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Multimedia

This glossary contains definitions for terms used in the Windows Multimedia documentation.

Adaptive Differential Pulse Code Modulation (ADPCM)

An audio-compression technique.

ADPCM

See Adaptive Differential Pulse Code Modulation (ADPCM).

break key

In Media Control Interface (MCI), a keystroke that interrupts a wait operation. By default, MCI defines this key as CTRL+BREAK. An application can redefine this key using the MCI_BREAK command message.

CD-ROM extended architecture (CD-XA)

An extension of the CD-ROM standard that provides for storage of compressed audio data along with other data on a compact disc. This standard also defines the way data is read from a disc. Audio signals are combined with text and graphic data on a single track so they can be read at virtually the same time.

channel

A method, provided by Musical Instrument Digital Interface (MIDI), for sending messages to an individual device within a MIDI setup. There are 16 MIDI channel numbers. Devices in a MIDI setup can be directed to respond only to messages marked with a channel number specific to the device.

channel map

A channel map, provided by the MIDI Mapper, that can redirect Musical Instrument Digital Interface (MIDI) messages from one channel to another. See also MIDI Mapper, Musical Instrument Digital Interface (MIDI).

chunk

The basic building block of a Resource Interchange File Format (RIFF) file, consisting of an identifier (called a chunk identifier), a chunk-size variable, and a chunk data area of variable size.

command message

In Media Control Interface (MCI), a symbolic constant that represents a unique command for an MCI device. Command messages have associated data structures that provide information a device requires to carry out a request.

command string

In Media Control Interface (MCI), a null-terminated character string that represents a command for an MCI device. The text string contains all the information that an MCI device needs to carry out a request. MCI parses the text string and translates it into an equivalent command message and data structure that it then sends to an MCI device driver.

compact disc – digital audio (CD-DA)

An optical data-storage format that provides for the storage of up to 73 minutes of high-quality digital-audio data on a compact disc. Also known as Red Book audio.

compact disc – read-only memory (CD-ROM)

An optical data-storage technology that allows large quantities of data to be stored on a compact disc.

compound device

A Media Control Interface (MCI) device that requires a device element, usually a data file. An example of a compound device is the MCI waveform audio driver. See also device element.

control change

See MIDI control-change message.

device element

Data required for operation of Media Control Interface (MCI) compound devices. The device element is generally an input or output data file.

division type

The technique used to represent the time between Musical Instruments Digital Interface (MIDI) events in a MIDI sequencer.

file element

A complete file contained in a Resource Interchange File Format (RIFF) compound file.

FM synthesizer

See frequency modulation (FM) synthesizer.

FOURCC (Four-Character Code)

A code used to identify Resource Interchange File Format (RIFF) chunks. A FOURCC is a 32-bit quantity represented as a sequence of one to four ASCII alphanumeric characters, padded on the right with blank characters.

frequency modulation (FM) synthesizer

A synthesizer that creates sounds by combining the output of digital oscillators using a frequency modulation technique.

General MIDI

A synthesizer specification created by the MIDI Manufacturers Association (MMA) defining a common configuration and set of capabilities for consumer Musical Instrument Digital Interface (MIDI) synthesizers.

HMS time format

A time format used by Media Control Interface (MCI) to express time in hours, minutes, and seconds. The HMS time format is used primarily by videodisc devices.

IMA

See Interactive Multimedia Association (IMA) and International MIDI Association (IMA).

Interactive Multimedia Association (IMA)

A professional trade association of companies, institutions, and individuals involved in producing and using interactive multimedia technology.

International MIDI Association (IMA)

The nonprofit organization that circulates information about the Musical Instrument Digital Interface (MIDI) specification.

LIST chunk

A Resource Interchange File Format (RIFF) chunk with a chunk identifier of LIST. LIST chunks contain a series of subchunks.

list type

A four-character code (FOURCC) identifying the type of data contained in a Resource Interchange File Format (RIFF) chunk with a chunk identifier of LIST. For example, a LIST chunk with a list type of INFO contains a list of information about a file, such as the creation date and author.

MCI

See Media Control Interface.

Media Control Interface (MCI)

High-level control software that provides a device-independent interface to multimedia devices and media files. MCI includes a command-message interface and a command-string interface.

MIDI

See Musical Instrument Digital Interface.

MIDI control-change message

A Musical Instrument Digital Interface (MIDI) message sent to a synthesizer to change different synthesizer control settings. An example of a control-change message is the volume controller message, which changes the volume of a specific MIDI channel.

MIDI Manufacturers Association (MMA)

A collective organization composed of Musical Instrument Digital Interface (MIDI) instrument manufacturers and MIDI software companies. The MMA works with the MIDI Standard Committee to maintain the MIDI specification.

MIDI Mapper

Windows systems software that modifies Musical Instrument Digital Interface (MIDI) output messages and redirects them to a MIDI output device using values stored in a MIDI setup map. The MIDI Mapper can change the destination channel and output device for a message, as well as modify program-change messages, volume values, and key values.

MIDI mapping

The process of translating and redirecting Musical Instrument Digital Interface (MIDI) messages according to data defined in a MIDI map setup.

MIDI program-change message

A Musical Instrument Digital Interface (MIDI) message sent to a synthesizer to change the patch on a specific MIDI channel.

MIDI sequence

Musical Instrument Digital Interface (MIDI) data that can be played by a MIDI sequencer.

MIDI sequencer

A program that creates or plays songs stored as Musical Instrument Digital Interface (MIDI) files. When a sequencer plays MIDI files, it sends MIDI data from the file to a MIDI synthesizer, which produces the sounds. Windows provides a MIDI sequencer, accessible through media control interface (MCI), that plays MIDI files. See also Media Control Interface (MCI).

MIDI setup map

A complete set of data for the Musical Instrument Digital Interface (MIDI) Mapper to use when redirecting MIDI messages. Only one setup map can be in effect at a given time, but the user can have several setup maps available and can choose between them by using the MIDI Mapper Control Panel option.

MMA

See MIDI Manufacturers Association.

MSF time format

A time format used by Media Control Interface (MCI) to express time in minutes, seconds, and frames. The number of frames in a second depends on the type of device being used; compact disc audio devices use 75 frames per second. The MSF time format is used primarily by compact disc audio devices.

Musical Instrument Digital Interface (MIDI)

A standard protocol for communication between musical instruments and computers.

parts per quarter note (PPQN)

A time format used for Musical Instrument Digital Interface (MIDI) sequences. PPQN is the most common time format used with standard MIDI files.

patch

A particular setup of a Musical Instrument Digital Interface (MIDI) synthesizer that results in a particular sound, usually a sound simulating a specific musical instrument. Patches are also called programs. A MIDI program-change message changes the patch setting in a synthesizer. Patch also refers to the connection or connections between MIDI devices. See also Musical Instrument Digital Interface (MIDI).

patch caching

A technique that enables some internal Musical Instrument Digital Interface (MIDI) synthesizer device drivers to preload their patch data, reducing the delay between the moment the synthesizer receives a MIDI program-change message and the moment it plays a note using the new patch. Patch caching also ensures that required patches are available (the synthesizer might load only a subset of its patches). See also Musical Instrument Digital Interface (MIDI), patch.

pitch scale factor

In waveform audio, the amount by which a waveform audio driver scales the pitch. A scale factor of two results in a one-octave increase in pitch. Pitch scaling requires specialized hardware. The playback rate and sample rate are not changed.

playback rate scale factor

In waveform audio, the amount by which the waveform audio driver scales the playback rate. Playback scaling is accomplished through software; the sample rate is not changed, but the driver interpolates by skipping or synthesizing samples. For example, if the playback rate is changed by a factor of two, the driver skips every other sample.

polyphony

The maximum number of notes that a Musical Instrument Digital Interface (MIDI) output device can play simultaneously.

PPQN

See parts per quarter note.

preimaging

The process of building a movie frame in a memory buffer before it is displayed.

Red Book audio

See compact disc - digital audio (CD-DA).

Resource Interchange File Format (RIFF)

A tagged-file specification used to define standard formats for multimedia files. Tagged-file structure helps prevent compatibility problems that often occur when file-format definitions change over time. Because each piece of data in the file is identified by a standard header, an application that does not recognize a given data element can skip over the unknown information. See also tagged file format.

RIFF

See Resource Interchange File Format (RIFF).

RIFF chunk

A chunk with chunk identifier Resource Interchange File Format (RIFF) that includes an identifying code and zero or more subchunks, the contents of which depend on the form type.

RIFF file

A file whose format complies with one of the published Resource Interchange File Format (RIFF) forms. Examples of RIFF files include WAVE files for waveform audio data, RMID files for Musical Instrument Digital Interface (MIDI) sequences, and RDIB files for device-independent bitmaps.

RIFF form

A file-format specification based on the Resource Interchange File Format (RIFF) standard.

sample

A discrete piece of waveform data represented by a single numerical value. Sampling is the process of converting analog data to digital data by taking samples of the analog waveform at regular intervals.

sampling rate

The rate at which a waveform audio driver performs audio-to-digital or digital-to-audio conversion. For compact disc – digital audio (CD-DA), the sampling rate is 44.1 kHz. See also compact disc - digital audio

sequence

See MIDI sequence.

sequencer

See MIDI sequencer.

simple device

A media control interface (MCI) device that does not require a device element (data file) for playback. The MCI compact disc audio driver is an example of a simple device.

SMPTE

See Society of Motion Picture and Television Engineers.

SMPTE division type

One of four SMPTE timing formats. SMPTE time is expressed in hours, minutes, seconds, and frames. The SMPTE division type specifies the frames-per-second value corresponding to a given SMPTE time. For example, a SMPTE time of one hour, 30 minutes, 24 seconds, and 15 frames is useful only if the frames-per-second value, or SMPTE division type, is known.

SMPTE offset

A Musical Instrument Digital Interface (MIDI) event that designates the SMPTE time at which playback of a MIDI file is to start. SMPTE offsets are used only with MIDI files using SMPTE division type.

SMPTE time

A standard representation of time developed for the video and film industries. SMPTE time is used with Musical Instrument Digital Interface (MIDI) audio because many people use MIDI to score films and video. SMPTE time is an absolute time format expressed in hours, minutes, seconds, and frames. Standard SMPTE division types are 24, 25, and 30 frames per second.

Society of Motion Picture and Television Engineers (SMPTE)

An association of engineers involved in movie, television, and video production. SMPTE also refers to SMPTE time, the timing standard that this group adopted.

square-wave synthesizer

A synthesizer that produces sound by adding square waves of various frequencies. A square wave is a rectangular waveform.

system-exclusive data

In Musical Instrument Digital Interface (MIDI), messages understood only by MIDI devices from a specific manufacturer. MIDI device manufacturers can use system-exclusive data to define custom messages that can be exchanged between their MIDI devices. (The standard MIDI specification defines only a framework for system-exclusive messages.) See also Musical Instrument Digital Interface.

tagged file format

A file format in which data is tagged using standard headers that identify information type and length. See also Resource Interchange File Format (RIFF).

tempo

The speed at which a Musical Instrument Digital Interface (MIDI) file is played. Tempo is measured in beats per minute (BPM); typical MIDI tempo is 120 BPM. See also Musical Instrument Digital Interface.

threshold

For the joystick interface, the amount, in device units, that the stick coordinates must change before the application is notified of the movement. A high threshold reduces the number of joystick messages sent to an application, but it also reduces the sensitivity of the joystick.

time stamp

A tag that enables a Musical Instrument Digital Interface (MIDI) sequencer to replay recorded MIDI data at the proper moment. See also Musical Instrument Digital Interface.

TMSF time format

A time format used by Media Control Interface (MCI) to express time in tracks, minutes, seconds, and frames. The number of frames in a second depends on the type of device being used; compact disc audio devices use 75 frames per second. The TMSF time format is used primarily by compact disc audio devices. See also Media Control Interface (MCI).

track

A sequence of sound on a compact disc – digital audio (CD-DA) disc. With a Musical Instrument Digital Interface (MIDI) file, information can be separated into tracks, defined by the creator of the file. MIDI file tracks can correspond to MIDI channels, or they can correspond to parts of a song (such as melody or chorus); a CD-DA track usually corresponds to a song. See also compact disc - digital audio.

volume scalar

A component of a Musical Instrument Digital Interface (MIDI) Mapper patch map that adjusts the volume of a patch on a synthesizer. For example, if the bass patch on a synthesizer is too loud relative to the piano patch, the volume scalar can reduce the volume for the bass or increase the volume for the piano. (Applications playing waveform audio can also adjust the output volume.) See also MIDI Mapper, patch.

WAVE file

A standard file format for storing waveform audio data. WAVE files have a .WAV filename extension.

waveform audio

A technique of recreating an audio waveform from digital samples of the waveform.

 

 

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