Subject: [SIP] Changing Codec

From: "Mo Zonoun" <[email-masked]>
Date: Tue, 21 Nov 2000 12:47:15 -0600

How do you change codec in a SIP call without disconnecting the established
call?

Mo Zonoun

---

From: "Bratakos, Maroula" <[email-masked]>
Date: Wed, 22 Nov 2000 07:50:45 -0800

Actually, I think it is better for the side that issued the re-INVITE to
make the decision about whether to return to the original media or tear down
the call.  If the decision is to return to the original media then no more
SIP messages are required since the other side already rejected the new
media.  If the decision is to terminate the call because the original media
can no longer be supported then a BYE can be issued.

-Maroula Bratakos

-----Original Message-----
From: Billy Biggs [mailto:[email-masked]]
Sent: Wednesday, November 22, 2000 7:33 AM
To: Venkatesh Venkataramanan
Cc: [email-masked]; Pascal Doré; Mo Zonoun
Subject: Re: [SIP] Changing Codec

Venkatesh Venkataramanan ([email-masked]):

> >   And the far end is sending you codec 1, but you only want to receive
> > codec 0, then you can always re-INVITE with:
> >
> >    m=audio 8552 RTP/AVP 0
> >
> >   And force it to use either codec 0 or nothing.  Be prepared though
> > that if the remote end can't send codec 0, it might tear down the call
> > (or at best audio won't flow).

>  But if this (re)INVITE fails, shouldn't the original media agreed
>  upon prevail ? That's how I understand (re)INVITES(unlike what you
>  mention about the remote UA tearing down the call). Please clarify.

  I think this was the intention of some folks on this list- that a
rejected re-INVITE means the old session stays up.

  However, I would be more inclined to accept the re-INVITE and shut
down the call.  The SDP was not malformed, and the remote side has
clearly changed its session and is now listening for a different codec.

  I don't have any implementation experience with multiple codecs
though (not with kphone).

-- 
Billy Biggs, 3Com               Email: [email-masked]
http://www.div8.net/billy/      Phone: [email-masked]

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---

From: Jonathan Rosenberg <[email-masked]>
Date: Wed, 22 Nov 2000 17:00:30 -0500

Either way is fine. Its a matter of local choice. I don't think the spec
needs to say anything except that a rejection of a reinvite returns to the
previous session state.

-Jonathan R.

---
Jonathan D. Rosenberg                       72 Eagle Rock Ave.
Chief Scientist                             First Floor
dynamicsoft                                 East Hanover, NJ 07936
[email-masked]                     FAX:   (973) 952-5050
http://www.cs.columbia.edu/~jdrosen         PHONE: (973) 952-5000
http://www.dynamicsoft.com

> From: Bratakos, Maroula [mailto:[email-masked]]
> Sent: Wednesday, November 22, 2000 10:51 AM
> To: 'Billy Biggs'; Venkatesh Venkataramanan
> Subject: RE: [SIP] Changing Codec
> 
>