Ardenwood Audio Video Glossary (ctrl F to search)

A/A ROLL EDITING

Editing from a single video source using effects to transition from the source to itself (source "A" to "A") using a picture freeze at the end of one scene to transition the start of the next scene.

A/B ROLL EDITING

Editing from two video sources ("A" and "B") to a third record VCR. Typically a switcher is used to provide transition effects between sources. Control over the machines and process can be done manually or automatically using an edit controller.

A/D CONVERTER (Analog-to-Digital Converter)

A device that digitizes an analog waveform.

A:B:C Notation

The a:b:c notation for sampling ratios, as found in the CCIR-601 specifications, has the following meaning:

• 4:2:2 means 2:1 horizontal downsampling, no vertical downsampling. (Think 4 Y samples for every 2 C b and 2 C r samples in a scanline)
• 4:1:1 ought to mean 4:1 horizontal downsampling, no vertical. (Think 4 Y samples for every 1 C b and 1 C r samples in a scanline) It is often misused to mean the same as 4:2:0.
• 4:2:0 means 2:1 horizontal and 2:1 vertical downsampling. (Think 4 Y samples for every C b and C r samples in a scanline)

Not only is this notation not internally consistent, but it is incapable of being extended to represent any unusual sampling ratios, eg. different ratios for the C b and C r channels.

AC-3

A term synonymous with Dolby Digital.

ACCESS TIME

The time it takes to retrieve a piece of information. With hard disks and compact discs, maximum access time is measured as the time it takes to move from one end of the disc to the other, find a piece of information, and transfer that information to RAM.

A-CHARACTERS

A character set used in the ISO 9660 Volume Descriptors. It consists of capital letters A to Z, digits 0 to 9, and the following symbols: (space)! " % & '()=*+,-./:;<?>_

ADPCM (Adaptive Delta Pulse Code Modulation)

An audio encoding compression technique which encodes the difference between the predicted value of the signal instead of the absolute value of the original waveform so that the compression efficiency is improved. This difference is usually small and can thus be encoded in fewer bits than the sample itself. Used in CD-I and CD-ROM XA recording.

ADR

Acronym for Automated Dialogue Replacement.

AES/EBU

Acronym for the dual-channel digital audio interface jointly conceived by the Audio Engineering Society and the European Broadcasting Union and defined by Standard IEC-958. This interface is usually found on professional equipment with connections made via XLR-type (3-pin) connectors. (See S/PDIF)

AES31 (AES31-3)

A proposed AES (Audio Engineering Society) standard for digital audio project interchange.

ADAT

An 8-channel digital audio tape recorder format utilizing S-VHS videocassettes, developed by Alesis.

ADL (Audio Decision List)

A sample-accurate EDL generated by a DAW rather than a video editing system.

AGC (Automatic Gain Control)

Circuitry used to ensure that output signals are maintained at constant levels in the face of widely varying input signal levels. AGC is typically used to maintain a constant video luminance level by boosting weak (low light) picture signals electronically. Some equipment include gain controls which are switchable between automatic and manual control.

ALC (Automatic Level Control)

Circuitry used to automatically adjust the audio recording level to prevent excessive volume. Excessive ALC has a tendency to introduce noise and hiss onto the audio tracks. Some equipment include level controls which are switchable between automatic and manual control. Used in video and audio equipment to ensure that output signals are maintained at constant levels in the face of widely varying input signal levels.

ALIASING

Undesirable signals added to and interfering with an originating electronic signal.

• In audio, frequencies generated by inadequate digital filter sampling circuitry, harmonically unrelated to the original signal.
• In video, display effects caused by too much high frequency video information. Examples are:
• Temporal aliasing - e.g., rotating wagon wheel spokes apparently reversing direction
• Raster scan aliasing - e.g., twinkling or strobing effects on sharp horizontal lines
• Stair-stepping - Stepped or jagged edges of angled lines, e.g., at the slanted edges of letters.

(See ANTI-ALIASING)

AM (Amplitude Modulation)

Amplitude modulation is a process used for some radio (AM broadcast) andtelevision video transmission. A low frequency (program) signal modulates (changes) the amplitude of a high frequency RF carrier signal (causing it to deviate from its nominal base amplitude). The original program signal is recovered (demodulated) at the receiver. This system is extensively used in broadcast radio transmission because it is less prone to signal interference and retains most of the original signal quality. In video, FM is used in order to record high quality signals on videotape.

ANALOG

An adjective used to describe a method of converting audio and video information to a continuously varying voltage or magnetic field representing the original data. The term is used mainly to differentiate established data storage methods of the 1960s and 1970s from the newer digital storage methods. Information stored in analog form is subject to generation losses and degradation due to noise, distortion and other electronic phenomena over time.

Examples of data stored in analog form are the VHS and 8mm videotape formats with typical video signal levels within the 0.7 - 1V (volt) range. (See DIGITAL)

ANALOG MONITOR

A television set, which cannot receive TV broadcasts because of its lack of a TV tuner, which accepts only analog signals. Several types of signal formats are accepted by analog monitors: composite video, RGB & sync, Y/C, YUV and any combination of these formats. The signals transmitted to an analog monitor are usually between 0 and 1V (volt) and use 75 ohm coaxial cables.

ANSI-LABELED

A tape recorded with a file structure and tape label system which defines the Volume name and file header for the information contained in the tape, according to ANSI (American National Standards Institute) specification X3.27-19778. Most disc manufacturers prefer ANSI-labeled tapes.

ANSI-UNLABELED

A tape recorded with a file structure, but without the ANSI tape labels.

ANTI-ALIASING

The process of electronically reducing aliasing, especially letters and genlocked graphic elements.

APERTURE

An adjustable opening in a lens which affects the amount of light entering a camera. The size of the aperture is controlled by the iris adjustment and is measured in f-stops. Smaller f-stop numbers pass more light to the surface of the camera’s pickup device.

ASIO (Audio Stream Input Output)

A standardized communication protocol between audio software and hardware, developed by Steinberg Media Technologies to bypass the problem of potentially high operating system/monitoring latency (time delay). It enables audio hardware manufacturers to write optimized drivers for their hardware. For a user, the knowledge that an ASIO driver exists for a particular piece of hardware, is a sign that there will be a performance boost, compared with the same audio card configured to use an operating system’s own mechanism.

ASPECT RATIO

The ratio between the height and width of the TV picture on the screen. The aspect ratio for a standard TV or video monitor is 4 to 3 (4:3). The HDTV video format has an aspect ratio of 16 to 9 (16:9).

ASPI (Advanced SCSI Programmer’s Interface)

Set of software primitives and data structures which allow software using the ASPI interface to be SCSI host adapter-independent.

A-TIME (Absolute Time)

Elapsed time measured in minutes, seconds and frames, referenced to the program start (00:00:00) on a CD, CD-DA or DAT. Can be used in determining the start and stop times of sound segments for programming an application on a mixed-mode disc, measuring from the very beginning of the data area (including the computer data in Track 1).

ATM (Asynchronous Transfer Mode)

Describes the ways a digital audio word may be transmitted (either big endian or little-endian). If a word is presented most significant bit first, it is big-endian. If presented least significant bit first, it is little endian.

AUDIO

The audible portion of any multimedia material consisting of frequencies corresponding to a normally audible sound wave (20 Hz to 20,000 Hz). Also the "soundtrack" of a videotape.

AUDIO BANDWIDTH

The range of audio frequencies which directly influence the fidelity of a sound. The higher the audio bandwidth, the better the sound fidelity. The highest practical frequency which the human ear can normally hear is 20 kHz. An audio amplifier which processes all frequencies equally (flat response from 20 Hz to 20 kHz) and a reasonably high signal-to-noise ratio, will faithfully reproduce the full range of perceptible sound.

AUDIO-FOLLOW-VIDEO

During video recording, the video signal is usually accompanied by an audio signal. Sometimes, during video editing, it is often necessary to separate the audio from the video signal. Audio-follow-video mixers allow accompanying audio to "follow" the video when switching video sources.

AUDIO LEVELS

Proper audio levels are crucial. If the audio level is too high when recording, overload of the input electronics will cause audio distortion. If audio levels are too low, the signal-to-noise ratio deteriorates. Audio levels are typically indicated either by mechanical VU-meters or electronic LED bar graph meters.

AUTHORING

Creation of a database for a CD-ROM. The end product of authoring is usually a search and retrieval type document with the addition of a user interface. Specific authoring functions include tagging and indexing.

B-ROLL

Stock footage acquired for miscellaneous needs.

BACK LIGHT

• A light source that illuminates a subject from behind, used to separate the subject from the background and give them depth and dimension. Back lights are often improperly applied or overlooked completely.
• Also a switch on some camcorders used to compensate exposure for situations where the brightest light is coming from behind the subject.

BANDWIDTH

(See AUDIO BANDWIDTH and VIDEO BANDWIDTH)

BARCODE

A unique code for a compact disc. With recordable CDs, this number is often printed in the clear inner ring of the disc. Some CD recorders can also read this information digitally.

BETA or BETAMAX

Consumer videocassette record/playback tape format using half-inch wide magnetic tape. The Beta system was the first consumer videocassette (VCR) format introduced by Sony in the mid 1970s. Although the format produces a higher quality video signal than VHS, marketing blunders by the Japanese electronics giant sealed the fate of the format. Sony continues to manufacture Beta format videocassettes and VCRs as there still is a small established market for them.

BETACAM

Portable, professional, high resolution record/playback tape format using the same videocassette shell as the original Betamax. Unlike its predecessor, it records video in component (YUV) format.

BETACAM SP

A superior performance version of Betacam. SP uses metal particle tape and a wider bandwidth recording system.

BIT DEPTH

(See WORD LENGTH)

BIT RATE

(See WORD LENGTH)

BITC (Burnt-In Timecode)

A visual overlay of time code on a video picture.

BLACK A TAPE

The process of recording a black burst signal across the entire length of a videotape. Often done before recording edited footage on the tape to give the tape clean, continuous video sync and to insure there is no video already on the tape.

BLACK BURST

A composite color video signal comprised of a sync, color burst and black video. It is used to synchronize (genlock) other video sources to the same sync and color information. Black burst generators are used in video studios to "lock" the entire facility to a common signal ("house sync" or "house black").

BLACK LEVEL

The voltage in a video signal which corresponds to black.

BLANKING LEVEL

Also known as the pedestal, it is the voltage level produced at the end of each horizontal picture line which separates the portion of the video signal containing the picture information from the portion containing the synchronizing information. This voltage makes the electron beam "invisible" as it moves to draw the next visible line.

BLANKING INTERVAL (Horizontal & Vertical)

The horizontal blanking interval is the time between the end of one scanning line and the beginning of the next. The vertical blanking interval is the time between the end of one video field and the beginning of the next. Blanking occurs when a monitor’s electron beam is positioned to start a new line or a new field. The blanking interval is used to instantaneously reduce the beam’s amplitude so that the return trace is invisible. (See VERTICAL INTERVAL SWITCHING)

BLER (Block Error Rate)

The “raw” digital error rate usually measured off media before any error correction.

BLUE BOOK

(See CD-EXTRA)

BNC (British Naval Connector)

A type of connector used on some consumer and most professional VCRs, video and RF equipment providing a secure twist-lock capability.

BUFFER

An amount of memory which temporarily stores data to help compensate for differences in the transfer rate of data from one device to another.

BUFFER UNDERRUN

A buffer underrun occurs when the system cannot keep up a steady stream of data as required by CD recording. The CD recorder has a buffer to protect against interruptions and slowdowns, but if the interruption is so long that the recorder’s buffer is completely emptied, a buffer underrun occurs, writing halts, and most often the recordable CD is irretrievably damaged.

BURN

To generate a CD-ROM on a specialised CD-R writer drive. The term ‘burn’ comes from the heat generated by the laser needed to make the pits in the disc.

CACHE

A portion of RAM used for temporary storage of data which must be accessed very quickly. In applications which run from CD-ROMs, the cache is typically used to store directory files.

CADDY

The plastic and metal carrier into which a CD must be inserted before it is loaded into some CD-ROM drives or CD recorders. Also called a cartridge.

CAMCORDER

Combination of camera and video tape recorder in one device. Camcorders permit easy and rapid photography and recording simultaneously. Camcorders are available in most home video formats: 8mm, Hi-8, VHS, VHS-C, S-VHS, etc.

CAMERA SUPPLY

Most video cameras use an external DC voltage supply which is derived either from a battery belt worn by the camera operator, from a battery within the video recorder itself, or from the mains power supply (after voltage conversion).

CANDLEPOWER

The unit measure of incident light.

CASSETTE

The standard consumer analog audio cassette introduced by Philips in the early 1970s.

CATV

Acronym for cable TV, derived from the older term, community antenna television.

CAV (Constant Angular Velocity)

Method of spinning a disc, in a CD-ROM or Laserdisc drive, in which the spin speed of the disc is held steady regardless of where the drive’s head mechanism is located. This results in increased data transfer rates and reduced seek times as the head moves towards the disc’s outside edge. Has largely superseded CLV.

CCD (Charge Coupled Device)

A semiconductor device (IC) that converts optical images to electronic signals. CCDs are the most commonly found type of image sensor in consumer camcorders and video cameras.

CCIR (Comite Consulatif International Des Radiocommunications)

A European committee situated in Paris responsible for creating and approving professional standards related to audio and video.

CCTV (Closed Circuit TV)

A video system used in many commercial installations for specific purposes such as security, medical and educational.

CD (Compact Disc)

(See CD-DA)

CD-DA (Compact Disc-Digital Audio)

The Philips/Sony specification for audio, launched in October 1982. CD-DA was the first incarnation of the compact disc used to digitally record and playback music. The CD-DA specification is known as the Red Book standard.

CD EXTRA or CD PLUS

A format for combining audio (which can be played in a normal audio CD player) and computer application data, seamlessly on one multisession disc. Audio tracks are written in the first session and one CD-ROM XA data track in the second session. This format is an alternative to mixed-mode. The CD-EXTRA specification is known as the Blue Book standard.

CD-I (Compact Disc-Interactive)

A compact disc format designed to allow interactive multimedia applications to be run on a player attached to a television. The CD-I specification is known as the Green Book standard.

CD-I BRIDGE

A set of specifications defining a way of recording CD-I information on a CD-ROM XA disc. Used for Photo CD and Video CD.

CD-MO (Compact Disc-Magneto Optical)

A rewritable optical storage technology that uses a combination of magnetic and optical methods. Data is written on an MO disk by both a laser and a magnet. The laser heats the surface to its Curie point, then a magnet alters the bit’s polarity. Writing takes two passes. MO disks do not have to be 'reformatted' when full. The CD-MO specification is part of the Orange Book standard.

CD-R (Compact Disc-Recordable)

The write-once compact disc format sometimes referred to as Compact Disc-Write Once (CD-WO). The format The CD-R specification is primarily defined in Part II of the Orange Book standard.

CD-ROM (Compact Disc-Read Only Memory)

A standard for compact disc to be used as a digital storage medium for personal computers. The disc can hold about 650MB of data, sound and limited stills and motion video. CD-ROM players will typically play CD-DA discs, but a CD-DA player will not play CD-ROMs. The CD-ROM specification is known as the Yellow Book standard.

CD-ROM DRIVE

A peripheral device attached to a computer which allows it to read/play a CD-ROM disc. All CD-ROM players can also play back audio CDs but you need external headphones or speakers to hear them.

CD-ROM XA (Compact Disc-Read Only Memory Extended Architecture)

An extension to the Yellow Book standard which utilizes the Mode 2 data format, generally consistent with the ISO 9660logical format but designed to interleave compressed audio, video and data as well as the encoding of PCM and ADPCM audio for multimedia synchronization purposes. CD-ROM XA did not develop very far as a multimedia format, but Photo CD discs are written in the CD-ROM XA physical format.

CD-RW (CD-ReWritable)

CD recordable media which can be erased and re-recorded. CD-RW media can only be written in a CD-RW recorder, not in a normal CD recorder, though a CD-RW recorder can also record write-once media. Formerly known as CD-E (CD-Erasable).

CD-WO (Compact Disc-Write Once)

A rarely used term for CD-R.

CD STANDARD

Comprised of one or more of the following documents available from Sony and Philips:

• Red Book, CD-DA
• Yellow Book, (ISO/IEC 10149) CD-ROM
• Orange book part 2 - CD Recordable, and part 3 - CD Erasable
• White book, CD-Video
• Green book, CD Interactive, CD-I
• CD-ROM XA
• Enhanced Music CD, CD Extra
• Multisession CD

CHARACTER GENERATOR

Device that electronically generates text which can be superimposed over a video signal. Text is usually entered via a keyboard, allowing selection of various fonts, sizes, colors, styles and background colors, then stored as multiple pages for retrieval.

CHROMINANCE

The color information contained in a video signal separate from the luminance component, consisting of the hue (phase angle) and saturation (amplitude) of the color subcarrier signal.

CHROMA CORRECTOR

A device used to correct problems related to the chrominance of the video signal, as well as color balance and color noise.

CHROMA NOISE

Noise which manifests itself in a video picture as colored snow.

CHROMA KEY

The process of overlaying one video signal over another by replacing a range of colors with the second signal. Typically, the first (foreground) picture is photographed with a person or object against a special, single-color background (the key-color). The second picture is inserted in place of the key-color. The most common example is in broadcast weather segments where pictures of weather maps are inserted "behind" the talent.

CHROMA LEVEL

Relating to the amount of saturation and hue at a particular point of an image. Black, gray and white have no chrominance, but any colored signal has both chrominance and luminance. The higher the chrominance level, the stronger the color (e.g., a strong signal produces red, and a weak signal, pink). Color saturation level can be changed using a color processor.

CIRC (Cross-Interleaved Reed-Solomon Code)

The first level of error correction used in every compact disc, and the only one used for audio CDs. It consists of two Reed-Solomon codes interleaved crosswise. (See CD-DA)

CLIPPING

The electronic action of shearing off the peaks of audio signals or either the white or black excursions of a video signal.

• In audio, clipping may be produced intentionally in a controlled fashion by a peak limiter. Unintentional clipping is almost always undesirable and detrimental to the sound quality.
• In video, clipping is sometimes performed prior to video modulation and other times to limit the signal, so it will not exceed a predetermined level.

CLOSE DISC

To "close" a recordable compact disc so that no further data can be written to it. This is done when the last recording session lead-in is written - the next writeable address is not recorded in that lead-in, so the CD recorder in subsequent attempts to write has no way of knowing where to begin writing. It is NOT necessary to close a disc in order to read it in a normal CD-ROM drive.

CLV (Constant Linear Velocity)

Method of spinning a disc, in a CD-DA or Laserdisc drive, in which the spin speed of the disc is regulated as the drive’s head mechanism moves towards the outside edge of the disc. This way, the data rate is maintained across the entire surface of the disc.

COAXIAL CABLE

The standard cable consisting of a central inner conductor and a cylindrical outer conductor. Used for many video connections, especially by CATV companies.

COLOR BARS

An electronically generated video pattern consisting of eight equal width colors, used to establish a proper color reference before recording and playback and for adjustment purposes.

COLOR BURST

The portion of a color video signal which contains a short sample of the color subcarrier used to add color to a signal. It is used as a color synchronization signal to establish a reference for the color information following it and is used by a color monitor to decode the color portion of a video signal. The color burst acts as both amplitude and phase reference for color hue and intensity. The color oscillator of a color television receiver is phase locked to the color burst.

COLOR CORRECTION

A process in which the coloring in a television image is altered or corrected by electronic means. (See CHROMA CORRECTOR)

COLOR DECODER

A device which divides a video signal into its basic color components. In TV and video, color decoding is used to derive signals required by a video monitor from the composite or component signals.

COLOR PHASE

The phase of the chroma signal as compared to the color burst, is one of the factors that determines a video signal’s color balance.

COLOR TEMPERATURE

A method for specifying the overall color of a light source, measured in degrees Kelvin (°K). Higher numbers indicate bluer light, lower numbers indicate a warmer light.

• Daylight = 5000-5500 °K
• Fluorescent = approx. 4100 °K
• Indoor incandescent = 2800 °K

COLOR SUBCARRIER

The 3.58 MHz/NTSC (4.43 MHz/PAL) signal added to a black and white television signal to add color information. The subcarrier frequency is too high to be detected by black and white televisions ensuring compatibility. Color sets employ special circuitry which detects and decodes the color component for display.

COLORIZATION

Special effect (also called paint) which colors a monochrome or color image with artificial colors.

COMMUNICATION PROTOCOL

A specific software based protocol or language for linking several devices together. Communication protocols are used between computers and VCRs or edit controllers to allow bi-directional "conversation" between the units. (See RS-232/RS-422)

COMPONENT VIDEO

Most home video signals consist of combined (composite) video signals, composed of luminance (brightness) information, chrominance (color) information and sync information. To get maximum video quality, professional equipment (Betacam and MII) and some consumer equipment (S-VHS and Hi-8) keep the video components separate.

COMPOSITE SYNC

A signal consisting of horizontal sync pulses, vertical sync pulses and equalizing pulses only.

COMPOSITE VIDEO

A video signal in which the luminance (brightness), chrominance (color), blanking pulses, sync pulses and color burst information have been combined using one of the international coding standards (NTSC, PAL, SECAM). This combined signal is used by television stations and all consumer and professional videocassette recorders (VCRs) and laser disc players. You can display and use composite video images by using a composite BNC or RCA connector cable.

COMPRESSION

• The process of restricting the dynamic range of an audio signal (as with MP3), in order to reduce the amount of storage or bandwidth required by the file.
• The process of electronically processing a video picture in order to reduce the amount of storage or transmission channel bandwidth required for the signal.
• The process of removing picture data to decrease the size of a video image.

CONTRAST

• The degree to which the various luminance values in a picture are mapped to very dark and very light values. A high-contrast picture is dominated by black and white and few values between. A low contrast picture has a lot of middle tones without many very dark or very light areas.
• A control on a television or monitor which adjusts the white level of the picture.

CONTROL-L

Sony’s wired consumer edit control protocol, also called LANC (Local Application Control), which allows two-way communication between a camcorder or VCR and an edit controller. Control-L allows the controller to control the deck (fast forward, play, etc.) and also allows the controller to read the tape position (tape counter) information from the deck.

CONTROL-M

Panasonic’s wired consumer edit control protocol. Similar to Control-L in function but not compatible. Also called Panasonic 5-pin edit control.

CONTROL-S

Sony wired transport control protocol which duplicates a VCR’s infra-red remote transport control (play, stop, pause, fast forward and rewind). Unlike Control-L, Control-S does not allow the controller to read tape counter information.

CONTROL-T

Similar to Control-L but allows multiple units to be controlled. Not used in current equipment.

CONTROL TRACK

The magnetized portion along the length of a videotape on which sync control information is placed. The control track contains a pulse for each video field and is used to synchronize the tape and the video signal.

CROSSFADE

The audio equivalent of the video dissolve where one sound is gradually faded out while a second sound simultaneously replaces the original one.

CROSSTALK

The interference between two or more audio or video signals caused by unwanted stray signals.

• In audio, crosstalk exhibits itself as signal leakage, typically between left and right channels or between different inputs, or as noise.
• In video, crosstalk between input channels can be classified into two basic categories:
• Luminance/sync crosstalk
• Chroma crosstalk

Audio crosstalk is usually caused by poor circuit design, poor grounding connections or improperly shielded cables. When video crosstalk is too high, ghost images from one source appear over the other.

CURIE POINT

The temperature at which a material loses its magnetic properties. Its molecules may then be realigned by an external magnetic field. For optical material, this temperature is approximately 200 degrees centigrade.

CYANINE

One type of organic dye used to form the data layer in CD-R discs. Cyanine was the first material used for these discs, but presently a metal-stabilized cyanine compound is generally used instead of “raw” cyanine. An alternative material is phthalocyanine.

D-CHARACTERS

A character set used in ISO 9660 Level 1 filenames, if the standard is strictly adhered to (which is not always necessary). Consists of capital A to Z, digits 0 to 9, and the underscore symbol ( _ ).

D/A CONVERTER (Digital-to-Analog Converter)

A device that coverts digital data into an analog waveform.

D1/D2/D3

Professional Digital video recording and playback formats. The D1 system uses component video while the D2 and D3 systems use composite video. By using fully digitized video in recording and playback, many problems such as generation loss and distortion are minimized or eliminated. The digital formats use mainly a 19mm wide magnetic tape (3/4").

DAT (Digital Audio Tape)

A consumer digital audio record/playback system developed by Sony, with a signal quality capability surpassing that of the CD. The DAT format was introduced in the mid 1980s as the first widely distributed consumer digital recording product. It accommodates the high bit rate transfer necessary for digital audio recording by using a rotating head similar to those used in current VCRs. Though the actual tape speed is rather slow, the rotating head gives the system a high relative tape to head speed ratio.

Its introduction in the U.S. was initially met with resistance from record companies and music publishers who claimed that rampant copying would impact their sales. Because of this resistance, its U.S. introduction was delayed, subsequently hampering its acceptance as a viable consumer format. It has since been adopted as a useful format by professionals.

An interesting note is that these same organizations opposed the introduction of the standard audio cassette in the early 1970s for similar reasons. Since the mid 1980s, pre-recorded audio cassette sales have outpaced all other forms of music distribution media combined.

DATA AREA

In ISO 9660, the space on a CD-ROM where the user data is written. It begins at the physical sector address 00:02:16.

DATA COMPRESSION

(See COMPRESSION)

DAW (Digital Audio Workstation)

A computer system containing dedicated hardware and software for editing, processing and mixing digital audio.

dB (Decibel)

A unit for expressing the ratio of two amounts of electric or acoustic signal power, used for measuring audio and video signals. Technically, this is equal to 20 times the common logarithm of the voltage or current ratio.

DCC (Digital Compact Cassette)

A consumer digital audio record/playback system developed by Philips. The DCC audio format was introduced by Philips in the early 1990s as an alternative to the DAT recording format. It boasts backward compatibility with the original analog audio cassette it was designed to replace through the use of a shell roughly the same size and shape as the standard cassette.

DD (Dolby Digital)

(See DOLBY DIGITAL)

DECODE

To expand a compressed audio signal or separate a composite video signal into its component parts.

DEFINITION

The aggregate of fine details available on a video screen. The higher the image definition, the greater the number of details that can be discerned.

ck, several factors can conspire to cause a loss of definition. Among these are the limited frequency response of magnetic tapes and signal losses associated with electronic circuitry employed in the recording process. These losses occur because fine details appear in the highest frequency region of a video signal and this portion is usually the first casualty of signal degradation. Each additional generation of a videotape results in fewer and fewer fine details as losses are accumulated.

DELAY CORRECTION

When a video signal travels through electronic circuitry or even through long coaxial cable runs, delay problems may occur. This is manifested as a displaced image and special electronic circuitry is needed to correct it.

DEMODULATOR

An electronic circuit which separates the audio and video signals from the RF carrier frequency.

DEPTH OF FIELD

The range of objects in front of a camera lens which are in focus. Smaller f-stops provide greater depth of field, i.e., more of the scene, near to far, will be in focus.

DIGITAL

An adjective used to describe a method of representing data using binary numbers. An analog signal is converted to digital using an analog-to-digital (A/D) converter chip by taking samples of the signal at a fixed time interval (sampling frequency). Assigning a discrete binary number to each of these samples, the digital stream is then recorded onto magnetic tape. Upon playback, a digital-to-analog (D/A) converter chip reads the binary data stream and reconstructs the original analog signal.

Unlike analog storage methods, data stored or transferred in digital form is immune to noise, distortion, crosstalk and signal degradation over time and virtually eliminates generation loss, as every digital-to-digital copy is theoretically an exact duplicate of the original. In this way, multi-generational dubs can be made without degradation. In actuality of course, digital systems are not perfect and specialized hardware/software error correction schemes are used to correct all but the most severe data losses.

Examples of digitally stored information are the compact disc, laser disc and the data on a computer hard disk. In addition, digitally based equipment often offers advantages in cost, features, performance and reliability when compared to analog equipment. (See ANALOG)

DIGITAL DELAY

A term used to describe a "black box" which delays an audio signal in millisecond increments for use in recording studios or public address systems. The signal is converted internally to a digital signal and passed through various components "bucket brigade style" to delay the processed signal compared to the original signal.

DIN (Deutsche Industrie Norme)

An international connector standard. DIN connectors carry both audio and video signals and are common on equipment in Europe.

DISC-AT-ONCE

Mode of writing an entire disc without turning off the recording laser. All of the information to be recorded needs to be staged on the computer’s hard disk prior to recording. The mode is especially useful for creating a master disc for subsequent mass replication thus eliminating the linking and run-in/run-out blocks associated with multisession and packet recording modes, which are often interpreted as uncorrectable errors during the mastering process. It requires the pre-mastering software to send a 'cue sheet' to the CD-R drive that describes the disc layout.

DISSOLVE

A process whereby one video signal is gradually faded out while a second image simultaneously replaces the original one.

DISTORTION

• In video, distortion usually refers to changes in the luminance or chrominance portions of a signal. It may contort the picture and produce improper contrast, faulty luminance levels, twisted images, erroneous colors and snow.
• In audio, distortion refers to any undesired changes in the waveform of a signal caused by the introduction of spurious elements. The most common audio distortions are harmonic distortion, intermodulation distortion, crossover distortion, transient distortion and phase distortion.

DISTRIBUTION AMPLIFIER

A device which splits (distributes) one audio and/or video source to several audio/video devices.

• In audio, distribution amplifiers are typically used to make single source signals available to multiple devices without compromising the integrity of the original signal, by compensating for long cable runs, properly terminating all circuits and keeping interaction between all devices to a minimum.
• In video, distribution amplifiers are used in duplication studios where many tape copies must be generated from one source or in multiple display setups where many monitors must carry the same picture, etc.

DITHER

Random data or noise that linearizes digital audio. Adding dither can actually increase the apparent resolution of audio signals which are operating in the lowest ranges (least-significant bits) of both A/D and D/A converters and also reduce requantizing distortion. Virtually all modern A/D converters add dither to the analog signals they process; therefore, when you add dither to a digital signal, you are actually redithering or dithering again.

DOLBY®

A compression/expansion (companding) noise reduction system developed by Ray Dolby, widely used in consumer, professional and broadcast audio applications. Signal-to-noise ratio improvement is accomplished by processing a signal before recording and reverse-processing the signal upon playback.

DOLBY DIGITAL

An advanced compression method that allows 1 to 5.1 channels of sound to be presented on disc. This is the standard sound format that is required on DVD, and it will also be used in future HDTV broadcasts. Audio equipment with a Dolby Digital decoder is required for playback, although all DVD players will "downmix" the signal into two-channel surround if you don’t have the DD equipment.

DOW (Direct OverWrite)

Method of writing new data over existing data in a single-pass. CD-RW is an example of a Direct Overwrite system.

DROPOUT

A momentary partial or complete loss of picture and/or sound caused by such things as dust, dirt on the videotape or heads, crumpled videotape or flaws in the oxide layer of magnetic tape. Uncompensated dropout produces white or black streaks in the picture.

DSD (Direct Stream Digital)

Digital audio recording format used for the new SACD (Super Audio CD) developed by Sony. Unlike the PCM recording format used for the standard CD, DSD uses 1-bit sampling at 2.88MHz and requires 353kB of storage per mono second (i.e. 4 times more than 16-bit PCM audio at 44.1kHz).

DSK (Downstream Keying)

A feature available in some special effects generators and video mixers in which one video signal is keyed on top of another video signal. The lightest portions of the DSK signal replace the source video leaving the dark areas showing the original video image. Optionally, the DSK signal can be inverted so the dark portions are keyed rather than the lightest portions allowing a solid color to be added to the keyed portions. The DSK input is most commonly a video camera or character generator. The DSK signal must be genlocked to the other signals.

DTRS

An 8-channel digital audio tape recorder format utilizing Hi-8 videocassettes, developed by Tascam.

DTS (Digital Theater Systems)

A competing multi-channel audio format that also encodes 1 to 5.1 channels of sound for playback on equipment that has a DTS decoder. Common in movie theaters, on laserdisc, and on compact disc, but there are no DTS DVDs yet. A DTS-compatible DVD player will be required for playback of the DTS signal, and only select recent DVD player have this capability.

DUB

A duplicate copy made from one recording medium to another.

DUBBING

The action of adding or replacing audio, synchronized to a film or video picture. Virtually all modern motion pictures do some form of "dubbing" after the initial footage has been shot, to replace actors spoken lines or add sound effects. Audio dubbing is also a VCR feature allowing replacement of the audio signals on a previously recorded tape without disturbing the video signal.

DUPLICATION

Making multiple copies of a compact disc with a device which writes each CD one at a time.

DVD (Digital Versatile Disc)

A new format jointly developed and agreed upon by Toshiba, Matsushita, Sony, Philips, Time Warner, Pioneer, JVC, Hitachi and Mitsubishi Electronics. DVD is now the universal format for high density audio and video compact discs utilizing higher data transfer rates. For computer applications, the disc will be called DVD-ROM and for audio, DVD-Audio. Like the CD, it is available in a number of different formats. Unlike the CD, it is available in a number of capacities ranging from 4.7GB to 17GB.

DVD-R (DVD-Recordable)

The write-once DVD format standard. DVD-R discs are the DVD counterpart to CD-R discs.

DVD-RAM (DVD-Rewritable Memory)

A new type of rewritable compact disc that provides much greater data storage than today’s CD-RW systems. The caddy-mounted discs will initially provide 2.6GB per side on single or double-sided discs.

DVD-ROM (Digital Versatile Disc-Read Only Memory)

This read-only format supports discs with capacities from 4.7GB (enough for an MPEG-2 compressed full-length movie) to 17GB, and access rates of 600KBps to 1.3MBps. DVD-ROMs are backward-compatible with CD-ROMs.

DVD-RW (DVD-ReWritable)

Recordable and erasable media version of the DVD-R format standard. DVD-RW media can only be written and erased in a DVD-RW recorder, not in a normal DVD-R recorder, though a DVD-RW recorder can also record write-once media.

DVD-Video

A consumer DVD format for displaying full-length digital movies. DVD-Video players attach to a television like a videocassette player. Unlike DVD-ROMs, the digital video format includes a Content Scrambling System (CSS) to prevent users from copying discs. This means that today’s DVD-ROM players cannot play DVD-Video discs without a hardware or software upgrade to decode the encrypted discs.

DVD+R (DVD+Recordable)

An incompatible competitor to the DVD-R format standard, this write-once DVD is being promoted by Hewlett-Packard, Philips and Sony.

DVD+RW (DVD+ReWritable)

An incompatible competitor to the DVD-RW and DVD-RAM format standard, this rewritable DVD is being promoted by Hewlett-Packard, Philips and Sony. DVD+RW media can only be written and erased in a DVD+RW recorder, not in a normal DVD+R recorder, though a DVD+RW recorder can also record write-once media.

DVE (Digital Video Effects)

These effects are found in special effects generators which employ digital signal processing to create two or three dimensional wipe effects.

DVI (Digital Video Interface)

Multimedia standard for computer generated text and graphics merged in video production.

8MM

A compact consumer videocassette record/playback tape format utilizing eight millimeter wide magnetic tape. A worldwide standard established by Sony in 1983, the small size of the cassette made the palm-sized camcorder a reality. Hi-8 is a format offshoot which increases the horizontal video resolution to over 400 lines, improving reproduced picture quality, sharpness and detail. The two formats are incompatible although Hi-8 equipment can record and play standard 8mm tapes.

EAN (European Article Number)

A unique thirteen-digit catalog number assigned to a compact disc in order to identify it when sold commercially. The number, controlled by the EAN Council located at Rue des Colonies, 54-BTE8, 1000 Brussels, Belgium, is written in the disc’s Table of Contents. The U.S. equivalent is known as the UPC.

ECC (Error Correction Code)

A system of scrambling and recording redundant data onto disc as it is premastered. On playback this redundant information helps to detect and correct errors that may arise during data transmission.

EDC (Error Detection Code)

32 bits in each sector which are used to detect errors in the sector data.

EDIT CONTROL

A connection on a video tape machine, VCR or camcorder which allows direct communication with external edit control devices. (e.g., Sony P2, LANC (Control-L and Control-M).

EDITING

The action of adding, removing, reordering or manipulating selected portions of audio, video or film program material in order to create a new, combined version. In the 1950s, audio and video material was edited like film, with razor blades and splicing blocks. While this continues to be the preferred way to edit the "celluloid" medium of film, it left much to be desired for the "electronic" mediums of audio and video.

Video was first to take advantage of early "electronic editing" systems in the 1960s, by using multiple video recorders. Unfortunately, audio continued to be edited "the old fashion way" throughout the 1970s. With the advent of digital audio and video hard disk recording in the 1980s, extremely precise edits can now be accomplished in a fraction of the time it took previously. Edits can now be previewed and reversed if necessary, a difficult job if the tape was cut.

Professional video editing is done using time code recorded on every frame of the magnetic tape, allowing single frame accuracy. Audio editing is often carried out simultaneously with video editing. In the last half of the 20th century, we have seen the editing process evolve into a highly specialized art form. Editing is probably the most important aspect of storytelling, responsible for the cinematic masterpieces we see today.

EDIT POINT

The location in an audio or video program where a production event or change occurs (e.g., audio segue or video dissolve/wipe).

EDL (Edit Decision List)

A list of a video production’s edit points. An EDL is a record of all original videotape scene location time references, corresponding to a production’s transition events. EDLs are usually generated by computerized editing equipment and saved for later use and modification.

EFM (Eight to Fourteen Modulation)

Used on every compact disc for modulation and error correction.

EIA RS-170A

The timing specification standard for NTSC broadcast video equipment.

ELECTROFORMING

A means of creating a “father” metal master disc by electroplating nickel onto the glass master until a sheet of nickel has been built up to a usable thickness (typically 0.3mm). Although this metal master could be used as a stamper to replicate discs, it usually undergoes further processing to create a “mother” metal master disc from which stampers are then made.

EMPHASIS

In an effort to improve the already excellent signal-to-noise ratio of the compact disc, CDs (as well as digital tapes) can be recorded with emphasis. If used, the recording is made with a high frequency boost (called Emphasis ). During playback, a corresponding high frequency rolloff is applied (called Deemphasis ) and in theory, the signal-to-noise ratio is improved. An automatic data flag in the CD’s PQ subcode, tells the player when to apply the deemphasis. There have been many problems with the use of emphasis (loss of headroom, wrong PQ codes, inaccurate deemphasis circuits) and therefore most CDs made today do not use emphasis.

ENCODE

The process of combining separate signal components, e.g., red, green and blue, into one compositeanalog or digital video signal.

ENG

Acronym for Electronic News Gathering.

ENHANCING

Improving a video image by boosting the high frequency content lost during recording. There are several types of enhancement. The most common accentuates edges between light and dark images.

EXABYTE

System for recording/reading digital data using 8mm video cassettes. One of the preferred mediums for sending audio data to CD replicators.

FADE

The act of increasing or decreasing the voltage level of audio or video signals.

• In audio, a fade-in increases the sound level from silence and a fade-out decreases the sound level until it is no longer audible.
• In video, the act of dissolving a video picture to either a color, pattern or titles. Fading a video image is often used as an artistic tool in video productions, most commonly seen as a fade to black.

Audio fading is often used in conjunction with video fading causing the sound and image to fade simultaneously. (See AUDIO-FOLLOW-VIDEO)

FATHER

In disc replication, the name typically given to the metal master created in the first step of the electroforming process when the deposited nickel coating is removed from the glass master. The father is an inverted image of the glass master.

FBR (Fixed Bit Rate)

The standard method (as opposed to the more efficient VBR) of encoding a digital audio or video stream in order to reduce it’s subsequent file size. FBR encoders maintain a steady data rate regardless of the program content. (See VBR)

FIELD

One-half of a complete television picture consisting of one complete vertical scan of the video image containing 262.5 line for NTSC and 312.5 lines for PAL. Two fields make up a complete television picture frame. (See INTERLACING)

FILE SYSTEM

A data structure that translates the physical (sector) view of a disc into a logical (files, directories) structure, which helps both computers and users locate files. (See LOGICAL FORMAT)

FILL LIGHT

Commonly referred to as "scoops," they provide a soft-edged field of light used to provide additional subject illumination to reduce harsh shadows or areas not highlighted by the key light.

FILM CHAIN

Projectors, multiplexors and cameras, connected for the purpose of transferring film to video.

FIREWIRE

(See IEEE-1394)

FLICKER

A strobing picture artifact, similar to an old-time movie effect, mainly related to vertical syncs and video field display rates. Some flicker normally exists due to video interlacing, but is more apparent in 50 Hz systems (PAL) and when converting film (24 fps) to video (30 fps). Flicker may also be a problem when static computer images are transferred to video.

FLYING ERASE HEAD

Facilitates smooth, seamless edits whenever the camcorder recording begins. Without a flying erase head, a video "glitch" may occur at scene transitions. The erase head is mounted on the spinning (flying) video head drum.

FM (Frequency Modulation)

Frequency modulation is a process used for radio (FM broadcast), wireless microphone systems, television audio transmission and videotape recording. A low frequency (program) signal modulates (changes) the frequency of a high frequency RF carrier signal (causing it to deviate from its nominal base frequency). The original program signal is recovered (demodulated) at the receiver. This system is extensively used in broadcast radio transmission because it is less prone to signal interference and retains most of the original signal quality. In video, FM is used in order to record high quality signals on videotape.

FORMAT

A variety of formats are used to record audio and video. They vary by tape width: (8mm, 1/4 inch, 1/2 inch, 3/4 inch, 1 inch and 2 inch), signal form: (composite, Y/C, component), data storage type (analog, or digital) and signal standard (NTSC, PAL, SECAM).

FRAME

A complete video image consisting of 2 fields. Also used to describe the total visible area of a video image.

FRAME SYNCHRONIZER

A digital electronic device which synchronizes two or more video signals. The frame synchronizer uses one of its inputs as a reference and genlocks the other video signals to the reference’s sync and color burst signals. By delaying the other signals so that each line and field starts at the same time, two or more video images can be blended, wiped and otherwise processed together. (A TBC takes this a step further by synchronizing both signals to a stable reference, eliminating time base errors from both sources.)

FREEZE (Frame)

Special effect in which the picture is held as a still image. It is possible to freeze either one field or a whole frame. Freezing one field provides a more stable image if the subject is moving, however, the resolution of the video image is half that of a full frame freeze.

FREQUENCY RESPONSE

A measure of the quality of reproduction of various frequencies (audio and video) by a circuit or device. If the frequency response of either a audio or video processor is adequate, there is no deterioration in the sound or image quality at the bandwidth extremes.

• For audio, full bandwidth implies a frequency response extending from 20 Hz to 20,000 Hz or higher.
• For video, the NTSC broadcast bandwidth is 4.2 MHz and the PAL broadcast bandwidth is 5.5 Mhz.

GENERATION

The number of duplication steps between an original recording and a given copy. A second generation duplicate is a copy of the original master and a third generation duplicate is a copy of a copy of the original master, etc.

GENERATION LOSS

When an analog program material is duplicated, the second-generation copy is usually inferior in some way to the master.

• In audio, this degradation most often appears as added noise, higher distortion and altered frequency response.
• In video, this degradation appears as loss of detail, improper colors, sync loss, etc.

Limited frequency response of audio/video magnetic tape and imperfections in electronic circuitry are the main causes of generation loss. Higher performance formats (such as 1-inch) exhibit much less generation loss than more basic formats. Digital formats make generation loss negligible because each copy is essentially an exact duplicate of the original.

GENLOCK

A method of synchronization involving the generation of a video signal sync-locked with another signal. Because they are synchronized, a genlocked signal can be mixed with the original signal, allowing dissolves, wipes and other transition effects.

GHOSTING

A weak, secondary, ghost-like duplicate video image within another video image caused by the undesired mixing of the primary signal and a delayed version of the same signal.

GLASS MASTER

The disc on which the source data (from either PCM-1630 tape, Exabyte tape or CD-R) is imprinted as the first step in CD replication (mastering). The glass master is a glass plate, about 10” in diameter, coated with a light-sensitive material (photoresist). During mastering, the source signals are converted to the EFM coding format for the CD and fed to the special laser beam recorder (LBR) which etches very tiny pits on the material. The glass master is very delicate, and cannot be played. Succeeding steps in the process, called the “father”, “mother” and stamper , result in the metal forms which are capable of hot molding thousands of compact discs on the presses.

GREEN BOOK

(See CD-I)

GROUP DELAY

A phenomenon involving timing differences between video signal components. For example, a long cable run may introduce a substantial delay between the transmission of the color and brightness video information resulting in shadows.

HARMONIC DISTORTION

When any signal is passed through an electronic circuit, the signal may be changed in many ways.

• In audio, odd harmonics (third, fifth, etc.) produce harsh and unpleasant sounding audio.
• In video, the image may become blurred, noisy or contain shadows.

HEADER FIELD

Four bytes recorded at the beginning of each sector which tell the address of the sector (expressed as a Logical Block Number) and the mode in which the sector is recorded.

HDTV (High Definition Television)

A television format for producing high resolution video. Typically, these systems provide about 1125 lines of horizontal resolution (compared to 525 for NTSC and 625 for PAL) and an aspect ratio of 16:9, for image quality approaching 35mm film photography.

HELICAL SCAN

A method of recording video information diagonally on a tape, used in home and professional VCRs. High speed rotating video heads scan these diagonal video tracks, giving an effective tape speed much higher than the actual tape speed allowing more information to be recorded on a given length of magnetic tape.

HFS (Hierarchical File System)

Used by the Macintosh computer platform. HFS formatted CD-ROMs have the same file structure as an Apple hard disk.

HI-8

An improved version of the 8mm tape format capable of recording better picture resolution (definition). A higher-density tape is required which provides a wider luminance bandwidth, resulting in sharper picture quality (over 400 horizontal lines vs. 240 for standard 8mm) and improved signal-to-noise ratio. Camcorders using this format are very small, light and provide a picture quality equivalent to S-VHS.

HI-FI (High Fidelity)

Most commonly used to refer to the high quality AFM audio tracks recorded by many VCRs. These tracks provide audio quality approaching that of a CD. However, because they are combined with the video signal before recording, audio dubs using them are impossible without re-recording the video.

HIGH SIERRA FORMAT

The standard logical format for CD-ROM originally proposed by the High Sierra Group, on which the ISO 9660 standard is based; essentially identical to ISO 9660. The original High Sierra format is rarely used any longer.

HISS

The most common audible noise component in audio recording, stemming from a combination of circuit and tape noise. Several noise reduction systems are available, such as Dolby, DBX, DNR (Dynamic Noise Reduction), DNL (Dynamic Noise Limiter), to help alleviate such problems.

HORIZONTAL RESOLUTION

Rating of the fine detail (definition) of a TV picture, measured in scan lines. The more lines, the higher the resolution and the better the picture. A standard VHS format VCR produces 240 lines of horizontal resolution, while over 400 lines are possible with S-VHS and Hi-8 camcorders.

HORIZONTAL SYNC

The sync pulse signal produced at the beginning of each video scan line which keeps a video monitor’s horizontal scan rate in step with the transmission of each new line. (See BLANKING LEVEL)

HUE

Often used synonymously with the term tint. It is the dominant wavelength which distinguishes a color such as red, yellow, etc. Most commonly, video hue is influenced by:

• A camera’s white balance
• Scene lighting Video color processors such as the Video Equalizer are the main tools used to adjust and correct hue problems.

HYBRID DISC

Recordable disc on which one or more sessions are already recorded, but the disc is not closed, leaving space open for future recording. However, in popular use, the term "hybrid" often refers to a disc containing both Macintosh and DOS/Windows software platforms. The disc contains separate ISO 9660 and HFS partitions.

IEEE-1394

A fast universal digital interface used for transferring any type of digital information. Also known as FireWire and developed by Apple Computer.

IMAGE PAC

Photo CD term which describes the set of five versions of the same image, at varying resolutions.

IMAGE STABILIZATION

Camcorder feature which takes out minor picture shakiness, either optically or electronically.

IMPEDANCE MATCHING

A video signal occupies a wide spectrum of frequencies, from nearly DC (0 Hz) to 6 MHz. If the output impedance of either the video source, cable or input impedance of the receiving equipment are not properly matched, a series of problems may arise. Loss of high frequency detail and color information as well as image instability, oscillations, snow, ghost images and component heat-up may result. Proper connections and cable types provide correct impedances. (See LOAD RESISTANCE)

INDEXING

Creation of a data index to speed up search and retrieval on CD media.

INSERT EDITING

Camcorder/VCR feature which allows a user to insert new audio/video segments into the middle of a previously recorded tape. Some camcorders insert both audio and video simultaneously; others can insert audio and/or video separately.

INTERLACING

A system developed for television which divides each video frame into two fields. This is done by first drawing one field consisting of an image’s odd scan lines (1, 3, 5... 525) and then drawing the remaining even scan lines (2, 4, 6...), interweaving both fields. Interlacing reduces the perception of screen flicker. Interlacing can cause annoying effects with images such as computer generated text and graphics when transferred to video.

ISO 9660

An international standard defining the file and directory structures for CD-ROM. It defines such items as file naming conventions and subdirectory levels, etc. An ISO 9660 formatted CD-ROM will function on any computer platform containing the appropriate driver software. ISO 9660 data starts at track time 00:02:16 or sector 166 (logical sector 16) of track one. For a multisession disc, the ISO 9660 data will be present in the first data track of each session containing CD-ROM tracks.

ISO 9660 FORMAT

An international standard specifying the logical format for files and directories on a CD-ROM.

ISO 9660 IMAGE

(Also CD-ROM image, image, disc image). A single large file which is an exact representation of the whole set of data and programs as it will appear on a CD, in terms of both content and logical format.

ISO 9660 w/Rockridge Extensions

A revision to the ISO specification to allow for UNIX specific exceptions to the ISO 9660 standard.

ISO INTERCHANGE LEVELS

There are three methods of recording and naming files on disc under the ISO 9660 standard. There are three nested, downward-compatible Levels.

In Level 1 (the most restrictive):

• Each file must be written on disc as a single, continuous stream of bytes - files may not be fragmented or interleaved.
• A filename may not contain more than eight d-characters.
• A filename extension may not contain more than three d-characters.
• A directory name may not contain more than eight d-characters.

In Level 2, again, each file must be written on disc as a single, continuous stream of bytes.

In Level 3 there are no restrictions.

ISRC (International Standard Recording Code)

A unique identifying designation usually assigned by the issuing record company for each audio track on a compact disc. The code is made up of: Country Code (2 ASCII characters), Owner Code (3 ASCII characters), Year of Recording (2 digits) and Serial Number (5 digits).

J-CARD

A term used to describe the cardboard label insert used in most recordable audio and video media cases. The name derives from the way these labels are folded to fit inside their respective media cases.

JITTER

Timing innacuracies in the transmission and reception of a digital bit-stream.

• In audio, timing variations in the clock reference of digital audio signals, which cause distortion.
• In video, small, rapid variations in a waveform or image due most often to mechanical disturbances. (See TBC)

JPEG (Joint Photographic Experts Group)

The name applied to the digital compression standard for still video images allowing them to occupy less memory or disk space. Like the MPEG standard, it includes options for tradeoffs between storage space and image quality.

KEY LIGHT

The term used to describe a subject’s main source of illumination. When shooting outdoors, the key light is the sun.

LANC

(See CONTROL-L)

LAND

A non-indented area on an optical medium such as a CD or DVD disc. For reading purposes, a directed laser beam is either reflected off the land or absorbed by indentations called pits. Using various algorithms, the reflections are converted into 0 or 1 data bits. (See also PIT)

LASER (Light Amplification by Stimulated Emission of Radiation)

A means of generating coherent light which can be accurately focused to a very small spot size, ideal for reading or writing optical disc media.

LASERDISC

12" consumer optical disc format used for the storage of audio and video signals. The laserdisc utilizes a high quality analog video signal capable of >400 lines of horizontal resolution as well as analog and/or digital audio tracks. Both CAV and CLV recording methods have been employed in the making of these discs over the years. The laserdisc is largely being replaced by the all digital DVD format.

LAVALIERE MICROPHONE

Small microphone worn around the neck or clipped to clothing.

LCD (Liquid Crystal Display)

A screen for displaying text/graphics based on a technology called liquid crystal, where minute currents change the reflectiveness or transparency of the screen. The advantages of LCD screens are: very small power consumption (can be easily battery driven) and low price of mass produced units. Its disadvantages presently include narrow viewing angle, somewhat slower response time, invisibility in the dark unless the display is back-lit, difficulties displaying true colors and resolution limitations.

LEAD-IN

An area at the beginning of each session on a recordable compact disc which is left blank for the session’s Table of Contents or TOC. The lead-in is written when a session is closed, and takes up 4500 sectors on disc (1 minute, or roughly 9 megabytes). The lead-in also indicates whether the disc is multisession by giving, if the disc is not closed, the next recordable address on the disc.

LEAD-OUT

An area at the end of a session which indicates that the end of the data has been reached; there is no actual data written in the lead-out. The first lead-out on a disc is 6750 sectors (1.5 minutes, about 13 megabytes) long; any subsequent lead-outs are 2250 sectors (0.5 minute, about 4 megabytes) .

LFE

Low Frequency Effects; name given to the dedicated subwoofer channel in Dolby Digital and DTS audio formats.

LINEAR EDITING

Editing using media like tape, in which material must be accessed in order (e.g., to access scene 5 from the beginning of the tape, one must proceed from scene 1 through scene 4). (See NONLINEAR EDITING)

LINE COMPENSATION

Use of a video line amplifier to pre-compensate for high frequency video signal transmission losses resulting from long distance cable runs (several hundred meters) by boosting those signal frequencies most effected. Without such compensation, deterioration is manifested as loss of fine details and color distortion.

LINKED MULTISESSION

A disc containing more than one recorded session, in which all (or selected) data from the various sessions can be seen as if it had all been recorded in a single session. (See MULTISESSION)

LOAD RESISTANCE

The impedance or resistance (load) that a cable places on a signal being transmitted through it. In the case of a high frequency signal, signal-to-cable matching is essential to prevent signal deterioration.

The cable should be terminated by a specific load resistance, usually 50 or 75 ohms. Improper cable loading results in signal distortion, ghost images, color loss and other adverse phenomena. Most video inputs have the proper termination built in.

LOGICAL BLOCK

The smallest addressable space on a disc. Each logical block is identified by a unique Logical Block Number (LBN), assigned in order starting from 0 at the beginning of the disc. Under the ISO 9660 standard, all data on a CD is addressed in terms of Logical Block Numbers.

LOGICAL FORMAT

A file system such as ISO 9660 translates the sector-by-sector view of a compact disc into a virtual "tree" of directories and files, which makes it easier for both humans and computers to use the information on the disc. UDF is another example of a file system which can be used to write CDs.

LOOPING

A term used to describe the chaining of a video signal through several video devices (distribution amplifiers, VCRs, monitors, etc.).

A VCR may be hooked up to a distribution amplifier which is supplied with a video input connector and a loop output connector. When a signal is fed to the distribution amplifier, it is also fed unprocessed to the loop output connector (parallel connection) on the distribution amplifier. In turn, the same signal is fed to another device which is attached to the first one and so on. Thus a very large number of VCRs or other video devices can be looped together for multiple processing.

LTC (Longitudinal Time Code)

SMPTEtime code standard usually recorded onto the linear audio track of a VCR or audio tape machine.

LUMINANCE

That part of a video signal relating to the degree of brightness at any given point in the video image. A video signal is comprised of luminance, chrominance (color information) and sync. If luminance is high, the picture is bright and if low, the picture is dark. Changing the chrominance does not affect the brightness of the picture.

LUMINANCE NOISE

Noise which manifests itself in a video picture as white snow, typically caused by one of the following situations:

• Low signal level due to poor lighting conditions
• Poor video signal processing
• Low quality videotapes
• Excessively long video cables used without pre-compensation
• Dirt on the video recorder heads which interferes with reading and writing
• Over-enhancement of the video signal

LUX

A measurement of light intensity, which is used in photography for the comparison of camera sensitivities. (1 Footcandle = 10.76 Lux)

MII

Portable, professional video component camera/recorder format, utilizing 1/2" metal particle videotape. JVC’s answer to Sony’s Betacam format.

MADI

(AES10) multichannel digital audio interface that supports 56 channels.

MASTERING

Technically, refers to the process of creating a glass master from which compact discs will be reproduced in quantity. In professional circles, the term is loosely used to refer to the process of preparing audio and video information for the pre-mastering phase.

MATRIX SWITCHER

A device which uses an array of electronic switches to route a number of audio/video signals to one or more outputs in almost any combination. Production quality matrix switchers perform vertical interval switching for interference free switching. Matrix switchers may be operated with RS-232 or RS-422 controls, enhancing flexibility.

MEDIA CONVERSION

The process of converting data from one type of media to another for premastering and mastering. Premastering software typically requires input data on hard disk. 8mm tape and compact disc are preferred as input media for the mastering process.

METALIZING

A process in which a thin layer of aluminum is deposited on a clear plastic disc after it has been injection molded. The usual deposition method is by sputtering, although vacuum vapor deposition or wet silvering can also be used.

MICROPHONE PREAMPLIFIER

A microphone is a device which converts sound waves to electrical impulses (transducer). Microphones typically generate very low signal levels requiring low noise, high fidelity, pre-amplification to boost the output signal to a level compatible with audio amplifier circuitry. Good microphone preamplifiers provide precise matching of microphone impedance and low noise electronic components.

MICROPHONE IMPEDANCE

In order to obtain the highest quality output signal from a microphone, a preamplifier input should provide a load (impedance) which exactly matches a microphone’s output impedance. Microphone output impedances vary from 150 ohms to several megohms.

MIDI (Musical Instrument Digital Interface)

A universal electronic computer-generated data language used to compose/record musical performances and sound effects using various keyboards, synthesizers and other electronic equipment.

MIXED-MODE

A compact disc including both computer data and CD-DA tracks. The data is all contained in Track #1 and the audio in one or more following tracks (#2-99).

MIXING

The blending of two or more audio or video signals to generate a combined signal.

MO (Magneto Optical)

(See CD-MO)

MODE

There are two recording modes for compact discs; Mode 1 and Mode 2.

MODE 1

Most common CD-ROM data format. In Mode 1, 288 bytes of each sector are used for storing three layers of error correction code, leaving the remaining 2048 bytes per sector for user data.

MODE 2

Data format utilized in CD-I and CD-ROM XA. Mode 2 has two forms. Form 1 is similar to Mode 1, but storing only two layers of error correction code. Form 2 is used for recording information such as audio or compressed video which do not require such extreme precision. Since less error correction is needed, more bytes in the sector can be freed for information storage, resulting in a data area of 2336 bytes per sector.

MOIRÉ

A distracting wavy effect produced when converging lines in a video image are nearly parallel to a monitor’s scanning lines.

MONITOR

A display that gets its signal directly from a camera or VCR, as opposed to a television, which relies on RF signals, such as those from cable television or broadcast. A monitor uses composite (RCA-style), S-video (Y/C) and/or BNC video jacks. (See ANALOG MONITOR)

MOSAIC

Special effect in which the picture is divided up into tiles.

MOTHER

In disc replication, the name typically given to the metal master created from the nickel coating which is deposited and then separated from the “father” metal master. The mother is a positive image, identical to the glass master. Multiple stampers are then made from the mother.

MOUNT

To install a CD or DVD disc so that the computer recognizes its presence and can read data from it.

MP3 (Moving Picture Experts Group 1, Layer 3)

Abbreviated term given to a method of compressing audio files. MP3 compression is accomplished by relying on a natural phenomenon called psychoacoustic masking to reduce the amount of data by as much as a factor of 10, inevitably degrading the sound quality somewhat. On a CD, each minute of stereo audio takes up about 10MB (MegaBytes) of space. Very few people would want to download a 40MB file just to hear four minutes of music. With MP3 compression, the same four minute song takes up about 4MB. This is a much more practical size for sending over the Internet.

MPEG (Motion Picture Experts Group)

The name applied to the digitalcompression standard for moving video images allowing them to occupy less memory or disk space. Like the JPEG standard it includes options for tradeoffs between storage space and image quality.

MULTI-STANDARD

A monitor which synchronizes to different video signal standards such as NTSC and PAL. (See ANALOG MONITOR)

MULTIMEDIA

A somewhat ambiguous term that describes the ability to combine audio, video and other information with graphics, control, storage and other features of computer-based systems. Applications include presentation, editing, interactive learning, games and conferencing. Current multimedia systems also use mass storage computer devices such as CD-ROM.

MULTIREAD

An OSTA standard for CD-ROM and DVD-ROM drives. Drives which follow the MultiRead standard can read commercial CDs (audio and data), CD-R and CD-RW discs. They can also read discs written in fixed or variable-length packets.

MULTISCAN MONITOR

A monitor (also referred to as multi-sync or multi-frequency) which synchronizes to different video signal sync frequencies, allowing its use with various computer video outputs. (See ANALOG MONITOR)

MULTISESSION

Specification which allows additional data to be appended to previously recorded disc sessions. All of the data in the various sessions, look as if it had been recorded in one single large session. If the data between sessions is linked (also referred to as a linked session), all data on a multisession disc may be seen as part of a single logical structure when read on a compatible CD-ROM drive. The multisession specification is part of the Orange Book standard.

NEGATIVE EFFECT

Special effect in which either blacks and whites are reversed or colors are inverted. For example, red becomes a blue-green, green becomes purple, etc. An electronic color filter can be used for fine adjustment of the hues.

NOISE

A general term used in electronics to indicate any unwanted electrical signal, unrelated to the original signal.

• In audio, noise is generally manifested as hiss and static.
• In video, noise is generally manifested as snow, graininess, ghost images or picture static induced by external sources such as the national power-line grid, electric motors, fluorescent lamps, etc.

NOISE GATE

A device used to modify a signal’s noise characteristics.

• In audio, a noise gate provides a setable signal level threshold below which all sound is removed.
• In video, noise gates provide optimal automatic suppression of snow (signal noise level).

NOISE REDUCTION

An electronic process used to reduce noise levels in audio and video signals.

• In audio, the most effective systems employ an encode/decode scheme, performed before and after recording, such as the Dolby audio noise reduction system. Noise reduction can be performed on an existing audio signal using systems such as DNR (dynamic noise reduction) but are less effective because they also affect the audio signal.
• In video, the most effective noise reduction is accomplished by digitizing the video signal and carrying out a computerized pixel by pixel analysis of the data.

NONLINEARITY

The amount by which a measured video signal output differs from a standard video signal output. The greater this deviation, the greater the video signal distortion and possibility of luminance and chrominance problems.

NONLINEAR EDITING

The process of editing using rapid retrieval (random access) computer controlled media such as hard disks, CD-ROMs and laser discs. Its main advantages are:

• Allows you to reorganize clips or make changes to sections without having to redo the entire production.
• Very fast random access to any point on the hard disk (typically 10-20 ms)

(See EDITING)

NORMALIZATION

An automatic process available on some DAWs, whereby the gain of all program material can be adjusted so the greatest peak level will just arrive at 0 dBFS. Normalization can be extremely damaging to digital audio if misued. For instance, normalization should never be used to correct the apparent loudness of different tracks on a music album. Truncation distortion may also be introduced if improperly applied.

NTSC (National Television Standards Committee)

Color TV broadcasting standard used mainly in North America, Central America, Japan, and parts of South America, featuring 525 lines per frame and 60 frames per second. (See PAL and SECAM)

ON-THE-FLY

To write "on-the-fly" means to write data to CD, referenced in a virtual image without first writing a real ISO 9660 image.

ORANGE BOOK

(See Multisession)

OVERLAY

Keyed insertion of one image into another. Overlay is used for example, to superimpose computer generated text on a video image, for titling purposes. The overlay procedure requires synchronized sources for proper operation.

OVERSCAN

Video images generally exceed the size of the physical screen. The edge of the picture may or may not be displayed, to allow variations in television sets. The extra area is called the overscan area. Video productions are planned so critical action only occurs in the center safe title area. Professional monitors are capable of displaying the entire video image including the overscan area.

P-CHANNEL

One of the CD subcode channels. The P-channel is used to indicate the gaps between tracks on the disc.

P2

Sony’s wired professional edit control protocol. Using an RS-422 serial data path, P2 allows multiple machines to be addressed on the same line and is a defacto standard used on most VTRs in professional use.

PACKET WRITING

Describes a method of adding data incrementally to a disc in small or large quantities called “packets”. It is possible to even record a single file at a time. Unlike previous methods of writing data to CD (disc-at-once and multisession), packet writing does not waste much time or disc space and there is no arbitrary limit to the number of packets that can be written to a CD.

PAL (Phase Alternate Line)

Color TV broadcasting standard used mainly in Western Europe, Australia, most of Asia, and parts of South America and Africa, featuring 625 lines per frame and 50 frames per second. (See NTSC and SECAM)

PANASONIC 5-PIN

(See CONTROL-M)

PCM (Pulse Code Modulation)

Digital audio recording format used since the late 1970s. PCM simultaneously captures all bits of a given word length (8 to 48-bits) at various standardized sampling frequencies (11kHz to 192kHz). The standard CD, co-developed by Philips and Sony, uses a 16-bit word length and a sampling rate of 44.1kHz).

PEDESTAL

The pedestal is a small DC voltage step within the video signal indicating a picture’s black level and is used as the reference in a standard video signal for white and all gray levels.

PHASE ERROR

A change in the color subcarrier signal which moves its timing out of phase, i.e., it occurs at a different instant from the original signal. Since color information is encoded in a video signal as a relation between the color subcarrier and the color burst phase, a deviation in the color subcarrier phase results in a change in the image’s hue.

PHOTO CD

A compact disc format developed by Kodak and Philips, based on the CD-I Bridge specification, used to store photographic images on a CD-ROM for display and printing. Up to 100 high resolution images can be stored on a Photo CD.

PHTHALOCYANINE

An organic dye used to form the data layer in some CD-R discs. Mitsui Toatsu Corporation holds the patent on this dye, but has licensed its formula to some other manufacturers.

PICTURE SHARPNESS

The fine details in a video picture. A picture appears sharp when it contains fine details and has good contrast. Picture sharpness is easily lost during the record/playback process. Advanced video enhancement equipment is used to improve picture sharpness, especially contrast, and can precompensate for potential losses which might alter an image during processing.

PIP (Picture In Picture)

Special effect in which one video image is inserted within another allowing several video images to share a single screen.

PIT

An indentation in an optical medium such as a CD or DVD disc. For reading purposes, a directed laser beam is either absorbed in the pits or reflected off non-indented areas called land. Using various algorithms, the reflections are converted into 0 or 1 data bits. (See also LAND)

POST-PRODUCTION

All production work done after the raw video footage and audio elements have been resorded. Editing, titling, special effects insertion, image enhancement, audio mixing and other production work is done during post-production.

POSTERIZATION

Special effect in which the picture is reduced to a small number of chrominance or luminance levels by removing any fine gradations of color and brightness, resulting in an oil painting effect.

PQ SUBCODE

The compact disc format contains a number of subcode areas named with letters from P to W. The key subcode areas are named P & Q and contain data pertaining to every track’s location on the CD, eq emphasis and copy protection. The mastering engineer performs PQ coding just before cutting the CDPreMaster.

PRE-ENHANCEMENT

In many situations, video losses can be anticipated, allowing signal pre-compensation in a way that partially corrects for the losses. (See LINE COMPENSATION)

PRE-MASTERING

The process of formatting data into the exact image that will appear on an audio CD or CD-ROM. This includes dividing the data into sectors and recording those sectors with the appropriate header (address) and error correction information and adhering to the required file structure (i.e., ISO 9660). In the case of recordable CD systems, premastering and mastering are done in one operation, resulting in a ready-to-read compact disc. A premastered image is ready to be mastered and replicated.

PREVIEW BUS

A processor function allowing the operator to select any incoming video source for viewing prior to actual use. Typically, each signal can be previewed on its own monitor. This is an effective method to check work before going "on the air".

PRIMARY COLOR

One of three basic colors used in most TV and video systems. These base colors consist of red, green and blue.

PROGRAM AREA

The largest area on a compact disc containing the audio or CD-ROM information.

PROGRAM BUS

Similar to the preview bus in concept except that the resulting output is the final signal which goes "on the air".

Q-CHANNEL

One of the CD subcode channels. The Q-channel is used to store timecode addresses and the disc’s Table of Contents.

RANDOM ERASE

Part of the UDF 1.5 specification. Random erase describes the ability to erase one file at a time from a CD-RW disc, just as you would on a hard disk. (See Sequential Erase

RASTER

The pattern of parallel horizontal scanning lines, traced by a video monitor’s electron beam, making up a video image.

RCA (connector)

A type of connector used on all consumer VCRs and camcorders to carry the standard composite video and audio signals.

RC (Rewriteable Consumer) Time Code

A time code system, available on 8mm and Hi-8 tape formats only. The code can be added either before or after video recording without affecting the video or audio signals.

REAL TIME COUNTER

Any display showing tape length recorded (elapsed time) or remaining in an hours-minutes-seconds format.

RECORDABLE DISC

Media used in recordable CD systems. The blank disc is made of a bottom layer of polycarbonate, with a preformed track spiral which the recording laser follows when inscribing information onto the disc. This type of disc is therefore also called pre-grooved. A translucent layer of recordable material is laid on top of the polycarbonate, then a reflective layer of gold. On top there are thin layers of lacquer and label.

RED BOOK

(See CD-DA)

REDITHERING

The process of adding random data or noise to an analog audio signal for the purpose of moving data from the least-significant bits to the "higher" bits in a digital word. (See DITHER)

REGION CODING

A method by which DVD playback is restricted by geographic region. For example, DVDs and DVD players sold in the United States, Canada, and Mexico are usually coded for Region 1. A Region 2 disc from Japan will not play on a Region 1 player, unless that player has been specially modified to do so.

REMOTE SOCKET

A socket on a VCR or video camera which when connected, permits remote control of the unit. Remotes may be wired or wireless (infrared) and allow such control as play, pause, record, fast forward and rewind. (See CONTROL-S)

REPLICATION

Making multiple copies of a compact disc with a machine press.

REQUANTIZING DISTORTION

Distortion caused by shortening the word length of a digital audio sample as a result of truncation. Distortion occurs because the intervals at which the waveform are quantized become larger, changing the original waveform.

RESOLUTION

A measure of the ability to reproduce video detail. Generally, referred to as horizontal resolution and evaluated by establishing the number of horizontal lines which are clearly discernible on a test pattern. Resolution specifications are not very well standardized, especially as stated in connection with monitors. Using the rule of thumb of 80 lines per MHz of bandwidth, the VHS and 8mm tape formats typically achieve 240 lines of resolution, S-VHS and Hi-8 achieve 400, and broadcast achieves about 330. (See DEFINITION)

RF (Radio Frequency)

A term used to describe the radio frequency signal band of the electromagnetic spectrum (about 3 MHz to 300 GHz). RF is used to carry modulated television signals and RF I/O connectors for cable TV and antennas, can be found on the back of most monitors and VCRs.

RF DISTRIBUTION

The process of supplying an RF signal to several devices simultaneously.

RF MODULATION

The process of combining a video signal with an RF source so the result can be transmitted to a television or VCR.

RGB (Red/Green/Blue)

The raw basic Red, Green and Blue signal components of a color video signal source such as a camera or computer video board. Each of these include luminance information so that if you view them separately, you will see a shade of B/W image (I am ignoring the need for sync at the moment). Using a color encoder, in conjunction with sync information, a complete composite video signal comprising luminance and chrominance can be generated.

Each component of an RGB signal uses a lot of bandwidth which is why the YIQ and YUV matrixed signal formats were developed for NTSC and PAL video systems respectively. (See COMPOSITE VIDEO and COMPONENT VIDEO)

RS-232/RS-422

Computer communication standards used in video for the control of certain video equipment. Computer controlled VCRs, edit controllers, switchers and other studio equipment can commonly be found in professional video studios. Successfully linking two devices, at the very least, requires that they use the same communication protocol.

RSDL (Reverse Spiral Dual Layer)

A technique by which a movie is split across two layers of a single DVD disc and is joined together for continuous playback. Allows longer movies (or movies with extra content) to be shown uninterrupted on a single side of a disc.

SAFE TITLE AREA

Generally, the center 80% of the entire video image area or that area which will display legible titles regardless of how a TV monitor is adjusted.

SCART

An audio/video connector used in consumer equipment, especially in Europe. The SCART connector's 21 pins carry two audio in and out channels, video in and out channels, RGB signals, ground and some additional control signals. Only one SCART-to-SCART cable is needed to connect two VCRs or VCR to a monitor thereby avoiding the need for multiple cables.

SCMS (Serial Copy Management System)

A technology introduced to tackle piracy problems. It allows the consumer to only make a single digital copy for personal use, from a copyrighted source.

SECAM (Sequential Couleur A’memorie)

Color TV broadcasting standard used mainly in France, Eastern Europe, and parts of Asia and Africa. In countries using the SECAM standard, most video production is done using PAL and converted to SECAM prior to transmission. (See NTSC and PAL)

SECTOR

The smallest recordable unit on a compact disc. A disc can contain [(75 sectors per second) x (60 seconds per minute) x (number of minutes on disc)] sectors. The amount of data contained in the sector depends on what physical format and mode it is recorded in. For regular CD-ROM (Mode 1) data, you can fit 2048 bytes (2 kilobytes) of data into a sector.

SEG (Special Effects Generator)

Device designed to generate special effects. The simplest devices process a single video signal, change its color, generate sepia tones, invert the picture to a negative, posterize the image and fade or break up the image into various patterns. More sophisticated equipment uses several video sources, computer-generated graphics and sophisticated animation with digital effects.

SEPIA TONE

A process used in photography to generate an overall brownish tone in pictures giving them an "antique" appearance. The same idea has been electronically adapted for video production where a black and white image can be sepia colored.

SEQUENTIAL ERASE

Erasing or reformatting an entire CD-RW disc so that it can be re-used. (See Random Erase)

SERIAL PORT

A computer I/O (input/output) port through which the computer communicates with the external world. The standard serial ports use RS-232 or RS-422 protocols.

SESSION

Data on a compact disc which includes lead-in, program data and lead-out format structures. Contrast the recording structure of a pressed CD-ROM or a CD-R written in disc-at-once mode that contains just one continuous session.

SHOTGUN MICROPHONE

Long, highly directional microphone designed to pick up sounds from a distance, directly in front of it, while rejecting sound from all other directions. Named for its appearance.

SIGNAL-TO-NOISE (S/N)

The ratio in decibels, of an audio or video signal, between the signal’s maximum peak-to-peak signal voltage and the measured voltage of what remains when the signal is removed, (i.e., the ratio of the signal to that of the noise floor).

• In audio, the higher the ratio, the cleaner the sound. Audio S/N ratios vary tremendously from compact discs/camcorder AFM Hi-Fi tracks (typically 90 dB) to VCR linear tracks (typically 40 dB).
• In video, the higher the ratio, the less snow is visible.

SMPTE

Acronym for the Society of Motion Picture and Television Engineers.

SMPTE Time Code

SMPTE is time code recorded on an audio channel of a tape and is used to label each block or frame of a tape with a unique identifying address. Commonly used when referring to either DAT or U-Matic tape.

SNOW

A general term used to describe interference in a video image. It manifests as random colored or black and white dots. (See LUMINANCE NOISE)

SOLARIZATION

Special effect in which the lightest and darkest values of a picture are made dark while the middle tones become light.

SPARS CODE

Acronym for the "Society of Professional Audio Recording Services". The SPARS code was developed at the advent of the digital audio revolution in order to inform consumers of the format origin of audio recordings distributed on digital media such as the compact disc. The codes and their definitions follow:

DDD

Digital recorder used during recording, mixing and/or editing and mastering.

ADD

Analog recorder used during recording; digital recorder used during subsequent mixing and/or editing and during mastering.

AAD

Analog recorder used during recording and subsequent mixing and/or editing; digital recorder used during mastering.

S/PDIF (Sony-Philips Digital Interface)

Acronym for the dual-channel digital audio interface defined by Standard IEC-958, differing only slightly from its professional sibling - AES/EBU. It is usually found on consumer equipment with connections made via RCA (coaxial) connectors. (See AES/EBU)

SPECIAL EFFECTS

Artistic video effects used to enhance a video production by creating drama, enhancing the mood or furthering the story. Special effects may vary from the limited addition of patterns or the mixing of several video images together, to sophisticated digital effects such as picture compression, page flipping and three-dimensional effects. Special effects are usually created using SEGs.

SPLIT SCREEN

Special effect which allows the viewing of two video images on-screen simultaneously, either side by side or above and below.

STEREO MIXING

Simultaneous processing of both left and right audio channels. (See MIXING)

STROBE

Special effect in which a video frame is periodically held for a finite time until another frame is held.

SUPERIMPOSE

To place in front of video, e.g., placing text over a video signal.

S-VHS (Super-VHS)

An improved version of the VHS tape format capable of recording better picture resolution (definition). The two formats are incompatible although S-VHS equipment can record and play standard VHS tapes. A higher-density tape is required which provides a wider luminancebandwidth, resulting in sharper picture quality (> 400 horizontal lines vs. 240 for standard VHS) and improved signal-to-noise ratio. Because the equipment is usually smaller and lighter than 3/4" video equipment, it is ideally suited for ENG/EFP applications.

S-VHS-C (Super VHS-C)

An improved version of the VHS-C tape format capable of recording better picture resolution (definition).

S-VIDEO (Separated Video)

Describes a system of electronics, plugs and jacks used to interconnect camcorders, VCRs and TV monitors, which keep compositechrominance and luminance information separate. Also called Y/C connectors (luminance/chrominance), this system greatly improves picture quality by keeping any signal interaction (degradation) to a minimum.

SWITCHER

General term for a device used to select different signals (audio, video or RF) from various sources.

SYNC (Synchronization)

A term used in electronics to describe the precise alignment of two signals or functions.

• In audio, synchronization usually refers to the locking of audio equipment to other audio or video equipment in order to do audio post-production.
• In video, sync signals is an essential element for maintaining the proper clocking of video signals. The sync signal is used by a monitor to know where and when to draw the on-screen video image.

SYNC RESTORATION

A process which replaces distorted and missing sync information by checking incoming sync, analyzing the frequencies involved and generating new fully restored sync.

SYNCRO-EDIT

Wired control protocol which activates/deactivates a VCR’s record pause function. Many non-compatible versions of this protocol exist.

SYNC STRIPPING

A process which separates sync from the rest of the video signal for timing correction, clamping and other purposes.

TABLE OF CONTENTS

(See TOC)

TALENT

A term used to refer to all on-camera human subjects in a video production, regardless if they have any or not.

TALLY LAMP

A signal lamp or LED installed on a video camera which informs performers and crew members when the camera is "live".

TBC (Time Base Corrector)

A device used to rectify any problems with a video signal’s sync pulses by generating a new clean time base, then synchronizing any other incoming video to this reference.

TELECINE

Telecine is a term used to describe a device used to convert film to video. In advanced telecine machines, the movie film is digitally sampled and converted to video, frame by frame in real-time. Frame rate is the biggest problem encountered in film-to-video conversion. Movie film has a frame rate of 18, 24 or 30 fps (frames per second) contrasting with the 30 and 25 fps video frame rates of NTSC and PAL respectively. With NTSC, every fifth film frame is repeated when transferred to video. (See FLICKER)

TELE-PROMPTER

A device for displaying large, readable text on a partially transparent screen for video production. The tele-prompter uses a monitor mounted under the camera lens, facing up, and a mirrored glass which reflects the monitor’s image toward the talent. Since the camera shoots through the mirrored glass and the mirrored glass is transparent to the camera, the talent can look directly into the camera lens as they read the script from the glass.

TERMINATION SWITCH

A switch that connects and disconnects a load resistance to a video input, used to terminate the line. In order for a video signal to be correctly transmitted without loss, proper end of line impedance is essential. A 50 or 75 ohm resistor is usually employed to accomplish this. When the termination switch is off, the unterminated video signal is looped to the next device where the signal can be transmitted in parallel. The final device in the chain must be terminated using the termination switch. (See LOAD RESISTANCE)

TEST PATTERN

A chart with special patterns, placed in front of a television camera to generate a standard reference signal that can be used to adjust the camera and all equipment downstream.

THX

A set of quality-control standards pioneered by Lucasfilm, named for one of George Lucas’ early student films "THX-1138". Encompassing theatrical presentation, home playback, and video mastering, "THX Certification" means many different things. Home theater components, for example, are tuned in such a manner to compensate for differences between theatrical and home playback.

TIME CODE

A digital code number recorded onto a videotape for editing purposes. When decoded, the time code identifies every frame of a videotape using digits reading hours:minutes:seconds and frames. Each individual video frame is assigned a unique address, a must for accurate editing. The three time code standards used for audio and video are VITC, LTC and RC.

TITLING

The addition of text, symbols and graphic elements to a video image. Titles may be added to a video scene during shooting or in post-production. Sophisticated titling devices allow the user to prepare text and graphics in various sizes, fonts and colors to be triggered later, one-by-one, at appropriate places within a production. Many video cameras include basic titlers or permit externally-generated titles to be mixed with the video image during shooting.

TOC (Table of Contents)

That part of a CD’s lead-in data which shows the number of tracks, their starting locations and the total length of the data area of the disc. The TOC does NOT show the length of each track, only its starting point.

TRACK-AT-ONCE

Mode of writing that allows a session to be written in a number of discrete write events called tracks. The mode mandates a minimum track length of 300 blocks (4 seconds), which equates to around 700KB, and a maximum of 99 tracks per disc. The disc may be removed from the writer and read in another writer before the session is closed (‘fixated’).

TRACKING

The angle and speed at which the tape passes the video heads. Due to small differences in head-to-tape alignment between VCRs, it is sometimes necessary to adjust the tracking control on a VCR when playing a tape recorded on another deck.

TRANSCODER

A device used to convert from one component format to another or one video standard to another. (e.g., PAL to SECAM)

TRANSFER RATE

The amount of data which is transferred from a CD-ROM to the computer. The CD-ROM transfer rate is limited by the speed at which the disc rotates in the drive. The conventional CD-ROM transfer rate is approximately 150 kilobytes/sec, referred to as 1x. Therefore, a quadruple speed (4x) CD-ROM drive can transfer data at a rate of 600 KB/sec.

TRUNCATION

The shortening of a digital word, wherein data belonging to the least-significant bits is lost.

UDF (Universal Disk Format)

An international standard defining the file and directory structures for optical media (such as CD-ROM and DVD). Developed by the Optical Storage Technology Association (OSTA), UDF has several advantages over the ISO 9660 file system used by standard CD-ROMs. It was designed for read-write interoperability between all the major computer operating systems as well as compatibility between rewritable and write-once media. The standard allows for efficient recording of small packages of data, using incremental packet writing.

UNDERSCAN

The opposite of overscan. In underscan, a video or computer image is reduced so that all four edges are visible on-screen, leaving it surrounded by black borders. Underscan is used to show what is happening in the blanking period and at the beginning and end of scan lines and frames. Underscanning can uncover latent image problems for identification and correction.

UPC (Universal Product Code)

A unique thirteen-digit inventory tracking number assigned to a compact disc by the Uniform Code Council to allow tracking when sold commercially. The number is written in the disc’s Table of Contents. The European equivalent is known as the EAN.

UV22

A proprietary process developed by Apogee Electronics, similar in concept to dither, that adds a high-frequency, narrowband signal just below half the digital sampling frequency (Nyquist frequency): around 22kHz for 44.1kHz systems such as DAT and CD.

VBR (Variable Bit Rate)

A more efficient method (as opposed to FBR) of encoding a digital audio or video stream in order to reduce it’s subsequent file size. The bit rate of an encoded audio/video file is the number of bits (binary digits - 0s or 1s) that are required to store 1 second of program.

• In audio, an MP3 file at 128kbps requires 128,000 (ish!) bits to store 1 second of audio. Using psychoacoustic algorithms, a Variable Bit Rate encoder varys the bit rate depending on how much information is needed to only store the most audible portion of the signal from moment to moment. Since silence doesn’t contain very much information, a VBR encoder just stores a code meaning “'x' seconds of silence” rather than storing thousands of zeros.
• In video, a VBR encoder uses algorithms which only store the changes from frame to frame rather than the entire video scene.

VERTICAL INTERVAL SWITCHING

In practice, randomly switching from one video signal to another, will often result in a jump in the picture upon playback. The problem is compounded when the tape is copied. To avoid this problem, switching is best performed on synchronized signals during the vertical blanking retrace period, known also as the vertical interval. This allows complete replacement of one whole frame by a second whole frame resulting in a very smooth on-screen switch.

VHS (Video Home System)

Consumer videocassette record/playback tape format using 1/2" wide magnetic tape. VHS is the predominate consumer VCR format today, producing about 240 lines of horizontal video resolution compared to standard NTSC television broadcast signals of about 330 lines. The most common home VCR format in the U.S.

Popular rumor has it that Sony originally developed the VHS format concurrently with the Beta format in the early 1970s. Deciding to market the higher quality Betamax system, they sold the rights to the VHS format to JVC in order to recoup some development costs. The rest is history.

VHS-C (VHS-Compact)

A miniature, electronically identical version of the VHS tape format utilizing smaller videocassettes that may also be played on standard VHS machines with the assistance of an adapter cartridge. This format was introduced in order to compete with Sony’s 8mm camcorder format but with reduced recording time.

VIDEO BANDWIDTH

The range between the lowest and highest signal frequency of a given video signal. In general, the higher the video bandwidth, the better the quality of the picture. Video bandwidths used in studio work typically vary between 3 and 12 MHz. Consumer VCRs are generally capable of 3-5.5 MHz.

VIDEO CAMERA

A camera which contains an electronic image sensor rather than photographic film. The lens focuses an image on an electronic tube or CCD chip.

A camera has electronic circuitry which generates color and sync pulses. Most portable consumer camcorders are equipped with a full complement of audio circuitry, e.g., microphone, audio amplifier and additional audio electronics. In order to obtain better quality images, a professional camera has three tubes or a triple CCD system, one for each primary color. Most professional cameras have a genlock input, which allows the camera to be synchronized to an external source. Some cameras also include basic character generators for titling purposes.

VIDEO CD

Format that allows the viewing of MPEG-1 (also known as the ISO IEC 11172 compression standard) video on CD-ROM. It allows for more than an hour of compressed video and compressed, hi-fi quality audio. The whole point of VideoCD is cross-platform compatibility. The discs should work on suitably equipped PCs, Macs, dedicated VideoCD players, and CD-I systems. The VideoCD specification is based on the White Book standard.

VIDEO ENHANCER

A general term used to describe a device used to correct video image problems.

VIDEO GAIN

The nominal composite video signal level is 1V (volt). At this level, a fully saturated image is transmitted and boosting the signal offers no advantage. Most video equipment is designed to output the same 1V level video signal. In cases where the signal level has been reduced, such as after a long cable run, an amplifier with video gain may be employed to restore the proper level.

VIDEO MIXER

A device used to combine video signals from two or more sources. Inputs are synchronized, then mixed along with various special effects patterns and shapes. A video mixer usually generates sync signals allowing genlocking of additional video sources to the first source.

VIDEO PRINTER

A special device used to capture a single frame of video to create a hard copy print.

VIDEO PROJECTOR

A display device which projects a video or computer image onto a large screen. The classic video projector has three primary color video tubes which converge on-screen to create the full color image. Single tube projectors eliminate convergence problems but compared to three tube systems, project a relatively lower quality image.

VIDEO WALL

A large array of several monitors, placed close to one another in the shape of a video screen or “wall.” Each monitor is fed only part of the original video image by using a video-wall generating unit. This device is a digitally-based processor which converts the original analog video signal to digital, rescans, resamples and generates several individual analog video outputs for driving each array monitor separately. When viewed from a distance, the effect can be very dramatic.

VITC (Vertical Interval Time Code)

SMPTEtime code standard for recording onto videotape. By inserting the digital address for each video frame into the vertical blanking interval of the video signal, it remains invisible on-screen yet is easily retrieved, even when a helical scanning VCR is in pause mode.

WHITE BALANCE

An electronic process used in camcorders and video cameras to calibrate the picture for accurate color display in different lighting conditions. (i.e., sunlight vs. indoor incandescent) White balancing should be performed prior to any recording, typically by pointing the camera at a white object for reference. (See COLOR TEMPERATURE)

WHITE BOOK

(See VIDEO CD)

WIPE

Special effect in which two pictures from different video sources are displayed on one screen. Special effects generators provide numerous wipe patterns varying from simple horizontal and vertical wipes to multi-shaped, multi-colored arrangements.

WORD CLOCK

The timing signal that is used in a multidevice digital audio system to synchronize the sampling frequency at which the system’s component devices operate. To avoid data loss and distortion, all digital devices in a system must be slaved to a single word-clock master so that their sampling frequencies will be exactly the same.

WORD LENGTH

The number of bits per sample that a digital device (such as an A/D converter or VBR encoder) uses to convert or store data. The greater the number of bits in a digital sample, the more accurate the digitized description of the instantaneous analog signal value. Also called bit depth, bit rate or bit resolution.

Y/C (Luminance/Chrominance)

A term used to describe the separate video signal components used in S-video based videotape formats such as Hi-8 and S-VHS.

YELLOW BOOK

(See CD-ROM)

YIQ (YC bC r - Luminance/In phase/Quadrature phase)

A bandwidth optimized, matrixed, composite video signal format used by NTSC video systems employing separate luminance and two derived blue and red chroma components derived from the YUV format.

YUV (YC bC r - Luminance/Chroma R-Y/Chroma B-Y)

A bandwidth optimized, matrixed, composite video signal format employing separate luminance and two derived blue and red chroma signals. The Y (or luminance) component is derived from RGB signals by adding the Red, Green and Blue channels together in a specific formula to make a Black & White signal (the formula is 30% Red, 59% Green, and 11% Blue). R-Y is derived by taking the newly-created luminance signal and subtracting it from the raw Red signal. Since we already have a luminance signal (Y), we don’t need the Y portion of the red component so subtracting it leaves only the color difference component we call R-Y. We do the same thing with the Blue channel, subtracting Y from it leaving only the color component of blue or B-Y. We do not need to make a G-Y component because we have the others, so we can matrix them to get what’s left, which is Green.