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Terms and Glossary

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d


D1

A component digital video recording format that uses data conforming to the ITU-R601 standard. Records on 19mm magnetic tape. (Often used incorrectly to refer to component digital video)

D2

A composite digital video recording format that uses data conforming to SMPTE 244M. Records on 19mm magnetic tape. (Often used incorrectly to refer to composite digital video)

D3

A composite digital video recording format that uses data conforming to SMPTE 244M. Records on 1/2" magnetic tape

D5

A component digital video recording format that uses data conforming to the ITU-R601 standard. Records on 1/2" magnetic tape

DARS

Digital Audio Reference Signal. A reference signal conforming to the format and electrical specification of the AES3 standard, but often has only the preamble active. This signal is used for synchronization in digital audio studio applications. The recommended practice AES11-1997 gives further information on the use of a DARS reference

DAT

Digital audio tape for high quality digital audio.

Datacasting

Jargon referring to the propagation of information from one source to another source.

Daylight saving time (DST)

Daylight Saving Time (DST) or Summer Time as it is called in many countries, is a way of getting more daylight out of the summer days by advancing the clocks by one hour during the summer. Then, the sun will appear to rise one hour later in the morning when people are usually asleep anyway, at the benefit of one hour longer evenings when awake. The sunset and sunrise are one hour later than during normal time

dB FS

Abbreviation for "decibels full scale," a unit of power as measured by a digital device. A digital measurement has a maximum value M depending on the number of bits used. If the actual power measurement is p, the dB FS value displayed is 20 log10(p/M) dB FS. Since p cannot exceed M, this reading is always negative

dB m, dB W

Logarithmic units of power used in electronics. These units measure power in decibels above the reference level of 1 milliwatt in the case of dB m and 1 watt in the case of dB W. A power of n watts equals 10 log n dB W; conversely, a power of p dB W equals 10(p/10) watts. The same formulas link dB m to milliwatts. An increase of 10 dB m or 10 dB W represents a 10-fold increase in power. Since 1 watt = 1000 milliwatts, 0 dB W = 30 dB m

dB u

A logarithmic unit of power, similar to dB m but computed from voltage measurements. The reference level is 0.775 volts, the voltage which generates a power of 1 milliwatt across a circuit having an impedance of 600?. A voltage of V volts corresponds to a power of 20 log10(V/0.775) dB u

dB- (prefix)

A symbol indicating that a measurement is made using a logarithmic scale similar to that of the decibel in that a difference of 10 dB- corresponds to a factor of 10. In each case, the actual measurement is compared to a fixed reference level r and the "decibel" value is defined to be 10 log10(a/r). Many units of this kind have been used and only a few of the more common ones are mentioned in the next entries. In each case the dB symbol is followed by a second symbol identifying the specific measurement. Often the two symbols are not separated (as in "dBA"), but the Audio Engineering Society recommends that a space be used (as in "dB A")

De-embedding

The process of extracting an embedded signal from an input stream to generate two separate signals, perhaps with different standards. This term is often used to describe the process of extracting AES audio that has been embedded onto a serial digital video signal

decibel (dB)

A customary logarithmic measure most commonly used (in various ways) for measuring sound. The human ear is capable of detecting an enormous range of sound intensities. Furthermore, our perception is not linear. Experiment shows that when humans perceive one sound to be twice as loud as another, in fact the louder sound is about ten times as intense as the fainter one. For this reason, sound is measured on logarithmic scales. Informally, if one sound is 1 bel (10 decibels) "louder" than another, this means the louder sound is 10 times louder than the fainter one. A difference of 20 decibels corresponds to an increase of 10 x 10 or 100 times in intensity. The beginning of the scale, 0 decibels, can be set in different ways, depending on exactly which aspect of sound is being measured. See also dB-

Degausser

Device for reducing residual magnetism.

Demodulation

A method for extracting digital information stored in a specific pattern on a radio frequency (RF) signal.

Demux

An abbreviation for 'de-multiplexing' which is the separation of Multiplexed data streams for dispersal to different devices. This term is often used synonymously with De-embedding when used to describe the process of extracting AES audio that has been embedded onto a serial digital video signal

Digital

Information sent as a series of high (1) and low (0) signals separated by a fixed period of time. Signals formed of series of coded pulses (numbers) as distinct from continuous analogue signals.

Digital light projection (DLP)

A technique developed by Texas Instruments that creates a video image on a piece of silicon and uses mirrors and light to project the image onto a viewable screen.

Digital satellite service (DSS)

MPEG-2-based digital transmission format (e.g., DirectTV).

Digital set-top-box (DSTB)

A device that receives and decodes digital video broadcasts for consumer viewing.

Digital Single Lens Reflex Camera

Traditionally, these were still only cameras, however since 2007 they have been able to shoot video. They are being used increasingly by small construction companies for a number of reasons; the quality of the lenses and images at low light levels are both high, and when combined with the large sensor and the fact they are cheaper than most traditional broadcast cameras, this makes them a natural choice for many companies. Some broadcasters however do not accept the footage as HD due to the face it is shot at below 50 Mbps. Older models also did not record a timecode and were not able to record synched sound, however later models are also beginning to remedy these issues.

Digital television (DTV)

A device that receives, decodes, and displays digital video broadcasts (in both high-definition and standard-definition formats) for consumer viewing.

Digital Video / Digital Audio

A video or audio stream encoded into binary digits instead of wavelengths and amplitudes

Digital video broadcast (DVB)

MPEG-2-based digital television standard that defines formats for cable, satellite, and terrestrial broadcast.

DIN

Deutscher Industrie Nornenausschus, a German standards body.

Discrete Cosine Transform (DCT)

A step used in the MPEG coding process to convert data from spatial to temporal domain.

Dissolve

Vision mixer effect where picture fades out as second picture fades in.

Distribution Amplifier

An electronic device which accepts a broadcast signal, amplifies it, and then outputs the same signal many times. Essentially a signal copying device

DNW

Model number prefix for Sony Digital Betacam broadcast grade equipment

DNxHD

Avid Media Composer's preferred codec. Typically HD footage will be recorded at or transcoded to 185 Mbps.

Downconverter

A converter which takes an HDTV signal and rescales it into a standard definition TV signal

Downstream

A broadcasting term meaning closer to the point of final transmission. Indicates the system is robust enough to handle "on-air" signals with confidence

Downstream Keyer

A caption superimposer on mixer output, i.e. not affected by the vision mixer standard.

Dropframe

A method of adjusting the nominal 30 frame per second counting rate of SMPTE 12M-1 time code to the actual counting rate of approximately 29.97 frames per second - a difference of 1 part in 1001. This correction drops 108 frames per hour by skipping frame counts 0 and 1 at the beginning of each minute, except minutes 0, 10, 20, 30, 40 and 50. See also LTC and VITC

Dropout

Loss of signal during replay caused by lack of magnetic coating on a portion of videotape, or by particles of dirt or grease.

Dropout Compensator

Device which reduces subjective effect of videotape dropout by repeating a previous signal.

Drum

Mechanical assembly containing the headwheel in a helical scan VTR.

DSR

Model number prefix for Sony DVCAM professional grade equipment

DVB-ASI

Digital Video Broadcast-Asynchronous Serial Interface. A standard definition digital video standard with a bit rate of 270Mb/s

DVW

Model number prefix for Sony Digital Betacam broadcast grade equipment

DWDM

Dense Wave Division Multiplexing. A method for combining multiple fiber optic signals of different wavelengths onto a single strand of cable in a much smaller wavelength spectrum than CWDM. Dense Wave Division Multiplexing allows up to 80 separate channels of data to be carried over a single optical cable using different wavelengths for each channel

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