AUv3 Extensions User Presets.md

AUv3 Extensions User Presets

@ WWDC 19

Presets

• Provide a fine-tuned set of parameteer values
• Capture a snapshot of the state of the Audiio Unit's parameters
• Loading a preset restores the Audio Unit to the same state

User Presets for Audio Unit Extensions

• We already support factory presets

  open var factoryPresets: [AudioUnitPreset]? { get }

• Provided by the Audio Unit Developer

• Immutable, built into the Audio Unit

User Presets for Audio Unit Extensions

open var userPresets: [AUAudioUnitPreset]? { get }

• Created and managed by the user

• Mutable

New API

open var supportsUserPresets: Bool { get }

• Set by the Audio Unit to opt-in
• Checked by the host to verify support

open func saveUserPreset(_ userPreset: AUAudioUnitPreset) throws
open func deleteUserPreset(_ userPreset: AUAudioUnitPreset) throws

• Have default implementations in AUAudioUnit
• Can be overriden to implement custom logic

open func presetState(foor userPreset: AUAudioUnitPreset) throws -> [Striing : Any]

• Implemented in the superclass, but can be overriden
• Returns the contents of a user preset
• Can be assigned to fullStateForDocument

open var isLoadedInProcess: Bool { get }

• Returns true if the audio unit is loaded in-process
• Loading in process is only available on macOS

Summary

• We now support user presets for Audio Units in addition to factoryPresets
• The Audio Unit has to opt in
• The methods have default implementations in the super class, but can be overriden