D Terms

D to A (Digital to Analog): A conversion process that takes a digital signal and converts it into an analog signal usually by a process of filtering.

D/A: Abbreviation for Digital-to-Analog converter.

D1: A SMPTE video tape format standard for recording digital component signals on tape, based on the international ITU (CCIR) standard. It is sometimes used interchangebly to mean the component SDI standard (Serial Digital Interface). However, this is incorrect. It is a video tape standard.
Component Digital Video employs the component Y, R-Y, B-Y recording system in a digital recording process. Some Sony machines that support this format are DVR-1000, DVPC-1000, DVR-2000, DVR-2100.

D2: A SMPTE video tape format standard for recording digital composite signals on tape.

Composite Digital Video employs the composite (full bandwidth, direct color) recording system in a digital recording process.

Sony machines that support this format are DVR-2, DVR-10, DVR-18, DVR-20, DVR-28.

D-picture: DC-coded picture. A picture that is coded using only information from itself (intrafield or intraframe coded). Of the DCT coeffcients in the coded representation, only the dc coefficients are present. Proposed use is to enable viewable pictures in fast forward and rewind.

DAC (Digital-to-Analog Converter): Also called a D to A converter. A device that converts digital signals to analog signals that can be handled by traditional analog circuitsÐi.e. VCRs, audio amplifiers, video monitors, etc. In a digital video system, the DAC converts digital video to an analog video signal. In a CD drive, it converts the digital information to analog audio that can be used by amplifiers and speakers.

Data Broadcasting: Use of the NTSC TV signal to deliver high volume digital data. Currently, Broadcasters use VBI to carry low volume data.

Data Communications: (1) The movement of encoded information by means he speed of a data-transfer process, normally expressed in bits per second or bytes per second. The data rate of CD-ROM is 150,000 bytes per second, while the data rate for a typical Magnetic Hard Disk is 1.5 MB per second.

dB: Decibel. A logarithmic scale used for notation of large numbers or extreme ratios or comparisons with the convenience of smaller numbers. Each increase of 3dB equates to a doubling of an electronic signal.

DBS: Direct Broadcast Satellite, also called direct to home in Europe, the provision of broadcasting from a satellite directly to a comsumer user, usually using a small aperture antenna.

DC (Direct Current): An electrical current which, unlike AC, maintains a steady flow and does not reverse directions. DC cannot be measured in cycles per seconds or Hz. DC current is either generated from a battery or derived from alternating current through a special circuit. Many electronic circuits require DC current in their operation.

DCE: Data Circuit Terminating Equipment. Telecommunications term: equipment at an access point of a network. A modem is a DCE while a personal computer is a DTE (Data Terminal Equipment).

Decision Point: The point in an interactive program where the user must make a choice, such as selecting an item from a menu or choosing an answer to a question. Choices made at the decision point move the viewer into one of several potential program branches. (See Branches).

DCS: Digital Crossconnect System. Telecommunication's synchronous, fixed rate signal routing device.

DCT: Discreet Cosine Transform. Mathematical algorithm which is used to generate frequency representations of a block of video pixels. The DCT is an invertible, discreet orthogonel transformation between time anfrequency domain. It can be either forward discreet cosine transform (FDCT), or the inverse discreet cosine transform (IDCT).

DCT Coefficient: The amplitude of a specific cosine basis function

De-emphasis: Filtering applied to and audio signal after storage or transmission to undo a linear distortion due to emphasis.

Decoded Stream: The decoded reconstruction of a compressed bitstream.

Decoder: Descrambler. The device used to restore an encoded (scrambled) signal to its original form.

Decryptor: A descrambler or decoder designed to restore a scrambled and encrypted signal to its original form.

Dedicated Network: Videoconferencing term: a network line which is leased full time, providing direct connection between sites.

Definition: Synonymous with sharpness, detail, quality, or resolution of a video signal.

Delivery System: The computer, video players, and other media equipment actually used to deliver a multimedia program. A delivery system may consist of as little as a videodisc player with an on-board microprocessor, a monitor, and a keypad or may extend to an external computer, two or more monitors, and a variety of peripheral devices.

Demodulation: The description of a signal stripped of its modulated carrier frequency and converted into a standard video signal after broadcast transmission and prior to display. Signals transmitted by antennae, microwave, fiber optics, or recorded by an analog video recorder must be modulated to a special carrier frequency prior to transmission: once transmission is complete, the original signal must be demodulated for display..

Depth Key: A DVS-2000C option that permits keys in the third dimension, using the "Z" axis or depth axis in XYZ coordinate space. Depth information can be derived from a full-screen video source, a key source, the main mask, a subsidiary mask, or by using "Z-data" from the DME-3000 or DME-7000. The feature allows you to perform visually complex keys without the need for complex masks, timelines, and repeated priority switching.

Depth of Field: The distance between the first object in focus and the last object in focus within a scene as viewed by a particular lens. Depth of field is affected by choice of lens focal length and aperture. Depth of field increases with shorter focal lengths and smaller aperture openings.

Dequantization: The process of rescaling the quantized DCT coeffiecints after their representation in the bitstream has been decoded and before they are presented to the inverse DCT.

Descrambler: Decoder or Decryptor.

Desktop Video: Video post production using personal computers at the desktop rather than a traditional post-production environment. Desktop video may include video storyboarding, editing, and/or special effects generation using personal computer equipment rather than dedicated post-production hardware.

Diaphragm: A flexible plate within a microphone that vibrates in sympathy with sound pressure waves. It assists in converting the sound energy into an electrical signal.

Digital: Expressed as a series of digits. A signal is said to be digital if its independent variable (e.g. time) and dependent variable (e.g. voltage, current, amplitude) are assigned dicreet values.

A method of representing information using a sequence of ones and zeros for storage and interpretation by a computer. In digital transmission, analog signals which are originally in a continuous form are converted to discrete signals of zeros or ones to be transmitted to a receive site, interpreted, and used to reconstruct the original analog signal.

Digital Framestore: A memory device that scans and stores a complete frame of video information after the information has been converted from analog to digital form. Digital framestores are used in the creation of digital special effects.

Digital Video: Video which is described by discrete voltage levels (represented by numbers) as opposed to the infinite range of values possible with analog video. Among its advantages, Digital Video may be copied with little or no change from one generation to the next.

Digitization: The process of changing an electronic analog signal into a discrete binary form. The process is divided into the steps of sampling the analog signal at set moments in time, quantizing each sample (assigning it a numerical value), and translating the sample into a discrete binary number. The advantages of digitization, include reliable high-speed signal transmission, quality duplication, and easy manipulation and processing. A copy of a digital signal is virtually identical to the original. The primary disadvantage of digital signals is their large size resulting in high-storage requirements. Digital compression techniques are helping to overcome this disadvantage.

Digitizer: A computer-peripheral device that converts an analog signal (images or sound) into a digital signal. With an image, the digitizer may employ an image scanner or a traditional video camera to pick up the image for digitizing.

Direct Color: The process of recording full-bandwidth video information onto videotape. This system is used in the 1-inch Type C and D-2 Digital formats.

Disc: A generic name for an optically recorded medium as opposed to disk which refers to magnetically recorded material.

Discreet Component: An electronic component that contains only one function (i.e. transistor, resisto which they were presented at the input of the encoder.

Dissolve: As one scene is fading out, another scene is simultaneously coming in. At the middle of the dissolve, both scenes are on the screen with the same 50% exposure. In single camera taping techniques, the dissolves are added in post production.

Distribution Amplifier (DA): A device which converts a single input into multiple outputs which can be distributed to various devices within the system. DAs assure that signal quality is maintained as the signal moves around the system.

DLC: Digital loop carrier. Multiplexed digital circuits which deliver digital information from a CO to an end user over twisted pair of copper wire phone lines.

DME: Sony’s term for Digital Multi-Effects.

Doubling: Strengthening a signal via mixing a delayed version with the original signal.

Downlink: An earth station that receives an audio, video and/or data signal to a satellite transponder. This term is also used to refer to the program site that is receiving the signal.

Downstream Keyer: Also called a DSK, a downstream keyer electronically appears after all other switcher functions — visually on top of all other layers and buses. Any operations performed on the switcher M/Es will not affect the downstream key video.

Downwardly Compatible: A feature by which an older format can play material recorded on a newer format. For instance, U-matic¨ SP tapes can be played back on older U-matic decks while Hi8ª tapes cannot be played back on 8mm equipment.

DRAM: Dynamic Random Access Memory DRAM has to be refreshed at a periodic rate.

DRAW Disc: Direct Read After Write. An analog disc recorder for making a single copy of a videodisc for the purpose of prototyping or checking your program before sending your master tape to be mastered and replicated in the standard optical format. DRAW discs are not compatible with standard laserdisc players and must be played back on a DRAW player or Player/Recorder.

Driver (Device Driver): A software program that translates commands between the computer operating system and a peripheral device such as a CD-ROM drive, videodisc player, computer printer, or other device.

Drop Frame Editing: Time code editing where video time is corrected for clock time. For every second of time, 29.97 frames of video occur. This creates an error of 3.5 seconds an hour which is corrected by dropping two frames from time code every minute except for the 10, 20, 30, 40, 50, and 60th minutes. The choice when editing for clock time. Only the frame numbers are dropped, not the actual video frames.

Drop Shadow: Key effect that provides a shadow just behind the key and over the background. This effect is often combined with keyed text to make it more attractive and readable.

Drop-Out: Loss of a portion of the video picture signal caused by a lack of iron oxide on that portion of the videotape, or by dirt or grease covering that portion of the tape.

DS-O: Digital Service, Level 0: A standard for digital communications channels in North American which communicate at 64 Kbps

DS-1: Digital Service, Level 1: A standard for digital communications channels in North American which communicate at 1.544 Mbps. Also referred to as T- 1.

DS-3: Digital Service, Level 3: A standard for digital communications channels in North American which communicate at 45.304 Mbps. Also referred to as T-3.

DSC Chart: David S. Corley chart used for color matrix set-up.

DSM: Digital Storage Media A digital storage or transmission device or system.

DSS: Digital Satellite System: Refers to the small dish antenna and accompanying set top receiver I decoder that is used in conjunction with DBS service.

DSTB: Digital set top box: Device which receives a digital stream, demodulates and decompresses it and delivers a video signal to the TV, and in some cases other types of information to other home devices. The set top box may also contain a tuner and descrambler.

DSU (Data Service Unit): A videoconferencing/telecommunications term: A CPE (Customer Premises Equipment) component which interfaces to a digital circuit such as Tl. The DSU converts the digital data to a format suitable for transmission. The DSU is generally used in conjunction with a CSU (Channel Services Equipment).

DTE (Data Terminal Equipment): A videoconferencing/telecommunica-tions term: Computer, terminal, or other end-user device that connects to a network through a DCE (Data Circuit-Terminating Equipment).

DTF: Digital Tape Format. Digital information recorder format. Sony model numbers GY-10C, GY-10D (Akebono) and GY-2120.

Dual Channel Mode: A mode, where two audio channels with independent program contents (e.g. bilingual) are encoded within one bitstream. The coding process is the same as for the stereo mode.

Dub: (1) The process of copying one videotape to another. (See Y-688 Dub). (2) One of the two terms used to describe an audio or videotape duplicate. Dupe is now a more generally used term. To dub is also a term meaning to copy.

Dub Cable: Transfers the video information in a component form. (The dub cable does not carry audio). This means that the copied image will have less noise and less image deterioration than if the video signal is run through the line cable. In hard-cut editing, the image quality saved by using a dub cable, in terms of generational loss, is significant. It is possible to run dub cables between different format videotape recorders.

Duplex Audio: An audio teleconferencing system which allows all sites to be heard simultaneously. These systems generally do not use voice switches. They operate like normal telephone handsets used between two sites. Sometimes referred to as Open audio.

DVE (Digital Video Effects): Used to manipulate video images: fly-in, squeeze room, rotate spin. DVE effects have been exclusively in the high-end video production domain until recently when low-cost extension boards have become available to accomplish these effects on the Macintosh and other PCs.

DVI: Intel Corporation's Digital Video Interactive is a set of proprietary chips that allow the recording of 72 minutes of full-motion video, 40-hours of digital audio, or a combination of both audio and video on a CD-ROM disc. The video quality is said to rival that of VHS 1/2-inch videotape. DVI is not yet a commercial product.

Dwell Time: The amount of time a sequential switcher allows a particular image to remain displayed.

Dye Sublimation: A printing process that produces photo-realistic, hard-copy prints from video and computer imagery. The process uses special dye films affixed to coated paper stock by use of a multi-element thermal head which achieves a smooth, finished blend of dyes.

Dynamic Microphone: A low-impedance type of microphone that operates on electromagnetic principals.

Dynamic Range: Difference between the maximum and minimum distinguishable signal levels.

1.) Audio Term: The range of acceptable loudness an audio device can handle without distortion.

2.) The highest and lowest signal levels (amplitude) on a given device.