Re: FW: [rtcweb] How to signal RTX SSRCs with simulcast

Could you elaborate a bit to help me understand why that would be needed for FLEX-FEC when using RepairedRtpStreamId?

Is it that you get explicit indication in SDP, like "a=rid:<rid-id> send pt=<media-fmt>,<redundancy-fmt> ..." when using RtpStreamId for both original and redundancy RTP stream?

I guess that use of RtpStreamId or RepairedRtpStreamId on RTP level (in the RTP and RTCP packets) should not matter much, neither for FLEX-FEC nor RTX, as long as it is clearly defined what it means?

/Bo
(as individual)

> -----Original Message-----
> From: Iñaki Baz Castillo [mailto:[email protected]]
> Sent: den 13 mars 2017 11:46
> To: Bo Burman <[email protected]>
> Cc: mmusic ([email protected]) <[email protected]>; Taylor Brandstetter ([email protected])
> <[email protected]>; [email protected]; [email protected]
> Subject: Re: [MMUSIC] FW: [rtcweb] How to signal RTX SSRCs with simulcast
> 
> 2017-03-13 10:56 GMT+01:00 Bo Burman <[email protected]>:
> > I’m personally slightly inclined to suggest always using
> > RepairedRtpStreamId in the rtx redundancy RTP stream to relate it to
> > the original RTP stream (second “if” bullet above), mainly to avoid
> > having to change interpretation of RtpStreamId based on the optional
> > presence of RepairedRtpStreamId. I’m of course open to arguments.
> 
> Personally I prefer option A (use a shared RtpStreamId). My rationale:
> 
> If we go with option B (RepairedRtpStreamId) then we will need something similar when it comes to FLEX-FEC [*]:
> 
>         v=0
>         o=ali 1122334455 1122334466 IN IP4 fec.example.com
>         s=2-D Parity FEC with no in band signalling Example
>         t=0 0
>         m=video 30000 RTP/AVP 100 110
>         c=IN IP4 233.252.0.1/127
>         a=rtpmap:100 MP2T/90000
>         a=rtpmap:110 flexfec/90000
>         a=fmtp:110 L:5; D:10; ToP:2; repair-window:200000
>         a=ssrc:1234
>         a=ssrc:2345
>         a=ssrc-group:FEC-FR 1234 2345
> 
> 
> For me it's to think in RtpStreamId as "the identificator of a media stream and, optionally, also the identificator of the RTX
> stream and FEC stream of such a media stream".
> 
> 
> 
> [*] https://tools.ietf.org/html/draft-ietf-payload-flexible-fec-scheme-03
> 
> 
> --
> Iñaki Baz Castillo
> <[email protected]>
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