Hello. On my physical, host system, I have a discrete, modern PCI Express sound card which works only in High Definition Audio mode. When I use Whonix-Workstation VM (Virtualbox) and play sound or videos using VLC media player inside WS machine, I notice that sound is chopping. It means that sound is playing, then disappearing for ~0.5 seconds, then appearing again. I tested sound using VLC player on my host system and it plays good.
I’ve been trying to solve this problem for some time and I’ve found out that Whonix Workstation VM uses AC’97 virtual audio controller by default. I went to Virtualbox Whonix Workstation VM settings, then clicked on Audio tab, then switched the virtual audio controller from AC’97 to Intel HD Audio. Now sound works good without any interruptions.
I have a question to Whonix developers. Can the changing of virtual audio adapter lead to de-anonymization or not?
If not, can Whonix developers switch virtual audio adapter from AC’97 to Intel High Definition Audio by default in future Whonix releases? AC’97 specification is pretty old and not supported by modern hadrware nowadays and also can cause some problems with playing sounds. Also AC’97 sample rate is limited to 48kHz while Intel High Definition Audio can support up to 192kHz.
Thanks! This commit is significant. Most of modern (both built-in and discrete) sound cards have been using High Definition Audio (HDA) specification since 2004.
When Whonix-Workstation is set up to use ICH AC’97 virtual audio adapter in Virtualbox VM settings, then Linux kernel uses snd_intel8x0 driver which emulates the work of Intel 82801AA (ICH) I/O controller, which was released in 1999. This driver has no support for High Definition Audio.
When virtual audio adapter is changed to Intel HD Audio, then Linux kernel uses modern snd_hda_intel driver which emulates the work of 82801FBM (ICH6) I/O controller which was released in 2004. This driver has both High Definition Audio (HDA) and AC’97 support.
It means that the usage of an outdated AC’97 driver inside Whonix-Workstation is useless and may cause problems with sound because AC’97 and HDA specification has no backward compatibility.
As for host audio system, you can use both PulseAudio or ALSA for Whonix VirtualBox VM. The only thing you should know is that when you use ALSA for your VirtualBox VM directly, it means that there will be no sound on your other apps on host. If you use PulseAudio on your host, then all apps will have access to sound.