DTV Primer

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Or, a Parade of ACRONYMS

Updated July 3, 2006

480i, 480p - Vertical scan lines (top to bottom) for standard definition TV, or alternatively, number of rows of pixels in the screen. "i" designates interlaced scanning and "p" designates progressive scanning. In a widescreen TV, there would be 704 pixels in each of the 480 rows. Total pixels = 337,920.

720p - Vertical scan lines for minimum high-definition TV. Progressive scanning is only option for 720 HD. 1280 pixels across in each row. Total pixels = 921,600. Generally displayed at 60 frames per second.

1080i, 1080p - Vertical scan lines for uber high-definition TV. Either interlaced or progressive scan. 1920 horizontal pixels. Total pixels = 2,073,600, or six times more detail than standard definition. Generally displayed at 30 frames per second.

5.1, 6.1, & 7.1 channel sound - Multi-channel audio formats. The ".1" part is the subwoofer channel, or LFE (low frequency effects). Broadcast high-definition TV is presently capable of only 5.1 audio, although a rear channel can be derived by some A/V receiver/processors. DVDs and especially next-gen high-def video discs are capable of encoding a discrete rear channel. In 7.1 channel systems, the two rear channels carry the same audio signal.

8-VSB - Vestigial Sideband Modulation with 8 discrete amplitude levels - this is the modulation protocol specified in the digital ATSC TV standard for over-the-air broadcasts (or how the TV signal is encoded in radio waves and then received and decoded inside your TV set).

ATSC - Advanced Television Systems Committee, Inc., is an international, non-profit organization developing voluntary standards for digital television. The ATSC member organizations represent the broadcast, broadcast equipment, motion picture, consumer electronics, computer, cable, satellite, and semiconductor industries. Formed in 1982.

ATSC digital television standard describes the system characteristics of the advanced television (ATV) system, adopted by statute in 1996 as the U.S. TV standard. The system is modular in concept; the FCC adopts ATSC recommendations for amendments and additions to the ATSC standard from time to time.

Bit-rate (or data rate) - the rate a digital data stream (containing the video and audio of the TV programming) is transferred from source to display device. One channel of high definition over-the-air TV is limited to about 19 Mbps (mega-bits per second). By contrast, a standard DVD uses video and audio data at a rate of about 5 or 6 Mbps.

Blu-Ray Disc - One of two next-generation high-definition video discs competing to replace DVDs. Its backers are headed by Sony. Dual-layer Blu-Ray Discs hold 50GB of data.

CableCARD - a card-like device that contains security codes and algorithms that can be plugged into a properly equipped digital TV, permitting the reception of premium cable programming without the need for a set-top-box. Generic name for this device is "POD" - point of deployment security module.

CEA - Consumer Electronics Association - the companies that build TVs

CERC - Consumer Electronics Retailers Coalition - the companies that sell TVs

CRT - Cathode ray tube. Traditional TV technology. Special metal is heated and gives off electrons which are accelerated by a positive electrical grid and aimed with magnetic fields at the inside of the TV tube, which is coated with phosphors. The electrons strike the phosphors and cause them to glow. TV!

Conventional Definition Television - the analog NTSC television system display (480i).

D/A - digital to analog

D-ILA - Digital direct drive image light amplifier (a variation of LCD rear projection TV technology)

DLP - Digital Light Processing - a TV projection technology (front and rear) that uses a small chip containing an array of tiny moveable mirrors, usually equal in numbers to the pixels in the display (for some 1080p displays, each micro-mirror may light up two pixels, one at a time).

Dolby Digital Plus - next generation high bit-rate wideband audio standard from Dolby Laboratories, adopted for high-definition video discs

DTS-HD - next generation high bit-rate wideband audio standard from Digital Theater Systems, adopted for high-definition video discs

DTV - digital television

DVD - digital versatile disc

DVI - Digital Visual Interface - interconnect protocol for transferring video data in digital form (input/output jacks and the cable for connecting them). DVI interconnects permit use of High-bandwidth Digital Content Protection (HDCP) anti-piracy coding. DVI is being replaced by HDMI, which carries both the video and audio parts of TV programming.

EDTV - enhanced-definition television is a term not defined by ATSC. It is rather a marketing term used by the consumer electronics industry to mean a digital standard definition TV (that is, one only capable of displaying 480 lines of resolution, progressive scan). The term is apparently used to distinguish those digital sets from NTSC analog sets capable of displaying 480 lines of resolution, interlaced scan. The latter is properly termed "conventional-definition" TV. When buying any TV, check for the maximum number of lines the set if capable of displaying. 1080 or 720 is high-definition, anything less is not.

HDCP - High-bandwidth Digital Content Protection - A protocol that makes it harder to make illegal copies of protected high-definition programming.

HD-DVD - One of two next-generation high-definition video discs competing to replace DVDs. Its backers are headed by Toshiba. Dual-layer HD-DVDs hold 30GB of data, less than Blu-Ray Discs, but can be produced using existing DVD production technology.

HDMI - High-Definition Multimedia Interface - Advanced digital interface that supports HDCP and the next-gen audio standards. HDMI interconnects carry both digital video and digital audio components of TV programming. You want HDMI inputs on any new television you buy (two would be good) and HDMI outputs on DVD players, etc.

HDTV - High-definition television provides significantly improved picture quality relative to conventional (analog NTSC) television and a wide screen format (16:9 aspect ratio). The ATSC Standard enables transmission of HDTV pictures at several frame rates and one of two picture formats; these are listed in the top two lines of the table below. The ATSC Standard also enables the delivery of digital sound in various formats.

ATSC Digital Television Standard Video Formats
Vertical Lines Pixels Aspect Ratio Picture Rate
1080 1920 16:9 60i, 30p, 24p
720 1280 16:9 60p, 30p, 24p
480 704 16:9 & 4:3 60p, 60i, 30p, 24p
480 640 4:3 60p, 60i, 30p, 24p

Interlaced - Old TV scan technology inherited from NTSC television. Odd-numbered lines are scanned first, and then even numbered lines. One complete video frame consists of an odd-line field and an even-line field. Each field takes 1/60th of a second; one frame takes 1/30th of a second.

LCoS - Liquid Crystal on Silicon. Variation of LCD technology.

LFE - Low Frequency Effects, typically 20 Hz to around 80 Hz low frequency sound routed to the subwoofer.

MPEG - Moving Picture Experts Group - develop standards for compressing digital video streams into fewer bits and lower data rates - MPEG-2 standard is used for broadcast TV - MPEG-4 is a more advanced scheme that will become the standard for high-definition programming delivered via satellite.

MSO - multiple system operator cable system operator. The largest are Comcast Corporation, Time Warner Cable, Cox Communications, Charter Communications, Adelphia Cable, and Cablevision.

MVPD - Multi-channel Video Programming Distributor - cable and satellite companies (eg. Time-Warner, Comcast, DirecTV)

NTSC - National Television Systems Committee - group formed in the early 1940s to develop a U.S. television standard, reactivated in the early 1950s to modify the standard to include color. Also refers to the standard created by the committee.

OLED - Organic Light Emitting Diode (or Display) - new flat-panel technology expected show up commercially in TVs by 2007-08. Potential for excellent video quality. Eventually may be produced in flexible plastic panels which could be incorporated in clothing, for example.

POD - point-of-deployment security modules, more commonly known by consumers as CableCARDs.

Progressive - modern TV scanning technology in which horizontal lines of picture elements are scanned sequentially top-to-bottom, completing a frame in one pass. ATSC standards allow for three progressive frame rates: 60 per second, 30 per second, or 24 per second (or alternatively, rates that are very close to these even numers).

PSIP - Program and System Information Protocol - a collection of tables describing virtual channel attributes, event features, and other information, that is transmitted along with the video and audio signals. Also used for program guide information.

QAM - Quadrature Amplitude Modulation - digital cable tuner technology, not the same as the 8-VSB tuners used for over-the-air broadcasts. "Digital Cable Ready" TV sets will have both QAM and 8-VSB tuners built in.

RF - radio frequency - electromagnetic waves in the frequency range intially used for radio (back before there were TVs and cell phones). Visible light and X-rays are examples of electromagnetic waves that are outside of the RF range.

SCTE - Society of Cable Telecommunications Engineers

SDTV - standard-definition television is a digital television system in which the quality is approximately equivalent to that of NTSC. Also called standard digital television.

SED - Surface-conduction Electron-emitter Display - flat-panel display technology developed by Canon and used by Toshiba for larger televisions starting around the end of 2005. CRT-quality with faster response and lower power consumption.

TFT - thin film transistor (as contrasted to super twisted nematic LCD) - type of liquid crystal technology used in more advanced LCD flat-panel displays.