Author Topic: xrandr & gtf question.  (Read 335 times)

pigdog

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xrandr & gtf question.
« on: March 17, 2014, 04:09:00 am »
Hi,

If xrandr doesn't show a particular screen resolution - for example 1280x720 does that mean my monitor will not be able to exactly reproduce that resolution?

Even if I plug in a modeline supplied by gtf?

Cheers.

l3mce

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Re: xrandr & gtf question.
« Reply #1 on: March 17, 2014, 03:08:32 pm »
If there is any kind of adapter in the way, this generally kills EDID discovery. That is almost always the answer.

As per building a modeline, try:
cvt 1280 720 60

My sample output on this laptop is:
cvt 1280 720 60
# 1280x720 59.86 Hz (CVT 0.92M9) hsync: 44.77 kHz; pclk: 74.50 MHz
Modeline "1280x720_60.00"   74.50  1280 1344 1472 1664  720 723 728 748 -hsync +vsync

So the modeline in xorg.conf would be:
        Modeline        "1280x720_60.00" 74.50 1280 1344 1472 1664 720 723 728 748 -hsync +vsync

It is important to remember to remove all double spaces after the quotes. In that example there is one after the quote, before the 1280 and one before the 720.

On my core I have:
root@dcerouter:~# cvt 1280 720 60
# 1280x720 59.86 Hz (CVT 0.92M9) hsync: 44.77 kHz; pclk: 74.50 MHz
Modeline "1280x720_60.00"   74.50  1280 1344 1472 1664  720 723 728 748 -hsync +vsync

The one generated by LMCE is:
        Modeline        "1280x720" 74.250 1280 1390 1430 1650 720 725 730 750 +hsync +vsync
You can see they are very close.

You can then set xrandr to use this mode if it is not working right ootb. BTW... if this is a CRT, a bad modeline can physically damage the monitor.

Cheers
« Last Edit: March 17, 2014, 03:12:10 pm by l3mce »
I never quit... I just ping out.

pigdog

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Re: xrandr & gtf question.
« Reply #2 on: March 17, 2014, 08:04:54 pm »
Hi,

Thanks for the information.

My monitor is a HDTV Samsung flat panel that doesn't support 1080p.

I've been playing with AVWizard and screen supported modelines to get max res out of monitor.

It's been a learning experience.  When things work ootb it's nice but then 'sometimes' the challenge is 'fun'.

Cheers.