14. Advanced Topics

14.1. Adding support for your MIDI/HID Controller

With several dozens of DJ controllers supported out-of-the-box, Mixxx gives you comprehensive hardware control for your DJ mixes, see Using MIDI/HID Controllers.

Support for additional devices can be added to Mixxx by creating a new preset file. This file tells Mixxx how to translate, or map, MIDI/HID messages from a controller into commands that Mixxx understands.

You can download and share custom controller presets in the Mixxx User customizations forums.

14.1.1. Controller Wizard

Mixxx Controller Wizard - Mapping a control

By far, the easiest way to create a new MIDI preset is by using the Controller Wizard.

Connect your controller(s) to your computer
Start Mixxx
Go to Preferences ‣ Controllers
Select your device from the list of available devices on the left, and the right pane will change
Activate the Enabled checkbox
Click on Learning Wizard to open the selection dialog
Click any control in the Mixxx GUI
Alternatively, click the Choose Control button and choose one from the selection list
Push Learn and then move a control or push a button on your controller to map it. You can also move a control without pushing the Learn button if you are learning many controls.
If you are learning a button, just push it once. If you are learning a knob or a slider, try to move it throughout its range.
After Mixxx detects the control, you may click Learn Another or you can click on another button in the Mixxx GUI to learn another control.
When you are finished mapping controls, click Done

There are also some advanced options in the Midi Wizard you may need to use:

Soft Takeover: Use this option for knobs or sliders to avoid sudden jumps in when the knob in the GUI doesn’t match the physical knob. If you select this option, you won’t be able to perform super-fast motions as easily. (Recommended off)
Invert: Use this option for controls that you want to work backwards from how they were detected.
Switch Mode: Use this option on controllers that have controls that act like switches and emit one value on the first press, and a different value on the next press. (Think an actual hardware toggle switch, or a button that lights up on the first press and turns off on the second press).
Jog Wheel / Select Knob: Use this for knobs that don’t have a beginning or an end, but spin continuously.

The Controller wizard saves the new preset to the following file paths:

Linux: /home/<username>/.mixxx/controllers
macOS: /Users/<username>/Library/Application\ Support/Mixxx/controllers
Windows: %LOCALAPPDATA%\Mixxx\controllers

You can then modify the XML file it creates (or any of the ones that ship with Mixxx) if you’d like to fine-tune it or add more presets. For more information, go to https://github.com/mixxxdj/mixxx/wiki/MIDI-Controller-Mapping-File-Format.

The Controller Wizard works only for MIDI devices. Currently you can’t map modifier (shift) keys and platter rotations. Use MIDI Scripting instead.

14.1.2. MIDI Scripting

In order to support the advanced features of many MIDI/HID controllers, Mixxx offers what we call MIDI Scripting.

It enables MIDI controls to be mapped to QtScript (aka Javascript/EMCAScript) functions stored in function library files, freeing Mixxx from a one-to-one MIDI mapping ideology. These user-created functions can then do anything desired with the MIDI event such as have a single controller button simultaneously affect two or more Mixxx properties (“controls”), adjust incoming control values to work better with Mixxx (scratching), display a complex LED sequence, or even send messages to text displays on the controller.

For more information, go to https://github.com/mixxxdj/mixxx/wiki/Midi-Scripting and https://github.com/mixxxdj/mixxx/wiki/hid_mapping_format.

14.2. Making a Custom Keyboard Mapping

The default keyboard mappings are defined in a text file which can be found at the following location:

Linux: /usr/local/share/mixxx/keyboard/en_US.kbd.cfg
macOS: /Applications/Mixxx.app/Contents/Resources/keyboard/en_US.kbd.cfg
Windows: <Mixxx installation directory>\keyboard\en_US.kbd.cfg

Depending on your system’s language settings, Mixxx might use a different file as default, e.g. de_DE.kbd.cfg for German or es_ES.kbd.cfg for Spanish.

It is not recommended that you modify the system-wide keyboard mapping file because all your changes may be lost if you uninstall or upgrade Mixxx. Instead, copy the default mapping file to the following location:

Linux: ~/.mixxx/Custom.kbd.cfg
macOS: ~/Library/Application\ Support/Mixxx/Custom.kbd.cfg
Windows: %LOCALAPPDATA%\Mixxx\Custom.kbd.cfg

Then edit this file and save the changes. On the next startup, Mixxx will check if Custom.kbd.cfg is present and load that file instead of the default mapping file. This has the advantage that you can always revert back to the default mapping by deleting Custom.kbd.cfg.

For a list of controls that can be used in a keyboard mapping, see https://github.com/mixxxdj/mixxx/wiki/mixxxcontrols.

You can download and share custom keyboard mappings in the Mixxx User customizations forums.

14.3. Additional Effects via external Mixer Mode

Mixxx comes with a set of native effects. Additionally, using the external mixer mode you can route each deck directly to 3rd party effect hosts.

The following examples are only intended to encourage experimentation, they are not definitive guidance.

14.3.1. Effects via AU Lab on macOS

The Au Lab routing for external effects on macOS

On macOS there is a simple and free way to give Mixxx access to the collection of AU/VST/MAS plugins that are installed on your system.

Install the free Soundflower, a system extension for inter-application audio routing.
Install the free digital audio mixing application AU Lab.

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macOS 10.15 (Catalina) introduces additional restrictions on running non-Apple software. Make sure to grant permission in System Preferences –> Security & Privacy –> Microphone –> AU Lab.

Alternatively, try Blackhole, a modern virtual audio driver that allows applications to pass audio to other applications with zero additional latency, and Hosting AU, a free micro-sized DAW that hosts Audio Unit instruments and effect plugins.

In Mixxx

Go to Preferences ‣ Sound Hardware‣ Output
Select for Deck 1 the Soundflower 16 device with Channel 1-2
Select for Deck 2 the Soundflower 16 device with Channel 3-4
Click the Apply button

In AU Lab

Click on the + button to create a new configuration
Add 2 stereo input tracks in the Audio Input Tab
Add 2 stereo output tracks in the Audio Output Tab
Click OK
Change the audio input device to Soundflower 16
Change the audio output device for example to Built-in Output
Click Create document
In the Output 1 channel, select an effect from the drop-down menu, for example Apple > AUCompressor

The effect should now react if you play a track in Mixxx.

14.3.2. Effects via JACK Rack on GNU/Linux

The Jack routing for external effects on GNU/Linux

Use Jack to route each deck directly through JACK Rack effect racks, or for more control you can use Ardour (or another DAW) using sends for effects. This gives Mixxx access to the extensive collection of LADSPA plugins.

Make sure the correct multichannel audio interface has been selected in Jack (Jack settings visible bottom left). Note that Mixxx possibly labels its Jack ports as Portaudio.

14.4. Deleting Your Library

The library file is stored in the following places depending on your operating system:

Windows

The Mixxx library is stored in the %USERPROFILE%\Local Settings\Application Data\Mixxx\ folder. To delete your library on Windows, delete the mixxxdb.sqlite file in this folder.

macOS

The Mixxx library is stored in the Library/Application Support/Mixxx folder in your home directory. To delete your library on macOS type the following command into a terminal:

rm ~/Library/Application\ Support/Mixxx/mixxxdb.sqlite

GNU/Linux

The Mixxx library is stored in the .mixxx folder in your home directory. To delete your library on GNU/Linux type the following command into a terminal:

rm ~/.mixxx/mixxxdb.sqlite

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Deleting your library will lose all of your metadata. This includes saved hotcues, loops, comments, ratings, and other library related metadata. Only delete your library if you are fine with losing these.