Gain: A term used for amplification of an electronic signal. Also stands for amplitude or volume. In projection systems, the ability of a screen to amplify incident light. In cameras, the ability to amplify the input signal to obtain pictures in low-light conditions.
Gamma: The transfer characteristic of light input to light output of the television system. Many components in the television system introduce unequal light response and must be corrected.
Gbps: Gigabits per second: Billion bits per second
Gen-Lock: Circuitry that synchronizes the television signal source of two or more devices. All video signals contain synchronization pulses that are used to reconstruct the picture on the CRT. When several signals are used together through a common device such as a switcher, they all must be operating on the same sync. A master sync generator provides gen-lock to signal generating devices (cameras, VTRs, switchers, etc.) so that they can operate in sync.
General Purpose Interface: (GPI) 1.) A communications port that controls "triggering" with frame-accuracy. Typically used with devices that do not have serial control capability. On an editing system, the GPI port typically sends trigger pulses to peripheral devices. On devices such as switchers and digital effects, the GPI port typically receives triggers from the editor.
2.) A pulse or contact (switch) closure signal sent from an editor to trigger audio tape recorders, digital video effects devices, and graphics generators to activate for an edit or effect. Some external devices do not have the ability to be directly controlled by the editor. In this case GPI signal is used as a means of telling these devices when to execute a command. The choice of command itself, however, must be set up on the external device and cannot be controlled by the editor.
Generation: This refers to the number of times the original master videotape is copied. For example, the videotape used by the VTR during the actual shooting is a first generation tape. The edited master made from those original tapes would be second generation.
Generational Loss: The decreasing signal-to-noise ratio resulting when one analog recording is copied to another.
Geostationary Orbit: An orbital location of a communications satellite fixed above the earth's equator at 22,300 miles out. The satellite's position is constant relative to a point on the earth.
Ghosting: A phenomenon primarily visible in tube-type imagers where a ghost of an image remains in the scene when the camera or subject moves. Most observable as a result of bright light sources on dark backgrounds, ghosting or lag has been almost entirely eliminated by CCD imagers.
GHz: GigaHertz. One billion cycles per second.
GPI: See "General Purpose Interface".
Grand Alliance: Agreement among ATV proponent systems to develop a unified ATV transmission system for North America
Graphics: 1.) Computer term: Text or pictorial artwork created on the computer with software and stored on a hard disk for use in computer-based presentations, desktop publishing, or video applications.
2.) Video term: Text and Graphics created primarily by specialized electronic character generators and graphics systems and used in videotape applications. Personal computers equipped with special video output cards are capable of producing graphics for video production.
Graphics Capability: Some codecs offer a graphics transmission capability that permits the transmission of still-frame images at higher resolution than the motion channel. This feature is used in conjunction with a graphics camera and stand, scanner, or Mavica¨.
Gray scale: An even range of gray tones between black and white.
Ground: A large conducting body (as the earth) used as a common return for an electric circuit and as a zero potential (voltage). Earth ground is a conductor connection to the earth (a conductor actually driven into the ground) giving a common potential for circuits. Equipment is often grounded for safety factors to prevent accidental electrocution.
GSM: Groupe speciale mobile; global standard for mobile communications
GUI :Graphic User Interface A computer software system that relies on menus, icons, and pointing devices (mouse) for user interaction. The foundation for the Macintosh personal computer and IBM PCs operating with Microsoft Windows 3.0.