Grass Valley Dictionary

Dictionary of Technical Terms - D

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A component digital video recording format that uses data conforming to the ITU-R BT.601-2 (CCIR-601) standard. Records on 19mm magnetic tape. (Often used incorrectly to indicate component digital video.)

A composite digital video recording format that uses data conforming to SMPTE 244M. Records on 19mm magnetic tape. (Often used incorrectly to indicate composite digital video.)

A composite digital video recording format that uses data conforming to SMPTE 244M. Records on 1/2" magnetic tape.

A component digital recording format that uses data conforming to the ITU-R BT.601-2 (CCIR 601) standard. Records on 1/2'' magnetic tape.

Digital HDTV recorder using D1 tape.

Distribution amplifier.

Directory assistance.

DAC (D-A, D/A, D-to-A)

Digital-to-analog converter.

Dedicated access line.

data compression

A technique that provides for the transmission or storage, without noticeable information loss, of fewer data bits than were originally used when the data was created.

A plastic, key-shaped memory device containing an EEPROM used for off-line storage.

A measure of voltage, current, or power gain equal to 1/10 of a Bel. Given by the equations 20 log Vout/Vin, 20 log Iout/In, or 10 log Pout/Pin. See also Bel.

A measure of power relative to 1 kilowatt. 0 dBk equals 1 kW.

A measure of power relative to 1 mW. 0 dBm equals 1 mW.

A measure of voltage gain relative to 1 millivolt at 75 ohms.

This notation expresses the relationship between two program signal levels. It denotes the difference in dB between a measured program signal magnitude and a defined reference magnitude called zero relative level.

Direct broadcast satellite.

1. A United Kingdom term that shows comparison between a measured value of voltage and a reference value of 0.775 Volt, expressed under conditions in which the impedance at the point of measurement (and of the reference source) are not considered. 2. dB relative to 1 microvolt.

A measure of voltage gain relative to 1 volt.

A measure of power relative to 1 watt. 0 dBm equals 1 watt.

Direct current.

The portion of a signal that consists of direct current. The average value of a signal.

DCC-45 DS3 Digital Cross-Connect Switch

A Grass Valley DS3 digital switching system for video, audio, voice, or T1 or other data.

A type of connector that has a trapezoidal shell resembling a D.

A method of coupling one circuit to another so as to transmit the static (DC) characteristics of the signal as well as the varying (AC) characteristics. Any DC offset present on the input signal is maintained and will be present in the output. Some GVG distribution amplifiers may be set for true DC coupling. This method of coupling is the preferred mode for component analog video signals, particularly Y, R-Y, B-Y, which has negative-going energy in the R-Y and B-Y channels.

The amount that the DC component of the signal has shifted from its correct level.

DC on blanking level

The absolute DC value of the blanking signal's voltage.

The re-establishment of the DC and low-frequency components of a video signal which have been lost by AC transmission.

DC signal bounce

Overshoot of the proper DC voltage level due to multiple AC couplings in a signal path.

Discrete cosine transform. A mathematical transformation used in many compression technologies.

Digital disk recorder. See disk recorder.

Digital Data Service.

A device used to recover the component signals from a composite (encoded) source. Decoders are commonly used in monitors and receivers for recovery of RGB signals to drive a color picture tube.

A control which is assigned to perform only one function, i.e., dedicated to that function, as opposed to delegated to several functions. See also delegate.

Reducing the level of higher audio frequencies during FM reception to compensate for pre-emphasis that was applied during transmission.

The setup condition existing when a device is first powered-up.

default channel

A term used for a digital picture manipulator having one or more control panels that can be assigned (delegated) to control any of several manipulation channels. The default channel is the one to which a control panel is delegated at power-up.

A digital picture manipulation term meaning a controlled blurring of the picture.

1. To demagnetize (erase) all recorded material on a magnetic medium, such as video or audio tape. 2. To demagnetize the shadow mask in a color picture tube.

1. Loss of quality on a videotape typically due to multiple generations of copying the material. 2. To reduce the gain of an amplifier stage by applying negative feedback (feedback that is 180 degrees out of phase) to the input.

The time required for a signal to pass through a device or conductor.

An electronic component that delays a signal by a specified amount of time.

delay line response error

Frequency loss or overshoot caused by delay lines.

delay distribution amplifier

An amplifier that can introduce adjustable delay into a video signal path.

To use a single control panel or panel section to control two or more identical devices or functions. For example, a single keyer control panel may control 2 keyers, or a single control panel of a digital picture manipulator can control 2 manipulation channels. A switch selects which of the identical functions the panel is "delegated to" or assigned to control. The reverse is also possible: a single device or function can be delegated to any one of several control panels.

In effects management systems, a data manipulation technique used in memory systems to allow the settings of control panel analog controls to be different from the analog values applied to the processing software.

A circuit that demodulates or decodes the desired signal from amplitude and/or frequency modulation present on a carrier wave.

demultiplexer (demux)

A device used to separate two or more signals that were previously combined by a compatible multiplexer and are transmitted over a single channel.

See demultiplexer.

A mode in some GVG switchers and digital picture manipulators which automatically defines layering priority. This allows the layer closest to the viewer to automatically cover other layers. Can be used to create "intersecting planes" effects.

A device that converts serial digital information to parallel digital.

Video editing and production done using standard desktop computing platforms running add-on video hardware and software.

A routing switcher term describing the point to which a source signal is routed.

A device that converts one kind of energy into another. For example, one kind of detector might convert light signals to electrical signals.

A digital picture manipulation term meaning points to which the picture can be made to snap. For example, when rotating a picture, snap points usually exist in 45 degrees increments so that the operator can easily turn the picture 45 degrees, 90 degrees, etc.

Drop and insert. A point in the transmission where portions of the digital signal can be dropped out and/or inserted.

diagonal resolution

Picture detail in the diagonal direction versus horizontal and vertical resolution. Many video encoders and decoders sacrifice diagonal resolution in favor of enhanced horizontal and vertical resolution, resulting in blurring.

A program built into a device which tests the functionality of the device and reports the results. Used as an aid in troubleshooting.

Direct inward dialing.

A material that does not conduct electricity. An insulator.

differential amplifier

An input circuit that rejects voltages that are the same at both input terminals but amplifies any voltage difference between them. This causes any signal, such as common mode hum, that is present on both sides to cancel itself. This system is used in all GVG 8500 series amplifiers.

differential DC

Maximum DC voltage that can be applied between the differential inputs of an amplifier while maintaining linear operation.

differential gain

A change in subcarrier amplitude of a video signal caused by a change in luminance level of the signal. The resulting TV picture will show a change in color saturation caused by a simultaneous change in picture brightness.

differential input

See differential amplifier.

differential looping input

A video input port that allows the signal to be looped through to another input.

differential phase

A change in subcarrier phase of a video signal caused by a change in luminance level of the signal. The hue of colors in a scene change with the brightness of the scene.

Circuitry in which data carrying signals are restricted to either of two voltage levels, corresponding to logic 1 or 0. A circuit which has two stable states: high or low, on or off.

Digital Borderline(R)

See Borderline(R).

digital components

Component video signals that have been digitized.

digital effects

Special effects created using a digital picture manipulator.

digital parallel distribution amplifier

A distribution amplifier designed to amplify and fan-out parallel digital signals.

digital picture manipulator (DPM)

A GVG term for digital video effects systems which can manipulate a video picture to change its size, shape, angle, etc.

digital to analog converter

A device that converts digital signals to analog signals.

digitizing pad (digitizing tablet)

A device that translates drawings from a tablet and stylus to a digital video format.

The number of bits treated as a single entity by the system.

1. A temporary, usually major, reduction in the level of audio output to monitor speakers. 2. In digital picture manipulators, an effect where the manipulated image tapers off to black or into the background picture.

dip switch (DIP switch)

Dual in-line package switch. A pc module mounted switch package of dual in-line style, typically mounting from two to eight switches and used in such functions as mode assignment and address selection.director

The person who coordinates all aspects of a live television broadcast from within the control room.

Having an individual identity. An individual circuit component. A discrete circuit is one that uses individual transistors and other components rather than integrated circuits.

A video recording device that uses a hard disk drive or optical disk drive mechanism. Disk recorders offer nearly instantaneous access to recorded material.

The characteristic of a light-conducting medium that causes the medium to transmit light of different frequencies at different velocities. Dispersion causes the refractive index of a given medium to vary as a function of wavelength. As it relates to optical fiber, this property influences both the effective numerical aperture and the bandwidth of an optical fiber.

dispersion effect

In optical telecommunications, the pulse spreading of an optical signal that takes place when it is transmitted over optical fiber. This effect is caused by the fiber's differing material index of refraction at the various wavelengths present in the optical signal.

dissolve (mix, cross fade)

A transition where one source of video or audio is faded down as the other is faded up. See also effects dissolve.

Undesired changes in the waveform of a signal.

distribution amplifier (DA)

A device used to replicate an input signal, typically providing 6 outputs, each of which is identical to the input. May also include delay and/or cable equalization capabilities.

Typically, a random, low-level signal (oscillation) which may be added to an analog signal prior to sampling. Usually consists of white noise of one quantizing level peak-to-peak amplitude.

dither component encoding

A slight expansion of the analog signal levels so that the signal comes in contact with more quantizing levels. The results are smoother transitions. This is done by adding white noise (which is at the amplitude of one quantizing level) to the analog signal prior to sampling.

The communications path from a satellite to its ground station or from a transmitter to a studio.

Occurring after other devices in a signal path.

downstream keyer

A keyer that inserts the key after the effects system video output. This enables the key to remain on-air while the backgrounds and effects keys are changed behind it.

Digital Picture Manipulator. The GVG term for video equipment that performs digital effects such as compression and transformation.

Gradual shift or change in the output over a period of time due to change or aging of circuit components. Change is often caused by thermal instability of components.

drive pulse(s) (pulse drives, drives)

A term commonly used to describe a set of signals needed by source equipment, such as a camera. This signal set may be composed of any of the following: sync, blanking, subcarrier, horizontal drive, vertical drive, PAL pulse, and burst flag.

An electronic circuit which supplies input to another electric circuit.

drop-frame time code

SMPTE time code format that continuously counts 30 frames per second but drops 2 frames from the count every minute except for every tenth minute (drops 108 frames every hour) to maintain synchronization of time code with clock time. This is necessary because the actual frame rate of NTSC video is 29.94 frames per second rather than an even 30 frames. See non-drop frame time code.

A momentary loss or deterioration of video or audio during playback on a tape machine. Caused by momentary loss of tape contact with the playback head or by flaws in the tape.

dropout compensator

A circuit within a videotape recorder that detects dropouts and replaces them with information from the previous scan line.

A Borderline(R) mode which places a border below and on one side of a title key insert, giving a shadow effect.

Digital signal level zero, 64 kbps.

A telephone company format for transmitting information digitally. DS1 has a capacity of 24 voice circuits at a transmission speed of 1.544 megabits per second.

A telephone company format for transmitting information digitally. DS3 has a capacity of 672 voice circuits at a transmission speed of 44.736 megabits per second.

Downstream keyer.

Dual-tone multifrequency signaling.

Digital termination system.

To copy a video signal to tape. To copy one tape to another. A copy of a videotape (noun).

A manufacturer of sophisticated video graphic workstations, character generators, and still stores. Now merged with Grass Valley Group.

A computer display terminal that serves as a conversational slave to a host computer. Has a keyboard for data entry but no computing power of its own.

1. The ratio of operating time to total elapsed time of a device which operates intermittently, expressed in percent. 2. The ratio of the active time of a repetitive waveform to the full-cycle time, expressed in percent.

Digital video effects. A registered trademark of Nippon Electric Company. Refers to video equipment that performs digital effects such as compression and transformation.

Digital videotape recorder.

A 1/2" composite digital video tape format.

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