DEVELOPING A LOW BIT RATE SPEECH CODER BASED ON THE HALF RATE GSM STANDARD-'C30

This application report describes the development of a low bit rate speech coder based on the GSM HR (Half Rate) speech coding standard using the Texas Instruments (TITM) TMS320C30 digital signal processor (DSP). For storage applications, the delay introduced by the coder is not critical and the bit rate does not need to be constant. It is therefore possible to develop high performance coders with variable rates. Applications of such a system are:

-Telephone voice recorders

-Voice email

-Black boxes for airplanes

The paper discusses the VSELP (Vector Sum Excited Coder) coder and the algorithm used to reduce the computation load. It describes the C program structure and the TI TMS320C30 optimizing C compiler.

This work is part of a project of static voice recording supported by the Texas Instruments Elite program. The aim is to develop several speech coding methods with decreasing bit rates for voice storage.

This document was part of the first European DSP Education and Research Conference that took place September 26 and 27, 1996 in Paris. For information on how TI encourages students from around the world to find innovative ways to use DSPs, see TI's World Wide Web site at www.ti.com.

*DISCLAIMER: This document was part of the DSP Solution Challenge 1995 European Team Papers. It may have been written by someone whose native language is not English. TI assumes no liability for the quality of writing and/or the accuracy of the information contained herein.

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