demodulator

Yet another FM demodulator as a way for me to spend (i.e. waste) my spare time playing with different ways to learn DSP.

Building

Clone this repo, then use cmake to build. The code has been tested on various *nix platforms (e.g. Ubuntu 18+ aarch64, Debian buster armhf, Ubuntu 20+ x64, MacOS 13.3 and Ubuntu on WSL2), but the various automation scripts may not function as expected on all systems.

mkdir build && cd build && cmake .. && make -j$(nproc)

CMake compile options

• -DIS_NVIDIA compiles CUDA version, requires nvcc (https://docs.nvidia.com/cuda/cuda-installation-guide-linux/index.html) , default: OFF

Usage

Required command-line parameters

• -i input file; use '-' to specify stdin
• -o output file; use '-' to specify stdout

Optional command-line parameters

• -L input signal lowpass cutoff frequency (ωc), default: none, skips input lowpass entirely
• -l output signal lowpass cutoff frequency (ωc), default: 1
• -S output sampling rate, default: 10

Examples

Using DSD

sox -q -D -twav <some-wav-iq-wav-file> -traw -eunsigned-int -b8 -r192k - \
| build/demodulator -i - -o - -S96000 -l12500 \
| sox -q -D -traw -b32 -ef -r96k - -traw -es -b16 -r48k - \
| dsd -i - -o/dev/null -n

Using multimon-ng

sox -q -D -twav <some-wav-iq-wav-file> -traw -eunsigned-int -b8 -r192k - \
| build/demodulator -i - -o - -S96000 -l6500 -L12500 \
| sox -q -D -traw -b32 -ef -r96k - -traw -es -b16 -r22050 - \
| multimon-ng -q -c -a<some-codecs> -