HDTV Information: Interlace Vs. Progressive
Interlaced and progressive are terms that describe the way in which a television image appears on the screen. It is generally considered that progressive results in a smoother, crisper picture. With the speed images appear on television, however, it is questionable if the difference is noticeable with the naked eye.
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Interlaced Explained
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Simply, if you put your fingers on both hands between each other to produce eight "lines," you get a rough idea of lines on a TV screen. An interlaced picture displays the odd lines first--1, 3, 5, 7 and so on. Then, a split-second later, the even-numbered lines--2, 4, 6, 8,etc.--appear to complete the TV image.
Progressive Explained
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Progressive scanning is the display of TV lines sequentially from top to bottom. In true HDTV terms, that is 1920-by-1080 scan lines. All HDTVs are progressive scan.
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The Change in TV Transmission
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In the United States particularly, the old NTSC standard was an interlaced format. The lines per screen were less than 20 percent of high definition resolution. To anyone who grew up with color television, however, it looked pretty good. For anyone who wears glasses, consider HD (high definition) to SD (standard definition) comparable to seeing with and without glasses.
What Changed
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Our way of looking at televised images changed, even before HD was officially the broadcast standard. DVDs introduced higher resolution images than broadcast television. Computer games took this even higher, with resolution better than standard DVDs. Now, Blu-ray disks, along with several video game players, are the very highest resolution, true 1920-by-1080p lines, otherwise known as progressive.
And What About TV Broadcasts?
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The highest resolution currently broadcast, both over-the-air and over cable, is 1080i, or interlaced, because of the bandwidth size of broadcasting the higher resolution 1080p images. The point, going back to the beginning, is that all 1080 resolution images look fantastic, so the fact that one is interlaced and the other is progressive, while both are high definition, is likely noticeable by only the most trained video experts.
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