RE: [AVT] VoIP Shim for RTP Payload Formats

["Even, Roni" <roni.even at polycom.co.il>]

Hi,
I want to put my 2 cents on in band signaling.

I would agree that in-band signaling will work I point to point call.
Care should be taken for the following cases

1. Unidirectional media.
2. Multicast
3. Multipoint cases

That is why I think that capabilities should be in the signaling path
In the media path you can have changes which are of a temporary nature
like rate change commands for video or audio or indications.

I think you suggest a capability describing a more permanent state which
should be in SDP.

Roni Even    

> -----Original Message-----
> From: Desineni, Harikishan [mailto:hdesinen at qualcomm.com]
> Sent: Wednesday, September 06, 2006 10:57 PM
> To: Colin Perkins; Ingemar Johansson S ((LU/EAB))
> Cc: avt at ietf.org
> Subject: RE: [AVT] VoIP Shim for RTP Payload Formats
> 
> 
> I am under the impression that in-band signaling inside payload header
> is an accepted concept in this community. Other than AMR Payload
format,
> there is another payload format which is trying to use this concept.
> Once such work is the use of MBS field in Sec 5.2
> draft-ietf-avt-rtp-g729-scal-wb-ext-07.txt
> 
> "MBS (4 bits): maximum bit rate supported.  Indicates a maximum bit
>  rate to the encoder at the site of the receiver of this payload."
> 
> I think that RTCP (AVPF) has a similar message which can be used to
> convey maximum bit rate to the encoder at the remote end.
> 
> I'd like to infer the following statements from the reference to the
> above work in RTP and RTCP:
> 
> 1) In-band signaling using RTP payload header is an allowed/accepted
> concept.
> 2) RTCP signaling may also exist to carry the same information.
> 
> In certain scenarios (MOH, voice mail), RTCP signaling is unavoidable.
> One will end up defining methods to carry the same information using
> both in-band RTP and RTCP based feedback.
> 
> -----Original Message-----
> From: Colin Perkins [mailto:csp at csperkins.org]
> Sent: Friday, August 25, 2006 7:30 AM
> To: Ingemar Johansson S ((LU/EAB))
> Cc: avt at ietf.org
> Subject: Re: [AVT] VoIP Shim for RTP Payload Formats
> 
> > Inband signaling of the type proposed already exist for eg.
> > the AMR payload format (RFC3267), it is however limited to the
> > request of lower/higher codec rate. The intention of this added
> > inband signaling is to allow for requests regarding frame
aggregation
> > and redundancy during a session so in that aspect it is a
> > continuation of the inband signaling concept that already exist.
> 
> This is one of the less desirable features of the AMR payload format,
> and was included solely for backwards compatibility.
> 
> 
> Colin
> 
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