Glossary of Digital Broadcasting & Digital Communications Terms

Edition of 2005

Mr. Tsuyoshi Miura (Senior Volunteer)

-#3:2 pull-down: Method used to map the 24 fps of film onto the 30 fps (60 fields) of 525-line TV, so that one film frame occupies three TV fields, the next two, etc. It means the two fields of every other TV frame come from different film frames making operations such as rotoscoping impossible and requiring care in editing. Some sophisticated equipment can unravel the 3:2 sequence to allow frame-by-frame treatment and subsequently re-compose 3:2. The 3:2 sequence repeats every five TV frames and four film frames, the latter identified as A-D. Only film frame A is fully on a TV frame and so exists at one time code only, making it the editable point of the video sequence. 4fsc: Four times the frequency of SC (subcarrier). The sampling rate of a D2 digital video signal with respect to the subcarrier frequency of an NTSC or PAL analog video signal. The 4fsc frequency is 14.3 MHz in NTSC and 17.7 MHz in PAL. 4:1:1: This is a set of sampling frequencies in the ratio 4:1:1, used to digitize the luminance and color difference components (Y, R-Y, B-Y) of a video signal. The four represents 13.5 MHz, the sampling frequency of Y, and the ones each 3.75 MHz for R-Y and B-Y. With the color information sampled at half the rate of the 4:2:2 system, this is generally used as a more economical form of sampling for 525-line picture formats. Both luminance and color difference are still sampled on every line. But the latter has half the horizontal resolution of 4:2:2, while the vertical resolution of the color information is maintained. For 525-line pictures, this means the color is fairly equally resolved in horizontal and vertical directions.

4:2:0: A sampling system used to digitize the luminance and color difference components (Y, R-Y, B-Y) of a video signal. The four represents the 13.5 MHz sampling frequency of Y, while the R-Y and B-Y are sampled at 6.75 MHz--effectively between every other line only (one line is sampled at 4:0:0, luminance only, and the1

next at 4:2:2). This is generally used as a more economical system than 4:2:2 sampling for 625-line formats so that the color signals have a reasonably even resolution in the vertical and horizontal directions for that format. 4:2:2: A commonly used term for a component digital video format. A ratio of sampling frequencies used to digitize the luminance and color difference components (Y, R-Y, B-Y) of a video signal. It is generally used as shorthand for ITU-R 601-5 STUDIO ENCODING PARAMETERS OF DIGITAL TELEVISION FOR STANDARD 4:3 AND WIDE-SCREEN 16:9 ASPECT RATIOS. The term 4:2:2 describes that for every four samples of Y, there are two samples each of R-Y and B-Y, giving more chrominance bandwidth in relation to luminance compared to 4:1:1 sampling. This Recommendation specifies methods for digitally coding video signals. It includes a 13.5 MHz sampling rate for both 4:3 and 16:9 aspect ratios with performance adequate for present transmission systems. An alternative 18 MHz sampling rate for those 16:9 systems which require proportionately higher horizontal resolution is also specified. Specifications applicable to any member of this family of standards are presented first. 4:4:4: Similar to 4:2:2, except that for every four luminance samples, the color channels are also sampled four times. 16:9: See aspect ratio, and widescreen 48sF: 48 segmented frames. The process of taking 24-frame progressive images and deconstructing them to produce 48 interlaced frames each with half of the number of lines of resolution to allow some HDTV processors to pass the signal and for viewing on an interlaced monitor without flicker. 5.1 Channel Sound: 1) A five point one channel sound system actually has 6 channels of surround sound to better reproduce ambience and provide a more enjoyable listening experience. The 5 channels feed speakers around the listening position and are at centre front, and then left, right, rear left and rear right. The extra point one refers to the reduced-bandwidth low frequency effects (LFE) channel where the bass sounds from all directions are combined into a single channel that requires a (usually larger) sub-woofer loudspeaker. This combining can be done, as human hearing cannot sense the direction of these very low frequency sounds below about 100 Hz. This avoids all speakers having to cover the full frequency range, and extended bass response usually requires large speakers and enclosures. In a domestic installation this solution is both lower cost and space saving. Surround sound systems can source multiple channels either from:2

stereo (two channel) program that has been captured with the ambience that allows sound delay differences between the two channels to be used to generate surround and rear channel information. This was used in quadraphonic systems that appeared in the 1970s. These were replaced with systems such as Dolby Surround ProLogic (I or II); for best performance, from separate multiple channel information carried in consumer digital audio systems such as DTS or Dolby AC-3 (5.1 version in DVDs, USA ATSC and optional on Australian HD) or MPEG-2 (AAC 5.1 and 7.1 channel versions on Japanese DTV). Studio VTR recording of 5.1 channels, which may be done on 2 AES/EBU digital channel pairs using Dolby-E format. 480i: Type of standard digital television (SDTV) image that is 480 lines by 720 pixels wide, displayed in interlaced format. (It has a 4:3 or 16:9 aspect ratio, 29.97-Hz frame rate, as defined by the ATSC standard.) 480p: High-definition television (HDTV) image that is 480 vertical lines by 720 horizontal pixels displayed in progressive format (It has a 4:3 or 16:9 aspect ratio, 59.94 Hz, 29.97 Hz, and 23.98 Hz frame rates, as defined by the ATSC standard.) 720p: Type of high-definition television (HDTV) image that is 720 vertical lines by 1,280 horizontal pixels wide, displayed in progressive format. (It has a 16:9 aspect ratio, 59.94 Hz, 29.97 Hz, and 23.98 Hz frame rates, as defined by the ATSC standard.) 1080i: Type of high-definition television (HDTV) image that is 1,080 vertical lines by 1,920 horizontal pixels wide, displayed in an interlaced format. (It has a 16:9 aspect ratio, 29.97 Hz frame rate, as defined by the Advanced Television Systems Committee (ATSC) standard.) 1394: The standard for a digital connection or bus used to transfer data between two independent systems. The 1394a standard provides 400-Mbps bandwidth and the reach is limited to 3 or 4 meters. The 1394b standard extends the bandwidth to 800 Mbps and the reach to a whole-house environment. 8 bits: A measure of memory. 8 bits make up 1 byte, and offer 256 (2^8) different combinations 8-VSB: Eight Discrete Amplitude Level Vestigial side-Band broadcast transmission technologies, used in the ATSC digital television transmission standard. The VSB modulator receives the 10.76 Msymbols/s, 8-level trellis encoded composite data signal (pilot and sync added). The ATV system performance is based on a linear3

phase raised cosine Nyquist filter response in the concatenated transmitter and receiver, as shown in Figure 12.

The system filter response is essentially flat across the entire band, except for the transition regions at each end of the band. Nominally, the rolloff in the transmitter shall have the response of a linear phase root raised cosine filter. 10Base2: A type of Ethernet cable that has been largely phased out. It's also known as "thinnet." Cable speeds are typically up to 10Mbps. 10Base2 uses RG-58 coaxial cable in a bus topology configuration with a maximum cable length of 185 meters. 10Base2 was used for desktop machines, while 10Base5 was used mainly for backbones. 10Base5: The original Ethernet specification, which is now more uncommon than 10Base2. It's also known as "thicknet." Cable speeds are typically up to 10Mbps. 10Base5 uses RG-11 coaxial cable in a bus topology configuration and has a maximum cable length of 500 meters, thus the 10(Mbps)Base5(00) name. 10BaseT: A type of Ethernet cable topology that uses RJ-45 connectors, twisted pair wiring, and a star topology. Transmission speed is 10Mbps. 100Base-T (Faster Ethernet): A networking standard that supports data transfer rates up to 100 Mbps (100 megabits per second). 100BASE-T is based on the older Ethernet standard. Because it is 10 times faster than Ethernet, it is often referred to as Fast Ethernet. Officially, the 100BASE-T standard is IEEE 802.3u. Like Ethernet, 100BASE-T is based on the CSMA/CD LAN access method. There are several different cabling schemes that can be used with 100BASE-T, including: 100BASE-TX: two pairs of high-quality twisted-pair wires 100BASE-T4: four pairs of normal-quality twisted-pair wires 100BASE-FX: fiber optic CABLES4

1000Base-T (Gigabit Ethernet): An extension of 100BaseT that runs 10 times faster than 100BaseT. It's theoretically capable of 1Gbps (1000Mbps) transmission speed, and requires Category 6 cables to run over copper wire. Gigabit Ethernet can run over fiber-optic cabling as well. 16-bit Operating Systems: DOS and Windows 3.x are 16-bit operating systems. They are limited in complexity and suffer instability and slow speed (compared to 32-bit OSes) when run on 32-bit processors like the 386DX-compatible chips and above. 16-bit chips were limited to 65,536 (2^16) Kbytes of memory, or 64 MB. This limitation caused momentum for the move to 32-bit chips and operating systems. 32-bit Operating Systems: Windows NT, OS/2, and some flavors of UNIX are 32-bit operating systems. Windows 95 is a 32-bit operating system running on top of a 16-bit operating system (DOS). 32-bit color depth: Anything that supports 32-bit color supports over four billion different colors (2^32, or 4,294,967,296 to be exact). Graphics cards are supporting up to and over 32-bit color, but the human eye cannot discern between colors at that level, and you need more memory on your graphics card to display 32-bit color at high resolutions. Color scanners, however, use 32-bit or higher color depth. This is a more accurate scan, even though the color difference between two pixels may not be perceptible. 32-bit processor (32-bit Chips) : This type of processor can run a 32-bit OS, such as Windows NT or some versions of UNIX. You can also run a 16-bit or lesser OS, but performance is not optimal. Intel's 386DX, 486, Pentium, and Pentium II/III/4 are all 32-bit processors. So are AMD's 386, 486, Athlon, and Duron. 32-bit processors can address up to 4 GB of memory. Although this may be plenty for a typical desktop machine, higher end servers, workstations, and desktops require more memory and use 64-bit processors. 48-bit color depth - Some scanners support 48-bit color, which offers the ability to identify over 281 trillion (2^48) colors. Such color differences may be imperceptible to the human eye, but as scanner DPI levels increase it helps keep colors more accurate. 64-bit Operating Systems - An operating system that is programmed to run on 64-bit processors. Some flavors of UNIX--and now Linux--are 64-bit operating5

systems designed to run on 64-bit chips. There are also preliminary versions of Microsoft Windows that are 64 bits so that they can run on 64-bit processors. 64-bit processor (64-bit Chips) - A processor that can run a 64-bit OS. The DEC Alpha is 64-bit, and so are Intel's Itanium and AMD's Opteron and Athlon 64 processors. The 386, 486, and Pentium and Pentium II/III/4 are all 32-bit processors, even though the Pentium and newer chips have 64-bit memory buses. 128-bit Operating Systems: Operating systems may eventually be 128-bit. The ability to address 128 bits of memory space is something that may someday be necessary for huge databases, and will speed up operations. Of course, this will not happen until after there are some 128-bit chips to run them on. So far there are some chips with 128-bit registers and special operations, but they are not fully 128-bit. 128-bit Video: The bits referred to here describe the bus between the GPU and the video memory. Typically, larger buses mean faster video, but it also depends on the transmission speed over that bus. The first 128-bit video cards had only 2 MB or 4 MB of video memory on them. 3D (3-dimensional): The representation of objects in a space by length, width, and height (three planes). On a computer display device, 3D objects are typically represented on the 2D surface of a flat screen, but are computed as if they were actually in a three-dimensional environment. Advances in 3D technology are making gaming and other 3D environments more realistic.

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-AAAC (Advanced Audio Coding): Originally specified in Part 7 of MPEG-2, AAC is an improved audio compression system. Used in Japanese ISDB, U.S. XM Satellite radio and Radio Mondale (RDM) and used with MPEG-4 Advanced video coding. Recent demonstrations (such as at IBC 2002) have shown advances in this system now known as aacPlus with good quality stereo at 64kbps or less. AAC is the audio coding standard defined by the International Organization for Standardization (ISO) as part of the MPEG-2 specification. Declared an international standard in April 1997, MPEG-2 AAC builds upon and extends the popular ISO/MPEG-1 Audio Layer-3 (MP3) audio coding format. Compared to MP3, AAC provides higher quality music with approximately 30% storage space or bandwidth. AAC provides up to 48 audio channels and sample rates up to 96 kHz. AAL (ATM Adaptation Layer): One of three layers of the ATM (ASYNCHRONOUS TRANSFER MODE) protocol reference model. It performs segmentation and reassembly (SAR), translates higher-layer data into ATMcell payloads, and translates incoming cells into a format readable by the higher layers. AAL-0 (ATMAdaptation Layer type 0): AAL0 cells are sometimes referred to as raw cells. The payload consists of 48 bytes and has no special meaning. AAL-1 (ATMAdaptation Layer type 1): AAL-1 relates to ATMservice class A where a time relation exists between the source and the destination, the bit rate is constant, and the service is connection-oriented(e.g., a voice channel). The structure of the AAL1 PDU is given in the following illustration: SN CSI SC CRC SNP EPC SAR PDU Payload 1 bit 47 bytes

1 bit

3 bits

3 bits

AAL1 PDU

AAL-2 (ATMAdaptation Layer type 2): relates to ATMservice class B; where a time relation exists between the source and the destination, the bit rate is variable, and the service is connection-oriented(e.g., a video or audio channel). AAL2 provides7

bandwidth-efficient transmission of low-rate, short and variable packets in delay sensitive applications. It supports VBR and CBR. AAL2 also provides for variable payload within cells and across cells. AAL type 2 is subdivided into the Common Part Sublayer (CPS ) and the Service Specific Convergence Sublayer (SSCS ). AAL-3 (ATMAdaptation Layer type 3): relates to ATMservice class C; where no time relation exists between the source and the destination, the bit rate is variable, and the service is connection-oriented(e.g., a connection-oriented file transfer). AAL-4 (ATMAdaptation Layer type 4): relates to ATMservice class D; where no time relation exists between the source and the destination, the bit rate is variable, and the service is connectionless(e.g., LAN interconnection and electronic mail). AAL-3/4 (ATMAdaptation Layer type 3/4): since the differences between AAL-3 and AAL-4 were minor, the ITUmerged them into a single type called AAL-3/4. ABR (Available Bit Rate): QoS class defined by the ATM Forum for ATM networks. ABR is used for connections that do not require timing relationships between source and destination. ABR provides no guarantees in terms of cell loss or delay, providing only best-effort service. Traffic sources adjust their transmission rate in response to information they receive describing the status of the network and its capability to successfully deliver data. Compare with CBR, UBR, and VBR Absolute Threshold of Hearing (ATH): The Threshold of hearing is the Sound pressure level SPL of 20 Pa (micropascals) = 2 10-5 pascal (Pa). This low threshold of amplitude (strength or sound pressure level) is frequency dependent. See Fig. 2. The absolute threshold of hearing (ATH) is the minimum amplitude (level or strength) of a pure tone that the ear can hear in a noiseless environment. The threshold of pain is the SPL beyond which sound becomes unbearable for a human listener. This threshold varies only slightly with frequency. Prolonged exposure to sound pressure levels in excess of the threshold of pain can cause physical damage, potentially leading to hearing impairment. Different values for the threshold of pain Fig 1: Flecher-Munson equal loudness contours(The lowest of the curve is the ATH)

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The Threshold of hearing is frequency dependent, and typically shows a minimum (indicating the ear's maximum sensitivity) at frequencies between 1 kHz and 5 kHz. A typical ATH curve is pictured in Fig. 1. The absolute threshold of hearing represents the lowest curve amongst the set of equal-loudness contours, with the highest curve representing the threshold of Threshold of pain pain.120 dBSPL 130 dBSPL 134 dBSPL 137.5 dBSPL 140 dBSPL

In psychoacoustic audio compression, the ATH is used, often in combination with masking curves, to calculate which spectral components are inaudible and may thus be ignored in the coding process; any part of an audio spectrum which has an amplitude (level or strength) below the ATH may be removed from an audio signal without any audible change to the signal.20 Pa 63 Pa 100 Pa 150 Pa 200 Pa

SPL

Sound pressure

Fig. 2: Thresholds of hearing for male (M) and female (W) subjects between the ages of 20 and 60

The ATH curve rises with age as the human ear becomes more insensitive to sound, with the greatest changes occurring at frequencies higher than 2 kHz. Curves for subjects of various age groups are illustrated in Fig. 2. The data is from

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the United States Occupational Health and Environment Control, Standard Number:1910.95 App F AC Coefficient: Any DCT (Discrete Cosine Transform) coefficient for which the frequency in one or both dimensions is non-zero. Acceptance Angle: The half-angle of the cone (a) within which incident light is totally internally reflected by the fiber core. It is equal to sin-1(NA).

Access Unit: A coded representation of a presentation unit. In the case of audio, an access unit is the coded representation of an audio frame. In the case of video, an access unit includes all the coded data for a picture, and any stuffing that follows it, up to but not including the start of the next access unit. If a picture is not preceded by a group_start_code or a sequence_header_code, the access unit begins with the picture start code. If a picture is preceded by a group_start_code and/or a sequence_header_code, the access unit begins with the first byte of the first of these start codes. If it is the last picture preceding a sequence_end_code in the bitstream, all bytes between the last byte of the coded picture and the sequence_end_code (including the sequence_end_code) belong to the access unit. Alternating Current (AC): A type of electrical current that reverses its direction at a regular interval, and can be represented by a sine wave. Alternating current is the type of current typically found in a wall outlet. You plug your TV, computer, refrigerator, etc. into alternating current. These devices then change the alternating current into direct current (DC) so that they can use the current properly. Alternating current is the reason that we need such complex power supplies, or power bricks, to regulate the flow of current in electronic devices. AC-3: A proprietary digital sound system developed (and patented) by Dolby. Also known as Dolby Digital (www.dolby.com), it can carry multiple channels, including stereo (2.0) (decodable with ProLogic I or II) and 5.1 discrete channel. Extra data can be included to control the dialog levels ('dial-norm') and dynamic range to the listener's choice. Variants of the system are used in movie theatres, domestic laser disk and DVD and in the US ATSC and Australian DVB-T digital broadcast systems. Decode systems may include a second decoder for special requirements. ACK (Acknowledgment): A response from a server to a network request. Basically, the server is saying, "I'm here, and I saw your request!" This also refers to the 6th ASCII character.. Active Device: A device that requires a source of energy for its operation and has an output that is a function of present and past input signals. Examples include controlled power supplies, transistors, LEDs, amplifiers, and transmitters.10

ADC (A-D, A/D, A-to-D): Analog to Digital Conversion. Also referred to as digitization or quantization. The conversion of an analog signal into the digital data representation of that signal--normally for subsequent use in a digital machine. For TV, samples of audio and video are taken, the accuracy of the process depending on both the sampling frequency and the resolution of the analog amplitude information--how many bits are used to describe the analog levels. For TV pictures eight or 10-bits are normally used; for sound, 16 or 20-bits are common, and 24-bits are being introduced. The ITU-R 601 standard defines the sampling of video components based on 13.5 MHz, and AES/EBU defines sampling of 44.1 and 48 kHz for audio. For pictures, the samples are called pixels, each containing data for brightness and color. See also: Binary, Bit.

Add/Drop: The process where a part of the information carried in a transmission system is extracted (dropped) at an intermediate point and different information is inserted (added) for subsequent transmission. The remaining traffic passes straight through the multiplexer without additional processing. ADM: Add-Drop-Multiplexer. This is one of SONET's claim to fame. The tributaries of a SONET transport stream, are synchronously multiplexed to the line rate, i.e. there are no stuff bits or stuff opportunity bits as is the case in the plesiochronous hierarchy. As such an ADM can insert or extract lower rate tributary data without demultiplexing the aggregate line rate.

Address: Data structure or logical convention used to identify a unique entity, such as a particular process or network device. Address Mapping: Technique that allows different protocols to interoperate by translating addresses from one format to another. For example, when routing IP over X.25, the IP addresses must be mapped to the X.25 addresses so that the IP packets can be transmitted by the X.25 network. See also address resolution. Address Mask: Bit combination used to describe which portion of an address refers to the network or subnet and which part refers to the host. Sometimes referred to simply as mask. See also subnet mask.

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Address Resolution: Generally, a method for resolving differences between computer addressing schemes. Address resolution usually specifies a method for mapping network layer (Layer 3) addresses to data-link control layer (Layer 2) addresses. See also address mapping . ADSL (Asymmetric Digital Subscriber Line) - A technology that is the phone company's answer to cable modems. It supports data speeds over 7Mbps downstream (to the user) and slower speeds upstream (to the Internet). Asymmetric describes how the upstream speed is different than the downstream speed. Administrative Unit (AU): An Administrative Unit is the information structure which provides adaptation between the Higher-Order path layer and the Multiplex Section layer. The Virtual Container (VC) plus the pointers (H1, H2, H3 bytes) is called the Administrative Unit (AU). AES/EBU: Audio Engineering Society / European Broadcast Union is a digital audio standard commonly used in linking professional digital audio equipment. The AES/EBU digital interface is usually implemented using 3-pin XLR connectors, the same type connector used in a professional microphone. One cable carries both right and left channels. AES/EBU is an alternative to the S/PDIF standard. Informal name for a digital audio standard established jointly by the AES and EBU organizations. The sampling frequencies for this standard vary depending on the format being used; the sampling frequency for D1 and D2 audio tracks is 48 kHz. Audio Engineering Society that promotes standards in the professional audio industry. International Headquarters--60 East 42nd Street, Room 2520, New York, New York 10165-2520. Tel: 212-661-8528. Fax: 212-682-0477. Email: HQ@aes.org. Internet: www.aes.org. AGC (Automatic Gain Control): A process or means by which gain is automatically adjusted in a specified manner as a function of input level or another specified parameter.

Agent: (1) Generally, software that processes queries and returns replies on behalf of an application. 2) In NMSs, process that resides in all managed devices and reports the values of specified variables to management stations. AIF (Audio Interchange File): An audio file format developed by Apple Computer to store high quality sampled sound and musical instrument information. The AIF files are a popular format for transferring between the Macintosh and the PC. AIS (Alarm Indication Signal): (1) A code sent downstream indicating an upstream failure has occurred. (2) In a T1 transmission, an all-ones signal12

transmitted in lieu of the normal signal to maintain transmission continuity and to indicate to the receiving terminal that there is a transmission fault that is located either at, or upstream from, the transmitting terminal. Aliasing: Defects or distortion in a television picture or audio. Defects are typically seen as jagged edges on diagonal lines and twinkling or brightening. In digital video, aliasing is caused by insufficient sampling or poor filtering of the digital video. a-law: ITU-T companding standard used in the conversion between analog and digital signals in PCM systems. A-law is used primarily in European telephone networks and is similar to the North American mu-law standard. See also (mu)-law. ALiS: ALiS (Alternate Lighting of Surfaces) is a relatively recent type of high-definition plasma panel designed for optimum performance when displaying 1080i material. On a conventional plasma TV, all pixels are illuminated at all times. With an ALiS plasma panel, alternate rows of pixels are illuminated so that half the panel's pixels are illuminated at any moment (somewhat similar to interlaced-scanning on a CRT-type TV). ALiS panels offer bright, clear picture quality, reduced power consumption, and extended panel life. Algorithm: A formula or set of steps used to simplify, modify, or predict data. Complex algorithms are used to selectively reduce the high digital audio and video data rates. These algorithms utilize physiologists' knowledge of hearing and eyesight. For example, we can resolve fine detail in a still scene, but our eye cannot resolve the same detail in a moving scene. Using knowledge of these limitations, algorithms are formulated to selectively reduce the data rate without affecting the viewing experience. See also: Compression, MPEG. Alpha Channel: A relative transparency value. Alpha values facilitate the layering of media object on top of each other. In a four digit digital sampling structure (4:2:2:4) the alpha channel is represented by the last digit. AMI (Alternate Mark Inversion): The line-coding format in transmission systems where successive ones (marks) are alternatively inverted (sent with polarity opposite that of the preceding mark).

Amplifier: A device, inserted within a transmission path that boosts the strength of an electronic or optical signal. Amplifiers may be placed just after the transmitter (power booster), at a distance between the transmitter and the receiver (in-line amplifier), or just before the receiver (preamplifier).13

Amplitude Modulation (AM): A means of transmitting and receiving radio waves that is based on variances in the amplitude of the radio waves. See also FM. Amplified Spontaneous Emission (ASE): A background noise mechanism common to all types of erbium-doped fiber amplifiers (EDFAs). It contributes to the noise figure of the EDFA which causes loss of signal-to-noise ratio (SNR).

Analog: 1. An adjective describing any signal that varies continuously as opposed to a digital signal, which contains discrete levels. 2. A system or device that operates primarily on analog signals. Anamorphic Video: Video images that have been "squeezed" to fit a video frame when stored on DVD. These images must be expanded (un-squeezed) by the display device. An increasing number of TVs employ either a screen with 16:9 aspect ratio, or some type of "enhanced-for-widescreen" viewing mode, so that anamorphic and other widescreen material can be viewed in its proper proportions. When anamorphic video is displayed on a typical TV with 4:3 screen size, the images will appear unnaturally tall and narrow. Angular Misalignment: Loss at a connector due to fiber end face angles being misaligned.

ANSI (American National Standards Institute): A US standards body. This organization represents the United States in the International Organization for Standardization (ISO). It works to develop coding and signaling standards. http://www.ansi.org/ Anti-Aliasing: The smoothing and removing of aliasing effects by filtering and other techniques. Most, but not all, DVEs and character generators contain anti-aliasing facilities. A method used to better define higher resolution objects in lower resolution. For example, you would use anti-aliasing if you have two lines that are so close together that at 320x200 they look as if they are one double-width line and you want to represent them better. This is most noticeable when dealing with curves, such as circles. For example, if you look at a circle drawn in a simple paint program at a low resolution, you can see the "steps," or "jaggies"--the points14

it takes to make the circle. If you raise the resolution you'll notice the "steps" much less. If you use anti-aliasing, different shades of the circle's color are used to "fill in" the gaps caused by low resolution, smoothing out its appearance to the user. Typical uses for anti-aliasing are for smoothing out fonts and straight lines in 3D images. If you are using a system with jagged-looking fonts, chances are that it's not anti-aliasing the fonts. Anti-Alias Filter: A low pass filter used to bandwidth-limit a signal to less than one-half the sampling rate. APC: Abbreviation for Angled Physical Contact. A style of fiber optic connector with a 5-15 angle on the connector tip for the minimum possible backreflection.

Applet: A derivation of "application." You use the Applet tag in HTML code to define calls to Java-based applications within a browser. Thus, any Java program accessible through a Java-enabled browser can be referred to as an applet or Java Applet. Application Layer: Layer 7 of the OSI reference model . This layer provides services to application processes (such as e-mail, file transfer, and terminal emulation) that are outside of the OSI model. The application layer identifies and establishes the availability of intended communication partners (and the resources required to connect with them), synchronizes cooperating applications, and establishes agreement on procedures for error recovery and control of data integrity. Corresponds roughly with the transaction services layer in the SNA model. See also data-link layer, network layer, physical layer, PQ, session layer, and transport layer. Application Programming Interface (API): APIs allow you to program to a pre-constructed interface (the API) instead of programming a device or piece of software directly. This allows for faster development, since programming to a device's API is designed to be easier than programming to a device directly. APIs allow you to program without having intimate knowledge of the device or software to which you are sending commands. For example, the OpenGL API allows you to create 3D effects without actually knowing the innards of your video card. Application Information Table (AIT): Part of a DVB/MPEG transport stream that provides information about MHP applications associated with a particular service. For each application this information includes - The application type (e.g. DVB-J application or plug-in application); An application identifier that uniquely identifies the application; An application control code that controls the lifecycle of the application; The last of these entries says that the lifecycle can be controlled by the information sent in the AIT. When the user selects a service, the control codes in15

the AIT are read. The AIT for a specific service is sent at frequent intervals and the application control flag can be updated between AIT versions. In this way the service provider can control the applications in the service; e.g. a news application is set to be AUTOSTART at the time when the 6:00pm news begins. Application Service Provider (ASP): A company that provides remote access to applications, typically over the Internet. ASPs are used when an organization finds it more cost effective to have someone else host its applications than to host them itself. The applications served up can be as simple as access to a remote fileserver, or as complex as running an order entry system through your browser. The ASP provides the servers, network access, and applications to be used, typically for a monthly or yearly subscription fee. APS (Automatic Protection Switching): A 1+1 protection switch architecture is one in which the head end signal is permanently bridged (at the electrical level) to service and protection equipment to enable the same payload to be transmitted identically to the tail end service and protection equipment. At the tail end , each service and protection optical signal is monitored independently and identically for failures. The receiving equipment selects either the service or protection channel based upon the switching criteria. Architecture: The specifications of a system and how its subcomponents interconnect, interact and cooperate. Architectures are often described in multiple levels of abstraction from low-level physical to higher-level logical application and end-user views. Archive: As a noun, this refers generally to any type of backed-up data. It can refer to tapes, disks, or just simply a group of data that is an old copy of current data. That copy could be one minute old or several years old. As a verb, archive is the act of backing up data or creating an archive. Off-line storage of video/audio onto backup tapes, floppy disks, optical disks, etc. AR Coating: Antireflection coating. A thin, dielectric or metallic film applied to an optical surface to reduce its reflectance and thereby increase its transmittance. Argument: What you have with your girlfriend when she wants you to stop using your computer so much. Actually, argument refers to the value with which you call a procedure. For example, if you wrote a line of code that said "goto 140" telling your program to go to line 140, the argument is "140." Some procedures will accept multiple arguments, or alternately, require no arguments. Arithmetic Logic Unit (ALU): The part of the CPU that actually does the work of adding, subtracting, multiplying, and dividing, including OR, AND, and NOT operations. The ALU is an execution unit, like the FPU, that is fed with data from the CPU registers. ARPANet (Advanced Research Projects Agency Network): A network of interconnected computers that formed the original Internet. The United States military funded the ARPANet, and construction was started in 1968. It was

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designed to be a redundant network of computers so that no single disruption could break down communications between other units. The ARPANet expanded to universities for research, and soon after the Internet was born. Artifacts: Undesirable elements or defects in a video picture. These may occur naturally in the video process and must be eliminated in order to achieve a high-quality picture. Most common in analog are cross color and cross luminance. Most common in digital are macroblocks, which resemble pixelation of the video image. ASCII (American Standard Code for Information Interchange): A standard code for transmitting data, consisting of 128 letters, numerals, symbols, and special codes each of which is represented by a unique binary number. This is a standard means of representing characters, consisting of 256 characters. The first 128 characters are standardized, and the first 32 of those are control codes, which don't really represent visible characters but rather codes that can be used for text formatting or actions, such as making the computer beep or clearing the screen. After the 32 control codes, the next 96 standardized characters represent numbers, letters (both uppercase and lowercase), and standard punctuation marks. The last 128 characters represent different things on different platforms. ASCII is being largely supplanted by Unicode. ASIC (Application specific integrated circuit): An integrated circuit designed for special rather than general applications. Aspect Ratio: The aspect ratio of an image is its displayed width divided by its height (usually expressed as "x:y"). For instance, the aspect ratio of a traditional television screen is 4:3, or 1.33:1. High definition television uses an aspect of 16:9, or about 1.78:1. Aspect ratios of 2.39:1 or 1.85:1 are frequently used in cinematography, while the aspect ratio of a full 35 mm film frame with soundtrack (also known as "Academy standard") is around 1.37:1.

Comparison of three common aspect ratios. The outer box (blue) and middle box (red) are common formats for cinematography. The inner box (green) is the format used in standard television. The 4:3 ratio for standard television has been in use since television's origins and many computer monitors use the same aspect ratio. Since 4:3 is close to the old 1.37:1 cinema academy format, theaters suffered from a loss of viewers after films were broadcast on TV. To prevent this, Hollywood created widescreen aspect17

ratios to immerse the viewer in a more realistic experience and, possibly, to make broadcast films less enjoyable if watched on a regular TV set. 16:9 is the format of Japanese and American HDTV as well as European non-HD widescreen television (EDTV). Many digital video cameras have the capability to record in 16:9. Anamorphic DVD transfers store the information in 16:9 vertically squeezed to 4:3; if the TV can handle an anamorphic image the signal will be de-anamorphosed by the TV to 16:9. If not, the DVD player will unsqueeze the image and add letterboxing before sending the image to the TV. Wider ratios such as 1.85:1 and 2.39:1 are accommodated within the 16:9 DVD frame by adding some additional masking within the image itself. Within the motion picture industry, the convention is to assign a value of 1 to the image height, so that, for example, an anamorphic frame is described as 2.39:1 or just "2.39". This way of speaking comes about because the width of a film image is restricted by the presence of sprocket holes and a standard intermittent movement interval of 4 perforations, as well as an optical soundtrack running down the projection print between the image and the perforations on one side. The most common projection ratios in American theaters are 1.85 and 2.39. The 16:9 format adopted for HDTV is actually narrower than commonly-used cinematic widescreen formats. Anamorphic widescreen (2.39:1) and American theatrical standard (1.85:1) have wider aspect ratios, while the European theatrical standard (1.66:1) is just slightly less. (IMAX, contrary to some popular perception, is 1.33:1, the traditional television aspect ratio.) Super 16mm film is frequently used for television production due to its lower cost, lack of need for soundtrack space on the film itself, and aspect ratio similar to 16:9 (Super 16mm is natively 1.66 whilst 16:9 is 1.78). The term is also used in the context of computer graphics to describe the shape of an individual pixel in a digitized image. Most digital imaging systems use square pixelsthat is, they sample an image at the same resolution horizontally and vertically. But there are some devices that do not, so a digital image scanned at twice the horizontal resolution to its vertical resolution might be described as being sampled at a 2:1 aspect ratio, regardless of the size or shape of the image as a whole.

Assembly Language: A programming language specific to a microprocessor. It is a very low-level language, where you actually give the processor instructions like "MOV A,B", which moves a value from one register to another. As you might imagine, programming directly in assembly language is quite tedious. Thus, higher

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level languages, such as C++, Visual Basic, or Java, are normally used and then compiled into assembly language specific to the microprocessor on which the program will be run. The compiler tries to optimize the code during this process (e.g., "MOV A,B" followed by "MOV B,C" might be replaced by "MOV A,C"). Depending on how elegant the optimization is, the code may run faster than if no optimization is used. Today, very small and fast programs can be created by using assembly language (defeating code bloat), but assembly language programming is becoming a dying art. Asymmetric communications: Two-way communications in which the volumes of traffic in each direction are significantly different. For example, TV on demand. Asynchronous: Lacking synchronization. In video, a signal is asynchronous when its timing differs from that of the system reference signal. A foreign video signal is asynchronous before it is treated by a local frame synchronizer.

Asynchronous Mapping - These mappings are defined for clear channel transport of digital signals that meet the standard DSX cross connect requirements, typically DSX-1 and DSX-3 in most practical applications. At the asynchronous mapping interface, frame acquisition and generation is not required. For example if your system can transport a BERT (bit error test set) signal with a 10^23-1 test pattern, it is being asynchronously mapped for transport. Asynchronous Serial Interface (ASI): Commonly used for carrying (MPEG) compressed program (video, audio, etc.) as packet data on conventional digital TV studio 270Mb/s distribution and routing systems designed for uncompressed video per Rec ITU-R BT.601 and 656. The MPEG data stream payload can typically be equivalent to only several Megabit/sec up to say 34Mb/s. To be compatible to 270Mb/s equipment, the data is clocked at 270Mb/s, which bunches up the data and leaves intervening periods with no data (bursty mode). Normally these gaps are filled with coded filler (ASI stuffing bytes) to present a continuous stream. Refer byte gap & gap size: Number of 10-bit, K28.5 special character commas inserted between bytes within transport stream packets in the ASI transmission protocol. Special character commas are used as stuffing data to spread out transport stream packets in time. Refer to DVB Blue Book Implementation Guidelines for the Asynchronous Serial Interface DVB Document A055 May 2000; and, ETSI TR 101 891 V1.1.1 (2001-02) ; Professional Interfaces: Guidelines for the implementation and usage

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of the DVB Asynchronous Serial Interface (ASI). ATM (Asynchronous Transfer Mode): The Asynchronous Transfer Mode (ATM) is a multiplexing technique that makes optimal and flexible use of the bandwidth of modern transmission links. ATM should not be confused with PDH or SDH transmission techniques. Asynchronous Transfer Mode ATM defines how the available bandwidth of a transmission medium is used. It is a statistical time division multiplex method. Its essential features are:

Packets (cells) of constant length (53 bytes) Cells comprising a 5-byte header and a 48-byte payload

Fig: An ATM Cell Consists of a Header and Payload Data

No error control for user data Supports virtually all PDH and SDH tributary bit rates (from 1.5 Mbit/s) Based on SDH networks for public use, otherwise also cell based Suitable for all useful signals (video, voice, data) and transmission modes (connection-oriented, connectionless, constant bit rate, burst mode, variable bit rate)

Quality of Service (QoS) is one of the main features of ATM (Asynchronous Transfer Mode). Apart from variable bandwidth utilization, the customer (user) can, for the first time, order and pays only for the quality he really needs for his telecommunication service. Only ATM can handle QoS in such a flexible and comprehensive way. In addition, work is in progress to extend the IP protocol to include QoS aspects for LAN applications (RSVP, Resource Reservation Protocol, IP V6 (next IP version)). When purchasing ATM service, you generally have a choice of four different types of service: Constant Bit Rate (CBR): specifies a fixed bit rate so that data is sent in a steady stream. This is analogous to a leased line. Variable Bit Rate (VBR): provides a specified throughput capacity but data is not sent evenly. This is a popular choice for voice and videoconferencing data. Available Bit Rate (ABR): provides a guaranteed minimum capacity but allows data to be bursted at higher capacities when the network is free. Unspecified Bit Rate (UBR): does not guarantee any throughput levels.20

This is used for applications, such as file transfer, that can tolerate delays. A data transmission scheme using self-routing packets of 53 bytes, 48 of which are available for user data. Typically 25, 155, and 622 Mbps--the latter of which could be used to carry non-compressed ITU-R 601 video as a data file. SDH is the optical transport layer in wide area networks. This layer makes use of containers, which allows the highly flexible and secure transmission of any kind of telecommunication signal. SDH technology is the successor to PDH technology. Before SDH (synchronous digital hierarchy) was standardized and introduced, PDH (plesiochronous digital hierarchy), which is still being used, was state of the art. ATM Cell Header Format: An ATM cell header can be one of two formats: UNI (User-Network-Interface) or NNI (Network-Network-Interface). The UNI header is used for communication between ATM endpoints and ATM switches in private ATM networks. The NNI header is used for communication between ATM switches. Figure below depicts the basic ATM cell format, the ATM UNI cell header format, and the ATM NNI cell header format.

Fig: An ATM Cell, ATM UNI Cell, and ATM NNI Cell Header Each Contain 48 Bytes of Payload

Unlike the UNI, the NNI header does not include the Generic Flow Control (GFC) field. Additionally, the NNI header has a Virtual Path Identifier (VPI) field that occupies the first 12 bits, allowing for larger trunks between public ATM switches. ATM Network Interfaces: An ATM network consists of a set of ATM switches interconnected by point-to-point ATM links or interfaces. ATM switches support two primary types of interfaces: UNI and NNI. The UNI connects ATM end systems (such as hosts and routers) to an ATM switch. The NNI connects two ATM switches. Depending on whether the switch is owned and located at the customers premises or is publicly owned and operated by the telephone company, UNI and NNI can be further subdivided into public and private UNIs and NNIs. A private UNI connects an ATM endpoint and a private ATM switch. Its public counterpart connects an ATM endpoint or private switch to a public switch. A private NNI connects two ATM switches within the same private organization. A public one connects two21

ATM switches within the same public organization. An additional specification, the broadband intercarrier interface (B-ICI), connects two public switches from different service providers. Figure 27-4 illustrates the ATM interface specifications for private and public networks.

ATM Interface Specifications Differ for Private and Public Networks

ATSC (Advanced Television Systems Committee): Formed to establish technical standards for advanced television systems, including digital high definition television (HDTV). 1750 K Street NW, Suite 800, Washington, DC 20006. Tel: 202-828-3130. Fax: 202-828-3131. Email: atsc@atsc.org. Internet: www.atsc.org. The digital television (DTV) standard has ushered in a new era in television broadcasting. The impact of DTV is more significant than simply moving from an analog system to a digital system. Rather, DTV permits a level of flexibility wholly unattainable with analog broadcasting. An important element of this flexibility is the ability to expand system functions by building upon the technical foundations specified in ATSC standards such as the ATSC Digital Television Standard (A/53) and the Digital Audio Compression (AC-3) Standard (A/52). With NTSC, and its PAL and SECAM counterparts, the video, audio, and some limited data information are conveyed by modulating an RF carrier in such a way that a receiver of relatively simple design can decode and reassemble the various elements of the signal to produce a program consisting of video and audio, and perhaps related data (e.g., closed captioning). As such, a complete program is transmitted by the broadcaster that is essentially in finished form. In the DTV system, however, additional levels of processing are required after the receiver demodulates the RF signal. The receiver processes the digital bit stream extracted from the received signal to yield a collection of program elements (video, audio, and/or data) that match the service(s) that the consumer selected. This selection is made using system and service information that is also transmitted. Audio and video are delivered in digitally compressed form and must be decoded for presentation. Audio may be monophonic, stereo, or multi-channel. Data may supplement the main video/audio program (e.g., closed captioning, descriptive text, or commentary) or it may be a stand-alone service (e.g., a stock or news ticker). The nature of the DTV system is such that it is possible to provide new features

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that build upon the infrastructure within the broadcast plant and the receiver. One of the major enabling developments of digital television, in fact, is the integration of significant processing power in the receiving device itself. Historically, in the design of any broadcast systembe it radio or televisionthe goal has always been to concentrate technical sophistication (when needed) at the transmission end and thereby facilitate simpler receivers. Because there are far more receivers than transmitters, this approach has obvious business advantages. While this trend continues to be true, the complexity of the transmitted bit stream and compression of the audio and video components require a significant amount of processing power in the receiver, which is practical because of the enormous advancements made in computing technology. Once a receiver reaches a certain level of sophistication (and market success) additional processing power is essentially free. The Digital Television Standard describes a system designed to transmit high quality video and audio and ancillary data over a single 6 MHz channel. The system can deliver about 19 Mbps in a 6 MHz terrestrial broadcasting channel and about 38 Mbps in a 6 MHz cable television channel. This means that encoding HD video essence at 1.106 Gbps1 (highest rate progressive input) or 1.244 Gbps2 (highest rate interlaced picture input) requires a bit rate reduction by about a factor of 50 (when the overhead numbers are added, the rates become closer). To achieve this bit rate reduction, the system is designed to be efficient in utilizing available channel capacity by exploiting complex video and audio compression technology. The compression scheme optimizes the throughput of the transmission channel by representing the video, audio, and data sources with as few bits as possible while preserving the level of quality required for the given application. The RF/transmission subsystems described in the Digital Television Standard are designed specifically for terrestrial and cable applications. The structure is such that the video, audio, and service multiplex/transport subsystems are useful in other applications.

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Figure 1 Block diagram of functionality in a transmitter/receiver pair. RF Transmission refers to channel coding and modulation. The channel coder takes the digital bit stream and adds additional information that can be used by the receiver to reconstruct the data from the received signal which, due to transmission impairments, may not accurately represent the transmitted signal. The modulation (or physical layer) uses the digital bit stream information to modulate a carrier for the transmitted signal. The modulation subsystem offers two modes: an 8-VSB mode and a 16-VSB mode. ATSC Formats are 18 voluntary video formats shown in the following table.

The U.S. digital television transmission standard using MPEG-2 compression and the audio surround-sound compressed with Dolby Digital (AC-3). So that a wide

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variety of source material, including that from computers, can be best accommodated, two line standards are included--each operating at 24, 30, and 60 Hz. Note that 1,088 lines are actually coded in order to satisfy the MPEG-2 requirement that the coded vertical size be a multiple of 16 (progressive scan) or 32 (interlaced scan). See the lists of related specifications number attached here. Attached: A physical channel of a digital picture manipulator is attached to a logical channel of a controller if the physical channel is successfully acquired by the controller. A physical channel may be attached to only one logical channel of one controller at a time. Attenuation: 1) The decrease in signal strength along a fiber optic waveguide caused by absorption and scattering. Fiber optic attenuation is caused by transparency of the fiber, bending the fiber at too small of a radius, nicks in the fiber, splices, poor fiber terminals, FOTs, etc. Attenuation is usually expressed in dB/km.

2) A loss of signal strength in an electrical or radio signal usually related to the distance the signal must travel. Electrical attenuation is caused by the resistance of the conductor; poor (corroded) connections, poor shielding, induction, RFI, etc. 3) Radio signal attenuation may be due to atmospheric conditions, sun spots, antenna design / positioning, obstacles, etc. Attenuator: 1) In electrical systems, a usually passive network for reducing the amplitude of a signal without appreciably distorting the waveform. 2) In optical systems, a passive device for reducing the amplitude of a signal without appreciably distorting the ATV (Advanced Television): Digital television, including standard, enhanced and high-definition versions. Refer to ATSC. AU (also SND): Interchangeable audio file formats used in the Sun Sparcstation, Nest and Silicon Graphics (SGI) computers. Essentially a raw audio data format proceeded by an identifying header. The .au file is cross-platform compatible. Auditory Masking: A phenomenon that occurs when two sounds of similar frequencies occur at the same time. Because of auditory masking, the louder sound drowns out the softer sound and makes it inaudible to the human ear. Autotiming: Capability of some digital video equipment to automatically adjust input video timing to match a reference video input. Eliminates the need for manual timing adjustments.

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Authentication: A process of proving the identity of a computer or computer user. For users, it generally involves a user name and password. Computers usually pass a code that identifies that they are part of a network. Availability - The foundation for many Bellcore reliability criteria is an end to end two way availability of objective of 99.98% for interoffice applications (0.02% unavailability or 105 minutes/year down time). The objective for loop transport between the central office and the customer premises is 99.99%. For interoffice transport the objective refers to a two way broadband channel, e.g. SONET OC-N, over a 250 mile path. For loop applications the objective refers to a two way narrowband channel, e.g. DS0 or equivalent. Avalanche Photodiode (APD): A photodiode that exhibits internal amplification of photocurrent through avalanche multiplication of carriers in the junction region.

AVI: Audio video interleaving. The Microsoft Video for Windows file format for combining video and audio into a single block in time such as a 1/30th second video frame. In this file format, blocks of audio data are woven into a stream of video frames. ASF is intended to supersede AVI. AVO: Audiovisual object. In MPEG-4, audiovisual objects (also AV objects) are the individual media objects of a scene--such as video objects, images, and 3D objects. AVOs have a time dimension and a local coordinate system for manipulating the AVO are positioned in a scene by transforming the object's local coordinate system into a common, global scene coordinate system.

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AWGN (Additive White Gaussian Noise): In communications, the additive white Gaussian noise (AWGN) channel model is one in which the only impairment is the linear addition of wideband or white noise with a constant spectral density (expressed as watts per hertz of bandwidth) and a Gaussian distribution of amplitude. The model does not account for the phenomena of fading, frequency selectivity, interference, nonlinearity or dispersion. However, it produces simple, tractable mathematical models which are useful for gaining insight into the underlying behavior of a system before these other phenomena are considered. Wideband Gaussian noise comes from many natural sources, such as the thermal vibrations of atoms in antennas, "black body" radiation from the earth and other warm objects, and from celestial sources such as the sun. The AWGN channel is a good model for many satellite and deep space communication links. It is not a good model for most terrestrial links because of multipath, terrain blocking, interference, etc. Axis: Relating to digital picture manipulation, the X axis is a horizontal line across the center of the screen, the Y axis is a vertical line, and the Z axis is in the third dimension, perpendicular to the X and Y axes, and indicates depth and distance.

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-BBackbone: A segment of a network that's often a higher speed than the rest of the network and that connects all the other segments. If you don't have a backbone faster than the rest of your network your network could lag. That's why a lot of ISPs are constantly restructuring their backbones. Banner ad: The most common form of advertising found on the Web. The traditional size of a banner ad is 468 by 60 pixels, but there are many other sizes in general use. Banner ads are typically animated GIF graphics or Flash animations that are simply clicked on to go to the website of the advertiser, but can also contain rich media that allows for some degree of interaction with the ad besides a simple click. BASIC (Beginner's All-purpose Symbolic Instruction Code): This programming language was developed in the mid '60s. The language was constructed of simple, English-like commands that were run through an interpreter, line by line, each time the program was "run." This caused BASIC programs to be slow. Nowadays compilers have been developed to speed up BASIC programs, and recent versions of BASIC can do anything that other programming languages can. Back Channel: A means of communication from users to content providers. Examples include a connection between the central office and the end user, an Internet connection using a modem, or systems where content providers transmit interactive television (analog or digital) to users while users can connect through a back channel to a web site, for example.

Backup: A copy of the work created on a computer, stored in a safe place such as a floppy disc, CD-ROM or through a network on to another computer. Backward Compatibility: A newer coding standard is backward compatible with an older coding standard if decoders designed to operate with the older coding standard are able to continue to operate by decoding all or part of a bitstream produced according to the newer coding standard. Backward Motion Vector: A motion vector that is used for motion compensation from a reference frame or reference field at a later time in display order. Backward Prediction: Prediction from the future reference frame (field).

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Bandwidth: The complete range of frequencies over which a circuit or electronic system can function with minimal signal loss, typically less than 3 dB. 2. The information-carrying capability of a particular television channel. In PAL systems, the bandwidth limits the maximum visible frequency to 5.5 MHz, in NTSC, 4.2 MHz. The ITU-R 601 luminance channel sampling frequency of 13.5 MHz was chosen to permit faithful digital representation of the PAL and NTSC luminance bandwidths without aliasing. In transmission, the United States analog and digital television channel bandwidth is 6 MHz. BandwidthDistance Product: Of an optical fiber, under specified launching and cabling conditions, at a specified wavelength, a figure of merit equal to the product of the fibers length and the 3 dB bandwidth of the optical signal. The bandwidthdistance product is usually stated in megahertz kilometer (MHzkm) or gigahertzkilometer (GHzkm). It is a useful figure of merit for predicting the effective fiber bandwidth for other lengths, and for concatenated fibers. Barn Doors: A term used in television production to describe the effect that occurs when a 4:3 image is viewed on a 16:9 screen. When this happens, viewers see black bars on the sides of the screen or "barn doors." Baseband: A signaling technique in which the signal is transmitted in its original form and not changed by modulation. Local Area Networks as a whole, fall into two categories: baseband and broadband. Baseband networks are simpler and cheaper; the entire bandwidth of the LAN cable is used to transmit a single digital signal. In broadband networks, the capacity of the cable is divided into channels, which can transmit many simultaneous signals. Broadband networks may transmit a mixture of digital and analog signals, as will be the case in hybrid fiber/coax interactive cable television networks. Base Layer: First, independently decodable layer of a scalable hierarchy. Batch: A group of commands that are executed one at a time. Batch File: A file in a DOS/Windows environment with the .bat extension. This file type is executable in DOS or at a Windows command prompt. Batch programs are written in a batch programming language that utilizes a superset of standard DOS commands. Baud: A unit of signaling speed equal to the number of signal events per second. Baud is equivalent to bits per second in cases where each signal event represents exactly one bit. Often the term baud rate is used informally to mean baud, referring to the specified maximum rate of data transmission along an interconnection. Typically, the baud settings of two devices must match if the devices are to communicate with one another. BBS (Bulletin Board System): A bulletin board system used to describe message boards that people would dial into directly with modems before the Internet was easily accessible. Instead of dialing into a network where everything is connected, you had your choice of a group of BBSs to dial into, and each one tried to offer the

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most members, files, and graphics to its members. Typically you paid for access on a monthly basis. More recently, the term describes Internet-based message boards or forums. BCC (Blind Carbon Copy): When sending an e-mail, if you BCC someone you are sending him or her a copy of your e-mail, but not allowing the recipients in the "To" or "CC" fields of your e-mail client to know that the BCC recipient was sent the message as well. BCC is often used for covert company communications, such as if you are getting irritated at someone and want to let someone else in on it without alerting the party you are irritated about, or if you are sending the CEO of your company a mail telling him or her he or she is wrong about something and want to BCC copies to your friends to gloat over it. Use BCC with caution. One of the most common uses of BCC is when sending mass e-mails; just send the e-mail to yourself and BCC it to the whole group you are sending to. That way, your mailing list is not known to any of the members. BCD: Binary coded decimal. A coding system in which each decimal digit from 0 to 9 is represented by four binary (0 or 1) digits. BCH (Bose-Chaudhuri-Hocquenghem) Code: Co-authors of the so-named family of commonly-used linear block codes, a type of forward error correction (FEC). Beam: A portion of a satellite antenna's footprint on earth. A typical satellite footprint is divided into a large number of beams. Beam width: In an antenna, the angular sector in degrees of the radiated power pattern at the half-power (3dB) point. Bel (B): A measure of voltage, current, or power gain. One bel is defined as a tenfold increase in power. If an amplifier increases a signal's power by 10 times, its power gain is 1 bel or 10 decibels (dB). If power is increased by 100 times, the power gain is 2 bels or 20 decibels. 3 dB is considered a doubling. The logarithm to the base 10 of a power ratio, expressed as: B = log10(P1/P2), where P1 and P2 are distinct powers. The decibel, equal to one-tenth bel, is a more commonly used unit. Beep Code: When you turn on your PC--and all is well--you typically hear a single beep from your computer speaker, signaling that all is OK. If things are wrong--and the computer BIOS senses that things are wrong--a series of beeps will be emitted. This is the beep code. Based on the number of beeps, you can look up the meaning in your motherboard documentation and often diagnose the problem. Obvious things to check are whether your video card, processor, and/or memory are plugged in and seated properly. Bending Loss: Attenuation caused by high-order modes radiating from the outside of a fiber optic waveguide which occur when the fiber is bent around a small radius. See also macrobending, microbending.30

BER: Bit error rate. Bit errors are caused by interference, or loss of signal, so the stream of bits composing the DTV picture is disrupted. A measure of the errors in a transmitted signal. The number of bit errors detected in a unit of time, usually one second. Bit Error rate (BER) is calculated with the formula: BER = errored bits received/total bits sent Betacam: An analog component VTR system using a 1/2-inch tape cassettes. This was developed by Sony and is marketed by them and several other manufacturers. Although recording the Y, R-Y and B-Y component signals onto tape many machines are operated with coded (PAL or NTSC) video in and out. The system has continued to be developed over the years to offer models for the industrial and professional markets as well as full luminance bandwidth (Betacam SP), PCM audio and SDI connections. Digital versions exist as the high-end Digital Betacam and Betacam SX for ENG and similar applications. Betacam SX: A digital tape recording format developed by Sony which uses a constrained version of MPEG-2 compression at the 4:2:2 profile, Main Level (422P@ML) using 1/2-inch tape cassettes. B Frames or B Pictures (Bidirectionally Predictive-coded Pictures): Pictures that use both future and past pictures as a reference. This technique using motion compensated prediction from past and/or future reference fields or frames is termed bidirectional prediction. B-pictures provide the most compression. B-pictures do not propagate coding errors as they are never used as a reference. Bidirectionally Predictive Coding:

From the above pictures, there is some information which is not in the reference frame. Hence B picture is coded like P-pictures except the motion vectors can reference the previous reference picture, the next picture, or both. The following is the mechanism of B-picture coding.

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BIFS: Binary Format for Scenes. In MPEG-4, a set of elements called nodes that describe the layout of a multimedia layout BIFS-Update streams update the scene in time, BIFS-Anim streams animate the stream in time. BIFS are organized in a tree-lined hierarchical scene graph node structure derived from VRML. Big Picture: A coded picture that would cause VBV buffer underflow as defined in C.7. Big pictures can only occur in sequences where low_delay is equal to 1. "Skipped picture" is a term that is sometimes used to describe the same concept. Binary: A base-2 numbering system using the digits 0 and 1 (as opposed to 10 digits [0 - 9] in the decimal system). In computer systems, the binary digits are represented by two different voltages or currents, one corresponding to 0 and the other corresponding to 1. All computer programs are executed in binary form. Binary representation requires a greater number of digits than the base 10 decimal system more commonly used. For example, the base 10 number 254 is 11111110 in binary. The result of a binary multiplication contains the sum of digits of the original numbers. So: 10101111 x 11010100 = 1001000011101100 (In decimal 175 x 212 = 37,100) (From right to left, the digits represent 1, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, 2048, 4096, 8192, 16384, 32768) Each digit is known as a bit. This example multiplies two 8-bit numbers to produce a 16-bit result--a very common process in digital television equipment.

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Binary Code: Binary consists of a string of bits, with bits represented by 1s and 0s, e.g., 01010111000000001. The "bi" refers to base 2 mathematical representation (1s and 0s). Binary N-Zero Suppression (BNZS): Line coding system that replaces N number of zeros with a special code to maintain pulse density required for clock recovery. N is typically 3, 6, or 8. BIOS (Basic Input Output System): A program stored on your motherboard that controls all of the interaction between your components and your chipset. Simple access to video, keyboard, hard drive, floppy, CD-ROM, and other devices--that are enough to get an operating system loaded up--are included in the BIOS. Your BIOS is there to get things started for the operating system. BIP (Bit-Interleaved): A parity check that groups all the bits in a block into units (such as byte), then performs a parity check for each bit position in the group. BIP-8 (Bit Interleaved Parity 8): BIP-8 is a method used for error monitoring where each bit of the BIP-8 code word or byte, corresponds to even parity as calculated across matching bit positions for the distinct bytes in a SONET frame. That is the first BIP-8 bit would correspond to even parity across bit number 1 of a certain number of bytes in the SONET frame. The certain number of bytes depends upon whether you are calculating section, line, or path BIP-8. BIP-8 vs BER (where N is the N in OC-N) BER Max. Detection Time BIP-8 Violations 10e-3 10 ms 10e-4 100 ms 10-5 1s 10e-6 10s 10e-7 100s 10e-8 1000s 10e-9 10,000s 344xN 492xN 510xN 512xN 512xN 512xN 512xN

The BIP violations are counted over a sliding time window equal to the maximum detection time. The BIP-8 violation counts of individual STS-1s of an STS-N are added together. The above values take into account the error detection saturation effect at high BER. Design objectives for the for the average detection time depend on the level N of the Optical Carrier and are typically an order of magnitude lower than the Max-detection times shown in the above table for OC-3. As the optical rate increases the average detection time decreases proportionally. B-ISDN (Broadband Integrated Services Digital Network): A single ISDN network which can handle voice, data, and eventually video services.

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Bistable Multivibrator (flip-flop): A simple element of memory made up of an assembly of logic gates. Based on inputs, the state of a flip-flop can be changed back and forth, affecting the future output of the flip-flop. Bit (Binary Digit): The smallest unit of data in a digital system. A bit is a single one or zero. A group of bits, such as 8-bits or 16-bits, compose a byte. The number of bits in a byte depends upon the processing system being used. Typical byte sizes are 8, 16, and 32.

Bit Bucket: Any device capable of storing digital data--whether it be video, audio or other types of data. Bit Budget: The total amount of bits available on the media being used. In DVD, the bit budget of a single sided/single layer DVD5 disk is actually 4.7 GB. Bit Depth: The number of levels that a pixel might have, such as 256 with an 8-bit depth or 1,024 with a 10-bit depth. - How many bits it takes to represent the color in one pixel. The greater the bit depth, the more colors you can potentially display, and the more power it takes to represent a screen full of pixels at that bit depth. Common bit depths are 16 and 32 bits. Bit depth of 1 would only enable 2 colors, bit depth of 2 enables 4 colors, and so on, where the amount of potential colors can be determined by 2^bit_depth. Bitmap: A type of graphics format that specifies a number of pixels and then specifies what color those pixels are. A simplified example: 5 red, 4 green, 3 red, etc. GIF and JPEG files are bitmaps. If an image contains large blocks of solid color, it will take less storage space than an image with a lot of small regions with different colors. Bitmap font: A font where each character is stored as a bitmap graphic. These fonts are not easy to scale to different sizes. Bit-Stuffing: In asynchronous systems, a technique used to synchronise asynchronous signals to a common rate before multiplexing. Bit Parallel: Transmission of digital video a byte at a time down a multi-conductor cable where each pair of wires carries a single bit. This standard is covered under SMPTE 125M, EBU 3267-E, and ITU-R BT.656-4.

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Bit Period (T): The amount of time required to transmit a logical one or a logical zero.

Bit Rate: The rate at which the compressed bit stream is delivered from the channel to the input of a decoder. Bit Rate Reduction: See: Compression. Bit Serial: Transmission of digital video a bit at a time down a single conductor such as coaxial cable. May also be sent through fiber optics. This standard is covered under ITU-R BT.656-4. Bit Slippage: 1. Occurs when word framing is lost in a serial signal so that the relative value of a bit is incorrect. This is generally reset at the next serial signal (TRS-ID for composite and EAV/SAV for component). 2. The erroneous reading of a serial bit stream when the recovered clock phase drifts enough to miss a bit. 3. A phenomenon that occurs in parallel digital data buses when one or more bits get out of time in relation to the rest. The result is erroneous data. Differing cable lengths is the most common cause. Bit Stream: A continuous series of bits transmitted on a line. Black Level: Describes the appearance of darker portions of a video image. Black is the absence of light, so to create the black portions of an image, a display must be able to shut off as much light as possible. Displays with good black level capability not only produce deeper blacks, but also reveal more details and shading in dark or shadowy scenes. High-quality CRT-based TVs generally have better black level performance than digital displays such as plasma, LCD, DLP, and LCoS. Block: Rectangular area of picture, usually 8 x 8 pixels in size, which are individually subjected to DCT coding as part of a digital picture compression process. Artifact of compression generally showing momentarily as misplaced rectangular areas of picture with distinct boundaries. This is one of the major defects of digital compression, its visibility generally depending on the amount of compression used, the quality of the original signal, and the quality of the coder. The visible blocks may be 8 x 8 DCT blocks or "misplaced blocks"--16 x 16 pixel macroblocks, due to the failure of motion prediction/estimation in encoder or other motion vector system, such as a standards converter.

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The MPEG Data HierarchyBlock Coding: Block coding is the primary type of channel coding which was used in earlier Mobile communication systems and digital broadcasting system. Simply it adds redundancy so that at the receiver, one can decode with (theoretical) probability of zero errors provided that the Rate(R) would not exceed the Channel Capacity. There are many types of block codes, but the most important by far is Reed-Solomon coding because of its widespread use on the DTV, the Compact disc, the DVD, and in computer hard drives. Golay, BCH and Hamming codes are other examples of block codes. Block Error rate (BLER): One of the underlying concepts of error performance is the notion of Errored Blocks; i.e., blocks in which one or more bits are in error. A block is a set of consecutive bits associated with the path or section monitored by means of an Error Detection Code (EDC), such as Bit Interleaved Parity (BIP). Block Error rate (BLER) is calculated with the formula: BLER = errored blocks received/total blocks sent Bluetooth: Special Interest Group (www.bluetooth.com) founded in 1998 by Ericsson, IBM, Intel, Nokia and Toshiba. Bluetooth is an open standard for short-range transmission of digital voice and data between mobile devices (laptops, PDAs, phones) and desktop devices. It supports point-to-point and multipoint applications. Bluetooth provides up to 720 Kbps data transfer within a range of 10 meters and up to 100 meters with a power boost. Bluetooth transmits in the unlicensed 2.4GHz band and uses a frequency hopping spread spectrum technique that changes its signal 1600 times per second. If there is interference from other devices, the transmission does not stop, but its speed is downgraded. Ericsson (a Scandinavian company) was the first to develop Bluetooth. The name comes from Danish King Harald Blatan (Bluetooth) who in the 10th century began to Christianize the country. BNC (British Naval Connector): A connector type for 10Base2 or Thin-Net networks. Shaped like the letter T, it connects coaxial cables. The "T" has two male connectors and one female connector. The female connector can connect to the36

male connection of an Ethernet card that supports BNC connections, or remain empty. The male connectors link to coaxial cable or a terminator. The BNC part stands for either British Naval Connector, British Nut Connector, or Bayonet Neill-Concelman ... or perhaps it stands for some combination of those terms. Neill and Concelman are the names of the inventors of the BNC Connector Boot Up: To start up. Most computers contain a system operating program that they read out of memory and operate from after power up or restart. The process of reading and running that program is called boot up. Bottom Field: One of two fields that comprise a frame. Each line of a bottom field is spatially located immediately below the corresponding line of the top field. Bottleneck: Part of a system that limits the performance of the system. This term was derived from the neck of a bottle, which limits the flow of liquid due to the smaller circumference of the neck as compared to the wider body of the bottle. Often you will hear of people attempting to find and eliminate the bottlenecks in their computer systems or networks. This is certainly a helpful practice if the bottleneck is slowing things down inordinately, but as soon as you remove one bottleneck from a system remember that something else immediately becomes the bottleneck. For example, if you get a faster processor to speed up your 3D video, the 3D video card may be the bottleneck afterwards. Bouquet: collection of services marketed as a single entity BPSK: Biphase shift keying. BPSK is a digital frequency modulation technique used for sending data over a coaxial cable network. This type of modulation is less efficient--but also less susceptible to noise--than similar modulation techniques, such as QPSK and 64QAM. Brillouin Scattering - Stimulated Brillouin scattering is an interaction between the optical signal and the acoustic waves in the fiber that causes the optical power to be scattered backwards towards the transmitter. It is a narrowband process that effects each channel in a DWDM system individually. It is noticeable in systems that have channel powers in excess of 5 - 6 dBm. In most cases SBS can be suppressed by modulating the laser transmitter to broaden the line width. Broadband: 1) A response that is the same over a wide range of frequencies. 2) Capable of handling frequencies greater than those required for high-grade voice communications (higher than 3 to 4 kilohertz). Broadcast: A method of sending information over a network. With broadcasting, data comes from one source and goes to all other connected sources. This has the side effect of congesting a medium or large network segment very quickly. Sometimes broadcasting is necessary to locate network resources, but once found, more advanced networking protocols change to point-to-point connections to transmit data. Nowadays, switches and routers often do not pass along broadcast packets, but in the days of shared Ethernet broadcasting could really congest a network.

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Broadcaster (SERVICE Provider): organization which assembles a sequence of events or programmes to be delivered to the viewer based upon a schedule Broadcast FTP Protocol (BFTP): A one-way IP multicast based resource transfer protocol; the unidirectional Broadcast File Transfer Protocol (BFTP) is a simple, robust, one-way resource transfer protocol that is designed to efficiently deliver data in a one-way broadcast-only environment. This transfer protocol is appropriate for IP multicast over television vertical blanking interval (IPVBI), in IP multicast carried in MPEG-2, like with the DVB multiprotocol encapsulation, or in other unidirectional transport systems. It delivers constant bitrate (CBR) services or opportunistic services, depending on the characteristics and features of the transport stream multiplexer or VBI insertion device. Browser: Most commonly used to refer to a software program used to look at World Wide Web pages. More technically, a browser reads HTML pages over TCP/IP port 80 using HTTP. Thus, you will notice the term "HTTP" before the URL in your browser address bar, such as: http://www.geek.com/ Buffer: 1) A temporary location to store or group information in hardware or software. Buffers are used whenever data is received in sizes that may be different than the ideal size for the hardware or software that uses the buffer. For example, a 64-bit processor on a 16-bit bus may have a buffer to hold 16-bit requests until they equal 64-bits. Another use of buffers is to keep hardware from getting overwhelmed with information. In that scenario, you use a large buffer to hold data until a device or program is ready to receive it, instead of just pushing it onto a device that might not be ready. Buffers must be optimized in size to work efficiently for the purpose they are designed. 2) In optical fiber, a protective coating applied directly to the fiber (illustrated).

Buffered Memory: Memory modules that have extra chips on them to support Error Checking and Correcting (ECC) functionality. Buffer Management: Rules are specified so as to avoid underflow and overflow of receive side buffers. This is achieved by a hypothetical receive side timing model, which specifies timing relationships between outgoing PDUs at the send side. Buffer Overload: See: Video coder overload. Bug: This is commonly an error in design or programming in a hardware device or piece of software. The effects of a bug may be as harmless as an extra graphic on the screen, or as harmful as a system crash or loss of data. The first computer

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"bug" was a real bug, a moth, in fact, that was stuck between relays back in an early computer in 1945. See also Feature Burn-in: Screen burn-in can damage displays that rely on a phosphor coating on the screen plasma TVs and rear-projection CRT-based TVs are the most vulnerable to burn-in, and it's less likely, but possible with direct-view CRT TVs. Burn-in can occur when a static image such as a video game, stock or news ticker, or station logo remains on-screen for an extended period. Over time, these images can become etched into the phosphor coating, leaving faint but permanent impressions on-screen. The chance of burn-in can be reduced or eliminated by properly adjusting a display's brightness and contrast settings. Bus: A group of conductors that together constitute a major signal path. A signal path to which a number of inputs may be connected to feed to one or more outputs.

Bus Address: A code number sent out to activate a particular device on a shared communications bus. Business to Business (B2B): This term is often used to describe websites that sell goods or services to other businesses. Thus, businesses are serving other businesses as opposed to consumers. Business to Consumer (B2C): A form of doing business that deals with selling goods and services to the consumer marketplace. Examples of this would be selling consumer electronics, toys, or pet supplies. This contrasts with the business to business model. BWF Broadcast WAV: An audio file format based on Microsoft's WAV. It can carry PCM or MPEG encoded audio and adds the metadata, such as a description, originator, date and coding history, needed for interchange between broadcasters. Bypass: The ability of a station to isolate itself optically from a network while maintaining the continuity of the cable plant.

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Byte: A group of data bits that are processed together. Typically, a byte consists of 8, 16, 24 or 32 bits. 1 Byte = 8 bits = 256 discrete values (brightness, color, etc.) 1 kilobyte = 210 bytes = 1,024 bytes: (not 1000 bytes) 1 Megabyte = 220 bytes = 1,048,576 bytes: (not 1 million bytes) 1 Gigabyte = 230 bytes = 1,073,741,824 bytes: (not one billion bytes) 1 Terabyte = 240 bytes = 1,099,511,627,776 bytes: (not one trillion bytes) A full frame of digital television, sampled according to ITU-R 601, requires just under 1 Mbyte of storage (701 kbytes for 525 lines, 829 kbytes for 625 lines). HDTV frames are 4-to-5 times as large and digital film frames may be that much larger again. Byte aligned: A bit in a coded bit stream is byte-aligned if its position is a multiple of 8-bits from the first bit in the stream.

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-CC-Langage: A programming language developed in the late '70s. It became hugely popular due to the development of UNIX, which was written almost entirely in C. C was written by programmers for programmers, and it lets you write code in sloppy ways that other, more structured languages do not. When you think of programming in C, think of driving a Delorean. It goes really fast, but it's a mess inside. C++: An extension of the C programming language that adds object-oriented concepts. CableCARD: A removable security card available from cable TV providers. It allows a TV with a compatible CableCARD slot to receive digital cable programming, including premium and HD channels, without using a separate set-top box. The FCC (Federal Communications Commission) began requiring service providers to make CableCARDs available as of July 1, 2004. Contact your local cable provider for details regarding the availability and costs of CableCARD-related services. CableLabs: Founded in 1988 by members of the cable television industry, Cable Television Laboratories, Inc. (CableLabs) is a non-profit research and development consortium that is dedicated to pursuing new cable telecommunications technologies and to helping its cable operator members integrate those technical advancements into their business objectives. http://www.cablelabs.com/ Cable Modem: A data modem that uses the bandwidth of a given cable system, which promise speeds of up to 80 times faster than an ISDN line or six times faster than a dedicated T1 line (the type of connection most large corporations use). Because cable modems provide Internet access over cable TV networks (which rely primarily on fiber optic or coaxial cable), they are much faster than modems that use phone lines. Bandwidths are typically up to 30 Mbps in the downstream direction. Cache Memory : Generally a small chunk of fast memory that sits between either 1) a smaller, faster chunk of memory and a bigger, slower chunk of memory, or 2) a microprocessor and a bigger, slower chunk of memory. The purpose of cache memory is to provide a bridge from something that's comparatively very fast to something that's comparatively slow. Most microprocessors have built-in cache memory that holds some of the information from main memory. When the processor needs the information it takes it from the speedy cache instead of the slower main memory. Cach