Re: [rtcweb] #27: Section 6.2 FEC

"Roni Even" <ron.even.tlv@gmail.com> Mon, 26 August 2013 18:51 UTC

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From: "Roni Even" <ron.even.tlv@gmail.com>
To: "'Colin Perkins'" <csp@csperkins.org>, "'rtcweb issue tracker'" <trac+rtcweb@grenache.tools.ietf.org>
References: <066.f62f1912f660dbc0c28343d2955a2ef5@trac.tools.ietf.org> <081.60ad42bfcba9b4972ad06bf3f62ca73e@trac.tools.ietf.org> <5A2C089B-BBFF-42D1-949A-AD2984EE3E90@csperkins.org>
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Date: Mon, 26 Aug 2013 21:48:36 +0300
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Cc: draft-ietf-rtcweb-rtp-usage@tools.ietf.org, rtcweb@ietf.org
Subject: Re: [rtcweb] #27: Section 6.2 FEC
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So for FEC need to support RFC5956 and RFC6364 for signaling but no specific
FEC scheme
Roni Even

> -----Original Message-----
> From: rtcweb-bounces@ietf.org [mailto:rtcweb-bounces@ietf.org] On
> Behalf Of Colin Perkins
> Sent: 26 August, 2013 6:51 PM
> To: rtcweb issue tracker
> Cc: draft-ietf-rtcweb-rtp-usage@tools.ietf.org; rtcweb@ietf.org
> Subject: Re: [rtcweb] #27: Section 6.2 FEC
> 
> On 26 Aug 2013, at 08:18, rtcweb issue tracker
> <trac+rtcweb@trac.tools.ietf.org> wrote:
> > #27: Section 6.2 FEC
> >
> >
> > Comment (by bernard_aboba@hotmail.com):
> >
> > [Magnus Westerlund]
> >
> > Bernard, this is the WG consensus that we so far have arrived on. If you
> have a proposal regarding FEC, please make it and lets see if we can reach
> consensus on such a proposal.
> >
> > However, I fail to see how this is generally problematic. Retransmission
will
> cover certain parts of the deployment cases when the transport RTT and
> delay does not prevent it from being able to repair in a timely fashion.
FEC
> clearly covers transport characteristics where retransmission will show
its
> shortcomings. If one want improved transport performance in those cases
> clearly a common implemented FEC solution is desired.
> >
> > [BA] FEC is discussed in Sections 1.1.7 and 3.3 of draft-roach-mmusic-
> unified-plan, with examples how it might be declared using SDP, so I found
it
> a bit odd that draft-ietf-rtcweb-rtp-usage only had recommendations for
> RTX, not FEC.  For example, Section 1.1.7 says:
> >
> >    For robust applications, techniques like RTX and FEC are used to
> >    protect media, and simulcast/layered coding can be used to provide
> >    support to heterogeneous receivers.  It needs to be possible to
> >    support these techniques, allow the recipient to optionally use or
> >    not use them on a source-by-source basis; and for simulcast/layered
> >    scenarios, to control which simulcast streams or layers are received.
> 
> I don't see anything in this section that conflicts with rtp-usage draft.
> 
> > Here is what Section 3.3 says:
> >
> > 3.3.  Handling of Simulcast, Forward Error Correction, and
> >       Retransmission Streams
> 
> ...
> 
> Again, that all seems reasonable, but doesn't address the issue of what
type
> of FEC to use. Like Magnus, I don't see working group consensus to
> recommend a particular FEC scheme. If you believe there is consensus on
> using a particular FEC scheme, make a proposal, and we'll incorporate it
if
> accepted.
> 
> --
> Colin Perkins
> http://csperkins.org/
> 
> 
> 
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