Audio/Video Glossary

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.

CAPACITOR MICROPHONE

(See CONDENSER MICROPHONE)

CARDIOID MICROPHONE

Microphone pickup pattern type characterized by a heart-shaped pickup pattern. This type favors sound arriving from the front of the microphone.

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 Has largely superseded CLV.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 9660 logical 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. CIRC applies two levels of error correction, known as C1 and C2. The C1 level is meant to correct small, random errors. The C2 level corrects larger errors and burst errors. The errors E11, E21, E31, E12, E22, and E32 derive from these two levels of error correction.

CIRC employs two principles to detect and correct errors: redundancy and interleaving. CIRC uses about 25 percent data redundancy. The data is laid out in a way that will allow errors to be corrected, even though the data is not 100% redundant; it uses a parity-checking algorithm to reproduce data that is unreadable. In addition, the data on a disc is interleaved. Interleaving means that the data is distributed over a relatively large physical-disc area. The data bytes are interleaved during recording and de-interleaved during playback. One data block (frame) of 24 data bytes is distributed over 109 blocks. To destroy one byte, you would have to destroy these other bytes. With scratches, dust, fingerprints, and even holes in the disc, there is usually enough data left to reconstruct any that has been damaged or rendered unreadable.

Level 1 E Errors, E11, E21, and E31, occur at the first stage of error correction. An E11 error means that one bad symbol (byte) was corrected at the C1 stage. An E21 error means two bad bytes, and E31 signifies that three bad bytes were detected. E31 errors are uncorrectable at the first stage and must be passed on to the second stage of correction. The first number is always the number of errors, and the second number is always the decoder level.

Level 2 E Errors are handled in the second C2 stage. An E12 error means one bad symbol (byte) was corrected at the C2 stage. Likewise, an E22 means two bad symbols and E32, three or more bad symbols. For CD-ROM, any E32 errors are unacceptable. First, an uncorrectable error in computer data can have a devastating effect. Second, the mastering equipment used by replication facilities will abort when an uncorrectable error on input media occurs, and the process must be restarted, which can result in additional costs and delays in your replication run. Some, but not all, CD-ROM drives use error correction and detection to such an extent that even an E32 error can be recovered, but there is no guarantee that even the best CD-ROM drive will be able to recover every E32 error. E32s on a pressed Audio or ROM disc, or a CD-R, indicate that the user is dangerously close to losing stored data with the next scratch or fingerprint. (See CD-DA)

CLAPSLATE

A slateboard used in synchronizing sound and picture during filming and editing. The slate carries information such as scene and take number, production title, shot location (e.g., indoors or outdoors) and time code. A pair of hinged boards on top of the slate, called clapsticks, slap together, producing the sound that is used to synchronize the sound to picture.

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.

Component video comes in several flavers both analog and digital: RGB (red, green, blue), YUV (luminance, sync, and red/blue) and Y/C (luminance and chrominance), available to consumers via the S-video jacks found on some equipment (S-VHS and Hi-8). You can display and use S-video images by using a 4-pin S-video connector cable.

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.

CONDENSER MICROPHONE

A microphone that converts (transduces) acoustic energy into electrical energy using electrostatic principles. These mics are not as physically durable as dynamic microphones. Condenser mics tend to exhibit high sensitivity with good pickup characteristics and their extended frequency response generally provides a crisp, accurate reproduction of the sound source. They also have excellent transient response for accurately reproducing sudden sonic impulses, such as those produced by the human voice, piano or percussive instruments. Also called capacitor microphones.

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:
1. Luminance/sync crosstalk
2. 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.

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