[Spce-user] Ringback

[Andreas Granig]

Hi John,

On 10/11/2012 12:48 AM, John Murray wrote:
> Can I maybe rewrite an incoming 183 from a PBX/Gateway and send a 180 to
> the PSTN when the call is initiated from the PSTN.
> 
> The problem I have is that the gateway is an MVNO mobile network and
> when the user is offline I get a ‘183 Session progress’ with media that
> says ‘The user is offline please try later’ twice and then a ‘480 temp
> unavailable’ at which point I can forward to voicemail or elsewhere.
> 
> Of course the caller has hung up by then on hearing the announcement. I
> would like to play ringing over that instead.
> 
>  
> 
> Can this be done? With Sems perhaps?

You can basically change the 183 to 180 in
/etc/ngcp-config/templates/ngcp.sbcprofile.conf.customtt.tt2 with a line
like this:

reply_translations="183=>180 Ringing"

But the peer will probably still send you early-media to the SDP infos
you provided it in the initial INVITE. Not sure if even stripping the
SDP in the 183/180 will help, as the peer already has all the relevant
infos where to send early media to, regardless of the reply the caller
gets back. Not sure if this would be valid in regards to RFC 3264
(offer/answer model using SDP) though.

Maybe you're lucky and the caller generates its own ringback and drops
arriving RTP packets if it gets a 180, but I won't count on that.

Andreas

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