The broadcast industry is moving toward conversion of our system to High Definition Television (HDTV), a conversion which presumably will be complete sometime in this decade. This is good news. HDTV is better than EDTV, and much better than regular TV for two reasons. First, it increases the number of scan lines on the screen, so you get much more picture clarity and detail. Second, it gives you a wider picture that looks more like a movie theater screen rather than the old, almost square TV.
So how many more scanlines do you get? Well, there are two popular HDTV formats in use. One is called 1080i, and the other is 720p. But don't worry, there are no format wars to worry about. All digital projectors and digital HDTVs take both formats. The fact is that ABC, ESPN, and Fox broadcast in 720p, while CBS, NBC, HDNet and others use 1080i. Both formats produce great pictures that are a leap forward over regular television. And you will never know the difference. If you are watching Everybody Loves Raymond in high definition on Monday night, and you flip to ABC to see what is happening on Monday Night Football, your projector or HDTV will automatically switch from 1080i to 720p without you even knowing it. All you will be aware of is that both channels look a lot better than they used to with an amazingly clear and detailed widescreen picture.
For those who want a bit more technical explanation, we can say that both formats feature the widescreen 16:9 aspect ratio that defines HDTV. However, the 1080i format has 1080 lines for each frame of video, whereas the 720p format has 720 lines. A lot of people think 1080i is preferred because it has more scanlines, and thus is capable of more picture detail. However, since there is so much data in the 1080-line format, each frame must be separated into even and odd lines and broadcast a half frame at a time in interlaced format, just like the current TV broadcast system. This can introduce the same type of artifacts as we see today, but they are smaller and less noticeable since there are so many scanlines.
The alternative HDTV format is 720-lines progressive scan, or 720p. Though it has fewer lines, the native progressive scan format eliminates motion artifacts that originate in interlacing. So for subject matter that contains a lot of rapid motion—NFL Football for example--you can get a clearer, more stable picture from 720p than you can from 1080i. Alternatively, for subject matter that has very little motion, 1080i is capable of rendering more picture detail.
The truth is that 1080i and 720p are both excellent HDTV formats. One is not better than the other; they are just each better with particular types of subject matter. When done right, both are clearly superior to the 480-line format we have today. And best of all, you will never have to worry about it because your projector or HDTV will sort it all out for you anyway.
2007-09-16
02:52:49
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5 answers
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lee b
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