[Freeswitch-dev] Strange behaviour in SOFIA SIP

[Anthony Minessale]

that's what I was trying to explain.
PROXY mode does not let you manipulate anything, it's pure
pass-through negotiation between the endpoints.

All the stuff with ep_codec_string are relevant only when you are not
trying to use proxy mode.
This is a common mistake people make assuming not using proxy mode
means somehow doing more work but it's not the case, any time both
legs of a call use the same codec it's equally efficient to what you
end up with in proxy mode.  proxy mode simply means take the inbound
SDP and offer it AS IS to the far end and vice-versa and use a fake
codec in the middle that is agnostic.



On Fri, Oct 21, 2011 at 10:36 AM, Visciano Giovanni
<Giovanni.Visciano at italtel.it> wrote:
> 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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-- 
Anthony Minessale II

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