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US 4,736,428 AGranted
Multi-pulse excited linear predictive speech coder
AssigneeU.S. Philips Corporation
InventorsEdmond F. A. Deprettere, Peter Kroon
Life of this patent
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Abstract
A multipulse excitation signal, as a better approximation than a single-pulse excitation signal, searches for a kth pulse which minimizes either a difference between a synthesized and a reference signal, or a distance between a multipulse excitation signal and a residual signal. The search uses an averaging function M.sub.k (n) of a weighted error signal.
Claims8
A multi-pulse excited linear predictive speech coder comprising:
- a. a multi-pulse excitation signal generator for generating a multi-pulse excitation signal and having a control input;
- b. a linear-predictive speech synthesizer, for synthesizing a signal from the multi-pulse excitation signal to produce synthetic speech samples;
- c. means for receiving a reference speech signal;
- d. a difference generator for comparing the reference speech samples with the synthetic speech samples and producing a difference signal;
- e. means for perceptually weighting the difference signal to produce a weighted error signal;
- and
- f. means for controlling the multi-phase excitation signal generator in response to the weighted error signal to minimize the weighted error signal;
- wherein the improvement comprises:
- g. means for determining a position of a k.sup.th pulse in a given interval of the multi-pulse excitation signal, where k is an integer, the k.sup.th pulse being one for which the difference signal is minimized, including:
- i. means for producing an average magnitude auxiliary function (M.sub.k (n)), which is a measure of the energy of the weighted error signal determined from the multi-pulse excitation signal after (k-1) pulses;
- ii. means for identifying a value n'.sub.k of n for which the auxiliary function (M.sub.k (n)) is maximized;
- iii. means for determining a reduced interval, shorter than the given interval, in a region surrounding n'.sub.k ;
- and
- iv. means for searching for the k.sup.th pulse weighting the reduced interval, whereby computational complexity is reduced.
11 more elements
A method of multi-pulse excited linear predictive speech coding comprising the steps of:
- a. generating a multi-pulse excitation signal;
- b. synthesizing synthetic speech samples from the multi-pulse excitation signal to produce synthetic speech samples in a linear-predictive manner;
- c. receiving a reference speech signal;
- d. generating a difference signal representing a difference between the reference speech samples and the synthetic speech samples;
- e. perceptually weighting the difference signal to produce a weighted error signal;
- and
- f. controlling the multi-pulse excitation signal generator in response to the weighted error signal to minimize the weighted error signal;
- wherein the improvement comprises:
- g. determining a position of a k.sup.th pulse in a given interval of the multi-pulse excitation signal, where k is an integer, the k.sup.th pulse being one for which the difference signal is minimized, including:
- i. producing an average magnitude auxiliary function (M.sub.k (n)), which is a measure of the energy of the weighted error signal determined from the multi-pulse excitation signal after (k-1) pulses;
- ii. identifying a value n'.sub.k of n for which the auxiliary function (M.sub.k (n)) is maximized;
- iii. determining a reduced interval, shorter than the given interval, in a region surrounding n'.sub.k ;
- and
- iv. seraching for the k.sup.th pulse weighting the reduced interval, whereby computational complexity is reduced.
11 more elements
A multi-pulse excited linear predictive speech coder comprising:
- a. a multi-pulse excitation signal generator producing a multi-pulse excitation signal and having a control input;
- b. means for receiving a reference speech signal;
- c. means for analyzing the reference speech signal to produce a residual signal, said analyzing means performing an analyzing operation which is the inverse of a linear-predictive synthesizing operation which produces synthetic speech samples from the multi-pulse excitation signal, whereby a speech synthesizer performing the synthesizing operation may be omitted from the coder;
- d. means for generating a distance function signal measuring a distance between the residual signal and the multi-pulse excitation signal;
- e. means for perceptually weighting the distance function signal to create a weighted error signal;
- f. means for controlling the multi-pulse excitation generator in response to the weighted error signal to reduce the weighted error signal;
- and
- g. means for determining a position of a k.sup.th pulse in a given interval of the multi-pulse excitation signal, where k is an integer, the k.sup.th pulse being one for which the distance function signal is minimized, including:
- i. means for producing an average magnitude auxiliary function (M.sub.k (n)), which is a measure of the energy of the weighted error signal determined from the multi-pulse excitation signal after (k-1) pulses;
- ii. means for identifying a value n'.sub.k of n for which the auxiliary function (M.sub.k (n)) is maximized;
- iii. means for determining a reduced interval, shorter than the given interval, in a region surrounding n'.sub.k ;
- and
- iv. means for searching for the k.sup.th pulse weighting the reduced interval, whereby computational complexity is reduced.
10 more elements
The method of multi-pulse excited linear predictive speech coding comprising the steps of:
- a. controllably generating a multi-pulse excitation signal a multi-pulse excitation signal;
- b. receiving a reference speech signal;
- c. analyzing the reference speech signal to produce a residual signal, said analyzing step including an analyzing operation which is the inverse of a linear-predictive synthesizing operation which produces synthetic speech samples from the multi-pulse excitation signal, whereby no speech synthesizing step is performed;
- d. generating a distance function signal measuring a distance between the residual signal and the multi-pulse excitation signal;
- e. perceptually weighting the distance function signal to create a weighted error signal;
- f. controlling the multi-pulse excitation generating step in response to the weighted error signal to reduce the weighted error signal;
- and
- g. determining a position of the k.sup.th pulse in a given interval of the multi-pulse excitation signal, where k is an integer, the k.sup.th pulse being one for which the distance function signal is minimized, including the steps of:
- i. producing an average magnitude auxiliary function (M.sub.k (n)), which is a measure of the energy of the weighted error signal determined from the multi-pulse excitation signal after (k-1) pulses;
- ii. identifying a value n'.sub.k, of n for which the auxiliary function (M.sub.k (n)) is maximized;
- iii. determining a reduced interval, shorter than the given interval, in a region surrounding n'.sub.k ;
- and
- iv. searching for the k.sup.th pulse within the reduced interval, whereby computational complexity is reduced.
10 more elements
Dependencies are inferred from the claim text.