Messages in this thread | | | Date | Tue, 07 Jan 2003 20:08:18 +0100 | From | Thomas Tonino <> | Subject | Re: [Asterisk] DTMF noise |
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Mark Spencer wrote:
> The DTMF detector in the linux kernel is fairly simplistic and doesn't do > many relative energy tests. The Zapata library has a much better tone > detector, but it is FP, and so would have to be made fixed point. If > nothing else, it may provide some lessons for the ISDN folks.
I remember that a good DTMF decoder can be very simplistic: DTMF was designed for that.
The idea is:
- separate the high tones from the low tones. - amplify clip the high band and the low band separately - run the tone decoders on the clipped signals
The clipping stage would make sure that only relatively pure tones will trigger the detector.
See also http://groups.google.com/groups?selm=7462%40accuvax.nwu.edu
Thomas
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