VESA Video Modes: Difference between revisions
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===Don't Assume The Monitor Supports A Video Mode=== |
===Don't Assume The Monitor Supports A Video Mode=== |
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We all like pretty graphics and high resolution video modes. Unfortunately, if VBE says that a video mode is supported by the video card it does not mean that the video mode is also supported by the monitor. VESA has defined 2 video mode timings that are meant to be supported by all monitors (640 * 480 standard VGA timing and 720 * 480 standard VGA timing). For all other video modes you should either use EDID to find out if the monitor supports the video mode's timing (or not), or provide a way for the user to test the video mode and change it if it doesn't work. |
We all like pretty graphics and high resolution video modes. Unfortunately, if VBE says that a video mode is supported by the video card it does not mean that the video mode is also supported by the monitor. VESA has defined 2 video mode timings that are meant to be supported by all monitors (640 * 480 standard VGA timing and 720 * 480 standard VGA timing). For all other video modes you should either use EDID to find out if the monitor supports the video mode's timing (or not), or provide a way for the user to test the video mode and change it if it doesn't work. This is the approach used by Windows, with a dialog box appearing with the option to accept or revert. No action within 15 seconds reverts. Just an idea ;). |
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Using EDID for this purpose is complicated. Unless you provide a "CRTC information block" structure when you set the video mode you can't be entirely sure what timing the video card will use; and only some video cards that support VBE 3.0 support the "CRTC information" correctly. |
Using EDID for this purpose is complicated. Unless you provide a "CRTC information block" structure when you set the video mode you can't be entirely sure what timing the video card will use; and only some video cards that support VBE 3.0 support the "CRTC information" correctly. |
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* 320 * 240 (actually uses "640 * 480" timing) |
* 320 * 240 (actually uses "640 * 480" timing) |
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Colour depth doesn't/shouldn't effect the video timing signals. This means that the best possible safe video mode would be 720 * 480 * 24/32-bpp. |
Colour depth doesn't/shouldn't effect the video timing signals. This means that the best possible safe video mode would be 720 * 480 * 24/32-bpp. |
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==See Also== |
==See Also== |
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