Saturday, February 2, 2013

Fix HDMI Overscan without Catalyst

If you hook up your screen using HDMI cable, you will often get annoying borders and distorted graphics due to so-called "overscan". This technology is used with screens that were produced somewhere around stone age and use CRT technology. CRT tube will cut off sides from the picture, effectively removing all or some of taskbar and start menu. Hence, to compensate for that, they artificially squeeze picture to make sure all of it fits. Usually, overscan will eat up to 15% of the screen.

Screens produced after stone age usually have LCD panels with exactly as many pixels as they can display, so the overscan technology is no longer needed. But for compatibility, manufacturers still support it and even make it default.

Micrtosoft supplies drivers for my ATI graphics card. I really do not want any other software. Only thing I must have which they don't let me configure is disable annoying overscan. I found this article, which didn't help me, but gave me an idea what to do:

  1. Go to regedit, navigate to HKLM\SYSTEM\CurrentControlSet\Control\Video.
  2. Locate a GUID with 0000, 0001, 0002 entries that has a bunch of values underneath
  3. Set following values:
    TVEnableOverscan: DWORD = 0
    DigitalHDTVDefaultUnderscan: DWORD = 0

Screenshot of my regedit
I didn't have DigitalHDTVDefaultUnderscan in that registry key, so I had to create it. Once I crated it and rebooted, screen which was connected to HDMI started working properly.