<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">
<HTML>
<HEAD>
<META HTTP-EQUIV="Content-Type" CONTENT="text/html; charset=iso-8859-1">
<TITLE>Fixing Problems with the Image.</TITLE>
</HEAD>
<BODY BGCOLOR="#efefef" TEXT="black" LINK="blue" VLINK="#551A8B" ALINK="red">

<A HREF="VideoModes.html"><EM>XFree86 Video Timings HOWTO</EM></A>
 <b>:</b> <EM>Fixing Problems with the Image.</EM><BR>
<b>Previous:</b> <A HREF="VideoModes13.html"><EM>Questions and Answers</EM></A><BR>
<b>Next:</b> <A HREF="VideoModes15.html"><EM>Plotting Monitor Capabilities</EM></A>


<HR NOSHADE>
  <H2><A NAME="20"></A>14. Fixing Problems with the Image.<A NAME="fixes"></A></H2>

<p>OK, so you've got your X configuration numbers.  You put them in Xconfig with
a test mode label.  You fire up X, hot-key to the new mode, ... and the image
doesn't look right.  What do you do?  Here's a list of common problems and how
to fix them. </p>
<p>(Fixing these minor distortions is where <b>xvidtune</b>(1) really shines.)</p>
<p>You <em>move</em> the image by changing the sync pulse timing.  You
<em>scale</em> it by changing the frame length (you need to move the
sync pulse to keep it in the same relative position, otherwise scaling will
move the image as well).  Here are some more specific recipes: </p>
<p>The horizontal and vertical positions are independent.  That is, moving the
image horizontally doesn't affect placement vertically, or vice-versa.
However, the same is not quite true of scaling.  While changing the horizontal
size does nothing to the vertical size or vice versa, the total change in both
may be limited.  In particular, if your image is too large in both dimensions
you will probably have to go to a higher dot clock to fix it.  Since this
raises the usable resolution, it is seldom a problem! </p>

<H3><A NAME="21"></A>14.1. The image is displaced to the left or right</H3>

<p>To fix this, move the horizontal sync pulse.  That is, increment or decrement
(by a multiple of 8) the middle two numbers of the horizontal timing section
that define the leading and trailing edge of the horizontal sync pulse. </p>
<p>If the image is shifted left (right border too large, you want to move
the image to the right) decrement the numbers.  If the image is shifted right
(left border too large, you want it to move left) increment the sync pulse. </p>

<H3><A NAME="22"></A>14.2. The image is displaced up or down</H3>

<p>To fix this, move the vertical sync pulse.  That is, increment or decrement the
middle two numbers of the vertical timing section that define the leading and
trailing edge of the vertical sync pulse. </p>
<p>If the image is shifted up (lower border too large, you want to move the image
down) decrement the numbers.  If the image is shifted down (top border too
large, you want it to move up) increment the numbers. </p>

<H3><A NAME="23"></A>14.3. The image is too large both horizontally and vertically</H3>

<p>Switch to a higher card clock speed. If you have multiple modes in your
clock file, possibly a lower-speed one is being activated by mistake.</p>

<H3><A NAME="24"></A>14.4. The image is too wide (too narrow) horizontally</H3>

<p>To fix this, increase (decrease) the horizontal frame length.  That is, change
the fourth number in the first timing section.  To avoid moving the image, also
move the sync pulse (second and third numbers) half as far, to keep it in the
same relative position. </p>

<H3><A NAME="25"></A>14.5. The image is too deep (too shallow) vertically</H3>

<p>To fix this, increase (decrease) the vertical frame length.  That is, change
the fourth number in the second timing section.  To avoid moving the image,
also move the sync pulse (second and third numbers) half as far, to keep it in
the same relative position. </p>
<p>Any distortion that can't be handled by combining these techniques is probably
evidence of something more basically wrong, like a calculation mistake or a
faster dot clock than the monitor can handle. </p>
<p>Finally, remember that increasing either frame length will decrease your
refresh rate, and vice-versa. </p>

 <HR NOSHADE>
<A HREF="VideoModes.html"><EM>XFree86 Video Timings HOWTO</EM></A>
 <b>:</b> <EM>Fixing Problems with the Image.</EM><BR>
<b>Previous:</b> <A HREF="VideoModes13.html"><EM>Questions and Answers</EM></A><BR>
<b>Next:</b> <A HREF="VideoModes15.html"><EM>Plotting Monitor Capabilities</EM></A>



</BODY>
</HTML>
