Subject: RE: [AVT] RFC2833 Question

From: "O'Connor, Kevin" <[email-masked]>
Date: Tue, 13 Jun 2006 14:34:40 -0400

Is this possible with any 'audio'? For example, if an RTP session is
negotiated to allow G.711 and G.729, should the receiver be able to
handle receiving both G.729 and G.711 packets for the same timestamp
range?

-----Original Message-----
From: Tom-PT Taylor [mailto:[email-masked]] 
Sent: Tuesday, June 13, 2006 1:36 PM
To: O'Connor, Kevin
Cc: [email-masked]
Subject: Re: [AVT] RFC2833 Question

You can have two packets in the same stream representing the same 
timestamp range. Because the media type for RFC 2833 events is 'audio', 
it can be offered in the same stream as your G.711 example. You need a 
policy at the receiving gateway to decide which payload type to use, 
bearing in mind the need for a clean transition between tones and other 
content.

O'Connor, Kevin wrote:
> Is it possible to have two RTP packets in the same stream that
> represent the same timestamp range? For example, the audio
> representation of a tone event as G.711 as well as the
> telephone-event representation. Another example would be the
> telephone-event and the tone as two different packets.
> 
> 
> 
> Or, is this only possible via an explicit redundancy mechanism such
> as RFC 2198?
> 
> 
> 
> 
>
------------------------------------------------------------------------
> 
> 
> _______________________________________________ Audio/Video Transport
> Working Group [email-masked] https://www1.ietf.org/mailman/listinfo/avt

_______________________________________________
Audio/Video Transport Working Group
[email-masked]
https://www1.ietf.org/mailman/listinfo/avt

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From: "Tom-PT Taylor" <[email-masked]>
Date: Tue, 13 Jun 2006 15:53:28 -0400

Yes, it is possible. I could see it happening in a transition to and 
from voiceband data. I'm not sure if it would really happen in practice.

---

From: Randell Jesup <[email-masked]>
Date: Tue, 13 Jun 2006 16:39:21 -0400

>handle receiving both G.729 and G.711 packets for the same timestamp

In theory, yes, you have to "handle" it.  What you do with them: undefined
so far as I know.  In theory, if you have two codecs agreed to in the SDP,
you could have every other packet be a different codec. And they could
overlap, timestamp-wise.  The timestamp for packet N+1 could even be
earlier than the timestamp for packet N (and this does happen for some
video codecs, even for the same payload/codec).

-- 
Randell Jesup, Worldgate (developers of the Ojo videophone), ex-Amiga OS team
[email-masked]

---

From: Colin Perkins <[email-masked]>
Date: Wed, 14 Jun 2006 16:38:18 +0100

On 13 Jun 2006, at 21:39, Randell Jesup wrote:
> so far as I know.

Mixing them together and playing out the result would probably be a  
reasonable approach, although I don't know if that's formally  
specified anywhere.

> In theory, if you have two codecs agreed to in the SDP,

Right.

Colin