AACS Advanced Access Control System. A computer specification for guarding next-generation optical-media content created by the film, electronics, and software industries.

AC-3 (see Dolby Digital 5.1)

Aspect ratio The ratio of screen width to screen height.  For TVs it is either 4:3 (1.33:1) or 16:9 (1.78:1).  Theater film uses many different aspect ratios, some as high as 2.5:1.

ATSC (Advanced Television System Committee technical standard)  This is the name of the technology used by terrestrial digital TV stations in the U.S.

BNC connectors These common RF connectors are sometimes found on VGA cables in place of a VGA connector.  They employ a quarter-turn twist-lock mechanism.

Bob and Weave Two processes for de-interlacing (converting interlaced video into progressive scan).  Weave refers to combining successive fields.  Also called interfield, this method preserves the original resolution.  Bob refers to up-converting a field into a frame, in effect creating new lines by averaging the adjacent lines above and below.  Also called intrafield, this method causes a loss of resolution but never causes motion artifacts.  See also Motion Adaptive De-interlacing.

Cable card The Cable Card is the mechanism the industry has adopted to prevent the piracy of cable services.  The cable company will periodically mail out new cable cards, ask their customers to plug them into the TV, and then disable the old cards, so anyone without a new cable card would lose service. If you want the simplicity that comes with the cable receiver being integrated with the TV then you should buy a TV with a cable card slot.  However if you like TiVo then you would instead get a DVR, which will have its own cable card slot.

C-band / Ku-band 1.  a range of RF spectrum. C-band is app. 4 GHz.  Ku-band is app. 12 GHz.  2.  Geo-stationary satellites the networks use to acquire and distribute programming to affiliates and cable TV companies.  These satellites use C-band and Ku-band frequencies.  3.  a consumer service that uses the satellites the networks originally set up for themselves.  An 8-foot steerable dish is required.  Some channels are free.  Others are available by subscription.  The digital channel subscription service is called 4DTV.

COFDM modulation technique This technical standard has been used in Europe and other places for digital TV.  8VSB is used in the U.S.

Color temperature This describes how white is displayed.  Low temperature means slightly reddish, while high temperature means slightly bluish.  Standard NTSC white corresponds to the color a glowing hot object would be at 6500° K

Comb filter A circuit in NTSC sets that separates the color information from the brightness information.

Component video This 3-wire convention was created for connecting DVD players to TVs or monitors.  It avoids downgrading the signal to NTSC.  The signals may be RGB or YPrPb.  Some HD STBs have only component video output.

Composite video This 1-wire standard contains all video information: intensity, color, and sync.  The encoding is the same as NTSC, and thus has the “overlapping sideband” problem which sometimes causes wrong colors to appear.

Convergence An adjustment that must be made occasionally to CRT sets.  This adjustment makes the three colors coincide perfectly.

DBS (direct broadcast satellites)  These satellites are powerful enough to be received by an 18 inch dish.  They use Ku-band frequencies.  Companies that provide DBS services to consumers in the U.S. are DirecTV and Dish Network.  Canadian DBS providers are Star Choice and Bell ExpressVu.  Also called DSS.

D-ILA (Direct-drive Image Light Amplifier) (see LCOS)

DirecTV (see DBS)

Dish Network (see DBS)

DLP (digital light processor).  A technology for video projection, also call DMD (Digital Micro-mirror Device).  It is a large chip with about a million tiny mirrors on its surface.  The chip can tilt each mirror to vary the amount of light reflected off of it.

Dolby Digital 2.0 This is a two channel (stereo or Pro Logic) version of Dolby Digital.  It is often used by DBS systems.

Dolby Digital 5.1 Also known as AC-3, it provides 6 channels of sound: left, center, right, left rear, right rear, and sub-woofer.  It is also called “5.1 channels” since the 6th channel has reduced bandwidth.  Dolby Digital 5.1 is the audio standard for all U.S. digital TV stations, most DVDs, some DBS programs, and many theaters.

Dolby Pro Logic Surround This is a 4-channel analog system.  During recording, the 4 channels are “folded” into 2 stereo channels.  If played back without a Pro Logic decoder, it sounds like normal stereo.  This format is becoming obsolete.

DTCP (Digital Transmission Content Protection)  This is an encryption standard for IEEE 1394 that prevents the copying of first-run movies and pay-per-view events.  DTCP is also called 5C Copy protection (in reference to the ‘five companies’ that license it).

DTS An alternative to Dolby Digital.  ATSC does not use DTS but some DVDs do.  Most audio receivers that work with Dolby Digital also handle DTS.

DTV (digital TV).  Examples of DTV are DBS satellite services, digital cable TV services, and ATSC digital TV stations.

DTVLink This logo is on equipment that has IEEE 1394 and DTCP.

DVB (Digital Video Broadcasting)  An alternative to ATSC used in most of the world outside the U.S.  It has three different standards:

·        DVB-T is for terrestrial (OTA) broadcasts.

·        DVB-S is for satellite broadcasts.

·        DVB-C is for cable broadcasts.

DVI (Digital Visual Interface)  This connector conveys HDTV image scanning signals in binary data form.  The data rate is very high (1.65 Gb/s).  Binary data is preferred by monitors that are not CRTs.  DVI comes with a decryption option called HDCP which will decode encrypted programs such as first-run movies.

EDTV (enhanced definition TV)  Essentially DVD quality, it is a small step up from NTSC.  An EDTV will convert all 18 ATSC formats to 480p.

FCC (Federal Communications Commission) This is a Federal agency responsible for regulating radio wave usage and some other media.  The FCC answers to Congress and also implements international radio standards.

Fire-wire (see IEEE 1394)

First-surface mirror Normal mirrors have the silvering on the back surface of the glass.  First surface mirrors have it on the front.  Cleaning a first-surface mirror must be done very carefully.

FTA “Free To Air” or “Free To All”.  This is a digital satellite technology employing MPEG-2, but it is not compatible with DSS systems (Dish or DirecTV) or with Motorola Digicipher II (C-band 4DTV) and it doesn’t have a provision for encryption.  At the present time there are no high definition stations on FTA. lists all the stations.,, and others sell receivers.  The frequencies used are Ku-band and C-band.  FTA’s forte is that it is cheap and very international.  FTA is heavily used outside the U.S.  FTA started becoming popular in the U.S. about 2002 among experimenters and immigrants.  In the opinion of some people the rise of FTA is a mistake and HDTV might eventually kill it.  It might survive in the U.S. market because of a need for an unregulated domain for international stations.

GLV (Grating Light Valve)  This is another contender to replace CRTs in projection TVs.

HAVi (Home Audio Video Interoperability)  This is a standard for 1394 bus audio and video devices.  It is software that is required for the units to talk to each other.  HAVi allows plug-and-play recognition of devices, interoperability, and brand independence.

HDCP (High-bandwidth Digital Content Protection)  This is a DVI decryption option.  It will decode encrypted programs such as first-run movies.  (Its real function is to prevent unauthorized copying of programs.)

HD-Capable TV A standard definition set with a digital tuner.  (This term was probably invented to confuse people.)

HD-Ready TV An HDTV monitor or TV that lacks a digital tuner.

HDMI (High-Definition Multimedia Interface)  This miniature connector is intended to replace DVI.  It is backward compatible with DVI, and an adapter will connect it to a DVI unit.  It has 19 pins and carries DVI plus digital audio. It also has a control line that allows the STB to sense the monitor’s state and native formats.

HDTV (High Definition TV)  A TV that displays 1280×720 pixels or better.

IEEE 1394 Also called Firewire or iLink.  Originally a serial bus for PCs, 1394 may or may not become the interconnection standard for DTV products.  It is competing with DVI.  IEEE 1394 is a spec for a hardware interconnect plus a software shell.  But additional software, such as HAVi, is required for connected units to actually talk to each other.  Some day 1394 may dramatically simplify the way DTV products interconnect. (see IEEE 1394)

Interlaced scan Historically, TV CRTs are interlaced, while computer CRTs are not.  Interlaced means that the electron beam skips every other horizontal line, filling in the missing lines on the next pass.  A frame is composed of 2 fields.  One field is all of the odd numbered lines, and the other field is all of the even numbered lines.

Jack A female connector.

LCD (Liquid Crystal Display)  A common display technology.  LCD is likely to replace CRTs in the smallest HDTV’s.

LCOS (Liquid Crystal On Silicon)  This is another contender to replace CRTs in projection TVs.

LFE (Low Frequency Effects)  Sub-woofer.  The 6th channel in a 5.1 channel system.

Line Doublers This device converts NTSC or 480i into 480p.  Line doublers with motion-adaptive processing can to an extent turn a 30 frames/sec image into a 60 frames/sec image, thus removing some of the jerkiness and blurriness associated with motion.

LNB (Low Noise Block converter)  An LNB can be found at the focus point of a dish antenna.  It is a low noise amplifier that also converts the signal to a lower frequency.  (The original higher frequency would not travel very far in ordinary coaxial cable.)

Motion Adaptive De-interlacing The image is divided into regions where there is motion and where there is none.  Areas of the image without motion are de-interlaced using “weave”, and areas with motion are de-interlaced using “bob”.  See Bob and Weave.

MPEG-2 (Motion Picture Experts Group technical standard 2)  This is a widely used standard for digital encoding of motion pictures.  It typically achieves a 50 to 1 compression of data. It achieves this mainly by not retransmitting areas of the screen that have not changed since the previous frame.

MTS (Multi-channel Television Sound)  This refers to an analog NTSC TV equipped with stereo and SAP (separate audio program) features.

Multipoint convergence Projection TVs with 3 CRTs require periodic adjustment to keep the 3 images perfectly aligned.  Typically this is a simple 5 minute procedure the consumer must do every month or so.

Multi-path interference Some neighborhoods are plagued with this problem:  The signal finds more than one path to the antenna.  Multi-path results from reflections off of buildings and diffraction around the sides of hills.  For NTSC sets this will result in ghosts: multiple images shifted laterally.  For DTVs the result can be an unusable signal, even though it may be strong.  The solutions are moving the antenna or selecting a very directional antenna.  Newer generations of DTV receivers are better able to cope with multi-path.

Must-Carry This refers to the legal obligation of cable companies to carry analog or digital signals of over-the-air local broadcasters.

Native format Some DTVs will convert the 18 ATSC formats into 1 or 2 formats and will draw only those.  For these sets, the ‘native’ format is  1.  the formats the set will draw or  2.  the original format.  (These are contradictory definitions, but they reflect current practice.  1 is probably the preferred meaning.)

NTSC (National Television System Committee technical standard)  This is analog TV invented in 1946.  NTSC has 525 lines (483 visible) interlaced, 60 fields per second.  This standard is in use in North America, Japan, South Korea, Burma, Taiwan, the Philippines, and much of South America.

OAR (original aspect ratio)  Also called Letterbox format, OAR means that none of the image is clipped or squeezed.  Unused parts of the screen are usually black.

OTA (over the air)  There are about 1500 OTA (terrestrial) TV stations in the U.S.

Over-scan/Under-scan Computer CRT monitors under-scan, which means they leave a thin black border around the image.  TVs over-scan, which means a small part of the image perimeter is lost.  (Digital displays don’t necessarily do either.)

PAL (Phase Altering Line standard)  This alternative to NTSC has 625 lines, interlaced, 50 fields per second. It is used in most of Europe, Asia (except USSR), Africa, and Australia, and parts of South America.

Pan-and-scan A method of broadcasting a wide screen film on a 4:3 channel.  Most of the time just the center of the image is shown.  (The right and left edges are clipped off.)

PCM (Pulse Code Modulation)   This 2-channel digital audio standard is simpler than Dolby Digital.

Plug A male connector.

Progressive scan This is the opposite of interlaced scan.

PSIP data (Program and System Information Protocol)  This data is arranged as a table with multiple sub-tables.  The data identifies the station name, what the sub-channels are, the program name, the following programs, content advisories, language options, and caption options.  Some of this data is transmitted as often as 7 times per second.

PVP-OPM Protected Video Path Output Protection Management. Downgrades computer video resolution or blocks the picture entirely if the connected display doesn’t support content protection.

PVP-UAB Protected Video Path User-Accessible Bus. Encrypts video content as it passes over the PCI Express bus from the high-def disc to prevent other PCI Express devices from intercepting the video stream.

Raster A group of closely-spaced lines whose brightness changes so as to appear to be an image.

RGB 1.  red-green-blue  2.  a 3-wire standard (See component video)  3.  a 5-wire standard (See VGA.)


SDTV (standard definition TV)  SDTV is 480i, which is approximately the resolution of NTSC and DVDs.

SECAM (Sequential Color And Memory standard)  This alternative to NTSC has 625 lines interlaced, 50 fields per second.  It is used in the former USSR, France, and parts of Eastern Europe, the Middle East, and Africa.

SPDIF (Sony/Philips Digital Interface)  This is digital audio, and can be either coaxial cable or fiber optic.

STB (Set Top Box)  These include satellite receivers, cable TV receivers, OTA receivers, and various recording devices.

Sub-channels OTA DTV stations can show multiple programs simultaneously, subject to the 6 MHz bandwidth limit.  This is called multicasting.


S-video Also called Y/C, this two-wire standard keeps the color separate from the intensity signal, and thus avoids the overlapping sideband problem of composite signals.  (Converting an NTSC signal to S-video gains you nothing since what was lost cannot be recreated.)  Although the quality of S-video is close to component video, S-video cannot transport anything better than 480i.

Symbol rate The symbol rate for ATSC is 10.76 million symbols/sec.  8VSB has 3 bits/symbol.  After the error correction bits are removed the net  transfer rate is 19.28 million bits/sec.

THX 1.  a standard that theaters try to meet.  2.  equipment to help theaters meet that standard.

Toslink A fiber optic cable standard.

Transponder A satellite channel.  There is often one program per transponder.  Some transponders are wider than 6 MHz and can carry more than one NTSC program.  Several digital channels can fit on one transponder.

VGA a 5-wire standard interface, originally for computer monitors, now common for HDTV monitors.  Usually the 5 wires are in one cable.  The connector can be either a 15-pin connector or five BNC connectors.  The signals are usually red, green, blue, horizontal sync, and vertical sync.  But Y, Pr, and Pb can replace the colors.

Virtual channel number This is the channel the consumer thinks he is watching.  The actual (physical) channel is selected by a hidden mechanism.

YCrCb Almost identical to YPrPb.  If you connect a YCrCb unit to a YPrPb unit you might have to adjust the color slightly.  YCrCb is an older standard uncommon for consumer connections.

YPrPb Color representation requires three independent variables.  CRTs  prefer red, green, and blue.  Ink jet printers prefer yellow, magenta, and cyan.  NTSC encodes color as luminance (brightness), hue (color), and saturation (absence of white in colors).  Storage media such as DVDs prefer Y, Pr, and Pb, where Y is luminance, Pr is red-Y, and Pb is blue-Y.  This is because Pr and Pb can be at lower resolution and not degrade the image noticeably, thus saving storage space.


3:2 pull-down This is the process of converting a 24 frames/sec image into a 30 frames/sec image.  Some line-doublers will reverse this process to acquire the original, and then re-perform it.

4DTV This is a DTV subscription service for C-band and Ku-band (a satellite service requiring an 8 foot dish).

5.1 channel This is 6 channel audio.  The 6th channel (the sub-woofer) has reduced bandwidth.

5C Copy Protection See DTCP.

8VSB modulation technique (8-level vestigial sideband)  DTV stations in the U.S. use 8VSB modulation.  This is an AM mode wherein the carrier is multiplied by an 8-level digital signal, and then a filter is used to remove all but the carrier and 6 MHz of the upper sideband.  (“8VSB” is often used as a synonym for OTA.)