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VST3

Generates cross-platform VST3 plugins (.vst3 bundles) from gen~ exports using CMake and the Steinberg VST3 SDK.

OS support: macOS, Linux, Windows

Prerequisites

  • Python >= 3.10
  • CMake >= 3.19
  • C/C++ compiler (clang, gcc, or MSVC)
  • Network access on first configure (to fetch VST3 SDK, ~50MB; cached afterward)

Quick Start

# Create a VST3 project
gen-dsp ./my_export -n myeffect -p vst3 -o ./myeffect_vst3

# Build
cd myeffect_vst3
cmake -B build && cmake --build build

# Output: build/VST3/Release/myeffect.vst3/

Or use gen-dsp build:

gen-dsp build ./myeffect_vst3 -p vst3

How It Works

gen-dsp uses header isolation to separate VST3 SDK code from genlib code:

  • gen_ext_vst3.cpp -- VST3-facing wrapper (includes only VST3 SDK headers)
  • _ext_vst3.cpp -- genlib-facing bridge (includes only genlib headers)
  • _ext_vst3.h -- C interface connecting the two sides via an opaque GenState* pointer

The plugin uses SingleComponentEffect -- the simplest VST3 plugin structure that combines the audio processor and edit controller into a single class. The implementation passes all 47 tests in Steinberg's SDK validator.

Signal type: float (32-bit). gen~ is compiled with GENLIB_USE_FLOAT32.

Zero-copy audio: VST3's channelBuffers32[ch][sample] layout matches gen~'s float** exactly, so audio buffers are passed directly with no copying or format conversion.

Plugin type detection: Automatic based on I/O configuration:

  • Fx (effect) if the gen~ export has audio inputs
  • Instrument|Synth if the gen~ export has no audio inputs

Parameters

All gen~ parameters are exposed as RangeParameter instances with real names, min, max, and default values. Parameters are automatable by the host.

Plugin FUID: A deterministic 128-bit ID generated from the MD5 hash of com.gen-dsp.vst3.<lib_name>, split into 4 x uint32 and passed to CMake as hex values.

State Save/Restore

The plugin implements setState()/getState() on the SingleComponentEffect, allowing hosts to save and recall presets and session state. Parameters are serialized as a flat binary blob (4-byte magic header + one float per parameter) using IBStreamer. Invalid or empty state data is rejected on load.

Buffers

Buffer support follows the standard gen-dsp pattern. Up to 5 single-channel buffers are supported.

Build Details

  • Build system: CMake with FetchContent
  • SDK: Steinberg VST3 SDK fetched via CMake FetchContent (tag v3.7.9_build_61)
  • Audio format: Float32, non-interleaved (zero-copy)
  • Code signing: ad-hoc signed on macOS during build
  • Compile flags: -DGENLIB_USE_FLOAT32 -DWIN32 -DGENLIB_NO_DENORM_TEST
  • SDK class: SingleComponentEffect (combined processor + controller)

The generated CMakeLists.txt explicitly compiles vstsinglecomponenteffect.cpp and platform-specific entry points (macmain.cpp, etc.) from the SDK. The SDK's example and VSTGUI options are disabled (SMTG_ENABLE_VST3_PLUGIN_EXAMPLES=OFF, SMTG_ENABLE_VSTGUI_SUPPORT=OFF).

Shared FetchContent Cache

By default, gen-dsp bakes an OS-appropriate shared cache path into the generated CMakeLists.txt so that multiple projects share a single SDK download. Pass --no-shared-cache to disable this.

# Override the default shared cache at cmake configure time
GEN_DSP_CACHE_DIR=/path/to/cache cmake ..

Cache paths by OS:

OS Default shared cache path
macOS ~/Library/Caches/gen-dsp/fetchcontent/
Linux $XDG_CACHE_HOME/gen-dsp/fetchcontent/ (defaults to ~/.cache/)
Windows %LOCALAPPDATA%/gen-dsp/fetchcontent/

Using a Local SDK

If you already have the VST3 SDK on your system, you can skip the FetchContent download entirely by setting CMake's built-in FETCHCONTENT_SOURCE_DIR_<NAME> variable:

cmake -DFETCHCONTENT_SOURCE_DIR_VST3SDK=/path/to/vst3sdk -B build

This tells CMake to use your local copy instead of cloning from GitHub. No template or project changes are needed.

Note: the generated project pins SDK tag v3.7.9_build_61. If your local SDK is a different version, it will be used as-is with no version check. API differences between versions may cause build failures.

Install

OS Install path
macOS ~/Library/Audio/Plug-Ins/VST3/
Linux ~/.vst3/
Windows %COMMONPROGRAMFILES%/VST3/ 
# macOS
cp -r build/VST3/Release/myeffect.vst3 ~/Library/Audio/Plug-Ins/VST3/

# Linux
cp -r build/VST3/Release/myeffect.vst3 ~/.vst3/

Licensing

The VST3 SDK is GPL3/proprietary dual licensed. If you distribute your plugin under a proprietary (non-GPL) license, you must obtain a proprietary license from Steinberg.

Troubleshooting

  • CMake configure hangs: The VST3 SDK is ~50MB. The first download may take a while. If it seems stuck, check your network connection. Set GIT_TERMINAL_PROMPT=0 in your environment to prevent git from prompting for credentials.
  • STR macro redefinition warnings: The VST3 SDK redefines STR as STR16. The gen-dsp wrapper uses GSTR() to avoid this conflict. No action needed.
  • Plugin not appearing in DAW: Ensure the .vst3 bundle (it's a directory, not a single file) is in the correct install path. Restart the DAW to rescan.
  • First build is slow: The VST3 SDK is large. Subsequent builds reuse the cached SDK and are much faster. The shared cache is enabled by default; pass --no-shared-cache to disable it.