How can I decode DTMF using Audacity and Multimon
This article assumes you have captured audio from your Digium card utilizing dahdi_monitor. You can find an instructional article at this link: How do I record calls using dahdi monitor
Programs you will need:
Audacity: Multi-track audio editor for Linux/Unix, MacOS and Windows. It is designed for easy recording, playing and editing of digital audio.
Multimon: The executable name for Linux Radio Transmission Decoder, software that can decode a variety of digital transmission modes.
Once you have the software installed and the wave files that you would like to analyze , please use the following steps to edit and decode DTMF.
If you are attempting to verify DTMF that Asterisk is sending, select the outgoing stream (TX) wave file, and open it in Audacity. If you are attempting to verify DTMF that Asterisk is receiving, you would select incoming stream (RX) instead.
These names depend on using the dahdi_monitor naming convention suggested in the article linked above.
Listen to your audio file to locate the DTMF you would like to analyze.
Using your mouse, click and drag to highlight the waveforms you want to select.
Click 'File' in the menu bar, and select 'Export Selection'.
Select your desired save location and ensure WAV is the selected file type.
Open a terminal and run the following command:
multimon -t wav -a DTMF <location of .wav file>
If successful, you will see the following output:
multimod (C) 1996/1997 by Tom Sailer HB9JNX/AE4WA
available demodulators: POCSAG512 POCSAG1200 POCSAG2400 EAS AFSK1200 AFSK2400 AFSK2400_2 HAPN4800 FSK9600 DTMF ZVEI CCIR SCOPE
Enabled demodulators: DTMF
DTMF: 1
DTMF: 2
DTMF: 5