Wednesday, August 04, 2004

Adjusting Display Video Setting for Xserver 4.x.x

The annoying thing I notice with dual booting Windows and Linux is that the display on monitor shifts whenever you switch from one to another (not with all monitors). The reason I found for this is that Xserver is unable to calculate the display timings for that mode correctly.

Until XFree86 release 4.0.0 the XF86Config file used to contain display timings (called modeline setting) for each mode (resolution). From 4.0.0 the XF86Config file got changed radically which removed all the modeline things from the configuration file and Xserver started calculating timings at run time from the specified H & V Sync frequency ranges given in the Monitor section. So if the display gets distorted it means that the Xserver calculations are not suiting the monitor for that mode so we need to give the correct timings in the configuration file with modeline statement.

How do we find out these modeline timing? It happens that the XFree86 4.x.x releases comes with a tool called xvidtune . Using this tool, you adjust all aspects of video setting dynamically when Xserver is actually running. Once you have done that you can ask tool to generate a modeline statement in a suitable format to put in the configuration file. Now copy this line to Monitor section of the XF86Config file and things should be fine.

One more reason for me to like Eric S. Raymond is for his excellent document on this.


At 8/05/2004 10:58 AM, Blogger  said...

One more reason for me to dislike Eric S Raymond is for his document on that.

At 8/20/2004 7:41 PM, Blogger s c r a p s s t u f f s said...

Just what I'm looking for as I go and install Linux on my box at home. I have run into this problem on my work box at my previous company and didn't find the time to investigate (or just felt plain lazy). Now I know what to fix.


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