Re: ORTC and FEC/RTX/RED

On 22/10/2014 21:59, Bernard Aboba wrote:
> On Oct 22, 2014, at 12:34 PM, Sergio Garcia Murillo 
> <sergio.garcia.murillo@gmail.com 
> <mailto:sergio.garcia.murillo@gmail.com>> wrote:
>
>> Hi,
>>
>> I disagree, It is not possible just by looking at the SDP to know 
>> which ssrc is from the media and which is from rtx. While for 
>> WebRTC-endpoints it may be irrelevant because, as you say, you can 
>> wait for the RTP data to check the payload type and match the ssrc, 
>> we have seen that it is a must have for interoperability with ORTC.
>>
>> Best regards
>> Sergio
>
> [BA] Currently FEC/RED/RTX capabilities are in part discovered and 
> configured as codecs, which can include a payload type. In addition 
> the SSRCs can be configured. As Inaki discovered, there is no "apt" 
> parameter defined in RED, but that could be added. So putting aside 
> the issue of whether the present design is awkward, is there a loss of 
> functionality from WebRTC 1.0?
>
> My take so far is that as long as the matching rules guide the 
> RTX/FEC/RED streams to the same RtpReceiver as the media streams they 
> are associated with, we are OK. In the case of multiple sources this 
> could be a bit tricky if the receivers are sharing payload types, but 
> that is where the SSRC configuration comes

 From an implementation point of view I would prefer to move out of the 
clunkiness of WebRTC 1.0, and be able to de-multiplex per ssrc only, 
without having to take a look at the pt.

Best regards
Sergio