Vox Spec (vox-spec)

A real-time vocal overtone, pitch tracking, and timbre visualizer built with Rust, egui, and cpal. Supports both desktop (Linux/macOS/Windows) and Android.

Features

• Real-Time Pitch Tracking: Sub-harmonic fundamental frequency ($f_0$) tracking using autocorrelation / MPM with octave jump protection.
• Narrowband Spectrogram & Overtone Analysis: FFT-based harmonic tracking with spectral tilt and formants.
• Vocal Mode & Timbre Crosshair: 2D vocal resonance mapping (Edge/Belt, Overdrive, Twang Mix, Neutral/Falsetto) based on spectral tilt ($\Delta H12$) and twang / pharyngeal ring energy.
• Audio Inputs:
  • Real-time microphone input via cpal
  • Audio file decoding and playback (wav, mp3, flac, aac) via symphonia
  • Built-in test tone generator (329.6 Hz $E_4$)
• Cross-Platform UI: Built with egui / eframe with responsive portrait mobile layout and desktop views.

Architecture

The application runs decoupled threads communicating via lock-free primitives:

1. Audio Input Thread: Real-time stream capture and decoding (cpal, symphonia).
2. DSP Worker Thread: Narrowband FFT (realfft), pitch detection, harmonic extraction, and vocal mode estimation.
3. UI Render Thread: Immediate-mode GPU rendering (eframe/glow).

See spec.md for full technical specifications.

Building & Running

Desktop (Linux / macOS / Windows)

cargo run --release

Android APK

Prerequisites:

• Android SDK (API 34) & NDK (r25+)
• cargo-apk (cargo install cargo-apk)
• Rust targets:

  rustup target add aarch64-linux-android x86_64-linux-android

Build and sign the APK:

./android/build-apk.sh

Install to a connected device:

adb install -r vox-spec-release.apk

License

MIT OR Apache-2.0