Re: [rtcweb] JSEP question: How to set up simulcast for server-originated calls?

[Harald Alvestrand <[e-mail]>]

On 11/05/2018 02:07 PM, Sergio Garcia Murillo wrote:
> On 05/11/2018 12:45, Harald Alvestrand wrote:
>> I do fear that simulcast will continue to affect parts of the spec that
>> we don't expect it to. But we don't have the luxury of specifying it
>> halfway; either we rip it out altogether, or we specify it in enough
>> detail for interoperable implementation.
>
> I agree to that. If we are able to find an "easy" (i.e. not
> introducing too many changes) I would not have any issues adding
> support to that.
>
> Something like:
>
> - Browser adds a track via addTrack
>
> - Browser call SRD with a recv simulcast m-line offer
>
> - The transceiver is created with one send encoding per rid offered by
> the SFU with default values and all send encodings except first one
> with active=false (this would be the only required change)
>
> ----- browser encodes/sends a single rtp stream, same as if the remote
> offer was a non simulcast stream--
>
> -Browser calls sender.getParameters(), modifies the desired send
> encoding parameters ( scaleResolutionDownBy,  maxFramerate,
> maxBitrate, etc) and enables them by setting active=true
>
> Would this approach fulfill the requirements?

Yes, I believe so. This is also precisely what I was proposing, except
for the requirement to call addTrack.

Note that our current spec text says that when addTrack is called, a
transceiver is created with the max number of simulcast encodings set to
1, and that this number cannot be increased. This would have to change.