Plugins Host Vst Plugin
Vst Host Plugins
Plugins Vst Host
Plugins Host Vst Plugins

Want to use some of the comprehensive FX plug-ins that REAPER provides, but stuck in another host? Haven't made the switch yet? Fear not - you can download ReaPlugs, a package of FX that includes many of the plug-ins that come with REAPER, for free! Hosts - VST - Here you will find software which will allow you to host and use VST instrument and effect plug-ins. Hosts may be incorporated in production suites and sequencers or be stand-alone applications. For a large selection of VST plug-ins see the Plug-ins - VST and Plug-ins - VSTi categories. Gig Performer is a cross-platform (Mac/Windows) audio plugin host for both live performance and session musicians (keyboard players, guitarists, singers, drummers, FOH engineers) looking for an intuitive fast and flexible VST/VST3/AU plugin hosting environment for their software synths and effects. Minihost Modular is a modular environment for hosting/interconnecting VST/AU plugins based on a custom modular engine especially developed for this purpose. As a standalone, Minihost Modular can be used as an advanced VST or AU host with modular routing with some sequencing recording/playback capabilities. Advanced Audio Plugin Host Element is a modular AU/VST audio plugin host. Connect plugins to create power effects racks and instruments. Load graphs on the fly for quick access to your sounds.

Introduction

Writing VST plugins is a lot of fun, but it’s even more fun to write your own host which uses the wide variety of plugins already out there to do something original and new. Making your own VST host is not a trivial task, but the trickiest part is figuring out how to load the plugins and connect them to your code’s callback functions. As the VST documentation is a bit sparse on the subject of hosting, this guide will assist you in setting up your own host.

This guide only covers loading the plugin and basic communication, and the language of choice here is C++. C# programmers should consider using the VST.NET framework, and I’m not sure what frameworks exist for other languages.

Also, it’s worth noting that Teragon Audio has developed an open-source VST host, MrsWatson. Feel free to look at the code and fork it for your own project! If you find yourself using a substantial portion of the MrsWatson source in your own code, please let me know so I can add a link to your project from the MrsWatson page.

Code conventions

In the course of your development, you will probably require logging, error handling, etc. To simplify the code in this tutorial, I have simply written “return -1” or “return NULL” statements, but you should consider expanding this to log some info or handle the error.

Also, this tutorial is written for both Windows and Mac OSX developers. As such, there is a lot of platform-specific code, which you will probably need to box with #ifdef/#endif statements in the preprocessor.

Setting up your build environment

You’ll need to first download and install the following tools:

Steinberg’s VST SDK, which requires you to make a free Steinberg Developer account. This tutorial assumes you are working with the VST 2.4 SDK.
Microsoft’s Visual C++ 2010 Express, if you wish to support Windows.
Microsoft’s Platform SDK, again if you are developing on Windows.
Xcode 4.x, if you are developing on Mac OS X.

Plugins Host Vst Plugin

Project configuration

Aside from your project files, you need only to add the VST SDK headers into your project’s include path. This includes the following files, which are located under the vstsdk2.4/pluginterfaces/vst2.x directory:

aeffect.h
aeffectx.h
vsfxstore.h

On both Windows and Mac OSX, you should probably configure your program to build as a 32-bit binary, simply because most VST plugins are not 64-bit compatible yet. On the Mac, this gets to be a bit hairy because Apple is working to deprecate Carbon, which is a 32-bit framework. If anyone out there has example code in C (not objective-C) to load a plugin from bundle without using Carbon, please let me know so I can update this article.

Loading the VST plugin

After your host performs its own internal initialization routines, it is time to load the VST plugin from source. This procedure varies a bit depending on the platform, but the algorithm is fundamentally the same: find the plugin, load the dynamic library into memory, acquire the plugin’s main address, and create a VST callback connection. These callbacks are defined function pointers which you should define in one of your project’s header files, and are as follows:

On Windows, VST plugins are simply dynamically linked libraries (DLL’s). The code for opening a DLL library in Windows is fairly simple:

On Mac OSX, VST plugins are also dynamic libraries, but they are packaged as bundles. Your host can open these bundles through the Carbon API. On Mac OS9, VST plugins were packaged as CFM files, which has long since been deprecated, and it is highly unlikely that any modern VST host should need to support this format.

The procedure for opening a plugin under OSX is a bit more complex, but the code should be fairly straightforward. Keep in mind that although a VST plugin can be loaded from any location on disk, they are usually stored in either /Library/Audio/Plug-Ins/VST or $HOME/Library/Audio/Plug-Ins/VST.

Anyways, to load the VST plugin on Mac OSX, that will look something like this:

You need to keep the bundle pointer around until the host is ready to unload the plugin. At this point, you call CFBundleUnloadExecutable and then CFRelease on the bundle’s reference.

Setting up plugin callbacks

At this point, you should now have successfully loaded the plugin into memory, and you can now establish the plugin dispatcher callbacks:

Plugin initialization

At this point, the plugin should be ready to go, so you can initialize it through the dispatcher handle created in the previous step:

Suspending and resuming

Calling the plugin’s suspend and resume methods are a bit counter-intuitive, and are done like this:

Plugin capabilities

The VST protocol uses “canDo” strings to define plugin capabilities, the most common of which are defined in audioeffectx.cpp in the PlugCanDos namespace near the top of the file. To ask a plugin if it supports one of these capabilities, make the following dispatcher call:

Host capabilities

The plugin can also ask the host if it supports a given capability, which is done through the hostCallback() function defined above. The implementation of this file looks something like this:

The full list of opcodes is defined in aeffect.h (for the VST 1.x protocol) and aeffectx.h (for VST 2.x protocol). There are a lot of opcodes, and your application doesn’t need to support them all, but you will soon figure out which ones are the most important through trial and error. Depending on the nature of the opcall, you will either be required to return a given integer value, call a method in the plugin’s dispatcher, or fill the *ptr pointer with some type of data. The VST SDK header files have fairly good documentation specifying what you need to do depending on the opcode.

The MrsWatson source code also contains an example implementation of this function with the most common opcode cases.

Processing audio

In the VST SDK 2.4, processReplacing() became the new standard call. You may have to add in support to your host for the old style of process() plugins, though there aren’t so many plugins out there which still do this. To have the plugin process some audio:

In the above code, there is an inputs and outputs array which should be initialized by your application as soon you have calculated the desired channel count and buffer size. You should not allocate the inputs and outputs arrays in the processAudio() function, as doing so may severely impact performance. Hence, the call to initializeIO() should be made as soon as possible and before the first call to processAudio(). You should also take care to properly initialize the data in both the inputs and outputs array to zero, or else you can g