Scandoubler output looks horrible on TFT, but great on CRT

[motorollin]

I've got my DCE internal scandoubler installed in my A4000. On my LCD TV, the scansoubler output looks awful. A large amount of the picture is off the screen. The quality is very poor, and there horizontal bars scrolling down the screen.

I brought a 17" CRT home from work today and tried the scandoubler output on that. It looked perfect - absolutely brilliant quality. I'm just wondering if this is normal? Why would the quality be so bad on the TFT? Is it just because the resolution from the scandoubler is not the optimal resolution of the screen?

This is not really a problem as I can just keep the CRT. I'm just curious about why it would happen.

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moto

[motorollin]

It was PAL. I didn't think of trying NTSC since the screen is PAL.

--
moto

[motorollin]

Oh well, I'll keep the CRT. Looks like I'll have an LCD TV for sale soon :-)

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moto

[motorollin]

Well it looks as good through the DCE Scandoubler as it does directly from the RGB port, so I'm happy.

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moto

[motorollin]

A few people have asked why I'm using a scandoubler with an LCD TV. Yes I know that using the SCART input from the Amiga's RGB socket will provide better quality. I have indeed been using it in this configuration for some time. But I wanted to use the CV64's autoswitch, which means scandoubling the RGB output to a VGA signal to feed in to the CV64. Now I know that scandoubled RGB screenmodes look horrible on a TFT screen (using a VGA input) I am no longer using the LCD TV.

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moto

[motorollin]

I'm currently using a Compaq 17" CRT. RGB -> SCART is better than RGB -> VGA on a TFT because low resolutions (like the Amiga's RGB output) have to be scaled up to the high resolution of the TFT screen, which can result in poor quality. If you use the RGB input, then there is presumably some circuitry in the screen's own scandoubler which scales and dithers it nicely. CV64 is shorthand for Cybervision64, which is the graphics card I use. It has a VGA input as well as an output, and it can auto-switch between them.

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moto