Analysis-by-synthesis speech coding method with open-loop and closed-loop search of a long-term prediction delay
First Claim
1. Analysis-by-synthesis speech coding method for a speech signal digitised into successive frames each divided into a number nst of sub-frames, each sub-frame having a number lst of samples, comprising the steps of:
- linear prediction analysis of the speech signal in order to determine parameters of a short-term synthesis filter;
open-loop analysis of the speech signal in order to detect voiced frames of the signal and in order, for each voiced frame, to determine a degree of voicing of the signal and an interval for searching for a long-term prediction delay;
closed-loop predictive analysis of the speech signal in order, for at least one of the sub-frames of the voiced frames, to select a long-term prediction delay contained in the search interval and constituting a parameter of a long-term synthesis filter; and
determination of a stochastic excitation for each sub-frame, so as to minimise a perceptually weighted difference between the speech signal and the stochastic excitation filtered by the long-term and short-term synthesis filters,wherein, in the open-loop analysis step, the search interval relating to each voiced frame is so determined as to contain a number of delays which is dependent on the degree of voicing of said frame.
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Abstract
A method comprising the steps of performing a linear prediction analysis of a speech signal digitized in a series of frames divided into sub-frames, in order to determine the parameters of a short-term synthesis filter; carrying out an open loop analysis to detect voiced signal frames and determine, for each voice frame, a degree of signal voicing and a long-term prediction delay search interval containing a number of delays depending on the degree of voicing; carrying out a closed-loop predictive analysis of the speech signal to select, for at least some sub-frames of the voiced frames, a long-term prediction delay contained in the search interval and constituting a long-term synthesis filter parameter; and determining a stochastic excitation for each sub-frame, to minimize a perceptually weighted deviation between the speech signal and the stochastic excitation filtered by the long-term and short-term synthesis filters.
71 Citations
18 Claims
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1. Analysis-by-synthesis speech coding method for a speech signal digitised into successive frames each divided into a number nst of sub-frames, each sub-frame having a number lst of samples, comprising the steps of:
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linear prediction analysis of the speech signal in order to determine parameters of a short-term synthesis filter; open-loop analysis of the speech signal in order to detect voiced frames of the signal and in order, for each voiced frame, to determine a degree of voicing of the signal and an interval for searching for a long-term prediction delay; closed-loop predictive analysis of the speech signal in order, for at least one of the sub-frames of the voiced frames, to select a long-term prediction delay contained in the search interval and constituting a parameter of a long-term synthesis filter; and determination of a stochastic excitation for each sub-frame, so as to minimise a perceptually weighted difference between the speech signal and the stochastic excitation filtered by the long-term and short-term synthesis filters, wherein, in the open-loop analysis step, the search interval relating to each voiced frame is so determined as to contain a number of delays which is dependent on the degree of voicing of said frame. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
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Specification