Method and apparatus for speech compression using multi-mode code excited linear predictive coding
First Claim
1. A method of communicating digitized voice signals in a computer system, said computer system including an analyzer coupled to a synthesizer, said method comprising the steps of:
- dividing said digitized voice signals into a plurality of frames, each frame of said plurality of frames including a plurality of subframes;
for at least one frame of said plurality of frames performing the steps of;
calculating a set of linear prediction coefficients (LPCs) corresponding to said frame; and
for at least one subframe in said frame performing the steps of;
determining a previous search mode for a previous subframe;
selecting from a plurality of modes a currently selected set of modes based on said previous search mode;
selecting a current search mode from said currently selected set of modes;
encoding a set of selected parameters for said current search mode;
transmitting said selected parameters from said analyzer to said synthesizer;
decoding said selected parameters according to said current search mode; and
generating a synthesized voice signal from said selected parameters, said synthesized voice signal corresponding to said digitized voice signals.
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Abstract
An apparatus and method of coding speech. The apparatus includes a first circuit being coupled to receive a first signal, the first signal corresponds to the speech signal. The first circuit is for generating a first set of parameters corresponding to the first frame. The apparatus includes a second circuit, being coupled to receive a second signal and the first set of parameters, the second signal corresponding to the speech signal, and the second circuit is for generating a third signal. The apparatus further includes a pulse train analyzer, being coupled to the second circuit, for generating a third match value, a third set of parameters, and a third excitation value. The apparatus further including a fourth circuit, being coupled to the second circuit, for generating a fourth match value, a fourth set of parameters, and a fourth excitation value. The apparatus further including a fifth circuit, being coupled to the third circuit and the fourth circuit, for selecting a mode corresponding to a match value. The apparatus further including a sixth circuit, being coupled to the fifth circuit, for selecting a selected set of parameters and a selected excitation corresponding to the mode. The apparatus further including a seventh circuit, being coupled to the first circuit and the sixth circuit, for generating an encoded signal responsive to the selected set of parameters and the mode.
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Citations
25 Claims
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1. A method of communicating digitized voice signals in a computer system, said computer system including an analyzer coupled to a synthesizer, said method comprising the steps of:
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dividing said digitized voice signals into a plurality of frames, each frame of said plurality of frames including a plurality of subframes; for at least one frame of said plurality of frames performing the steps of; calculating a set of linear prediction coefficients (LPCs) corresponding to said frame; and for at least one subframe in said frame performing the steps of; determining a previous search mode for a previous subframe; selecting from a plurality of modes a currently selected set of modes based on said previous search mode; selecting a current search mode from said currently selected set of modes; encoding a set of selected parameters for said current search mode; transmitting said selected parameters from said analyzer to said synthesizer; decoding said selected parameters according to said current search mode; and generating a synthesized voice signal from said selected parameters, said synthesized voice signal corresponding to said digitized voice signals. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A method of encoding digitized voice signals in a computer system, wherein said digitized voice signals are divided into a plurality of frames, each frame of said plurality of frames including a plurality of subframes, said method comprising the steps of:
for at least one subframe in said frame performing the steps of; determining a previous search mode for a previous subframe; selecting from a plurality of modes a currently selected set of modes based on said previous search mode; selecting a current search mode from said currently selected set of modes; and encoding a set of selected parameters for said current search mode. - View Dependent Claims (9, 10, 11, 12, 13, 14)
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15. A method of encoding a current subframe representing a portion of a digitized voice signal, said method comprising the steps of:
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obtaining information regarding a previously selected excitation search mode used for a previous subframe; selecting from a plurality of excitation search modes a set of more than one admissible excitation search modes based upon said information, each excitation search mode in said plurality of excitation search modes corresponding to one of a plurality of sets of excitation parameters; selecting one of said set of more than one admissible excitation search modes as a current excitation search mode; selecting one of said plurality of sets of excitation parameters as a currently selected set of excitation parameters based upon said current excitation search mode, each set of excitation parameters in said plurality of sets of excitation parameters produced by a corresponding circuit; and encoding said current subframe using said current excitation search mode and said currently selected set of excitation parameters. - View Dependent Claims (16, 17)
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18. An apparatus for transforming a voice signal into an encoded signal comprising:
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a plurality of circuits, each circuit in said plurality of circuits for performing a different excitation search technique to generate an excitation and a set of parameters for use in encoding said voice signal; a comparator and controller circuit for selecting a current excitation search technique from said different excitation search techniques, said comparator and controller circuit selects said current excitation search technique by selecting a subset of said different excitation search techniques based on a previous excitation search technique used for encoding a previously processed subframe of said voice signal; a selector of parameters coupled to said comparator and controller circuit for selecting as a currently selected set of parameters the set of parameters generated by the one of said plurality of circuits that performs said current excitation search technique; a selector of excitations coupled to said comparator and controller circuit for selecting as a currently selected excitation the excitation generated by the one of said plurality of circuits that performs said current excitation search mode; and an encoder coupled to said selection circuit for encoding said voice signal using said currently selected excitation and set of parameters. - View Dependent Claims (19, 20)
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21. A method of encoding digitized voice signals, wherein said digitized voice signals are divided into a plurality of frames, said method comprising steps of:
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dividing each of a plurality of frames into subframes; and employing a single search mode for a subframe by performing the steps of; determining a previous search mode for a previous subframe, selecting from a plurality of modes a currently selected set of modes based on said previous search mode, selecting a current search mode from said currently selected set of modes, and encoding no more than one set of parameters for the subframe, the one set of parameters corresponding to said current search mode. - View Dependent Claims (22, 23)
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24. A method of encoding digitized voice signals in a computer system, wherein said digitized voice signals are divided into a plurality of frames, each frame of said plurality of frames including a plurality of subframes, said method comprising the steps of:
for at least one subframe in said frame performing the steps of; determining a previous search mode for a previous subframe; determining a currently selected set of search modes based on said previous search mode, the currently selected set of search modes including at least two search modes; dynamically selecting a current search mode from said currently selected set of search modes; and encoding a set of selected parameters for said current search mode. - View Dependent Claims (25)
Specification