Don’t mount your TV over the fireplace, it’s not a good idea

When people are setting up their home theater, it’s tempting to mount out TV over the fireplace .These arrangements seem like a great use of spaces, but in reality one of the worst arrangements you can do for both the TV itself and for people own viewing experience.
How it’s bad idea for TV?
First and most, heat and soot generated by the fireplace both can raise the temperature for the TV set. Both things reduce television’s usable life span. If the internal damage is noticeable, the manufacturer can refuse warranty of services. It doesn’t topic, if you want to use the fireplace, but it's looser, if you do it.
It gives pain in the neck
If people are not concerned about the damaging the TV, people will still strain their neck watching it if it’s mounted too high. It would be as similar as you sit in the front row of a movie theater every time you watch TV. We are suggesting here for placing the center of the screen at eye level from our standard sitting position, or even slightly below. An apartment Therapy offers same advice, suggesting that the top of the screen should only be about 15 degrees above from the horizontal plane of vision. By either measure, hanging our TV screen above a fireplace isn't remotely close to an optimal position. In fact, we would be better off mounting it inside the fireplace.
It will hurt your image quality
Most of the LCD and LED still suffering from poor viewing angle problems, so looking at TV from below can destroy your experience. By the reference of experts, most of the LCD suffered from noticeable color shifts less than 15 degrees. Far less than  15 degree angle from your couch to the top of a fireplace-mounted screen. Beautiful designing of our room attracts every one and compel to admire it. People are going to have a small basement too, which will have small family TV room, and that will be the main location for the watching TV. However, they will have a TV in the family room and the most logical place to put their TV.

The technology of LCD has improved something’s in recent years, but unless you have a plasma screen display or an expensive display, you'll never get a vibrant a picture from a  mantle-mounted TV as you would from one at eye level.
Off axis problem
Since most of the people buy LCDs, can’t say why, there is one more problem: most LCDs look significantly worse if you're not looking at TV straight on. Even the few degrees below their centerline like people would have sat on a sofa looking up at the TV can be profoundly different than what it looks like on-axis.
The fixing for this, if you have  set of mounting over the  fireplace, is a wall mount that pivots the TV downward. "Pointing" the TV toward the couch is the one way to ensure picture quality with LCDs.
While plasma TVs are very less reliable than LCDs to off-angle degradation, some have screened filters, like Panasonic's "louver" design, that can also dim the image when seen from extreme vertical angles.
http://www.dynamicmounting.com/