Glossary definition of 'Pulse Code Modulation'

(PCM) This is the most common and basic method of representing an analogue waveform in uncompressed digital form. Essentially the amplitude of the waveform is measured at uniform intervals and stored as a series of numbers. For example, audio for use on a CD is measured (sampled) 44100 times per second. At each point the amplitude is stored as a 16 bit binary number having 65536 different possible values. Both channels are represented separately using the same technique. When stored as a computer WAV file, the resulting string of numbers is simply stored with a header defining the format used. Storage on CD requires further encoding to enable the mechanics of the CD to work properly, but the digital audio when recovered from the disk essentially remains encoded as a series of 16 bit numbers at the rate of 44100 per second.