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LaserLand's Home Theatre Glossary

Absorption  The dissipation of sound energy into another form of energy (typically heat). When a sound wave encounters resistance, from an obstacle such as a wall, absorption occurs. Absorption is measured in sabins (after Wallace Clement Sabine). A Sabin is the amount of absorption provided by one square foot of open air. One square meter of absorption is called a metric sabin.

Absorption Co-Efficient  The portion of energy absorbed when a sound wave strikes a material. The absorption coefficient of a material is dependent on the frequency of the sound wave. An absorption co-efficient of 1.0 = total absorption, 0.0 = total reflection. These co-efficents are used to rate acoustic materials' capabilities.

AC  Alternating Current. The periodic change in direction of the flow of electrons. The rate of change is known as frequency and is measured in Hertz (Hz: cycles per second). Standard wall outlets supply alternating current.

AC Line Conditioner/Protector  A device that filters noise from the AC powerline and isolates equipment from voltage spikes and surges.

AC3 (Audio Codec 3). This was the original and more technical name for Dolby Digital - a data compression method developed by Dolby Laboratories. To market a more brand friendly name it was replaced by Dolby Digital. Initially RF modulated, 5.1-encoded laser discs were labeled as AC3; subsequent releases bore the name Dolby Digital. (see Dolby Digital)

Acoustic (or Air) Suspension  A type of loudspeaker system that utilizes a sealed enclosure.

A/D; Analog-to-Digital Converter (ADC)  Circuit that converts analog (varying amplitude) signal to a digital (pulse type) signal. 

Amplification  An increase in signal level, amplitude or magnitude.

Amplifier  A device which increases the level of signal (by increasing the voltage or current).

Amplifiers
1. Pre-amplifier  The first stage of an amplification system, which boosts the amplitude of a weak signal from a source (tuner, turntable, tape deck or CD player). It also may provide for tonal adjustment so that the signal may be fed into a power amplifier. Usually contains all audio controls.
2. Power Amplifier  The second or final stage of an amplifier system, which regulates and increases low-level signals received from the preamplifier and feeds them to speakers.
3. Integrated Amplifier   A component that combines a preamp and power amp in a single unit. An integrated amp combined with a tuner in a single unit is called a receiver.

Analog  An electrical signal whose frequency and level vary continuously in direct relationship to the original acoustical sound waves. "Analog" also may refer to a control or circuit, which continuously changes the level of a signal in a direct relationship to the control setting.

Analog vs. Digital  With analog recording and playback, a parameter such as the width of a movie soundtrack, the magnetic field on recording tape, or the side-to side swings of the groove on a phonograph record varies in a way that is directly in relation to the sound waves of the original sound. These variations are translated to a varying electrical voltage, which ultimately causes the loudspeaker's cones to move back and forth, recreating the original sound.
With digital recording and playback, points along the sound waves of the original sound are assigned numeric (or digital) values, which are represented as microscopic pits on CDs and DVDs, magnetic pulses on tape, or microscopic dots on a digital movie soundtrack. When the recording or soundtrack is played back, the numeric values are converted back to the varying electrical voltage needed to drive the speakers.
Digital soundtracks can be very high quality, but take up much more room than analog. Sophisticated techniques of sampling and compression, such as Dolby Digital are used to make multi-channel digital recording viable.

Anamorphic Presentation  Many DVDs and some TV or satellite broadcasts may "unsqueeze" an anamorphic signal to display a widescreen image utilizing the highest vertical resolution possible on a widescreen monitor or TV. For recording or broadcasting purposes, a wide image is squeezed horizontally. Unsqueezing is done by 'stretching circuits' in the TV. Should your TV set not be a widescreen format, or you have not set your TV to detect anamorphic signals, people in these images will look tall and unrealistically thin.

Anechoic  An acoustical setting without sound reflections; not having or producing echoes; free from echoes and reverberations - as in a completely enclosed room with wall/floor/ceiling coverings that absorb sound frequencies.

Aspect Ratio  The width to height ratio of an image or picture on a film or TV screen. The NTSC standard is 4:3 (4 units wide to 3 high, or 1.33:1) while the HDTV screen standard is 16:9 (1.78:1). Movie films range that includes 1.33:1, and 1.66:1 through 2.4:1 with 1:78, 1.85:1 and 2.35:1 being the most common. (also see widescreen or letterbox)

Audio Direct  When playing CDs in a conventional DVD player, the audio signal is routed through the video circuit even though there isn't an image being displayed.

Audio Mixer  A unit that combines or blends several sound inputs. 

Band  A range of frequencies between two definite limits. Broadcast bands are assigned by the CRTC in Canada and FCC in the U.S.A.

Band Pass Filter (BPF)  A circuit, commonly having inductance and capacitance, that effectively passes a given range of frequencies, while frequencies above and below this range are attenuated.

Bandwidth  The range of frequencies, expressed in Kilobits per second, that can pass over a given data transmission channel. The bandwidth determines the rate at which information can be sent through a channel - the greater the bandwidth, the more information that can be sent in a given amount of time. Usually measured in bits-per-second. A full page of English text is about 16,000 bits. A 56Kbs modem can easily move 16,000 bits in less than one second. For audio/video bandwidth, frequencies are expressed in thousands of cycles per second (KHz) or millions of cycles per second (MHz).

Biamping  Incorporating more than one power amp plus a crossover network for woofers and tweeters.

Bipole Speaker  One type of speaker commonly used for surrounds. In this loudspeaker, two or more drivers face in opposite directions with their cones vibrating in phase, creating an omni-directional sound.

Biwiring  Connecting an amplifier to speakers using separate cables for woofers and tweeters.

Blu-ray Disc (BD) uses Blue Laser technology having a much shorter wavelength than the red laser technology used in current DVD. Blu-ray employs a disc the size of a standard DVD disc, but with much greater storage capacity sufficent to hold an entire film at HDTV resolution or allow two hours of high definition video content to be recorded. Single-layer (25GB) - Dual-layer (50GB)

Bypass  An alternate signal path that goes around a given circuit. A "hard wire" bypass uses a switch and a piece of wire to route the signal from the input to the output of a device. A "bypass" switch is sometimes called an "in-out" switch.

CDR/MP3 
- CD-R  Compact Disc Recordable discs have become a popular way of storing your own music or video images onto a CD. With a CD recorder ("burner"), you can choose the specific music to be recorded onto a CD-R disc. CD-R discs are playable. Some content recorded via PC may not be compatible with certain DVD/CD players.
- MP3  MPEG Audio Layer 3 is a digital compression format that allows compression of regular music tracks onto a CD-R. With MP3 compression, one CD-R disc can store up to 100 music tracks on a single disc. This gives you the ability to store an immense number and variety of MP3 music tracks onto one CD-R. Number of music tracks will vary depending on the length of each track and bit rate. The 100-track approximation is based on 128kbps at an average of five minutes per track.

Clipping  is a circumstance where an amplifier cuts off the peaks of a signal when too little amplitude is available to meet the peak demand. In a high volume situation, if an amplifier is unable to handle the signal without clipping, a condition called compression may occur where the high frequencies may overdrive the power handling capability of a tweeter and cause it to blow.  With today's amplifiers, you may not hear the distortion at moderate clipping levels until the stress on the tweeter has blown it. The best protection against this destructive problem is an amplifier fitted with a clipping protection circuit, which switches off the speaker output immediately if clipping should occur.  Normally, higher powered amplifiers are less likely to go into clipping mode.

Crossover Frequency  In a multi-driver loudspeaker system, the sound signal is split to send the higher frequencies to a high frequency driver such as a tweeter, while the lower frequency portion goes to a lower frequency driver such as a mid-range or bass driver. The circuitry that enables this frequency split is called a crossover, and the frequency at the split is the crossover frequency.

CRT Projector  A type of projector which throws the image onto the front of a projection screen. It consists of three cathode ray tubes (CRTs) each putting out one color: red, green, or blue. They offer brightness and excellent picture detail, but require some expertise to set-up and align, and convergence may be required about two or three times a year.

Digital-to-Analog Converter (DAC)  A circuit that converts digital signals to analog (varying amplitude) signals.

Decibel (dB) Unit of measure for sound. A logarithmic expression of the relative loudness of sound.

De-interlacing  The complex process that converts a traditional interlaced video source into the progressive scan format required by high definition displays. Some de-interlacing processors are better than other at reducing noisy artifacts and motion blurs. If the objects in the video image are not moving, it is very easy to de-interlace as the two fields can be weaved together and combined to form a complete frame. If an object in the video has moved in the fraction of a second it takes to go from one frame to another, simply combining fields causes the errors in the image called “combing” or “feathering” artifacts. A low level frame-based motion-adaptive computation may be used by the processor to lessen the artifacts or in better processors a pixel-based motion-adaptive algorithm may detect and correct for motion pixel by pixel.

Digital Light Processing (DLP) generates images by reflecting light off the surface of a digital micromirror device (DMD) containing hundreds of thousands of tiny mirrors, then through a color wheel and a lens and onto the screen. Higher resolution projectors have more mirrors in their DMD's, reflecting a greater amount of light for brighter images. Today the CRT projector will still outperform the DLP in terms of picture detail, but the slight sacrifice in detail and dark level may be outweighed by the relative ease of set-up and convergence (transportability).

Digital Micro-mirror Device (DMD)  A mirror that is very small that can be kept as is or tilted x amount of degrees in order to reflect light. As such, it is either on or off. It can be turned on and off at various rates per second to achieve different levels of brightness. Commonly used together to form micromirror "wafers" and are controlled by a Digital Light Processor (DLP).

D-ILA  (Direct-drive Image Light Amplifier) JVC's reflective liquid-crystal technology used in high-resolution displays. A variant of LCoS.

Dipole Speaker  A type of loudspeaker sometimes used as a surround speaker. Two or more drivers face opposite directions and their cones vibrate out-of-phase. This causes nulling out of the sound at the side of the speaker creating a "figure-8" sound field with highest sound levels in front of or behind the speaker.

Discrete  Audio information can be isolated, assigned to and sent to a specific speaker. The content in this specific speaker channel is considered to be discrete as it is unique to this channel with no leakage or bleeding from other channels.

DLP  (see Digital Light Processing)

DMD  (see Digital Micro-mirror Device)

Dolby AC-3  The former name for the most popular 5.1-channel home theater sound system. Now called Dolby Digital. In its full implementation, it provides discrete sound signals to front left and right speakers, a center speaker, left and right surrounds, and a Low Frequency Effects (LFE) channel, usually a subwoofer. (also see Dolby Digital and DTS)

Dolby Digital
1) The name for the most popular 5.1-channel home theater sound system. Formerly called Dolby AC-3 it is a data-compression scheme that seeks to eliminate the data we cannot hear while maintaining all the information that we can. Dolby Digital divides the audio spectrum of each channel into narrow frequency bands that correlate closely to the frequency selectivity of human hearing. That allows coding noise to be very sharply filtered by taking advantage of the psychoacoustic phenomenon known as auditory masking. Coding noise stays close in frequency to the audio signal being coded, so it is effectively masked. Bits are distributed among the various channels according to need. Using this system, multichannel surround sound can be encoded at a lower bit rate than required by just one channel on a CD with a compression ratio in the order of 12:1. The nominal bit rate for six (5.1) channels is 384 kilobits per second (Kbps), which represents a compression ratio of about 10 to 1, but is capable of a maximum of 448 Kbps. AC-3 is a “lossy” compression scheme. In its full implementation, it provides discrete sound signals to front left and right speakers, a center speaker, left and right surrounds, and a Low Frequency Effects (LFE) channel, usually a subwoofer. (also see DTS)
2) A 5.1-channel sound system used in some commercial movie theaters.  The audio information is placed in the strips on either side of the sprockets on both sides of the film.

Dolby Digital EX adds an extra surround channel to the already thrilling Dolby Digital 5.1-channel listening experience. Feature films originally released in Dolby Digital Surround EX carry the encoded third surround channel in their subsequent DVD releases, as well as onto 5.1-channel digital satellite and terrestrial TV broadcasts. If your home theater system has a receiver or preamp/processor with Dolby Digital EX decoding-the home version of Surround EX-you can hear Surround EX soundtracks, with the increased realism created by the extra surround channel. With regular 5.1-channel Dolby Digital playback equipment, no sonic information is lost.

Dolby Pro-Logic is a common surround format which can be decoded by most current audio/video receivers. It uses matrixed surround in order to encode four channels of sound on to a 2 track stereo recording, then subsequently decode it back to 4 channels upon playback: left/right front channels, a center front channel, and one surround channel. It is quite common to use two surround speakers to diffuse (more widely disperse) the sound from the one surround channel.

Dolby Pro-Logic IIx provides a solution for 7.1-channel playback of traditional stereo and 5.1-channel content.

Dolby Surround  Prior to Dolby ProLogic, a 3-channel system enabled decoding and playback from matrixed stereo recordings. The channels consisted of front channels (left/right), and one surround channel often split between two surround speakers to diffuse (more widely disperse) the sound from the one surround channel.

Driver The active component of a loudspeaker which pushes or "drives" air movement to create audible sound. The driver is normally placed flush with the face of the loudspeaker enclosure or cabinet and is most often conical or horn shaped.

DTS  A 5.1 channel surround system featuring minimal data compression. The compression ratio is 3.75:1 of a 20-bit PCM digital audio stream with an 8-time oversampling rate. It has a typical data rate of 1411 kilobits per second (kbps)–almost four times higher than Dolby Digital's 384kbps. It uses a digital-coding methodology, designed to filter the audio signal into frequency bands that match the critical perceptual bands of the human ear. Within each frequency band, the signals are requantified at a variable resolution. DTS provides six channels of quality 20-bit recorded material that is sampled at 48 kilohertz with minimal digital compression.  (also see Dolby Digital)

DVD Audio  Unlike stereo CD audio, DVD Audio provides up to six discrete channels for music creating a wider sound stage with an ambience of music surrounding you.

DVI (Digital Video Interface) is a specification created by the Digital Display Working Group (DDWG) to accommodate analog and digital monitors with a single connector. There are three different DVI configurations: DVI-A, designed for analog signals, DVI-D, designed for digital signals, and DVI-I (integrated), designed for both analog and digital signals.

Using a DVI connector and port, a digital signal that is sent to an analog monitor is converted into an analog signal. If the monitor is a digital monitor, such as a flat panel display, no conversion is necessary. Many monitors now include a DVI connection and many video adapters include a DVI port along with, or instead of, the traditional 15-pin Video Graphics Array (VGA) port.

D-VHS is a tape format that allows recording and playback of HDTV programming or the playback of HD pre-recorded materials

EDTV  Enhanced Definition TV is a subset of DTV with the capability of displaying an image at 60 frames per second with 480p in either a 4x3 or 16x9 aspect ratio.

Efficiency  In a general sense, efficiency is the ratio of energy output to the total energy input, expressed as a percentage. In speaker systems, efficiency refers to the ratio of total acoustic watts radiated to total electrical watts input. Home speaker systems of 1% to 3% efficiency are typical, while larger horn-loaded sound reinforcement speakers sometimes reach 10% efficiency or more. Efficiency should not be confused with sensitivity.

Equalization  The action or circuitry which selectively adjusts the level of certain audio frequencies to compensate for deficiencies in the system. Also called "compensation."

Equalizer  A device that changes the relative volume of individual frequency bands to suit the personal tastes of the listener.

Frequency  The rapidity of change in current or voltage in an electrical signal or of air pressure in an acoustical signal. Frequency is measured in cycles per second; 1 cycle per second (cps) is 1 Hertz (Hz). The higher a note on the musical scale, the higher its frequency.

Front Projector  A video device that projects the image on to the front of a fabric screen, typically from a table or ceiling mounting. It allows screen sizes of over 300". Technology includes cathode ray tube (CRT), digital light processor (DLP), and liquid crystal (LCD).

H.264, which is also known as the Advanced Video Codec (AVC) specification or MPEG-4 Part 10, is one of the digital video codecs specified for the Blu-ray (BD) and High Definition DVD (HD DVD) formats. H.264 delivers two to three times the compression efficiency of the MPEG-2 standard, which is used to create current DVD videos. H.264 has been adopted by both the DVD Forum for HD DVDs and the Blu-ray Disc Association for Blu-ray Discs, and VC-1 has also been adopted by the DVD Forum for HD DVDs.

HD DVD (High Definition DVD) uses Blue Laser technology having a much shorter wavelength than the red laser technology used in current DVD.  In fact, the player uses a blue laser for playing high-definition HD DVD discs, and a conventional red laser for playing DVDs and audio CDs.  HD DVDs employ a disc the size of a standard DVD disc, but with much greater storage capacity sufficient to hold an entire film at HDTV resolution or allow two hours of high definition video content to be recorded. Single-layer (20GB) - Dual-Sided Disc (40GB) - Dual Layer (35GB).

HDMI (High Definition Multimedia Interface) is a specification that combines video and audio into a single digital interface for use with DVD players, digital television, set-top boxes, and other audiovisual devices. 

HDMI supports standard, enhanced, or high-definition video plus standard to multi-channel surround-sound audio. HDMI benefits include uncompressed digital video, a bandwidth of up to 5 gigabytes per second, one connector instead of several cables and connectors, and communication between the video source and the DTV.

High Definition Compatible Digital® HDCD® discs are encoded with four bits more than the average 16-bit 44kHz audio resolution of standard CDs. An HDCD decoder allows you to take full advantage of the more than 1,500 CD titles that offer this enhanced resolution. In addition, HDCD technology may improve the sound quality of regular CDs. DVD players that are equipped with an HDCD decoder will give you a greater stereo separation and depth, and will improve the clarity of your favourite music CDs. 

Headroom  Temporary output level beyond a device's continuous rating which it can handle for short periods of time without overload.

High Definition TeleVision (HDTV) broadcast format is the latest standard for North American television with a widescreen aspect ratio of 16:9 (1.78:1). It has over 1,000,000 pixels of resolution, and includes Dolby Digital as the official sound format. This digital system currently co-exists with the current NTSC standard, which digital television (DTV) is slated to replace in the U.S. after the year 2006.

Impedance  The total opposition to the flow of alternating current in an electrical circuit. Impedance is measured in ohms.

Infrared Repeater System  A device designed to receive an infrared signal at one location, convert it to an electrical signal for re-transmission by wire to a second location where the signal is then converted back to infrared.  Typical application: to extend hand held remote control to a device in another room.

Imaging Science Foundation (ISF) is a leading organization in the Display Standards industry. ISF trains technicians in the art of precisely fine tuning video displays (TV, plasma,  front or rear projection, etc.) to obtain the highest images possible and extend the life of the display. TV manufacturers set their video displays to look visually pleasing in a brightly lit retail showroom; however, these settings compromise image quality, as well as lead to long term damage to the display. An ISF certified technician uses specialized diagnostic equipment, test patterns, and a great deal of patience to set up your TV to industry standards of obtaining the most accurate reproduction from the incoming signal.  The visual results are spectacular and as a bonus, the TV will last longer.

Interlaced  A video frame which consists of 2 half frames is created by sequentially scanning only the odd numbered horizontal lines to make the 1st half, then scanning the 2nd half with even numbered lines filling in the gaps. A video amplifier can thus have a slower sweep speed allowing the picture frame to be painted in 2 sweeps over the full screen. The eye merges the interlaced lines into a single frame.

Keystone Correction  Without keystone correction, a projector that is tilted off-axis from perpendicular to the screen will display a picture that is trapezoidal in shape not rectangular as it should be.  Keystone correction is a projector feature which adjusts the picture back to the proper rectangular (undistorted) shape.
Digital keystone correction adjusts the image proportions by shrinking the image at the edge furthest away from the screen before it is generated by the projectors image panel(s). Hence, the image will lose resolution towards this edge. Digital keystone correction may also introduce artifacts, such as jagged edges.
Optical keystone correction adjusts the image proportions by physically modifying the light-path through the lens system. The correction happens after the light has been reflected off (passed through) the image panel(s) in the projector, hence the full panel remain in use - there is no loss of resolution.

LCD (liquid crystal display) A technology where a matrix of thin-film transistors applies voltage to liquid crystal-filled cells sandwiched between 2 sheets of glass. When hit with an electrical charge, the crystals "untwist" to filter light coming from behind the cells. Colour LCD chips - with each pixel comprised of a red, green, and blue cell - are used in many flat-panel TVs and computer monitors, front projectors and rear projection sets.

LCD Projector is one type of front projector. An LCD projector transmits light through a tiny LCD screen and then projects it to produce a larger image. One major benefit is that convergence adjustments are not required to set-up and frequently fine adjust the picture. Drawbacks of this technology are visible pixellation of the image and difficulty achieving dark levels.

LCoS  (liquid crystal on silicon) A fixed pixel display technology in which liquid crystals are applied to silicon chips. As voltage is applied, the light reflected by pixels on the chip varies.

Letterbox  Another name for widescreen, letterboxing was initially used on some laserdiscs whose image portrayed a version displaying black bars at the top and bottom of a 4:3 aspect ratio TV screen. The letterbox or widescreen format is presented in an attempt to be faithful to the aspect ratio of the original film, as opposed to a 'pan and scan' technique used to 'square up' a widescreen film to fill a 4:3 TV screen.

LFE  Low Frequency Effects channel. This is a special channel of 5 to 120 Hz of information primarily intended for special effects such as explosions in movies. The LFE has an additional 10dB of headroom in order to accommodate the required level.

Light-Valve Projector  One type of front projector. It combines the technologies of LCD projectors and CRT projectors. They offer exceptional detail and brightness.

Line Doubler/Tripler/Quadrupler doubles, triples or quadruples the number of lines that make up a picture, therefore increasing detail, and reducing the visibility of scan lines.

Lossy Compression  technologies attempt to eliminate redundant or unnecessary information.  Lossy compression refers to data compression techniques in which some amount of data is lost and unrecoverable in the compression process. Some of what is normally recorded before compression is imperceptible, for example, very loud sounds may overshadow very soft ones. Therefore, some data representing imperceptible sounds can be eliminated. This selective approach, based on phychoacoustic research, is the basis for "lossy" compression. Some will debate how much data can actually be thrown away (or compressed) without an audible sacrifice.

Lossless Compression  A compression format that recovers all the original data from the compressed version. MLP is a lossless compression scheme.

Loudspeaker  A device to convert into audible sound, electrical signals from an amplifier's speaker output. More commonly referred to as speakers, loudspeakers come in many types such as reflex, dipole, bipole, monopole, 2-way and 3-way. For home theater use, they are commonly referred to as fronts (left & right), centre, surrounds, and rear surrounds with centre, depending on their relative placement with respect to a viewer facing the viewing screen or display.

Matrixed Surround refers to the of the process by which Dolby Pro-Logic compatible material is made. It fits four channels of sound into a space meant for two channels. The center channel is decoded by using material common to both left/right channels, and the surround channel is decoded by extracting the sounds with inverse waveforms. One of the limitations of this sound format is channel leakage whereby sound meant for one channel may bleed slightly into another channel, thereby not providing the distinct and clearly separated effect of discrete channels. See Dolby Digital and DTS for discrete channel information.

Monopole Speaker  A type of speaker with all drivers facing one direction. Typically used in front and center speakers where directionality of sound is important.

MLP  Meridian Lossless Packing. This is a data compression technique designed specifically for high quality (96 kHz/24 bit) sonic data. MLP differs from other data compression techniques in that no significant data is thrown away, thereby claiming the "Lossless" moniker. MLP is also a standard for the 96 kHz/24 bit portion of the DVD-Audio disc.

NTSC  The decades old analog broadcast standard for television in the U.S. and Canada. It has an aspect ratio of 4:3 (1.33:1).

Ohm  The unit of measure of electrical resistance or impedance to electron flow.

Omni-directional  Virtually equal sensitivity in all directions. Usually refers to non-directional microphones.

Optical Soundtrack  A clear photographic strip adjacent to the picture on a 35mm movie film print, varying in width according to the sound. As the film is pulled through the movie projector's sound head, a narrow light beam passes through this moving soundtrack, causing the intensity of the beam to vary. The varying light falls on a sensor that creates electrical signals for the theatre's sound system to convert back to sound.

PAL  The television broadcast standard used in Europe. It has a theoretical maximum resolution of 625 lines and displays an aspect ratio of 4:3/1.33:1.

Pan and Scan  A technique used in which a selected portion of widescreen video material is used in order to fit the picture into the narrower aspect ratio of the NTSC standard of 4:3 (1.33:1). The editors making a Pan & Scan version will scan for an important part of the image, and then pan horizontally across during subsequent frames to pick up a wider sense of the image.

Pixel  (Picture Element) The smallest element of an image that can be individually represented in a digital video system or non-CRT video display. 

Plasma Display is a thin (approx. 4" deep) video display technology that displays the video picture on the front of a screen, usually in HDTV format. Suitable for aesthetic or space saving reasons with the screen hung on a wall like a picture. Units supported by a high quality video signal processor exhibit quite spectacular picture quality even in relatively high ambient lighting conditions. The picture is created by varying current in the plasma just under the screen surface thereby exciting light-emitting plasma gas particles.

Play Exchange  Some disc changers will permit you to exchange up to four discs while in play mode. With Play Exchange, there is no need to stop the player in order to remove or insert additional discs. 

Polysilicon Technology splits light into red, green and blue (RGB) components and directs each to its own liquid crystal display (LCD) panel. Each LCD creates an image for its respective color by blocking out portions of the light (similar to a film negative). The output or images of the three panels is then "assembled" by a prism and transmitted through a lens to project a fully saturated color image.

Premastering  The process of adding encoded audio and/or video, with extra program content such as different endings, out-takes, camera angles, and biomaterial, and user interactivity such as menus and buttons to a DVD.

Progressive Scan  Rather than breaking up a frame of video into 2 fields of alternately scanned lines (one of even scan lines, followed by the other of odd scan lines as in interlaced video scanning), progressive scanning scans a complete frame of 480 visible lines in sequence from top to bottom, then shows it again, painting the screen at 60 full frames per second. The result is almost no visible scan lines, less flicker, and a picture to which you can sit more closely without it becoming distracting.

Rear Projector  A device which projects a video image on to a translucent panel of glass or acrylic with a customized coating and structure to optimally refract video imagery. The picture is projected from behind this panel typically by 3 cathode ray tubes (CRT) inside the projector cabinet.

Receiver  A multi-functional device used in home theatre and stereo applications to receive input signals from various sources and output them in a suitable form to loudspeakers.  In the case of an audio/video receiver, video signals will also be sent to a video display device. The receiver is a decoder, audio/video switcher, AM/FM tuner, and an amplifier built into one unit.

Refresh Rate  The number of times at which an image is redrawn on a display device in one second. Usually expressed in hertz (Hz) or cycles per second.

Resolution  A term associated with the number of lines or pixels that make up the picture across the screen. Historically, lines of resolution have been specified with regard to the capability of the video amplifier rather than that which can actually be displayed on the viewing screen. Pixel resolution provides a more truthful description of the picture detail. The higher the number, the more detailed the picture.

Scaling  The reformatting of video or digital pictures to occupy a different number of scan lines or a different horizontal or vertical pixel count.  Also referred to as "resampling". This is done to zoom an image on the screen without spreading out the existing scan lines, or to change the video from one format to another, for example HDTV to NTSC or NTSC to SECAM.
Video Scaler
Electronic device used to perform scaling, usually with a choice of scalings not necessarily an even multiple or fraction of the original scan line or pixel count.

Screen  The media onto which a picture is projected. In direct view (tube) TVs, this is the front portion of the glass cathode ray tube. In rear projection units, the screen typically receives the projection of 3 colour projectors. Front projectors require a separate screen with particular reflective characteristics to catch the image projected from across the room.

SDTV  Standard Definition TV is a subset of DTV covering digital signals that will yield picture quality at least as good as that of analog NTSC television (480i at 30 frames per second).

Sensitivity in speakers is a measure of the on-axis (face on) sound pressure level in relation to electrical input power.

Subwoofer  A special speaker used to handle the lower bass portions of movie and music soundtracks, and can be used with the Low Frequency Effects (LFE) channel in the new digital sound formats. These speakers may handle frequencies as low as 15hz.

Surround Sound  The popular term used to describe an experience where the sound envelopes or 'surrounds' you. The experience is derived using surround-encoded recorded material, and a surround receiver (or equivalent surround pre-amp/ processor and amplifiers) with appropriate loudspeakers.

Surround Speakers  Normally the set of loudspeakers (speakers) located approximately to the right and left of the listener to provide part of the sound enhancement known as Surround Sound.

THX  THX Ltd. is the founder of quality assurance programs for superior cinema presentation. It was established in 1983 by George Lucas to ensure that the entertainment consumer experienced films as the director intended. Through developing and implementing performance standards for cinema auditorium design, acoustic standards, projection equipment and loudspeaker performance, THX has certified more than 3000 theatres worldwide to deliver optimal film presentation.

This high level of performance can also be achieved in the home.  Equipment and recordings using this standard strive to assure the highest quality picture and sound. THX certified DVD discs produced through the THX quality control processes are fully compatible with all video and audio playback systems.  However, to optimize the sound, THX certified surround equipment must be used.  With proper speaker placement, the use of dipole surround speakers and properly adjusted equipment, you will hear the sound as intended by the filmaker when it was mixed professionally.

Toslink  A consumer audio fibre optic connection to carry a digital audio stream. The JIS F05 connector is the most common physical connector. Uses include connection of a CD player to a receiver and for DVD player connection to carry a digital audio stream to a Dolby Digital/DTS decoder.

Tweeter  A speaker driver used in a speaker system to reproduce only the treble or high frequencies of sound.

Watt  A unit of measure for electrical or acoustical power.

Widescreen The term used to describe a picture in which the aspect ratio is wider than the NTSC standard of 4:3 (1.33:1). Today most movie films are shot in some widescreen format. Converting different aspect ratios from film to TV formats is done using several different techniques: anamorphic presentation, letterbox, and Pan and Scan.

Woofer  A speaker driver used in a speaker system to reproduce only the bass or low frequencies of sound.

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