Technical information

Codec Compression/Decompression. A system which compresses a signal in
some way for storage or transportation and then decompresses it at the point of
delivery. Examples are MPEG, Dolby Digital and DTS. These systems use a codec
to reduce the amount of data in the signal. Other forms of codec, particularly in
the days of analogue audio systems, compressed and then decompressed the
dynamic range of the signal, not to reduce the size of the signal but to reduce
noise levels. One consumer system was called 'dbx'. Digital data storage for
audio use several software systems to take complete 16 bit (or higher) files in
WAV and compress to nearly half their size. When uncompressed, the files are
again identical WAV files. One common compression program is known as FLAC.
Colouration An unwanted alteration in the character of audio. Significant
colouration of sound can make instruments and voices sound unrealistic. It may
be caused by harmonic distortion, vibrations of component parts (for example, the
panels of an inadequately braced loudspeaker enclosure) or, most commonly,
through an uneven frequency response.
Compact cassette A neatly packaged magnetic tape recording and playback
system for audio introduced in the 1960s. Uses a narrow plastic tape with four
tracks running at a speed of 28.6mm/s (1 and 1/8 inches per second). While
initially very low in fidelity, in the early 1970s tremendous advances were made in
tape formulations, first with Chromium Dioxide magnetic materials and then later
with 'Metal' tapes, which extended the high frequency response and improved their
saturation characteristics. The addition of Dolby B noise reduction (and later
Dolby C) reduced the inherent problem of high noise levels due to the low tape
speed.
Compander Compressor/Expander. A noise-reduction system that works by
compressing the dynamic range of the audio before recording, and expanding it
again by an equivalent amount during playback. An example of this was the dbx
system.
Compliance The degree of 'springiness' in a mechanical system. For example, the
cone of a loudspeaker driver with a soft suspension which can move to and fro
relatively easily is more compliant than one with a stiff suspension. The stylus of
turntable cartridge with a high compliance tends to follow the excursions of the
groove more easily than a that of a cartridge with low compliance.
Component video Three components of a video signal that, together, constitute
the full signal. The three components are luminance (Y), red colour difference
(CR) and blue colour difference (CB). These can be wrapped into each other to
various degrees to form S-Video signals or composite video signals. On DVD the
video signal is carried in component video form. The best way to deliver the DVD's