[Freeswitch-users] codec and vad and cng configuration

[Mark D. Anderson]

> I added a new param to the sofia profile:
> 
> <param name="inbound-codec-negotiation" value="greedy"/>
> 
> This will do what you *expected*, (sorry for not meeting *all* your
> needs).

Thanks, that is cool.

Oh and by the way thanks again for mod_shout;
it worked perfectly the first time for me.

>> I see there is a "inbound-late-negotiation" param, but I don't
>>...

> This option prevents the codec negotiation from happening until the media
> is required.
> You can let calls hit the dialplan and examine the SDP with regular
> expressions
> and set an absolute codec string.  The point here is to make it possible
> to control
> the codec behaviour from the code.  Using this technique you can now set
> the 
> greedy behaviour as a channel variable in the dialplan.
> 
> Since you delayed negotation you had the oppurtunity to set the variable
> before the codec negotiation took place.
> 
> <action application="set" data="sip_codec_negotiation=greedy">
> <action application="answer"/>

Correct me if I'm wrong, but with inbound-late-negotiation set
to true, it would also be possible via dialplan xml logic or
more extended script logic, to consider the phase of the moon
and then do

  <action application="set" data="codec-prefs=GSM"/>

or 

  // or maybe not? channel vars aren't profile vars..
  session.setVariable("codec-prefs", "GSM")

where i pick just the one codec i want to use?

> We *always* advertise CNG and we *always* set the CNG mode in  the RTP if 
> someone we talk to supports it.  If they don't support it we turn it off.

oh, ok.
I was under the (apparently incorrect) impression that CNG was coupled
somehow to VAD, at least for some codecs.

> 
> When this takes place you will see a message in the DEBUG log about
> setting 
> the CNG payload type.  This means the RTP stack will send CNG frames
> whenever
> it notices an interval take place where no audio was sent.  The VAD param
> is the 
> way it is because we have not worked it into the SDP negotiation yet. 
> The in out
> or both is if you want to use this nonstandard VAD on the inbound media
> stream, the outbound
> streams or both.

My question about inbound VAD reflects what must be a basic
ignorance on my part about SIP -- I don't
understand what it would mean to turn it on or off -- the sender
will just do whatever it wants regardless, and the receiver has to cope,
right?

speaking of silence, is there any way in FS to make a channel be declared as
send-only (for example for an application that is just playing a file
and not doing anything with incoming voice).
[This is my own ignorance of SIP -- if it is one-way sending, can incoming 
rfc2833 dtmf tones still be sent in, to control the sending?]

> 
> A small TIP.   Going forward please take the time to read your email
> before you send it to
> make sure your wording or tone does not HIGHLY OFFEND the developers you
> are 
> asking for help.  YOU are asking ME to add functionality YOU want to MY
> software.
> 
> I am perfectly happy without this behaviour and I am adding it for YOU.
> I'll give you the benefit of the doubt if you did not realize the
> demanding tone
> of your email but please pay more attention to your manners in the
> future.

will do; sorry about any implication of a demand.
i only wanted to express confusion :)
i'm learning about SIP as i go along.

-mda