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A B C D E F G H I J K L M N O P Q [R] S T U V W X Y Z

R

Raid.
Redundant Array of Inexpensive Drives, a method of providing non-linear editors with many gigabytes of instantly accessible data storage by teaming together a group of slower, smaller, cheaper hard drives.
RAM or random access memory.
The size of a computer's "brain", measured in bytes, describing the amount of data the computer can process and temporarily store at any moment.
Most notable characteristic:
Represents memory a program can write to using an instruction
Easily and quickly written to & read
Volatile, must be constantly supplied with power otherwise data are lost
RAM is only used for temporary storage

Why is RAM called RAM?
Each location in RAM memory is accessible in same amount of time, independent of physical location
Differs from position-dependent storage such as disk-drives, tapes, or even a book
Why?
Time required depends upon initial position before search/write operation

RAM
Permanent "mass storage" devices (hard drives, etc.) are far too slow at providing data to the CPU
disc drives have access times of milliseconds, while CPUs operate in nanoseconds
fast access to data is imperative for modern processors - thus RAM is a vital factor in the performance of a computer system

RAM
By convention, semiconductor that can be written to is classified as RAM
2 basic types of RAM: Static & Dynamic

Memory Access
main memory is accessed over the system bus
"access" refers to both reading and writing data

RAM and PC Performance
size: clearly the more RAM the better
bandwidth: transfer rates mentioned above don't tell the whole story - actual bandwidth depends on type of RAM used
latency: this is the time taken for the initial CPU request for data to be answered - again, depends largely on RAM type

Classes of RAM
dynamic RAM (DRAM): this is the type of memory used for system RAM - various subtypes exist, such as EDO.

DRAM and SDRAM - requires pre-charge.
all dynamic RAM types suffer from slow initial access times.
static RAM (SRAM): used for cache memory - faster than DRAM, but more expensive - never needs pre-charging.
cache RAM will be very frequently used - needs ultra-fast initial access to be effective.
CMOS RAM: low power RAM used for essential system data needed at boot time.

SRAM vs DRAM.
Both are volatile require power to preserve values
DRAM cell smaller, simpler than SRAM.
DRAM is more dense & therefore less expensive
DRAM circuits require refresh circuitry
Favoured for larger memory requirements
SRAM vs DRAM
SRAM is faster and therefore preferred in cache
DRAM preferred for main memory applications

Ramping.
Phenomenon that causes the f number of a long zoom lens to increase as it zooms in, creating a dimmer picture.
Raster.
The pattern of parallel horizontal scanning lines, traced by a video monitor's electron beam, making up a video image.
Raster Graphics.
Category of 2-D image formats using bitmaps.
Raw Footage.
Recordings made directly from the camera, intended to be edited into a final program later.
RC time code or RCTC.
Sony time code system for 8mm and Hi8 VCRs. Code identifies each separate frame and is recorded on a special track next to the video signal.
RCA connector.
A type of connector used on all consumer VCRs and camcorders to carry the standard composite video and audio signals.
Real Audio.
A RealMedia data type for streaming highly compressed audio over a network.
Real Time.
Something that plays, records, compresses, or decompresses as fast as it actually happened in real life.
Real Time Counter.
A display showing hours-minutes-seconds of tape that has been recorded (elapsed time), or how much tape remains.
Rear Projection Television.
Television display composed of a rear projection screen, a cathode ray tube array with red, green and blue tubes and a series of mirrors to reflect the projected images onto the screen.
Rectifier.
Component of a power supply that converts alternating current from the transformer to direct current for use in the amplifier.
Reception Mode
One of four basic configurations used by a synthesizer that determines how it will respond to incoming data.
Re-EQ.
Aspect of home THX processing that slightly attenuates high frequency signals in movie soundtracks when the feature is engaged.
Refraction.
3-D graphics feature that calculates how light will bend as it passes through clear objects.
Relation (Database)
A relation is a table with columns and rows.
Relection Map.
Flat surface with clouds, stripes, or a "snapshot" of the area, used to make fake reflections off silvery objects.
Reflex (Bass Reflex).
Type of speaker enclosure which uses a port to allow air to travel from the inside of the box to the outside of the box taking full advantage of a speaker driver's output and increasing sound pressure (sound output or volume) by 2 to 3 dB compared to a similar speaker with a sealed enclosure.
Refresh Rate.
The vertical scan rate of a video display; number of times a video display can paint an entire screen with a video signal.
Render.
Electronically perform the calculations which create the surfaces, shadows, and reflections in a three dimensional scene.
Resolution.
A measure of the ability to reproduce 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, VHS and 8mm typically achieves 240 lines of resolution, S-VHS and Hi-8 achieve 400, broadcast achieves 600.
Resonant Frequency.
Frequency at which a speaker vibrates in unison with the audio signal creating vibrations in the enclosure and driver with very little input.
Retractable Screen.
Video screen used in a front projection video display to reflect images back to the viewers that can wrap itself up and out of site.
Reverberation.
Reflection of sound waves against room boundaries and objects within the room persisting after the original sound has ceased.
RF (Radio Frequency).
A term used to describe the radio signal band of the electromagnetic spectrum (about 3 MHz to 300 GHz).
RF Modulation.
Method of placing an audio signal with a relatively low 20 to 20,000 Hz frequency on top of a much higher frequency radio frequency (in the area of 100,000,000 Hz) by varying the frequency of the radio signal according to the audio signal so that the audio signal can be sent over long distances and distributed through broadcast antennas.
RGB.
R - red, G - green and B -Blue. The basic components of a colour video signal.
RGB colour components combine to produce white.
Additive colour.
The RGB system is not ideal for choosing and editing colours. This is because it is based on the technology of computer displays rather than the needs of people.
RGB Key.
Chroma key using RGB video sources to define a sharper key effect than is possible with composite video sources.
RGB video.
Video signals traveling on three separate wires. Red parts of a COLOURed picture go on one wire; green, on the second; and blue, on the third.
RGB-to-video encoder.
Device which changes RGB video signals to composite video signals. This is a part of the scan converter and the term is sometimes used interchangeably with scan converter.
ROM
Read only memory. Permanent memory in a computer
Roll-Off.
Decrease in signal or sound pressure in decibels as a speaker or speaker driver attempts to reproduce frequencies outside of its primary frequency range (a midrange driver may roll-off at 500 Hz and its output decreases from that point); attenuation of frequencies outside a range specified in a crossover network.
Room Interaction.
Description of how the room or space affects the quality of sound produced through an audio system or live audio performance.
Run-Length Encoding (RLE).
Any repeated byte value can be encoded.

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