Computationally efficient implementation of AMR speech coder

The adaptive multi-rate speech codec consists of eight source codecs with bit rates from 4.75 to 12.2 kbit/s. This paper presents an AMR implementation especially focused on reducing the computational complexity. In order to reduce the computational load, we propose the fast codebook search method that is simply modified version of the depth first tree search method used in algebraic codebook search in the AMR codec. For the AMR implementation we designed the 16 bit fixed-point DSP based on the TeakLite DSP core, which was tailored for the AMR implementation. The implemented AMR codec requires only 19.6 MIPS of computation for the highest complexity mode of the AMR by using the fast search method and exploiting the DSP architecture and managing the memory structure efficiently. It is verified with all the test vectors provided by 3GPP, and stable operation on the real-time testing board was also confirmed.