May 14, 2009

LCD TV distortion lines on image

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Just installed mandriva 2009.1 on my media pc. It is connected to a cheap chinese LCD tv - this tv is always problematic, as it's EDID says it can only support up to 1024x768, whereas it will actually do up to 1280x768.

I edited xorg.conf to get it to ignore the edid and add a modeline for 1280x768. However, when X starts, the tv takes a long time to display an image (like the tv is trying to do something with the signal) and when it does appear, there are 1-3 nearly horizontal bands of distortion running across the screen. I have tried using various pixel clock rates when adding the mode line, with no change (don't have any docs on tv, none online either). If i unplug the tv, and plug in a viewsonic lcd, the image displays fine. I have tried both the free and proprietary graphics card (NV GF4 MX4000) drivers.

There are no errors reported in Xorg.0.log.

This same pc was running kubuntu 9.04beta before, and I was able to get the tv working just by setting "1280x768" under the modes line in xorg - didn't need to add a whole modeline at all....

My laptop, with ati graphics and running kubuntu somehow magically adds 1360x768 @ 59.8Hz to the kde 'display settings' app, and this works fine (a little offscreen as it is only 1280 wide, but fine otherwise).

So.... Any tips on what to try next?

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