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Dictionary of Technical Terms - R

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An equipment rack. In video, a standard equipment rack is 19 inches (48.26 cm) wide at the front. Most video equipment is designed to fit into a standard rack.

Unit of measure of vertical space in an equipment rack. One rack unit is equal to 1.75 inches (4.45 cm). The height of a GVG electronics frame is typically specified in rack units.

RAM (random access memory)

A temporary, volatile memory into which data can be written or from which data can be read by specifying an address.

A video test signal that graduates from low luminance to high luminance used to measure luminance linearity.

1. A predetermined pattern of scanning the screen of a CRT. 2. The illuminated area produced by scanning lines on a CRT when no video is present.

rate conversion

1. The process of converting from one digital sample rate to another. The digital sample rate for the component digital video format is 13.5 MHz. For the composite digital video format it is either 14.3 MHz for NTSC or 17.7 MHz for PAL. 2. Often used incorrectly to indicate both resampling of digital rates and encoding/decoding.

Regional Bell operating company.

read before write

A feature of some videotape recorders that plays back the video or audio signal off of tape before it reaches the record heads, sends the signal to an external device for modification, and then applies the modified signal to the record heads so that it can be re-recorded onto the tape in its original position.

Computation or processing done in the present to control physical events occurring in the present. For example, when a digital effects system operator moves a joystick and the video images on the monitor appear to move simultaneously, the computations required to make the images move are said to have occurred in real time.

real-time multilayering

The ability to assemble several layers of video in real time. Some video switchers, such as the Kadenza system, allow several video layers to be viewed simultaneously in real time before a recording is made.

rear connector channel

To restart a computer. See boot up.

The process of clocking digital data with a regenerated clock.

recursion, recursive effects

Means to write again. A digital picture manipulation in which images are repeated on screen to create such effects as image trails, mosaics, and montages.

In digital picture manipulators, the part of the digital effects processor used to build recursive effects such as star trails, mosaics, montage effects, strobes, etc.

A test signal in which the picture is filled with 75% or 100% red.

redundant power supply

Backup power supply which takes over immediately if the primary power supply fails.

re-entry (reentry)

In video switchers, the ability to select the output of a mix/effects level as the input to another mix/effects level or to the program/preset mixer.

See reference video signal.

reference synchronizing generator

A sync pulse generator used as the main source of synchronizing signals. Other sync generators may be slaved (derive their signals) from the reference generator.

reference video signal

A composite video signal to which other signals are compared or locked for timing purposes.

refractive index

Relating to fiber optics, the ratio of the velocity of light in a vacuum to its velocity in a material, such as an optical fiber.

In video, to restore a pulse to its correct shape and level.

A memory storage location in an effects memory system.

relative humidity

Ratio of the quantity of water vapor in the atmosphere to the quantity which would cause saturation at the existing temperature.

An electromechanical device having electrical contacts that open or close when current is applied to the activating mechanism of the device.

A video device that, in the event of a power failure, routes the video signal around the equipment that has lost power. GVG's 3240-206 Relay Bypass Module is an example.

relegendable buttons

Control buttons that are designed to allow the user to change their designations (the name on the button).

Electronic signal transmitted from a distant location.

remote truck, remote van

A mobile truck or van that houses a broadcast switching and control center for broadcasting news or sports.

1. A receiver/transmitter that receives a signal from another transmitter and relays (retransmits) it to another receiver or a receiver/transmitter. 2. In fiber optics, a device that converts a received optical signal to its electrical equivalent, reconstructs the source signal format, amplifies and reconverts it to an optical output signal. The purpose is to restore the light amplitude, compensating for normal loss in fiber.

To restore a device to its default or original state. To restore a counter or logic device to a known state, often a zero output.

A load in which the voltage is in phase with the current.

A component made of a material (such as carbon) that has a specified resistance or opposition to the flow of electrical current.

Detail. In digital video and audio, the number of bits (four, eight, ten, etc.) determines the resolution of the digital signal. Four bits yields a resolution of 1 in 16. Eight bits yields a resolution of 1 in 256. Ten bits yields a resolution of 1 in 102 4. Eight bits is the minimum acceptable for broadcast television.

See frequency response.

A measure of the sensitivity of a photosensor. The ratio of the output current or voltage to the input flux in watts or lumens. When responsivity is indicated at a particular wavelength (in amperes/watt), it denotes the spectral response of the device.

See DC restoration.

Adjustment of a local synchronizing generator that has been locked to a distant source. This permits the local facility to use the distant source in real-time production through a video switcher.

The return of the electron beam in a CRT to the starting point after scanning. During retrace, the beam is typically turned off. All of the sync information is placed in this "invisible" portion of the video signal. May refer to retrace after each horizontal line or after each vertical scan (field).

A measure of the accuracy of the impedance match between a signal source (such as a cable) and its terminating load. An unequal impedance match causes some of the power from the source to be reflected back to the source, resulting in signal distortion. The ratio of the signal voltage at the load to that voltage reflected back to the source is defined as the return loss. This ratio is generally expressed in decibels (dB).

Radio frequency.

Radio frequency interference. Spurious electromagnetic energy that interferes with electronic equipment or broadcast signals.

A coaxial cable type often used in television.

RGB (red, green,þ& blue; GBR)

The three primary colors used in video processing, often referring to the three unencoded outputs of a color camera or VTR.

Regional holding company.

Flat cable with individually-insulated multiple parallel conductors.

An oscillatory transient on a signal occurring as a result of band-width restrictions and/or phase distortions. A type of ringing causes ghosting in the video picture.

A feature of video editing systems that automatically adjusts the in and out edit points of all affected events in a show when an event is deleted, added or changed in length.

Time required for a pulse edge to rise from 10% to 90% of the final value.

Record mark. This is a mark in the edit decision list indicating that the edit has already been recorded.

Root mean square. A measure of effective (as opposed to peak) voltage of an AC waveform. For a sine wave it is .707 times the peak voltage. For any periodic waveform, it is the square root of the average of the squares of the values through one cycle.

1. To start playing a videotape. 2. To scroll credits or graphics vertically up or down the screen. Also called credit roll.

rolloff (slope)

A gradual decrease in signal voltage, usually associated with an increase in frequency.

Read only memory. A memory device that is programmed only once with a permanent program or data that cannot be erased.

In digital picture manipulators, to turn an image on one of its axes. In video switchers, to turn a wipe pattern around a point on the picture surface.

In editing, a preliminary version of the edit decision list.

router, routing switcher

An electronic device that routes a user-supplied signal (audio, video, etc.) from any input to any user-selected output. Inputs are called sources. Outputs are called destinations.

Rural service area.

A SMPTE parallel component digital video standard. See SMPTE 125M

A document prepared by the Electronics Industries Association describing recommended practices for NTSC color television signals in the United States.

A standard, single-ended (unbalanced) interconnection scheme for serial data communications.

In telecommunications, a transmission specification for NTSC video and audio.

A standard, balanced interconnection scheme for serial data communications.

A graphic element of a video editing application that shows time or timecode along a horizontal axis. Similar to the ruler in word processing applications except the units are times.

ruler-flat frequency response

The response of a system to a constant-amplitude function that varies in frequency is flat if the response remains within specified limits of amplitude, usually specified in decibels from a reference quantity.

In GVG video equipment, this mode permits an effect to be recalled and replayed, but not created or modified.

A designator used to name one of the color signals (red minus luminance) of a color difference video signal. The formula for deriving R-Y from the red, green, and blue component video signals is .70R - .59G - .11B.

Return to zero. A data stream in which the logic level for a data 1 is a 1 during the time the data clock is high but returns to 0 during the time the data clock is low. For a data 0 the logic level is 0 for both high and low states of the data clock.

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