[Freeswitch-users] absolute_codec_string and bypass_media

Sergey Okhapkin sos at sokhapkin.dyndns.org
Tue Jul 27 09:04:05 PDT 2010


Yup, it's pretty easy to build modified (shortened/reordered) 
absolute_codec_string variable from ep_codec_string, rather than mess with 
switch_r_sdp variable.

On Tuesday 27 July 2010, Kristian Kielhofner wrote:
> Exactly.  What about these cases where you're removing a codec from
> the offer and/or changing the order?
> 
> FreeSWITCH currently allows you to do this by mangling the SDP and so
> do others (OpenSIPS txtops, etc).
> 
> On Tue, Jul 27, 2010 at 11:37 AM, Sergey Okhapkin
> 
> <sos at sokhapkin.dyndns.org> wrote:
> > In my application I need 2 kinds of SDP manipulation in bypass media mode
> > and late negotiation turned on:
> >
> > 1) Do not send out no-sense for PSTN codecs on leg B like wideband
> > codecs, ilbc or speex. I need to filter out all codecs except for PCMU,
> > PCMA,G729 and GSM.
> >
> > 2) Change codec order on B-leg, some PSTN carriers (like icall) behave
> > wildly if G729 is first codec, I need to change A-leg codec order "18 0"
> > to "0 18".
> >
> > On Tuesday 27 July 2010, Anthony Minessale wrote:
> >> You really never should be messing with the sdp because you can cause a
> >> violation in the SOA policy.
> >> The negotiation is between the 2 endpoints so if you modify A's sdp it
> >>  could confuse it when you reply back with B's sdp which was created
> >> under false pretenses.
> 




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