Re: Issue 456 (Move degradationPreference from RTCRtpParameters to RTCRtpEncodingParameters)

Murillo128 said:

"Shouldn't this be moved to the encodings? It would make sense to be able to have different degradation preferences for each layer in a simulcast encoding"

[BA] In WebRTC 1.0 (and then ORTC) we moved degradationPreference from RTCRtpEncodingParameters to RTCRtpParameters.

The thinking is that the preference for framerate versus resolution needs to be consistent within an RtpSender.

That is, it does not make sense for one simulcast layer to prefer framerate and another one to prefer resolution.

In the case of SVC, the layers relate to each other, so they can't have their own distinct values of degradationPreference.
For example, if the base layer framerate changes, a temporal extension layer will also change framerate.
So one can argue that setting degradationPreference differently for SVC layers should result in an exception being thrown.

Note the priority remains within RTCRtpEncodingParameters, so this can be different between layers (though it is more common to preferentially protect the baser layers with RTX or FEC rather than marking preferentially).