Saf Asghar

System and method for enhanced speech quality in voice storage and retrieval systems

A digital voice data storage and retrieval system using a low bit rate encoder which provides enhanced speech signal quality while also reducing memory size requirements. The system comprises a voice coder/decoder which preferably includes a digital signal processor (DSP) and also preferably includes a local memory. During encoding of the voice data, the voice coder/decoder receives voice input waveforms and generates a parametric representation of the voice data. A storage memory is coupled to the voice coder/decoder for storing the parametric data. During decoding of the voice data, the voice coder/decoder receives the parametric data from the storage memory and reproduces the voice waveforms. According to the invention, an interframe smoothing method is performed on the parametric data after encoding of all of the speech data has completed and the parametric data has been stored in the storage memory. The interframe smoothing is performed either in the background after the coding process has completed or in real time during the decoding process immediately prior to converting the parametric data back to signal waveforms. Since all of the voice input data has already been converted to parametric data and stored in memory, parametric data from a virtually unlimited number of prior and successive frames is available for use by the smoothing algorithm. Therefore, the present invention provides more accurate smoothing and provides enhanced speech signal quality over prior systems.