Questions on Scalability Mode and Media Capabilities

[bc-lee]

I have questions about Scalability Mode and Media Capabilities:

Let's say that a user agent advertises through the Media Capabilities API that the support of the encoding configuration below is power efficient.

{
  type: 'webrtc',
  video: {
    contentType: 'video/H264',
    width: 640,
    height: 480,
    bitrate: 100000,
    framerate: 30,
    scalabilityMode: "L1T3"
  }
};

However, when the user agent actually creates the encoder with the given Scalability Mode, it finds that the encoder does not support the given Scalability Mode.

In such a scenario, what would be the proper ways to handle this situation? Should we not create the encoder? Ignore the scalabilityMode? Or do something else? What if the power-efficient encoder is the only encoder for that codec?

Also, if the user agent can only determine whether a specific scalability mode is supported or not after the first few frames are encoded, what would be the proper ways to handle this situation? Should we not advertise the scalability mode? Or do something else?

[aboba]

Transferred to the Media Capabilities API Issue 208.