yabridge

Yet Another way to use Windows VST plugins on Linux. Yabridge seamlessly supports running both 64-bit Windows VST2 plugins as well as 32-bit Windows VST2 plugins in a 64-bit Linux VST host. This project aims to be as transparent as possible to achieve the best possible plugin compatibility while also staying easy to debug and maintain.

Tested with

Yabridge has been verified to work correctly in the following VST hosts using Wine Staging 5.5 and 5.6:

• Bitwig Studio 3.1 and the beta releases of 3.2
• Carla 2.1 (does not support opening multiple symlinked plugins in the same session)
• Ardour 5.12
• REAPER 6.09 (does not support symlinks)

At the moment there is a regression in Wine 5.7 that breaks application startup behavior, so you'll have to temporarily downgrade to an earlier version of Wine if you're got Wine 5.7 isntalled. Please let me know if there are any issues with other VST hosts.

Usage

You can either download a prebuilt version of yabridge through the GitHub releases section, or you can compile it from source using the instructions in the build section below.

There are two ways to use yabridge. The recommended way is to use symbolic links. The main advantage here is that you will be able to update yabridge for all of your plugins in one go, and it avoids having to install anything outside of your home directory. Sadly, not all hosts support this behavior. See the list above for hosts that don't.

If you have downloaded the prebuilt version of yabridge or if have followed the isntructions from the bitbridge section below, then yabridge is also able to load 32-bit VST plugins. The installation procedure for 32-bit plugins is exactly the same as for 64-bit plugins. Yabridge will detect whether a plugin is 32-bit or 64-bit on startup and it will handle it accordingly.

It's also possible to use yabridge with multiple Wine prefixes. Yabridge will automatically detect and use the Wine prefix the plugin's .dll file is located in. Alternatively you could set the WINEPREFIX environment variable to override the Wine prefix for all instances of yabridge.

Symlinking (recommended)

This is the recommended way to use yabridge if you're using Bitwig Studio or Ardour. You can either use the prebuilt binaries from the GitHub releases section, or you could build yabridge directly from source. If you use the prebuilt binaries, then you can simply extract them to ~/.local/share/yabridge or to anywhere else in your home directory. If you choose to build from source, then you can use the compiled binaries directly from the build/ directory. For the section below I'm going to assume you've extracted the files to ~/.local/share/yabridge.

To set up yabridge for a VST plugin called ~/.wine/drive_c/Program Files/Steinberg/VstPlugins/plugin.dll, simply create a symlink from ~/.local/share/yabridge/libyabridge.so to ~/.wine/drive_c/Program Files/Steinberg/VstPlugins/plugin.so like so:

ln -s ~/.local/share/yabridge/libyabridge.so "$HOME/.wine/drive_c/Program Files/Steinberg/VstPlugins/plugin.so"

As an example, if you wanted to set up yabridge for all VST plugins under ~/.wine/drive_c/Program Files/Steinberg/VstPlugins, you could run the following script in Bash. This will skip any .dll files that are not actually VST plugins.

yabridge_home=~/.local/share/yabridge

find "$HOME/.wine/drive_c/Program Files/Steinberg/VstPlugins" -type f -iname '*.dll' -print0 |
  xargs -0 -P$(nproc) -I{} bash -c "(winedump -j export '{}' | grep -qE 'VSTPluginMain|main|main_plugin') && printf '{}\0'" |
  sed -z 's/\.dll$/.so/' |
  xargs -0 -n1 ln -sf "$yabridge_home/libyabridge.so"

Copying

If your VST host does not have support for symlinked VST plugins, then you can also install yabridge by creating copies of the libyabridge.so file instead of using symlinks. For this you will have to make sure that all four of the yabridge-host* files from the downloaded archive are somewhere in the search path. The recommended way to do this is to download yabridge from the GitHub releases section, extract all the files to ~/.local/share/yabridge, and then add that directory to your $PATH environment variable. Alternatively there's an AUR package available if you're running Arch or Manjaro.

The installation process for a plugin is the same as the procedure described above, but instead of creating a symlink from libyabridge.so to plugin.so, you'll now have to create a copy. Using the same example, if you have extracted yabridge's files to ~/.local/share/yabridge and you want to set up yabridge for a VST plugin called ~/.wine/drive_c/Program Files/Steinberg/VstPlugins/plugin.dll, then you should copy ~/.local/share/yabridge/libyabridge.so to ~/.wine/drive_c/Program Files/Steinberg/VstPlugins/plugin.so like so:

cp ~/.local/share/yabridge/libyabridge.so "$HOME/.wine/drive_c/Program Files/Steinberg/VstPlugins/plugin.so"

You could also use a modified version of the installation script from the previous section to install yabridge for all of you VST plugins at once:

yabridge_home=~/.local/share/yabridge

find "$HOME/.wine/drive_c/Program Files/Steinberg/VstPlugins" -type f -iname '*.dll' -print0 |
  xargs -0 -P$(nproc) -I{} bash -c "(winedump -j export '{}' | grep -qE 'VSTPluginMain|main|main_plugin') && printf '{}\0'" |
  sed -z 's/\.dll$/.so/' |
  xargs -0 -n1 cp "$yabridge_home/libyabridge.so"

Runtime dependencies and known issues

Any VST2 plugin should function out of the box, although some plugins will need some additional dependencies for their GUIs to work correctly. Notable examples include:

• Serum requires you to disable d2d1.dll in winecfg and to install gdiplus through winetricks.

Aside from that, these are some known caveats:

• Plugins by KiloHearts have file descriptor leaks when esync is enabled, causing Wine and yabridge to eventually stop working after the system hits the open file limit. This sadly cannot be fixed in yabridge. Simply unset WINEESYNC while using yabridge if this is an issue.
• Most recent iZotope plugins don't have a functional GUI in a typical out of the box Wine setup because of missing dependencies. Please let me know if you know which dependencies are needed for these plugins to render correctly.

There are also some VST2.X extension features that have not been implemented yet because I haven't needed them myself. Let me know if you need any of these features for a certain plugin or VST host:

• Double precision audio (processDoubleReplacing).
• Vendor specific extension (for instance, for REAPER, though most of these extension functions will work out of the box without any modifications).

Building

To compile yabridge, you'll need Meson and the following dependencies:

• gcc (tested using GCC 9.2)
• A Wine installation with wiengcc and the development headers.
• Boost
• xcb

The following dependencies are included in the repository as a Meson wrap:

• bitsery

The project can then be compiled as follows:

meson setup --buildtype=release --cross-file cross-wine.conf build
ninja -C build

32-bit bitbridge

It is also possible to compile a host application for yabridge that's compatible with 32-bit plugins such as old SynthEdit plugins. This will allow yabridge to act as a bitbirdge, allowing you to run old 32-bit only Windows VST2 plugins in a modern 64-bit Linux VST host. For this you'll need to have installed the 32 bit versions of the Boost and XCB libraries. This can then be set up as follows:

# Enable the bitbridge on an existing build
meson configure build -Duse-bitbridge=true
# Or configure a new build from scratch
meson setup --buildtype=release --cross-file cross-wine.conf -Duse-bitbridge=true build

ninja -C build

This will produce two files called yabridge-host-32.exe and yabridge-host-32.exe.so. Yabridge will detect whether the plugin you're trying to load is 32-bit or 64-bit, and will run either yabridge-host.exe or yabridge-host-32.exe accordingly.

Debugging

Wine's error messages and warning are usually very helpful whenever a plugin doesn't work right away. Sadly this information is not always available. Bitwig, for instance, hides a plugin's STDOUT and STDERR streams from you. To make it easier to debug malfunctioning plugins, yabridge offers these two environment variables:

• YABRIDGE_DEBUG_FILE=<path> allows you to write the Wine VST host's STDOUT and STDERR messages to a file. For instance, you could launch your DAW with env YABRIDGE_DEBUG_FILE=/tmp/yabridge.log <daw>, and then use tail -F /tmp/yabridge.log to keep track of that file. If this option is not present then yabridge will write all of its debug messages to STDERR instead.

• YABRIDGE_DEBUG_LEVEL={0,1,2} allows you to set the verbosity of the debug information. Each level increases the amount of debug information printed:

  • A value of 0 (the default) means that yabridge will only write messages from the Wine process and some basic information such about the plugin being loaded and the Wine prefix being used.
  • A value of 1 will log information about most events and function calls sent between the VST host and the plugin. This filters out some noisy events such as effEditIdle() and audioMasterGetTime() since those are sent tens of times per second by for every plugin.
  • A value of 2 will cause all of the events to be logged, including the events mentioned above. This is very verbose but it can be crucial for debugging plugin-specific problems.

  More detailed information about these debug levels can be found in src/common/logging.h.

Wine's own logging facilities can also be very helpful when diagnosing problems. In particular the +message and +relay channels are very useful to trace the execution path within loaded VST plugin itself.

Attaching a debugger

When needed, I found the easiest way to debug the plugin to be to load it in an instance of Carla with gdb attached:

env YABRIDGE_DEBUG_FILE=/tmp/yabridge.log YABRIDGE_DEBUG_LEVEL=2 carla --gdb

Doing the same thing for the Wine VST host can be a bit tricky. You'll need to launch winedbg in a seperate detached terminal emulator so it doesn't terminate together with the plugin, and winedbg can be a bit picky about the arguments it accepts. I've already set this up behind a feature flag for use in KDE Plasma. Other desktop environments and window managers will require some slight modifications in src/plugin/host-bridge.cpp. To enable this, simply run:

meson configure build --buildtype=debug -Duse-winedbg=true

Architecture

The project consists of two components: a Linux native VST plugin (libyabridge.so) and a VST host that runs under Wine (yabridge-host.exe/yabridge-host.exe.so, and yabridge-host-32.exe/yabridge-host-32.exe.so if the bitbirdge is enabled). I'll refer to the copy of or lthe symlink to libyabridge.so as the plugin, the native Linux VST host that's hosting the plugin as the native VST host, the Wine VST host application that's hosting a Windows .dll file as the Wine VST host, and the Windows VST plugin that's being loaded in the Wine VST host as the Windows VST plugin. The whole process works as follows:

1. Some copy of or a symlink to libyabridge.so gets loaded as a VST plugin in a Linux VST host. This file should have been renamed to match a Windows VST plugin .dll file in the same directory. For instance, if there's a Serum_x64.dll file you'd like to bridge, then there should be a symlink to libyabridge.so named Serum_x64.so.

2. The plugin first attempts to locate and determine:

   • The Windows VST plugin .dll file that should be loaded.

   • The architecture of that VST plugin file. This is done by inspecting the headers if the .dll file.

   • The location of the Wine VST host. This will depend on the architecture detected for the plugin. If the plugin was copmiled for the x86_64 architecture or the 'Any CPU' target, then we will look for yabridge-host.exe. If the plugin was copmiled for the x86 architecture, when we'll search for yabridge-host-32.exe.

     We will first search for this file alongside the actual location of libyabridge.so. This is useful for development, as it allows you to use a symlink to libyabridge.so directly from the build directory causing yabridge to automatically pick up the right version of the Wine VST host. If this file cannot be found, then it will fall back to searching through the search path.

   • The Wine prefix the plugin is located in. If the WINEPREFIX environment variable is specified, then that will be used instead.

3. The plugin then sets up a Unix domain socket endpoint to communicate with the Wine VST host somewhere in a temporary directory and starts listening on it. I chose to communicate over Unix domain sockets rather than using shared memory directly because this way you get low latency communication with without any busy waits or manual synchronisation for free. The added benefit is that it also makes it possible to send arbitrarily large chunks of data without having to split it up first. This is useful for transmitting audio and preset data which may have any arbitrary size.

4. The plugin launches the Wine VST host in the detected wine prefix, passing the name of the .dll file it should be loading and the path to the Unix domain socket that was just created as its arguments.

5. Communication gets set up using multiple sockets over the end point created previously. This allows us to easily handle multiple data streams from different threads using blocking read operations for synchronization. Doing this greatly simplifies the way communication works without compromising on latency. The following types of events each get their own socket:

   • Calls from the native VST host to the plugin's dispatcher() function. These get forwarded to the Windows VST plugin through the Wine VST host.

   • Calls from the native VST host to the plugin's dispatcher() function with the effProcessEvents opcode. These also get forwarded to the Windows VST plugin through the Wine VST host. This has to be handled separately from all other events because of limitations of the Win32 API. Without doing this the plugin would not be able to receive any MIDI events while the GUI is being resized or a dropdown menu or message box is shown.

   • Host callback calls from the Windows VST plugin through the audioMasterCallback function. These get forwarded to the native VST host through the plugin.

     Both the dispatcher() and audioMasterCallback() functions are handled in the same way, with some minor variations on how payload data gets serialized depending on the opcode of the event being sent. See the section below this for more details on this procedure.

   • Calls from the native VST host to the plugin's getParameter() and setParameter() functions. Both functions get forwarded to the Windows VST plugin through the Wine VST host using a single socket because they're very similar and don't need any complicated behaviour.

   • Calls from the native VST host to the plugin's processReplacing() function. This function gets forwarded to the Windows VST plugin through the Wine VST. In the rare event that the plugin does not support processReplacing() and only supports The deprecated commutative process() function, then the Wine VST host will emulate the behavior of processReplacing() instead.

   • The Windows VST plugin's AEffect object. A copy of this is sent over a socket from the Wine VST hsot to the plugin after the Windows VST plugin has finished initializing. Whenever this struct gets updated by the Windows VST plugin, the Windows VST plugin will call the audioMasterIOChanged() host callback and we'll repeat the process.

   The operations described above involving the host -> plugin dispatcher()and plugin -> host audioMaster() functions are all handled by first serializing the function parameters and any payload data into a binary format so they can be sent over a socket. The objects used for encoding both the requests and the responses for theses events can be found in src/common/serialization.h, and the functions that actually read and write these objects over the sockets are located in src/common/communication.h. The actual binary serialization is handled using bitsery.

   Actually sending and receiving the events happens in the send_event() and receive_event() functions. When calling either dispatch() or audioMaster(), the caller will oftentimes either pass along some kind of data structure through the void pointer function argument, or they expect the function's return value to be a pointer to some kind of struct provided by the plugin or host. The behaviour for reading from and writing into these void pointers and returning pointers to objects when needed is encapsulated in the DispatchDataConverter and HostCallbackDataCovnerter classes for the dispatcher() and audioMaster() functions respectively. For operations involving the plugin editor there is also some extra glue in PluginBridge::dispatch_wrapper. On the receiving end of the function calls, the passthrough_event() function calls the callback functions and handles the marshalling between our data types created by the *DataConverter classes and the VST API's different pointer types. This behaviour is separated from receive_event() so we can handle MIDI events separately. This is needed because a select few plugins only store pointers to the received events rather than copies of the objects. Because of this, the received event data must live at least until the next audio buffer gets processed so it needs to be stored temporarily.

6. The Wine VST host loads the Windows VST plugin and starts forwarding messages over the sockets described above.

7. After the Windows VST plugin has started loading we will forward all values from the plugin's AEffect struct to the Linux native VST plugin using the socket described above. After this point the plugin will stop blocking and has finished loading.