Single chip multi-pulse coder with pitch prediction

The author presents a 9.6 kbps multi-pulse excited LPC coder implemented using a single TMS320c25 working at full speed. To maintain high quality in the coded speech several modifications to the classical algorithms were introduced: pitch cancelling, reoptimization of the pulse amplitudes and trellis coding of the pulse positions which allows to put almost a pulse per millisecond. The coder was simulated using PRO-MATLAB by means of which the segmental S/N ratio corresponding to different variants of the algorithm and different settings of the parameters were measured. These measurements were the base for the final selection of algorithms and parameters that led to the implementation in real-time. This implementation was simplified by the use of a library of basic DSP building blocks that produced more than 90% of the assembler code almost automatically