Re: [AVT] draft-ietf-avt-rtp-speex-02.txt

[Colin Perkins <csp at csperkins.org>]

On 19 Jun 2007, at 10:51, Colin Perkins wrote:
> On 19 Jun 2007, at 10:15, Aymeric Moizard wrote:
> > There is an issue with section:
> > "	4.1.1. Registration of media type audio/speex"
> >
> > First, the mode parameter text is defined using the same text as  
> > for the SDP usage text: It sounds clear to me that in case "mode"  
> > is used as a
> > media parameter, it cannot be possible to specify several "mode".
> >
> > Although, I don't know much about media type.
> >
> > Thus, I think we have to keep the definition of mode in the SDP
> > usage section.
>
> There shouldn't be any parameter definitions in the SDP usage  
> section. That section is only used to specify how the media type  
> parameters are represented in SDP.

Having now had time to read the draft in detail, what's needed is  
something like:

   The information carried in the media type specification has a
   specific mapping to fields in the Session Description Protocol (SDP)
   [5], which is commonly used to describe RTP sessions.  When SDP is
   used to specify sessions employing the Speex codec, the mapping is
   as follows:

   o  The media type ("audio") goes in SDP "m=" as the media name.

   o  The media subtype ("speex") goes in SDP "a=rtpmap" as the  
encoding
      name. The required parameter "rate" also goes in "a=rtpmap" as  
the
      clock rate.

   o  The parameters "ptime" and "maxptime" go in the SDP "a=ptime" and
      "a=maxptime" attributes, respectively.

   o  Any remaining parameters go in the SDP "a=fmtp" attribute by
      copying them directly from the media type string as a semicolon
      separated list of parameter=value pairs.

   Some example SDP session descriptions utilizing Speex encodings
   follow.

To replace much of the existing text in the first half of Section 5.  
The rationale is that all parameters are defined as parameters of the  
media type, and the SDP usage just describes how those media type  
parameters are encoded into SDP.

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



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