Re: [rtcweb] Resolution negotiation - a contribution

[Harald Alvestrand <[e-mail]>]

On 04/12/2012 08:19 PM, Stephan Wenger wrote:
> Hi Harald,
> Thanks for this strawman.  I believe it should work, but I fail to see how
> a two dimensional negotiation requirement (negotiating max values for
> framerate and image size--which, in turn, also has two-dimensional
> properties) leads to better interop than a one dimensional negotiation
> (pixels per second processing requirement).
Stephan,

I do not see this (or the requirement from the use-cases document) first 
and foremost a decoder complexity negotiation; it is a negotiation of 
how much data it is useful to send, given the recipient's intended use 
of that data.

For instance, in Google+ Hangouts, we use a similar function to make 
sure the participants who are not currently displayed in large format on 
anyone's screen only send the data needed to display the "thumbnail"; 
this represents a huge saving in bandwidth at our central servers.

It just happens that the decoding complexity of the VP8 codec is 
sufficiently linear with the number of pixels displayed that we don't 
see any advantage in encumbering the negotiation of that codec with 
extra features like "profiles" - but that's a discussion for PAYLOAD, 
not RTCWEB.