asterisk users - Aug 2013 - How to play audio to callee when a fax is detected ?

Hello,

Let say Alice and Bob both have a sip phone connected to the same asterisk
11 box.
Alice has T.38 enabled softphone.

When Alice sends a fax to Bob extension, the following happens on my system:
- Bob phone starts to ring
- Bob answers
- asterisk sends the incoming call to appropriate fax extension
- Bob is hearing nothing at all: no tone, no sound at all.

I want to play an audio file back to Bob, something "Do not panic, you are
receiving a fax', before hanging up.

How can I do this ?

Playing with pre-dial handlers, I could enter the dialplan context I
dedicated to this feature but obviously, inside that context, applications
like Wait or Playback fail with messages like:

    -- Executing [s at check-fax-reception:2]
Playback("SIP/7005-0000028f",
"tt-weasels") in new stack
[Aug 13 16:19:03] WARNING[24235][C-0000046f]: file.c:830
ast_readaudio_callback: Failed to write frame

Or:

    -- Executing [s at check-fax-reception:2]
Wait("SIP/7005-00000291", "0.5")
in new stack
  == Spawn extension (check-fax-reception, s, 2) exited non-zero on
'SIP/7005-00000291'
[Aug 13 16:36:32] NOTICE[24309][C-00000470]: app_stack.c:1031 gosub_run:
SIP/7005-00000291 Abnormal
'Gosub(check-fax-reception,s,1(SIP/7012-00000290,7005))' exit.  Popping
routine return locations.



My understanding is :
when a fax is detected and sent a fax extension, callee channel is in a
state "close to termination" which is not compatible with many
dialplan
applications.


How can I work around this ?
Suggestions ?

Regards
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Le 13/08/2013 16:41, Olivier a ?crit :
> Hello,
Hi
>
> [...]
>
> How can I work around this ?
> Suggestions ?
Answer the call, wait few seconds and then ring Bobs extension. If 
asterisk detect fax it already sended to fax extension so Bobs phone 
will never ring.

-- 
Daniel