PHU COMPRESSOR

A free, open-source OTT-style dual-band compressor VST3 plugin built with JUCE.
Combines classic downward compression (tame loud signals) with upward compression (lift quiet signals) in a single, lightweight processor — perfect for glue compression, mastering levelling, or parallel pumping effects.

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Table of Contents

• Features
• Parameters
• Installation
  • Pre-built Binaries
  • Supported Platforms
• Building from Source
  • Windows
  • Linux
  • CMake Presets
• Project Structure
• Contributing
• License
• Acknowledgements

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Features

• Dual-mode compression — independent downward and upward compressor in one plugin
• OTT-style gain computation — ratio-based power-law mapping with smooth ballistic envelopes
• Per-channel stereo processing — left and right channels processed independently
• Zero-latency — no look-ahead; tail length is zero
• Preset state save/restore — full DAW automation and session recall via APVTS
• Lightweight — no web browser, no CURL, no unnecessary JUCE modules
• FOSS — MIT licensed; source included, forks welcome

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Parameters

Parameter	ID	Range	Default	Description
Down Threshold	down_thresh	−60 … 0 dB	−12 dB	Level above which downward compression engages
Down Ratio	down_ratio	1 … 20	4	Downward compression ratio (N:1)
Up Threshold	up_thresh	−60 … 0 dB	−30 dB	Level below which upward compression engages
Up Ratio	up_ratio	1 … 20	4	Upward compression ratio (N:1)
Attack	attack_ms	0.1 … 200 ms	10 ms	Attack time for both compressors
Release	release_ms	1 … 2 000 ms	100 ms	Release time for both compressors

All parameters are fully automatable and saved with the DAW project.

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Installation

Pre-built Binaries

Download the latest pre-built VST3 from the Releases page.

Windows

1. Download PHU-COMPRESSOR-windows.zip from the latest release.
2. Extract and copy PHU COMPRESSOR.vst3 to your VST3 folder:

   C:\Program Files\Common Files\VST3\
   

3. Rescan plugins in your DAW.

Linux

1. Download PHU-COMPRESSOR-linux.zip from the latest release.
2. Extract and copy PHU COMPRESSOR.vst3 to:

   ~/.vst3/
   # or system-wide:
   /usr/lib/vst3/

3. Rescan plugins in your DAW.

Supported Platforms

Platform	Architecture	Format
Windows 10 / 11	x64	VST3
Ubuntu 22.04+ / Debian	x64	VST3
Other Linux	x64	VST3 (build from source)

macOS is not yet officially supported (contributions welcome — see Contributing).

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Building from Source

Prerequisites

• Git (with submodule support)
• CMake ≥ 3.23
• C++17-capable compiler (MSVC 2022+ on Windows, GCC 11+ / Clang 13+ on Linux)

Clone the repository with submodules (JUCE is a submodule):

git clone --recurse-submodules https://github.com/huberp/phu-compressor.git
cd phu-compressor

If you already cloned without --recurse-submodules:

git submodule update --init --recursive

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Windows

Quick build (batch script)

scripts\build.bat

The script configures and builds a Release VST3 using the vs2026-x64 CMake preset. The output is placed in:

build\vs2026-x64\src\phu-compressor_artefacts\Release\VST3\PHU COMPRESSOR.vst3

Create a release package

scripts\release.bat

This builds Release and zips the VST3 into dist\PHU-COMPRESSOR-windows.zip.

Manual steps

cmake --preset vs2026-x64
cmake --build --preset release

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Linux

Install system dependencies first (Ubuntu / Debian):

sudo bash scripts/install-linux-deps.sh

Then build:

cmake --preset linux-release
cmake --build --preset linux-build

The built plugin is at:

build/linux-release/src/phu-compressor_artefacts/Release/VST3/PHU COMPRESSOR.vst3/

Install to your user VST3 folder:

cp -r "build/linux-release/src/phu-compressor_artefacts/Release/VST3/PHU COMPRESSOR.vst3" \
    ~/.vst3/

For detailed Linux instructions see docs/LINUX_BUILD.md.

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CMake Presets

Preset	Platform	Description
vs2026-x64	Windows	Visual Studio 2026, x64
linux-release	Linux	Unix Makefiles, Release
release (build)	Windows	Release build targeting phu-compressor_VST3
debug (build)	Windows	Debug build
linux-build (build)	Linux	Release build

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Project Structure

phu-compressor/
├── src/
│   ├── OttCompressor.h        # Core DSP — OTT-style compressor (header-only)
│   ├── PluginProcessor.cpp/.h # JUCE AudioProcessor: parameter setup & audio routing
│   ├── PluginEditor.cpp/.h    # JUCE AudioProcessorEditor: slider UI
│   └── CMakeLists.txt         # Plugin target definition
├── JUCE/                      # JUCE framework (git submodule)
├── scripts/
│   ├── build.bat              # Windows quick-build script
│   ├── release.bat            # Windows release-package script
│   └── install-linux-deps.sh  # Linux dependency installer
├── docs/
│   └── LINUX_BUILD.md         # Detailed Linux build guide
├── .github/
│   └── workflows/
│       ├── build.yml          # CI: build + pluginval on every push/PR
│       └── release.yml        # CD: publish a GitHub Release on version tags
├── CMakeLists.txt
├── CMakePresets.json
└── LICENSE                    # MIT

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Contributing

Contributions, bug reports and feature requests are welcome!

1. Fork the repository.
2. Create a branch: git checkout -b feature/my-feature
3. Commit your changes with a clear message.
4. Open a Pull Request against main.

Please keep code style consistent with the existing .clang-format configuration (BasedOnStyle: Google, 100-column line limit).

Ideas for future improvements:

• macOS / AU support
• Gain reduction meter in the UI
• Mid/Side processing mode
• Multiband (phu-splitter integration)

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License

MIT License — © 2026 huberp

You are free to use, modify, and distribute this plugin in both open-source and commercial projects. Attribution is appreciated but not required.

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Acknowledgements

• JUCE — cross-platform C++ audio framework (ISC / GPL)
• pluginval — plugin validation used in CI
• Inspired by the classic OTT multiband compressor preset