Efficient Implementation of ITU-T G.723.1 Speech Coder for Multichannel Voice Transmission and Storage

摘要

Dual-rate G.723.1 speech coder has been widely applied to real-time video and teleconferencing applications where reduced bandwidth and good voice quality is required. This paper presents an efficient implementation of G.723.1 speech coder. To simplify the excitation quantization procedure which is the most computationally demanding, we propose fast algorithms for adaptive codebook and fixed codebook search. In the fast adaptive codebook search, pitch delay and pitch gains are computed sequentially. In the fast fixed code-book search, the codebook structure is redesigned based on the interleaved single-pulse permutation (ISPP) design at high rate mode and the depth-first tree search is applied instead of nested-loop search at low rate mode. A real-time implementation is achieved using a 16-bit fixed-point TMS320C62x DSP. The implemented G.723.1 speech coder requires 8.70 and 10.29 MHz clock cycles at low and high rate, respectively, 57.8 kByte of program memory and 55 kByte of data memory. Thus, more than 16 channels of G.723.1 coder can be operated in real-time using a single TMS320C62x DSP.