[rtcweb] Support of video with different resolutions

[Christer Holmberg <[e-mail]>]

Hi,

Section 4.3.3.1 (description of the 'Video conferencing system with
central server' use-case) of the use-case-and-requirements draft
contains a note, describing different mechanisms for providing
video streams with different resolution.

                "Note: This use-case adds requirements on support for fast stream switches F7, on encryption of media and on ability to
                traverse very restrictive FWs. There exist several solutions that enable the server to forward one high resolution and several low
                resolution video streams: a) each browser could send a high resolution, but scalable stream, and the server could send just the
                base layer for the low resolution streams, b) each browser could in a simulcast fashion send one high resolution and one low
                resolution stream, and the server just selects or c) each browser sends just a high resolution stream, the server transcodes into
low resolution streams as required."
If we want to support content sent in different resolutions, the question is whether we need to mandate the browser to support a specific
mechanism.

As shown in the note, there are basically 3 mechanism: SVC, simulcast and "local transcoding".

The "local transcoding" alternative doesn't put any requirements on
browsers. The SVC and simulcast alternatives would.


However, the "local transcoding" alternative will consume lots of resources,

and as far as I know none of the proposed MTI video codecs support SVC.



Some people have indicated support for simulcast in the past, but it would

be nice to get a wider view.

Opinions?

Regards,

Christer