RAM (Random-Access Memory)
Generally refers to solid-state chips. In the case of DVD-RAM, the term was borrowed to indicate ability to read and write at any point on the disc.

RAMbo drive
A DVD-RAM drive capable of reading and writing CD-R and CD-RW media. (A play on the word "combo.")

random access
The ability to jump to a point on a storage medium.

raster
The pattern of parallel horizontal scan lines that makes up a video picture.

read-modify-write
An operation used in writing to DVD-RAM discs. Because data can be written by the host computer in blocks as small as 2 KB, but the DVD format uses ECC blocks of 32 KB, an entire ECC block is read from the data buffer or disc, modified to include the new data and new ECC data, then written back to the data buffer and disc.

Red Book
The document first published in 1982 that specifies the original compact disc digital audio format developed by Philips and Sony.

Reed-Solomon
An error-correction encoding system that cycles data multiple times through a mathematical transformation in order to increase the effectiveness of the error correction, especially for burst errors (errors concentrated closely together, as from a scratch or physical defect). DVD uses rows and columns of Reed-Solomon encoding in a two-dimensional lattice, called Reed-Solomon product code (RS-PC).

reference picture (or reference frame)
An encoded frame that is used as a reference point from which to build dependent frames. In MPEG-2, I pictures and P pictures are used as references.

reference player
A DVD player that defines the ideal behavior as specified by the DVD-Video standard.

regional code
A code identifying one of the world regions for restricting DVD-Video playback.

regional management
A mandatory feature of DVD-Video to restrict the playback of a disc to a specific geographical region. Each player and DVD-ROM drive includes a single regional code, and each disc side can specify in which regions it is allowed to be played. Regional coding is optional-a disc without regional codes will play in all players in all regions.

replication
1) The reproduction of media such as optical discs by stamping (contrast with duplication); 2) a process used to increase the size of an image by repeating pixels (to increase the horizontal size) and/or lines (to increase the vertical size) or to increase the display rate of a video stream by repeating frames. For example, a 360x240 pixel image can be displayed at 720x480 size by duplicating each pixel on each line and then duplicating each line. In this case the resulting image contains blocks of four identical pixels. Obviously, image replication can cause blockiness. A 24-fps video signal can be displayed at 72 fps by repeating each frame three times. Frame replication can cause jerkiness of motion. Contrast with decimation. Also see interpolate.

resampling
The process of converting between different spatial resolutions or different temporal resolutions. This may be based on simple sampling of the source information at higher or lower resolution or may include interpolation to correct for differences in pixel aspect ratios or to adjust for differences in display rates.

Reserved bytes
6 bytes in the header of each DVD sector reserved for future use.

reserved (reserved field)
The field indicated by the term "reserved" may be used in future revisions of the DVD specifications. Unless otherwise indicated all reserved bits shall be set to zero.

resolution
1) A measurement of relative detail of a digital display, typically given in pixels of width and height; 2) the ability of an imaging system to make clearly distinguishable or resolvable the details of an image. This includes spatial resolution (the clarity of a single image), temporal resolution (the clarity of a moving image or moving object), and perceived resolution (the apparent resolution of a display from the observer's point of view). Analog video is often measured as a number of lines of horizontal resolution over the number of scan lines. Digital video is typically measured as a number of horizontal pixels by vertical pixels. Film is typically measured as a number of line pairs per millimeter; 3) the relative detail of any signal, such as an audio or video signal. Also see lines of horizontal resolution.

RGB
Video information in the form of red, green, and blue tristimulus values. The combination of three values representing the intensity of each of the three colors can represent the entire range of visible light.

RLE
See Run length coding.

RMA
Region Management information. In DVD-Video, an 8-bit (1 byte) value stored in the CPR_MAI that indicates in which regions of the world a disc is permitted to play. See regional management.

ROM
Read-only memory.

Root Menu
Menu used to access other interactive menus in the Video Tile Set Manager domain, or to make a selection which is not defined by other system menus such as Angle Menu, Audio, Menu, PTT Menu and Sub-picture Menu.

rpm
Revolutions per minute. A measure of rotational speed.

RS
See Reed-Solomon.

RS-CIRC
See CIRC.

RSDL
Reverse-spiral dual-layer. See Opposite Track Path (OTP).

RS-PC
Reed-Solomon Product Code. An error-correction encoding system used by DVD employing rows and columns of Reed-Solomon encoding to increase error-correction effectiveness.

Run-length coding (RLE)
Lossless compression method that exploits contiguous samples with same value.

R-Y, B-Y
The general term for color-difference video signals carrying red and blue color information, where the brightness (Y) has been subtracted from the red and blue RGB signals to create R-Y and B-Y color-difference signals.