C FFT Visualizer

Real-time FFT spectrum analyzer for audio files and live microphone input. Built with C, FFTW3, Raylib, and PortAudio.

Note: Early prototype. Only WAV files and microphone input are supported. Sample rates above 48 kHz may cause the visualization to lag behind the audio.

Requirements

• Clang
• Make
• Raylib
• FFTW3
• PortAudio

Prerequisites

Arch Linux

sudo pacman -S clang raylib fftw portaudio

Debian/Ubuntu (24.04+)

sudo apt-get install -y clang libraylib-dev libfftw3-dev portaudio19-dev

Debian/Ubuntu (< 24.04)

libraylib-dev is only in Ubuntu 24.04+/Debian 13+. For older releases, install raylib from source:

git clone https://github.com/raysan5/raylib.git /tmp/raylib
cd /tmp/raylib && mkdir build && cd build
cmake -DBUILD_SHARED_LIBS=ON -DCMAKE_BUILD_TYPE=Release ..
make -j$(nproc)
sudo make install
sudo ldconfig

Then install the remaining dependencies:

sudo apt-get install -y clang libfftw3-dev portaudio19-dev

Build

make build
make run
make clean
make format
make help

Usage

# Audio file (loop optional)
./build/c_fft_visualizer <path_to_audio_file> --loop

# Live microphone
./build/c_fft_visualizer --mic

Controls

Key	Action
O	Cycle octave scaling (1/1 ... 1/48)
C	Cycle color gradients
P	Toggle pink compensation
A	Toggle dB-domain averaging vs linear
F	Toggle Fast/Slow averaging preset
H	Cycle peak-hold (Off, 0.5s, 1.0s, 2.0s)
W	Cycle frequency weighting (Z/A/C)
T	Cycle meter time weighting (Fast/Slow/Impulse)
K	Calibrate SPL to 94 dB reference (mic mode)
G	Peak-find from max-hold trace and lock cursor
Left/Right	Step locked band by one bar
Mouse Left	Toggle nearest-band lock
R	Reset peak and max-hold traces
Space	Freeze/Unfreeze live trace
F11	Toggle fullscreen

Features

• Log-frequency bars with fractional-octave smoothing (1/1 ... 1/48)
• dB-domain time averaging (EMA) with Fast/Slow presets
• Frequency weighting modes (Z/A/C)
• SPL calibration workflow (94 dB calibrator via key command)
• Per-band peak-hold with timed decay
• Persistent max-hold trace (manual clear)
• Peak-find and nearest-band lock navigation
• Pink compensation (pink-flat display)
• dB grid overlay and peak/RMS meters
• Cursor readout (hover for exact Hz and level)

Configuration

Edit include/config.h to tune defaults.

Default FFT: FFT_WINDOW_SIZE=8192, FFT_HOP_SIZE=FFT_WINDOW_SIZE/16. Increase window size for finer bass resolution; decrease for faster transient tracking. Adjust UI_SCALE if text and panels look too small or too large.

Screenshot

License

GPL-3.0