Implementation of various LPC algorithms using commercial digital signal processors

An LPC vocoder which is compatible to the government standard algorithm LPC-10 can be implemented using three µPD 7720 Signal Peripheral Interfaces (SPI) from NEC, a microprocessor (CPU), and some other commercial integrated circuits. The main tasks, LPC analysis, pitch analysis, and synthesis, can be performed with one SPI each. Due to their large RAM storage requirements, the block-form LPC-10 algorithm is not well suited for such an implementation. Its components must be modified or even totally replaced by other algorithms which can be performed on a sample-by-sample basis and therefore require less RAM storage. In this paper some results of investigations on implementing various LPC algorithms are presented. The components of the LPC-10 algorithm are compatible with the components of the algorithms suggested in this paper, i. e. the analysis and synthesis components may be mixed with no audible degradation of speech.