CoreAudio: What is "AudioBox" as contrasted to "AudioDevice"

Question

The header file CoreAudio/AudioHardware.h refers to a class "AudioBox" and indicates that it is distinct from but related to the class "AudioDevice". Searching developer.apple.com yields no hits for AudioBox. There is, unfortunately, a commercial product called AudioBox™, which makes googling for the term painfully low-yield.

Here are the comments containing the references:

kAudioHardwarePropertyBoxList

An array of AudioObjectIDs that represent all the AudioBox objects currently provided by the system.

kAudioHardwarePropertyTranslateUIDToBox

This property fetches the AudioObjectID that corresponds to the AudioBox that has the given UID. The UID is passed in via the qualifier as a CFString while the AudioObjectID for the AudioBox is returned to the caller as the property's data. Note that an error is not returned if the UID doesn't refer to any AudioBoxes. Rather, this property will return kAudioObjectUnknown as the value of the property.

The header file: AudioHardwareBase.h contains numerous references to AudioBox, but does not define or explain it, although it associates it with AudioDevice.

Searching the docs via XCode just takes me back to AudioHardwareBase.h.

I can infer that perhaps an "AudioBox" is an audio device that is accessed via a plugin. But this does not appear to be stated anywhere.

So What Is An AudioBox?

Answer 1

An AudioBox is a container of (usually) AudioDevices