Is there a way to take the input of a sound card, check for DTMF, decode the DTMF, and pass the rest of the audio through the speaker?

Trying to code a software amateur radio repeater.

 

Of course there is, with FFT (as in Fast Fourier Transform) you can spot the tones you want
There are a lot of other ways too - of course...


/Johan Bengtsson

Do you need education in the area of automation?
> ----------------------------------------
> P&L, Innovation in training
> Box 252, S-281 23 Hässleholm SWEDEN
> Tel: +46 451 74 44 00, Fax: +46 451 898 33
> E-mail: [email protected]
> Internet: http://www.pol.se/
> ----------------------------------------

 

I just recently wrote a simple sound card DTMF decoder application using C++. It involves an FFT and a search for peak frequencies. I could send you the source code if you like. Contact me directly at [email protected].

-Robert Scott
Real-Time Specialties

 

Dear Mr Robert Scott
I am very happy to see your reply. This is what exactly I am searching for. I want to decode the DTMF signals present at input of my sound card. I appreciate if you give the sample code of your application. I also want to know whether any additional H/W is required for doing this job.
Thanks and regards
Sateesh babu

 

Dear Mr.Robert Scott
I tryed lot of methods to decode the dtmf in audio signals. and almost succeded the problem is whatever method i used also dectecting dtmf in voice also. is your decoder will help me solve my problem

 

Dear Robert,

I'm Rafael, student of computer engineering, from Brazil, was finding any informations about decode DTMF in language C allow all tones sound that I dial by my phone. When I dial my soundcard speaker receive this signal allow my hardware. The DTMF sound want decode in my PC and get in realtime as a string. I know that you hava a project or any sample code, want yoyr help to my project. Please, could you help me?

Thanks a lot, by your attention,

Rafael Roberto Prado

 

Try looking for FFT software with source. You
should be able to set thresholds at the DTMF fundamental frequencies and that's pretty close to a solution. There are a lot of kits for tone decoders as well. This problem has been solved for many years.

Regards

cww

 

You might also request the free CD with Sound and Vibration Resources at:
http://digital.ni.com/express.nsf/bycode/exjm4c?opendocument=en&node=seminar_US&node=12049
This is on the National Instruments Website, www.ni.com, under products, and sound and vibration

The CD is free and contains FFT analysis software that will work with your sound card. The system includes a zoom FFT which will allow you to view the two tones side by side in the FFT arena.

Hope this helps.

Sincerely,

Preston Johnson
Business Development Manager
Industrial Control and Measurements
National Instruments
11500 North Mopac Blvd, Bldg B
Austin, TX 78759

phone: 512-683-5444
fax: 512-683-8800
cell: 512-431-2371

www.ni.com/machine/mcm.htm
http://ni.com/analysis/monitoring.htm
[email protected]
www.ni.com