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HDTV Technology Background

Publication Type: Miscellaneous Publication
Date: 4/1/2006
Overview

While much has changed in television over the last 25 years, the essential look and sound of the medium – referred to as analog – has largely remained the same. Digital television (“DTV”) is a general reference to a new all-digital system where programming is produced, transmitted, and received digitally. DTV is also is an umbrella term given to TV sets and monitors that can receive and display the various digital formats.

High-Definition Television (HDTV) is the highest resolution format of digital television. Standard-Definition (SDTV) is a lower resolution digital television format.

HDTV differs from Analog TV in several key ways:

  • HDTV has higher resolution: The image on a digital television is made up of small elements called pixels. The pixels in HDTV are closely packed together to provide high-resolution detail. HDTV can have 1,280 or 1,920 active horizontal pixels by 720 or 1,080 active scanning lines respectively. The total number of pixels in a high-definition image can exceed two million.

  • HDTV has a widescreen format: In addition to providing improved picture quality with more visible detail, HDTV is transmitted in a widescreen display commonly referred to as a 16:9 format, meaning that the picture is 16 units wide by 9 units high. A conventional analog TV display is 4 units wide by 3 units high, or 4:3 (see diagram below). Thus, the 16:9 display provides a wider image area that more closely matches the relative dimensions, or aspect ratio, of cinema.

  • HDTV has better sound: Many HDTV programs also contain multi-channel (5.1) Dolby® Digital surround sound to complete the realism of the viewing experience within a home theater system.

    • Digital Television Sets & Monitors

    Two tiers of DTVs – HDTV and SDTV – differ in the number of pixels they display on the screen. A high-definition display must be capable of displaying 1,080 active lines using interlaced scanning (1080i) or 720 active lines using progressive scanning (720p) on a screen with a 16:9 aspect ratio. By comparison, a standard-definition display must, at a minimum, be capable of displaying 480 active lines using interlaced scanning in at least one of two aspect ratios, 16:9 or 4:3.

    Demonstration of aspect ratio

    Some digital television sets may provide the tuning and digital decoding functions built into the device to offer an integrated, one-product solution. Other sets are only capable of displaying the HDTV or SDTV programming and require a separate receiver/tuner or set-top box to receive the digital signal.

    Digital television sets and monitors incorporate different display technologies, including direct-view (the cathode ray tube style most of us are familiar with), front or rear projection, and plasma.

    How to get HDTV

    There are several components required to watch a program in high-definition.

  • The program must be transmitted in high-definition. Viewers can receive HDTV signals through one of three ways: over-the-air broadcast, cable or direct broadcast satellite.

  • At the consumer’s home, the signal must first go through a receiver/tuner. Some HDTV sets now have receivers/tuners built-in, while other times the receiver/tuner is sold separately. Cable subscribers who receive HDTV programming do so by means of an HDTV set-top box.

  • The program must be viewed on an HDTV set. If consumers have a separate receiver/tuner – either over-the-air, cable or satellite – they can receive and view HDTV programming on an HDTV monitor. Some HDTVs incorporate an integrated receiver/tuner.

    • What is the difference between “digital cable” and “HDTV”?

    For today's digital cable programming, digital set-top boxes translate the digital signals for display on conventional analog television sets. In contrast, HDTV has a much higher level of resolution and must be received on a digital television set capable of displaying HD.

    What kind of equipment do I need to receive HDTV?

    You will need to purchase a digital television capable of displaying a high-definition signal, which uses either the 1080i or 720p format. Most high-definition digital televisions will display these formats. In some digital television sets, the digital decoding and tuning functions are built into the TV. Other instances require a digital monitor, capable of displaying HDTV, plus a tuner in a separate set-top box. When receiving HDTV from cable, an HD set-top box may be purchased at a retail outlet or leased from the cable operator, depending on the local cable system.