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Discussion Starter · #1 ·
I am watching MyHD on a Mits 65" RPTV connected via a rgb breakout cable. The HTPC is using a Radeon LE set @ 960x540 via powerstrip for the desktop. At this resolution there is the expected overscan (I can just barely see the top of the taskbar) that can be taken out by running 920x500 within 960x540 timings. The problem that I am running into is that when viewing MyHD in full screen (set to 1080i) I seem to lose even more of the picture to overscan than with the default HD timings. When watching 48Hours (I only get one channel of HD) the CBS logo was clipped in half horizontally. Nothing I could set in the MyHD app seems to affect this.

Now the questions;

Has anyone else noticed this?

Is something setup incorrectly (I just left the MyHD setup @defaults)?

Any ideas on how to reduce the overscan in MyHD?

Would switching the MyHD to PYRb affect this?


Any insights would be appreciated (I just spent the weekend putting a antenna in the attic, three floors up from the HTPC and would really like to relax and enjoy the results).


Thanks...
 

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Unfortunately, the imo "right" way to fix overscan is at the display (assuming the sources don't violate the standards for sync and blanking position and duration). The bad news is that RPTVs tend to have weak ability to compensate for the non-linearity of sweeps that results when overscan is minimized. (For better control of linearity, extra circuitry is required. Say, like in a 5- or 10-year-old FP CRT that you might find from someone like Curt Palme for a fraction of its original price.)


Also, each scan format (480p, 480i, 1080i) requires its own careful adjustment. Thus, it's not surprising at all that you're getting different results from different sources.


The good news is that part of the full calibration process is to fix the convergence, so you'll probably end up with a *much* nicer looking picture than what the factory provided.


If you don't have the skills and confidence to do this yourself, contact a high-end video retailer in your area (or ask in these forums) for a reference for a tech who can help. Remember, though, you're gonna have to pay a professional for a full day's work, most likely. That means it won't be cheap, but you're already in for a pound, so throw in some pennies, too.


When I had my set calibrated, I felt like the improvement over the uncalibrated performance was almost as much more than the performance of the set when it arrived over my old NTSC set. Unfortunately, convergence drifts, and it's necessary to tweak it from time to time to maintain image quality. (You'll start seeing red and green edges around sharp black-white boundaries. That means it's time to go to the setup menus.)


Enjoy.


-yogaman
 

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Quote:
When watching 48Hours (I only get one channel of HD) the CBS logo was clipped in half horizontally.
48 hours is not broadcast in HDTV. Is your CBS affiliate possibly broadcasting standard-def programming in some type of cropped 14:9 or 16:9 resolution, or do you have black bars on the side for 4:3 material? If 4:3 programming fills your screen and doesn't have bars on the side, then what you're seeing is not overscan; it's just the way your affiliate is broadcasting. My CBS affiliate does the same thing, and it's pretty annoying to have part of the top and bottom cropped.
 

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In my case, solving one overscan problem creates another. I am currently using 3 separate RGB sources to feed my Philips RPTV, a DTC-100, a Hipix card and a Radeon 32DDR video card with Powerstrip (for DVD's). Soon, I will add the MyHD card as well. Each device has slightly different T&R characteristics at 540p/1080i that create different overscan and underscan conditions.


Trying to find common calibration settings on the set with minimum tweaking is a chore. I do some slight adjustments in the setup menu for different sources, but too much adjustment can easily throw off the convergence. If there were only a Powerstrip program for the Hipix card and the DTC-100....... ;)
 

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I have also had interesting results when switching between devices.


The screen was distorted when switching between my DTC-100 doing 1080i and the MyHD card doing 1080i.


My workaround is to adjust 1080i for the DTC-100, and use the MyHD card in 720P mode. So, my display (Sampo 34" HDTV) is adjusted for both display formats.
 

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â€The screen was distorted when switching between my DTC-100 doing 1080i and the MyHD card doing 1080i.â€


Please describe how the screen is distorted. Without full disclosure we have no way of knowing what to look for or how to fix it.
 

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Discussion Starter · #7 ·
My TV shows approximately 5% overscan on all edges when playing the AVIA DVD via the Radeon @ 1920x1080i. When viewing the MyHD output it appears that there is 10% horizontially and 15% vertically. I could try to adjust this out with the service menu but the TV has only one memory associated with HD and I watch alot more DVD's than network TV.
 

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â€My TV shows approximately 5% overscan on all edges when playing the AVIA DVD via the Radeon @ 1920x1080i. When viewing the MyHD output it appears that there is 10% horizontially and 15% vertically. I could try to adjust this out with the service menu but the TV has only one memory associated with HD and I watch alot more DVD's than network TV.â€


First question is where did you get a transport stream image that can be used to test ATSC overscan?


It sounds like the setting for Aspect Ratio is set for Zoom with the Auto radio button unchecked. I just checked by unchecking Auto and selecting Zoom and got about the same amount of excessive overscan as you reported for 1080i.
 

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Quote:
Originally posted by Cliff Watson
â€The screen was distorted when switching between my DTC-100 doing 1080i and the MyHD card doing 1080i.â€


Please describe how the screen is distorted. Without full disclosure we have no way of knowing what to look for or how to fix it.
The distortion was just the type where you change to a new resolution that your monitor is not adjusted for, and the picture doesn't go to the edges of the screen, and is "warped" on the edges.


At first, it looked like my monitor would only store one config for 1080i, but after adjusting it for both a couple times, it appears to store both the DTC-100 1080i settings and MyHD.


I was just a bit surprised because I thought 1080i would be the same for both devices.
 

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Discussion Starter · #10 ·
To guesstimate the overscan I place an object on the edge of a scene when in overlay mode and then switch to full screen. While I realize that this is not 100% accurate it is the best I have until somebody points me to a stream test pattern. I have the Auto box checked and set to letterbox. I think that JKohn it correct about the 48Hrs because I haven't seen anything that extreme again. I have done some more research in other forums and have found that there is a very wide range of timings being driven by various set top boxs, in other words I am not the only one to see this effect nor is it limited to the MyHD board. If it becomes too much of an issue I'll probably try to reduce the overscan via the service menu on my set again. Overall I am extremely happy with my purchase and would certainly do it again.


Thanks,


Michael
 
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