Entering the World of HDTV
Since the transition to color TV in the 1950s and ’60s, 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 — a lot of TV programming is still all-analog, for example. And this stage of the game can be confusing, with an alphabet soup of acronyms, changing technologies, and emerging standards.
Oh, say, can you ATSC?
More than 50 years ago, 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, there have been some changes in those 50 years (such as the addition of color), but today’s analog TVs are built on this NTSC system.
In the 1980s, the ATSC (Advanced Television System Committee) was formed to move TV forward. Many years later (1996), the ATSC’s recommendations for a digital-television system were adopted by the FCC (Federal Communications Commission — the folks who set standards for TV broadcasts, regulate phone companies, and fine Howard Stern). ATSC standards use newer-than-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 filmlike images with no video flicker
- All digital, with none of the “ghosts” and other image problems found in analog TV
Understanding video standards
HDTV (and digital TV, or DTV, in general — there are some digital TV variants that are not high-definition, and we discuss them in this section) 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. 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.
There are three essential concepts to understand when you are 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 will appear.
- Resolution is defined by one of two factors:
• Lines (the number of left-to-right lines the TV can display). CRT-based TVs (tube TVs) are rated this way.
• Pixels (the number of pixels across the screen times the number up and down). Fixed-pixel displays (plasmas, LCDs, DLPs and the like) are rated this way.
- Scan Type comes in two forms:
• 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.
• 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).
- Aspect Ratio (the shape of your TV picture):
• Traditional TVs have a 4:3 aspect ratio (screen shape). 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 will be 9 inches high.
• 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.
There isn’t a single “HDTV” standard out there. Instead, ATSC contains many different TV standards (with different resolutions, aspect ratios, and scan types) — 18, in fact. Some of these standards are truly HDTV; most are not. In the real world, you will deal with four standards when you try to watch TV content on your HDTV. The two primary HDTV standards are these:
- 720p: This provides 720 lines of resolution with progressive scan (hence the p). By comparison, NTSC has less than 480 lines of resolution. 720p uses a 16:9, a widescreen aspect ratio.
- 1080i: This variant (the highest resolution within the ATSC standard) uses interlaced scanning, but provides 1080 lines of resolution. 1080i is also widescreen, with a 16:9 aspect ratio.
There is actually a higher HDTV variant in the ATSC standard — 1080p, which is a progressive scan variant of 1080i. Only a few HDTV projectors (in the $40,000 and above price range) can handle this variant, and we know of no material that is broadcast or otherwise available as 1080p. So don’t worry about it.
True HDTV performance requires at least 720p performance. If a TV program, movie, or other content is not 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 and 1080i are the two HDTV standards, but you’ll also find a lot of digital TV material will be 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 will make this programming look better than it does on a regular TV — but remember: That stuff is not really HDTV.
- 480p (EDTV): This enhanced-definition TV standard provides higher-than-NTSC resolution, with progressive scan (NTSC is interlaced). EDTV can be (and often is) 16:9 widescreen, but it is not 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 will often be in the product descriptions; you need to know exactly what you’re buying.