XFree86 Video Timings HOWTO : Fixing Problems with the Image.
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14. Fixing Problems with the Image.

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.

(Fixing these minor distortions is where xvidtune(1) really shines.)

You move the image by changing the sync pulse timing. You scale 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:

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!

14.1. The image is displaced to the left or right

14.2. The image is displaced up or down

14.3. The image is too large both horizontally and vertically

14.4. The image is too wide (too narrow) horizontally

14.5. The image is too deep (too shallow) vertically


XFree86 Video Timings HOWTO : Fixing Problems with the Image.
Previous: Questions and Answers
Next: The image is displaced to the left or right