Technical Q&A QA1408

Audio Units - How to determine the version of an Audio Unit

Q: How do I determine the version of an Audio Unit I am using?

A: Core Audio uses the Audio Component API to make Audio Units available as a system-wide resource. After obtaining a valid instance of an Audio Unit, you can use AudioComponentGetVersion to get the version number.

This can be useful when you require a specific version of an Audio Unit with updated or different features and you want to determine which version is installed before using the Audio Unit.

Listing 1 demonstrates how to ensure you have at least version 2.0 of the 3D Mixer audio unit installed.

Listing 1 Checking the 3D Mixer Version.

// The Version format is 0xMMMMmmbb

// The digits M/m/b are stored in BCD (Binary Coded Decimal) format for numbers greater than 9

// A version number for 10.3.1 would be: 0x100301

// A version number for 2.3.1 would be: 0x20301

#define kPreferredMixerVersion  0x20400

#define kMinimumMixerVersion    0x20000

...

    // if the returned version is less than 0x20000

    // it's not the 3DMixer we're looking for, move along...

    UInt32 mixerVersion = kMinimumMixerVersion;

    if ( Is3DMixerVersionValid(&mixerVersion) ) {

        // yes, we can work with it

        // your code here...

        printf("Version Number Returned 0x%x", (unsigned int)mixerVersion);

...

bool Is3DMixerVersionValid(UInt32 *ioVersionNumber)

    bool isVersionValid = false;

    UInt32 theVersionNumber = 0;

    if (NULL == ioVersionNumber) return false;

    AudioComponentDescription mixer3D_desc = { kAudioUnitType_Mixer,

                                               kAudioUnitSubType_3DMixer,

                                               kAudioUnitManufacturer_Apple,

                                               0, 0 };

    AudioComponent mixer3D_component = AudioComponentFindNext(0, &mixer3D_desc);

    if (NULL == mixer3D_component) return false;

    if (AudioComponentGetVersion(mixer3D_component, &theVersionNumber)) return false;

    if (theVersionNumber >= *ioVersionNumber){

        isVersionValid = true;

        *ioVersionNumber = theVersionNumber; // validated this pointer on entry

    return isVersionValid;

See AudioComponent.h for more information.

Document Revision History

Date	Notes
2013-07-30	Updated to use Audio Component API. Updated description of version format & added examples.
2005-03-07	Changed code of Is3DMixerVersionValid(). Added information about Version format (BCD).
2005-02-03	New document that demonstrates how to find the version number of an Audio Unit.