Glossary
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## Glossary

AIFF

  Audio Interchange File Format. A standard audio format for SGI workstations.

AIFF-C

  Audio Interchange File Format with Compression. A standard audio format for SGI workstations.

analog

  A video signal in which a continuously variable voltage or current (rather than a set of numbers) represents the value of a pixel.

audio

  The sound portion of a program, or, a track recorded on a videotape which contains sound, music, or narration.

AVI

  AVI stands for “Audio Video Interleaved” and is Microsoft's file format for movies.

bit rate

  The bit rate is the number of bits used to store one second of a digital video and/or audio sequence.

black burst

  A video signal which has no luminance or chrominance components (except burst), but contains all other elements of a video signal. Black burst is the most common reference signal used for timing.

brightness

  Same as the luminance signal (Y), which carries information about the amount of light at each point in an image.

byte order

  Numbers that are more than 8-bits long are stored as consecutive bytes. The byte order indicates whether the bytes are stored most significant to least significant (big endian) or vice versa (little endian). The concept is analogous to storing the digits in 100 as 1-0-0 or 0-0-1.

B-Y

  Blue minus Y. B-Y signals are used in analog component videotape recording formats.

CCIR

  Comite Consultatif International des Radio-Communications. An organization formed by the United Nations to regulate international communications.

CCIR-601

  CCIR recommendation number 601, which sets a standard of encoding parameters for digital television.

cent

  In the world of audio, a cent is a unit of pitch measurement corresponding to one one-hundredth of a semitone.

channels

  Independent streams of audio. For example, monophonic recordings contain a single channel of audio whereas stereo recordings contain two channels, left and right. The number of channels affects the file size; stereo files are twice as large as mono files.

chroma key

  The process of using a video signal's color characteristics to do the “cutting” of a foreground image into a background image. Allows the weatherman to appear to stand in front of a satellite image.

chrominance

  The color information in a composite video signal. Describes hue and saturation of a picture, but not the brightness. The signals R-Y and B-Y are examples of chrominance information.

CinePak

  A codec implemented for both QuickTime and AVI (Microsoft windows standard for desktop video). It is an asymmetrical codec, meaning that movies encoded with it take a long time to compress, but decompress very rapidly at playback time. CinePak was originally created to compress movies for rapid decompression and playback off of CD-ROMs.

clip

  Refers to a media file, especially when using a digital audio or video editing program.

codec

  A codec is a piece of software that is capable of both compressing and decompressing movies.

color correction

  A process in which the color elements in a video image are changed by electronic means. Color correction is almost always used in conjunction with high-end film-to-tape transfers.

component video

  Video whose original elements are retained separately rather than combined into a single signal (composite video). Separating the color components yields a signal with a higher color bandwidth than that of composite video.

composite video

  An signal consisting of combined luminance and chrominance components. Composite video can be either analog or digital.

compression

  The coding of data to save storage space or transmission time. Although data is already coded in digital form for computer processing, it can often be coded more efficiently (using fewer bits).

crop area

  The area of the image that will be captured. The Capture tool marks the crop area with a red box. You can change the crop area by adjusting the size and placement of this box.

demultiplexing

  Demultiplexing is extracting part of a movie file, in order to create a single audio or video file. For example, extracting an MPEG audio file from an MPEG movie file (that contains audio and video).

desktop

  The screen background. By default, several icons are placed on the desktop: a folder icon representing your home directory, a dumpster icon, several application icons, and an icon for each peripheral you have installed. You can place other icons on the desktop so that you can access them more easily.

  In this way, the desktop is similar to an actual office desk. For example, on your desk, you might have a telephone, a container of pens and pencils, and a stack of folders or notebooks related to the projects on which you're currently working, Other items that are used less are stashed away in desk drawers.

device

  In relation to the Audio Panel, the term device refers to an internal device that your system uses to communicate with external equipment. By using Audio Panel to select a default input and output device, you are setting the default audio signal path into and out of your system. See Figure B-1 in Appendix B for a visual example.

digital

  Component signals in which the values for each pixel are represented by a set of numbers.

edit line

  A thin line in the waveform. Use this to mark the location at which you want to begin playing and recording or copying and inserting audio.

file browser

  Most applications display a file browser when you choose the “Save” or “Save As...,” or “Open...” command. The file browser makes it easy for you to save a file in a particular directory, by entering a pathname or by simply adding a new filename on the end of the path in the pathname field. For example, the pathname in the file browser might be `/usr/people/joe`; to save your file in `/usr/people/joe`, add the filename after “`joe`,” so that it looks like this: `/usr/people/joe/filename.` You can also use the file browser to select a file or directory you want to open.

flicker filter

  Flicker filter eliminates the TV monitor flicker that may occur when a movie includes computer-generated graphics, such as those created by including a 3D filter in your movie.

format

  The general configuration of signals used for equipment interconnection.

four-channel

  Audio containing four channels of separate information for four speakers operating simultaneously. Often used in front-left, front-right, rear-left, and rear-right configuration, but may be found in other configurations. Sometimes referred to as quadraphonic audio.

frame

  In video, conceptually the same as one frame of film, except that a video frame is digital. In NTSC, 30 frames comprise a second of video. In PAL, 25 frames comprise a second. In both standards, two fields comprise a frame. Note that in film, 24 frames comprise a second.

frame rate

  The number of frames captured or displayed per second. A lower frame rate produces a less fluid motion and saves disk space. A higher setting results in a fluid image and a larger movie file.

full frame

  This term refers to the way the video image was captured. Different tools for capturing video store the captured video fields differently. A full frame occurs when one image equals two fields alternated inside the image file to produce one full frame.

gain

  Boosting the amplitude of the audio signal, perceived by the human ear as an increase in volume.

General MIDI

  A standard subset of MIDI rules designed to ensure compatibility among different instruments. General MIDI instruments all store sounds in the same memory areas, and always use MIDI Channel 10 for precussion. They can all play at least 16 sounds at once, and have at least 24-note polyphony.

genlock

  Video output timing is locked to a selected source.

Hi-8mm

  An 8mm recording format developed by Sony; accepts composite and S-Video signals.

icon view

  The window you see when you open a folder (directory) icon. It displays the files, folders, and applications that the directory contains.

interlaced

  An analog video signal consisting of alternating odd and even fields. The two fields are superimposed to create a single frame. See also interlaced odd and interlaced even.

interlaced odd

  An analog video signal in which the first field in a frame starts on an odd line, and thus the second field starts on an even line. NTSC recorders create interlaced odd signals. See also interlaced and interlaced even.

interlaced even

  An analog video signal in which the first field starts on an even line. PAL recorders create interlaced even signals. See interlaced and interlaced odd.

internal

  Video output timing runs independent of any inputs. Should be used when no video input is available.

JPEG

  JPEG is a compression standard developed by the Joint Photographic Experts Group. JFIF is the corresponding file format standard for storing a single JPEG-compressed image in a file. JPEG is a lossy compression scheme designed for still images, but can be used for movies. For example, QuickTime, SGI Movie, and OMFI file formats all are capable of storing JPEG-compressed video data inside movies. Software JPEG compression results in a file that is reduced to anywhere from 2 to 100 times its original size. JPEG is typically used to compress each still frame during the editing process, with the intention being to apply another type of compression (such as MPEG) to the final version of the movie. JPEG works better on high-resolution, continuous-tone images such as photographs, than on crisp-edged, high-contrast images like line drawings.

key frame

  In movie compression, the key frame is the baseline frame against which other frames are compared for differences. The key frames are saved in their entirety, while the frames in between are compressed based on their differences from the key frame. In Media Convert, for example, if you set the Key Frame option to 10, every 10th frame will be a key frame. This translates to a higher level of compression and playback speed than a movie that was compressed with the Key Frame option set at a lower number. However, if you want to stop a movie in different places, in order to view different frames, a lower Key Frame option will provide better stop and start viewing.

lossless

  A video/image compression method that retains all of the information present in the original data.

lossy

  A video/image compression method that doesn't preserve 100% of the information in the original data

luminance

  The monochrome component of a color video signal. Called the “Y” components as in R-Y and B-Y.

menu button

  A button that reveals a popup menu. Place the cursor over the button; then press the left mouse button.

MIDI

  MIDI stands for Musical Instrument Digital Interface. It is a standardized digital language (and hardware specification) that enables computers and a wide variety of electronic musical instruments/devices to communicate with each other.

MIDI channel

  Any one of 16 pathways that the MIDI standard provides for the transmission and reception of data. The number of the channel over which MIDI data should be transmitted is specified by a number in the MIDI data stream.

MIDI controller

  A MIDI controller is any piece of hardware or software that transmits MIDI data.

MIDI device

  A product that responds to or generates MIDI data. Common examples of MIDI devices are modern keyboards and drum-pads, which include MIDI `IN`, `OUT`, and `THRU` ports.

MIDI interface

  In using Silicon Graphics software MIDI tools, the word MIDI interface refers to that with which the MIDI software communicates. MIDI interface could refer to the workstation's internal synthesizer or an external piece of equipment.

MIDI interface adapter

  A hardware device that lets a computer communicate with MIDI devices such as instruments and synthesizers.

MPEG

  MPEG is a compression standard developed by the Motion Pictures Expert Group. It is most often used for CD-ROM and World Wide Web authoring material. MPEG-1 typically reduces the data size of an uncompressed file by a factor of 100. It is a lossy algorithm that is capable of producing higher compression ratios than both JPEG and MVC1. MPEG is well suited for video publishing, where a video is compressed once and decompressed many times for playback.

multiplexing

  Multiplexing is combining one audio file and one video file to create a movie file that contains both audio and video. For example, combining an MPEG audio file with an MPEG video-only file to create an MPEG systems file.

MVC1

  MVC1 (Motion Video Compressor 1) is a Silicon Graphics proprietary algorithm that is a good general-purpose compression scheme. MVC1 typically reduces data size by a factor 5. It is a color-cell compression technique that works well for movies, but can cause fuzzy edges in high-contrast animation. MVC1 is a fairly lossy algorithm that does not produce compression ratios as high as JPEG. An advantage of MVC1 is that software-only playback is relatively fast.

MVC2

  MVC2 (Motion Video Compressor 2) provides results similar to MVC1 in terms of image quality. MVC2 compresses the data more than MVC1, but takes longer to perform the compression. MVC2 typically creates a file that's approximately 20 times smaller than an uncompressed file. Playback and decompression is faster than MVC1, because there is less data to read.

non-interlaced

  The video signal created when frames or images are rendered from a graphics program. Each frame contains a single field of lines being drawn one after another. See also interlaced.

NTSC

  A color television standard or timing format encoding all of the color, brightness, and synchronizing information in one signal. Used in North America, most of South America, and most of the Far East, this standard is named after the National Television Systems Committee, the standardizing body that created this system. NTSC uses a total of 525 horizontal lines per frame, with two fields per frame at 262.5 lines each. Each field refreshes at 60 Hz (actually 59.94 Hz).

PAL

  A color television standard or timing format developed in West Germany and used by most other countries in Europe, including the United Kingdom but excluding France, as well as Australia and parts of the Far East. PAL uses a total of 625 horizontal lines per frame. Each field refreshes at 50 Hz. PAL encodes color differently from NTSC. PAL stands for Phase Alternation Line or Phase Alternated by Line, by which this system attempts to correct some of the color inaccuracies in NTSC. See also NTSC.

PAL-M

  A version of the PAL system used only in Brazil.

pathname

  The list of directories that leads you to a specific file or directory in the file system. For example: `/usr/people/jane/test.results` is a pathname. Note that directories contain other directories and files. The root (/) directory is the original directory, which all other directories reside in.

pixel

  A “picture element”; images are made of many tiny pixels. For example, a 13-inch computer screen is made of 307,200 pixels (640 columns by 480 rows).

pixel aspect

  The pixel aspect describes the shape of each pixel. Most images are made of square pixels. Another possible pixel aspect is “CCIR 601/525,” if the video source for your images was a CCIR 601 video device (with NTSC timing).

preset

  A MIDI preset is a digital sound specification for MIDI instruments. It contains data that determines what type of sound (instrument) to use and detailed information about any oscillators, filters, and envelopes that define the sound. For example, if you select the Harmonica preset, and then play a few notes with the MIDI Keyboard , the sound of the notes will resemble the sound of a harmonica. See the `synthpreset(4)` man page for more details.

project

  When using Sound Track, the audio composition you are working on is called a project. A project contains more than one track of sound. For example, it may have a track that contains voice and a track that contains music. The actual contents of a project are a master project file, associated sound files, and waveform plotting files. You create a project so that you can work with more than one sound clip at a time. Once your project is complete, you can export it as a single sound file with all clips mixed together.

QuickTime

  A desktop video standard developed by Apple Computer. QuickTime Animation was created for lossless compression of animated movies and QuickTime Video was created for lossy compression of desktop video.

QWERTY

  A name for the standard computer keyboard, named by first six keys from left on the top alphabetic row.

reverberation

  The simulation of natural reverberation (such as the echoing caused by sound reflection), in order to add a sense of spaciousness and ambience to a sound.

RGB

  Red, green, and blue color signal components.

RLE

  RLE stands for Run-length Encoding. RLE is also known as Animation, and was created specifically for compression and decompression of animation clips. It is best used as a lossless codec of sequences of drawn or rendered still images.

R-Y

  Red minus Y. One of the color difference signals of the analog component video format.

sample rate

  The speed at which audio samples are recorded and played back. This is analogous to video and film frame rates. Higher sample rates give higher audio quality at the expense of larger audio file size. Lower sample rates save disk space but result in poorer audio quality. Typically, 8 kHz is fine for human voice recording. Audio CDs are recorded at 44.1 kHz, and audio DATs are recorded at 32, 44.1, or 48 kHz.

sample width

  The number of bits used to represent a single sample of audio data, typically expressed in multiples of 8-bits (8, 16 or 24). Larger widths allow for greater dynamic range and precision, both of which influence audio quality.

SCSI

  Small Computer System Interface, pronounced “scuzzy.” SCSI is a high speed input/output specification for small computers. DAT drives and CD-ROMs are examples of SCSI devices—they use the SCSI protocol to communicate with the system.

sequencer

  A digitally-based device used to record, edit, or play MIDI data sequentially.

slave

  Video output timing is determined from video input timing and internal signal path delays.

SMPTE

  Society of Motion Picture and Television Engineers. SMPTE sets standards for the professional film and video industry.

software synthesizer

  Refers to the MIDI synthesizer that is included in your system software. It is an internal program that can be controlled and monitored with programs like MIDI Keyboard. For example, when you use Sound Player to play a MIDI file, what you are hearing is the software synthesizer. See the `midisynth(1)` man page for more information.

source

  The tape or device from which a video or audio signal originates.

SoundFont2

  The SoundFont Compatible File Format was developed by E-muŽ Systems, Inc. It consists of a complex RIFF header containing large amounts of information about the sound samples, plus an imbedded, contiguous block of binary data representing the sound samples. See the `sf2(4)` man page for more information

split fields

  This term refers to the way the video image was captured. Different tools for capturing video store the captured video fields differently. A split field occurs when one image equals two fields, which are stored as two separate pictures, one for each field; one stacked on top of the other.

standard

  The specific signal configuration, composed of reference pulses and voltage levels, which describe the input and output requirements of a video signal.

S-VHS, S-video
systems

  In the world of MPEG compression, systems refers to a movie file containing interleaved MPEG audio and MPEG video. Systems is short for the technical compression term systems bitstream.

time indicator

  Several of the digital media applications have a time indicator, which is a vertical line that represents the current time within a movie or audio composition. As the movie or audio is played, this line moves. The application's time display also reflects the current time, which is the point at which the time indicator is positioned at any given moment.

track

  When using an audio or video editing program, tracks are what make it possible to combine layers of media files, and are organizational tools for the digital editing process. A tracks contain a sequence of one or more clips.

velocity

  In music, the speed at which a note has been pressed or released. Velocity can alter the volume and/or brightness of a sound.

video

  The picture portion of a program, or, the picture track recorded on a videotape. A videotape typically contains one video (picture) track, up to four audio (sound) tracks, and one timecode track.

VINO

  Video In No Out. This is the standard video capability of an Indy workstation. The workstation will accept video input but does not create video output. Video input can be saved to disk but cannot be output to videotape.

wipe

  A transition whereby one portion of a video image is replaced with another, using a switcher-generated pattern or effect.

Y

  The luminance signal in a component set.

Y/C

  The S-VHS and Hi8 component video standard. Video is separated into luminance (Y) and chrominance (C) signals, but is carried on a single cable.

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