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Glossary of DVD Terminology "I to L"

I picture (or I frame) - In MPEG video, an intra picture that is encoded independent from other pictures (see intraframe). Transform coding (DCT, quantisation, and VLC) is used with no motion compensation, resulting in only moderate compression. I pictures provide a reference point for dependent P pictures and B pictures and allow random access into the compressed video stream.

i.Link - Trademarked Sony name for IEEE 1394.

IDE - Integrated Drive Electronics. An internal bus, or standard electronic interface between a computer and internal block storage devices. IDE was adopted as a standard by ANSI in November 1990. ANSI calls it Advanced Technology Attachment (ATA). Also see E-IDE and ATAPI.

IDTV - Improved-definition television. A television receiver that improves the apparent quality of the picture from a standard video signal by using techniques such as frame doubling, line doubling, and digital signal processing.

IEC - International Electrotechnical Commission.

IED - ID error correction. An error-detection code applied to each sector ID on a DVD disc.

IEEE 1394 - A standard for transmission of digital data between external peripherals, including consumer audio and video devices. Also known as FireWire.

IEEE - Institute of Electrical and Electronics Engineers. An electronics standards body.

IFE - In-flight entertainment.

I-MPEG - Intraframe MPEG. An unofficial variation of MPEG video encoding that uses only intraframe compression. I-MPEG is used by DV equipment.

Interframe - Something that occurs between multiple frames of video. Interframe compression takes temporal redundancy into account. Contrast with intraframe.

Interlace - A video scanning system in which alternating lines are transmitted, so that half a picture is displayed each time the scanning beam moves down the screen. An interlaced frame is made of two fields.

Interleave - To arrange data in alternating chunks so that selected parts can be extracted while other parts are skipped over, or so that each chunk carries a piece of a different data stream.

Interpolate - To increase the pixels, scan lines, or pictures when scaling an image or a video stream by averaging together adjacent pixels, lines, or frames to create additional inserted pixels or frames. This generally causes a softening of still images and a blurriness of motion images because no new information is created. Compare to filter.

Intraframe - Something that occurs within a single frame of video. Intraframe compression does not reduce temporal redundancy, but allows each frame to be independently manipulated or accessed. (See I picture.) Compare to interframe.

Inverse telecine - The reverse of 3:2 pulldown, where the frames which were duplicated to create 60-fields/second video from 24-frames/second film source are removed. MPEG-2 video encoders usually apply an inverse telecine process to convert 60-fields/second video into 24-frames/second encoded video. The encoder adds information enabling the decoder to recreate the 60-fields/second display rate.

ISO 9660 - The international standard for the file system used by CD-ROM. Allows filenames of only 8 characters plus a 3-character extension.

ISO - International Organization for Standardization.

ISRC - International Standard Recording Code.

ITU - International Telecommunication Union. 

ITU-R BT.601 - The international standard specifying the format of digital component video. Currently at version 5 (identified as 601-5).

JCIC - Joint Committee on Intersociety Coordination.

JEC - Joint Engineering Committee of EIA and NCTA.

jewel box - The plastic clamshell case that holds a CD or DVD.

Jitter - Temporal variation in a signal from an ideal reference clock. There are many kinds of jitter, including sample jitter, channel jitter, and interface jitter.

JPEG - Joint Photographic Experts Group. The international committee which created its namesake standard for compressing still images.

k byte - One thousand (103) bytes. Not to be confused with KB or kilobyte (210 bytes). Note the small “k.”

k - Kilo. An SI prefix for denominations of one thousand (103). Also used, in capital form, for 1024 bytes of computer data (see kilobyte).

karaoke - Literally “empty orchestra”. Karaoke was largely responsible for the success of laserdisc in Japan, thus supporting it elsewhere. Now a growing trend in DVD.

KB - Kilobyte.

kbps - Kilobits/second. Thousands (103) of bits per second.

key picture (or key frame)- A video picture containing the entire content of the image (intraframe encoding), rather than the difference between it and another image (interframe encoding). MPEG I pictures are key pictures. Contrast with delta picture.

kHz - Kilohertz. A unit of frequency measurement. One thousand cycles (repetitions) per second or 1000 hertz.

kilobyte - 1024 (210) bytes. See p. 12 for more information.

land - The raised area of an optical disc.

Laserdisc - A 12-inch (or 8-inch) optical disc that holds analog video (using an FM signal) and both analog and digital (PCM) audio. A precursor to DVD.

Layer - The plane of a DVD disc on which information is recorded in a pattern of microscopic pits. Each substrate of a disc can contain one or two layers. The first layer, closest to the readout surface, is layer 0; the second is layer 1.

Lead in - The physical area 1.2 mm or wider preceding the data area on a disc. The lead in contains sync sectors and control data including disc keys and other information.

Lead out - On a single-layer disc or PTP dual-layer disc, the physical area 1.0 mm or wider toward the outside of the disc following the data area. On an OTP dual-layer disc, the physical area 1.2 mm or wider at the inside of the disc following the recorded data area (which is read from the outside toward the inside on the second layer).

Legacy - A term used to describe a hybrid disc that can be played in both a DVD player and a CD player.

Letterbox - The process or form of video where black horizontal mattes are added to the top and bottom of the display area in order to create a frame in which to display video using an aspect ratio different than that of the display. The letterbox method preserves the entire video picture, as opposed to pan & scan. DVD-Video players can automatically letterbox a widescreen picture for display on a standard 4:3 TV.

Letterbox filter - Circuitry in a DVD player that reduces the vertical size of anamorphic widescreen video (combining every 4 lines into 3) and adds black mattes at the top and bottom. Also see filter.

Level - In MPEG-2, levels specify parameters such as resolution, bit rate, and frame rate. Compare to profile.

Line doubler - A video processor that doubles the number of lines in the scanning system in order to create a display with scan lines that are less visible. Some line doublers convert from interlaced to progressive scan.

Linear PCM - A coded representation of digital data that is not compressed. Linear PCM spreads values evenly across the range from highest to lowest, as opposed to nonlinear (companded) PCM which allocates more values to more important frequency ranges.

lines of horizontal resolution - Sometimes abbreviated as TVL (TV lines) or LoHR. A common but subjective measurement of the visually resolvable horizontal detail of an analog video system, measured in half-cycles per picture height. Each cycle is a pair of vertical lines, one black and one white. The measurement is usually made by viewing a test pattern to determine where the black and white lines blur into grey. The resolution of VHS video is commonly gauged at 240 lines of horizontal resolution, broadcast video at 330, Laserdisc at 425, and DVD at 500 to 540. Because the measurement is relative to picture height, the aspect ratio must be taken into account when determining the number of vertical units (roughly equivalent to pixels) that can be displayed across the width of the display. For example, an aspect ratio of 1.33 multiplied by 540 gives 720 pixels.

Lo/Ro - Left only/right only. Stereo signal (no matrixed surround information). Optional downmixing output in Dolby Digital decoders. Does not change phase, simply folds surround channels forward into Lf and Rf.

Locale - See regional code.

Logical - An artificial structure or organization of information created for convenience of access or reference, usually different from the physical structure or organization. For example, the application specifications of DVD (the way information is organized and stored) are logical formats.

Logical Unit - A physical or virtual peripheral device, such as a DVD-ROM drive.

Lossless Compression - Compression techniques that allow the original data to be recreated without loss. Contrast with “lossy compression”.

Lossy compression - Compression techniques that achieve very high compression ratios by permanently removing data while preserving as much significant information as possible. Lossy compression includes perceptual coding techniques that attempt to limit the data loss to that which is least likely to be noticed by human perception.

LPCM - See linear PCM.

Lt/Rt - Left total/right total. Four surround channels matrixed into two channels. Mandatory downmixing output in Dolby Digital decoders.

luma (Y´) - The brightness component of a colour video image (also called the grayscale, monochrome, or black-and-white component). Nonlinear luminance. The standard luma signal is computed from nonlinear RGB as Y´ = 0.299 R´ + 0.587 G´ + 0.114 B´.

luminance (Y) - Loosely, the sum of RGB tristimulus values corresponding to brightness. May refer to a linear signal or (incorrectly) a nonlinear signal.