However, OSS audio simply fails. No input, no output when guest is booted with this option. Furthermore, this is the only host program that cannot use OSS properly. VLC, mpv, and other multimedia apps work fine when switched to OSS audio.
Attached is a log with audio debug enabled, showing VBox unable to open an OSS stream. Currently using a USB Audio headset (usb_ac/usb_as), this even works fine in a native port of Mumble.
00:00:59.945593 Audio: Requested host recording format for '[OSSAudio] Mic-In': 48000Hz, 16S, 2 Channels 00:00:59.945641 Audio: Using default period size (50ms, 2400 frames) for stream '[OSSAudio] Mic-In' 00:00:59.945653 Audio: Using default buffer size (250ms, 12000 frames) for stream '[OSSAudio] Mic-In' 00:00:59.945664 Audio: Using default pre-buffering size (250ms, 12000 frames) for stream '[OSSAudio] Mic-In' 00:00:59.955550 Audio: Stream '[OSSAudio] Mic-In' could not be created in backend because of missing hardware / drivers 00:01:00.284117 AC97: Setting Front DAC rate when VRA is not set is forbidden, ignoring