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DDC/EDID: Difference between revisions

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The data to be returned over DDC is stored in [http://en.wikipedia.org/wiki/Extended_display_identification_data EDID] format.
The data to be returned over DDC is stored in [http://en.wikipedia.org/wiki/Extended_display_identification_data EDID] format.
==When it doesn't work==
==When it doesn't work==
Sometimes, despite hardware support, DDC breaks down. This usually manifests as bad settings in [[Xorg_hell|X]], especially regarding viewing dimensions (DisplaySize) and DPI (DPI, NVIDIA-specific option). Look at <tt>xdpyinfo</tt> to see what X believes the settings to be.
Sometimes, despite hardware support, DDC breaks down. This usually manifests as bad settings in [[Xorg_hell|X]], especially regarding viewing dimensions (DisplaySize) and DPI (DPI, NVIDIA-specific option). Look at <tt>xdpyinfo</tt> to see what X believes the settings to be. DisplaySize is described in millimeters (25.4 per inch).
* Extract H*V from a diagonal length using the Pythagorean Theorem and the resolution ratio
* Divide H and V by their appropriate resolutions to get the DPI
 
==See also==
==See also==
* [http://www.mythtv.org/wiki/Specifying_DPI_for_NVIDIA_Cards Specifying DPI for NVIDIA Cards] at the MythTV site
* [http://www.mythtv.org/wiki/Specifying_DPI_for_NVIDIA_Cards Specifying DPI for NVIDIA Cards] at the MythTV site
* [http://http.download.nvidia.com/XFree86/Linux-x86/1.0-8178/README/appendix-y.html Appendix Y -- DPI] from the NVIDIA documentation
* [http://http.download.nvidia.com/XFree86/Linux-x86/1.0-8178/README/appendix-y.html Appendix Y -- DPI] from the NVIDIA documentation