The code for determining outbound-rtp.active assumed, as the spec says,
that we have one RtpEncodingParameters per RTP stream. Unfortunately
SVC is currently implemented as one RtpEncodingParameters per SVC
layer. This causes a discrepency where we do correctly only have one
outbound-rtp stats object, but the lookup to check whether or not we are
"active" needs to look at more than a single encoding.
The bug is that if SVC layers are {inactive, active, active} then
stats reports outbound-rtp.active: false. With this fix, active: true is
reported if ANY of the SVC layers are active.
For singlecast or simulcast this CL has no change in behavior. In these
cases we have the same number of outbound-rtp and encodings and a simple
ssrc lookup does work.
The fix is exercised by unit tests and has also manually been confirmed:
- Singlecast tested by https://jsfiddle.net/henbos/nvd6p4j1/.
- Simulcast tested by https://crbug.com/webrtc/14628#c11.
- SVC tested by Google Meet and chrome://webrtc-internals/.
Bug: webrtc:14628
Change-Id: Ib89945caf29c8f4b85dd8a1120dcf8279296e4a3
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/282222
Reviewed-by: Harald Alvestrand <hta@webrtc.org>
Commit-Queue: Henrik Boström <hbos@webrtc.org>
Cr-Commit-Position: refs/heads/main@{#38569}
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