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Old 08-17-2004, 06:58 PM   #1  
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Default Overscan

Repeated from another thread.

Overscan has been a part of TV since the beginning. Basically TVs are set to display a smaller area of the picture than what is received in order to insure there will not be any black borders around the picture. The overscan is due to the TV settings not the devices sending the signal to the TV.

The reason the TV manufacturers do this is twofold. First it was determined that people want to have the entire area of the picture filled. We have seen many posts about getting rid of the black or grey bars on the 16:9 sets when 4:3 images are displayed on this forum. Fact is most people would rather watch a stretched or zoomed picture as opposed to the black or grey bars. Second is the precision of the TVs themselves. Early models in particular could not produce a straight line at the edges of the picture. Over the years the technology has improved in CRTs to where this is the case with computer monitors and most of the time computer monitors are set with a small black border around the picture. This is required in order to be able to see the entire computer frame. For some reason people will accept this setting for a computer monitor, but will not for watching TV.

Fixed pixel monitors have eliminated this issue, but because the television programming producers still produce images targeted for the "sweet spot" many plasmas and flat panels only display the overscaned picture instead of the entire picture. If they displayed the entire picture received, you would get black surrounds or video noise in the surround areas on many programs.

Due to the overscan issue, it caused a problem when you try to use the HDTV as a computer monitor in that some of the desktop is not displayed on the TV screen. The amout of the desktop that is cut off will vary between 5% and 15% according to what I have read.



Here are two screen captures of my desktop:




Fig. 1 - Screen that shows on my computer monitor



Fig. 2 - Overscanned screen that shows on my HDTV.

As can be seen in Fig. 2, there is a whole row of icons across the top and an entire column on the left that is not shown on the overscaned TV screen. Additionally the Start button and the bottom row of windows is off the screen.

The resolution for the images shown is set at 1380x720p and the clarity of the HDTV picture is very good and quite useable except for the overscan. The connection to my 50" HDTV is through the component cables using a Key Digital KD-VTCA3 VGA to component converter. This converter allows me to have both my VGA monitor and my HDTV connected at the same time.

The video card I am using is an ATI 7500 pci Radeon that has both a DVI and a VGA output connector, so I'm able to connect my 40" HDTV in my living room via the DVI connection and the overscan is about the same. The overscan is somewhat better at 1920x1080i, but the overall picture is worse when displaying computer screens.

Now getting to the aspect of using a computer as a DVR what troubles me at this point is two things. First, with the overscan issue having control of the computer through the use of the HDTV is almost impossible. When I use the HDTV as a monitor I launch the desired program by using my computer monitor then size the program window to fit within my HDTV screen. That would be ok for recorded programs assuming the software did not compensate for the overscan. If it does, then even more of the picture could be chopped off! Secondly, the only programs that I could record with the ATI solution would be the OTA broadcasts and I'm not sure that is worth it. I'm going to wait for at least a card with component inputs so I can record my Voom receiver output.

Link Removed

Edit:
If you have the ability to get into your TV's service menus, there is the possibility of resetting the height and width to eliminate the overscan. Some TVs allow for individual setting on each input.

Last edited by rbinck; 07-27-2005 at 03:37 PM..
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Old 03-02-2005, 10:23 PM   #2  
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This link you've posted, is unfortunately no longer working.

Best regards and waiting from an answer from you someday,
Alessandro Marinho.

rbinck edit:
I removed the redundant post in quote and thanks for pointing out the problem with the link.

Last edited by rbinck; 03-03-2005 at 05:26 AM..
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Old 03-02-2005, 11:19 PM   #3  
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Let's say your tv has 10% overscan. If you adjust that to 5% does that improve resolution as you have compressed more video into less space? Is this a procedure that can be done in the service menu without a calibration DVD?
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Old 03-03-2005, 05:32 AM   #4  
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I suppose you could say it would improve the resolution on a CRT type TV. Reducing overscan will show more of the original picture.

Basically to reduce overscan you are reducing the height and width adjustments. Any source that has a circle should be fine to maintain the proper aspect ratio so the circle stays round.

I'd use extreme caution when getting into the service menu.
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Old 03-06-2005, 11:18 AM   #5  
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First rule of service menus is "write down EVERYTHING before changing ANYTHING!". And before even THINKING about just playing around, understand your can cause your set to stop displaying a reasonable image - which makes it impossible to FIX since you can't SEE the menu. Result: dead TV, expensive service call. Danger, Danger, Will Robinson! (best Robby the Robot voice here).

As Super M's answer suggests, there is another issue when adjusting size with a fixed pixel display like a Plasma or DLP. There is a point when the logical pixels exactly match up with the hardware pixels, called 1:1 pixel mapping. This gives the crispest & clearest display, especially noticable with PC text. But this state may be at odds with the object of seeing the desktop edge & icons lost in overscan... an alternate solution for this case is to use a PC utility called Powerstrip to create a logical screen size of something like 1240 x 680 with standard 1280 x 720 timings. Then Windows will arrange things so everything is within the visible area of your HDTV.
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Old 03-30-2005, 02:59 PM   #6  
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Rbinck --

Side note: If that is a full screen shot of your display, then you may better utilize the empty space by moving your task bar to either sides, left or right, instead of the bottom where it is now. Besides, then you can widen it to whatever width you find best.
I have mine on the left on the 2nd monitor (17") thus freeing more space on the primary(19").
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Old 03-30-2005, 03:34 PM   #7  
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I don't use extended desktop and I prefer to have the width in my applications rather than the height. I don't do any work while on the desktop, so it is just an application launching pad for me. Those were just for overscan illustration purposes.
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Old 04-02-2005, 07:32 AM   #8  
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New member here. This sounds like what i'm experiencing. Since i
have no knowledge of HDTV settings at all, just learning.

I have a westinghouse, model LTV-30w2 (HDTV/PC). It supports 480i,
480P, 720P and 1080i. For PC compatability it says it will support
1280x1024 but recommends 1280x768 (as best). The graphics
card i have will support up to 2048x1536 with no problem but i can
imagine what i'll see on-screen with that resolution.

The HDTV part works\looks great but the PC part leaves something
to be desired. I am an avid flight sims player and having the resolution
set to 1280x 768x32, the screen objects are pretty jagged. Upping
the PC resolution to 1280x1024 forces the screen edges (several
inches) to not show (i assume, higher res would make even more
disappear). I pulled the powerstrip program down but not sure of the
settings i need to mod. Indeed, not even sure if this is a solution.
What i want to do is run (PC mode) in 1280x1024x32 (or higher)
and have the full picture on-screen (viewable) without having to scroll
. Is this possible? If so, how?

thank you,
savagcl
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Old 04-02-2005, 09:12 AM   #9  
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The reason you are getting the scrolling is not overscan, but rather the video driver thinking the resolution of your monitor is smaller than the video resolution of the card. The driver is placing a monitor window over the video memory. What you want is the video to just go out to the monitor and let the monitor scale it to fit the screen. But it would be best to have the resolution set to the native resolution of your monitor, 1280x768. The 1280x1024 mode will not help as the video will have to be scaled to fit your screen.

Ok, you didn't say if you were talking about Microsoft Flight Simulator or some other program, so I will assume for this reply we are talking about the Microsoft Flight Simulator.

First, you may not have the proper .inf file installed for the monitor. This is available at: http://westinghousedigital.com/support/downloads.shtml Make sure you have the proper inf file installed.

Also in reviewing the FAQ file at: http://westinghousedigital.com/support/faq.shtml they talk about needing to get the proper driver installed. If you have a 4:3 driver or inf file it can cause aspect ratio problems.

I ask my son who is another avid MFS fan and he suggested the following. In the Microsoft Flight Simulator there are some various display settings. The one that will affect jaggies is the Anti-Alias setting. If this is set for low you will get jaggies. Also try playing with some of the other filtering settings.

If all else fails you can call Westinghouse support at 1 (866) 287-5555.

Last edited by rbinck; 04-02-2005 at 09:15 AM..
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Old 04-02-2005, 10:02 AM   #10  
My plasma is High Def.
 

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rbinck,
Thank you for the quick response.
I checked with westinghouse (WH for now) and they said those inf
files were not for my unit, that since my unit is plug and play, no inf is
needed. I have the latest Gforce driver for my video card (NV7184)
which is a Gforce 6600 GT w/128 mem mem on board.

"What you want is the video to just go out to the monitor and let the
monitor scale it to fit the screen." How do i do this?

Never thought about the anti-alias but will give it a try soonest and
post back here.

I have played MFS (1, 2 and 3), have others but am partial to Strike
fighters and Wings Over Vietnam (WOV). In particular WOV, since i
got to have a year's vacation in that beautiful country at government
expense, communing with nature and admiring the countryside while
carrying a full pack (thank whoever, i'm retired now).

thanks again for the comeback,
savagcl
(clif)
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Old 04-02-2005, 11:55 AM   #11  
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Default Confused? or maybe not?

I have to admit I'm a bit confused by the whole issue of overscan. I have a Samsung HLP5685, with which I am most pleased. When I connect a computer via a VGA cable (VGA to VGA) and set the tv to "PC" as its source I get three settings under PICTURE size: Wide TV; Wide PC and Expand. There are overscan issues when set to Wide TV, no overcsan issues when set to Wide PC but the picture is stretched horizontally, and in Expand the screen is proportional to the 4-3 screen of the PC monitor. The input is set for 1024 by 768. Anything greater comes back with a black screen with a dialogue box "unsupported input" which is a message from the tv.
I am not a "gamer" per se but enjoy using the TV to "play" World Wind, the NASA interactive program/game. In doing this keeping the screen so the image is proportional is important to me so I have been using the "Expand" setting. I'm pleased with what I see but am curious is this as good as I can get or is it possible to improve the picture? The pixel count per image being fixed at the native resolution of the screen (720), the tv's scaler dealing or accepting the 768 output the computer is presently set at. I can't see where I can get more than I'm presently getting, is that right or am I missing something?

Thanks in advance,
Wiley
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Old 04-02-2005, 10:13 PM   #12  
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The TV settings will have overscan because TV need to overscan to get rid of unused video. The PC setting is what you want.
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Old 04-03-2005, 08:28 AM   #13  
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Expand is the preferred mode, it has 1:1 pixel mapping & small overscan.

What you're missing is you're feeding the display a 4:3 image format, but it's a 16:9 display... You need to set your graphics card to output 1280 x 720 @ 60 Hz. TVs only accept 60 Hz, other rates can do damage. You don't say what make & model graphics card you've got... 720p is a standard selection in NVidia drivers, as is 848 x 480 (16:9 EDTV).
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Old 04-03-2005, 12:17 PM   #14  
My plasma is High Def.
 

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Ok, In PC mode, I have 3 menu settings also - Standard, Fill and
Zoom, all listed under Aspect Mode. I see no difference between the
3 modes at all (i'm using fill right now).

In my graphics card (GeForce 6600 GT with 128 megmem) under
Display>Settings>Advanced>GeForce6600GT>Digital Flat Panel
Settings, there are 4 options:
1. Display Adapter Scaling
2. Centered Output
3. Monitor Scaling
4. Fixed Aspect Ratio Scaling

Of the above, 1 and 4 gives me ragged lines from top to bottom of
the screen (un-readable).
Number 2, cuts off the top & bottom of the screen but is readable.
Number 3, is the one i'm using because it gives me a full screen.

I did get the monitor program and this is an extract (not sure what its
telling tho).

Timing characteristics
VESA GTF support............ Not supported
Horizontal scan range....... 30-80kHz
Vertical scan range......... 50-75Hz
Video bandwidth............. 140MHz
Extension blocks............ n/a
Timing recommendation #1.... 1280x768 at 60Hz
Modeline................ "1280x768" 79.500 1280 1344 1472 1664
768 771 778 798 -hsync +vsync

Same thing for Powerstrip, has a lot of settings but i am unsure what
they mean (and wether or not i can damage something).

Suggestions??

thank you,
savagcl
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Old 04-03-2005, 12:17 PM   #15  
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Default 82810E Graphics Controller

Sorry to not have included that info. I set the regular PC monitor to 1024 -768 which is a 4:3 output (using the slide bar in the settings dialogue box). Then I shut it down and change the monitor to the VGA connecting the Samsung. Then restart, it then displays in 4:3 on the TV (Expand mode") and the settings say "Samsung DLP on Intel(r) 82810 Graphics Controller". Also this computer is running Windows ME if that helps. And in "advanced settings" the "Hardware Acceleration" is set to FULL on the slider; refresh rate set to 60hz (would using "optimal" be a better setting?).
This was a freebie computer that the previous owner had failed to keep up an anti-virus program and the son had visited some sights with some nasty self-replicating porn. It's is a DELL Dimension L600cx and was fine as a starter back in 2000 (only 10 gigs). The machine was two-blocked and it took hours to get it cleared of the problems. I was going to use it to store and display photos on the TV then I found World Wind and want to make the most of it it before replacing with my main PC. I realize the small RAM and fairly slow processor account for the slow action on World Wind with the DELL but wondered if the picture could be improved as well as the action with a better video card. It didn't seem logical that the picture would be improved as one needs the tool bars to run the program and of course one needs to keep the world (and subsequent photos) proportional; thus a 4:3 format.
I'm slowly working my way toward a home theatre, clearing the space at present and then will be building a "room in a room" for soundproofing. I would like to have a PC wireless connected to the system and I am at the low end of the learning curve at present. I have the DELL wireless at the moment. All help appreciated!
Thanks, Wiley
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