Exploring HDTV - dummies

By Danny Briere, Pat Hurley

You can buy an HDTV (high-definition TV) for well under $500 these days, so unless your budget is tight, you should make an HDTV-capable display the centerpiece of your home theater. With HDTV broadcast programming becoming commonplace, and HDTV Blu-ray discs also hitting the market, there’s plenty of great HDTV content to watch on your big screen.

HDTV is a subset of ATSC technology. ATSC signals can be divided into different groups, depending on the signal’s resolution and the scanning method. They are further divided into:

  • SDTV (standard-definition television): These signals are about the same or a little better than NTSC (analog). Note: A related category here is EDTV, or enhanced-definition television, which is essentially a widescreen version of NTSC.

  • HDTV (high-definition television): The latest and greatest: HDTV has truly spectacular picture quality.

Within the ATSC standard are eighteen SDTV, EDTV, and HDTV variations, but you’re most likely to see just six, as shown in the following table.

Digital-TV Variants
Name Resolution Scanning Method Quality
480i 640 x 480 Interlaced Standard definition (SDTV); same as NTSC
480p 640 x 480 (normal) Progressive Standard definition (SDTV)
480p 720 x 480 (widescreen) Progressive Enhanced definition (EDTV)
720p 1280 x 720 Progressive High definition (HDTV)
1080i 1920 x 1080 Interlaced High definition (HDTV)
1080p 1920 x 1080 Progressive High definition (HDTV)

To take advantage of all the benefits of digital TV, you need a high-definition-capable television and a TV tuner that can decode the ATSC signal. That tuner can be inside the display (just as most TVs have analog NTSC tuners), it can be in a separate tuner component, or it can even come inside a satellite TV receiver or cable set-top box.

Traditional televisions don’t have the internal circuitry to decode digital TV signals, and they generally don’t have screens that can display high-definition ATSC pictures in all their glory. Traditional TVs aren’t even the right shape. The aspect ratio of HDTV signals is wider than that of NTSC signals. NTSC is 4:3; HDTV is 16:9.

This diagram shows the difference in aspect ratios. The HDTV screen has an aspect ratio like the elongated screens in movie theaters.