Fax-enabled inbound route, long delay after call answered

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Fax-enabled inbound route, long delay after call answered

Postby eric_rkt » Wed May 22, 2013 12:25 pm

For an inbound route that has fax detect enabled, if a regular voice call comes in that goes to an automated attendant, it is picked up and then there is a long delay (equal to or greater than the configured fax detect time) before the automated attendant outbound announcement plays.

This can be a little annoying to callers, and the more impatient among them might think something is wrong and hang up (and maybe call again, maybe not).

It also makes it impossible to implement an automated attendant outgoing message that says something like "If you would like to send a fax, start it now. Otherwise, press 1 for John, 2 for Jane, 3 for Fred, or 0 for the receptionist.".

It would be better if Asterisk would detect a fax tone WHILE it is playing the outgoing message and not only BEFORE it starts playing the outgoing message.

I know this is possible, because fax+answering machines have worked that way for a decade or more.

The people intimately involved with Asterisk development... and with selling stuff for Asterisk... including the folks that wrote the Asterisk Definitive Guide, like to claim that there is virtually nothing that Asterisk can't do. So, this is something I would like Asterisk to do. Anyone have any idea how I would go about programming it to detect faxes while playing the OGM?
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Re: Fax-enabled inbound route, long delay after call answered

Postby david55 » Fri May 24, 2013 6:28 am

I don't think fax calling tone detection is part of FFA. Alternatively it only exists to confirm fax tone and force a fall back if not present.

As this is a feature request without a patch, the best place to make it would be the developer mailing list.

If implemented, this would almost certainly have to be in the form of a special application, like Background, which would have to run for at least the detection time. Detecting fax tone whilst letting the dialplan do arbitrary processing, including bridging, is likely to be a messy change.

Because fax calling tone is a single tone, it is more prone to talk off, so it is not something one would want enabled on the channel for longer than necessary.

Having said that, it looks to me that the the trunk build sip channel driver will force a Goto to the fax extension whenever it detect fax tone during a call, unless the current extension is already fax, or there is no fax extension in the current context, and always assuming fax detection is enabled.

It looks to me that chan_dahdi does something similar, but turns off fax tone detection after the first such detection.
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