Matrix quantization based speech coder at 1200 bps

This paper presents a new 1200 bps speech coder designed with a tree searched multi stage matrix quantization scheme. With the new matrix quantization method, spectral distortion about 1 dB is achieved using rates as low as 18 bits/frame. In the proposed coder, LSF parameters of two consecutive frames are grouped into a superframe and jointly quantized. For other speech parameters, quantization is made for each frame. New techniques for improving performance include joint quantization of pitch and voiced/unvoiced/mixed decisions, gain interpolation and residual LSF quantization. For the new matrix quantization based speech coder (MQBC), the listening tests have proven that an efficient and high quality coding has been achieved at bit rate 1200 bps. Test results are compared with the 2400 bps LPC10e coder and the new 2400 bps MELP coder chosen as the new 2400 bps Federal Standard