SATA Serial ATA (Advanced Technology Attachment) is designed to transfer data between disks drives (hard and optical) and computer hardware and is the successor of ATA. SATA adapters and devices communicate over a high- speed serial link originally specified in SATA I at 1.5 Gb/s, now SATA II at 3 Gb/s and SATA III at 6 Gb/s is planned. The serial interface means the connector is smaller (than ATA) and can run faster – as fast parallel data starts to suffer from skewing – serial does not. SATA does not just serialize ATA. SATA II adds native command queuing, originally a feature of SCSI, that allows handling multiple pending transactions rather than just one at a time. This allows the disk to organize the transactions for faster operation. Website: www.sata-io.org

Scaling

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Analog video signals have to be scaled prior to digitizing in an ADC so that the full amplitude of the signal makes best use of the available levels, or numbers, in the digital system. The ITU-R BT.601 digital coding standard specifies, when using 10 bits, black to be set at level 64 and white at 940. The same range of values is ascribed should RGB be used. Computer applications tend to operate with a different scaling with black set to level 0 and white at 1023. For color they usually use RGB from 0-1023. However, most still keep to 8-bit accuracy so the scale runs from 0-255. Clearly, going between computers and TV requires processing to change color space and scaling. See also: Into digits (Tutorial 1)

Schema

A collection of tables and constraints that describe the structure of a database. It provides a level of security as no one else can interpret the stored database without the schema; it is just a collection of figures. It organizes the database to allow scalability for expansion and defines efficient operation to suit a particular application.

Scrub (audio)

Replay of audio tracks at a speed and pitch corresponding to jog speed – as heard with analog audio tape ‘scrubbing’ backwards and forwards past an audio replay head. This feature, which is natural for analog fixed- head recorders, may be provided on a digital system recording on disks to help set up cues.

SCSI

The Small Computer Systems Interface is a high data rate, general-purpose parallel interface introduced in 1979 allowing up to eight devices to be connected to one bus (now 16 for Wide SCSI). Since then SCSI has hugely increased in performance but is now used mainly on high- performance workstations and RAIDs on servers while other lower cost interfaces such as USB2 and IEEE1394 connect external devices and SATA is used for hard disks. See also: Disk drives

SD, SDHC See SDTV, Secure Data

SDI

See Serial Digital Interface SDK

Software Developers Kit. Typically a software and documentation package to facilitate the development of applications to run on a given operating

system or other application. It provides another layer on top of an API, often including shortcuts and pre-built routines to make development easier and final operation faster.

SDTI Serial Digital Transport Interface (SMPTE 305M). Based on SDI, this provides realtime streaming transfers. It does not define the format of the signals carried but brings the possibility to create a number of packetized data formats for broadcast use. There are direct mappings for SDTI to carry Sony SX, HDCAM, DV-DIFF (DVCAM, DVCPRO 25/50, Digital-S) and MPEG TS.

SDTV Standard Definition Television. Digital television systems that operate using standard definition video formats, i.e. 720 x 460/60I or 720 x 567/50I. In both these may carry 4:3 or 16:9 images, and in all cases, the pixels are not square. All HDTV digital standards describe square pixels.

Secondary color correction Primary color correction, or grading, is applied to the whole image. Secondary correction is applied only to selected areas of the image – the area being defined by a pattern generator (e.g. a circle or rectangle), by curved lines or derived from the object itself using chromakey techniques – or any combination of all these. This way, for example, the color of a car in a clip could be changed from say, red to green.

Secure Data A non-volatile memory card format that is widely used in portable devices, including digital cameras, handheld computers, PDAs, GPSs. The latest cards, from 2 GB up, are SDHC (high capacity) Minimum writing speed is shown as Class 2, 4 or 6 offering 2, 4 or 6 MB/s. As development of these devices continues so the applications widen. See also: Flash memory, ING, P2, RAM Website: www.sdcard.org

SED Surface-conduction Electron-emitter Display technology is a mix of old and new, coupling Cathode Ray Tube (CRT) and LCD technologies. SED screens comprise thousands, even millions, of minute electron emitters – hence the CRT connection. The screens are thinner LCD displays and observers think SED technology is superior to current LCD and plasma monitors. Deliveries are slated to start in 2008 but may be delayed, and will concentrate on the bigger-screen end of the market – around 55-inches, initially.

Seek time (a.k.a. Positioning time)

The time taken for the read/write heads of a disk drive to be positioned over a required track. Average seek time is the time to reach any track from the center track. Maximum seek/ positioning time is the time to reach any track from any track. A high performance modern hard disk offers around 4 ms average seek time and typically twice that for the maximum. Minimum seek time to adjacent tracks is as low as 0.2 ms for read, 0.4 ms for write. These times are critical to disk performance, especially when operating with the very high data rates associated with video and digital film. See: Disk drives, FrameMagic

Serial Digital Interface (SDI) Serial Digital Interface carries uncompressed digital video, multiple tracks of embedded audio and ancillary data over the ubiquitous 75-ohm coax cable,

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GLOSSARY OF TERMS