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Glossary of terms

August 30, 1999
Web posted at: 3:05 p.m. EDT (1905 GMT)

by the Computerworld staff
   Sound adds a useful dimension to corporate intranets

(IDG) -- If your organization intends to deploy multimedia files across the network, you'll likely encounter many of the following buzzwords.

Band: A range of frequencies that fall within two definite limits.

Bit rate: The average number of bits that one second of multimedia data will consume. Usually measured in kilobits per second (K bit/sec.), it can be used to describe how much compression has been applied to a multimedia data file and can be a measure of sound quality as well.

CD Ripper: A program that pulls audio tracks from a CD and converts them to digital WAV format.

Channel: A stream of sound intended to be reproduced through a single output device such as a loudspeaker. Monaural sound, for example, has a single channel that can't be split into additional channels. Standard stereo sound, on the other hand, has two channels: treble and bass.

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Codec: Stands for compression/decompression, or coder/decoder. A codec manages the process of turning digital multimedia data -- such as sound or video -- into a form that can be sent across a network and received on the other side with as little loss in quality as possible and minimal impact on resources such as bandwidth.

Decoding: The process of converting an encoded (compressed) bitstream back to its original format.

Encoding: The very complex process of converting uncompressed digital data into a highly compressed and coded form known as a bitstream. In order to be played, the bitstream must be uncompressed, or decoded, and returned to its original format.

Frequency: A single repetition of the soundwave's shape is known as a waveform or cycle. The frequency of that sound is the number of cycles the wave goes through in one second, measured in hertz (Hz). The more waveforms that occur in one second, the higher the frequency. The higher the frequency, the higher the tone (pitch) of the sound.

Lossy compression: A technique of reducing file size by discarding data. Once discarded, data can't be retrieved. Lossy compression techniques produce small files that don't need to be decompressed in a separate step before use, but the trade-off is some loss of quality.

Lossless compression: A technique of reducing file size by eliminating redundancies. Lossless compression formats, such as Zip, must be expanded before use, but they reproduce the original file exactly, without data loss.

MP3: First, it doesn't stand for MPEG-3. It's short for MPEG-Audio Layer 3 and is the third in a series of audio compression scheme standards maintained by the Moving Picture Experts Group. MP3 is generally thought to produce better final sound quality than its predecessors, at a much higher compression rate.

Sampling: Sound is, by definition, an analog phenomenon because it occurs in continuous waves. To be used in a computer, it must be converted to a digital format. In order to do this, instruments measure, or sample, the frequency of the sound wave at specified intervals. That's known as the sampling rate. The higher the sampling rate, the more samples per second are taken by these instruments, and the truer the digital version will be to the original analog sound wave. However, the higher the sampling rate, the larger the resulting digital sound file will be -- because the number of samples being saved increases as well.

WAV: Short for "waveform audio" and pronounced "wave," WAV is one of the most common uncompressed digital audio formats.

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