Re: WebRTC-SVC: "S" modes and simulcast using a single SSRC

The RIDs aren't necessary in all packets of the same stream. in fact once
the receiver acknowledges receipt of a stream with a MID or RID, the sender
can remove the MIDs and RIDs from future packets carrying the same SSRC (as
the relationship between SSRC -> MID and SSRC -> RID has been established
by the receiver).
to that extent, you should not send different layers using the same SSRC
and relying on them having different RIDs, as receivers might also be
ignoring the RID and MID extensions once the relationship to SSRC is
established. Not sure if SVC would be different than regular simulcast in
this regard, but worth mentioning.

On Wed, Jul 24, 2019 at 11:30 AM Bernard Aboba <>

> Florent said:
> "I don't think there are any issues adding S modes as it's just a special
> case of spatial layers which we intend to support already."
> [BA] It sounds like there is interest in adding the "S" modes back.  I
> will prepare a PR for that and would appreciate your review.
> "I would love to continue the discussion about this at TPAC and possibly
> include some time to discuss APIs to improve the application's control over
> each spatial or temporal layer's parameters."
> [BA] If you have specific Issues or PRs relating to the WebRTC-SVC draft,
> can you file them in the repo?  TPAC is scheduled earlier this year so it
> will be upon us before we know it 😉

Received on Tuesday, 30 July 2019 18:10:46 UTC