Generalized Timing Formula is a standard by VESA which defines exact parameters of the component video signal for analogue VGA display interface.
The video parameters defined by the standard include horizontal blanking (retrace) and vertical blanking intervals, horizontal frequency and vertical frequency (collectively, pixel clock rate or video signal bandwidth), and horizontal/vertical sync polarity.
These parameters are used by the XFree86 Modeline, for example.
This video timing standard is available from VESA for 350 USD.
History
The standard was adopted in 1999, and was superseded by the Coordinated Video Timings specification in 2002.
References
Generalized Timing Formula Wikipedia(Text) CC BY-SA