A low-bit-rate speech coding system using a low cost stack architecture microprocessor

A real-time Adaptive Differential Pulse Code Modulation (ADPCM) system is described which employs an inexpensive, currently about $25, stack-architecture microprocessor. The coder operates at 3 bits/sample and a 10 KHz rate and performs all processing between the taking of input speech samples. The ADPCM tables are stored in the stack for rapid manipulation of table column and row pointers allowing implementation of real-time operation.