[webrtc-pc] setParameters woes

fippo has just created a new issue for https://github.com/w3c/webrtc-pc:

== setParameters woes ==
http://w3c.github.io/webrtc-pc/#dom-rtcrtpsender-setparameters

while I was overjoyed to learn that I do not have to go through an O/A cycle to change the bandwidth I am sending I have a couple of questions.

* what are the parameters modifyable by setParameters? I assume ptime (within the bounds of maxptime from the sdp), bitrate (within the bounds of b= from the SDP) and frameRate (within the range of max-fr in the sdp for vp8).After writing this i found http://w3c.github.io/webrtc-pc/#dom-rtcrtpencodingparameters which gives me such a list.
* should the algorithm describe that those values must be checked against their maximums?
* how does it learn (without parsing the SDP) the maximum value that can be set? this would imply read-only maximum* and read-write current*

Please view or discuss this issue at https://github.com/w3c/webrtc-pc/issues/1248 using your GitHub account