Digital video glossary

The most daunting element of any new technology is its jargon. If the alphabet soup that is digital video argot baffles you, check out this glossary of DV-related terms.

		B C D E F G M O R S V
8mm/VHS:		Analogue formats that store colour information in composite format with 240 to 250 lines of resolution and a signal-to-noise ratio, or measure of inherent noise in the signal, of around 43 to 45 decibels. In contrast, digital video stores image information in the higher-quality component format, with 500 lines of resolution and a much higher signal-to-noise ratio of 60 decibels.
Bit rate:		A measure of the file size or capacity associated with a particular unit of time. For example, a file compressed to 28.8Kbps contains 28.8 kilobits of data for each second. Similarly, a 28.8Kbps modem can transfer a maximum of 28.8 kilobits of data per second.
CCD		Charge-coupled device; the chip onboard a DV camera that converts the brightness and colour information from the lens into digital data.
Digital8		A format that uses Hi8 or 8mm tapes to store digital video.
Digital video		Video stored in a digital file.
Digital zoom		The process by which a camera takes a small portion of the original captured frame and zooms it digitally with interpolation -- similar to zooming in on an image in an image editor. Generally causes image degradation above 2X to 3X zoom ratios.
Digitise		To convert analogue video to digital video.
DV		A digital standard created by a consortium of camcorder vendors, which uses Motion JPEG video at a 720 by 480 resolution at 29.97 frames per second, stored at a bit rate of 25Mbps.
DVD		Originally referred to as Digital Video Discs, these high-capacity optical discs, now called Digital Versatile Discs, are used to store everything from massive computer applications to full-length movies. Although similar in physical size and appearance to a CD or a CD-ROM, DVD is a huge leap from its predecessor's 650MB of storage. A standard single-layer, single-sided DVD can store a whopping 4.7GB of data. But it doesn't stop there: DVD also has a two-layer standard that boosts the single-sided capacity to 8.5GB. DVDs also can be double-sided, ramping up the maximum storage on a single disc to 17GB. Unfortunately, to use DVDs, you must buy a new disk drive for your PC, but that new hardware also will read older CD-ROMs and audio CDs.
DVD authoring		The process of preparing and copying audio, video, still images and navigational menus to a final DVD image, which can be burned to DVD-R or copied to DLT tape for reproduction.
DVD-R		A write-once, recordable format. DVD-R drives can write DVD-R discs, which can be written only once, as opposed to a DVD-RW drive, which can write and rewrite to RW media.
DVD-RAM		A two-sided, rewritable format introduced by Hitachi, Toshiba and several other manufacturers. DVD+RAM discs cannot be read by DVD set-top players, nor by many computer DVD drives.
DVD-RW		DVD-RW (recordable/rewritable) drives can write both DVD-R discs, which can play back on virtually all DVD set-top players and computer drives, and DVD-RW rewritable discs, which can generally be read only by DVD-RW drives.
DVD+RW		A 4.7GB, rewritable format pioneered by the DVD+RW Alliance, which includes Hewlett-Packard, Mitsubishi Chemical/Verbatim, Philips, Ricoh and Sony. DVD+RW discs cannot be read by DVD set-top players, nor by many computer DVD drives.
Electronic image stabilisation		Image stabilisation compensates for slight movements of the hand during shooting. Electronic image stabilisation works by capturing an image larger than the ultimate target frame and shifting the actual pixels stored on tape to account for camera motion. Generally considered inferior to optical image stabilisation.
FireWire		Apple brand name for the IEEE 1394 standard (also known as i.LINK), which enables the transfer of digital video between DV camcorder and computer at 400Mbps.
Generation loss		The quality loss associated with copying an analogue video from tape to tape, similar to photocopying a photocopy. Does not occur with digital video formats.
MPEG		The Moving Pictures Experts Group, which formulates standards for video encoding, such as MPEG-2 for DVD and MPEG-4 for streaming video.
Optical image stabilisation		Image stabilisation compensates for slight movements of the hand during shooting. Optical image stabilisation works by using gyros and prisms within the camera to compensate for camera motion. Generally considered superior to digital image stabilisation.
Optical zoom		Also called telephoto or true zoom, optical zoom is produced by the optical lens itself, as with a traditional film-based camera, producing enlargement without degradation.
Resolution		The size of a video frame, measured in pixels. Digital video has a resolution of 720 by 480, which means that every complete frame (two fields combined) is 720 pixels wide and 480 pixels high.
Streaming		A low-bit-rate encoding format intended for use over networks and the Internet. Streaming files match the encoded bit rate to the connection speed of the user, so the remote viewer can play audio or video with minimal stoppage without first downloading the entire video file.
SuperVideoCD		Another CD-ROM-based format that uses MPEG-2 video instead of MPEG-1. Both VideoCD and SuperVideoCD were popular in the Far East, but never achieved momentum in the United States or Europe.
S-VHS/Hi8		Analogue formats that store colour information in S-Video format with 400 to 420 lines of resolution and a signal-to-noise ratio of around 45 to 46 decibels. In contrast, digital video stores colour information in a higher-quality component format, with 500 lines of resolution and a much higher signal-to-noise ratio of 60 decibels.
VideoCD		A predecessor to DVD, VideoCD is a compact disc (CD-ROM) format that can use MPEG-1 video for playback on computer CD drives or dedicated VideoCD players.