Audio unit
An audio unit ( AU ) is a plug-in in the core audio technology of Apple's macOS . Their task is to process sound material (as an effect) or to convert MIDI data into audio signals (as a software instrument). This process can take place in real time (with a time delay depending on the computational effort) or even faster with so-called offline computation.
The principle of the Audio Units is to collect all plugins in one place. Any program, the so-called host software, must support Core Audio in order to gain access to all plugins. The Audio Units replace Steinberg's VST interface under macOS and in particular the sequencer program Logic , which is no longer supported by Logic from version 6. In contrast to VSTs, AUs, as part of Core Audio, are platform-bound to macOS and do not run under other operating systems such as Windows or Linux , which also limits their distribution. The filename extension of the Audio Unit plugins is usually component .
Audio units can be developed by other manufacturers and additionally installed; some are already integrated in the operating system. Most manufacturers of software instruments and effects ported their VSTs after the new interface was announced and made AU and VST versions available. The "VST to Audio Unit Adapter" plug-in from FXPansion makes it possible to integrate VST plug-ins into an AU interface by acting as a plug-in for the AU host and as a host for the VST plug-in.
Another popular audio plug-in interface is Real Time AudioSuite , developed by Digidesign .