﻿id	summary	reporter	owner	description	type	status	component	version	resolution	keywords	cc	guest	host
20171	macOS host duplex CoreAudio devices are broken => fixed in SVN/next maintenance	csnover		"!VirtualBox will not use an audio device in a macOS host if it is a duplex (both input and output) device.

Such devices did work in !VirtualBox 5.0.40; I did not determine the specific version where this broke (I upgraded from 5.0 to 6.1).

Reproduction:

1. Create a duplex device (see below)
2. Set the duplex audio device as the default output (and/or input) device in macOS System Preferences
3. Run a VM

Expected: !VirtualBox plays/records audio through the duplex device.

Actual: !VirtualBox will not play/record audio. VBox.log says “CoreAudio: No default playback device found” (for output) or “CoreAudio: No default capturing device found” (for input). The DEFAULT flag on the device also isn’t set unless it is set as the system default for both output *and* input (though it still won’t work even then).

Workaround: For output only, Audio MIDI Setup.app can be used to create a “Multi-Output Device” which forwards to the outputs of the duplex audio device. This is not a good workaround, though, since this disables volume control.

To create a duplex device, you can either install one (e.g. [http://www.kuwatec.co.jp/synvisum/download/kuwatecAudioLoopback.pkg.zip kuwatec Audio Loopback], [https://github.com/mattingalls/Soundflower/releases/tag/2.0b2 Soundflower], or [https://apps.apple.com/us/app/boom2-volume-boost-equalizer/id948176063?mt=12 Boom2]), or construct an Aggregate Device following these steps:

1. Open /Applications/Utilities/Audio MIDI Setup.app
2. Click the plus icon in the bottom-left corner and choose “Create Aggregate Device”
3. Select the Aggregate Device from the menu on the left
4. Tick the “Use” box next to a device with a non-zero “In” column (e.g. “Built-in Microphone”)
5. Tick the “Use” box next to a device with a non-zero “Out” column (e.g. “Built-in Output”)

There are at least a couple of forum posts about this problem which contain appropriate logs:

https://forums.virtualbox.org/viewtopic.php?f=2&t=92570&p=445771&hilit=duplex#p445906 [[br]]
https://forums.virtualbox.org/viewtopic.php?f=8&t=96119&p=466346&hilit=coreaudio#p466346

The relevant section of my own VBox.log is:

{{{
00:00:04.472027 Audio: Initializing Core Audio driver
00:00:04.533481 CoreAudio: Default capturing device is 'USB Advanced Audio Device'
00:00:04.533688 CoreAudio: No default playback device found
00:00:04.533718 Audio: Host driver 'CoreAudio' supports 2 input streams and 2 output streams at once
00:00:04.536723 CoreAudio: Default capturing device is 'USB Advanced Audio Device'
00:00:04.536912 CoreAudio: No default playback device found
00:00:04.536934 Audio: Found 5 devices for driver 'CoreAudio'
00:00:04.536947 Audio: Device 'Built-in Microphone':
00:00:04.536955 Audio: 	Usage           = Input
00:00:04.536963 Audio: 	Flags           = NONE
00:00:04.536970 Audio: 	Input channels  = 2
00:00:04.536978 Audio: 	Output channels = 0
00:00:04.536986 Audio: Device 'USB Advanced Audio Device':
00:00:04.536993 Audio: 	Usage           = Input
00:00:04.537000 Audio: 	Flags           = DEFAULT
00:00:04.537008 Audio: 	Input channels  = 2
00:00:04.537015 Audio: 	Output channels = 0
00:00:04.537023 Audio: Device 'kuwatec Audio Loopback':
00:00:04.537031 Audio: 	Usage           = Duplex
00:00:04.537038 Audio: 	Flags           = NONE
00:00:04.537045 Audio: 	Input channels  = 2
00:00:04.537052 Audio: 	Output channels = 2
00:00:04.537060 Audio: Device 'Built-in Output':
00:00:04.537067 Audio: 	Usage           = Output
00:00:04.537075 Audio: 	Flags           = NONE
00:00:04.537082 Audio: 	Input channels  = 0
00:00:04.537090 Audio: 	Output channels = 2
00:00:04.537097 Audio: Device 'USB Advanced Audio Device':
00:00:04.537105 Audio: 	Usage           = Output
00:00:04.537112 Audio: 	Flags           = NONE
00:00:04.537119 Audio: 	Input channels  = 0
00:00:04.537127 Audio: 	Output channels = 2
}}}

Version: at least 6.1.16 & 6.1.18[[br]]
Host OS: at least macOS 10.14.6 (18G8012)[[br]]
Guest OS: All (tested Windows 7 32-bit)"	defect	closed	audio	VirtualBox 6.1.18	fixed			all	Mac OS X
