thank you very much Tamas,
i found this infos very useful :)

-----Ursprüngliche Nachricht-----
Von: freeswitch-users-bounces@lists.freeswitch.org [mailto:freeswitch-users-bounces@lists.freeswitch.org] Im Auftrag von Tamas
Gesendet: Samstag, 13. September 2008 14:31
An: freeswitch-users@lists.freeswitch.org
Betreff: Re: [Freeswitch-users] VAD and CN question


Hello,

to answer for my own email - for other who might be interested...


Tamas írta:

Hello,

I've talked about CNG, VAD with Anthony and Brian already but I still

have a mess in it and don't really know how it works.

Could anybody explain the practical side of these magic options?

1. What does suppress_cng=true do exactly? (yep, I know it suppresses

CNG, but what does this mean? Won't send out the CN/8000 rtpmap in SDP?)

suppress-cng and suppress_cng are used to manage the sending of CN RTP
packets after agreement through SDP.

2. What do VAD settings do in sofia profile? I've read

http://wiki.freeswitch.org/wiki/Sofia.conf.xml

  <!-- <param name="vad" value="in"/> -->

  <!-- <param name="vad" value="out"/> -->

  <!-- <param name="vad" value="both"/> -->

What do these options do in practice? Can FS detect silence (e.g. no

RTP?) and than what can it do with?

When VAD is turnd on, FS checks on the given channel for incoming or/and
outgoing channel (depends on the settings) and when detects silence,
stops sending out RTP.

3. I found undocumented options rtp_enable_vad_in, rtp_enable_vad_out

for sofia which might be the per call settings for point 2. ? If this is

correct, what will this do?

           <action application="set" data="rtp_enable_vad_in=true"/>

           <action application="set" data="rtp_enable_vad_out=true"/>

          <action application="bridge" data="sofia/....."/>

These settings are the same as in 1. but can be used per call.

4. What will FS do when one side of the bridge supports CN but the other

doesn't?

E.g. softphone->FS->GW (sends CN packets)

the softphone does not support CN

Would it be possible to turn on comfort noise generation in FS for the

side which cannot handle CN?

When on side does not support CN, FS simply won't forward CN RTP
packets. Comfort noise generation into media channel in FS is possible with
bridge_generate_comfort_noise=true
added in r9543. More about on http://wiki.freeswitch.org/wiki/VAD_and_CNG

5. Is it possible to let FS detect silence and on one leg send CN

packets insted of RTP?

E.g. softphone->FS->GW (sends  CN packets)

the softphone does not support CN, but for saving bandwidth it would be

good to have silence detection and in case of silence FS lets send CN

instead of RTP.

Yes, possible. VAD has to be turned on that channel and both sides have
to agree on CN RTP packets (in SDP).

Sorry for my dump questions, I would like to understand the whole picture.

I hope I'm on the right way :)

I would like to add the clarification to FS wiki to lets other have less

troubles (with endpoints on one side supporting VAD/CNG and endpoints on

other side not supporting VAD/CNG, e.g. CallWeaver)

Check
http://wiki.freeswitch.org/wiki/VAD_and_CNG

Thanks in advance!

Regards,

   Tamas