Subject: [AVT] Re: I-D ACTION:draft-setsko-avt-ipmr-00.txt

From: Colin Perkins <[email-masked]>
Date: Sun, 30 Dec 2007 17:57:49 +0000

Andrey,

On 18 Dec 2007, at 20:15, [email-masked] wrote:
> A New Internet-Draft is available from the on-line Internet-Drafts
> directories.
>
> Title	: RTP Payload Format for SPIRIT IP-MR Speech Codec Software
> Author	: A. Setsko
> Filename: draft-setsko-avt-ipmr-00.txt
> Pages	: 14
> Date	: 2007-12-18
> 	
>   This document specifies the payload format for packetization of
>   SPIRIT IP-MR encoded speech signals into the Real-time Transport
>   Protocol (RTP). The payload format supports transmission of multiple
>   frames per payload, introduced redundancy for robustness against
>   packet loss, and payload format extension for future versions
>   compatibility.
>
> A URL for this Internet-Draft is:
> http://www.ietf.org/internet-drafts/draft-setsko-avt-ipmr-00.txt

This generally looks very reasonable, although I have a couple of  
comments:

The payload header includes two bits to signal if DTX is allowed and  
if byte aligned mode is used. There are also media type parameters  
defined to signal these features suitable for use with SDP  
signalling. It's not clear that both are useful - you might consider  
removing in-band signalling from the payload header, and relying  
solely on the SDP signalling.

Similarly, the payload header includes a bit (the "T bit") to  
indicate the presence of an extension to the payload header.  
Including extension headers in-band like this makes it difficult to  
negotiate their use: it's generally better to use different media  
subtype names for each variant, and hence use a different RTP payload  
type for each, since that allows negotiation for the extension.

Section 3 uses the old media type registration template, and should  
be updated to follow RFCs 4855 and 4288.

Regards,

-- 
Colin Perkins
http://csperkins.org/

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