EDID - detect proper DPI and refresh rate values

Question

I just tried to extract EDID file data with read-edid util; The thing is the output shows :

$sudo get-edid | decode-edid

...
Manufacturer: AUO Model 20ec Serial Number 0
Made week 0 of 2013
EDID version: 1.4
Digital display
6 bits per primary color channel
Digital interface is not defined
Maximum image size: 34 cm x 19 cm
Gamma: 2.20
Supported color formats: RGB 4:4:4
First detailed timing is preferred timing
Established timings supported:
Standard timings supported:
Detailed mode: Clock 77.000 MHz, 344 mm x 193 mm
               1366 1382 1398 1628 hborder 0
                768  771  785  788 vborder 0
               -hsync -vsync
Manufacturer-specified data, tag 15
ASCII string: AUO
ASCII string: ***
...

I checked the xrandr and it outputs :

$xrandr
    Screen 0: minimum 320 x 200, current 1366 x 768, maximum 8192 x 8192
    eDP1 connected 1366x768+0+0 (normal left inverted right x axis y axis) 344mm x 193mm
       1366x768      60.02*+
       1024x768      60.00  
       800x600       60.32    56.25  
       640x480       59.94 
...

And it shows I have 60.02 refresh rate or similar which is not correct?...

As a test, according to the EDID I created /etc/X11/xorg.conf.d/90-monitor.conf file with content as :

Section "Monitor"
    Identifier             "<default monitor>"
    DisplaySize             344 193
EndSection

...as you can see, the xrandr outputs as enabled the 344x193 display size but still I am not sure is the 344x193 are correct values? Should it be 344x193 or 340x190 according to "Maximum image size: 34 cm x 19 cm" values?

Moreover, the EDID shows my notebook has 77.000MHz refresh rate (supposed to be) but the xrandr outputs (see above) I have 60.000MHz, as I can get it; So that makes me confused which values really should be used for xorg? And should I have (in linux .config) PWM as y or m if I need un-standard refresh rate be running?

So my question is... how to use proper DPI and refresh values from EDID to set them into /etc/X11/xorg.conf.d/90-monitor.conf file and have them valid?

p.s.

• kernel 3.16.7
• os Linux Arch x64
• video card : Intel HD Graphics (Sandy Bridge - Bay Trail)

Answer 1

77MHz is the pixel clock, not the vertical refresh rate. The vertical refresh rate is measured in Hz, not MHz.

Take a look at the mode:

   Clock 77.000 MHz, 344 mm x 193 mm
   1366 1382 1398 1628 hborder 0
    768  771  785  788 vborder 0

1366 is the number of "active" pixels per line, and 768 is the number of "active" lines. These are pixels you see. There are also "blanking" pixels and lines and "border" pixels and lines that are inserted to even out the clock.

See the one metric that says 1628x788? This is the one that includes all active, blanking, and border pixels. If you divide 77MHz (or 77,000,000Hz) by (1628 * 788), you'll see that you get roughly 60.02 Hz.