C1@Plug-in software product by Waves, Ltd., for compression and miscellaneous dynamics processing. Available for various plug-in architectures.@Cache, L2 Cache@Any small amount of computer memory, used to increase the efficiency of data transfers. It acts as a temporary repository, from which information can be retrieved more quickly than the original source. Caches may be dedicated memory components, in the form of "Disk Caches" incorporated into some disk drives. In other cases, a smaller section of the computer's main memory may be reserved for use as a cache (for example, the Macintosh's "Disk Cache" control panel). A "Memory Cache" is an even smaller, high-speed memory component. It retains the data which has most recently been stored or retrieved from the computer's main RAM; access time to data found in this cache is much faster than the RAM itself. A "Level 1" memory cache is incorporated into the CPU chip (Pentium, 486, PowerPC), providing access times on the order of 9 nanoseconds, compared to about 70 nanoseconds for typical RAM. "Level 2" or "L2" caches are cards with high-speed SRAM chips, used as a "secondary" cache. They communicate with the CPU via a special slot on the motherboard of the computer (Mac IIci, vx, fx, PowerMac 8100). See also Disk Cache.@Calibration Tool@Digidesign software utility, which facilitates adjustment of input and output levels of certain Pro Tools audio interface models to the mixing console being used. Fine adjustments of these levels can be made using the Trim controls on the front of supported audio interfaces. This adjustment also allows the user to fine-tune the desired amount of Headroom above nominal gain level.@Capacitor@An electrical device consisting of two or more conducting plates separated by some insulating material, with the ability to store an applied electrical charge. Same as Condenser. See also Condenser Microphone.@Capture Button@Digidesign term. In Pro Tools and Sound Designer II, when specifying SMPTE locations (for the entire soundfile or session, for specific regions), the SMPTE timecode dialog features a button labeled Capture. Pressing this button registers the incoming SMPTE timecode address for that moment, automatically inserting it into the numerical field used for indicating SMPTE values.@Capture Region@Digidesign term. A function which permits assigning a convenient name to the current selection of audio within a file, in order to thereafter address this segment by the Region name. See Region.@Cardioid Microphone@The most common type of unidirectional microphone, whose directional response pattern to incoming sound is more sensitive towards the front, with -6 dB reduction at the sides (90û), while rejecting sounds coming from the rear (180û off-axis). The polar response pattern of these microphones looks like a heart shape (upside-down), hence the name cardioid. Cardioid microphones are very useful in sound reinforcement, because their good off-axis rejection helps avoid feedback provoked by reflected sound or onstage monitors. They can be positioned to minimize leakage from other instruments. Even more directional variants are supercardioid (-8.7 dB at 90û) and hypercardioid (-12 dB at 90û)microphones.@Carrier@A waveform whose amplitude, frequency or phase (AM, FM or PM) is being modulated by another signal. See also FM Synthesis, Frequency Modulation, Amplitude Modulation.@Cart@Cartridge. Broadcast industry term for endless-loop magnetic tape cartridges, extensively used for on-the-air playback of radio commercial spots, station identifications, etc. Several cart standards are defined by the NAB, the National Association of Broadcasters. NAB cart machines have no erase heads; the carts must be erased using a degausser (demagnetizer). When the Record button is pressed, a special 1KHz "Stop" tone is put onto tape, which allows the mechanism to always stop at this point after playback, and therefore be prepared for instant playback the next time it is needed.@Catalog Code@Part of the Red Book standard for audio CDs, the Catalog Code contains information pertaining to the entire CD. Permits encoding the UPC/EAN barcode (Universal Product Code) into the Q subcode channel of the finished CD. See also Red Book, PQ Code.@Catch@Emagic Logic Audio term. Function for making the section of the song currently displayed in the window reflect the current song position.@CBR, VBR@Abbreviations for Constant Bit Rate, Variable Bit Rate. "Bit Rate'" describes the rate at which data passed through, and is measured in kbps (kilobits per second). The terms CBR and VBR generally come up in the context of MP3 audio on the Web, to describe how the compression method encodes the audio for playback (through the "decoder" algorithm in the MP3 Player software).
CBR is the more established method: Density of the data is maintained at a consistent level throughout the MP3 file, even if this level may be more than strictly necessary in some places (for example, silences) - or less than ideal in other sections. CBR encoding does have the advantage of producing predictable file sizes, and simpler programming for the software decoder.
VBR actually varies the density of the information (the number of kilobits per second of audio) according to the requirements of the material itself. There may be spots where space is saved by not using more data than necessary to represent a given section - and other higher kbps "spikes" for sections that require a higher bit rate to sound best.
At the moment, many feel that CBR is a safer choice for widespread compatibility, as some MP3 "Players" don't yet properly support files created with VBR compression. See also MP3. @CD, Compact Disc@A popular digital audio medium introduced in 1982. A low-intensity laser beam is reflected by a series of pits on the metallized plastic substrate of a rotating disk, and registered by an optical pickup. The pits are arranged along a spiral path extending outwards from the center; the relative length of the pits and the spaces between them ("land") is varied, producing changes in reflectivity by which the ones 1's and 0's of the digital data are encoded. CD rotational speed varies from about 3.5 to 8 revolutions per second, according to the location being read on the disk, which is either 120mm (standard size, about 4.74 inches) or 80mm in diameter (CD-3, or "CD single"), and 1.2 millimeters thick. Currently, the standard format for Red Book audio CDs (also known as CD-DA) is 16-bit audio with a 44.1 kHz Sampling Rate, on 63 or 74-minute discs. Eight subcoding channels, P through W, are interleaved with the audio data (only channels P & Q are actually used by audio CD players). Channel Q in particular is used for most track indexes, catalog codes, etc., and CIRC error detection/correction on audio CDs. See also Red Book, PQ Code, CD-ROM.@CD+G@Compact Disc + Graphics. A CD format which, along with standard digital audio, encodes computer graphics (and sometimes compressed video) into subcode channels R through W (in 25Mb worth of data storage space, which is otherwise unexploited on standard audio CDs). Disks in CD+G format have been used for some karaoke CD players, to display lyrics in the form of text on a standard television monitor (NOT full-motion video, as is the case with karaoke laserdiscs). Aside from this, the CD+G has not achieved as much popularity as Enhanced and Mixed Mode CDs. See also Compact Disc.@CD-3, CD Single@Smaller CD format, 80 millimeters in diameter (approximately 3 inches) instead of the standard 120mm. Holds a maximum of 20 minutes of audio. Most current CD players feature concentric rings in their disc drawer, accommodating either CD size. See also Compact Disc, Red Book.@CD-DA@Compact Disc Digital Audio. An ordinary audio compact disc, as defined by the Red Book standard. The original, proper name for this data format used for storing digital audio on compact disc, more commonly known as "Red Book". See Compact Disc, Red Book.@CD-E@CD-Erasable. A proposed standard for erasable compact discs, being developed by an alliance of manufacturers including Sony and Philips. CD-E drives are based on Phase-Change technology, and will permit erasing tracks. A laser is used to heat spots along a groove in the substrate of a disc, changing their structure from amorphous to crystalline. This creates changes in reflectivity, by which the binary data is encoded. Commercial CD-E drives are projected to reach the market in 1997. See also CD.@CD-I, Green Book@Compact Disc Interactive. A compact disc multimedia format, optimized for high-speed interaction in real time with applications incorporating digitized audio, video (MPEG), and graphics, as well as text. A standalone CD-I player is required, with specific controllers and decoder chips for each data type; its audio and video output is connected to an ordinary television set. (CD-I players can also play back ordinary Red Book audio tracks.) Most digital audio data used in CD-I applications is compressed (through ADPCM, 8- or 4-bit Adaptive Delta Pulse Code Modulation) at 3 different compression quality levels: Hi-Fi, Mid-Fi, and Speech. Compressed audio occupies less disk space, and allows faster access and processing, which facilitates efficient use of multiple sound resources in the high-speed, interactive CD-I environment. The CD-I format was developed by Philips in 1987 and publshed in a book with a green cover; it is similar to Yellow Book Mode 2, Form 1, and holds up to 650Mb of data. The first CD-I players were shipped by Philips in 1991, Philips is still the only major manufacturer strongly supporting this standard, more popular in Europe than elsewhere. See also ADPCM, CD-ROM, Yellow Book.@CD-R@Compact Disc-Recordable, also known as CD-WO, Compact Disc-Write Once. Format for user-recordable compact discs (either audio CDs or CD-ROMs). The blank, recordable CD discs used on CD-R units use the same polycarbonate base as an ordinary CD, but instead of the pre-stamped aluminum substrate, they feature a layer of organic dye, with an extremely thin gold coating. The laser pulses from the Write head of the CD-R unit create mounds along the spiral data path on the disk's surface, which serve the same purpose as the pits on prerecorded CDs. CD-R discs are pre-grooved to ensure compatibility between recorders/players, and also include a partially prerecorded lead-in area with a Table of Contents (TOC), indicating the start positions of the primary data areas on the disc. Blank CD-R discs are available in 63-minute (550 MB), or 74-minute (650 Mb) capacities. The term CD-R is also used to refer to the CD recording device itself. For professional pre-mastering of Red Book audio CDs, CD recorders must be able to write the entire disc in one "burn", Disc-at-Once mode. Track-at-Once mode (commonly used to write multisession discs) turns off the laser between tracks, writing "links" between them; some CD players and industrial duplication equipment will interpet these links as errors. See also Orange Book, Red Book, CD-ROM, MasterList CD.@CD-ROM@Disk format using compact discs to store up to 650Mb of data (audio CDs can hold up to 782Mb). As the acronym implies (CD Read-Only Memory), you canÕt create or write onto these disks yourself (unless you have a CD-R, CD recorder, attached to your computer). The Yellow Book CD-ROM specification includes data disk volumes in Macintosh HFS, ISO 9660, High Sierra and other audio-video formats. CD-ROMs are extremely useful for distributing very large amounts of information, such as audio sample libraries, sound effects, multimedia audio/video and interactive games. To use them, you will need a CD-ROM drive on your computer. These drives usually can also play back audio CDs. There are ways to directly lift the digital audio off the CD and onto your hard disk for editing in various audio programs. See also CD, Yellow Book, Orange Book, Photo CD, CD-I, 2x, 4x.@CDDI@Copper Distributed Data Interface. A local networking standard similar to FDDI (see definition), which instead of fiber optics uses less-costly copper cabling to achieve similar data transmission speeds (100 megabits per second), over shorter distances. Supported by several digital audio workstation manufacturers.@CDEV@Macintosh file type. Acronym for Control Panel Device. See Control Panels.@CDXA, CD-ROM/XA, XA@Compact Disc Extended Architecture. Also known as CD-ROM-XA. Common term for Yellow Book Mode 2, a standard CD format which interleaves data for audio, video, graphics and text, for synchronized "multimedia" playback. Kodak's Photo CD format ("Beige Book") is a subset of CDXA, therefore all CDXA-compatible CD-ROM drives can also accept Photo CD discs. See Yellow Book, CD-ROM, Photo CD.@Cent@Abbreviation for Centitone. A unit for measuring musical intervals. Each cent represents one-hundredth of a musical semitone. There are 12 semitones (chromatic half steps) in each octave, therefore an octave is equal to 1200 cents. Since musical intervals are logarithmic (proportional) rather than arithmetic, the absolute frequency change implied by a given detuning in cents will vary proportionally to the frequency of the original tone. Cents are the units used in the "fine tuning" parameter of many synthesizers and pitch shifters. Cents are a convenient way to describe pitch intervals, used to form the degrees of a musical scale in alternative intonation systems (temperaments), by comparing them to the equal-tempered scale which is commonly used in music derived from the European tradition.@CGA@Color Graphics Adapter, an early IBM standard for color PC monitors, 320x200 in 4 colors. Now considered obsolete, and not supported by most current audio and MIDI programs.@Channel@Generally, a discrete audio path, data path, or communications line.
On traditional audio consoles, a channel is an audio input, with its corresponding level adjustments, EQ and routing assignments.
In the MIDI environment, Channel Events are specific to one data channel among a total of sixteen, for example Note On events. (Information for all 16 MIDI channels is transmitted on the same cable. However, channel-specific events are "flagged"; a voice or device which is not "tuned" to the corresponding channel ignores these messages.) See MIDI.
A Pro Tools Channel refers to actual physical inputs & outputs on the audio interfaces, each unit providing four (442) or eight (888/882) channels of analog input/output, plus S/PDIF or AES/EBU digital input/output.@Chase@MIDI term: Refers to the capability of a MIDI sequencer to correctly set the values of MIDI controllers such as modulation, program change, etc., when playback is initiated from any point within the sequence, by looking backwards in the file to determine the previous positions of these controllers.
Audio Synchronization: When one audio or video transport "chases" another (because it is "slaved" to the master transport, usually through SMPTE timecode), it looks at the received timecode reference, rewinds or fast forwards its transport to the appropriate location, and begins playback; a process which may take several seconds. This is called Chase Lock. (A MIDI sequencer, or the Pro Tools software, is doing the same thing when it is "online", or synchronized to an external timecode source. But of course, there's no tape to rewind or fast forward!) See also SMPTE TimeCode.@Check box@Emagic Logic Audio term. A small box. Placing a check in it (by clicking on it) activates an option.@Chooser@Apple Macintosh term. A program which appears under the "Apple" menu, which allows the user select printers and network file servers. The Chooser is also where you turn AppleTalk networking on/off in order to make the Macintosh printer port available for MIDI or machine control.@Chorus (musical form)@In popular song forms, the term chorus is often used as a synonym for Refrain, a set of phrases or melodic motifs, repeated between Verses. Musically, it is usually a "B" section which appears in contrast to an "A" section. In jazz improvisation, the term Chorus sometimes applies to each repetition of the complete chord progression, an entire song form. See also "Chorus" an audio processing effect. See also Bridge.@Chorusing, Chorus (effect)@Signal processing effect that applies a series of short, continuously varying delays to produce slight pitch-shifts, which when combined with the original signal add fullness and texture to a sound. The name refers to the way an ensemble of voices or instruments in unison sounds richer than a solo voice, due to minute differences in intonation and timing. See also Delay.@CHRP, PreP@Common Hardware Reference Platform, PowerPC Reference Platform. CHRP is a proposed industry-standard computer architecture developed jointly by Apple, IBM and Motorola, using the the PowerPC processor (CPU). CHRP was based on IBM's PowerPC Reference Platform, with numerous modifications; in particular it supports Apple's Macintosh OS (operating system), while PreP does not. See also PowerPC, 680X0.@CIRC, Cross-Interleave Reed-Solomon Code@Standard type of error correction used on audio CDs. Two different block error detection codes, physically separated among the digital data by both interleaving and delay methods, are used as complementary error detection; one can be used to point to errors in the other. See Compact Disc, Red Book.@Circle of Digi@A location on the Cool School Interactus Volume 1 CD-ROM, by Cool Breeze Systems, a radial menu from which the user can navigate to various software modules.@CISC@Complex Instruction Set Computer. The standard type of microprocessor design used for the CPUs of most personal computers, before the appearance of the RISC-based PowerPC processor. The entire Motorola 680X0 family of processors, and the Intel 80X86 family, are CISC designs. See also RISC, 680X0, PowerMac.@Click Track@An audio track where a percussive sound has been recorded, serving as a metronome. Used to assist musicians in matching precise, predetermined musical tempos during the recording process.@Clipboard@In the Macintosh operating system, when any data is cut or copied, it is kept in an area of memory known as the "ClipBoard", until it is subsituted by something else which is cut or copied, or until the computer is shut down. In this manner, identical data can be pasted repeatedly.@Clipping@A type of distortion where the top of a waveform is cut off (clipped). In other words, the waveform is squared off by being unable to reach its maximum excursion, due to some limitation of the device attempting to reproduce or record the signal. Usually caused when the amplitude of the signal overloads an input or output stage of an audio device, or exceeds the maximum allowed recording level of a recorder.@Clock@A source of hardware-level timing information, especially important when two or more devices must be synchronized. Also, the timing crystal in the CPU chip of a digital device, whose oscillation speed or Clock Rate is measured in megahertz (MHz). A Sample Clock also controls the Sample Rate of a digital audio device. See also Word Clock, House Sync.@CLV@Constant Linear Velocity. A disk drive mechanism which adjusts rotational speed according to the position of the read/write head (unlike phonograph records and some laserdiscs, which maintain a constant rotational speed, regardless of position, known as Constant Angular Velocity, or CAV). In CLV discs, data on the larger, outer tracks passes by the head at the same rate and density as on the smaller, inner tracks, therefore they hold more data. All compact disk drives are based on the CLV technique (audio CDs, CD-ROMs, CD-I, etc.). Videodisc players based on CAV designs are better able to address individual frames of video. However, due to their lesser data density on outer tracks, they hold a smaller total amount of information. See also Compact Disc.@CMX@A particular type of Edit Decision List used for video editing. Based on the industry-standard CMX file format for EDLs, which can be saved/exported as a text file to disk. This format was introduced with the CMX 340X and 3400 microprocessor-based offline video edit controllers from CMX, Inc., a company created by CBS Labs and Memorex. See EDL.@Coaxial@1) A type of cable where a central conductor (a single, solid wire) is surrounded by an insulator, which in turn is surrounded by an outer conductor forming a cylindrical shell; both conductors therefore share the same axis. Also, 2) a coaxial loudspeaker design is one where a smaller high-frequency unit is concentrically mounted inside a larger woofer, therefore sharing the same axis.@Codec@Coder/Decoder. A software algorithm for audio or video data compression and decompression, also a hardware component used for the same purpose. A Codec encodes digitized data to reduce its size for transmission or storage; it is again decoded at the receiving end, or during playback. (Not to be confused with gain compression, an audio signal processing technique!) Almost all codecs are "lossy" to some degree; some of the information or image quality in the original is lost as a result of the data compression process. Two types of codec algorithms for audio are included in Microsoft's Windows 95 operating system: IMADPCM, a music-oriented compression method achieving reductions of 4:1, and TrueSpeech, a voice-oriented method providing 15:1 reduction of audio data. (Common digital video codecs include Cinepak, MPEG, YUV component, etc.) See ISDN, MPEG, QuickTime.@Comb Filtering@A characteristic type filtering effect produced by phase cancellation, which alters or misrepresents the orginal sound source; especially when caused by the interaction between various out-of-phase versions of the same waveform. A number of null points (dips, or notches in the frequency response) are spread out over a relatively wide region of the audio spectrum, at these points acoustical energy present in the original waveform is attenuated (while at other points frequencies are reinforced). (When viewed graphically as a frequency response curve, the closely-spaced notches of attenuation resemble the teeth of a comb.) See also Phase Cancellation.@Combination Tones, Sum and Difference Tones@Perceptive phenomenon, created by two loud tones which differ by more than about 50Hz. The ear produces additional tones, corresponding to the sum and/or difference between the two frequencies. Difference tones are most notable, especially when the frequency of the difference tone is lower than either of the two original frequencies. (Sum and Difference tones are also the "sidebands" produced by the modulation of a carrier wave in AM radio.)@Comp Track, Composite Track@An audio track composed of segments copied from other tracks, for instance to combine the best portions of various recorded takes of the same performance. Used to obtain an ideal overall performance, to open up the original tracks for further recording, or merely to simplify the mixdown.@Compact Audio@Digidesign Pro Tools command. A function which reduces the size of an audio file on disk, by eliminating all portions of the file which aren't actually being used by the current Session document. There is a provision for leaving a certain amount of Padding before and after the audio regions that are retained, so that small adjustments of their start/end points will still be possible. Keep in mind that this is a "destructive" function; it permanently eliminates the "excess" audio from your disk!@Compander, Compansion, Companding@Various methods that compress the amplitude of a signal at one end of an audio chain, and later expand it to reproduce the original input signal. Companding is often used as a form of noise reduction in analog recording: A compressor restricts the dynamic range during recording, obtaining a higher recorded level for better signal-to-noise ratios. During playback, the compressed recording is expanded to restore its original dynamic range, which also reduces the level of tape hiss, particularly during quiet passages. Companding is also used in many wireless microphone systems, as a means of overcoming the dynamic range restrictions of their transmission methods. It is also used in some low-resolution digital delay circuits. The process is also known as Compansion. See Dolby, dbx, Compressor, Expander.@Composite Video@A video signal which combines the information for all three additive color components (red, green, blue; RGB) which comprise a video image into a single "chroma" value, plus a "luminance" value representing the brightness, or saturation of each pixel. The standard format for consumer television; as opposed to component video, which processes each of the three colors separately. (Sony Betacam and D1 video formats record information for each color separately; computer monitors and graphics cards also send information for each color on a separate cable. See also RGB, Betacam.@
