[Freeswitch-users] VAD and CN question

[Tamas]

Hello,

Thanks for guys on IRC channel, now things around VAD/CNG are more clear
for me.

I've started a wiki documentation about the topic as there is no such
page yet and I hope it will be a good startup:
http://wiki.freeswitch.org/wiki/VAD_and_CNG

I'm aware of that some parts might be inaccurate and even wrong, so bear
with me, I just took the time to start document this part.

I would like to ask the gurus (anthm, bkw, coppice, etc.) to review the
page and correct my mistakes.

Thanks!

Regards,
    Tamas

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?)
>
> 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?
>
> 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/....."/>
>
> 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?
>
> 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.
>
> Sorry for my dump questions, I would like to understand the whole picture.
>
> 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)
>
> Thanks in advance!
>
> Regards,
>     Tamas
>