[H-GEN] problems with vertical sync rate

[Stephen Thorne]

On 2009-09-21, Peter Robinson wrote:
> I was told by the lectopia technicians that my vertical sync rate was  
> too high and I should be using 60.
>
> I am running Ubuntu Jaunty on my Dell e6400 (with nvidia card).

Are you using the open source 'nvidia' driver or the closed source 'nv'
driver.

Modern X using the open source drivers can have its modelines configured
dynamically using 'xrandr'. If you're not using the closed source driver
you should be able to create and then use a modeline on the fly.

The relevent sections of the man page:


--newmode name mode
    New modelines can be added to the server and then associated with
    outputs.  This option does the former. The mode is specified using
    the ModeLine syntax for xorg.conf: hdisp hsyncstart hsyncend htotal
    vdisp vsyncstart vsyncend vtotal flags. flags  can  be  zero  or
    more of +HSync, -HSync, +VSync, -VSync, Interlace, DoubleScan,
    CSync, +CSync, -CSync. Several tools permit to compute the usual
    modeline from a height, width, and refresh rate, for instance you
    can use cvt.

Example:

    Forces to use a 1024x768 mode on an output called VGA:
      xrandr --newmode "1024x768" 63.50  1024 1072 1176 1328  768 771 775 798 -hsync +vsync
      xrandr --addmode VGA 1024x768
      xrandr --output VGA --mode 1024x768

To see what modelines have been automatically detected:

$ grep Modeline /var/log/Xorg.0.log | sort -u

The science of creating a usable modeline escapes me entirely, but
hopefully if you find that piece of the puzzle, you can use this to fit
it in the right place.

-- 
Regards Thorne
Development Engineer
NetBox Blue - 1300 737 060