Bug 1933658 [wpt PR 49392] - Update stereo opus test to expect upmixi…

…ng., a=testonly

Automatic update from web-platform-tests
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 <htachromium.org>
Commit-Queue: Henrik Boström <hboschromium.org>
Cr-Commit-Position: refs/heads/main{#1388674}

--

wpt-commits: d97f56c5831beb33c9302d2dd2707554bd842116
wpt-pr: 49392

UltraBlame original commit: de89aa35ef835eeb58e01f3e96b8c4de7bef4e4d

testing/web-platform/tests/webrtc/RTCRtpEncodingParameters-codec-opus-stereo.https.html

@@ -562,6 +562,24 @@
 remoteTrack
 )
 ;
+/
+/
+The
+stereo
+opus
+decoder
+outputs
+stereo
+regardless
+of
+the
+signal
+on
+the
+/
+/
+wire
+.
 assert_equals
 (
 await
@@ -570,13 +588,19 @@
 t
 remoteTrack
 )
-1
+2
 '
 Remote
 track
 is
-also
+stereo
+(
+despite
+local
+track
+being
 mono
+)
 '
 )
 ;
@@ -590,6 +614,11 @@
 track
 with
 opus
+(
+stereo
+decoder
+upmix
+)
 '
 )
 ;