[mythtv-users] OT: How to calculate displaysize

[Brian C. Huffman]

Discussion about mythtv <mythtv-users at mythtv.org> wrote: 
> 
> 2) You can calculate the appropriate "DisplaySize" based on the 
> resolution you're using:
> 
> Given 1 inch = 25.4millimeters
> DisplaySize is specified in millimeters
> You're using a resolution of X x Y:
> 
> DisplaySize should be set to the truncated integer value (note, you have 
> to do the math yourself, don't specify the equation in your X 
> configuration file):
> 
> DisplaySize: ((X / 100) * 25.4) ((Y / 100) * 25.4)
> 
> So, for 1024x768:
> 
> 1024 / 100 = 10.24 * 25.4 = 260.096 = 260
> 768 / 100 = 7.68 * 25.4 = 195.5072 = 195
> 
> DisplaySize  260 195
> 
> Some round instead of truncating.  I've found that truncating gives best 
> results...
> 

This doesn't make sense to me (probably why I'm asking the question in the first
place).  You're calculating displaysize based on the resolution rather than the
physical dimensions of the display.  The man page for xorg.conf says the
following:

DisplaySize width height
    This optional entry gives the width and height, in millimetres, of the
picture area of the monitor. If given this is used to calculate the horizontal
and vertical pitch (DPI) of the screen.

If this option is calculated this way, the Xserver could do it by itself? 
Honestly, logic would tell me to get out a tape rule and measure my TV, but
obviously the information that I'm reading is telling me something different. 
Still confused.  :-(

-b