[Asterisk-Users] Sangoma A200 preventing Zap channels from disconnecting immediately after PSTN line hangs up (getting empty voicemails)

[Mike Garey]

On 4/26/06, John Novack <jnovack at stromberg-carlson.org> wrote:
>
>
> Mike Garey wrote:
>
> > <snip>
> >
> >>
> >>; How many seconds of silence before we end the recording
> >>maxsilence=10
> >>; Silence threshold (what we consider silence, the lower, the more sensitive)
> >>silencethreshold=128
> >>
> >>
> >
> >the maxsilence setting doesn't really help, as I believe that only
> >limits how long we record for after voicemail has already started and silence is detected.  I don't want voicemail to record anything at all if the call has been disconnected before the voicemail prompt starts.
> >
> >
> Makes good sense.
> If there is no speech, but simply x seconds of silence, the VM messges
> should  not even exist

ideally there should be a setting to simply remove a voicemail message
that contains nothing but silence, but that's not what the maxsilence
setting is for.  Once you start recording a voicemail message, if you
stop talking, a timer begins counting.  If you don't speak for
maxsilence seconds, you get disconnected.

It is, however, possible to use maxsilence in conjunction with the
minmessage setting to prevent empty voicemails from being left, by
simply setting minmessage to be 1 second longer than the maxsilence
setting.  So if someone hangs up before leaving a voicemail message,
but the system doesn't disconnect them immediately, the system stops
the recording after maxsilence (ie 3 seconds), but if you have
minmessage set to 4, asterisk will abandon the message.  The problem
is, if someone calls and then maybe gets sidetracked, or has to speak
to someone else for a few seconds, or pick up their cell phone, in the
middle of leaving a message, they'll get disconnected.  So this still
isn't a solution.

The only thing I can think of is to run a script (specified by
externnotify) after a voicemail message is left, which runs some type
of audio analysis process to determine whether the sound file actually
contains anything, and if not, delete it.  I'm not sure what tool I
can use to do the silence detection (I checked the manpage for sox,
but it seems to only be able to remove silence from the beginning/end
of a file, not report whether a file has silence or not).

Mike


> >What I don't understand is that this works fine on many regular
> >telephone answering machines, which are _much_ less advanced than
> >asterisk. If they can do it, why can't asterisk?
> >
> It certainly could, if someone were smart enough and willing to code it.
> There generally seems more interest in adding new wiz bang features
> rather than polish up what is already mostly working.
>
> > I mean, if I call my home line and wait for the answering machine message to kick in, then hangup right before it starts recording, I don't end up with an empty message, the system just disconnects me.
> >
> >
> >
> Many machines work this way even after they start recording, but there
> is nothing but silence. Returned dial tone and line noise cause this to
> fail, however.
>
> jOHN nOVACK
>
> >
> >
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