What is HDTV?

Everyday we hear more and more about HDTV. Watching your local channels such as ABC, NBC, CBS and FOX you might have noticed that all of these stations now broadcast is HDTV. So what exactly is HDTV or High Definition TV and why is it better than the broadcast signals of the past.

Basically High Defintion means the signal is transmitted from the source at a higher resolution. This also means that the video has to be initially captured with a higher resolution. Television signals up until recently have always worked on a analog signal. With an analog signal a 6 MHz analog (as opposed to digital) signal carries the information needed to display the images onto your television. In the USA all analog signals have 525 scan lines for an images. Now these scan lines are refreshed every 30th of one second which is fast enough for the human eye not to notice the changes. Along with this the analog signals are interlaced which means that have of the lines change every 16th of a second and then the other half change and the following 16th. The horizontal resolution for analog signals on regular televisions is comparable to a computer display with a resolution of 640X480 pixels or basically 525 lines of resolution.

Now for the past 10 years or so we have all heard about Digital TV, Digital Cable or Digital Satellite signals. These digital signals provided a clearer and more detailed picture than the old analog signal could because more information can be transmitted over a digital signal. HDTV is just a very high detailed digital signal capable of producing images with resolutions up to 1080 lines of resolution. This is almost double the resolution we have been viewing for the last 70 some odd years. But HDTV does not have to have 1080 lines of resolution.

There are 3 formats currently available for HDTV:

720p : 1280 x 720 pixels are progressively scanned(all pixels change at the same time as opposed to interlaced where half are changes then the other half)

1080i : 1920 x 1080 pixels are interlaced

1080p: 1920 x 1080 pixels are progressively scanned (this format offers the most detailed image)

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