I recently installed a new Debian guest on a FreeBSD host with VirtualBox. On this VM I need to be able to play/record sound from my laptop (Skype). To do so I configure the guest with an Intel HDA soundcard using the OSS audio driver. However I want to use the internal mic (/dev/dsp1.0) which is different than the default unit (/dev/dsp). So I had basically two options. Either I could record my voice but could not hear anything or I could hear everything but could not record my voice.

But there is a solution! I digged in the VirtualBox source code, and there are actually some options for the OSS driver (and other audio drivers as well). The two options of interests are:

• DACDev: Path to the DAC (output/playback) device.
• ADCDev: Path to the ADC (input/record) device.

You can use VBoxManage to configure these options. Assuming that the name of the VM is MyVM with an Intel HDA card and the OSS driver, use this command:

$ VBoxManage setextradata MyVM "VBoxInternal/Devices/hda/0/LUN#0/Config/Audio/OSS/ADCDev" /dev/dsp1.0

You can also directly edit the vbox file for this VM:

MyVM.vbox:

<ExtraData>
  ...
  <ExtraDataItem name="VBoxInternal/Devices/hda/0/LUN#0/Config/Audio/OSS/ADCDev" value="/dev/dsp1.0"/>
</ExtraData>

Note if when starting the VM you receive the message The attached driver configuration is missing the 'Driver' attribute (VERR_PDM_CFG_MISSING_DRIVER_NAME). This is probably because the sound device you selected for this VM is not the same as specified in the extra data. The above example is for Intel HD Audio (hda). If you need ICH AC97, replace hda by ichac97 in the example above.