NIH-plug Spectrum Analyzer

A real-time audio spectrum analyzer plugin built with NIH-plug and Iced for the GUI. This plugin provides professional-grade spectrum analysis with adaptive windowing, customizable display options, and real-time metering.

Features

• Real-time FFT spectrum analysis with configurable resolution levels (128-2049 bins)
• Resolution-adaptive curve smoothing - Automatic curve radius adjustment based on resolution level
  • Low resolution: Large radius curves for smooth, flowing visualization
  • High resolution: Tight radius curves preserving fine detail
  • Frequency-aware smoothing: Larger curves for low frequencies, detailed high frequencies
• Adaptive windowing - Different window functions for low, mid, and high frequencies
• Lock-free audio/UI communication using triple buffering
• Level metering with peak hold and smoothed decay
• Perceptual tilt compensation (+4.5dB/octave) for flatter visual response
• Catmull-Rom spline rendering for professional-grade smooth spectrum curves
• Zero allocation in audio thread - Real-time safe processing

Architecture

The plugin follows a clean producer/consumer pattern:

• Audio thread (Producer): Generates spectrum and meter data
• UI thread (Consumer): Reads and displays the data
• Lock-free communication: Triple buffering for spectrum, atomic values for meters

Dependencies

Note: Currently using local paths for NIH-plug. Update these in Cargo.toml to point to external repos:

nih_plug = { git = "https://github.com/robbert-vdh/nih-plug.git" }
nih_plug_iced = { git = "https://github.com/robbert-vdh/nih-plug.git" }

Building

After installing Rust, you can compile the plugin:

cargo xtask bundle spectrum_analyser --release

The compiled plugin will be in target/bundled/ as:

• spectrum_analyser.clap - CLAP format

Installation Scripts (macOS)

⚠️ Note: The provided scripts are configured for macOS and use specific paths. You may need to adjust them for your system.

Quick Build & Install (scripts/run.sh)

This script automates the entire workflow:

1. Builds the plugin in release mode
2. Removes old plugin version from /Library/Audio/Plug-Ins/CLAP/
3. Installs the new version
4. Launches Bitwig Studio with logging enabled
5. Opens a tmux session with:
   • Left pane: Bitwig Studio
   • Right pane: Live log monitoring

./scripts/run.sh

Build Only (scripts/build.sh)

Just builds and installs the plugin without launching Bitwig:

./scripts/build.sh

Logging & Debugging

The plugin uses NIH-plug's logging system. You can add debug output in your code:

nih_plug::nih_log!("Debug message: value = {}", some_value);

When running through scripts/run.sh, logs are:

• Written to: ~/Library/Logs/Bitwig/nih.log
• Displayed in real-time in the tmux right pane
• Enabled via the NIH_LOG environment variable

Manual Logging Setup

To enable logging when running your DAW manually:

# For Bitwig Studio
NIH_LOG=~/Library/Logs/Bitwig/nih.log "/Applications/Bitwig Studio.app/Contents/MacOS/BitwigStudio"

# For other DAWs, adjust the path accordingly
NIH_LOG=~/my_plugin.log /path/to/your/daw

Platform Notes

• macOS: Scripts assume CLAP plugins go in /Library/Audio/Plug-Ins/CLAP/
• Linux: Adjust paths in scripts, typically ~/.clap/ or /usr/lib/clap/
• Windows: Adjust paths, typically C:\Program Files\Common Files\CLAP\

Development

This is a learning project focused on:

• Lock-free audio programming patterns
• Real-time safe DSP in Rust
• Custom Iced widgets with Canvas
• Functional programming in systems contexts

License

TODO: Add license information