|last updated Wed Apr-21-2010 07:15|
AV Processing⁄AV terminology
Glossary of AV terms (from AMIA compendium of moving image cataloging practice, 2001, unless otherwise noted)
Analog A type of electrical signal (such as that recorded on videotape) whose value is continuously variable. Thses signals degrade in successive generations. Related term: digital.
Anamorphic squeeze This process is used to achieve a widescreen image, when the image is considerably wider than standard NTSC fare, once it is "unsqueezed". The wider image is squeezed into the skinnier aspect ration, which is usually the NTSC standard of 4:3⁄1.33:1. The end result is a picture with really skinny objects. Another option which has less detail,. but is more widely used is letterboxing the picture. Related glosary terms: letterbox, pan & scan.
Aspect ratio This describes the width of a picture to the height. The NTSC standard is 4:3. The current HDTV standard (2001) is 16:9, or 1.78:1.
Audio DVD These are DVDs that contain audio files or a combination of audio and video files. They cannot be played on a compact disc player. They must be played on a PC or a universal DVD player.
Clone A digital to digital dub without intermediate analog steps, and therefore without generational loss of quality. Related glossary terms: dub.
Digital A type of electrical signal whose value can exist only at predefined levels. Digital dubbing produces and exact replica of the previous generation with no signal degradation. Related glossary terms: analog, clone.
Dolby noise reduction A patented electronic technique to reduce audio noise on a recording. Dolby A, Dolby B, Dolby C and Dolby SR are common noise reduction formats: they are not interchangeable.
Dub A dub is a duplication of an electronic recording within or between formats to produce a copy of a videotape or audio tape. A dub in one generation away from the previous recording. Loss of quality occurs in each successive generation of an analog dub. Digital dubbing, or cloning does not cause signal loss. Dubs are made for editing, distribution or protection purposes. Relate glossary term: clone.
DVD (from dvddemystified.com and afterdawn.com⁄glossary)
The original acronym came from "digital video disc;" according to some, or may stand for Digital Versatile Disc. DVD is the new generation of optical disc storage technology. DVD is essentially a bigger, faster CD that can hold cinema-like video, better-than-CD audio, still photos, and computer data.
DVD is very often used as a replacement acronym for DVD-Video, which is one standard based on DVD format. DVD-Video is a standard developed by DVD Forum and specifies how video should be stored on optical DVD disc. DVD-Video specs allow two different kind of video encoding algorithms to be used: MPEG-2 and MPEG-1. Virtually all DVD-Video discs use MPEG-2 format, mostly because of its superiority over MPEG-1 in terms of video quality.
HDTV High Definition Television is a viewing format with an aspect ration of 16:9⁄1.78:1 -- a much more rectangular image (16 units across by 9 units up). Also there is a dramatic increase in the lines of resolution (1125), giving us about 6 times the picture information of 525 line television, as well as to have Dolby Digital be the official sound format. There are two forms in existence. There is an analog system in Japan, and a digital system proposed by the Grand Alliance for the U.S. This system is supposed to co-exist with and eventually replace NTSC. Related glossary term: NTSC.
Letterbox This process, which is used on many laser discs and some TV broadcasts, is used to achieve a widescreen image, where the image is considerably wider than standard NTSC fare. The end result is a wider picture with black bands on the top and bottom of the screen. Another option with greater detail but less widely used is anamorphically squeezing the picture. Related glossary terms: anamorphic squeeze, pan & scan.
MPEG (pronounced M-peg), which stands for Moving Picture Experts Group, is the name of family of standards used for coding audio-visual information (e.g., movies, video, music) in a digital compressed format. The major advantage of MPEG compared to other video and audio coding formats is that MPEG files are much smaller for the same quality. This is because MPEG uses very sophisticated compression techniques.
NTSC Currently (2001) in the U.S., we receive our television signal on the NTSC (National Television System Committee) standard. It has an aspect ration of 4:3 -- a relatively "square" image (4 units across by 3 units up). It also scans in 525 lines to make up the picture image. Related glossary term: HDTV.
NTSC, PAL, SECAM NTSC is an abbreviation for National Television System Committee, the body that sets color standards for broadcast television in the U.S. NTSC standards were subsequently adopted by Canada, Japan, South Korea, Mexico, and several Latin American countries. PAL (Phase Alternation Line) is the British broadcast color standard. SECAM (Sequential Couleur à Memoire) is the French broadcast standard. The three systems are incompatible. A signal recorded in any given standard must run through a conversion device in order to be viewable in a different system.
Pan & Scan A method where a director in a studio decides which part of the 16:9 image shoud be cut off to get the best and most informative 4:3 image. This is more or less like sliding a 4:3 schrrn template of the 16:9 image. The disadvantage is that the viewer has no say in this, and depends of the individual at the controls. Related glossary terms, anamorphic squeeze, letterbox.
VCD (from http:⁄⁄www.afterdawn.com⁄glossary⁄ )
VCD stands for VideoCD (version 2.0 to be more specific). VideoCD is a standard developed in early 1990's that allows regular CD to contain 74 minutes of video and audio. Both, video and audio, are encoded in MPEG-1 format and stored on the CD in specific format.
VideoCDs can be played in most of the stand-alone DVD players, in all stand-alone VCD players and in all computers that have CD-ROM drive. This is the VCD's strong point against DivX format which is based on MPEG-4 audio⁄video encoding technology.
VideoCD resolution is in PAL format 352 x 288 pixels with 25 frames⁄second. In NTSC format it is 352 x 240 pixels with 29,97 frames⁄second (except in NTSC film format, where the framerate is 23,976 frames⁄second. Audio is encoded with bitrate of 224 kbit⁄sec in MPEG-1 Layer2 format (in both PAL and NTSC versions). Video is encoded with bitrate of 1150 kbit⁄sec.
VideoCDs are pretty rare in western countries, but a very popular method for movie distribution in China, Hong Kong, Singapore, Malaysia, etc.. Some studios release some of their movies officially for VCD format in Asia. It has almost completely replaced regular VHS format in Asia, because cheap VCD recorders are widely available there. VideoCD's successor is called SuperVideoCD.
Widescreen TV Uses an aspect ration of 16:9 compared with the common TV aspect ratio of 4:3. Widescreen stretches out a 4:3 image to the sides to fill up the 16:9 screen.