A 16kbps APC codec using digital signal processors

A compact 16kbps speech codec for digital radio communications was developed using three NEC signal processor LSI chips. Adaptive Predictive Coding (APC) with variable length coding for residual signal was employed in the codec. Additional functions for communications such as error correction and frame synchronization were also included. Actual board size for the half duplex codec is 9 × 15 cm. A 20.5 dB segmental SN ratio was obtained.