Re: [rtcweb] SDP and ssrc-group,

[Sergio Garcia Murillo <[e-mail]>]

On 22/10/2014 18:06, Makaraju, Maridi Raju (Raju) wrote:
>
> Hi Raju
>
> I foresee that when we start working on FEC we will end up using a 
> different ssrc to avoid asking retransmissions of FEC redundant data. 
> So 3 ssrcs will be needed for each media stream.
> */<Raju2> /*
>
> */But for FEC, you will have to specify a different a=ssrc-group:FID. 
> So, I think a=ssrc-group:FID will still have 2 ssrcs only./*
>
> */</Raju2>/*
>
Indeed, in fact I was proposing in another thread to use a the 
ssrc-group:FEC (and remove the RED altogether).

> Regarding the ftmp ssrc attribute, syntactically it solves perfectly 
> the problem (even if we have fec in its own ssrc), but I am not sure 
> if semantically it is the intended usage, as it seems more to define 
> format attributes for an specific ssrc an not to restrict the usage of 
> the payload type to that ssrc.
> */<Raju2>/*
>
> */Whatever was the initial intended purpose, I think it can be put to 
> use it for this (new) usage. By definition, retransmission payload can 
> only be sent on one ssrc only and also the original payloads can only 
> be sent on one ssrc only. So, assuming there is only one 
> retransmission payload independent of  # of original payloads, just 
> associating it to an ssrc unambiguously maps both ssrcs. But still, an 
> explicit mapping for all ssrcs can also be done, thought which is 
> unnecessary I think. /*
>
> */</Raju2>/*
>
I am also fine, just not sure if everyone else would agree.

Best regards
Sergio