Re: [rtcweb] Proposed Plan for Usage of SDP and RTP - Lower level API minus SDP

[Harald Alvestrand <[e-mail]>]

On 03/08/2013 03:56 AM, Silvia Pfeiffer wrote:
> On Fri, Mar 8, 2013 at 11:28 AM, Timothy B. Terriberry 
> <[e-mail] <mailto:[e-mail]>> wrote:
>
>     Silvia Pfeiffer wrote:
>
>         For example: the programmer wants to say - I want to get this
>         video
>         resolution, this audio bitrate & channels, I want to use this
>         camera and
>         this microphone for this call. Having to manipulate SDP
>         directly for
>         this is a programmer's nightmare.
>
>
>     I would like to point out that the currently proposed W3C APIs do
>     not require (or even allow) SDP manipulation for _any_ of this,
>     with the possible exception of audio bitrate (which, as we've long
>     discussed, should actually be adapted in real-time based on
>     available bandwidth as determined by congestion control, with some
>     app-provided way to set priorities that will _not_ be based on
>     SDP... the number in SDP merely defines the limits of what's
>     possible).
>
>
> Is there any way for the Web developer to influence the negotiation 
> of, say, the video resolution? For example, if the video is displayed 
> in a 160x120 video element, then it makes no sense to receive anything 
> larger than that resolution. I was under the impression that this 
> would have to be done through manipulating SDP?

See draft-alvestrand-constraints-resolution for 3 ways of doing this, 2 
of which have no SDP manipulation.

I think SDP manipulation is the messiest of the 3; the first one (out of 
band messaging) can be used on Chrome today when creating video streams. 
(We won't implement changing of constraints until we have an agreed-upon 
API; there are enough other things that need doing that we can wait 
until there's text in the spec before starting to implement it.)