A single chip speech codec and filter

A simplified combination speech codec (coder/ decoder) and filter structure is described. It uses adaptive delta modulation followed by digital processing to produce a filtered log-PCM representation of a speech signal. The simplification results from combining the delta modulation step-size expansion, integration and low-pass filtering into one operation. All multiplications are eliminated and replaced by one-bit shift-and-add operations. The resulting structure is amenable to a single chip implementation using conventional, all-digital technologies while satisfying established filter standards.