C FFT Visualizer

Overview #

A real-time FFT visualizer that renders log-frequency bars with fractional-octave smoothing, per-band peak-hold, and pink-noise compensation. Works with .wav files or a live microphone input. Warning: Early prototype. Sample rates of 48kHz and higher may make the visualization lag relative to the audio.

Problem / approach #

• Visualize audio spectra smoothly with configurable averaging and scaling.
• Keep latency low while supporting multiple smoothing/averaging modes.
• Provide flexible input: file playback or live mic.

Solution #

• C + FFTW3 for frequency analysis, Raylib for rendering, PortAudio for audio I/O.
• RTA-style analysis controls: fractional-octave smoothing, dB-domain averaging (EMA), peak-hold + max-hold trace, and cursor readouts.
• Display/analysis modes: pink compensation (pink-flat display) and frequency weighting (Z/A/C) with meter time-weighting.
• Mic-mode SPL calibration workflow (94 dB calibrator via key command).

Features #

• Log-frequency bars with fractional-octave smoothing (1/1…1/48)
• dB-domain time averaging (EMA) with Fast/Slow presets
• Per-band peak-hold with timed decay + persistent max-hold trace
• Peak-find + nearest-band lock navigation
• Cursor readout (hover for exact Hz and level)
• Pink compensation + frequency weighting modes (Z/A/C)
• dB grid overlay and peak/RMS meters

Controls (high level) #

• O octave scaling, C color gradients, P pink compensation
• A dB-domain averaging, F fast/slow preset, H peak-hold modes
• W Z/A/C weighting, T meter time-weighting
• K calibrate SPL to 94 dB (mic mode), G peak-find + cursor lock
• F11 fullscreen, Space freeze, R reset traces

Outcome #

• Responsive RTA-style display with dB-domain averaging and peak tracking.
• Works on typical Linux setups (e.g., sudo pacman -S clang raylib fftw portaudio).
• GPL-3.0 licensed, ready for tweaking visuals or analysis settings.

• Source
• Demo