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XF86 - Resolution Question
http://forum.linhes.org/viewtopic.php?f=6&t=7551		 Page 1 of 2
Author:  ed3120 [ Tue Dec 27, 2005 2:43 pm ]
Post subject:  XF86 - Resolution Question
In XF86Config-4, what is the purpose of listing multiple resolutions. (like in the example below from knoppmythwiki) I've heard that myth picks the first resolution listed (800x600 below) but even list 640x480 if it is going to ignore it. Wouldn't that be the same as commenting it out?

Could someone please explain how this works?

# The "magic" modelines borrowed from someone else
Modeline "800x600" 40.12 800 848 968 1056 600 601 605 628 #60Hz
# From http://xtiming.sourceforge.net/cgi-bin/xtiming.pl
# hfreq: 37.9 kHz
Modeline "800x600@60" 38.21 800 832 976 1008 600 612 618 631

# The "magic" modelines borrowed from someone else
Modeline "640x480" 25.175 640 664 760 800 480 491 493 525 #60Hz
# From http://xtiming.sourceforge.net/cgi-bin/xtiming.pl
# hfreq: 30.43 kHz
Modeline "640x480@60" 24.11 640 672 760 792 480 490 495 505


source: http://www.knoppmythwiki.org/index.php? ... X5200HowTo
Author:  ceenvee703 [ Tue Dec 27, 2005 3:44 pm ]
Post subject: 
I guess it's to try out different resolutions, but I regularly get rid of any modelines I'm never going to use, comment out ones that I'm experimenting with or might want to use, and only have one "active" modeline.

Note that what X uses also depends on the "screen" section at the end... you can have lots of active modelines, but only the ones you use in the Subsection "Display" line will be used. I only have one modeline here too, as I've never grokked how cycling through different resolutions is useful under X (it always gives me a virtual desktop, which is not helpful with MythTV).
Author:  Xsecrets [ Tue Dec 27, 2005 7:25 pm ]
Post subject: 
there are two other benefits of having multiple modelines.

1) you can use the ctrl+alt++/- to cycle through the resolutions, though the virtual screen size stays the same, so this has very limited uses.

2) much more interesting is you can use xrandr to swap resolutions, and with some work and tweaking you should theoretically (I haven't actually made it work yet) be able to play each recording at it's native resolution.
Author:  tjc [ Tue Dec 27, 2005 7:27 pm ]
Post subject: 
Notice that the names (the bit in quotes right after the word Modeline) for the different lines at the same resolution are spelled differently... ("800x600" vs. "800x600@60" ) The fact that the names reflect the resolution is just convention, you could call them anything, even "Barney" and "Betty". Down in the "Screen" section it uses those names to link back to the definitions in the "Monitor" section. Notice how the Screen section also uses the names "Card0" and "Monitor0" (again both arbitrary names, you could call them "Fred" and "Wilma" just so long as you were consistent) to link back to the appropriate Monitor and Device... :idea:
Author:  ed3120 [ Wed Dec 28, 2005 9:48 am ]
Post subject: 
Thank you...this is very helpful. I think I'm interested in the xrandr command. What I am looking to do is cycle through different resolutions on the fly on my TV to see which ones look the clearest. It takes too long to do that with a reboot in between.

What is the syntax for xrandr? Do I use the modeline names as a switch?
I.e. Would I bring up a shell and type "xrandr 800x600" ?

Also, can I can use XF86Config-4 to determine the position of the image on my TV's screen. Right now the image is on the left side of my TV and there is a 1 inch black border on the right side. I am trying to find a way to move the screen to the right.
Author:  Xsecrets [ Wed Dec 28, 2005 10:06 am ]
Post subject: 
I can't remember the exact syntax, but something like xrandr --help should give you the syntax. I think xrandr with no arguments gives you a list of available resolutions, but it's been a while since I used it from command line. And no it cannot be used to move the screen around. for that you would have to use something like xvidtune or nvtv or nvidia-settings for nvidia cards.
Author:  gamelyn31 [ Sun Jan 01, 2006 9:39 am ]
Post subject: 
Perhaps this is common knowledge to those who are familiar with the XF86Config-4 file, but I've learned a couple things during my tinkering...

It seems like there are several dozen predefined ModeLine settings in the monitor section of the XF86Config-4 file. When Linux boots up (or is it when X starts?) it goes through all these entries and compares them against the HorizSync and VertRefresh values defined at the top of the Monitor Section. (For KnoppMyth purposes, this is where the HorizSync is set to 30-50 and VertRefresh is set to 60 for output to a tv). If any of the ModeLine entries are outside of the valid ranges for these values, they get filtered out. You can look at the log file /var/log/XFree86.0.log (which tjc suggested in a different post) to see which ModeLines are being flagged as invalid, and why.

Finally, after all the invalid ModeLines are filtered out, the "first best fit" for the connected monitor is selected. Again, this selection gets entered in the log file.

As part of this filtering process, it seems to filter out some ModeLines with messages like:

"width too large for virtual size"
"height 600 is larger than EDID-specified maximum of 540"

Anybody have any insight about these messages? What is EDID and why is the max 540? Can it be changed? Should it be changed? If so, how? Also, how do you set the virtual screen size? In the log file, there's an entry which says: "Virtual screen size determined to be 640 x 480" How is that determined? I have a 65" CRT HD tv that's capable of displaying [whatever] x 1080i. I certainly don't want to be limited to 640 x 480.
Author:  tjc [ Sun Jan 01, 2006 10:48 am ]
Post subject: 
gamelyn31 wrote:
It seems like there are several dozen predefined ModeLine settings in the monitor section of the XF86Config-4 file.

There are actually a bunch built into the server. I've got exactly 4 modelines in my /etc/X11/XF86Config-4 file (2 each 640x480 and 880x600) and it still scans about sixty default ones. Someday I may even bother to look up the option to make it stop that sillyness...
gamelyn31 wrote:
"width too large for virtual size"
"height 600 is larger than EDID-specified maximum of 540"

Anybody have any insight about these messages? What is EDID and why is the max 540? Can it be changed? Should it be changed? If so, how? Also, how do you set the virtual screen size? In the log file, there's an entry which says: "Virtual screen size determined to be 640 x 480" How is that determined? I have a 65" CRT HD tv that's capable of displaying [whatever] x 1080i. I certainly don't want to be limited to 640 x 480.

1080 / 2 == 540 (i.e. without the interlacing) I believe that you can turn off the EDID stuff via an option in the file. See the readme files in /usr/share/doc/NVIDIA_GLX-1.0/ for more details.
Author:  Xsecrets [ Sun Jan 01, 2006 10:57 am ]
Post subject: 
yes edid is specified from the monitor/tv. in some cases they don't specify correctly, and yes there is an option you can find in the readme file tjc already referenced to turn off the edid checks.
Author:  declanh [ Tue Jan 03, 2006 4:06 am ]
Post subject: 
not 100% on topic i expect - but in the same ballpark i guess

My lcd tv has resolution 1280x768 - im using it via the vga connector with
/etc/X11/XF86Config-4 configured for 1024x768

I have a radeon 7000 graphics card which im not sure supports 1280 x 768


basically im asking - is there a way i can improve the display output by changing the resolution or am i stuck at 1024x768


thanks in advance
d
ps - picture quality is fine as it stands - just wondering if it could be improved
Author:  ed3120 [ Tue Jan 03, 2006 8:21 am ]
Post subject: 
I tried playing around xrandr, but I couldn't figure it out. I would type it with a number after it, which should make it change resolutions, but it wasn't working. Is there anything that needs to be configured prior to using xrandr?
Author:  Xsecrets [ Tue Jan 03, 2006 10:22 am ]
Post subject: 
no nothing has to be configured. if you run it with no arguments it should tell you all the possible resolutions it sees. For how to change stuff do xrandr -h will give you the syntax and switch options.
Author:  zetoune [ Wed Feb 01, 2006 3:51 pm ]
Post subject: 
what are the values shown in ModeLine.

there is a modeline genetor at http://xtiming.sourceforge.net/cgi-bin/xtiming.pl, but I don't know what values I have to enter?

How can I know these values?
Author:  tjc [ Wed Feb 01, 2006 11:17 pm ]
Post subject: 
For a TV there are standard ones. For a monitor it's often printed on the back, or in the documentation, or on the manufacturers website, or avilable via a Google search.

For example let's say I've got a "Dell D1226H" 19" monitor sitting in front of me. The third or fourth hit from a Google search was this page: http://www.etech4sale.com/products/part ... 27374.html which amoung other things tells you:
Quote:
Scanning Frequency
Horizontal (line) 30 to 95 kHz (AutoScan)
Vertical (frame) 50 to 160 Hz (AutoScan)

Which along with a desired resolution and aspect ratio should be plenty of information to feed the generator. You don't need to fill in every field, some of the information is redundant and just there to let you come at the problem from different directions.
Author:  zetoune [ Thu Feb 02, 2006 8:53 am ]
Post subject: 
tjc: ok. But for my case my monitor is my 27" TV.
The standard values for a TV you are speaking about are :
30-50 for Horizontal Rate
60 for Refresh Rate (same as Verticale Rate?)
Am I correct?

What is the Dot Clock Frequency for a TV?
I have to check "interlace", don't I?

I don't have to change advanced configuration.

Maybe I can stay with values that are in the XF86Config-4.sample.nvidia-tvout, but I like to understand what I'm doing.
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