D1-D9	Various digital videotape formats ratified by international agreement. D1 records uncompressed 8 bit component video (Sony, Bosch). D2 records uncompressed composite video (Sony, Ampex). D3 records uncompressed composite video (Panasonic). D5 records uncompressed 10 bit component video (Panasonic). D6 records High Definition (Phillips). D7 is DVCPro, records compressed 8 bit component video (Panasonic). D9 is Digital-S, records compressed 10 bit component video (JVC).
DAT	Digital Audio Tape. Small format audio recording medium. Can record in 16 bit at 48kHz sampling rate.
dark chip	Latest generation of the DMD. Central component of Texas Instruments' 'DLP Cinema'. Features higher resolution and increased contrast ratios.
data rate	Amount of data that a storage device consistently saves or plays back per second, or the amount of data per second in a video sequence.
dB	Decibel. The standard unit used to express gain or loss of power. It is the logarithmic ratio of output power divided by input power. A reduction of 3 dB in a signal is an attenuation to half of the original power.
DCT	Discrete Cosine Transform. A technique for representing waveform data as a weighted sum of cosine waves. DCT is commonly used for data compression, eg in M-JPEG. The use of DCT is non-lossy. Data compression technologies that rely on DCT, however, may be lossy if they approximate some of the coefficients to reduce the amount of data.
digital	A signal in which information is transmitted as a binary code, ie as a series of 1s and 0s. Unlike an analogue signal, which can be represented as a continuously varying wave, a digital signal is a ultra high density stream of discrete blocks. See 'bit'.
Digital 8	Consumer digital video format.
DigiBeta	Digital Betacam. A 10 bit professional digital video format employing 2:1 compression.
Digital-S	10 bit digital video at 3.3:1 compression and a data rate of 50Mb/s.
DigitalScope	Electronic creation of an 'anamorphic' 35mm negative. HD master is letterboxed then squashed horizontally prior to film transfer. Results in widescreen image without the need for anamorphic lenses.
D-ILA	Direct-drive Image Light Amplifier. Digital development of JVC analogue projector technology based on transmissive LCD.
DLP	Digital Light Processing. The basis for the only commercially available digital cinema projectors. Developed by Texas Instruments and Digital Projection. Combines the Digital Micromirror Device with sophisticated image processing. See 'DMD'
DMD	Digital Micromirror Device. Core technology of DLP Cinema projectors. An array of 500,000+ individually switchable reflective surfaces mounted on a square inch of silicon. Each can be oriented to reflect more or less light replicating the behaviour of the pixels in digital video.
drop frame timecode	NTSC time code format that counts 30 frames per second but drops 2 frames from the count every minute but for each tenth minute (108 frames dropped every hour) to maintain synchronization of time code with clock time. This is necessary because the actual frame rate of NTSC video is 29.94 frames per second rather than an even 30 frames.
dropout	A momentary loss or deterioration of video or audio during playback. Caused by loss of tape contact with the playback head or by flaws in the tape.
dual-stream	A video editing system capable of mixing two streams of video in real time to avoid rendering.
DV	A generic term for 5:1 compression digital video formats - DVCam, DVCPro, miniDV. Records 525 lines in PAL. 25Mbp/s data rate.
DVCam	Sony professional DV format with 4:2:0 sampling (PAL). Evaporated metal 1/4 inch tape allows higher data density and slower tape speed.
DVCPRO	Panasonic professional DV format with 4:1:1 sampling (PAL). Metal particle 1/4 inch tape requires lower data density and higher tape speed.
DVCPro50	Panasonic rival to Sony Digital Betacam. Uses MPEG-2 compression. Also known as DV50.
EDL	Edit Decision List. A log file that lists the in and out points and source tapes of all video clips (events) in an edit.
field	Two fields (odd and even) comprise one frame of interlaced video. The odd and even sets are alternately recorded, each with 312.5 lines (PAL).
FireWire	Apple registered tradename for the IEEE1394 interface.
fps	Frames per second.
frame	One complete picture which, in PAL video, consists of 625 horizontal scan lines. Each frame is composed of two interlaced fields.
free-run timecode	Timecode generated from a continuous internal clock, ie clock run is not triggered on/off by recording start/stop. Results in discontinuous timecode on tape. See 'record-run timecode'.
gain	Electronic enhancement of the image. Used to brighten low-light scenes. Increasing gain increases picture noise.
gamma	An exponential function modelling the non-linearity of the light output of a CRT with respect to voltage input. Can be manipulated to vary the brightness of an image.
genlock	A device enabling synchronisation of two signals.
generation	Each pass (or recording) of a signal. Generation loss results in artefacting and image deterioration. For digital signals with minimal compression generation loss is effectively eliminated, allowing tapes to be copied many times.
GLV	Grating Light Valve. Digital Projection technology using a laser as the light source.
grading	Adjustment of picture colour, brightness, contrast. Used to fine tune (or completely change) the image. Also known as 'colour correction'.
HDTV	High Definition Television. Not standardised to a particular image resolution. HDTV cameras are not to be confused with those designed for digital cinema.
HD24P	High Definition video format devised by Sony/CineAlta. Defined as a resolution of 1920x1080 pixels, recorded at 24fps in progressive scan mode. Can be converted to a variety of established video formats.
Hi-8	Consumer analogue tape format based on Video8.
IEEE1394	A serial digital protocol for device linking. In video, transmits both DV data and device control instructions.
i-link	Sony version of firewire.
interlaced video	Video, typical of all established systems, with each frame composed of two sets of alternately scanned lines (odd and even fields).
interpolation	A computer-based method of creating values (lines or pixels) between extant known values of a video or audio signal. Can be used to smooth out an image or sound, or simulate an increase/decrease in resolution.
IRE units	A linear scale measuring the relative amplitude of a component of a television signal with a zero reference at the blanking (no signal) level. True black (zero volts) to peak white is 100IRE units.
LANC	An editing protocol enabling two-way communication between recorder and computer.
LCD	Liquid Crystal Display. A fluid crystalline material held between glass. An applied electric charge causes specific areas to turn dark. Combined with dyes or filters a colour display is possible. Used in analogue and, potentially, digital video projectors.
letterboxing	A technique for showing, without distortion, a wide aspect ratio picture on a standard aspect ratio screen. The result is black bars at the top and bottom of the screen.
line doubling	A process that doubles the number of scan lines in a video signal during conversion to a higher resolution format. See Interpolation.
LTC	Linear or Longitudinal timecode. Data is recorded on a tape edge track.
luminance	The part of a video signal that contains the brightness information of an image. The only signal required for black and white. For colour, it is obtained from a weighted sum of the R, G and B components.
Mb/s	Megabits per second - a data transfer rate. Also Mbps.
MB/s	Megabytes per second - a data transfer rate. Also MBps.
ME tape	Metal Evaporated tape. High density tape format. Used for DVCam.
miniDV	The smallest digital video tape format. 25Mbps data rate.
M-JPEG	Motion JPEG, an image compression format based on DCT (Discreet Cosine Transform). M-JPEG compresses each video frame separately to create a sequence of JPEGs (still images). Unlike DV, M-JPEG generates a variable data rate and can't be recorded directly to videotape.
mosquito noise	Artefacting caused by defects in the DCT algorithm.
MP tape	Metal Particle tape. Older, lower density tape format than ME. Used for DVCPRO.
MPEG	A variable rate lossy compression routine for video and audio data. Differs from M-JPEG in utilising only critical frames and identifying redundant areas between frames.
non-drop frame timecode	NTSC timecode format that counts a full 30 frames per second. Because NTSC video does not operate at exactly 30 frames per second, non-drop frame timecode will count 108 more frames in one hour than actually occur in the video sequence. The result is incorrect synchronization of time code with clock time.
non-interlaced video	See 'progressive scan'.
NLE	Non-Linear Editing. The ability to edit and re-edit video by entering a sequence at any point. Facilitated by the non-linearity of hard disk recording on computer.
NTSC	National Television Systems Committee (USA). Video standard for North America, parts of South America, and Japan. Comprised of 525 lines at 60Hz.
off-line edit	First stage edit frequently using reduced quality copies of master material. An EDL is created which allows 'conform' of masters in the on-line edit.
on-line edit	Final stage edit using EDL from off-line edit and master material.
overscan	On a monitor, revealing only that part of a video image within 'safety' on a standard television.