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> Carla Plugin Host v2.4.0 is here
On 2021-08-20 by falkTX

Hello everyone, this is the announcement of the 2.4.0 version of the Carla Plugin Host.
If you do not know, Carla is a fully-featured cross-platform audio plugin host, which can also run as a plugin.

This release was initially meant to be 2.3.3 but there are some small new features so treating it as bugfix would be misleading.
Semantically-speaking, new stuff means new version, so 2.4 it is.
I was going to wait a bit more until a release, but it is Ubuntu feature freeze time, so got to go with what is available now in order to make it.
Anyway, let's go through the (small) release highlights.


Option to use classic skin by default

Who doesn't like a little bit of nostalgia?
Reminiscent of its v1.x days, the "classic" rack skin can now be made into the default.
So now you can be on latest Carla with all the new stuff, but still feel retro. :D

The dry/wet and volume controls are only accessible through the built-in plugin edit dialog,
but in return the whole rack takes less screen space.


LV2 Gtk UIs on any system

After some changes on how Carla handles its Gtk UI bridges, it is now possible to build and use them on any system.
Behind the scenes instead of directly linking against Gtk libraries, the Carla Gtk UI bridge will open the Gtk library/DLL to find the needed symbols in order to get a working Gtk setup.
This doesn't change the behaviour on Linux, but allows to use Gtk-based UIs on systems like Windows and macOS.
Its usefulness is a bit questionable, my main reason to change this was to be able to adapt to new Gtk versions more easily, but it has nice side effects.

Currently there are no LV2 plugins released on macOS or Windows that make use of such a UI, but could change soon via PawPaw.
I have been doing some tests and at least amsynth and Invada are possible to get working with their full UIs.
Later on I will see if and how it could be possible to package such plugins with their UIs.

Full changelog

  • Add option to use classic skin by default
  • Add support for lv2 ui gtk bridges on any system
  • Set display scale factor for carla-bridge-*/carla-single standalone usage (on macOS and X11 systems)
  • Fix Linux VST3 plugin GUIs crash on close
  • Fix build under msys2 (will not force static binaries)
  • Fix keyboard focus for bridges on macOS (2nd attempt)
  • Fix canvas icon in settings to be high-dpi compatible
  • Fix wrong scale factor of plugin GUIs under macOS


To download Carla binaries or source code, jump on over to the KXStudio downloads section.
If you're using the KXStudio repositories, you can simply install "carla".
Bug reports and feature requests are welcome! Jump on over to the Carla's Github project page for those.

Notes for users

This was already the case for v2.2 and v2.3 but it is worth reiterating:
When using JACK2, the canvas - plugin integrations requires at least JACK2 v1.9.13.
This is because Carla relies on JACK meta-data in order to store information about each plugin/client, and meta-data was only added to JACK2 in version 1.9.13.
Alternatively, you can use JACK1 instead of JACK2, which has meta-data support since a long time.
Note that the "extras" KXStudio repository (which provides an updated JACK2) supports both Ubuntu 18.04 and 20.04.
The UbuntuStudio backports PPA also provides updated JACK2 packages.

There are no official Linux binary builds for v2.4 at this point.
Carla v2.4 is provided in the KXStudio repositories and in many official Linux distribution repositories too anyway.


As always, if you appreciate the kind of work I do, please consider a donation.
Thank you in advance for your support, and stay safe out there!