[asterisk-users] How to tune Asterisk AMD - Answering Machine Detection "hacks"

[Matt Riddell]

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Costa Dinoteli wrote:
> Hello Everyone,
> 
> Can someone point me to reliable links on how to tweak Asterisk AMD
> I am calling a number and have to two files to play depending if it is a
> real person or an
> answering machine.
> Most everytime Asterisk calls  it thinks it is an Answering Machine and it
> starts playing
> the AMD message, instead of the delivering the "1st real message"

Heh, two critical things that affect it:

1) The threshold - just play with this till its right - bear in mind
that calls to cellphones may need a higher threshold as the noise is
often read as talking.

2) Call setup time once answered.  This is a really easy one to prove
and has had me pulling my hair out (what's left) on a few occasions.

Basically do the following:

exten => s,1,Answer()
exten => s,n,Background(beep)
exten => s,n,AMD()

What this will do is that when the call is bridged to the remote end
(i.e. someone answered the phone) you will hear a beep once Asterisk has
answered the channel.

Bear in mind that most people will say hello pretty quickly after
answering the phone.

Make a call to yourself (send one end to you and the other end to the
above snippet) and try to respond in a way that you think a normal user
would.

If you say hello before you hear the beep then there is no way that AMD
is going to be able to hear it, and you will fall into the
initial_silence territory.  I.E. The AMD will think that it is a machine
because it missed the initial hello and then the person was silent.

You may find that this bridging time varies between providers (and most
people using AMD are also trying to use the cheapest providers).

I have a system with 3000 concurrent lines running which now has no
problems, but required a direct connection to Qwest.

- --
Kind Regards,

Matt Riddell
Director
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