Digital Trends

Scan through coverage of the recent Consumer Electronics Show in Las Vegas—a city I loathe with all my heart and soul, but never mind that—and you'll see the mysterious recurrence of four numerals and a letter. By the first day of the show, several manufacturers were boasting that their next-generation video displays would support the 1080p signal format.

The list included not only established brand names like JVC, LG, Samsung, Sharp, Toshiba, and Vidikron but also up-and-coming names like Optoma, Syntax, and Westinghouse—and I've undoubtedly missed a few. Evidently all these companies believe 1080p is the next big thing in HDTV. But what exactly is 1080p and why is it worth bragging about?

Let's cut to the chase: It's the highest of high-definition signal formats, with 1080 vertical pixels by 1920 horizontal pixels, and uses progressive scanning. There are no 1080p signal sources yet—at least, none available to consumers—but it's still handy as a picture-enhancing upconversion format. If you know what I'm talking about, you might as well skip the rest of the column and click on "discuss this article." For the rest of you, I'll generate some more words, as I so often do.

The DTV standard used in the U.S., Canada, and Mexico is named ATSC, after the Advanced Television Systems Committee, the industry-led group that originated it. ATSC allows resolution as high as 1080 by 1920 pixels, but only in an interlaced format. That means the picture is scanned in two passes, or "fields," each lasting 1/60th of a second. The first pass leaves blank spaces between lines, which are filled in by the second pass. Because each field takes 1/60th of a second, and there are two of them, 1080i actually needs 1/30th of a second to convey a full frame—it is a 30-frames-per-second medium. Fixed-pixel displays don't need to use scan lines but approximate the same thing in dots.

The upside of interlaced scanning is that it conserves bandwidth while still providing more than two million pixels onscreen (1080 times 1920 equals 2,073,600). The ATSC adopted interlacing for the 1080-line format specifically to fit over-the-air HDTV into the same 6MHz bandwidth as an analog TV channel (though 1080i also travels via cable and satellite). The downside of interlacing is that it induces motion artifacts and other forms of distortion. The best example would be a horse race. With interlacing, the horses' legs become a blur.