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Video Glossary

8 mm: A compact videocassette record/playback tape format which uses eight millimeter wide magnetic tape. A worldwide standard established in 1983 allowing high quality video and audio recording. Flexibility, lightweight cameras and reduced tape storage requirements are among the format's advantages.

A or B Wind: When a roll of 16mm film, perforated along one edge, is held so that the outside end of the film leaves the roll at the top and toward the right, winding "A" should have the perforations on the edge of the film toward the observer, and winding "B" should have the perforations on the edge away from the observer. In both cases, the emulsion surface should face inward on the roll.

A/B Roll Editing: Video editing arrangement where scenes are edited from two source VCRs ("A" and "B") to a third (recording) VCR. Typically a switcher or mixer is used to provide transition effects between sources. Control over the machines and process can be done manually or automatically using an edit controller.

Adaptive Compression: Data compression software that continually analyzes and compensates its algorithm, depending on the type and content of the data and the storage medium.

AFV: AFV (Audio Followup Video). During video recording, the video signal is usually accompanied by an audio signal. Sometimes, during video editing, it is often necessary to separate the audio from the video signal. Audio-follow-video mixers allow accompanying audio to "follow" the video when switching video sources or not.

AGC: AGC (Automatic Gain Control) is the circuitry used to ensure that output signals are maintained at constant levels in the face of widely varying input signal levels. AGC is typically used to maintain a constant video luminance level by boosting weak (low light) picture signals electronically. Some equipment include gain controls which are switchable between automatic and manual control.

ALC: ALC (Automatic Level Control) is the circuitry used to automatically adjust the audio recording level to compensate for variations in input volume. Some equipment includes level controls which are switchable between automatic and manual control.

Aliasing: A form of image distortion caused by sampling frequencies being too low to faithfully reproduce image detail. (See Anti-aliasing.) Examples include: - Temporal aliasing - e.g., rotating wagon wheel spokes apparently reversing direction - Raster scan aliasing - e.g., twinkling or strobing effects on sharp horizontal lines - Stair-stepping - Stepped or jagged edges of angled lines, e.g., at ...

Analog: A device or method which makes use of non-discrete variations in frequency, amplitude, location, etc., to symbolize or carry sounds, signals, mathematical data or other information. The signals vary continuously instead of in steps. Analog technology "mimics" information, so that, e.g., a voice is represented as an electrical signal with frequency and amplitude proportional to the pitch and ...

Analog Video: A video signal that represents an infinite number of smooth gradations between given video levels. Analog video whether transmitted over cables, read from videotapes or broadcast, is subject to degradation due to noise, distortion and other electronic phenomena. Normal signal levels should be within 0.7-1 volt. By contrast, a digital video signal assigns a finite set of levels.

Anti-Aliasing: A form of interpolation used when combining images; pixels along the transitions between images are averaged to provide a smooth transition.

Aperture: Effective Aperture: The apparent diameter of a lens viewed from the position of the object against a diffusely illuminated background, such as a sky. Picture Aperture: The rectangular opening in a metal plate at which each frame of the motion picture film is situated during exposure, printing, or projection. Relative Aperture: The ratio of the focal length of a lens to its effective aperture for ...

Arithmetic Coding: Perhaps the major drawback to each of the {Huffman} encoding techniques is their poor performance when processing texts where one symbol has a probability of occurrence approaching unity. Although the entropy associated with such symbols is extremely low, each symbol must still be encoded as a discrete value. Arithmetic coding removes this restriction by representing messages as intervals of ...

Aspect Ratio: The relationship of width and height. When an image is displayed on different screens, the aspect ratio must be kept the same to avoid "stretching" in either the vertical or horizontal direction. For standard TV or monitor, the aspect ratio is 4: 3 yielding 160X120, 320X240 and 640X480 sizes. The HDTV video format has an aspect ratio of 16 to 9 (16: 9).

Asymmetrical Compression: A system which requires more processing capability to compress an image than to decompress an image. It is typically used for the mass distribution of programs on media such as CD-ROM, where significant expense can be incurred for the production and compression of the program but the playback system must be low in cost.

ATM: ATM (Asynchronous Transfer Mode) is a switching/transmission technique where data is transmitted in small, fixed sized cells (5 byte header, 48 byte payload). The cells lend themselves both to the time-division- multiplexing characteristics of the transmission media, and the packet switching characteristics desired of data networks. At each switching node, the ATM header identifies a virtual path ...

ATV: Advanced TV. 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, ...

Audio Bandwidth: The range of audio frequencies which directly influence the fidelity of a sound. The higher the audio bandwidth, the better the sound fidelity. The highest practical frequency which the human ear can normally hear is 20 kHz. An audio amplifier which processes all frequencies equally (flat response to 20 kHz) and a reasonably high signal-to-noise ratio, will faithfully reproduce the audio ...

Audio Dub: VCR feature allowing replacement of the audio signals on a previously recorded tape without disturbing the video signal. When dubbing is not available via the video recorder, audio dubbing can be performed while recording using an audio mixer.

Audio Mixing: The blending of two or more audio signals to generate a combined signal which is often used for audio dub. During video processing, audio mixing may be used to insert narration or background music.

AVI: Audio Video Interleaved. File format for digital video and audio under Windows wherein audio and video data are stored in alternate blocks. File format is cross-platform compatible, allowing *.AVI video files to be played under other operating systems.

AVK: Audio Video Kernel. DVI system software designed to play motion video and audio across hardware and operating system environments.

Back Light: 1) A light source that illuminates a subject from behind, used to separate the subject from the background and give them depth and dimension. Back lights are often improperly applied or overlooked completely. 2) Also, a switch on some camcorders used to compensate exposure for situations where the brightest light is coming from behind the subject.

Background Video: 1) Video that forms a background scene into which a key may be inserted. 2) A solid color video output generated by the background generator within a device, such as a production switcher, for use as background video in key effects.

Backing: Anti-halation Backing: A temporary, dark-colored, gelatin coating which is sometimes applied to the rear side of a photographic plate or film to reduce halation by absorbing any light that may pass through the emulsion. Non-Curl Backing: A transparent, gelatin coating, sometimes applied to the opposite side of a photographic film from the emulsion to prevent curling by balancing the forces that ...

B-Frame: An {MPEG} video frame type that provides bi-directional interframe compression. B frames derive their content from the closest I or P frames, one in the past and one in the future. B frames require greater computing power to produce than I or P frames. B frames enable compression rates of 200: 1. Robust MPEG encoders employ a combination of B, I, and P frame encoding.

Black a Tape: The process of recording a black burst signal across the entire length of a tape. Often done before recording edited footage on the tape to give the tape clean, continuous video and sync and to insure there is no video already on the tape.

Black Burst: A composite color video signal comprised of sync, color burst and black video. It is used to synchronize (genlock) other video sources to the same sync and color information. Black burst generators are used in video studios to "lock" the entire facility to a common signal ("house sync" or "house black").

Blanking Interval: The horizontal blanking interval is the time between the end of one scanning line and the beginning of the next. The vertical blanking interval is the time between the end of one video field and the beginning of the next. Blanking occurs when a monitor's electron beam is positioned to start a new line or a new field. The blanking interval is used to instantaneously reduce the beam's amplitude so ...

Blanking Level: Also known as the pedestal, it is the voltage level produced at the end of each horizontal picture line which separates the portion of the video signal containing the picture information from the portion containing the synchronizing information. This voltage makes the electron beam "invisible" as it moves to draw the next visible line.

Blue Screen: A film or video technique in which an object or performer is taped against a blue-colored background. In post-production, the blue color is electronically removed, allowing images to be combined. Also, the film industry's term for chroma key.

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 ...

CD-I: CD-I means Compact Disc Interactive. It is meant to provide a standard platform for mass consumer interactive multimedia applications. So it is more akin to CD-DA, in that it is a full specification for both the data/code and standalone playback hardware: a CD-I player has a CPU, RAM, ROM, OS, and audio/video/(MPEG) decoders built into it. Portable players add an LCD screen and ...

CD-XA: CD-XA is a CD-ROM extension being designed to support digital audio and still images. Announced in August 1988 by Microsoft, Philips, and Sony, the CD-ROM XA (for Extended Architecture) format incorporates audio from the CD-I format. It is consistent with ISO 9660, (the volume and the structure of CD-ROM), is an application extension of the Yellow Book, and draws on the Green Book. CD-XA ...

Cel Animation Production Artwork: Any cel, drawing or painting used in any part of the making of a film. (Note: Production does NOT mean "under the camera". Many types of art created for the production of the film were not photographed, but instead acted as a guide for artists to follow. Some of the different types of production artwork are: Concept Art Inspirational sketches or paintings used to establish the situations, ...

Cel Levels: The individual cels that go together to make up a cel setup. Due to technical considerations, it was very rare for two or more separate characters to be included on a single cel level. Usually, each element was on its own cel, with up to a maximum of five levels to a scene. Because of the added density of the multiple cel levels, the paint colors were corrected for the discoloration caused by the ...

Cel Setups: A combination of two or more cels, with or without a background, which work together to form a complete image. These can be either Matching (the way the image appeared in the finished film) or Non-Matching (combinations of elements which are pleasing together, but do not appear together in the film).

Cell Compression: Cell is a compression technique developed by Sun Microsystems Inc. The compression algorithms, the bit-stream definition, and the decompression algorithms are open. That is Sun will tell anybody who is interested about them . Cell compression is similar to MPEG and H.261 in that there is a lot of room for value-add on the compressor end. Getting the highest quality image from a given bit count at ...

Cels: Sheets of clear plastic, containing the images of the characters, which are placed over a background, and then photographed in succession to give the illusion of movement in the completed film. The outline of the image, whether hand-inked or xerographed, is applied to the front of the cel. The colors are painted by hand onto the back of the cel to eliminate brushstrokes. Large areas of black ...

Character Generator: Device that electronically generates text which can be superimposed over a video signal. Text is usually entered via a keyboard, allowing selection of various fonts, sizes, colors, styles and background colors, then stored as multiple pages for retrieval.

Chroma: The color portion of the video signal that includes hue (phase angle) and saturation (amplitude) information. Requires luminance, or light intensity, to make it visible.

Chroma Key: The process of overlaying one video signal over another by replacing a range of colors with the second signal. Typically, the first (foreground) picture is photographed with a person or object against a special, single-color background (the key-color). The second picture is inserted in place of the key-color. The most common example is in broadcast weather segments where pictures of weather maps ...

Chrominance Level: The color portion of a video signal separate from the luminance (or brightness) component, representing the saturation and hue (tint) at a particular point of the image. Black, gray and white have no chrominance, but any colored signal has both chrominance and luminance. The higher the chrominance level, the stronger the color (e.g., a strong signal produces red, and a weak signal, pink).

CIF: Common Image Format. The standardization of the structure of the samples that represent the picture information of a single frame in digital HDTV, independent of frame rate and sync/blank structure. The uncompressed bit rates for transmitting CIF at 29.97 frames/sec is 36.45 Mbit/sec.

Cinepak: A software file-compression scheme for video that's well suited to low-power CPUs. Established by SuperMac (now Radius Technologies), it is common on Windows and the Mac OS. Cinepak video is typically 320-by-240 pixels at 15fps.

Clip: A continuous set of frames from a source tape or reel. Also called a scene or "take."

Clipping: The electronic process of shearing off the peaks of either the white or black excursions of a video signal for limiting purposes. Sometimes, clipping is performed prior to modulation, and sometimes to limit the signal, so it will not exceed a predetermined level.

Codec: Code/Decode. An encoder plus a decoder is an electric device that compresses and decompresses digital signals. CODECs usually perform A-to-D and D-to-A conversion.

Color Balance: The process of matching the amplitudes of red, green and blue signals so the resulting mixture makes an accurate white color.

Color Bars: An electronically generated video pattern consisting of eight equal width colors, used to establish a proper color reference before recording and playback and for adjustment purposes.

Color Burst: The portion of a color video signal which contains a short sample of the color subcarrier used to add color to a signal. It is used as a color synchronization signal to establish a reference for the color information following it and is used by a color monitor to decode the color portion of a video signal. The color burst acts as both amplitude and phase reference for color hue and intensity. The ...

Color Correction: A process in which the coloring in a television image is altered or corrected by electronic means. (See Chroma Corrector)

Color Keying: To superimpose one image over another for special effects.

Color Subcarrier: The 3.58 MHz/NTSC (4.43 MHz/PAL) signal added to a black and white television signal to add color information. The subcarrier frequency is too high to be detected by black and white televisions ensuring compatibility. Color sets employ special circuitry which detects and decodes the color component for display.

Component Video: Most home video signals consist of combined (composite) video signals, composed of luminance (brightness) information, chrominance (color) information and sync information. To get maximum video quality, professional equipment (Betacam and MII) and some consumer equipment (S-VHS and Hi-8) keep the video components separate. Component video comes in several varieties: RGB (red, green, blue), YUV ...

Composite Video: A video signal in which the luminance (brightness), chrominance (color), blanking pulses, sync pulses and color burst information have been combined using one of the coding standards. ({NTSC}, {PAL}, {SECAM})

Compressed Video: A digital video image or segment that has been processed using a variety of computer compression algorithms and other techniques to reduce the amount of data required to accurately represent the video content.

Contrast: (1) The general term for describing the tone separation in a print in relation to a given difference in the light-and.shade of the negative or subject from which it was made. Thus, "contrast" is the general term for the property called "gamma" (Y), which is measured by making an H & D Curve for the proces under study. (2) The range of tones in a photographic negative or positive expressed as the ...

Crosstalk: The interference between two audio or two video signals caused by unwanted stray signals. In video, crosstalk between input channels can be classified into two basic categories: luminance/sync crosstalk; and color (chroma) crosstalk. When video crosstalk is too high, ghost images from one source appear over the other. In audio, signal leakage, typically between left and right channels or between ...

Curl: A defect of a photographic film consisting of unflatness in a plane cutting across the width of the film. Curl may result from improper drying conditions, and the direction and amount of curl may vary with the humidity of the air to which the film is exposed.

DAT: Digital Audio Tape. A consumer recording and playback medium developed by Sony, maintaining a signal quality equal to that of the CD.

Definition: The aggregate of fine details available on-screen. The higher the image definition, the greater the number of details that can be discerned. During video recording and subsequent playback, several factors can conspire to cause a loss of definition. Among these are the limited frequency response of magnetic tapes and signal losses associated with electronic circuitry employed in the recording ...

Delay Correction: When an electronic signal travels through electronic circuitry or even through long coaxial cable runs, delay problems may occur. This is manifested as a displaced image and special electronic circuitry is needed to correct it.

Delta Frame: Also called Difference Frame. Contains only the pixels different from the preceding Key Frame. Delta Frames reduce the overall size of the video clip to be stored on disk

Digital: A method of signal representation by a set of discrete numerical values, as opposed to a continuously fluctuating current or voltage or where information is transferred by electrical "on-off" or "high-low" pulses, instead of continuously varying ("analog") signals. An analog signal is converted to digital by the use of an analog-to-digital (A/D) converter chip by taking samples of the signal at a ...

Distortion: In video, distortion usually refers to changes in the luminance or chrominance portions of a signal. It may contort the picture and produce improper contrast, faulty luminance levels, twisted images, erroneous colors and snow. In audio, distortion refers to any undesired changes in the waveform of a signal caused by the introduction of spurious elements. The most common audio distortions are ...

Drop Frame: A type of SMPTE time code designed to match clock time exactly. Two frames of code are dropped every minute, on the minute, except every tenth minute, to correct for the fact that color frames occur at a rate of 29.97 per second, rather than an exact 30 frames per second (see Non-Drop Frame). Designed to drive editors crazy.

DSK: DSK (Downstream Keying) is an effect available in some special effects generators and video mixers in which one video signal is keyed on top of another video signal. The lightest portions of the DSK signal replace the source video leaving the dark areas showing the original video image. Optionally, the DSK signal can be inverted so the dark portions are keyed rather than the lightest portions ...

DVI: Digital Video Interactive (DVI) technology brings television to the microcomputer. DVI's concept is simple: information is digitized and stored on a random-access device such as a hard disk or a CD-ROM, and is accessed by a computer. DVI requires extensive compression and real-time decompression of images. Until recently this capability was missing. DVI enables new applications. For example, a ...

Eberhard Effect: Another manifestation of adjacency effects. A series of photographic line images of various widths, all exposed with equal intensities. As the lines become narrower, the concentration of reaction products is reduced, and thus the narrower lines develop to a higher density than do the wider lines. This effect would be expected to continue with successive narrowing until one reached the width of ...

Emulsion Layer: (1) Broadly, any light-sensitive photographic material consisting of a gelatin emulsion containing silver halide together with the base and any other layers or ingredients that may be required to produce a film having desirable mechanical and photographic properties (2) In discussions of the anatomy of a photographic film, the emulsion layer is any coating that contains light sensitive silver ...

Fade: The act of dissolving a video picture to either a color, pattern or titles. Fading a video image is often used as an artistic tool in video productions, most commonly seen as a fade to black. In audio, there is a decrease in the sound level until it is no longer audible. Audio fading is often used in conjunction with video fading causing the sound and image to fade simultaneously.

Field: One-half of a complete television picture consisting of one complete vertical scan of the video image containing 262.5 line for NTSC and 312.5 lines for PAL. Two fields make up a complete television picture frame. The first field of a frame contains all the odd numbered lines, and the second field contains all of the even numbered lines.

Fielding: Refers to the size of the area on the artwork which falls within the sight of the camera. Thus, a 12 field is roughly 12 inches across and a 9 field is 9 inches across. Even though a drawing or cel may be of a standard 12 or 16 field size, the camera may have been zoomed in to a 8 or 9 field, focusing on a tighter area of the artwork, eliminating the outer margins of the sheet. Most early ...

Fill Light: Fill lights, commonly referred to as "scoops," provide a soft-edged field of light used to provide additional subject illumination to reduce harsh shadows or areas not highlighted by the key light.

Filtering: A process used in both analog and digital image processing to reduce bandwidth. Filters can be designed to remove information content such as high or low frequencies, for example, or to average adjacent pixels, creating a new value from two or more pixels.

Flicker: A strobing picture artifact, similar to an old-time movie effect, mainly related to vertical syncs and video field display rates. Some flicker normally exists due to interlacing, but is more apparent in 50 Hz systems (PAL) and when converting film (24 fps) to video (30 fps). Flicker may also be a problem when static computer images are transferred to video.

Footage Encoder Time Code Generator: An electronic device which takes the input from a reader of Keykode numbers, decodes this information and correlates the numbers with the SMPTE time code it generates. These data, along with 3:2 pull-down status of the transfer, footage count, and audio time code (if applicable) are made available for window burn-ins, VITC-LTC recording and output to a computer. (See KODAK Guide to Film and Video ...

FPS: Frames Per Second. The number of images contained in a single second of a moving picture. Thirty FPS is considered full-motion video. Many proprietary digital video technologies produce only 15 FPS video. Film is 24 FPS, NTSC is 30 FPS and PAL/SECAM is 25 FPS.

Frame: A single, complete picture in video or film recording. A video frame consists of two interlaced fields of either 525 lines (NTSC) or 625 lines (PAL/SECAM), running at 30 frames per second (NTSC) or 25 frames per second (PAL/SECAM). Also used to describe the total visible area of a video image.

Frame Synchronization: A digital electronic device which synchronizes two or more video signals. The frame synchronizer uses one of its inputs as a reference and genlocks the other video signals to the reference's sync and color burst signals. By delaying the other signals so that each line and field starts at the same time, two or more video images can be blended, wiped and otherwise processed together. (A TBC takes ...

Freeze: Special effect in which the picture is held as a still image. It is possible to freeze either one field or a whole frame. Freezing one field provides a more stable image if the subject is moving, however, the resolution of the video image is half that of a full frame freeze. Digital freeze frame is one special effect that could be created with a special effects generator or a TBC

Frequency Response: A measure of the quality of reproduction of various frequencies (audio and video) by a circuit or device. If the frequency response of a video processor is adequate, there is no deterioration in image quality at the bandwidth extremes. For video, the NTSC broadcast bandwidth is 4.2 MHz and the PAL broadcast bandwidth is 5.5 MHz. For audio, full bandwidth implies a frequency response extending ...

Full Motion Video: Video reproduction at 30 frames per second (NTSC-original signals) or 25 frames per second (PAL-original signals).

Generation Loss: When an analog master videotape is duplicated, the second-generation copy is usually inferior in some way to the master. This degradation appears as loss of detail, improper colors, sync loss, etc. Limited frequency response of audio/video magnetic tape and imperfections in electronic circuitry are the main causes of generation loss. Higher performance formats (such as 1-inch) exhibit much less ...

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 ...

Halation: A defect of photographic films and plates. Light forming an image on the film is scattered by passing through the emulsion or by reflection at the emulsion or base surfaces. This scattered light causes a local fog which is especially noticeable around images of light sources or sharply defined highlight areas.

HDTV: High-Definition Television. A television system with approximately twice the horizontal and twice the vertical resolution of current 525-line and 625-line systems, component colour coding (e.g. RGB or {YCbCr}) a picture aspect ratio of 16:9 and a frame rate of at least 24 Hz. Currently there are a number of proposed HDTV standards, including HD-MAC, HiVision and others.

Hi-8: An improved version of the 8mm tape format capable of recording better picture resolution (definition). A higher-density tape is required which provides a wider luminance bandwidth, resulting in sharper picture quality (over 400 horizontal lines vs. 240 for standard 8mm) and improved signal-to-noise ratio. Camcorders using this format are very small, light and provide a picture quality similar to ...

Hiss: The most common audible noise component in audio recording, stemming from a combination of circuit and tape noise. Several noise reduction systems are available, such as Dolby, DBX, DNR (Dynamic Noise Reduction), DNL (Dynamic Noise Limiter), to help alleviate such problems

Horizontal Resolution: Rating of the fine detail (definition) of a TV picture, measured in scan lines. The more lines, the higher the resolution and the better the picture. A standard VHS format VCR produces 240 lines of horizontal resolution, while over 400 lines are possible with S-VHS, S-VHS-C, and Hi-8 camcorders.

HSB: {Hue} Saturation Brightness. With the HSB model, all colors can be defined by expressing their levels of hue (the pigment), saturation (the amount of pigment) and brightness (the amount of white included), in percentages.

Hue: Often used synonymously with the term tint. It is the dominant wavelength which distinguishes a color such as red, yellow, etc. Most commonly, video hue is influenced by: A camera's white balance Scene lighting

Huffman Coding: For a given character distribution, by assigning short codes to frequently occurring characters and longer codes to infrequently occurring characters, Huffman's minimum redundancy encoding minimizes the average number of bytes required to represent the characters in a text. Static Huffman encoding uses a fixed set of codes, based on a representative sample of data, for processing texts. ...

Hybrid Coder: In the archetypal hybrid coder, an estimate of the next frame to be processed is formed from the current frame and the difference is then encoded by some purely intraframe mechanism. In recent years, the most attention has been paid to the motion-compensated DCT coder where the estimate is formed by a two-dimensional warp of the previous frame and the difference is encoded using a block transform ...

I Frame: An {MPEG} video frame incorporating intraframe compression where only the information in a single frame is considered. Unlike P and B frames, I frames do not take redundancy between adjacent frames into account. I Frame encoding compresses at up to a 6: 1 ratio before noticeable artifacts appear. It is used in conjunction with B and P frame encoding.

IDTV: Improved Definition Television. A television system that offers picture quality substantially improved over conventional receivers, for signals originated in standard 525-line or 625-line format, by processing that involves the use of field store and/or frame store (memory) techniques at the receiver . One example is the use of field or frame memory to implement de-interlacing at the receiver in ...

Image Resolution: The fineness or coarseness of an image as it was digitized, measured in Dots Per Inch (DPI), typically from 200 to 400 DPI.

Interactive Video: The fusion of video and computer technology. A video program and a computer program running in tandem under the control of the user. In interactive video, the user's actions, choices, and decisions affect the way in which the program unfolds.

Interlace: A system developed for television which divides each video frame into two fields. This is done by first drawing one field consisting of an image's odd scan lines (1, 3, 5...525) and then drawing the remaining even scan lines (2, 4, 6...), interweaving both fields. Interlacing reduces the perception of screen flicker. Interlacing can cause annoying effects with images such as computer generated ...

ISDN: ISDN stands for "Integrated Services Digital Networks", and it's a CCITT term for a relatively new telecommunications service package. ISDN is basically the telephone network turned all-digital end to end, using existing switches and wiring (for the most part) upgraded so that the basic call is a 64 kbps end-to-end channel, with bit-diddling as needed (but not when not needed!). Packet and maybe ...

JPEG: Joint Photographic Expert Group. JPEG is a high-quality, single-picture spatial compression standard for still video images that allows the image to occupy less memory or disk space. Uses DCT algorithm (Discrete Cosine Transfer). Has been adapted to video but provides no frame compression. Like the MPEG standard, it includes options for trading off between storage space and image quality.

Key Frame: A video frame in which all of the video information is recorded in compressed fashion. If the clip has a large amount of motion, better playback will occur with every frame being a Key Frame. If there is very little motion, such as a narrator, a higher number of Delta Frames will give satisfactory playback.

Keying: The process of replacing part of one video image with video from another image. As opposed to mixing images together, keying "cuts" one image cleanly into another.

Letter Box: A television system that limits the recording or transmission of useful picture information to about three-quarters of the available vertical picture height of the distribution format (e.g. 525-line) in order to offer program material that has a wide picture aspect ratio.

Linear: The layout of audio and video scenes in a continuous length of tape. Working with linear video is slower than with non-linear footage, because the operator must fast forward or rewind to search for scenes.

Looping: A term used to describe the chaining of a video signal through several video devices (distribution amplifiers, VCRs, monitors, etc.). A VCR may be hooked up to a distribution amplifier which is supplied with a video input connector and a loop output connector. When a signal is fed to the distribution amplifier, it is also fed unprocessed to the loop output connector (parallel connection) on the ...

Lossy Compression: A scheme that, after decompression, does not produce exactly the same data that was given to the compressor. Due to the nature of image data, the losses are often imperceptible to the human eye. Although image quality may suffer, many experts believe that up to 95 percent of the data in a typical image may be discarded without a noticeable loss in apparent resolution.

Luma: Video originates with linear-light (tristimulus) RGB primary components, conventionally contained in the range 0 (black) to +1 (white). From the RGB triple, three gamma-corrected primary signals are computed; each is essentially the 0.45-power of the corresponding tristimulus value, similar to a square-root function. In a practical system such as a television camera, however, in order to ...

Luminance: The degree of brightness (black and white portion of the video signal) at any given point in the video image. A video signal is comprised of luminance, chrominance (color information) and sync. If luminance is high, the picture is bright and if low the picture is dark. Changing the chrominance does not affect the brightness of the picture. May be measured in lux or foot-candles.

LZW: Lempel-Ziv Welch (LZW) Compression is the algorithm used by the Unix compress command to reduce the size of files, eg. for archival or transmission. The algorithm relies on repetition of byte sequences (strings) in its input. It maintains a table mapping input strings to their associated output codes. The table initially contains mappings for all possible strings of length one. Input is taken one ...

Model-Based Coder: Communicating a higher-level model of the image than pixels is an active area of research. The idea is to have the transmitter and receiver agree on the basic model for the image; the transmitter then sends parameters to manipulate this model in lieu of picture elements themselves. Model-based decoders are similar to computer graphics rendering programs. The model-based coder trades generality ...

MPEG: Motion Picture Expert Group. Similar to spatial compression of JPEG, but adds frame-to-frame temporal compression. Compaction is typically 3 times better than video JPEG. Like the JPEG standard, it includes options for trading off between storage space and image quality.

MPEG-1: MPEG-1 defines a set of international standards for the compression and decompression of digital video signals. MPEG-1 specifies a video resolution of 352-by-240 pixels compressed at 30 frames per second (fps) at a bandwidth of 150 kilobytes per second.

MPEG-2: MPEG-2 is targeted for use with high-bandwidth broadcast applications specifying 720-by-480 playback at 60 fields per second at data rates ranging from 500 kilobytes per second to more than two megabytes per second. Essentially, MPEG-2 is digital television.

Multimedia: Refers to the delivery of information that combines different content formats (motion video, audio, still images, graphics, animation, text, etc.). A somewhat ambiguous term that describes the ability to combine audio, video and other information with graphics, control, storage and other features of computer-based systems

Noise: A general term used in electronics to indicate any unwanted electrical signal, unrelated to the original signal. Video noise is generally manifested as snow, graininess, ghost images or picture static induced by external sources such as the national power-line grid, electric motors, fluorescent lamps, etc. In audio, noise is generally manifested as hiss and static.

Noise Gate: A device used to modify a signal's noise characteristics. In video, noise gates provide optimal automatic suppression of snow (signal noise level). In audio, a noise gate provides a setable signal level threshold below which all sound is removed.

Noise Reduction: An electronic process used to reduce noise levels in audio and video. In video, the most effective noise reduction is accomplished by digitizing the video signal and carrying out a computerized pixel by pixel analysis of the data. In audio, the most effective systems employ an encode/decode scheme, performed before and after recording, such as the Dolby audio noise reduction system. Noise ...

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

P Frame: An MPEG encoding method using a predictive algorithm to take into account information that is common among adjacent frames. P frames predict the difference between the current frame and the closest preceding I or P frame to minimize the amount of data that needs to be coded for each frame. P frame encoding is used in conjunction with I and B frame encoding.

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

Post Production: All production work done after the raw video footage and audio elements have been captured. Editing, titling, special effects insertion, image enhancement, audio mixing and other production work is done during post-production. Videonics equipment is ideally suited for use in post-production.

QCIF: Quarter Common source Intermediate Format (1/4 CIF , e.g. 1180*144). The uncompressed bit rates for transmitting QCIF at 29.97 frames/sec is 9.115 Mbit/s.

Region Coding: Region Coding has received attention because of the ease with which it can be decoded and the fact that a coder of this type is used in Intel's Digital Video Interactive system (DVI), the only commercially available system designed expressly for low-cost, low-bandwidth multimedia video. Its operation is relatively simple. The basic design is due to Kunt. Envision a decoder that can reproduce ...

Resolution: A measure of the ability to reproduce detail. Generally, referred to as horizontal resolution and evaluated by establishing the number of horizontal lines which are clearly discernible on a test pattern. Resolution specifications are not very well standardized, especially as stated in connection with monitors. Using the rule of thumb of 80 lines per MHz of bandwidth, VHS and 8mm typically ...

Reticulation: The formation of a coarse, crackled surface on the emulsion coating of a film during improper processing. If some process solution is too hot or too alkaline, it may cause excessive swelling of the emulsion and this swollen gelatin may fail to dry down as a smooth homogeneous layer.

Reversal Process: Any photographic process in which an image is produced by secondary development of the silver halide grains that remain after the latent image has been changed to silver by primary development and destroyed by a chemical bleach. In the case of film exposed in a camera, the first developer changes the latent image to a negative silver image. This is destroyed by a bleach and the remaining silver ...

Sampling: The first step in the process of converting an analog signal into a digital representation. This is accomplished by measuring the value of the analog signal at regular intervals called samples. These values are then encoded to provide a digital representation of the analog signal.

Scalable Video: With respect to Indeo(TM) video technology, it is a playback format that can determine the playback capabilities of the computer on which it is playing. Using this information, it allows video playback to take advantage of high-performance computer capabilities while retaining the ability to play on a lower performance computer.

SECAM: SECAM (Sequentiel Coleur A Memoire) is a 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.

SEG: SEG (Special Effects Generator) is a device designed to generate special effects. The simplest devices process a single video signal, change its color, generate sepia tones, invert the picture to a negative, posterize the image and fade or break up the image into various patterns. More sophisticated equipment uses several video sources, computer-generated graphics and sophisticated animation with ...

Sensitometer: An instrument with which a photographic emulsion is given a graduated series of exposures to light of controlled spectral quality, intensity, and duration. Depending upon whether the exposures vary in brightness or duration, the instrument may be called an intensity scale or a time scale sensitometer.

Shotgun Microphone: Long, highly directional microphone designed to pick up sounds directly in front of the microphone, rejecting sound from other directions. Named for its appearance.

Signal-to-Noise Ratio: The ratio in decibels (dB), of an audio or video signal, between the signal's maximum peak-to-peak signal voltage and the measured voltage of what remains when the signal is removed, (i.e., the ratio of the signal to that of the noise). In video, the higher the ratio, the less snow is visible. In audio, the higher the ratio, the cleaner the sound. Audio s/n ratios vary tremendously from compact ...

SMPTE: SMPTE is the Society of Motion Picture and Television Engineers. There is an SMPTE time code standard (hr:min:sec:frame) used to identify video frames.

Special Effects: Artistic effects added to a video production in order to enhance the production by creating drama, enhancing the mood or furthering the story. Special effects may vary from the limited addition of patterns or the mixing of several video images together, to sophisticated digital effects such as picture compression, page flipping and three-dimensional effects. Special effects are usually created ...

Sub Band Coding: Sub-band coding for images has roots in work done in the 1950s by Bedford and on Mixed Highs image compression done by Kretzmer in 1954. Schreiber and Buckley explored general two channel coding of still pictures where the low spatial frequency channel was coarsely sampled and finely quantized and the high spatial frequency channel was finely sampled and coarsely quantized. More recently, ...

S-Video: Type of video signal used in Hi8, S-VHS and some laserdisc formats. It transmits luminance and color portions separately, using multiple wires thereby keeping any signal interaction (degradation) to a minimum. S-Video avoids composite video encoding, such as NTSC, and the resulting loss of picture quality. Also known as Y/C Video.

Symmetrical Compression: A compression system which requires equal processing capability for Compression and decompression of an image. This form of compression is used in applications where both compression and decompression will be utilized frequently. Examples include: still-image databasing, still-image transmission (color fax), video production, video mail, videophones, and videoconferencing.

Sync: Synchronization. A term used in electronics to describe the precise alignment of two signals or functions. In video, sync is an essential element for maintaining the proper clocking of video signals. The sync signal is used by a monitor to know where and when to draw the on-screen video image. The horizontal sync signal is a short pulse generated at the beginning of each video line which tells ...

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 ...

Take: When a particular scene is repeated and photographed more than once in an effort to get a perfect recording of some special action, each photographic record of the scene or of a repetition of the scene is known as a "take." For example, the seventh scene of a particular sequence might be photographed three times, and the resulting records would be called: Scene 7, Take l; Scene 7, Take 2; and ...

Talent: A term used to refer to on-camera subjects in a video production.

Telecine: Telecine is a term used to describe a device used to convert film to video. In advanced telecine machines, the movie film is digitally sampled and converted to video, frame by frame in real-time. Frame rate is the biggest problem encountered in film-to-video conversion. Movie film has a frame rate of 18, 24 or 30 fps (frames per second) contrasting with the 30 and 25 fps video frame rates of NTSC ...

Teleconference: A general term for a meeting not held in person. Usually refers to a multi-party telephone call, set up by the phone company or private source, which enables more than two callers to participate in a conversation. The growing use of video allows participants at remote locations to see, hear, and participate in proceedings, or share visual data ("video conference").

Tele-Prompter: A device for displaying large, readable text on a partially transparent screen for video production. The tele-prompter uses a monitor mounted under the camera lens, facing up, and a mirrored glass which reflects the monitor's image toward the talent. Since the camera shoots through the mirrored glass and the mirrored glass is transparent to the camera, the talent can look directly into the camera ...

Trellis Coding: Trellis coding is a source coding technique that has resulted in numerous publications and some very effective source codes. Unfortunately, the computational burden of these codes is tremendous and grows exponentially with the encoding rate. A trellis is a transition diagram, that takes time into account, for a finite state machine. Populating a trellis means specifying output symbols for each ...

Video Camera: A camera which contains an electronic image sensor rather than photographic film. The lens focuses an image on an electronic tube or CCD chip. A camera has electronic circuitry which generates color and sync pulses. Most portable consumer cameras are equipped with a full complement of audio circuitry, e.g., microphone, audio amplifier and additional audio electronics. In order to obtain better ...

Video Editing: A procedure for combining selected portions of video footage in order to create a new, combined version. A variety of editing consoles are available. During video editing, special effects such as wipes, dissolves, inserts, etc. can be added. Professional editing is done using time code recorded on every frame of the magnetic tape allowing single frame accuracy. Audio editing is often carried out ...

Video Gain: The nominal composite video signal level is 1 volt. At this level, a fully saturated image is transmitted and boosting the signal offers no advantage. Most video equipment is designed to output the same 1-volt level video signal. In cases where the signal level has been reduced, such as after a long cable run, an amplifier with video gain may be employed to restore the proper level.

Video Mixer: A device used to combine video signals from two or more sources. Inputs are synchronized, then mixed along with various special effects patterns and shapes. A video mixer usually generates sync signals allowing genlocking of additional video sources to the first source.

Videoconferencing: A terms used to describe a meeting between two or more people that is not held in person, but rather using video as a communication tool. Each party in the conference has a video receiver to view the other participants, and, optionally, a video broadcaster (such as a webcam) to broadcaster his/her image to the other participants.

White Balance: An electronic process used in camcorders and video cameras to calibrate the picture for accurate color display in different lighting conditions. (i.e., sunlight vs. indoor incandescent) White balancing should be performed prior to any recording, typically by pointing the camera at a white object for reference.

Wipe: Special effect in which two pictures from different video sources are displayed on one screen. special effects generators provide numerous wipe patterns varying from simple horizontal and vertical wipes to multi-shaped, multi-colored arrangements.

YCbCr: The international standard CCIR-601-1 specifies eight-bit digital coding for component video, with black at luma code 16 and white at luma code 235, and chroma in eight-bit two's complement form centred on 128 with a peak at code 224. This coding has a slightly smaller excursion for luma than for chroma: luma has 219 risers compared to 224 for Cb and Cr. The notation CbCr distinguishes this set ...

YCC: Kodak's PhotoYCC colour space (for PhotoCD) is similar to YCbCr, except that Y is coded with lots of headroom and no footroom, and the scaling of Cb and Cr is different from that of Rec. 601-1 in order to accommodate a wider colour gamut: Y_8bit = (255/1.402) * Y C1_8bit = 156 + 111.40 * (Bgamma - Y) C2_8bit = 137 + 135.64 * (Rgamma - Y) The C1 and C2 components are subsequently ...

YIQ: The U and V signals above must be carried with equal bandwidth, albeit less than that of luma. However, the human visual system has less spatial acuity for magenta-green transitions than it does for red-cyan. Thus, if signals I and Q are formed from a 123 degree rotation of U and V respectively [sic], the Q signal can be more severely filtered than I (to about 600 kHz, compared to about 1.3 MHz) ...

YPbPr: If three components are to be conveyed in three separate channels with identical unity excursions, then the Pb and Pr colour difference components are used: Pb = (0.5/0.886) * (Bgamma - Y) Pr = (0.5/0.701) * (Rgamma - Y) These scale factors limit the excursion of EACH colour difference component to -0.5 .. +0.5 with respect to unity Y excursion: 0.886 is just unity less the luma ...

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 ...

 

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