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For Dummies is a registered trademark of Wiley Publishing, Inc. in the United States and other countries. Used here by license.Since the transition to color TV in the 1950s and ’60s, nothing — nothing!! — has had as much impact on the TV world as HDTV (high-definition TV) and digital TV. That’s right. TV is going digital, following in the footsteps of, well, everything. We’re in the early days of this transition to a digital TV world (a lot of TV programming is still all-analog, for example), and this stage of the game can be confusing. In this article, we alleviate HDTV anxiety by telling you what you need to know about HDTV, ATSC, DTV, and a bunch of other acronyms and tech terms. We also tell you why you’d want to know these terms and concepts, how great HDTV is, and what an improvement it is over today’s analog TV (as you can see when you tune in to HDTV). Finally, we guide you through the confusing back alleys of HDTV and digital TV, making sure you know what’s HDTV and what’s not. Almost everyone involved with HDTV has noticed that consumer interest is incredibly high with all things HDTV! As a result, a lot of device makers and other manufacturers are trying to cash in on the action by saying their products are “HDTV” (when they are not) or talking about such things as “HDTV-compatible” when it might be meaningless (like on a surge protector/electrical plug strip). Be on the lookout for such interlopers and insist on true HDTV functionality.
ATSC?A long time ago (over 50 years ago — longer than even Danny has been alive!), in a galaxy far, far . . . errr, actually right here in the United States . . . a group called the NTSC (National Television System Committee) put together a group of technical specifications and standards that define television as we know it today. Sure, some changes have been made in those 50 years (such as the addition of color), but today’s analog TVs are built on this NTSC system. Fifty years is a long time for any technology to dominate. Indeed, technologies and components used in television-transmission systems, cameras, recording systems, and display systems (the TVs themselves) have long been capable of doing something more. In the 1980s, the ATSC (Advanced Television System Committee) was formed to move TV forward. Many years later (1996), the FCC (Federal Communications Commission — the folks who set standards for TV broadcasts, regulate phone companies, and fine Howard Stern) adopted the ATSC’s recommendations for a digital-television system. ATSC standards use newerthan- 1953 technology to give you TV like you’ve never had before:
Widescreen images like those in the movies
Greater detail — up to six times more detail
Sharper images
Smoother, more film-like images with no video flicker
All digital, with none of the ghost images — where you see a translucent version of the image on your screen, slightly offset — and other image problems found in analog TV Please note that ATSC is not the only game in town when it comes to digital TV and HDTV. In most European countries and in many other parts of the world, the DVB (Digital Video Broadcasting) standard applies. (Terrestrial, cable, and satellite variants exist, noted by a -t, -c, or -s appended to the DVB.) In Japan and a few other countries, there’s a system known as ISDB (Integrated Service Digital Broadcasting). These systems all use different mechanisms to encode (or digitize and compress) video signals for transport over the airwaves, over a cable, or via satellite. The impact here is that the device you use to tune in your HDTV signals differs depending upon your country. Regardless of which system is in use where you live, the important thing to you as a viewer is the picture itself, and that’s where HDTV is truly a universal phenomenon. HDTV pictures contain two to six times more picture detail than older analog standard-definition systems (again, this is true regardless of which country you’re dealing with). This extra detail lets you display your TV content on a bigger screen and still see a great picture. You also see more vivid colors, a wider screen presentation, and the increased picture quality enabled by digital transmission. No more ghosts and snowed-out pictures — digital is usually either a great picture (most of the time) or essentially no picture at all (on those rare occasions when you don’t have a good enough signal). Throughout this book, we focus on the U.S.-based ATSC system, but our real focus is on the HDTV formats we’re about to discuss, such as 720p and 1080i, which apply no matter where you live and no matter how your TV is delivered to you.
Powerful Performance
HDTV is all about giving you a bigger and better picture, better audio, and generally making your TV-watching experience more like a movie-watching experience. (Digital TV, or DTV, in general also does the same thing, but some digital TV variants are not high definition, and we discuss them in the following sections.) In fact, at its best, HDTV is so realistic that it’s often described as “looking through a window” — as if you’re really there, not just watching a program.
Video standards
In this section, we discuss the characteristics of the HDTV programming itself (be it broadcast over the airwaves, over cable, via satellite, or saved on a hard drive or optical disc). There’s a related category of the display characteristics for HDTV — meaning what your HDTV can actually show you on the screen. Many HDTVs can accept different types of HDTV signals and then transform them into the resolution, aspect ratio, and other such formats that work best on the HDTV display itself. You need to understand four essential concepts when comparing different video standards:
Resolution: The number of individual picture elements that make up a TV image. The higher the resolution, the more detailed the image and the sharper the image. Resolution is defined by one of two factors:
1) Lines: The number of left-to-right lines — counted vertically, like a stack of pancakes — the TV can display. CRT-based TVs (tube TVs) are rated this way.
2) Pixels: The number of pixels across the screen times the number of pixels up and down. Fixed-pixel displays (plasmas, LCDs, DLPs, and the like) are rated this way.
Scan type comes in two forms:
1) Interlaced scan: These TV images are created by lighting up every other row of horizontal lines on the screen in one instant and then going back through and lighting up the remainder of the lines in the next instant. It happens so fast that your eye can’t really tell it’s happening. In an interlaced system, these groups of lines (each consisting of half of the picture) are known as fields.
2) Progressive scan: These systems light all the horizontal lines in the same instant, which can make the image seem “smoother” and more like film (or real life). In progressive scan, this grouping of all the lines is called a frame. Two interlaced fields combined together equal one full frame.
Scan rate is the measure of how often a picture is redrawn on the screen, measured in terms of the number of fields (for interlaced scan) or full frames (for progressive scan) that are drawn on the screen per second. In the United States, this is typically either 30 or 60 times per second (often called hertz). In European markets, it’s often 50 hertz. Movies themselves are usually filmed at 24 frames per second, which then must be converted to 50 or 60 during the process of turning film into video.
Aspect ratio (the shape of your TV picture):
1) Traditional TVs have a 4:3 aspect ratio. This means that for every 4
units of measure across the screen, you have 3 units of screen height.
For example, if the screen is 12 inches wide, it’s 9 inches high.
2) HDTVs have a 16:9 aspect ratio — which makes the screen relatively much wider for the same height, compared to a 4:3 TV. Most movies are widescreen (16:9, or even wider), so HDTVs can display most movies without the annoying letterbox black bars on the top and bottom of the screen. Don’t get bogged down in up-front technical explanations of these concepts now.
HDTV standards
There isn’t a single HDTV standard out there. Instead, digital TV systems contain dozens of different TV standards (with different resolutions, aspect ratios, and scan types and rates). Some of these standards are truly HDTV; most are not. In the real world, you deal with three primary formats that are considered true HDTV:
720p: This provides 720 lines of resolution with progressive scan (hence the p). By comparison, NTSC has less than 480 lines of resolution. In pixel terms, it has a resolution of 1,280 across by 720 vertically. 720p uses a 16:9 widescreen aspect ratio. You can find 720p in HDTV broadcasts and also in recorded HDTV content like HD DVD and Blu-ray discs.
1080i: This variant (the highest resolution within the ATSC standard) uses interlaced scanning but provides 1,080 lines of resolution. In pixel terms, 1080i fills your screen with 1,920 pixels across by 1,080 vertically. 1080i is also widescreen, with a 16:9 aspect ratio.
1080p: The big dog in the HDTV world is 1080p, which provides the same number of pixels or lines as 1080i but does it in a progressive scan fashion, so all 1,920 x 1,080 of those picture elements are redrawn each time your screen is refreshed, rather than only half per refresh. Today, 1080p is found only in recorded HDTV formats such as Blu-ray and HD DVD. If you see 720i listed as an option, don’t believe it. Either it’s a typo for 720p, or someone is trying to fool you. No broadcast standard permits 720 interlaced lines in a video frame at any frame rate. True HDTV performance requires at least 720p performance. If a TV program, movie, or other content isn’t at least 720p (either 720p or 1080i), it is not HDTV. If a TV can’t display at least 720 lines of resolution, it is not HDTV-capable. If a salesperson tries to tell you that an inexpensive plasma set, regular DVD, regular digital cable, or regular satellite TV is HDTV just because it’s digital, it’s not so.
Compatible DTV standards
720p, 1080i, and 1080p are the three main HDTV standards, but you can also find a lot of digital TV material that is broadcast at lower resolutions that don’t quite make the grade as HDTV. You can still watch this programming on your HDTV. In fact, most HDTVs make this programming look better than it does on a regular TV, but remember: This stuff is not really HDTV:
480p (EDTV): This enhanced-definition TV standard provides higherthan- NTSC resolution with progressive scan (NTSC is interlaced). EDTV can be (and often is) 16:9 widescreen, but it isn’t required to be widescreen.
480i (SDTV): This is interlaced, non-widescreen (4:3), standard-definition TV, equivalent to NTSC analog broadcasts. Remember these different terms — HDTV, EDTV, and SDTV — when shopping. They often are in the product descriptions; you need to know exactly what you’re buying.
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For Dummies is a registered trademark of Wiley Publishing, Inc. in the United States and other countries. Used here by license.