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How can I eliminate aliasing and 'shadowing' on an HDTV monitor?

Posted on 2010-08-13
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Last Modified: 2013-11-06
I've just set up a two monitor setup with a laptop, with the second monitor being a 31.5" LCD HDTV, connected via DVI.  Since I'm sitting very close to the television (2-3 feet away, probably) I can see a few irritating pixel issues.  

First of all, there are these vertical bands on the screen where there is a ton of aliasing.  Since I'm not an expert on graphics, I'll be a bit more specific, because I might be saying something other than what I mean.  At certain vertical lines on the screen, points that should be one pixel wide would be two or three.  It's a really irritating effect that makes it hard to read on the TV.

Secondly, along these lines and at various other locations on the screen, there is a bit of jitter.  Pixels will be jumping back and forth between black and white at irregular intervals and at boundaries between black and white.  

Finally, there is a frustrating shadow that appears in some images on occasion.  What I mean by this is that about 5 to 7 pixels to the right of text, the blinking text cursor, and other dark-on-light situations, there will be a faint shadow of whatever is there.  It is extremely faint, so it is not as viewable straight on, but just a slight angle up or down will make it very visible.  

Here's what I've tried so far.  I've found a menu in the TV's settings regarding this sort of stuff (I think).  The options are:  H-Position (moves the image horizontally), V-Position (moves the image vertically), Clock (seems to stretch the image horizontally), and Phase (might make a difference with the jittering?).  I've adjusted the first three so as to make the image fill the screen entirely, and I tried to use the fourth to decrease jitter, but the problems persist.  

There's probably one last thing that I should tell you:  In Screen Resolution in Control Panel, the resolution of the monitor is set to 1280 x 768, the maximum that appears to work on the television.  However, when I press the Info button on the TV remote, it reports a resolution of 1360 x 768, a full 80 pixels off.  I do know that if I set the resolution of the output to the TV to 800 x 600, the TV does report the proper resolution, and I don't seem to have any of the problems that I'm reporting here.  

Can anyone confirm or deny my theory on why I have this problem, and help me to fix it either way?

I've included a couple of pictures of what I hope can help you guys understand the problem.  The first is of the text of this question, where the letter 'i' has the aliasing that I'm talking about, and the second is of the shadowing next to the blinking text input cursor.  (The second picture is very hard to see, but look closely at about 12% zoom and you'll notice a darker area 3-4 TV pixels to the right of the cursor).  

Thanks for the help in advance!
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Question by:h2g2guy
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by:ssparks827
ID: 33434675
If you aren't using 1920 x 1080 with an hdtv you are going to get those lines.  The refresh rate on your laptop is too slow and you're seeing them.  

the next best thing would be 720p which is 1280 x 720  try that and make sure your refresh Hz is 60 or below.

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by:h2g2guy
ID: 33434693
Thanks so much for the quick response!  

Unfortunately, I don't think the TV is properly reading the resolution of the incoming video.  If I try 1280 x 720, the TV bafflingly says "Mode Not Supported".  I'm thinking that it's reading the 1280 x 720 input as 1360 x 720 for some bizarre reason.  

The television reports that the refresh rate for the TV is 60Hz, and so does the computer.  
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by:ssparks827
ID: 33434812
Ooops sorry about that.  What is the tv and its specs?  Is it a true HDTV?  Your laptop what is the video card?  the specs

what is the best resolution it will output?
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by:h2g2guy
ID: 33435026
Sorry for the slight delay there.  

This is a Westinghouse 32" class television, with support up to 1080i.  I'm sorry I can't give you any more specifics than that, I just don't know them!  

It is a true HDTV.  

All I know about the integrated graphics chip is that it's name is the Mobile Intel 945 Express Chipset.  Nothing special, really.  Data about the chipset can be found here: http://www.intel.com/Products/Desktop/Chipsets/945G/945G-technicaldocuments.htm

I'm using the Generic Non-PnP driver for the external monitor, which allows output of up to 2048 x 1536.  

Again, I'm sorry I can't give you any more detailed information.  
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by:ssparks827
ID: 33435219
Ok great...I'm going to go out on a limb and ask is it possible that he cable is bad.  Sometimes the most basic things are the problem.  Check the cable and I will check on that Intel Chipset and see what I find.
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by:h2g2guy
ID: 33436509
Heh, I appreciate and understand your reasons for asking such a question.  If you'll humor a short story...

I'm currently in high school, and one day two years ago my teacher was saying that his computer wouldn't turn on.  I looked at it, and realized...he hadn't turned the monitor on.  For this reason (and because I've been on the receiving end of a few of these incidents) I totally understand why you say that the simplest things are often the problem.

To answer your question:  It is extremely unlikely that this cable is bad.  It's less than a year old, and for much of that time it has gone unused.  Nevertheless, I'll see what I can do to test it out on another configuration if I can, and report back what I find.

Thanks again for sticking with the problem!
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by:h2g2guy
ID: 33436611
Just out of curiosity, I just did a quick experiment.  

In WordPad, I set the font extremely small(2 pt) and made a line of lowercase L's.  Then, I zoomed in on the L's so that there would be approximately 1 pixel between each pair of L's.  Finally, I stepped the cursor through the L's and documented how many vertical stripes I hit.  My guess was 80, because that's how many pixels fewer the input is compared to the TV's reported output on the horizontal axis.  

The answer was EXACTLY 80.  

I don't know if this helps you at all.  

About testing the cable:  I'm only on my 'lunch break' right now, which will end in approximately an hour.  Since I can't find another DVI cable, the only way for me to test it would be to plug my computer into another one of the HDTVs in my house.  Unfortunately, when I was setting up the dual monitor display, I was cramped for space on my desk, so it is extremely difficult to get behind the television to hook up or disconnect cables.  Furthermore, I stupidly screwed the DVI cable into the back of the TV, so my only option is to pull the entire TV out from where it is to get behind it.  I don't really have the time to do all that at the moment, so I'll only be able to give you the results of that test tonight (around 7:00pm EST).  Sorry about that.
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by:h2g2guy
ID: 33442151
Oh, man...I'm terribly sorry about this...

I've gotten my abbreviations mixed up.  I'm connecting to the TV via VGA, not DVI.  

I also apologize about the delay in getting that test of the cable done.  I'll do that ASAP.  
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by:ssparks827
ID: 33445966
VGA is the problem.  You will get those shadows with a vga cable and a tv.  The DVI cable should remove the shadowing.
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by:h2g2guy
ID: 33447824
Ok, I suppose that makes sense.

Before I close the question, do you have any idea why the TV would be reporting the wrong resolution?  Because the results of that test I did seem to indicate that that has something to do with the problem.
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ssparks827 earned 500 total points
ID: 33448900
Its possible that the tv isn't able to figure out the configuration and it is basically guessing.  We had some small LCD's that did that.  The larger ones don't seem to have that problem.  I've also noticed the more expensive LCD's don't have that problem either.  So I don't know if the processors onboard are better or if the smaller ones just don't have the brains to figure out what resolution is being pushed to it.

Also one other thing, check the DPI setting for your fonts, and see if changing the size helps.  You also should try installing the DVI cable as this will represent a full digital conntection.  VGA is an analog connection so that is what comes over, were as DVI is a Digital Video Interface so it doesn't have to convert and that could be why the TV isn't picking up the signal correctly.

Good luck!
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by:h2g2guy
ID: 33449734
Thanks so much for sticking with my question!
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