Update stereo opus test to expect upmixing.
Update the test that sends and receives a local mono track with opus
that on the remote side the channelCount is 2 because the opus decoder
performs upmixing.
This strange behavior is option 1) discussed in
w3c/webrtc-pc#3010. This allows for some
optimization and simplifications which aids in virtual audio SSRC use
case of flip-flopping between mono and stereo signals on the wire and
not having to re-initialize the decoder (which could cause glitches).
The vibe from the November Virtual Interim
(https://www.w3.org/2024/11/19-webrtc-minutes.html#561c) was to
standardize what libwebrtc does when stereo is enabled, and this is
what it does.
Note: We still fail the test today though because "stereo opus" has not
been enabled-by-default. When it is the expectation is that we pass
both of these tests.
Bug: webrtc:379996136
Change-Id: Ibd6ee91a59d7c673bf53ad2302ba33f16b8b4ede
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/6049355
Reviewed-by: Harald Alvestrand hta@chromium.org
Commit-Queue: Henrik Boström hbos@chromium.org
Cr-Commit-Position: refs/heads/main@{#1388674}