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Old 07-14-2012, 06:21 PM
 
Location: Texas
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Default What is cause of occasional pixelation on TV?

It doesn't happen a lot, but it is a bit annoying.
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Old 07-14-2012, 06:59 PM
 
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Pixelation is a side effect of data rate compression techniques peculiar to digital image (especially television) systems. Images are (oversimplified) cut up into groups of 64 pixels that can appear, disappear or move quickly, and each of the 64 pixels in the group changes far more slowly if your eyes are able to pay attention to the detail.

Were it not for compression, a single high-definition TV service could take up the entire over-the-air TV band, or half of all the bandwidth an RG-6 cable could carry.

Now, if the transmission were to be interrupted or corrupted, you would be missing the data for some of the pixel groups. The imaging hardware and software will show these blocks in the same place, even if the rest of the scene is moving or even if the scene has changed (a jump-cut), and you may see a set of skyscraper windows in the shape of a person's face (for example).

Pixelation can be expected if the signal is too weak to decode, affected by interference, or by multipath (echoing). When TV was analog, these would usually be perceived as snow, wavy lines, or ghosting, respectively.

Problem is, with digital, the difference between a signal that produces a perfect picture and a pixelated mess can be very small, and you can actually have a very poor (unreliable) signal and think it is perfect. In analog, one could see the imperfections easily and could more easily correct the problem causing the poor picture.
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Old 07-14-2012, 07:53 PM
 
Location: East of Seattle, originally from SF Bay Area
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Where are you getting your service from? We had that problem and it turned out to be the crappy Comcast cable box.
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Old 07-14-2012, 08:07 PM
 
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It's almost certainly the TV service, and I've seen it on all of them. Dish, DirectTV, various cable services. I've seen it much less on OTA, when decoded by an ATSC tuner in the TV, but it still happens. Not much you can do about it beyond making sure you're receiving the best possible signal you can.
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Old 07-15-2012, 11:23 AM
 
Location: Texas
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Quote:
Originally Posted by Hemlock140 View Post
Where are you getting your service from? We had that problem and it turned out to be the crappy Comcast cable box.
Ours is Sudden Link. I don't know what the area coverage is.
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Old 07-15-2012, 11:35 AM
 
Location: Texas
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We have everything bundled with the same service. Sometimes my computer is slower than it should be. Right now, it's very fast, though I'm sure many people are at work now.
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Old 07-15-2012, 08:51 PM
 
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Does it happen when it rains or high humidity in the air? Does it happen on one TV or multiple TV's?
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Old 07-15-2012, 11:47 PM
 
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Could be something as simple as a faulty cable or poor signal caused by splitting it incorrectly or too much. These boxes have a diagnostic panel in them that usually requires you to hit a specific sequence of buttons on the box to access it, once you get in there it should tell you the signal strength.
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Old 07-16-2012, 10:24 AM
 
Location: Texas
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Quote:
Originally Posted by NeilVA View Post
Does it happen when it rains or high humidity in the air? Does it happen on one TV or multiple TV's?
We only have one big TV. I hadn't paid any attention to the humidity, though. Maybe I'll keep a log.
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Old 07-16-2012, 10:25 AM
 
Location: Texas
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Quote:
Originally Posted by thecoalman View Post
Could be something as simple as a faulty cable or poor signal caused by splitting it incorrectly or too much. These boxes have a diagnostic panel in them that usually requires you to hit a specific sequence of buttons on the box to access it, once you get in there it should tell you the signal strength.
Come to think of it, I don't even know where the box is. I'll take a look. I may just go to the company and ask them point blank.
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