[Freeswitch-dev] Strange behaviour in SOFIA SIP

Visciano Giovanni Giovanni.Visciano at italtel.it
Fri Oct 21 19:36:11 MSD 2011


Hello Anthony.
Maybe I want not so clear, let me explain.

I do not want to apply any codec manipulation, I'm working on a prototype endpoint module that has "proxy media capabilty" and wants to interoperate with other endpoints.
What I saw is that in a sofia vs sofia call (proxy mode+late negotiation) they exchange through FS calling/called endpoint capability looking at SDP session carried by channel variables, so internally they use SDP O/A scheme.
I thought that "ep_codec_string"->SWITCH_ORIGINATOR_CODEC_VARIABLE could be used to exchange capability without using a protocol specific format (SDP).
If this is not the case, what's the right way to negotiate capability between endpoints in proxy mode?

Than you.
Giovanni

PS: I did not find any existing endpoint except sofia that support this. Am I right?

-----Original Message-----
From: freeswitch-dev-bounces at lists.freeswitch.org on behalf of Anthony Minessale
Sent: Fri 10/21/2011 5:06 PM
To: freeswitch-dev at lists.freeswitch.org
Subject: Re: [Freeswitch-dev] Strange behaviour in SOFIA SIP
 
any codec manipulation techniques and proxy media mode are not
compatible.  Proxy media mode means stay completely out of the codec
negotiation process.

On Thu, Oct 20, 2011 at 3:11 PM, Visciano Giovanni
<Giovanni.Visciano at italtel.it> wrote:
> Preconditions on sip profile
> ----------------------------
> inbound-codec-prefs NOT set
> outbound-codec-prefs NOT set
> inbound-proxy-media=TRUE
> inbound-bypass-media=FALSE
> inbound-late-negotiation=TRUE + inherit_codec=TRUE
>
> TEST scenario
> -------------
> SIP phone send INVITE with SDP to FS
>
> INVITE
> SDP[codelist=PCMA, PCMU, G722, G729] --> FS
>
> FS has just the CORE_PC_MODULE [PCMA, PCMU, PASS-THR, VIDEO-PASS-THR, L16]
>
> The "ep_codec_string" channel variable is loaded with [PCMA, PCMU]
>
> EXPECTED
> --------
> In "proxy-media + late-negotiation" scenario:
> ep_codec_string=[PCMA,PCMU,G722,G729]
>
> PROBLEM
> -------
> According to the documentation
> (http://wiki.freeswitch.org/wiki/Codec_negotiation):
>
> "ep_codec_string: This variable is only available if late negotiation is
> enabled on the profile. It's a readable string containing all the codecs
> proposed by the calling endpoint."
> and
> "inherit_codec=true (only applicable when late-negotiation is enabled) will
> take the codec negotiated when the B leg answers and pass it to the A leg so
> it also uses the same codec (if the A leg supports it); otherwise, it will
> use whatever it can from its own list"
>
> The variable ep_codec_string doesn't contain ALL the codecs proposed by the
> calling endpoint. It contains the intersection between the codecs proposed
> by the calling and the codecs loaded in FS.
> In proxy-media / no-media configuration the called endpoint doesn't have the
> calling codec list so he can't negotiate using all the capabilities
> available.
> (I'm working on a test endpoint module that should work in proxy and
> no-media configuration ... mod_sofia vs mod_sofia works because they look at
> the remote sdp variable)
>
> Source reference - sofia_glue.c->sofia_glue_set_r_sdp_codec_string()
>
>
> Regards,
> Giovanni
>
>
>
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-- 
Anthony Minessale II

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