Hi Pekka,
________________________________
From: Pekka Pessi <ppe...@gmail.com>
To: Arsen Chaloyan <achalo...@yahoo.com>
Cc: Jarod Neuner <j.neu...@networkharbor.com>; Boris Ouretskey
<borisu...@gmail.com>; "sofia-sip-devel@lists.sourceforge.net"
<sofia-sip-devel@lists.sourceforge.net>
Sent: Mon, January 10, 2011 2:05:03 PM
Subject: Re: [Sofia-sip-devel] Parsing OPTIONS SDP body
Hi Arsen,
2011/1/4 Arsen Chaloyan <achalo...@yahoo.com>
Let me clarify this a bit.
>
>The response to the SIP OPTIONS request does contain an SDP message and it's
>clear how it should be parsed in general. The question is how to retrieve the
>SDP message included in the response to the SIP OPTIONS request using nua API
>in
>particular.
>
>nua_options() is used to send requests, while nua_r_options is intended to be
>used to handle the responses. The nua documentation states
>http://sofia-sip.sourceforge.net/refdocs/nua/nua_8h.html#abca36033336ce16e538a279413d2ca51a379a42069d0268db014b5d3bb5d40112
>
>
>
>
>nua_r_options Answer to outgoing OPTIONS.
>Parameters:
>
> status response status code (if the request is retried the status is 100 and
>the sip->sip_status->st_status contain the real status code from the response
>message, e.g., 302, 401, or 407)
>
>
> phrase a short textual description of status code
>
> nh operation handle associated with the incoming OPTIONS request
>
> hmagic application context associated with the handle
>
> sip response to OPTIONS request or NULL upon an error (status code is in
>status and descriptive message in phrase parameters)
>
>
> tags empty
>See also:
>nua_options(), RFC 3261 section 11, nua_i_options
>All is good. However, as you can see, the tags are always empty and this is
>the
>problem. As a workaround, instead of nua, it's certainly possible to use nta
>directly...
>
> Sofia-SIP does not parse the body in the OPTIONS reply, because it is not
>supposed to change the session state. Instead you can find the SDP > payload
>in
>the sip->sip_payload field in nua_r_options event. Like Jarod said, you can
>parse the SDP in your application using the sdp module.
Well, I didn't notice before that the SDP message can be retrieved through the
sip->sip_payload field. This is exactly what we need.
> I'm just curious, what you plan to do with SDP returned by OPTIONS reply?
>Initiate re-INVITE if needed?
In the MRCPv2 specification, the SIP OPTIONS method is used for resource
discovery.
http://tools.ietf.org/html/draft-ietf-speechsc-mrcpv2-22#section-7
This way an MRCP client (SIP uac) can learn the capabilities of the MRCP
servers
(SIP uas) it's supposed to work with.
Thanks,
Arsen
www.unimrcp.org
--Pekka
--
Pekka.Pessi mail at nokia.com
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