Audio Units (AU) are a system-levelplug-in architecture provided byCore Audio inApple'smacOS andiOS operating systems. Audio Units are a set ofapplication programming interface (API) services provided by theoperating system to generate, process, receive, or otherwise manipulate streams of audio in near-real-time with minimal latency. It may be thought of as Apple's architectural equivalent to another popular plug-in format,Steinberg'sVirtual Studio Technology (VST).
Because of the many similarities between Audio Units and VST, several commercial and free wrapping technologies are available (e.g.Symbiosis andFXpansionVST-AU Adapter).Celemony Software andPreSonus have also developed theAudio Random Access (ARA) extension, which works for both AU andVST, allowing greater integration between theplug-ins andDAW software.[1]
Audio Units allows sound fileaudio time stretching and pitch scaling (e.g., timestretch),sample rate conversion, and streaming over alocal area network. It also comes with a set of AU plug-ins such as EQ filters, dynamic processors, delay, reverb, and a Soundbank Synthesizer Instrument.
AU are used by Apple applications such asGarageBand,Soundtrack Pro,Logic Express,Logic Pro,Logic Pro X,Final Cut Pro,MainStage and most 3rd party audio software developed formacOS such asAbleton Live, Amadeus Pro,Ardour,Audio Hijack,DaVinci Resolve,Digital Performer,Gig Performer,REAPER, andStudio One.
