[asterisk-dev] Analyze inband DTMF in channel driver

[Russell Bryant]

On Wed, 2010-09-15 at 21:51 +0200, Artem Makhutov wrote:
> I would like to add inband DTMF analyzation to chan_datacard.
> 
> When I got a call from GSM --> Asterisk via chan_datacard I have only 
> inband DTMF.
> 
> When this call is forwarded to an other asterisk server via SIP or IAX
> only audio get forwarded and the other server may get problems analyzing 
> DTMF due to jitter, packet loss and audio codec compression.
> 
> So I would like to analyze the inband DTMF directly on the server that 
> is connected to the GSM Network and forward all DTMF data out of band.
> 
> Can you give we some hints where to look to implement this?

Both chan_sip and chan_dahdi (at least) support inband DTMF.  Search for
"ast_dsp" in those channel drivers to find the relevant code.  It is
handled using the API defined in include/asterisk/dsp.h.

-- 
Russell Bryant
Digium, Inc.  |  Engineering Manager, Open Source Software
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