Design and implementation of a parametric speech coder

Currently, it has been found out that speech coders based on linear predictive coding are good and accurate in modeling speech utterances. It does not only modeled speech utterance in an accurate manner but it also has the following properties: i) it provides a good estimate of the vocal tract spectral envelope; ii) it is analytically tractable; iii) it can be implemented in either software or hardware; iv) it uses lesser data storage than many other approaches of speech coders. In this paper, a hybrid speech coder based on Code Excited Linear Predictive Coding (CELPC) and Voice Excited Linear Predictive Coding (VELPC) is presented. CELPC is currently one of the main techniques for producing high quality speech at around 4. 8 kbps. However, the computation requirement for the original CELPC was too demanding and not suitable for practical use. Therefore, a hybrid approach to produce speech signals with high quality and with a bit rate of 3. 478 kbps has been proposed. This method splits the speech signal into two portions, the base-band signal and the high-band signal in the frequency domain. The base-band and the high-band signal are then coded using the CELPC and VELPC techniques, respectively. © 1998 IEEE.