adaptive differential pulse code modulation [ADPCM]


(n.) A standard method endorsed by the Interactive Multimedia Association (IMA) for storing digital audio on a multiple-session CD-ROM XA or a CD-i. The procedure reduces the amount of data needed by examining previously encoded data and adaptively predicting future encoding, eliminating some redundancy, and storing the differences between successive digital samples rather than full values. It is an extension of the pulse code modulation (PCM) audio encoding format. Another version of this audio encoding process standardized by the CCITT for telecommunications applications can transmit a voice over a 32-kilobit-per-second (Kbps) digital channel. Each sample is defined by three or four bits that represent the difference between adjacent samples.