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Project

C FFT Visualizer

Real-time audio spectrum visualizer using C, FFTW3, Raylib, and PortAudio.

Role

Systems + Graphics

Date

27-09-2025

Tech
CRaylibFFTW3PortAudio

Highlights

  • Log-frequency bars with fractional-octave smoothing (1/1…1/48)
  • dB-domain time averaging (EMA) + per-band peak-hold/max-hold
  • Mic or WAV input via PortAudio; weighting modes (Z/A/C) + pink compensation

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.

C FFT Visualizer spectrum view
FFT spectrum with log-frequency bars, peak-hold, and dB grid.

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.