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Glossary of DVD Terminology "S"


S/N - Signal-to-noise ratio. Also called SNR.

S/P DIF - Sony/Philips digital interface. A consumer version of the AES/EBU digital audio transmission standard. Most DVD players include S/P DIF coaxial digital audio connectors providing PCM and encoded digital audio output.

Sample - A single digital measurement of analog information. A snapshot in time of a continuous analog waveform. See sampling.

Sample Rate - The number of times a digital sample is taken, measured in samples per second, or Hertz. The more often samples are taken, the better a digital signal can represent the original analog signal. Sampling theory states that the sampling frequency must be more than twice the signal frequency in order to reproduce the signal without aliasing. DVD PCM audio allows sampling rates of 48 and 96 kHz.

Sample size - The number of bits used to store a sample. Also called resolution. In general, the more bits allocated per sample, the better the reproduction of the original analog information. Audio sample size determines the dynamic range. DVD PCM audio uses sample sizes of 16, 20, or 24 bits.

Sampling - Converting analog information into a digital representation by measuring the value of the analog signal at regular intervals, called samples, and encoding these numerical values in digital form. Sampling is often based on specified quantisation levels. Sampling may also be used to adjust for differences between different digital systems (see resampling and subsampling).

Saturation - The intensity or vividness of a colour.

Scaling - Altering the spatial resolution of a single image to increase or reduce the size; or altering the temporal resolution of an image sequence to increase or decrease the rate of display. Techniques include decimation, interpolation, motion compensation, replication, resampling, and subsampling. Most scaling methods introduce artifacts.

Scan line - A single horizontal line traced out by the scanning system of a video display unit. 525/60 (NTSC) video has 525 scan lines, about 480 of which contain actual picture. 625/50 (PAL/SECAM) video has 625 scan lines, about 576 of which contain actual picture.

Scanning velocity - The speed at which the laser pickup head travels along the spiral track of a disc.

SCMS - Serial copy management system. Used by DAT, MiniDisc, and other digital recording systems to control copying and limit the number of copies that can be made from copies.

SCSI - Small Computer Systems Interface. An electronic interface and command set for attaching and controlling internal or external peripherals, such as a DVD-ROM drive, to a computer. The command set of SCSI was extended for DVD-ROM devices by the SFF 8090 specification.

SDDI - Serial Digital Data Interface. A digital video interconnect designed for serial digital information to be carried over a standard SDI connection.

SDDS - Sony Dynamic Digital Sound. A perceptual audio-coding system developed by Sony for multichannel audio in theatres. A competitor to Dolby Digital and an optional audio track format for DVD.

SDI - See Serial Digital Interface. Also Strategic Defense Initiative, a.k.a. Star Wars, which as of 2000 was still not available on DVD other than as bootleg copies.

SDMI - Secure Digital Music Initiative. Efforts and specifications for protecting digital music.

SDTV - Standard-definition television. A term applied to traditional 4:3 television (in digital or analog form) with a resolution of about 700 x 480 (about 1/3 megapixel). Contrast with HDTV.

seamless playback - A feature of DVD-Video where a program can jump from place to place on the disc without any interruption of the video. Allows different versions of a program to be put on a single disc by sharing common parts.

SECAM - Séquential couleur avec mémoire/sequential colour with memory. A composite colour standard similar to PAL, but currently used only as a transmission standard in France and a few other countries. Video is produced using the 625/50 PAL standard and is then transcoded to SECAM by the player or transmitter.

sector - A logical or physical group of bytes recorded on the disc—the smallest addressable unit. A DVD sector contains 38,688 bits of channel data and 2048 bytes of user data.

seek time - The time it takes for the head in a drive to move to a data track.

Serial Digital Interface (SDI) - The professional digital video connection format using a 270 Mbps transfer rate. A 10-bit, scrambled, polarity-independent interface, with common scrambling for both component ITU-R 601 and composite digital video and four groups each of four channels of embedded digital audio. SDI uses standard 75-ohm BNC connectors and coax cable.

SFF 8090 - Specification number 8090 of the Small Form Factor Committee, an ad hoc group formed to promptly address disk industry needs and to develop recommendations to be passed on to standards organizations. SFF 8090 (also known as the Mt. Fuji specification), defines a command set for CD-ROM– and DVD-ROM–type devices, including implementation notes for ATAPI and SCSI.

SI - Système International (d’Unités)/International System (of Units). A complete system of standardized units and prefixes for fundamental quantities of length, time, volume, mass, and so on.

signal-to-noise ratio - The ratio of pure signal to extraneous noise, such as tape hiss or video interference. Signal-to-noise ratio is measured in decibels (dB). Analog recordings almost always have noise. Digital recordings, when properly prefiltered and not compressed, have no noise.

simple profile (SP) - A subset of the syntax of the MPEG-2 video standard designed for simple and inexpensive applications such as software. SP does not allow B pictures. See profile.

simulate - To test the function of a DVD disc in the authoring system, without actually formatting an image.

SMPTE - The Society of Motion Picture and Television Engineers. An international research and standards organization. The SMPTE time code, used for marking the position of audio or video in time, was developed by this group. (See Appendix C.)

son - The metal discs produced from mothers discs in the replication process. Fathers or sons are used in molds to stamp discs.

SP@ML - Simple profile at main level. The simplest MPEG-2 format used by DVD. Most discs use MP@ML. SP does not allow B pictures.

space - The reflective area of a writable optical disc. Equivalent to a land.

Spatial - Relating to space, usually two-dimensional. Video can be defined by its spatial characteristics (information from the horizontal plane and vertical plane) and its temporal characteristics (information at different instances in time).

Spatial resolution - The clarity of a single image or the measure of detail in an image. See resolution.

Squeezed video - See anamorphic.

Stamping - The process of replicating optical discs by injecting liquid plastic into a mold containing a stamper (father or son). Also (inaccurately) called mastering.

STP - Surface transfer process. A method of producing dual-layer DVDs that sputters the reflective (aluminium) layer onto a temporary substrate of PMMA, then transfers the metalised layer to the already-molded layer 0.

Stream - A continuous flow of data, usually digitally encoded, designed to be processed sequentially. Also called a bitstream.

subpicture - Graphic bitmap overlays used in DVD-Video to create subtitles, captions, karaoke lyrics, menu highlighting effects, and so on.

subsampling - The process of reducing spatial resolution by taking samples that cover larger areas than the original samples or of reducing temporal resolutions by taking samples that cover more time than the original samples. See chroma subsampling. Also called downsampling.

Substrate - The clear polycarbonate disc onto which data layers are stamped or deposited.

Subtitle - A textual representation of the spoken audio in a video program. Subtitles are often used with foreign languages and do not serve the same purpose as captions for the hearing impaired. See subpicture.

Surround sound - A multichannel audio system with speakers in front of and behind the listener to create a surrounding envelope of sound and to simulate directional audio sources.

SVCD - Super Video Compact Disc. MPEG-2 video on CD. Used primarily in Asia.

SVGA - A video graphics resolution of 800 x 600 pixels.

S-VHS - Super VHS (Video Home System). An enhancement of the VHS videotape standard using better recording techniques and Y/C signals. The term S-VHS is often used incorrectly to refer to s-video signals and connectors.

S-video - A video interface standard that carries separate luma and chroma signals, usually on a four-pin mini-DIN connector. Also called Y/C. The quality of s-video is significantly better than composite video since it does not require a comb filter to separate the signals, but it’s not quite as good as component video. Most high-end televisions have s-video inputs. S-video is often erroneously called S-VHS.

SXGA - A video graphics resolution of 1280 x 1024 pixels.

Sync - A video signal (or component of a video signal) containing information necessary to synchronize the picture horizontally and vertically. Also, specially formatted data on disc which helps the readout system identify location and specific data structures.

Syntax - The rules governing construction or formation of an orderly system of information. For example, the syntax of the MPEG video encoding specification defines how data and associated instructions are used by a decoder to create video pictures.

System Menu - The main menu of a DVD-Video disc, from which titles are selected. Also called the title selection menu or disc menu.