Technical Note TN2276

Audio Unit AUPlugIn - Updating an existing Audio Unit for OS X Lion and later

When updating audio units for Mac OS X Lion or later there are a number of changes that must be made to your Xcode project for the audio unit to build and run on the system. Once these changes are in place, the audio unit will build and run in Mac OS X Lion and also run when deployed in Mac OS X v10.6.x.

This technical note discusses these changes using the FilterDemo audio unit sample code project as an example.

Example: Updating the FilterDemo Audio Unit
Document Revision History


Mac OS X Lion introduces a new plug-in model called AUPlugIn which is no longer based on the Component Manager. The AUPlugIn model has a new dispatch mechanism requiring the inclusion of two new dispatch helper files called AUPlugInDispatch.h and AUPlugInDispatch.cpp respectively.

A new AUDIOCOMPONENT_ENTRY() macro has been added to ComponentBase.h and by using this macro audio unit entry points are created for both the audio unit plug-in for Mac OS X Lion and the Component Manager component for backwards compatibility with Mac OS X v10.6.x.

Because audio units no longer use the Component Manager on Mac OS X Lion or newer, AUPlugIn based audio units do not use resource files (.r files) or the 'thng' resource to define properties such as kComponentType, kComponentSubType, and kComponentManufactureType. These properties are now specified in the project's Info.plist file for the audio unit. You can continue to include the Component Manager resource file in the project for backwards compatibility with Mac OS X v10.6.x.

The new AUPlugIn entry point generated by the AUDIOCOMPONENT_ENTRY() macro is required and must be added to the exports file (.exp). You can leave the Component Manager entry point in the exports file to provide backwards compatibility with Mac OS X v10.6.x.

Example: Updating the FilterDemo Audio Unit

Download the FilterDemo Audio Unit sample and walk though the following update steps. Mac OS X Lion and the associated Xcode tools are required.

  1. Open the file Filter.cpp and replace COMPONENT_ENTRY(Filter) with AUDIOCOMPONENT_ENTRY(AUBaseFactory, Filter). This is the new macro that generates the plugin entry for the audio unit. See Listing 1.

  2. Add the new entry point called _FilterFactory to the Filter.exp file. _FilterFactory is generated by the AUDIOCOMPONENT_ENTRY() macro. Leave _FilterEntry for backwards compatibility. See Listing 2.

  3. Add an AudioComponents dictionary to the Info.plist file. Audio unit plugins do not use resource files to define their properties, therefore these items now need to be specified in the Info.plist file. Note that the resource file (Filter.r) should be left in place for backwards compatibility. See Listing 3 and Figure 1.

  4. Add the AUPlugInDispatch.h and AUPlugInDispatch.cpp files to the project. These dispatch helper files are located in Developer/Extras/CoreAudio/AUPublic/AUBase and are required by the AUPlugIn manager. See Figure 2.

Listing 1  Change entry point generation macro in Filter.cpp

//	Standard DSP AudioUnit implementation
// old component manager entry point no longer required
// new AUPlugIn macro

Listing 2  Add new entry point in Filter.exp


Listing 3  AudioComponents array in the Info.plist file.

<string>Filter AU</string>
<string>Apple Demo: Filter</string>
Figure 1  Graphical representation of AudioComponents array.
Figure 2  AUPlugInDispatch files added to Xcode project.

Document Revision History


Fixed plist information




Fixed plist information




New document that discusses required audio unit project changes for building and running on OS X Lion (and v10.6.x).