Originally Posted by robnix
Originally Posted by sawfish
The downside is that TV is meant to be overscanned. I have numerous channels that display junk (sometimes flickering) along the top edge when WMC is configured for "Television". My local NBC HD channel displays a bright white pixel in the upper left corner at all times. So, I leave WMC set to "Flat Panel", which hides this noise like any STB would, and it's fine, because I use it only for Recorded TV. I use XBMC for everything else, and it is configured with zero overscan, so I get the 1:1 pixel mapping for everything I watch in XBMC. Using two programs like this means no compromising on settings or tedious flipping back and forth between settings. (The TV of course is set to Full Pixel at all times.)
That white line is the old SD VBI signal. Google it, what it is and why you get it when you watch old SD shows on HD channels is pretty interesting.
Again, the bright white pixel in the upper left corner on my local NBC HD channel is always present, including during all HD shows like Law & Order SVU, Smash, Parks & Recreation, etc. Examining a screen shot in a paint program, it's actually a line of about 10 gray pixels that starts with a bright white one that's easily visible under normal viewing conditions. For whatever reason, NBC doesn't fill the full frame along the top, leaving a black bar about 10-15 pixels tall, and it displays this junk along the top edge. I've also seen other top-of-the-frame glitches on other HD channels in HD content, but it is more rare. Of course, whenever they switch to SD content, it's often there. (This is with my HD Homerun Prime Cablecard tuner, but I remember seeing the same thing a few years ago with Clear QAM when I first learned about the "Flat Panel" vs "Television" difference. It was this that made me abandon the "Television" experiment and go back to "Flat Panel", which is what I had always used, Nothing has changed since then.)
My take on it is that broadcast TV is meant to be overscanned, and you're not going to lose anything valuable by letting it work as designed. In fact, when you disable it, besides the top-line glitches, banners and scoreboards in various programs appear weirdly shifted into the interior of the picture, talking heads are smaller, and so forth, and everything just looks a little off. I suppose eliminating scaling might make some programs a tiny bit sharper, but I don't know that it's observable under normal conditions. Assuming you keep your TV in its Full Pixel mode, the only thing you really gain by eliminating overscan in WMC is the ability to show DVDs, MKVs, and whatnot in WMC without overscanning them, which is actually desirable and proper. I suppose people who care about this and want to use WMC for everything will simply have to put up with whatever glitches it reveals in their broadcast TV. Fortunately, I'm able to use WMC just for broadcast TV and XBMC for everything else, so I get overscanning for broadcast TV, while I get 1:1 pixel mapping for DVDs, MKVs, etc, including somewhat ironically, TV shows distributed in those formats, where the failure to overscan isn't a problem. (FWIW, this was not one of the reasons I started using XBMC. It's just something I realized after using XBMC for a while.)