Method of quantizing line spectral frequencies when calculating filter parameters in a speech coder

Claim 1

A method of generating quantized line spectral frequency signals from incoming speech samples when calculating parameters for an analysis filter included in a speech coder in linear predicted coding of the incoming speech samples with the intention of synthesizing said samples in a speech decoder subsequent to transmitting the line spectral frequency signals over a transmission channel having limited transmission capacity, wherein the line spectral frequency signals are formed by constructing, based on the incoming speech samples, two mutually symmetrical polynomials for the analysis filter with alternating roots on a unit circle, and quantizing the roots obtained from said two polynomials and corresponding to the line spectral frequencies, comprising the steps of: storing, in a memory store, a number of quantizing levels which correspond to pre-calculated line spectral frequencies; seeking or scanning alternately on each of said polynomials, using a given number of test frequency values derived from said quantizing levels, to establish a polarity of each of the polynomials and determine a polarity change between two mutually sequential test frequency values for one and the same polynomial, the quantizing level which corresponds to the value between said two mutually sequential test frequency values then being chosen as a quantized line spectral frequency signal, wherein the chosen quantizing level lies midway between two consecutive test frequency values.

Claim 2

A method of generating quantized line spectral frequency signals from incoming speech samples when calculating parameters for an analysis filter included in a speech coder in linear predicted coding of the incoming speech samples with the intention of synthesizing said samples in a speech decoder subsequent to transmitting the line spectral frequency signals over a transmission channel having limited transmission capacity, wherein the line spectral frequency signals are formed by constructing, based on the incoming speech samples, two mutually symmetrical polynomials for the analysis filter with alternating roots on a unit circle, and quantizing the roots obtained from said two polynomials and corresponding to the line spectral frequencies, comprising the steps of: storing, in a memory store, a number of quantizing levels which correspond to pre-calculated line spectral frequencies; seeking or scanning alternately on each of said polynomials, using a given number of test frequency values derived from said quantizing levels, to establish a polarity of each of the polynomials and determine a polarity change between two mutually sequential test frequency values for one and the same polynomial, the quantizing level which corresponds to the value between said two mutually sequential test frequency values then being chosen as a quantized line spectral frequency signal, wherein the chosen quantizing level lies midway between two consecutive test frequency values.

Claim 6

A method generating quantized line spectral frequency signals from incoming speech samples when calculating parameters for an analysis filter included in a speech coder in the linear predictive coding of the incoming speech samples in order to synthesize said samples in a speech decoder subsequent to transmitting the line spectral frequency signals across a transmission channel with limited transmission capacity, wherein the line spectral frequency signals are formed by forming, based on the incoming speech samples, two mutually symmetrical polynomials with alternating roots on a unit circle for the analysis filter and quantizing the roots obtained from said two polynomials and corresponding to the line spectral frequencies, comprising: a) storing, in a memory store, a number of quantizing levels which correspond to precalculated fixed line spectral frequencies, b) combining a given number of test frequencies derived from said quantizing levels into groups of test frequencies, each group corresponding to a possible root in each of said polynomials, c) scanning alternatingly on each of said polynomials by means of said given number of test frequencies, to establish the polarity of each of said polynomials, d) for each of said polynomials, evaluate a given root by using the test frequency values belonging to a given group to determine two consecutive frequency values for which a change in polarity for one and the same polynomial has occurred, and e) determining the quantizing level which corresponds to the value between said two consecutive test frequency values, thus determining the positions of the roots of each polynomial and the specific quantized lines spectral frequency signals.

Claim 7

A method generating quantized line spectral frequency signals from incoming speech samples when calculating parameters for an analysis filter included in a speech coder in the linear predictive coding of the incoming speech samples in order to synthesize said samples in a speech decoder subsequent to transmitting the line spectral frequency signals across a transmission channel with limited transmission capacity, wherein the line spectral frequency signals are formed by forming, based on the incoming speech samples, two mutually symmetrical polynomials with alternating roots on a unit circle for the analysis filter and quantizing the roots obtained from said two polynomials and corresponding to the line spectral frequencies, comprising: a) storing, in a memory store, a number of quantizing levels which correspond to precalculated fixed line spectral frequencies, b) combining a given number of test frequencies derived from said quantizing levels into groups of test frequencies, each group corresponding to a possible root in each of said polynomials, c) scanning alternatingly on each of said polynomials by means of said given number of test frequencies, to establish the polarity of each of said polynomials, d) for each of said polynomials, evaluate a given root by using the test frequency values belonging to a given group to determine two consecutive frequency values for which a change in polarity for one and the same polynomial has occurred, and e) determining the quantizing level which corresponds to the value between said two consecutive test frequency values, thus determining the positions of the roots of each polynomial and the specific quantized lines spectral frequency signals.