1. USB cameras 4 distinct USB camera functions GPhoto2 vs Video4Linux2
Still camera that downloads to the PC
Video clip camera that downloads to the PC
Computer controlled still camera
Computer controlled video webcam
GPhoto2 vs Video4Linux2
Two entirely different, mutually exclusive ways to talk to a USB camera

2. GPhoto2 Gphoto2 has 3 out of 4 functions
Still camera that downloads to the PC
Video clip camera that downloads to the PC
PC controlled still camera
USB protocol for GPhoto2 is contained in a user-level library called libgphoto2
Basically, gphoto2 is a command line interface for libgphoto2
Libgphoto2 uses libusb to do low level USB work

3. GPhoto2 command line interface
Auto-detection
gphoto2 --auto-detect
Shows you if you camera is recognized by gphoto2
List the context of camera
gphoto2 –get-list-files
Get files from you camera
gphoto2 –get-all-files

4. GPhoto2 capture capability
Defining Your Camera's Abilities
gphoto2 -a
Capturing 20 frames with an interval of 60 sec.
gphoto2 --capture-image --interval 60 –frames 20
Not all the camera support this feature
A list of cameras that support capture

5. Cannon Capture
Capture is a tool for periodic image capturing with digital Canon cameras
The consecutive shots are taken without the camera lenses being closed and opened again
Supposedly increases camera live

6. Libusb API External API for applications to use Core functions
usb_init()‏
Initialize libusb
usb_find_busses()
Finds all USB busses on system
usb_find_devices()‏
Find all devices on all USB devices
usb_get_busses()
Return the list of USB busses found

7. Libusb API Device operation functions Control transfer functions
Bulk transfer functions
Interrupt transfer functions
No portable functions