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Ralsina.Me — Roberto Alsina's website

Overscan Fix for Intel on a Cheap TV

I got a re­al­ly, re­al­ly cheap 24" 1080p TV to use as a mon­i­tor.

Once I fi­nal­ly got hold of the mi­cro-HD­MI->HD­MI adapter and plugged it in, of course, I ran in­to over­scan is­sues.

What's overscan?

When TVs get a full res­o­lu­tion feed over HD­MI, then zoom it a bit and trim the edges be­cause tv sig­nals usu­al­ly have garbage there.

How­ev­er, com­put­er's don't. In fac­t, be­cause of Fit­t's law, the edges are some of the most in­ter­est­ing bits of the screen.

The usu­al so­lu­tion for this is to set a spe­cif­ic mode in the TV menus, like "1:1" or "Just scan" which dis­ables over­scan. But this is a very cheap TV and has no such things.

The sec­ond usu­al so­lu­tion is to use nvidia util­i­ties and con­fig­ure "un­der­scan". But I have an in­tel board and can't do such things.

The third usu­al so­lu­tion is to use "xran­dr --­trans­for­m" to tweak the screen. But that makes the right and bot­tom edges be hid­den.

The fourth usu­al so­lu­tion is to set­up a cus­tom mode that does­n't trig­ger the TV's over­scan, but that means you are not do­ing 1:1 pix­els and things look ug­ly

The fifth usu­al so­lu­tion is to use a VGA in­put, which has no over­scan. But my VGA adapter/­ca­ble com­bi­na­tion pro­duces fuzzy im­age and the TV can't quite sync it, so I lose the left edge.

The sixth (not quite usual solution) is to use xrandr --out­put HD­MI --set au­dio force-d­vi because that will trigger some random combination of side effects in the intel driver and make the TV believe it's getting DVI input (the TV even says DVI on its mode info!?!) and not overscan.

But that made my screen look pur­ple.

So, seventh solution, which worked for me: xrandr --out­put HD­MI --set au­dio force-d­vi --­mode 1920x1080i

UP­DATE: The im­age qual­i­ty in 1080i is not as good as 1080p, and the pur­ple tint is prob­a­bly fix­able us­ing xran­dr's --gam­ma op­tion.

And no, I have no ex­pla­na­tion for it.

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