Re: [Perc] Double PERC draft 5 and webrtc audio FEC

> On Jun 29, 2017, at 1:46 PM, Sergio Garcia Murillo <sergio.garcia.murillo@gmail.com> wrote:
> 
> Hi all,
> 
> In the new double encryption draft that Cullen has just submitted, it is says:
> 
> 7.3.  FEC
> 
>    The algorithms recommended in [I-D.ietf-rtcweb-fec] for audio work
>    with no additional considerations.
> 
> But in ietf-rtcweb-fec it recommends to use rfc 2198 RTP payload for redundant audio data. The problem is that RED only protects the payload, and any RTP header extension will not be protected. That will prevent RED to work HBH as the receiver end will not be able to recover the OHB and perform the inner crypto on the recovered packet.
> Best regards
> 

Let me just ignore for a second that we disagree on best way to do RED when using SRTP (never mind PERC).  My read of draft-ietf-rtcweb-fec was that 2198 is a "MAY" be used but that the "RECOMMENDED" approach for opus in hybrid mode (which is preferred for WebRTC) was just to use the FEC that is build into Opus.  All the data I have seen suggests that opus FEC outperforms RED in pretty much all ways RED typically gets used so this seems somewhat reasonable. 

But that said, if you think the draft should mention RED, glad to add it. Plus the sentence in the draft probably needs to explain what works means in this context. 

> Sergop
> 
> _______________________________________________
> Perc mailing list
> Perc@ietf.org
> https://www.ietf.org/mailman/listinfo/perc