[Freeswitch-users] Codec negotiation questions

Anthony Minessale anthony.minessale at gmail.com
Fri Feb 13 07:46:15 PST 2009 

yes you are wrong.

inbound-late-negotiation setting delays the codec negotiation until the
instant audio is needed.
It is not tied to inbound-proxy-media.


This allows the call to come into the dialplan before any codec negotiation
is done giving you a chance to look at the SDP before the negotiation takes
place and insert an absolute_codec string essentially letting you chose
unique codec preferences per inbound call.

>>> Why I should parse variable_switch_r_sdp

Well....you must parse it because it's you who cares about what it says, as
described above it lets you peek at the sdp and enforce a unique set of
codec prefs per call.



On Fri, Feb 13, 2009 at 8:57 AM, ivdreg ivdreg <ivdreg at gmail.com> wrote:

> Hi Anthony,
>
> Excuse me if I'm wrong but inbound-late-negotiation must be used
> proxy_media as I see in documentation. I don't want to proxy media because
> of some issues with MOH or 3-way conferencing. Also I want to exclude media
> codecs that are supported only in pass-trough mode. Let mi give you an
> example:
>
> SDP from caller
>
>    v=0
>    o=- 1 2 IN IP4 192.168.20.193
>    s=CounterPath eyeBeam 1.5
>    c=IN IP4 192.168.40.81
>    t=0 0
>    m=audio 56888 RTP/AVP 100 106 97 105 98 3 101
>    a=fmtp:101 0-15
>    a=rtpmap:100 SPEEX/16000
>    a=rtpmap:106 SPEEX-FEC/16000
>    a=rtpmap:97 SPEEX/8000
>    a=rtpmap:105 SPEEX-FEC/8000
>    a=rtpmap:98 iLBC/8000
>    a=rtpmap:101 telephone-event/8000
>    a=sendrecv
>    a=x-rtp-session-id:61940567309B49E8909127E1393A966E
>    m=video 46378 RTP/AVP 125 115 34
>    a=fmtp:125 profile-level-id=42e015; max-br=4000; max-mbps=19800
>    a=fmtp:115 QCIF=1 MAXBR=4520
>    a=fmtp:34 QCIF=1 MAXBR=4520
>    a=rtpmap:125 H264/90000
>    a=rtpmap:115 H263-1998/90000
>    a=rtpmap:34 H263/90000
>    a=sendrecv
>    a=x-rtp-session-id:E8244E608F65445BA183BBE641C5DF3C
>    a=nortpproxy:yes
>
> SDP from Freeswitch to called
>
>    v=0
>    o=FreeSWITCH 6228154995644782318 4633980766357417433 IN IP4 10.10.10.10
>    s=FreeSWITCH
>    c=IN IP4 10.10.10.10
>    t=0 0
>    m=audio 26920 RTP/AVP 3 101 13
> *   a=rtpmap:3 GSM/8000*
>    a=rtpmap:101 telephone-event/8000
>    a=fmtp:101 0-16
>    a=rtpmap:13 CN/8000
>    a=ptime:20
>
> So we offer *only first* in codec preference list
>
> from called wich is normal receives
>    SIP/2.0 488 Not Acceptable Here
> *called suports - PCMA,PCMU,iLBC
> *
> Codec preference to this vars.xml we have witch is used in provile:
> <X-PRE-PROCESS cmd="set" data="all_codec_prefs=GSM,speex at 32000h
> @20i,speex at 16000h@20i,speex at 8000h@20i,*iLBC at 30i,PCMA,PCMU*,G729"/>
> also we have in profile:
> <param name="inbound-codec-negotiation" value="greedy"/>
> <param name="disable-transcoding" value="true"/>
> In dialplan I've set:
> <action application="set" data="inbound-late-negotiation"/>
> <action application="set" data="inherit_codec=true"/>
>
> About my second question:
> Why I should parse variable_switch_r_sdp: [v=0
> o=- 6 2 IN IP4 192.168.20.193
> s=CounterPath eyeBeam 1.5
> c=IN IP4 192.168.40.81
> t=0 0
> m=audio 60642 RTP/AVP 100 106 97 105 98 3 101
> a=rtpmap:100 SPEEX/16000
> a=rtpmap:106 SPEEX-FEC/16000
> a=rtpmap:97 SPEEX/8000
> a=rtpmap:105 SPEEX-FEC/8000
> a=rtpmap:98 iLBC/8000
> a=rtpmap:101 telephone-event/8000
> a=fmtp:101 0-15
> a=x-rtp-session-id:0674790128EB43ACB8C7F55829BCFF14
> m=video 44938 RTP/AVP 125 115 34
> a=rtpmap:125 H264/90000
> a=fmtp:125 profile-level-id=42e015; max-br=4000; max-mbps=19800
> a=rtpmap:115 H263-1998/90000
> a=fmtp:115 QCIF=1 MAXBR=4520
> a=rtpmap:34 H263/90000
> a=fmtp:34 QCIF=1 MAXBR=4520
> a=x-rtp-session-id:D1EAE543055746AC9C03006B91ADE6DF
> a=nortpproxy:yes
> ]
> In FS core this parse is already done I'm sure in much more intelligent
> way. It can be exported as a variable like a absolute codec string I think.
>
> Thanks again.
>
> 2009/2/12 Anthony Minessale <anthony.minessale at gmail.com>
>
> the entire sdp is available as a variable (route the call to the info app
>> to see the variables)
>> so if you have inbound-late-negotiation set to true on the sip profile
>> then you can use a regex or a script to set absolute_codec string before
>> you answer.
>>
>>
>> On Thu, Feb 12, 2009 at 8:06 AM, ivdreg ivdreg <ivdreg at gmail.com> wrote:
>>
>>> Hi all,
>>>
>>> Can I ask 2 questions about codec negotiation:
>>>
>>> 1. Is it possible Freeswitch to work negotiate codecs between two phones
>>> as it is described below.
>>> INVITE from A with some codecs in SDP ---> Freeswitch rewrites codec
>>> preference according absolute_codec_string but exclude all codecs not
>>> offered by A ----> INVITE to B with rewrited SDP.
>>>
>>> example:
>>> from A SDP:PCMA,PCMU,SPEEX  ----> absolute_codec_string=G722,PCMU,PCMA,GSM
>>> ----> to B SDP: PCMU,PCMA
>>>
>>> 2. Can I get codec list in INVITE with mod_perl for example or via
>>> xml_curl without processing SDP variable (switch_r_sdp). It will be useful
>>> to be in format that absolute_codec_string variable takes.
>>>
>>> Thanks
>>>
>>> _______________________________________________
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>>> Freeswitch-users at lists.freeswitch.org
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>>>
>>>
>>
>>
>> --
>> Anthony Minessale II
>>
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>>
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>>
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>>
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>
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>


-- 
Anthony Minessale II

FreeSWITCH http://www.freeswitch.org/
ClueCon http://www.cluecon.com/

AIM: anthm
MSN:anthony_minessale at hotmail.com <MSN%3Aanthony_minessale at hotmail.com>
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