bitrate or target bitrate
(https://developer.mozilla.org/en-US/docs/Web/API/RTCRtpEncodingParameters).
We propose a new logic to take max bitrate into consideration in this case,
use 3/4 max bitrate or calculated target bitrate whichever is larger.
Bug: None
Change-Id: I2234b4636daa379fd47d4bbe764cf8307b9a1ea4
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/186161
Reviewed-by: Ilya Nikolaevskiy <ilnik@webrtc.org>
Reviewed-by: Rasmus Brandt <brandtr@webrtc.org>
Commit-Queue: Ilya Nikolaevskiy <ilnik@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#32308}
c401923f3e