A speech coding/decoding system

Claim 2

(2) A speech coding/decoding system comprising; a coding side including; a predictor (6,10) for providing a predicted signal of a digital input speech signal based upon a prediction parameter which is provided by a prediction parameter means (1,2,3,4;7,8,9) for outputting said prediction parameter, a quantizer (16) for quantizing a residual signal, said residual signal being obtained by subtracting said digital input speech signal from said prediction signal, and a shaped quantization noise, a multiplexer (30) for multiplexing at the output of said quantizer (16) as codes of residual signal, and side information for sending to a receiver; a decoding side including; a demultiplexer (33) for separating said codes of residual signal and the side information, an inverse quantizer (36) for inverse quantization and for decoding of a quantized residual signal from a transmitter side, a prediction parameter decoder (38) coupled with output of said demultiplexer (33) for decoding a prediction parameter from a transmit side, a synthesis filter (42,43) for reproducing said digital input signal by adding an output of said inverse quantizer (36) and a reproduced predicted signal, wherein a first leakage selector (47) is provided in a coding side for adaptively adjusting a coefficient of said predictor (6) based upon said prediction parameter and, a second leakage selector (48) is provided in a decoding side for adaptively adjusting a coefficient of said synthesis filter (43) based upon output of said prediction parameter decoder (38), value of leakage of said first leakage selector (47) and said second leakage selector (48) is larger than 0 and smaller than 1, depending upon prediction gain which is the result of said prediction parameter means (4,38).

Claim 3

(3) A speech coding/decoding system according to claim 2, wherein value of leakage of said second leakage selector (48) on a decoding side is larger than that of said first leakage selector (47) in a coding side.

Claim 4

(4) A speech coding/decoding system according to claim 1, wherein a level adjuster (45) is provided on a decoding side, and said level adjuster functions to compensate gain difference between a coding side and a decoding side because of difference of leakages in both sides.

Claim 5

(5) A speech coding/decoding system according to claim 2, wherein each of said leakage value is switched between two values depending upon the accuracy of the prediction by the predictor.

Claim 6

(6) A speech coding/decoding system according to claim 2, wherein leakage value on a coding side is 0.9375, and leakage value in a decoding side is 0.963 when a prediction gain Gp is smaller than a predetermined value and 0.973 when said prediction gain Gp is larger than said predetermined value.

Claim 7

(7) A speech coding/decoding system according to claim 2, wherein each of said leakage value is selected among more than three values.

Claim 8

(8) A speech coding/decoding system according to claim 2, wherein each of said first leakage selector and said second leakage selector is implemented by a ROM.

Claim 9

(9) A speech coding system comprising; a predictor (6,10) for providing a predicted signal of a digital input speech signal in order to obtain a residual signal by removing correlations from said digital input speech signal, a quantizer (16) for quantizing said residual signal for sending to a receiver, wherein a first leakage selector (47) is provided in a coding side for adaptively adjusting a leakage which is weighting factor of said predictor (6) depending upon a prediction gain which indicates an accuracy of the prediction.

Claim 10

(10) A speech decoding system comprising; an inverse quantizer (36) for reproducing a quantized residual signal from coded residual signal from a transmitter side, a synthesis filter (40,41,42,43) for reproducing said digital input signal from said quantized residual signal, wherein a second leakage selector (48) is provided in a decoding side for adaptively adjusting a leakage which is weighting factor of said synthesis filter (43) depending upon a prediction gain which indicates an accuracy of the prediction.

Claim 11

(11) A speech coding/decoding system comprising; a coding side including; a predictor (6,10) for providing a predicted signal of a digital input speech signal in order to obtain a residual signal by removing correlations from said digital input speech signal, a quantizer (16) for quantizing said residual signal for sending to a receiver, a decoding side including; an inverse quantizer (36) for reproducing a quantized residual signal from coded residual signal from a transmitter side, a synthesis filter (40,41,42,43) for reproducing said digital input signal from said quantized residual signal, wherein a leakage of said synthesis filter (43) in a receive side is different from a leakage of said predictor (6) in a transmit side, wherein value of said leakage is larger than 0 and smaller than 1.

Claim 12

(12) A speech coding/decoding system according to claim 11, wherein value of leakage of said synthesis filter (43) is larger than that of said predictor (6).

Claim 13

(13) A speech coding/decoding system according to claim 11, wherein a level adjuster (45) is provided on a decoding side, and said level adjuster functions to compensate gain difference between a coding side and a decoding side because of difference of leakages in both sides.