The capture support is designed for live video, it is not for passive digital cameras that only transfer the already taken pictures. Are valid: USB cameras (like most Webcams), Firewire (IEEE 1394) cameras, and analog video capture boards, including TV Tuners. These are called devices.
The capture functions allows you to:
You can list the installed devices and once you connect to a specific device you can control its parameters. Each connected device captures data frames continuously when in Live state otherwise it stays in standby. You can connect to more than one device at the same time.
Once connected the user can retrieve frames from the device any time. This can be done with one function call, or inside a closed loop for several frames, or inside an idle function to periodically update the screen. The user is not notified when a new frame is available, but every time the user retrieve a frame, if successful, it is a new frame, old frames are discarded when a new frame arrives.
Currently it is implemented only in Microsoft Windows.