Issue 262: framerateBias, degradationPreference and Simulcast

https://github.com/openpeer/ortc/issues/262

In WebRTC 1.0, degradationPreference is now used instead of framerateBias (see:   http://w3c.github.io/webrtc-pc/ ).

To ensure compatibility between ORTC and WebRTC 1.0, the proposal is to add the WebRTC 1.0 definition of RTCDegradationPreference to Section 9.5 of the ORTC specification (and remove framerateBias):

RTCDegradationPreference can be used to indicate the desired choice between degrading resolution and degrading framerate when bandwidth is constrained.

enum RTCDegradationPreference {

    "maintain-framerate<http://internaut.com:8080/~baboba/ortc/github/ortc.html#idl-def-RTCDegradationPreference.maintain-framerate>",

    "maintain-resolution<http://internaut.com:8080/~baboba/ortc/github/ortc.html#idl-def-RTCDegradationPreference.maintain-resolution>",

    "balanced<http://internaut.com:8080/~baboba/ortc/github/ortc.html#idl-def-RTCDegradationPreference.balanced>"

};
Enumeration description

maintain-framerate


Degrade resolution in order to maintain framerate.

maintain-resolution


Degrade framerate in order to maintain resolution.

balanced


Degrade a balance of framerate and resolution.


There is another question as well, which is whether RTCDegradationPreference should remain within RTCRtpEncodingParameters, or whether it should instead migrate to RTCRtpParameters.  The argument for moving it is that degradation preference needs to be consistent between layers, so it is something that is set for the RTCRtpSender in general.  If it is moved, here is what RTCRtpParameters would look like:


dictionary RTCRtpParameters {

             DOMString                                 muxId = "";

             sequence<RTCRtpCodecParameters>           codecs;

             sequence<RTCRtpHeaderExtensionParameters> headerExtensions;

             sequence<RTCRtpEncodingParameters>        encodings;

             RTCRtcpParameters                         rtcp;

             RTCDegradationPreference                  degradationPreference = "balanced";

};