A Max OS X CoreAudio enhancement note

[Gregory Palmer]

For current Mac OS X hosts, if the user has configured and selected for default audio usage an external speaker system, such as the USB-interfaced Bose Companion 5 system, in place of the Mac's internal speakers, VirtualBox consistently fails to communicate with the CoreAudio system of the host OS during pre-boot operations resulting in solid error selection of the NULL audio driver and leaving the guest mute (vbox.log provided in evidence for driver case IHC AC97 - host is MAC OS X 10.6.2).

This behavior holds for both selections of audio driver - IHC AC97 or Soundblaster. A work around is to simply access the Audio configuration in System Tools to reestablish the internal speakers for the period of time during which VirtualBox hosts its guest(s).

I would like to suggest that there might be a better way to provide audio for guests running under VirtualBox for OSX - provide two additional Controller choices that avoid virtualization of sound cards altogether and simply provide the audio information directly to CoreAudio per the user's specification in System Tools::Audio and its companion Audio MIDI Setup application in the Utilities folder.

In doing this, you would allow the user to configure a choice of audio output, conducted by CoreAudio, in either of two ways:

a) to the CoreAudio Default Output unit (kAudioUnitSubType_DefaultOutput) is for whatever is 'standard' audio out, such as a user-configured external audio system

b) to the CoreAudio System Output unit (kAudioUnitSubType_SystemOutput) which is normally used for alerts and user interface sound effects.

I believe that this would provide the user with maximum flexibility and minimal configuration error.

[Gregory Palmer]

File illustrating CoreAudio failure - external audio system in usage