yabridge/README.md

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.

TODOs

Everything is implemented and ready for release after a few documentation updates:

• Add missing details if any to the architecture section.
• Add a screenshot, because why not?

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 "$HOME/.wine/drive_c/Program Files/Steinberg/VstPlugins" -type f -iname '*.dll' -print0 |
  xargs -0 -P8 -I{} bash -c "(winedump -j export '{}' | grep -qE 'VSTPluginMain|main|main_plugin') && printf '{}\0'" |
  sed -z 's/\.dll$/.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 "$HOME/.wine/drive_c/Program Files/Steinberg/VstPlugins" -type f -iname '*.dll' -print0 |
  xargs -0 -P8 -I{} bash -c "(winedump -j export '{}' | grep -qE 'VSTPluginMain|main|main_plugin') && printf '{}\0'" |
  sed -z 's/\.dll$/.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). I'll refer to a copy of or a 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 that's hosting a Windows .dll file as the Wine VST host, and the Windows VST plugin that's loaded in the Wine VST host is simply 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:

   • The location of yabridge-host.exe. For this it will first search for the file either alongside libyabridge.so. This is useful for development, as it allows you to use a symlink from the build directory to cause yabridge to use the yabridge-host.exe from that same build directory. If this file can't be found, then it will fall back to searching through the search path.
   • The wine prefix plugin is located in.
   • The corresponding Windows VST plugin .dll file.

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 use Unix domain sockets rather than shared memory 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 data without having to split it up into chunks first, which 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.

5. Communication gets set up using multiple sockets over the same end point. This allows us to use blocking read operations from multiple threads to handle multiple different events without the risk of receiving packets in the wrong order. The following types of events get assigned a socket:

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

   • Calls from the native VST host to the plugin's dispatch() function with opcode=effProcessEvents. These 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. Otherwise the plugin would not receive any MIDI events while the GUI is being resized or a dropdown menu or message box is open.

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

     Both the dispatch() 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.

   • 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 process() and processReplacing() functions. Both functions get forwarded to the Windows VST plugin through the Wine VST host using a single socket. The process() function has been deprecated, so a VST host will never call it if processReplacing() is supported by the plugin.

   • Updates of the Windows VST plugin's AEffect object. This object tells the host about the plugin's capabilities. A copy of this is sent over a socket from the Wine VST hsot to the plugin after it loads the Windows VST plugin so it can return a pointer to it to the native VST host. Whenever this struct updates, the Windows VST plugin will call the audioMasterIOChanged host callback and we'll repeat this process.

   The operations described above are all handled by first serializing the function parameters and any payload into an object before they can be sent over a socket. The objects used for encoding both the requests and and the responses for theses events can be found in src/common/communication.h along with functions that read and write these objects over streams and sockets. The actual binary serialization is handled using bitsery.

   Sending and receiving host -> plugin and plugin -> host events happen in the send_event() and receive_event() functions. Reading data and writing the results back for host-to-plugin dispatcher() calls and for plugin-to-host audioMaster() callbacks happen in the DispatchDataConverter and HostCallbackDataConverter classes respectively, with a bit of extra glue for GUI related operations in PluginBridge::dispatch_wrapper. On the receiving end, the passthrough_event() function calls the callback functions and handles the marshalling between our data types and the VST API's different pointer types. This behaviour is separated from receive_event() so we can some special handling for MIDI events, since a select few plugins only store pointers to the received events rather than copies of the objects. This requires the received event data to live at least until the next audio buffer gets processed.

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.