Patent ID: 6871176

Claim:
A speech encoder, comprising: a content extraction module including, a band pass filter that receives a speech input signal and generates a band limited speech signal, a first speech buffer connected to the band pass filter that stores the band limited speech signal, an LP analysis block connected to the first speech buffer that reads the stored speech signal and generates a plurality of LP coefficients therefrom, an LPC to LSF block connected to the LP analysis block for converting the LP coefficients to a line spectral frequency (LSF) vector, an LP analysis filter connected to the LPC to LSF block that extracts an LP residual signal from the LSF vector; and an LSF quantizer connected to the LPC to LSF block that receives the LSF vector and determines an LSF index therefor; a pitch detector connected to the LP analysis block of the content extraction module, the pitch detector classifying the band filtered speech signal as one of a voiced signal and an unvoiced signal; and a naturalness enhancement module connected to the content extraction module and the pitch detector, the naturalness enhancement module including, means for extracting parameters from the LP residual signal, wherein for an unvoiced signal the extracted parameters include pitch and gain and for a voiced signal the extracted parameters include pitch, gain and excitation level; and a quantizer for quantizing the extracted parameters and generating quantized parameters.