deinvert
deinvert is a scrambler-descrambler for voice inversion scrambling. It supports simple inversion as well as split-band inversion.
Prerequisites
By default, deinvert requires liquid-dsp and libsndfile.
But it can be compiled without liquid-dsp using the configure
option --without-liquid
; filtering will be disabled and the result will not
sound as good. It can also be compiled
without libsndfile using the configure option --without-sndfile
; WAV
support will be disabled, only raw input/output will work.
Compiling
./autogen.sh
./configure [--without-liquid] [--without-sndfile]
make
Usage
Descrambling a WAV file scrambled with setting 4:
./src/deinvert -i input.wav -o output.wav -p 4
Descrambling split-band inversion with a bandwidth of 3500 Hz, split at 1200 Hz:
./src/deinvert -i input.wav -o output.wav -f 3500 -s 1200
Descrambling a live FM channel at 27 Megahertz from an RTL-SDR, setting 4:
rtl_fm -M fm -f 27.0M -s 12k -g 50 -l 70 | ./src/deinvert -r 12000 -p 4
Note that since scrambling and descrambling are the same operation this tool also works as a scrambler.
If no input and output file is given, deinvert reads raw 16-bit PCM via stdin and outputs in the same format via stdout. The inversion carrier defaults to 2632 Hz.
./src/deinvert [OPTIONS]
-f, --frequency FREQ Frequency of the inversion carrier, in Hertz.
-h, --help Display this usage help.
-i, --input-file FILE Use an audio file as input. All formats
supported by libsndfile should work.
-o, --output-file FILE Write output to a WAV file instead of stdout. An
existing file will be overwritten.
-p, --preset NUM Scrambler frequency preset (1-8), referring to
the set of common carrier frequencies used by
e.g. the Selectone ST-20B scrambler.
-q, --quality NUM Filter quality, from 0 (worst quality, low CPU
usage) to 3 (best quality, higher CPU usage). The
default is 2.
-r, --samplerate RATE Sampling rate of raw input audio, in Hertz.
-s, --split-frequency Split point for split-band inversion, in Hertz.
-v, --version Display version string.
Inversion carrier presets
No | Frequency |
---|---|
1 | 2632 Hz |
2 | 2718 Hz |
3 | 2868 Hz |
4 | 3023 Hz |
5 | 3196 Hz |
6 | 3339 Hz |
7 | 3495 Hz |
8 | 3729 Hz |
Troubleshooting
Can't find liquid-dsp on macOS
If you've installed liquid-dsp yet configure
can't find it, it's possible that
XCode command line tools aren't installed. Run this command to fix it:
xcode-select --install
Can't find liquid-dsp on Linux
Try running this in the terminal:
sudo ldconfig
Licensing
deinvert is released under the MIT license, which means it is copyrighted to Oona Räisänen OH2EIQ yet you're free to use it provided that the copyright information is not removed. See LICENSE.