[webrtc-svc] how to specify L3T3? (#61)

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

== how to specify L3T3? ==
```
pc.addTransceiver(stream.getVideoTracks()[0], {
  direction: 'sendonly',
  sendEncodings: [
    {rid: 'q', scaleResolutionDownBy: 4.0, scalabilityMode: 'L3T3'}
    {rid: 'h', scaleResolutionDownBy: 2.0, scalabilityMode: 'L3T3'},
    {rid: 'f', scalabilityMode: 'L3T3'},
  ]    
});
```
seems like an odd way to do it since each spatial layer is defined by a separate sendencoding.
One can not specify a single encoding either
pc.addTransceiver(stream.getVideoTracks()[0], {
  direction: 'sendonly',
  sendEncodings: [
    {scalabilityMode: 'L3T3'}  ]    
});
```
since that looses the ability to control the downscaling factor (which might be tolerable) and the rid.

Please view or discuss this issue at https://github.com/w3c/webrtc-svc/issues/61 using your GitHub account


-- 
Sent via github-notify-ml as configured in https://github.com/w3c/github-notify-ml-config