More and more Free To Air satellite viewers are starting to use backend computers that have DVB-S/S2 tuner cards installed, and use backend software such as TVHeadEnd. This allows playback in all rooms of the home, but at each traditional HDTV set you need a computer of some type to act as a frontend. The frontend is then connected to the TV set via a HDMI cable.
Now what you may not realize is that when you do this, or when you use a a more conventional digital satellite receiver with HDMI output, chances are that your TV is not showing you the full picture that the frontend or receiver is sending. In fact, it almost certainly isn’t if you haven’t disabled overscan. What is overscan, you ask? Well, I could now write several paragraphs attempting to explain it to you and why it matters, or I can send you to a very good article at Engadget that explains it much better than I ever could. Since I am a bit on the lazy side, you get one guess which choice I am going to make. Here’s the article:
HD 101: Overscan and why all TVs do it
Here’s another one on the subject from Heron Fidelity:
A Good HDTV Shows You Everything
And one more from HD Guru:
Is Your HDTV Under Performing? Here’s a Fix
Note that this affects more than just satellite reception – it degrades the picture from nearly every digital source that your TV can receive signals from, including non-TV sources such as game machines. Manufacturers leave it enabled because they would rather that some of picture be lost, and the remaining picture a bit less sharp, than to have consumers return TV’s as “defective” because they happen to see a line at the top or side of the screen on one or two channels.
The big problem is that not all sets have a way to turn it off, and some that do hide the setting that turns it off very well. I’ve seen the feature referred to as Overscan, 1:1, Dot by Dot, Just Scan, Exact Fit, Screen Fit, Native, and a few other terms I can’t remember offhand. It might be grouped with the picture size and aspect settings, or it might be in an advanced settings menu, or in some other place entirely. Some manufacturers, such as Vizio, either omit it entirely or include it under a rather non-obvious setting. And I have even come across TV’s where you have to change the way the frontend computer sends the signal to the TV before the option is exposed, such as with certain older Sharp models.
Quite a few of the signals on the satellites nowadays are in glorious high definition, so why would you want your TV to degrade that signal? Find the setting to disable overscan, if your TV has one, and activate it. The only exception to that advice might be if you are primarily watching old TV shows made in pre-digital times, and the uplinker is transmitting the video with the old analog-style closed caption and other control data visible as flashing white and black scan lines at the top of the picture area. There is no really no reason any digital uplinker should be doing that, but I cannot assure you that none of them do it.