LSP prediction coding utilizing a determined best prediction matrix based upon past frame information

• US 6,088,667 A
• Filed: 02/13/1998
• Issued: 07/11/2000
• Est. Priority Date: 02/13/1997
• Status: Expired due to Fees

• Current Assignee: NEC Corporation
• Original Assignee: NEC Corporation
• Inventors: Murashima, Atsushi
• Primary Examiner(s): Zele, Krista
• Assistant Examiner(s): Opsasnick, Michael N.
• Application Number:
  US09/023,642
• Time in Patent Office: 879 Days
• Field of Search: 704/219, 704/220, 704/221, 704/222, 704/262
• US Class Current: 704/219
• CPC Class Codes: G10L 19/07 Line spectrum pair [LSP] vocoders

Abstract

An input vector is supplied from an input terminal 213. A first memory 213 accumulates a codevector from a quantizer. An adder 130 adds together the codevector and a Predicted vector from a predictor, and provides an output vector thus obtained to an output terminal 214. A second memory 214 accumulates the output vector. A prediction coefficient calculator calculates and provides a prediction coefficient matrix having the best evaluation value from the codevectors of a plurality of frames and the output vector. The predictor receives the codevectors of a plurality of selected past frames and the prediction coefficient matrix, and provides the predicted vector. A subtracter provides a difference vector between the input vector and the predicted vector. The quantizer obtains and provides the codevector by quantizing the difference vector.

Claims

1. A method for coding an input vector of a present frame using LSP prediction coding, the method comprising the acts of:

accumulating codevectors for frames previous to the present frame to produce accumulated codevectors, each codevector being produced by quantizing the difference between a prediction vector and an input vector of a respective frame;

accumulating output vectors for frames previous to the present frame to produce accumulated output vectors, each output vector being produced by adding the prediction vector and the codevector of a respective frame;

calculating a prediction coefficient matrix for the present frame from the accumulated codevectors and the accumulated output vectors;

calculating the prediction vector for the present frame from the accumulated codevectors and from the prediction coefficient matrix of the present frame, the prediction vector being used to predict the input vector of the present frame;

calculating the codevector of the present frame by quantizing the difference between the prediction vector and the input vector of the present frame; and

calculating an output vector of the present frame by adding together the prediction vector and the codevector of the present frame.

2. A method for coding, an input vector of a present frame using LSP prediction coding the method comprising the acts of:

accumulating codevectors for frames previous to the present frame to produce accumulated codevectors, each codevector being produced by quantizing the difference between a prediction vector and an input vector of a respective frame;

accumulating output vectors for frames previous to the present frame to produce accumulated output vectors, each output vector being produced by adding the prediction vector and the codevector of a respective frame;

calculating a prediction coefficient matrix for the present frame from the accumulated codevectors and the accumulated output vectors;

calculating the prediction vector for the present frame from the accumulated codevectors and from the calculated prediction coefficient matrix of the present frame, the prediction vector being used to predict the input vector of the present frame;

calculating the codevector of the present frame by quantizing the difference between the prediction vector and the input vector of the present frame;

calculating an output vector of the present frame by adding together the prediction vector and the codevector of the present frame;

accumulating input speech signals for frames previous to the present frame to produce accumulated input speech signals;

receiving an input speech signal of the present frame;

calculating a pitch predicted gain for the present frame from the input speech signal of the present frame and from the accumulated input speech signals; and

determining a control signal for the present frame from the pitch predicted gain of the present frame.

3. A method for coding an input vector of a present frame using LSP prediction coding, the method comprising the acts of:

accumulating codevectors for frames previous to the present frame to produce accumulated codevectors, each codevector being produced by quantizing the difference between a prediction vector and an input vector of a respective frame;

accumulating output vectors for frames previous to the present frame to produce accumulated output vectors, each output vector being produced by adding the prediction vector and the codevector of a respective frame;

calculating a prediction coefficient matrix for the present frame from the accumulated codevectors and the accumulated output vectors;

calculating the prediction vector for the present frame from the accumulated codevectors and from the prediction coefficient matrix of the present frame, the prediction vector being used to predict the input vector of the present frame;

calculating the codevector of the present frame by quantizing the difference between the prediction vector and the input vector of the present frame;

calculating an output vector of the present frame by adding together the prediction vector and the codevector of the present frame;

accumulating input speech signals from frames previous to the present frame to produce accumulated input speech signals;

receiving an input speech signal of the present frame;

calculating a pitch predicted gain for the present frame from the input speech signal of the present frame and from the accumulated input speech signals;

accumulating control signals for frames previous to the present frame to produce accumulated control signals, the control signals being determined from the pitch predicted gain of a respective frame, each control signal having a control signal value;

determining a control signal for the present frame from the pitch predicted gain of the present frame and the accumulated control signals;

substituting a prediction coefficient matrix of the frame immediately preceding the present frame for the prediction coefficient matrix of the present frame when all of the control signal values of the accumulated control signals, are not less than a predetermined threshold value.

4. A method for coding an input vector of a present frame using LSP prediction coding, the method comprising the acts of:

accumulating codevectors for frames previous to the present frame to produce accumulated codevectors, each codevector being produced by quantizing the difference between a prediction vector and an input vector of a respective frame;

accumulating output vectors for frames previous to the present frame to produce accumulated output vectors, each output vector being produced by adding the prediction vector and the codevector of a respective frame;

calculating a prediction coefficient matrix for the present frame from the accumulated codevectors and the accumulated output vectors;

calculating the prediction vector for the present frame from the accumulated codevectors and from the prediction coefficient matrix of the present frame;

calculating the codevector of the present frame by quantizing the difference between the prediction vector and the input vector of the present frame;

calculating an output vector of the present frame by adding together the prediction vector and the codevector of the present frame, the prediction vector being used to predict an input vector of the present frame;

accumulating input speech signals for frames previous to the present frame to produce accumulated input speech signals;

receiving an input speech signal of the present frame;

calculating a pitch predicted gain for the present frame from the input speech signal of the present frame and the accumulated input speech signals;

accumulating control signals for frames previous to the present frame to produce accumulated control signals, the control signals being determined from the pitch predicted gain of a respective frame;

determining a control signal for the present frame from the pitch predicted gain of the present frame and the accumulated control signals;

each control signal having a control signal value;

substituting a prediction coefficient matrix of the frame immediately preceding the present frame for the prediction coefficient matrix of the present frame, when all of the control signal values of the accumulated signals are not less than a predetermined first threshold value;

using the prediction coefficient matrix of the present frame, when a control signal value of any of the accumulated control signals is less than the first threshold value and the control signal value in the present frame is not less than a predetermined second threshold value;

setting the value of the prediction coefficient matrix of the present frame to be a zero matrix when any of the control signal values in the accumulated control signals is less than the first threshold value and the control signal value in the present frame is less than the second threshold value; and

switching from among a plurality of codevector tables used in calculating the codevector for the present frame when the control signal value in the present frame is less than the second threshold value.

5. A method for coding an input vector of a present frame using LSP prediction coding, the method comprising the acts of:

accumulating codevectors for frames previous to the present frame to produce accumulated codevectors, each codevector being produced by quantizing the difference between a prediction vector and an input vector of a respective frame;

accumulating output vectors for frames previous to the present frame to produce accumulated output vectors, each output vector being produced by adding the prediction vector and the codevector of a respective frame;

calculating a prediction coefficient matrix for the present frame from the accumulated codevectors and the accumulated output vectors;

calculating the prediction vector for the present frame from the accumulated codevectors and from the prediction coefficient matrix of the present frame, the prediction vector being used to predict an input vector of the present frame;

calculating the codevector of the present frame by quantizing the difference between the prediction vector and the input vector of the present frame;

calculating an output vector of the present frame by adding together the prediction vector and the codevector of the present frame;

accumulating input speech signal for frames previous to the present frame to produce accumulated input speech signals;

receiving an input speech signal of the present frame;

calculating a pitch predicted gain for the present frame from the input signal of the present frame and from the accumulated input speech signals;

accumulating control signals for frames previous to the present frame to produce accumulated control signals;

determining a control signal for the present frame from the pitch predicted gain for the present frame and the accumulated control signals, each control signal having a control signal value;

substituting a predetermined coefficient matrix of the frame immediately preceding the present frame for the prediction coefficient matrix of the present frame, when all of the control signal values of the accumulated control signals are not less than a predetermined threshold value; and

using the prediction coefficient matrix of the present frame when a control signal value of any of the accumulated control signals is less than the predetermined threshold value.

6. A method for coding an input vector of a present frame using LSP prediction coding, the method comprising the acts of:

accumulating codevectors for frames previous to the present frame to produce accumulated codevectors, each codevector being produced by quantizing the difference between a prediction vector and an input vector of a respective frame;

accumulating output vectors for frames previous to the present frame to produce accumulated output vectors, each output vector being produced by adding the prediction vector and the codevector of a respective frame;

calculating a prediction coefficient matrix for the present frame from the accumulated codevectors and the accumulated output vectors;

calculating the prediction vector for the present frame from the accumulated codevectors and from the prediction coefficient matrix of the present frame, said prediction vector used to predict an input vector of a present frame;

calculating the codevector of the present frame by quantizing the difference between the prediction vector and the input vector of the present frame;

calculating an output vector of the present frame by adding together the prediction vector and the codevector of the present frame;

accumulating input speech signals for frames previous to the present frame to produce accumulated input speech signals;

receiving an input speech signal of the present frame;

calculating a pitch predicted gain for the present frame from the input speech signal of the present frame and from the accumulated input speech signals;

accumulating control signals for frames previous to the present frame to produce accumulated control signals;

determining a control signal for the present frame from the pitch predicted gain of the present frame and the accumulated control signals;

each control signal having a control signal value;

substituting a prediction coefficient matrix of the immediately preceding frame for the prediction coefficient matrix of the present frame, when all of the control signal values of the accumulated control signals are not less than a predetermined first threshold value;

using the prediction coefficient matrix of the present frame, when a control signal value of any of the accumulated control signals is less than the first threshold value and the control signal value in the present frame is not less than a predetermined second threshold value;

setting the value of the prediction coefficient matrix of the present frame to be a zero matrix when any of the control signal values in the accumulated control signals is less than the first threshold value and the control signal value in the present frame is less than the second threshold value; and

switching from among a plurality of codevector tables used in calculating the codevector for the present frame when the control signal value in the present frame is less than the second threshold value.

7. A method for coding an input vector of a present frame using LSP prediction coding, the method comprising the acts of:

accumulating output vectors for frames previous to the present frame to produce accumulated output vectors, each output vector being produced by quantizing the difference between a prediction vector and a codevector of a respective frame;

accumulating output vectors for frames previous to the present frame to produce accumulated output vectors, each output vector being produced by adding the prediction vector and the codevector of a respective frame;

calculating a prediction coefficient matrix for the present frame from the accumulated codevectors and the accumulated output vectors;

calculating the prediction vector for the present frame from the accumulated output vectors and from the prediction coefficient matrix of the present frame, the prediction vector being used to predict the input vector of the present frame;

calculating the codevector of the present frame by quantizing the difference between the prediction vector and the input vector of the present frame; and

calculating an output vector of the present frame by adding together the prediction vector and the codevector of the present frame.

8. A method for coding an input vector of a present frame using LSP prediction coding, the method comprising the acts of:

accumulating codevectors for frames previous to the present frame to produce accumulated codevectors, each codevector being produced by quantizing the difference between a prediction vector and the codevector for a respective frame;

accumulating output vectors for frames previous to the present frame to produce accumulated output vectors, each output vector being produced by adding the prediction vector and the codevector of a respective frame;

calculating a prediction coefficient matrix for the present frame from the accumulated codevectors and the accumulated output vectors;

calculating the prediction vector for the present frame from the accumulated output vectors and from the calculated prediction coefficient matrix of the present frame, the prediction vector being used to predict the input vector of the present frame;

calculating the codevector of the present frame by quantizing the difference between the prediction vector and the input vector of the present frame;

calculating an output vector of the present frame by adding together the prediction vector and the codevector of the present frame;

accumulating input speech signals for frames previous to the present frame to produce accumulated input speech signals;

receiving an input speech signal of the present frames;

calculating a pitch predicted gain for the present frame from the input speech signal of the present frame and from the accumulated input speech signals; and

determining a control signal for the present frame from the pitch predicted gain of the present frame.

9. A method for coding an input vector of a present frame using LSP prediction coding, the method comprising the acts of:

accumulating codevectors for frames previous to the present frame to produce accumulated codevectors, each codevector being produced by quantizing the difference between a prediction vector and an input vector of a respective frame;

accumulating output vectors for frames previous to the present frame to produce accumulated output vectors, each output vector being produced by adding the prediction vector and the codevector of a respective frame;

calculating a prediction coefficient matrix for the present frame from the accumulated codevectors and the accumulated output vectors;

calculating the prediction vector for the present frame from the accumulated output vectors and from the prediction coefficient matrix of the present frame, the prediction vector being used to predict the input vector of the present frame;

calculating the codevector of the present frame by quantizing the difference between the prediction vector and the input vector of the present frame;

calculating an output vector of the present frame by adding together the prediction vector and the codevector of the present frame;

accumulating input speech signals from frames previous to the present frame to produce accumulated input speech signals;

receiving an input speech signal of the present frame;

calculating a pitch predicted gain for the present frame from the input speech signal of the present frame and from the accumulated input speech signals;

accumulating control signals for frames previous to the present frame to produce accumulated control signals, the control signals being determined from the pitch predicted gain of a respective frame, each control signal having a control signal value;

determining a control signal for the present frame from the pitch predicted gain of the present frame and the accumulated control signals;

substituting a prediction coefficient matrix of the frame immediately preceding the present frame for the prediction coefficient matrix of the present frame when all of the control signal values of the accumulated control signals, are not less than a predetermined threshold value.

10. A method for coding an input vector of a present frame using LSP prediction coding, the method comprising the acts of:

accumulating codevectors for frames previous to the present frame to produce accumulated codevectors, each codevector being produced by quantizing the difference between a prediction vector and an input vector of a respective frame;

accumulating output vectors for frames previous to the present frame to produce accumulated output vectors, each output vector being produced by adding the prediction vector and the codevector of a respective frame;

calculating a prediction coefficient matrix for the present frame from the accumulated codevectors and the accumulated output vectors;

calculating the prediction vector for the present frame from the accumulated output vectors and from the prediction coefficient matrix of the present frame;

calculating the codevector of the present frame by quantizing the difference between the prediction vector and the input vector of the present frame;

calculating an output vector of the present frame by adding together the prediction vector and the codevector of the present frame, the prediction vector being used to predict an input vector of the present frame;

accumulating input speech signals for frames previous to the present frame to produce accumulated input speech signals;

receiving an input speech signal of the present frame;

calculating a pitch predicted gain for the present frame from the input speech signal of the present frame and the accumulated input speech signals;

accumulating control signals for frames previous to the present frame to produce accumulated control signals, the control signals being determined from the pitch predicted gain of a respective frame;

determining a control signal for the present frame from the pitch predicted gain of the present frame and the accumulated control signals;

each control signal having a control signal value;

substituting a prediction coefficient matrix of the frame immediately preceding the present frame for the prediction coefficient matrix of the present frame, when all of the control signal values of the accumulated signals are not less than a predetermined first threshold value;

using the prediction coefficient matrix of the present frame, when a control signal value of any of the accumulated control signals is less than the first threshold value and the control signal value in the present frame is not less than a predetermined second threshold value;

setting the value of the prediction coefficient matrix of the present frame to be a zero matrix when any of the control signal values in the accumulated control signals is less than the first threshold value and the control signal value in the present frame is less than the second threshold value; and

switching from among a plurality of codevector tables used in calculating the codevector for the present frame when the control signal value in the present frame is less than the second threshold value.

11. A method for coding an input vector of a present frame using LSP prediction coding, the method comprising the acts of:

accumulating codevectors for frames previous to the present frame to produce accumulated codevectors, each codevector being produced by quantizing the difference between a prediction vector and an input vector of a respective frame;

accumulating output vectors for frames previous to the present frame to produce accumulated output vectors, each output vector being produced by adding the prediction vector and the codevector of a respective frame;

calculating a prediction coefficient matrix for the present frame from the accumulated codevectors and the accumulated output vectors;

calculating the prediction vector for the present frame from the accumulated output vectors and from the prediction coefficient matrix of the present frame, the prediction vector being used to predict an input vector of the present frame;

calculating the codevector of the present frame by quantizing the difference between the prediction vector and the input vector of the present frame;

calculating an output vector of the present frame by adding together the prediction vector and the codevector of the present frame;

accumulating input speech signal for frames previous to the present frame to produce accumulated input speech signals;

receiving an input speech signal of the present frame;

calculating a pitch predicted gain for the present frame from the input signal of the present frame and from the accumulated input speech signals;

accumulating control signals for frames previous to the present frame to produce accumulated control signals;

determining a control signal for the present frame from the pitch predicted gain for the present frame and the accumulated control signals, each control signal having a control signal value;

substituting, a predetermined coefficient matrix of the frame immediately preceding the present frame for the prediction coefficient matrix of the present frame, when all of the control signal values of the accumulated signals are not less than a predetermined threshold value; and

using the prediction coefficient matrix of the present frame when a control signal value of any of the accumulated control signals is less than the predetermined threshold value.

12. A method for coding an input vector of a present frame using LSP prediction coding, the method comprising the of:

accumulating codevectors for frames previous to the present frame to produce accumulated codevectors, each codevector being produced by quantizing the difference between a prediction vector and an input vector of a respective frame;

accumulating output vectors for frames previous to the present frame to produce accumulated output vectors each output vector being produced by adding the prediction vector and the codevector of a respective frame;

calculating a prediction coefficient matrix for the present frame from the accumulated codevectors and the accumulated output vectors;

calculating the prediction vector for the present frame from the accumulated output vectors and from the prediction coefficient matrix of the present frame, said prediction vector used to predict an input vector of a present frame;

calculating the codevector of the present frame by quantizing the difference between the prediction vector and the input vector of the present frame;

calculating an output vector of the present frame by adding together the prediction vector and the codevector of the present frame;

accumulating input speech signals for frames previous to the present frame to produce accumulated input speech signals;

receiving an input speech signal of the present frame;

calculating a pitch predicted gain for the present frame from the input speech signal of the present frame and from the accumulated input speech signals;

accumulating control signals for frames previous to the present frame to produce accumulated control signals;

determining a control signal for the present frame from the pitch predicted gain of the present frame and the accumulated control signals;

each control signal having a control signal value;

substituting a prediction coefficient matrix of the immediately preceding frame for the prediction coefficient matrix of the present frame, when all of the control signal values of the accumulated signals are not less than a predetermined first threshold value;

using the prediction coefficient matrix of the present frame, when a control signal value of any of the accumulated control signals is less than the first threshold value and the control signal value in the present frame is not less than a predetermined second threshold value;

setting the value of the prediction coefficient matrix of the present frame to be a zero matrix when any of the control signal values in said plurality of continuous frames are the accumulated control signals is less than the first threshold value and the control signal value in the present frame is less than the second threshold value; and

switching from among a plurality of codevector tables used in calculating the codevector for the present frame when the control signal value in the present frame is less than the second threshold value.

13. An LSP prediction coding apparatus for coding an input vector of a present frame, said coding apparatus comprising:

a first memory which stores codevectors for frames previous to the present frame to produce accumulated codevectors, each codevector being produced by quantizing the difference between a prediction vector and an input vector of a respective frame;

a second memory which stores output vectors for frames previous to the present frame to produce accumulated output vectors, each output vector being produced by adding the prediction vector and the codevector of a respective frame;

a prediction coefficient calculator which calculates a prediction coefficient matrix for the present frame from the accumulated codevectors and the accumulated output vectors;

a predictor which calculates a predicted vector for the present frame from the accumulated codevectors and from the prediction coefficient matrix of the present frame;

a quantizer which produces the codevector for the present frame by quantizing the difference between the predicted vector and the input vector of the present frame; and

an adder which adds together the prediction vector and the codevector of the present frame to produce an output vector of the present frame.

14. An LSP prediction coding apparatus for coding an input vector of a present frame, said coding apparatus comprising:

a first memory which stores codevectors for frames previous to the present frame to produce accumulated codevectors each codevector being produced by quantizing the difference between a prediction vector and an input vector of a respective frame;

a second memory which stores output vectors for frames previous to the present frame to produce accumulated output vectors each output vector being produced by adding the prediction vector and the codevector of a respective frame;

a prediction coefficient calculator which calculates a prediction coefficient matrix for the present frame from the accumulated codevectors and the accumulated output vectors;

a predictor which calculates a predicted vector for the present frame from the accumulated codevectors and from the prediction coefficient matrix of the present frame;

a third memory which stores input speech signals for frames previous to the present frame to produce accumulated speech signals;

a quantizer which produces the codevector for the present frame by quantizing the difference between the predicted vector and an input vector of the present frame;

a processor which calculates a pitch predicted gain from an input speech signal of the present frame and from the accumulated input speech signals, the processor further determines a control signal from the pitch predicted gain;

an integration interval determiner which determines an integration interval from the control signal; and

an adder which adds together the prediction vector and the codevector of the present frame to produce an output vector of the present frame;

wherein

the quantizer switches among a plurality of codevector tables used in calculating the codevector for the present frame when the control signal is less than a threshold value.

15. An LSP prediction coding apparatus for coding an input vector of a present frame, said coding apparatus comprising:

a first memory which stores codevectors for frames previous to the present frame to produce accumulated codevectors, each codevector being produced by quantizing the difference between a prediction vector and an input vector of a respective frame;

a second memory which stores output vectors for frames previous to the present frame to produce accumulated output vectors each output vector being produced by adding the prediction vector and the codevector of a respective frame;

a prediction coefficient calculator which calculates a prediction coefficient matrix for the present frame from the accumulated codevectors and the accumulated output vectors;

a predictor which calculates a predicted vector for the present frame from the accumulated codevectors and from the prediction coefficient matrix of the present frame;

a quantizer which produces the codevector for the present frame by quantizing the difference between the predicted vector and an input vector of the present frame;

a third memory which stores input speech signals for frames previous to the present frame to produce accumulated speech signals;

a processor which calculates a pitch predicted gain for the present frame from an input speech signal of the present frame and from the accumulated speech signals;

a fourth memory which stores control signals for frames previous to the present frame to produce accumulated control signals, the control signals being determined from the pitch predicted gain of a respective frame;

the processor further determines a control signal for the present frame from the pitch predicted gain of the present frame and from the accumulated control signals;

each control signal having a control signal value; and

an adder which adds together the prediction vector and the codevector of the present frame to produce an output vector of the present frame;

wherein

the coefficient matrix calculator uses the prediction coefficient matrix of the present frame when any one of the accumulated control signal values is less than a predetermined threshold value, and wherein the coefficient matrix calculator substitutes a prediction coefficient matrix of a frame immediately preceding the present frame for the prediction coefficient matrix of the present frame when all of the control signal values of the accumulated control signals are not less than the threshold value.

16. The LSP prediction coding apparatus according to claim 15, further comprising:

an integration interval determiner which determines an integration interval from the control signal of the present frame; and

wherein the accumulated codevectors and output vectors are determined by the integration interval.

17. An LSP prediction coding apparatus for coding an input vector of a present frame, said coding apparatus comprising:

a first memory which stores codevectors for frames previous to the present frame to produce accumulated codevectors, each codevector being produced by quantizing the difference between a prediction vector and an input vector of a respective frame;

a second memory which stores output vectors for frames previous to the present frame to produce accumulated output vectors, each output vector being produced by adding the prediction vector and the codevector of a respective frame;

a prediction coefficient calculator which calculates a prediction coefficient matrix for the present frame from the accumulated codevectors and the accumulated output vectors;

a predictor which calculates a predicted vector for the present frame from the accumulated codevectors and from the prediction coefficient matrix of the present frame;

a third memory which stores input speech signals for frames previous to the present frame to produce accumulated speech signals;

a quantizer which produces the codevector for the present frame by quantizing the difference between the predicted vector and an input vector of the present frame;

a processor which calculates a pitch predicted gain for the present frame from an input speech signal of the present frame and from the accumulated input speech signals;

a fourth memory which stores control signals for frames previous to the present frame to produce accumulated control signals, the control signals being determined from the pitch predicted gain of a respective frame;

the processor further determines a control signal for the present frame from the pitch predicted gain of the present frame and from the accumulated control signals;

each control signal having a control signal value; and

an adder which adds together the prediction vector and the codevector of the present frame to produce an output vector of the present frame;

wherein

the coefficient matrix calculator uses the prediction coefficient matrix of the present frame when any one of the accumulated control signal values is less than a predetermined first threshold value and the control signal value in the present frame is not less than a predetermined second threshold value, wherein the coefficient matrix calculator substitutes a prediction coefficient matrix of a frame immediately preceding the present frame for the prediction coefficient matrix of the present frame when all of the accumulated control signal values are not less than the first threshold value and wherein the coefficient matrix calculator sets the value of the prediction coefficient matrix to be a zero matrix when any of the control signal values of the accumulated signals is is less than the first threshold value and the control signal value in the present frame is less than the second threshold value; and

wherein

the quantizer switches among a plurality of codevector tables when the control signal valve in the present frame is less than the second threshold value.

18. The LSP prediction coding apparatus according to claim 17, further comprising:

an integration interval determiner which determines an integration interval from the control signal of the present frame; and

wherein the accumulated codevectors and output vectors are determined by the integration interval.