D
Digital Visual Interface (DVI): A high-speed digital interface for
visual data (both video and still images), typically used in
connecting a computer with a display device but also on some
HDTV monitors.
Digital TV (DTV): Broadcasts of digital television signals in the
US following the standards issued by the ATSC, which specify the
18 formats to be used. The most common high-definition (HDTV)
formats are variants of 1080i (1,080 interlaced scan lines) and
720p (720 progressive scan lines), while the enhanced-definition
(EDTV) formats all use 480 progressive scan lines (480p) and the
standard-definition (SDTV) formats use 480 interlaced scan lines
(480i). Though the EDTV and SDTV formats can have both
widescreen (16:9) and conventional (4:3) aspect ratios, the HDTV
formats are widescreen only.
Direct-view TV: Usually refers to a CRT set whose single picture
tube is intended for viewing head on, not projecting onto a screen.
Dolby Digital: The Dolby Labs format for digital surround sound
providing up to 5.1 channels; used in DVDs, the digital TV system
and some laserdiscs; formerly called AC-3 (for Audio Code 3).
Dolby Pro Logic (DPL): An enhancement to Dolby Surround
decoding that extracts a center channel and improves channel
separation by means of logic-steering circuitry. A new, digital
version called Dolby Pro Logic II not only does the decoding in the
digital domain (which most DPL decoders already do) but can also
manipulate a Dolby Surround-encoded or plain two-channel signal
to simulate 5.1-channel playback, with separate modes optimized
for music and movie soundtracks.
Dolby Surround: The consumer name for the Dolby Stereo
system used for movie soundtracks. Dolby Surround encoding
matrixes four channels – left, ceter, right, and surround – into two
stereo-compatible channels (L
T
/ L
T
) that can be carried on any
two-channel sound medium. Basic Dolby Surround decoding
extracts the single surround channel to feed a pair of speakers at
the sides or back of the room; such decoders have now largely
been superseded by Dolby Pro Logic decoders as well as by Dolby
Digital systems.
DTS: A multichannel codec developed by Digital Theatre Systems
and used to carry a 5.1-channel sound-track on DVDs, CDs, and
laserdiscs.
DVD Video: A DVD format used almost exclusively for movies and
other image-intensive program material; it employs MPEG-2 video
encoding and Dolby Digital or DTS and PCM stereo audio encoding.
Most movie DVDs offer up to 5.1 channels of surround sound, and
today most come in widescreen format.
E
EDTV Monitor: A TV set that can display a 480p-format
enhanced-definition digital TV signal when connected to an
outboard tuner/decoder.
Electronic program guide (EPG): An onscreen program guide /
menu system that is used both to select the program to be viewed
and to set the recording timer in a VCR or hard-disk recorder.
Schedule information is downloaded at night from the program
service provider via a built-in mode connected to a telephone line
or decoded from a TV channel’s VBI.
Enhanced-definition TV (EDTV): A subset of the digital TV
(DTV) standard that is superior to standard-definition TV chiefly
because it uses 480p (progressive-scan) formats at up to 60 fps for
display – with either a 16:9 or 4:3 aspect ratio – rather than
SDTV’s 480i (interlaced-scan), 30-fps formats.
F
5.1-channel: The conventional designation for a medium or
system that carries six channels of sound information: front
left/centre/right, surround left/right, and a restricted-bandwidth
(hence the “.1”) LFE channel.
Frame: A complete, individual picture on a motion-picture film or
contained in a video signal.
Frame rate: The rate at which frames are displayed. In typical
modern movies the frame rate is 24 per second; in color NTSC
video it is 29.97 per second.
Front projector: A type of video display in which the projector
elements are housed in a separate unit, not connected to the
screen and mounted in front of it, much like a movie projector;
front projectors are often mounted on the ceiling.
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