Method and apparatus for transcoding between different speech encoding/decoding systems
First Claim
1. A code converting method for converting a first code sequence conforming to a first system to a second code sequence conforming to a second system, comprising the steps of:
- acquiring a first linear prediction coefficient and first information on an excitation signal from said first code sequence and actuating a filter having said first linear prediction coefficient with the excitation signal obtained from said first information to generate a first speech signal;
deriving an optimum gain based on a second speech signal generated by second information obtained from said second code sequence, and based on said first speech signal;
correcting said optimum gain to generate corrected optimum gain; and
finding gain information in said second code sequence based on said corrected optimum gain, said optimum gain and on a gain read out from a gain codebook for said second system.
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Accused Products
Abstract
A code converting apparatus for converting a first code sequence conforming to a first system to a second code sequence conforming to a second system, in which a speech decoding circuit acquires a first linear prediction coefficient and the information on an excitation signal from the first code sequence, and actuates a filter having the aforementioned first linear prediction coefficient with the excitation signal obtained from the information on the excitation signal, to generate a first speech signal. A gain code generating circuit calculates a gain minimizing the distance between a second speech signal, generated from the information, obtained from the second code sequence, and the first speech signal (optimum gain), and corrects the optimum gain and the gain code generating circuit then finds the gain information in the second code sequence, based on the optimum gain as corrected (optimum gain corrected), the above optimum gain and a gain read out from a gain codebook of the second system. The gain is found at this time, in a non-speech segment, based on a speech decision value, using an evaluation function which will reduce time variations of the gain of the second system.
6 Citations
22 Claims
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1. A code converting method for converting a first code sequence conforming to a first system to a second code sequence conforming to a second system, comprising the steps of:
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acquiring a first linear prediction coefficient and first information on an excitation signal from said first code sequence and actuating a filter having said first linear prediction coefficient with the excitation signal obtained from said first information to generate a first speech signal; deriving an optimum gain based on a second speech signal generated by second information obtained from said second code sequence, and based on said first speech signal; correcting said optimum gain to generate corrected optimum gain; and finding gain information in said second code sequence based on said corrected optimum gain, said optimum gain and on a gain read out from a gain codebook for said second system. - View Dependent Claims (2, 3, 4, 5, 6, 7)
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8. A code converting apparatus for converting a first code sequence conforming to a first system to a second code sequence conforming to a second system, said apparatus comprising:
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a speech decoding circuit for acquiring a first linear prediction coefficient and first information on an excitation signal from said first code sequence and actuating a filter having said first linear prediction coefficient with the excitation signal obtained from said first information to generate a first speech signal; an optimum gain calculating circuit for calculating an optimum gain based on a second speech signal generated by second information obtained from said second code sequence, and based on said first speech signal; an optimum gain correcting circuit for correcting said optimum gain to generate corrected optimum gain; and a gain encoding circuit for finding the gain information in said second code sequence based on said corrected optimum gain, said optimum gain and on a gain read out from a gain codebook for said second system. - View Dependent Claims (9, 10, 11, 12, 13, 14)
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15. A computer program product in a medium used by a computer that composes a code converting apparatus for converting a first code sequence, conforming to a first system, into a second code sequence conforming to a second system, comprising a program for causing said computer to execute:
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(a) the processing of acquiring first linear prediction coefficient and first information on an excitation signal from said first code sequence and actuating a filter having said first linear prediction coefficient with the excitation signal obtained from said first information to generate a first speech signal; (b) the processing of calculating an optimum gain based on a second speech signal generated by second information obtained from a second code sequence, and based on said first speech signal; (c) the processing of correcting said optimum gain to generate corrected optimum gain; and (d) the processing of finding the gain information in said second code sequence based on said corrected optimum gain, said optimum gain and on a gain read out from a gain codebook for said second system. - View Dependent Claims (16, 17, 18, 19, 20, 21, 22)
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Specification