- In this report
- Overview
- What you need to get HD
- Programming in HD
- Transmission in HD
- What TV & tuner?
- A few pointers
ELECTRONICS FORUMS  Get real-world advice from others about choosing a new TV, digital camera, computer or cell phone. |
February 2006
| High-definition (HD) TV: What it is, why you'd want it High definition, or HD, is a high-quality digital TV format that has gained momentum in the past few years. The picture quality is almost photo-like and can be stunning, especially on a large widescreen set. HD signals are capable of containing more and finer detail than standard-definition TV signals, the type we've watched for decades. That's because HD images have higher resolution, meaning there are more elements making up the picture, creating finer detail. It's much the same way that a newspaper photo with many tiny dots looks sharper and more detailed than one with fewer, larger dots. High-definition specs There are several different HD specifications, but two have emerged as dominant. 1080i, an HD format with 1,080 lines that are drawn on-screen in two passes, first the 540 odd lines (1, 3, 5, etc.) and then the 540 even (2, 4, 6, etc.). The two sets of lines are woven together in an alternating pattern called interlaced, hence the i. 720p, an HD format with 720 lines that are drawn onscreen sequentially, in one pass (1, 2, 3, etc.). This sequential pattern is called progressive, hence the p. Neither HD format is inherently better than the other, though proponents of each would argue otherwise. 1080i signals contain more detail, but you get only half the lines with each sweep. 720p signals contain fewer lines, but all the lines are displayed at the same time, which can make for smoother motion. Most HD content is 1080i. A few content providers, including ABC, use the 720p format. Don't worry that your TV will be able to display only one format or the other. HDTVs can display both 720p and 1080i content because they process the signals into a format their screens can display. We're starting to see high-end TVs designed to display 1080p programming, which theoretically will combine the higher resolution of 1080i and the smoothness of 720p. Some microdisplay projection sets and plasma and LCD TVs with native resolution of 1920x1080 are now available. They're sometimes marketed as “1080p” models. There isn’t any 1080p content being broadcast yet—and there may not be for the foreseeable future—but these sets can up-convert current 1080i HD broadcasts into 1080p that’s almost as good as the real thing. And 1080i broadcast movies and programs that are film-based rather than video-based can be converted to true 1080p quality on sets with a feature called 3:2 pulldown. You’ll also be able to get top-quality video with DVDs soon. Today, the best quality you can see with most DVD players is 480p. But when high-definition DVDs and players (using both the Blu-Ray and HD-DVD formats) arrive on the market this year, you’ll be able to enjoy 1080p quality with DVDs. (Depending on the DVD’s format and the capabilities of the player and the TV, it may either be up-converted to 1080p or true 1080p, which can look slightly better.) Other formats It's important to note that not all digital TV signals are high definition. So just because you subscribe to digital cable
doesn't necessarily mean you're getting HD. There are also formats for enhanced definition and standard definition. |
