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Old 23 April 2009, 14:43   #1
crabfists
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DCE flicker magic: bad image quality on LCD monitor

After not touching anything Amiga for a year or so I somehow managed to get obsessed again. Bad timing really with an 18 month old daughter and another baby due in 2 weeks but you can't help these things.

I'm about to put all of my amiga stuff in storage, ready for some building work being done, and before I pack them away I thought I would just check they all still work. I fired up my A3000D (68030, Picasso IV, DKB3128 128Mb & Ariadne network) and that still works. I thought I would fire up the A1200 (Blizzard 68030 64Mb, 4Gb compact flash, pcmcia network card & internal DCE flickermagic scandoubler). It still works but something that always has bugged me is the quality of the picture I get on my Dell 2001FP LCD screen. No matter how much fiddling I do with the settings on the 2001FP I cannot get a good image. I get vertical banding/lines all over the screen where it looks like the monitor is trying to rescale the image but can't quite do it without introducing artifacts. Even on a pure colour screen I get the vertical lines. I can post a photo of the problem if people want to have a look?

For example, on a black screen I get vertical lines of grey. If I alter the pixel clock settings on the monitor it shifts the lines left or right but no setting will make them go away. I always thought the dodgy image quality was unavoidable and it's just a property of scan doublers and LCD monitors but I am beginning to think there is something wrong with my SD/FF?

The native resolution of the screen is 1600x1200 and it seems whichever amiga screen mode I try I get the same vertical lines.

I have tried plugging the 1200 into another LCD monitor and that produces the same results.

Has anybody got similar experiences with this SD/FF or know why this would happen? I am thinking about selling it and buying an Indivision AGA instead but I am not sure if this will have the same problems.
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Old 23 April 2009, 14:55   #2
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Are you running in 50Hz (PAL) or 60Hz (NTSC)?

If you boot your Amiga while holding down both mouse buttons and then press SPACE you can toggle between the two (KS3.1 only??)

What is the image like on a CRT? If it is equally poor it could be the shielding (or rather lack of it) on the VGA cable.
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Old 23 April 2009, 19:11   #3
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I am running in PAL - 50Hz. I will try a CRT screen and another VGA cable and see if that helps. Thanks for the suggestion.
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Old 23 April 2009, 22:48   #4
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I plugged the flicker magic into an IBM flat panel at 1024x768 and it worked fine in PAL or NTSC.
It looked awful of course what with the panel scaling the picture.
On CRT the picture is fantastic.
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Old 24 April 2009, 09:46   #5
crabfists
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Right, I tried another LCD and a CRT screen with a different VGA cable. It does seem it's just a scaling issue with LCD screens as the image is fine on CRT. I don't quite understand why it looks so bad though. I know when you put a LCD in a non-native resolution it can look a little distorted due to rescaling, like if you put a 1600x1200 screen into 1024x768, but this seems to be more than just distortion. Like I said, with the amiga I get colour banding, where the grey workbench backdrop will have vertical bars of light and dark grey where it should just be pure colour.

Due to space, I don't want to buy a CRT screen just for the amiga so that is not an option.

The question is, if I buy an Indivision AGA will I still get this problem? Does anybody use an Indivision AGA with an LCD screen? Do you see these problems?
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Old 24 April 2009, 10:10   #6
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Quote:
Originally Posted by crabfists View Post
It does seem it's just a scaling issue with LCD screens as the image is fine on CRT.
Did you try to adjust the clock & clock phase on your LCD monitor? Check your monitors options, should be there.

Quote:
Originally Posted by crabfists View Post
I don't quite understand why it looks so bad though.
Did you try 60Hz? Perhaps the monitor was never rated for vertical refresh of 50Hz. Most LCD monitors cannot handle inputs that low (and just do not display anything). 56Hz is usually the cut off point.

Quote:
Originally Posted by crabfists View Post
The question is, if I buy an Indivision AGA will I still get this problem?
Possibly. The scaler is inside the Indivision AGA so if it is scaling of the monitor then it may help. However I don't think the Indivision goes upto 1600x1200. But I could be wrong.

If it isn't the panels scaling and it is the frequency, Indivision AGA can scan-rate convert to a higher frequency at the penalty of smooth scrolling.
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Old 24 April 2009, 15:39   #7
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I had basically the same problem with my 17 inch 1280x1024 lcd monitor. On mine 640x480 worked good because everything was large, 800x600 had the banding problem that I couldn't get rid of, 1024x768 actually worked really good, and of course 1280x1024 worked very good. The non popular resolutions were truly awfull, very blocky and almost unreadable. With a CRT monitor all resolutions were good. This was also true with Windows.

I think it has to do with how well lcd monitors are optimized for scaling at each resolution. I discovered that the filters in WinUAE did a much better job of scaling then the lcd monitor did. Now I run the lcd monitor at 1280x1024 and let WinUAE do the scaling from whatever resolution I'm using on the Amiga.
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Old 24 April 2009, 17:07   #8
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Quote:
Originally Posted by Ed Cruse View Post
Now I run the lcd monitor at 1280x1024
You mean you run your gfx card at 1280x1024

Always best to run at panel resolution if your CPU/GPU are powerful enough.

Quote:
Originally Posted by Ed Cruse View Post
800x600 had the banding problem that I couldn't get rid of
Gotta be a naff monitor then... I've got two of the worlds cheapest LCD monitors here and both (with a bit of coaxing) work "acceptably" at any input resolution. You have to use a nice cable, and tweak the clock & clock phase but they work.
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Old 24 April 2009, 17:40   #9
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Quote:
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Always best to run at panel resolution if your CPU/GPU
are powerful enough.
True. That's why on my A3000D I run at 1600x1200

I think I am gonna get an Indivision AGA anyway and take the risk of the picture being rubbish on this monitor. Looking at photos of other people running Indivisions on LCD panels they don't seem to have the same problem. I may need to upgrade my Dell 2001FP for something that scales better.

Anybody want to buy a DCE flicker magic? At least I think it's a flicker magic. Its got the extra 2 chips where the scan magic has none.

ps Yes I have tried fiddling with the pixel clock settings but it doesn't help.

Last edited by crabfists; 24 April 2009 at 20:54.
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Old 25 April 2009, 00:42   #10
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Quote:
Originally Posted by crabfists View Post
Anybody want to buy a DCE flicker magic? At least I think it's a flicker magic. Its got the extra 2 chips where the scan magic has none.
LCD's work best with a 60hz signal. My A3000's vga display wont get any results on any lcd I've used, unless the a3000 is running in NTSC mode (I'm in the land of PAL).

My DCE scanmagic likewise has to be set to NTSC to produce any results with LCD's. Have yet to try a CRT screen, but as most others have posted, it'll work best.
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Old 25 April 2009, 15:45   #11
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Quote:
Originally Posted by alexh View Post
You mean you run your gfx card at 1280x1024

Always best to run at panel resolution if your CPU/GPU are powerful enough.


Gotta be a naff monitor then... I've got two of the worlds cheapest LCD monitors here and both (with a bit of coaxing) work "acceptably" at any input resolution. You have to use a nice cable, and tweak the clock & clock phase but they work.
Could be, most likely the manufacture didn't optimize very good with 800x600, and very poorly on odd ball resolutions. I adjusted everything I could find many times. I have two of the same monitors bought at different times, both do the same.

I used to run at 1280x1024, but I discovered my monitor did very well at 1024x768. I switched the native Amiga modes to 1024x768 because I run windows and the RTG at 1024x768, so no delay when switching between the three. I run 1024x768 on Windows and the RTG because 1280x1024 is just to small on a 17 inch monitor with my old eyes.
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Old 25 April 2009, 16:31   #12
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Then grab a LCD TV capable of VGA. There are lots of them able to sync down to 50Hz vertical refresh. Problem solved.
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