[webrtc-svc] Make SVC testable (#111)

jan-ivar has just created a new issue for https://github.com/w3c/webrtc-svc:

== Make SVC testable ==
The spec [says](https://w3c.github.io/webrtc-svc/#getparameters): _"After the initial negotiation has completed, [getParameters](https://www.w3.org/TR/webrtc/#dom-rtcrtpsender-getparameters)() returns the currently configured [scalabilityMode](https://w3c.github.io/webrtc-svc/#dom-rtcrtpencodingparameters-scalabilitymode) value for each encoding in encodings which had a value before the initial negotiation. This MAY be different from the values requested in [addTransceiver](https://www.w3.org/TR/webrtc/#dom-rtcpeerconnection-addtransceiver)() or [setParameters](https://www.w3.org/TR/webrtc/#dom-rtcrtpsender-setparameters)(). For example, if the codecs selected during negotiation do not include an encoder supporting the desired [scalabilityMode](https://w3c.github.io/webrtc-svc/#dom-rtcrtpencodingparameters-scalabilitymode) value, the user agent MAY select another value."_

The first _"MAY"_ is broad, and makes it impossible to write WPT tests for SVC behavior, as even a UA that always returns "L1T1" is compliant.

In contrast, the example given seems sensible, deterministic, and testable using [mediaCapabilities](https://w3c.github.io/webrtc-svc/#example-5), like we recently did for MediaRecorder in https://github.com/web-platform-tests/wpt/pull/57320: If it says supported there then it MUST be supported here.

**Proposal:** Restrict the MAY to the example.

Something like: _"This MAY be different from the values requested in [addTransceiver](https://www.w3.org/TR/webrtc/#dom-rtcpeerconnection-addtransceiver)() or [setParameters](https://www.w3.org/TR/webrtc/#dom-rtcrtpsender-setparameters)() only if the codecs selected during negotiation do not include an encoder supporting the desired [scalabilityMode](https://w3c.github.io/webrtc-svc/#dom-rtcrtpencodingparameters-scalabilitymode) value."_

Please view or discuss this issue at https://github.com/w3c/webrtc-svc/issues/111 using your GitHub account


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Received on Tuesday, 27 January 2026 00:52:00 UTC