Real-time implementation and optimization of ITU´s G.728 on TMS320C64X DSP

The objective of this paper is to illustrate the details of optimization and real-time implementation of ITU´s G.728 on C64x DSPs. First using pseudo codes provided by CCITTs published documents, we implemented the algorithm in C language. This implementation was performed for G and H (12.8 and 9.6 kbit/s) annexes. Next we optimized the written codes for implementation on DSP. At first stage, using different techniques based on DSPs´ hardware characteristics, we rewrote and changed the most time-consuming parts of our codes in order to reduce their execution time. At second stage, we balanced the computational load of G.728 coder algorithm by splitting the Durbin´s recursion for synthesis filter between different input speech vectors. In each stage, we verified the correctness of our implementation by testing our codes against testing vectors provided by ITU. Applying the above mentioned methods enabled us to optimize the C codes into 22.7 MIPS in worst case. At the end we also implemented the optimized codes in real-time on a DSK6416