One of the big appeals of a DirecTV system is the ability to get programming in HD, or High Definition. It allows you to make the maximum use of a flat screen TV and deliver image resolution much sharper and clearer than that of an old tube TV. But what does HD resolution really mean? And how can you differentiate one type of resolution from another with your programming?
Definition
High definition differs from standard analog TV in the way it is transmitted. The signal is sent digitally, through fiber-optic cables, rather than traditional cables. That allows the signal to contain a great deal of additional information, which turn packs a huge amount of data into a single image. As a result, the picture onscreen lacks the fuzziness and pixelization of older signals, providing a much more detailed viewing experience.
Pixels
Exactly how sharp the image is depends on how many pixels the screen can hold. A pixel is a dot of color, placed in a line along your TV screen. Hundreds of lines are stacked on top of each other on the screen, and as the pixels shift, the image appears to move. Most standard TV tubes hold about 480 lines of pixels. Flat screen TVs have the capacity to hold many more pixels, 720 or 1080 in the high-end models.
Interlaced Vs. Progressive
The second consideration for HD signals is whether they are interlaced or progressive. An interlaced signal broadcasts only half the pixel lines in a given instance, then switches and broadcasts the other half. The naked eye cannot spot the difference--the image looks unified--but the signal often results in the "flicker" effect that many TVs have. Progressive signals, on the other hand, broadcast every line of pixels on the TV, eliminating the flicker. An HD broadcast can thus be defined by a number (representing the number of pixel lines it contains) followed by the letter "p" or "i" determining whether it is interlace or progressive. 720p, for example, is a progressive HD broadcast containing 720 lines of pixels, while 1080i is an interlaced HD broadcast containing 1080 lines of pixels.
DirecTV
DirecTV's satellite service broadcasts signals from hundreds of cable stations into subscribers' televisions. For an additional fee (usually about $10 a month), the signals can be broadcast in HD. That doesn't necessarily mean you can receive the signals in HD, however. For starters, you will need a TV capable of receiving HD. In addition, not all shows are broadcast in HD, meaning that even if you have the right TV, the show will still come in the way it would on an analog set. Finally, some stations are broadcast in different HD resolutions than others--ESPN, for example, is broadcast in 720p on DirecTV, while CNN is broadcast in 1080i. A television only capable of receiving 720 HD resolution will broadcast 1080 signals as 720. (In other words, you're still getting the show, just not as clearly as you could).
Considerations
As of this writing, DirecTV signals do not broadcast in 1080p: the maximum sharpness and clarity. The technology simply doesn't exist yet to send out signals that clearly. (No other dish or cable companies can produce 1080p signals either). Blu-Ray discs and other consumer electronics can broadcast in 1080p, however, and eventually DirecTV will offer shows in that resolution. 1080p television sets can be purchased in anticipation of that time.
