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Topic: looking for a program that can filter out DTMF tones in realtime (Read 7974 times) previous topic - next topic
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looking for a program that can filter out DTMF tones in realtime

I have an audio stream that contains voice and DTMF (touch tone) sounds.  I would like to be able to reduce the volume of the touch tones only.

I'm thinking some type of DSP notch filter.

looking for a program that can filter out DTMF tones in realtime

Reply #1 –
Yes.  Notch filters should help.  Do you have an audio editor?    (If you don't have an audio editor, Audacity[/color] is FREE!)  I don't use Audacity that much and I'm not sure if it comes with a notch filter, but I assume you can get one for it.

I think you'll get the best results if you go through the file and manually select the correct filters for each tone, rather than applying all of the notch filters to the whole file. 

As you may know, DTMF means Dual Tone Multi-Frequency.  That means each tone contains two frequencies and you need two notch filters for each tone.

Wikipedia DTMF chart[/u] showing the frequency combinations for each key.

looking for a program that can filter out DTMF tones in realtime

Reply #2 –
Thanks for the reply.

Audacity is a great program, and it does have a notch filter plugin.  However, I need something that will filter in real-time (on a Windows XP machine).

Still open to suggestions 

looking for a program that can filter out DTMF tones in realtime

Reply #3 –
Quote from: drmartell on
Thanks for the reply.

Audacity is a great program, and it does have a notch filter plugin.  However, I need something that will filter in real-time (on a Windows XP machine).

Still open to suggestions 


SAVIHost is a standalone VST host that makes any VST plugin work like a separate program.
MiniHost is similar.

You can find a good free VST eq here

looking for a program that can filter out DTMF tones in realtime

Reply #4 –
Quote
Audacity is a great program, and it does have a notch filter plugin. However, I need something that will filter in real-time (on a Windows XP machine).
  Sorry...  I guess I didn't read your post carefully...

looking for a program that can filter out DTMF tones in realtime

Reply #5 –
Quote from: Iain on
SAVIHost is a standalone VST host that makes any VST plugin work like a separate program.
MiniHost is similar.

You can find a good free VST eq here


Thanks, I was able to use VSTHost from the first website you suggested and then add multiple instances of 'Tom's Notch' VST plugin to do the trick.  It is working just as I hoped.

Now DTMF tones are accurately transferred from my analog phone through Skype while still allowing voice.