Generalized Timing Formula is a standard by
VESA
VESA (), formally known as Video Electronics Standards Association, is an American technical standards organization for computer display standards. The organization was incorporated in California in July 1989To retrieve the information, searc ...
which defines exact parameters of the
component video signal for analogue
VGA
Video Graphics Array (VGA) is a video display controller and accompanying de facto graphics standard, first introduced with the IBM PS/2 line of computers in 1987, which became ubiquitous in the PC industry within three years. The term can no ...
display interface.
The video parameters defined by the standard include
horizontal blanking
Horizontal blanking interval refers to a part of the process of displaying images on a computer monitor or television screen via raster scanning. CRT screens display images by moving beams of electrons very quickly across the screen. Once the beam ...
(retrace) and
vertical blanking interval
In a raster scan display, the vertical blanking interval (VBI), also known as the vertical interval or VBLANK, is the time between the end of the final visible line of a frame or field and the beginning of the first visible line of the next fra ...
s,
horizontal frequency and
vertical frequency (collectively, pixel clock rate or video
signal bandwidth
Bandwidth is the difference between the upper and lower frequencies in a continuous band of frequencies. It is typically measured in hertz, and depending on context, may specifically refer to ''passband bandwidth'' or ''baseband bandwidth''. ...
), and
horizontal/
vertical sync
Analog television is the original television technology that uses analog signals to transmit video and audio. In an analog television broadcast, the brightness, colors and sound are represented by amplitude, phase and frequency of an analog s ...
polarity. Unlike predefined discrete modes (VESA DMT), any mode in a range can be produced using a formula by GTF.
A GTF-compliant display is expected to calculate the blanking intervals from the signal frequencies, producing a properly centered image. At the same time, a compliant graphics card is expected to use the calculation to produce a signal that will work on the display — either a GTF default formula for then-ordinary CRT displays or via a custom formula provided via EDID signaling.
These parameters are used by the
XFree86 Modeline : ''A mode line may also refer to a line for the Emacs and Vim editors that provides information about the file and modes.''
A modeline is a configuration line in xorg.conf or the XFree86 configuration file (XF86Config) that provides information ...
, for example.
This video timing standard is available for free.
History
The standard was adopted in 1999, and was superseded by the
Coordinated Video Timings Coordinated Video Timings (CVT; ''VESA-2013-3 v1.2'') is a standard by VESA which defines the timings of the component video signal. Initially intended for use by computer monitors and video cards, the standard made its way into consumer television ...
specification in 2002.
See also
; Similar standards
:
Coordinated Video Timings Coordinated Video Timings (CVT; ''VESA-2013-3 v1.2'') is a standard by VESA which defines the timings of the component video signal. Initially intended for use by computer monitors and video cards, the standard made its way into consumer television ...
:
Extended display identification data Extended Display Identification Data (EDID) and Enhanced EDID (E-EDID) are metadata formats for display devices to describe their capabilities to a video source (e.g. graphics card or set-top box). The data format is defined by a standard published ...
, as it can interact with the video card with respect to providing information on permissible timings.
; Standards organizations
:
VESA
VESA (), formally known as Video Electronics Standards Association, is an American technical standards organization for computer display standards. The organization was incorporated in California in July 1989To retrieve the information, searc ...
References
External links
* The GTF Standard (free of charge) provides formulas and the companion spreadsheet contains GTF calculations. Se
Standards FAQ - VESAan
Free Standards - VESA - Interface Standards for The Display Industry
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Video signal