# VESA CVT Standard - How to calculate video timings?

Most video resolutions like VGA (640x480), UXGA (1600x1200) or HD720 (1280x720) are defined by VESAs Coordinated Video Timing (CVT) standard. (It can be freely downloaded from VESA.org).

The download results in an Excel sheet, where one can enter the display resolution and several properties like reduced blanking. After that, the Excel sheets prints out the results like Pixel Clock, H-Front-Porch, H-Back-Porch or VSync polarity.

I would like to get the equations, so I can calculate all VESA timings in VHDL for one of our universal VGA timing modules.

I also found a Display Monitor Timing (DMT) document that lists all timings, but unfortunately no equations.

Alternative Solution:
How can I enter all known video resolutions into the Excel sheet and export the results into a file. I don't want to enter them manually.

Appendix:

Known display resolutions. Source: wikimedia.org.

• Have you looked at the equations in the spreadsheet calculator? – Tom Carpenter Aug 5 '15 at 18:31
• @TomCarpenter The spreadsheet has maybe 50 equations. Re-engineering the equations sounds very error-prone => many substitutions and nested if-then-else functions. Yes it's a possibility, but I would be glad to find a less error-prone solution :). – Paebbels Aug 5 '15 at 18:37
• There is no equation that I know of, some timings are somewhat related (double the resolution, double every values), but most of them are old and rely on standard clock frequencies available at the time (like 25.125MHz) to derive it's parameters. Morever, modern displays use EDID to export the timings modes it supports, and often doesn't support older "standard resolutions" or framerate. – Jonathan Drolet Aug 5 '15 at 18:45
• @JonathanDrolet Is EDID related to the I2C bus in the VGA connector (DDC)? Unfortunately, not every FPGA board supports these additional pins. Is EDID also a free standard from VESA? – Paebbels Aug 5 '15 at 19:21
• Yes, it's related to the I2C bus of the VGA connector (or HDMI connector, for that matter). Wikipedia has a page... It is a VESA standard as far as I know. Note that HD resolutions are not in your VESA document, they are in the CEA 861B standard (not free). However, many display supports HD resolutions on their VGA port. – Jonathan Drolet Aug 5 '15 at 19:25

The X.org distribution includes the tool cvt, which is based on that spreadsheet. It is implemented in hw/xfree86/utils/cvt/cvt.c and hw/xfree86/modes/xf86cvt.c.