Enable OHCI and UHCI support and V4L2 support in kernel. Don’t enable v4l compatibility layer because it causes problems with emerging linux-uvc.
Mic requires USB audio support in kernel.
linux-uvc not needed, because cam supported by in-kernel drivers.
Emerge guvcview for graphical webcam viewer (which is masked for amd64).
Add users to video group.
Cam device should be /dev/video (or /dev/video0) -> /dev/v4l/video0.
Microphone
Need USB audio built in kernel. Device drivers -> Sound -> USB support -> USB sound/midi or similar. This should result in detection of a new device ‘#1: USB Device 0x46d:0x992’ controlled via /dev/mixer1.
Skype can use mic on webcam and can mute it, but not control volume.
mixers
xfce4-mixer allows choice of mixer from File -> Options, shows all controls and can be used in the xfce4-panel.
aumix -d /dev/mixer1 -I & will show controls for USB mixer (/dev/mixer is soundcard), but unfortunately doesn’t show all controls when on /dev/mixer.
gnome-alsamixer includes controls for all mixers, but it’s too large a window for my tastes.
Minor problem
Volume control keeps auto reverting to 100% on reboot.