[asterisk-users] Ringing (180) no SDP to progress(183) with SDP transition => no audio.

[Richard Mudgett]

On Mon, Nov 20, 2017 at 7:31 AM, Benoit Panizzon <benoit.panizzon at imp.ch>
wrote:

> Dear List
>
> I am testing various early audio scenarios with different voice IC's,
> phones and pbxes.
>
> In Switzerland, when you operate a value added number, you have to
> announce the price of the call, usually in early audio, before the call
> is established.
>
> In 'dialplan' terms this would be:
>
> exten => XX,1,Ringing
> exten => XX,n,Wait(15)
> exten => XX,n,Progress
> exten => XX,n,Playback(price-announce,noanswer)
> exten => XX,n,Wait(5)
> exten => XX,n,Answer
>
> I see the asterisk playing the early announcement audio in the rtp
> stream. Some devices (arris EMTA) calling the asterisk also do play it
> to the caller.
>
> But!
>
> Most other devices I have tested just keep playing the locally generated
> ringtone despite getting an 183 with SDP and the announcement is never
> to be heard by the caller.
>
> If I do to force inband ringback tone, this works with all devices I
> have tested so far.
>
> exten => XX,1,Progress
> exten => XX,n,Ringing
> exten => XX,n,Wait(15)
> exten => XX,n,Playback(price-announce,noanswer)
> exten => XX,n,Wait(5)
> exten => XX,n,Answer
>
> Is anything wrong with the transition of ringing without SDP (to have
> the local device generating ringback tone) and then start sending early
> audio with 183?
>

Both orderings of Ringing and Progress are valid.  It is up to the calling
device to handle it.  As you have seen, there is quite a difference in
how devices handle it.  I have even seen where the calling device needs
Ringing before Progress to handle the call correctly.  I think that case was
because the device was converting ISDN to SIP.  I do think that the devices
that don't stop local ringback in favor of the incoming RTP stream following
the 183 are broken.  Unfortunately it is something that is out of your
control.

Richard
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