[Freeswitch-users] codec and vad and cng configuration

Sat Jun 9 19:48:05 PDT 2007

----- Original Message ----
From: Mark D. Anderson <mda at discerning.com>
To: freeswitch-users at lists.freeswitch.org
Sent: Saturday, June 9, 2007 1:18:09 PM
Subject: [Freeswitch-users] codec and vad and cng configuration

It seems FS will simply go through the rtpmap offers in an incoming INVITE,
in the incoming order, and pick the first one that is in the codec-prefs
in my sofia.conf.xml (see end of this message for trace).

But I was expecting that FS (or sofia underneath) would instead negotiate
by checking codecs in my configured list, and pick the first matching one
in *my* list, not the first matching one in *their* list.

---------------------------------------------------------------------------------------------------------------
That is correct.  This was done intentionally.  Since you asked *sooo* nicely

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).

---------------------------------------------------------------------------------------------------------------

I see there is a "inbound-late-negotiation" param, but I don't
know how this would be used -- nor do I think i'd want to use
it, if the priority can just be taken from my list.

---------------------------------------------------------------------------------------------------------------

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"/>

---------------------------------------------------------------------------------------------------------------

Regarding VAD, I'm wondering why there is an "in" or "both" setting --
isn't VAD chosen by the sender?
Also, it seems kind of limiting to have to enable VAD regardless
of who is connecting (what UA) and regardless of what codec is in
use. 
And I see no way to control CNG at all?

---------------------------------------------------------------------------------------------------------------

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.

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.

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.

---------------------------------------------------------------------------------------------------------------

-mda

example trace, showing how it picks PCMU since it is first in their list,
when the first match in my list would have been iLBC

----

2007-06-09 13:03:43 [DEBUG] sofia.c:1028 sofia_handle_sip_i_state() Remote SDP:
v=0
o=root 12720 12720 IN IP4 67.55.159.156
s=session
c=IN IP4 67.55.159.156
t=0 0
m=audio 12104 RTP/AVP 0 8 3 111 5 10 7 97 18 101
a=rtpmap:0 PCMU/8000
a=rtpmap:8 PCMA/8000
a=rtpmap:3 GSM/8000
a=rtpmap:111 G726-32/8000
a=rtpmap:5 DVI4/8000
a=rtpmap:10 L16/8000
a=rtpmap:7 LPC/8000
a=rtpmap:97 iLBC/8000
a=rtpmap:18 G729/8000
a=fmtp:18 annexb=no
a=rtpmap:101 telephone-event/8000
a=fmtp:101 0-16
a=silenceSupp:off - - - -

2007-06-09 13:03:43 [DEBUG] sofia_glue.c:1157 sofia_glue_negotiate_sdp() Audio Codec Compare [PCMU:0:8000]/[speex:98:8000]
2007-06-09 13:03:43 [DEBUG] sofia_glue.c:1157 sofia_glue_negotiate_sdp() Audio Codec Compare [PCMU:0:8000]/[iLBC:97:8000]
2007-06-09 13:03:43 [DEBUG] sofia_glue.c:1157 sofia_glue_negotiate_sdp() Audio Codec Compare [PCMU:0:8000]/[GSM:3:8000]
2007-06-09 13:03:43 [DEBUG] sofia_glue.c:1157 sofia_glue_negotiate_sdp() Audio Codec Compare [PCMU:0:8000]/[PCMA:8:8000]
2007-06-09 13:03:43 [DEBUG] sofia_glue.c:1157 sofia_glue_negotiate_sdp() Audio Codec Compare [PCMU:0:8000]/[PCMU:0:8000]
2007-06-09 13:03:43 [DEBUG] sofia_glue.c:817 sofia_glue_tech_set_codec() Set Codec sofia/profile1/8572337508 at 67.55.159.156:5060 PCMU/8000 20 ms

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