a b c d e f h l n p s t v w y

a

A:B:C notation

The a:b:c notation for sampling ratios, as found in the CCIR-601 specifications, has the following meaning:

• 4:2:2 means 2:1 horizontal downsampling, no vertical downsampling. (Think "4 Y samples for every 2 Cb and 2 Cr samples in a scanline".)
• 4:1:1 *ought* to mean 4:1 horizontal downsampling, no vertical. (Think "4 Y samples for every 1 Cb and 1 Cr samples in a scanline".) But it is often misused to mean the same as:
• 4:2:0 means 2:1 horizontal and 2:1 vertical downsampling. (Think "I want some of whatever these guys were taking.")

Not only is this notation not internally consistent, but it is incapable of being extended to represent any unusual sampling ratios, e.g. different ratios for the Cb and Cr channels.

courtesy Luigi Filippini

actor

Another term for the star of your BackDrop video production

arithmetic coding

A mechanism of representing messages as intervals of the real numbers between 0 and 1

ATV

Although sometimes used interchangeably, advanced and high-definition television (HDTV) are not one and the same. Advanced television (ATV) would distribute wide-screen television signals with resolution substantially better than current systems. It requires changes to current emission regulations, including transmission standards. In addition, ATV would offer at least two-channel, CD-quality audio

b

B-Y R-Y

The human visual system has much less acuity for spatial variation of colour than for brightness. Rather than conveying RGB, it is advantageous to convey luma in one channel, and colour information that has had luma removed in the two other channels. In an analog system, the two colour channels can have less bandwidth, typically one-third that of luma. In a digital system each of the two colour channels can have considerably less data rate (or data capacity) than luma.

Green dominates the luma channel: about 59% of the luma signal comprises green information. Therefore it is sensible, and advantageous for signal-to-noise reasons, to base the two colour channels on blue and 1red. The simplest way to remove luma from each of these is to subtract it to form the difference between a primary colour and luma. Hence, the basic video colour-difference pair is (B-Y), (R-Y) [pronounced "B minus Y, R minus Y"].

The (B-Y) signal reaches its extreme values at blue (R=0, G=0, B=1; Y=0.114; B-Y=+0.886) and at yellow (R=1, G=1, B=0; Y=0.886; B-Y=-0.886). Similarly, the extrema of (R-Y), +-0.701, occur at red and cyan. These are inconvenient values for both digital and analog systems. The colour spaces YPbPr, YCbCr, PhotoYCC and YUV are simply scaled versions of (Y, B-Y, R-Y) that place the extrema of the colour difference channels at more convenient values.

browser

A program that allows a person to read hypertext, which makes up the contents of most pages on the web; when it's a graphical browser, it also allows you to view images. The browser gives some means of viewing the contents of pages and of navigating from one page to another. Netscape Navigator, Internet Explorer, Mosaic, etc. are all examples of web browsers. AOL and other service providers often use a form of one of these browsers, which may behave slightly differently. Different browsers make pages look different.

c

CCIR-601

CCIR Rec. 601 is a specification document which specifies the image format, acquisition semantic and parts of coding for digital "standard" television signals

CCITT

Commite' Consultatif International de Telecommunications et Telegraphy -- A committee of the International Telecommunications Union responsible for making technical recommendations about telephone and data communication systems for PTTs and suppliers. Plenary sessions are held every four years to adopt new standards

CD-DA

Compact Disc-Digital Audio format, or your standard garden-variety music CD

CD-I

Compact Disc Interactive, a standard platform for multimedia applications. This is a standalone system that by itself provides images, music and control

CD-ROM

Compact Disc Read Only Memory; a computer cna read the bits on this disc as computer data

CD-XA

CD-ROM extension designed for digital audio and still image support. It incorporates the audio from the CD-I format with the data on a CD-ROM

CIF

Common Image Format, the structure for representing the picture information of a single frame of digital HDTV

CODEC

CODEC stands for Coder/decoder, or compression/decompression. This is the process of converting analog signals to digital (and vice versa) to be read by a computer or transmitted over a network. Your video camera utilizes this to produce a video stream for transmission across the Internet. This process also reduces the size of the multimedia file before transmission. This process can be accomplished through software, hardware, or a combination of both

cookies

Cookies are a mechanism used by web sites to track your history at the site. Although there is a great deal of hype and negative press about cookies, they are very benign. Cookies only store information that (a) you willingly provide to the web site or (b) is actually already available in a web server's log file. A given site can only view cookies that were accepted from them in the first place. So many misconceptions about cookies exist that CIAC (The U.S. Department of Energy's Computer Incident Advisory Capability) issued an informational release about them. Please review the release and make your own determination about cookies

d

domain name

A method of identifying computer addresses. For example, Sabbatical, Inc. is a commercial entity, so our domain is .com. The president's address, president@whitehouse.gov, indicates "gov" for government. Other top-level domains include educational institutions (.edu), companies (.com), networks (.net) and organizations (.org), plus additional ones to indicate countries.

DVI

Digital Video Interactive enables display of video, still images, text, and/or audio through computers. It is based upon the YUV system

e

E-mail

Messages automatically passed from one computer user to another, often through computer networks and/or via modems over telephone lines

f

flame

An electronic mail (e-mail) or Usenet news message intended to insult, provoke or rebuke, or the act of sending such a message. Sometimes a flame will be delimited by marks such as "flame on...flame off"

h

H.261

Recognizing the need for providing ubiquitous video services using the Integrated Services Digital Network (ISDN), CCITT (International Telegraph and Telephone Consultative Committee) Study Group XV established a Specialist Group on Coding for Visual Telephony in 1984 with the objective of recommending a video coding standard for transmission at m x 384 kbit/s (m=1,2,..., 5). Later in the study period after new discoveries in video coding techniques, it became clear that a single standard, p x 64 kbit/s (p = 1,2,..., 30), can cover the entire ISDN channel capacity. After more than five years of intensive deliberation, CCITT Recommendation H.261, Video Codec for Audiovisual Services at p x 64 kbit/s, was completed and approved in December 1990. A slightly modified version of this Recommendation was also adopted for use in North America.

The intended applications of this international standard are for videophone and videoconferencing. Therefore, the recommended video coding algorithm has to be able to operate in real time with minimum delay. For p = 1 or 2, due to severely limited available bit rate, only desktop face-to-face visual communication (often referred to as videophone) is appropriate. For p>=6, due to the additional available bit rate, more complex pictures can be transmitted with better quality. This is, therefore, more suitable for videoconferencing.

HDTV

High-Definition Television, a system with twice the horizontal and vertical resolution of current systems and a frame rate of at least 24 Hz

home page

A Web page that acts as a starting point. A user can go from a home page's hyperlinks to different sites across the world-wide web. Also used by folks who have a "web site" on the Web, e.g. "go check out my home page"

HTTP

Hypertext transport protocol is the Internet standard that enables the communication and distribution of information across the Internet. HTTP is the mechanism by which you can follow hyperlinks from one page to another on a web site.

Huffman Coding

A compression mechanism which assigns short codes to frequently occurring characters, and longer codes to characters that occur less frequently, thus reducing the number of bytes required to represent a larger portion of text

hyperlink

A highlighted word or image on a Web page that, when clicked on by a mouse or invoked by hitting return while your cursor is focused on it, can connect the user to a new location.

l

logo boy

Logo Boy™ is one of our trademarked images for the BackDrop product. LogoBoy symbolizes what you can do with BackDrop

Luma

Luma represents the Y component of video. In a mechanism where the RGB (red/green/blue, the three primaries standardized for video) corresponds to human vision, the luma coefficient is a function of the white point

n

NTSC

National Television System Committee, the USA video standard. It has an image format of 4:3, 525 lines, 60 Hz and 4Mhz video bandwidth with a total 6 Mhz of video channel width. NTSC uses YIQ

p

PAL

Phase Alternating Line is the European video standard, with image format 4:3, 625 lines, 50 Hz and 4Mhz video bandwidth with a total 8 Mhz of video channel width. PAL uses YUV

s

scene

A combination of star, background video, and foreground special effects and transitions

SECAM

Sequentiel Coleur A Memoire, another European video standard with image format 4:3, 625 lines, 50 Hz and 6 Mhz video bandwidth with a total 8 Mhz of video channel width

SMPTE

Society of Motion Picture and Television Engineers

spam

Hey, we hate it too! From the Monty Python "Spam" song, this refers to the posting of irrelevant or inappropriate messages to one or more Usenet newsgroups or mailing lists in deliberate or accidental violation of netiquette. Also used to describe general posting of unsolicited mail such as get-rich schemes, chain letters, etc

stand-in

So, you're on an airplane somewhere, you don't have your video camera handy, but you want to work up this nifty idea for a scene while you're idle. You can use your stand-in to represent where you, the star, would be in your completed BackDrop™ scene

star

Why, that is you! BackDrop makes you the star of your very own Desktop Broadcast

t

T1Q1.5

The T1Q1.5 Video Teleconferencing/Video Telephony (VTC/VT) ANSI Subworking Group (SWG) was formed to draft a performance standard for digital video. Important questions were asked, relating to video digital performance characteristics of video teleconferencing/video telephony:

• Is it possible to measure motion artifacts with VTC/VT digital transport?
• If it can be done by objective measurements, can they be matched to subjective tests?
• Is it possible to correlate the objective measurements of analog and digital performance specification?

The VTC/VT Subworking Group's goal is to answer these questions. It has become a first step to the process of constructing the performance standard.

TAPI

Telephony Application Programming Interface. This is an API for connecting PCs running Windows to telephone services

v

V.80

V.80 class modems allow users to make video connections with other users equipped with an H.324 system, which includes a readily available camera and video capture card.

A system equipped with a V.80 modem and the proper H.324 software and hardware can simultaneously exchange video, voice, and data with another user.

w

World-Wide Web

A web of linked documents that provide access to information and services over the Internet. Documents contain links to other documents and allow you to “travel” using your web browser software from one document to another. It is only a part of the Internet. The Internet is the network on which the World Wide Web works its magic. AOL is not the Internet or the World Wide Web; it is one of many dial-up connection service that provides a gateway to the Internet’s services

y

YCC

YCC is the Kodak PhotoCD format. It is similar to YCbCr

YUV

In composite NTSC, PAL, or S-Video systems, it is necessary to scale (B-Y) and (R-Y) so that the composite NTSC or PAL signal (luma plus modulated chroma) is contained within the range -1/3 to +4/3. These limits reflect the capability of composite signal recording or transmission channel. The scale factors are obtained by two simultaneous equations involving both B-Y and R-Y, because the limits of the composite excursion are reached at combinations of B-Y and R-Y that are intermediate to primary colors