sndgrep searches a provided input file or direct PCM stream of audio data for a specified tone. This tool was originally designed to find DTMF tones in audio streams.

This tool can also generate tones (including dtmf) and write that output to a file. However, that is not the primary use of this tool. Personally, I am thinking about making this tone-generation feature only available in debug mode.

Note that this searches for the specified tone one second at a time.

This is pre-alpha and there is a ton of testing that needs to be done. Primarily, I only care about DTMF, so traditional tones have not been tested (e.g., you can feel free to test these by NOT specifying the --dtmf command line argument).

Running a test make test will overwrite any files named: test.dat, test[0-9].dat

Currently this tool only supports PCM as input to search, or output to create. Specifically, 64bit PCM at an 8kHz sampling rate.

TODO:

• Support fractional frequencies
• Support multiple input and output formats
• More testing
• Better searching (more fine than one second a time)

libfftw: Fourier Transform Library http://www.fftw.org

libalsa: (optional) Advanced Linux Sound Architecture http://www.alsa-project.org/

Generated audio can be directly played from sndgrep, but sndgrep must be built and the optional "libalsa" dependency is required. To achieve this annoying feature build sndgrep as: make EXTRA_CFLAGS="-DDEBUG_PLAYSOUND -lasound"

• Generate a 1 second DTMF tone of the '5' key: sndgrep --dtmf --generate -d 1 -t 5 myoutput.pcm

• Search for all DTMF number tones in a provided input file: sndgrep --dtmf --search somefile.pcm

• Search for all DTMF number tones in an audio stream: sndgrep --dtmf --search < /dev/mystream

• Using ALSA to generate sound: http://www.alsa-project.org/alsa-doc/alsa-lib/_2test_2pcm_min_8c-example.html
• Getting a frequency from an FFT result: https://stackoverflow.com/questions/4364823/how-to-get-frequency-from-fft-result
• DTMF: https://en.wikipedia.org/wiki/Dual-tone_multi-frequency_signaling */

enferex [email protected]