- From: Harald Alvestrand via GitHub <sysbot+gh@w3.org>
- Date: Mon, 18 Jan 2021 07:38:21 +0000
- To: public-webrtc-logs@w3.org
For offer/answer, the relevant text is in section 7.1 of RFC 7587:
o The "stereo" parameter is a unidirectional receive-only parameter.
When sending to a single destination, a sender MUST NOT use stereo
when "stereo" is 0. Gateways or senders that are sending the same
encoded audio to multiple destinations SHOULD NOT use stereo when
"stereo" is 0, as this would lead to inefficient use of network
resources. The "stereo" parameter does not affect
interoperability.
As for what a missing "stereo=1" attribute means: Section 6.1:
stereo: specifies whether the decoder prefers receiving stereo or
mono signals. Possible values are 1 and 0, where 1 specifies that
stereo signals are preferred, and 0 specifies that only mono
signals are preferred. Independent of the stereo parameter, every
receiver MUST be able to receive and decode stereo signals, but
sending stereo signals to a receiver that signaled a preference
for mono signals may result in higher than necessary network
utilization and encoding complexity. If no value is specified,
the default is 0 (mono).
So receiving stereo is mandatory to support, but sending stereo when stereo=1 is missing is "allowed, but you really should have a strong reason to do so".
I think that once stereo is fully supported in the pipeline, we should put "stereo=1" into the default FMTP line for Opus.
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Received on Monday, 18 January 2021 07:38:22 UTC