Unary coding scheme for digital audio signals

Abstract

A coding scheme for digital audio signals. A method of coding a unary digital audio signal is provided for compressing a set of unary digital audio signal data comprising a succession of absolute amplitude values associated with respective sample periods of the digital audio signal, the absolute amplitude values being integers of positive or zero value, representing the number of speaker elements of a unary digital loudspeaker that are to be active in a sample period. The data is compressed by calculating the numerical difference between adjacent ones of the absolute amplitude values, thereby to convert the succession of absolute amplitude values into a corresponding succession of difference amplitude values. Each difference amplitude values is expressed as a sign bit and a plurality of data bits, representing the change in the number of speaker elements of a unary digital loudspeaker that are to be active in a given sample period relative to the immediately preceding sample period. A corresponding method of decoding the compressed signal is also provided, together with associated encoding and decoding apparatuses.