[Standards-JIG] XEP-0167: Jingle audio payload extensions

Peter Saint-Andre stpeter at jabber.org
Mon Oct 30 22:30:54 UTC 2006


Sean Egan wrote:
> On 10/30/06, Peter Saint-Andre <stpeter at jabber.org> wrote:
>> For example, as described in draft-ietf-avt-rtp-speex, the "ptime",
>> "sr", "ebw", "vbr", "eng", and "mode" parameters may be specified in
>> relation to usage of the Speex codec. In SDP these parameters are
>> represented in the "fmtp" line. I think that in Jingle we would
>> represent these in XML, such as:
> 
> A few of us here at Google discussed this exact issue last week. Our
> consensus was that codecs specified on the fmtp line should be
> specified more like:
> 
> <payload-type id='96' name='speex' clockrate='16000'>
>  <parameter name='vbr' value='on'/>
>  <parameter name='cmg' value='on'/>
> </payload-type>
> 
> This allows you to negotiate codec parameters and easily translate
> them to SDP without maintaining and understanding a vast namespace
> registry of every possible codec.

True. And that approach will work because parameter names are guaranteed
to be unique:

http://www.iana.org/assignments/sdp-parameters

> Non-codec-specific attributes (those defined in the SDP RFC itself)
> should be attributes of the <payload-type/> element. 

Agreed.

> So you'd have:
> 
> <payload-type id='96' name='speex' clockrate='16000' ptime='30' >
>  <parameter name='vbr' value='on'/>
>  <parameter name='cmg' value='on'/>
> </payload-type>

Right. I'll fix up the spec accordingly.

Peter

-- 
Peter Saint-Andre
Jabber Software Foundation
http://www.jabber.org/people/stpeter.shtml

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