Method and apparatus for decoding speech signal
AssigneeNEC Corporation
InventorAtsushi Murashima
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Abstract
A method of decoding a speech signal based on a CELP (Code Excited Linear Prediction) with improvement in degradation of decoded sound quality in a noise period. The method includes the steps of: calculating a norm of an excitation vector for each fixed period in a noise period; smoothing the calculated norm using a norm obtained in a previous period; changing the amplitude of the excitation vector in the period using the calculated norm and the smoothed norm; and driving a synthesizing filter by the excitation vector with the changed amplitude.
Claims20
A method of decoding a speech signal by decoding information on an excitation signal and information on a linear prediction coefficient from a received signal, producing said excitation signal and said linear prediction coefficient from said decoded information, and driving a filter configured with said linear prediction coefficient by said excitation signal, said method comprising the steps of:
- calculating a norm of said excitation signal for each fixed period;
- smoothing said calculated norm using a norm obtained in a previous period;
- changing amplitude of said excitation signal in said period using said calculated norm and said smoothed norm;
- and
- driving said filter by said excitation signal with the changed amplitude wherein the amplitude of said excitation signal is changed by dividing said excitation signal in said period by said norm, and multiplying said excitation signal by said smoothed norm in said period.
An apparatus for decoding a speech signal by decoding information on an excitation signal and information on a linear prediction coefficient from a received signal, producing said excitation signal and said linear prediction coefficient from said decoded information, and driving a filter configured with said linear prediction coefficient by said excitation signal, said apparatus comprising:
- an excitation signal normalizing circuit for calculating a norm of said excitation signal for each fixed period and dividing said excitation signal by said norm;
- a smoothing circuit for smoothing said norm using a norm obtained in a previous period;
- and
- an excitation signal restoring circuit for multiplying said excitation signal by said smoothed norm to change amplitude of said excitation signal in said period.
A method of decoding a speech signal by decoding information on an excitation signal and information on a linear prediction coefficient from a received signal, producing said excitation signal and said linear prediction coefficient from said decoded information, and driving a filter configured with said linear prediction coefficient by said excitation signal, said method comprising:
- calculating a norm of said excitation signal for each fixed period;
- smoothing said calculated norm using a norm obtained in a previous period;
- changing amplitude of said excitation signal in said period using a ratio of said calculated norm and said smoothed norm;
- and
- driving said filter by said excitation signal with the changed amplitude wherein temporal fluctuation of said excitation signal is reduced.
An apparatus for decoding a speech signal by decoding information on an excitation signal and information on a linear prediction coefficient from a received signal, producing said excitation signal and said linear prediction coefficient from said decoded information, and driving a filter configured with said linear prediction coefficient by said excitation signal, said apparatus comprising:
- an excitation signal normalizing circuit for calculating a norm of said excitation signal for each fixed period;
- a smoothing circuit for smoothing said norm using a norm obtained in a previous period;
- and
- an excitation signal restoring circuit for changing amplitude of said excitation signal in said period,
- wherein said amplitude is changed based on a ratio of said calculated norm and said smoothed norm.
Dependencies are inferred from the claim text.