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Lesson 2: HDTV primer

HDTV Hardware
HDTV: High-definition television. High-resolution digital television broadcast and playback system composed of roughly a million or more pixels, 16:9 aspect-ratio screens, and AC3 digital audio. A subset of digital television, HDTV formats include 1080i and 720p resolution.

• What's HD and What's Not HD: A digital television (DTV) is not necessarily HDTV. Not all flat-panel TVs qualify as HD either. So how can you distinguish real HDTV from the other stuff? Start with the dots and lines that form the picture.
• Pixels, Lines, and Native Resolution: A DTV picture is made up of dots called pixels, or picture elements. Most DTVs are fixed-pixel devices with grids of vertical and horizontal pixels. The pixels are delivered in lines, or horizontal rows of pixels, scanned from the top of the screen to the bottom. Specify those two numbers, the vertical and horizontal pixels, and you've got native resolution.
• More Pixels: HDTV: High-definition television (HDTV) has the highest native resolution in DTV, producing pictures with either 1080 by 1920 pixels (about two million total) or 720 by 1280 pixels (just under a million). Both are true HDTV. Anything with fewer than 720 vertical pixels or 1280 horizontal pixels is not HDTV--though it might be EDTV or SDTV.
• Less Pixels: EDTV and SDTV: A picture with 480 vertical pixels and 640+ horizontal pixels (more for widescreen) is either enhanced-definition television (EDTV) or standard-definition television (SDTV), depending on whether it uses progressive or interlaced scanning (see below). These formats are suitable for casual (not home theater) viewing in screen sizes of 27 inches or less.
• Do I Need to Worry About Analog Compatibility? No, any digital set you buy will convert all analog and digital signals to its own native resolution.

More Distinctions

• Widescreen vs. Non-widescreen: Contemporary movies and some TV programming have screen proportions (called aspect ratio) of 16:9. Older movies and most other TV programs have narrower proportions of 4:3. Using common denominators, that's 1.78:1 vs. 1.33:1. Your display may adjust automatically or manually. It's more visually coherent to have blank bars at top/bottom or left/right than to stretch the image.
• Progressive vs. Interlaced Scanning: Each frame in the picture may be scanned in either one pass or two. Progressive scanning, used in PC monitors and some DTVs, delivers a whole frame. Interlaced scanning, used in some digital and all analog TVs, divides each frame into a pair of gap-toothed fields that knit together. This is more efficient but also introduces distortions called motion artifacts.
• ATSC vs. NTSC: The incoming digital TV standard is known as ATSC, named for the Advanced Television Systems Committee, the standard-setting body that created it. The outgoing analog TV standard is NTSC, named for the National Television Systems Committee. DTVs have an ATSC tuner to receive digital channels over the air. Usually they have NTSC tuners to receive analog channels as well.

What Kind of HDTV Is Right for You?

• I Want It Flat and I Want It Big: For screens of 42 inches and up, the best choice is the plasma panel. It has better black level and off-axis uniformity than LCD flat panels. On the downside, it's also subject to the "screen-door effect"--with more noticeable spaces between pixels.
• I Want It Flat But Not as Big: For screens of 42 inches or less, the LCD (liquid crystal display) offers a smoother picture, with more tightly packed pixels. The downsides are price, more grayish blacks, motion smear, and limited viewing angle.
• I Want the Best Picture for the Lowest Price: Rear-projection sets using a trio of red, green, and blue CRTs (cathode ray tubes) boast a winning combination of resolution, black level, and seamlessness. Tubes are video's gold standard. The downside is that they make for a bulky set.
• I Want to Save Both Money and Space: Rear-projection sets that replace tubes with newer microdisplay technology slim down the cabinet's depth. DLP projectors reflect light off chips full of micro-mirrors that open and close to produce each pixel. LCD projectors (including the D-ILA and LCoS types) reflect light off liquid-crystal panels. The downside: a sacrifice in picture quality compared to tube-based sets.
• I Want the Biggest, Baddest Picture on the Block: Then a front-projection system is for you--because when you separate the projector from the screen, you can have a much larger screen (and a smaller projector). The choices are the same as in rear-projectors: CRT, DLP, or LCD. Consider a high-quality screen part of the cost.

Additional tips for buying digital televisions (DTV)

• Integrated digital televisions (DTV) vs. DTV-Ready Monitors: This older terminology distinguishes between DTVs with or without tuners that receive ATSC (digital) channels. Today anything called a DTV is presumed to have an ATSC tuner. Unfortunately, many still don't, so watch out for these terms. A DTV with out a tuner isn't necessarily useless for everyone since you don't need a tuner to receive DTV via satellite or cable.
• Digital Cable Ready Digital Television (DTVs): DCR sets with CableCARD slots can decrypt copy-protected cable signals with a card from your cable company. Some cable systems don't support the card, so ask before buying. Cable-ready sets also have QAM tuners that handle nonencrypted bottom-tier channels (such as network affiliates) without need for a card.
• HDMI and IEEE 1394: These next-generation digital cables provide a better picture than analog interfaces like component video, S-video, and composite video. HDMI can carry both video and audio and is akin to a USB for Home Theaters.

1394 (AKA FireWire) is suitable for recording and networking (with certain limitations).

• Other Attractions: Some sets have built-in satellite tuners, hard-drive-based recording capability, or Internet browsing.