CODING METHOD, DECODING METHOD, APPARATUS, PROGRAM, AND RECORDING MEDIUM

• US 20130034168A1
• Filed: 02/07/2011
• Published: 02/07/2013
• Est. Priority Date: 03/09/2010
• Status: Active Application

• Current Assignee: Nippon Telegraph and Telephone Corporation
• Original Assignee: Nippon Telegraph and Telephone Corporation
• Inventors: Fukui, Masahiro, Sasaki, Shigeaki, Hiwasaki, Yusuke, Tsutsumi, Kimitaka, Koyama, Shoichi
• Granted Patent: US 10,269,363 B2
• Time in Patent Office: Days
• US Class Current: 375/240.22
• CPC Class Codes: G10L 19/038 Vector quantisation, e.g. TwinVQ audio

Abstract

A normalization value calculator 12 calculates a normalization value that is representative of a predetermined number of input samples. A normalization value quantizer 13 quantizes the normalization value to obtain a quantized normalization value and a normalization-value quantization index corresponding to the quantized normalization value. An quantization-candidate calculator 14 subtracts a value corresponding to the quantized normalization value from a value corresponding to the magnitude of each of the samples to obtain a difference value and, when the difference value is positive and the value of each of the samples is positive, sets the difference value as an quantization candidate corresponding to the sample. When the difference value is positive and the value of each of the samples is negative, the quantization-candidate calculator 14 reverses the sign of the difference value and setting the sign-reversed value as an quantization candidate corresponding to the sample. When the difference value is not positive, the quantization-candidate calculator 14 sets 0 as an quantization candidate corresponding to the sample. A vector quantizer 15 jointly vector-quantizes a plurality of quantization candidates corresponding to a plurality of samples to obtain a vector quantization index.

Claims

1. A coding method comprising:

a normalization value calculation step of calculating a normalization representative value representative of a predetermined number of input samples;

a normalization value quantization step of quantizing the normalization value to obtain a quantized normalization value and a normalization-value quantization index corresponding to the quantized normalization value;

an quantization-candidate calculation step of subtracting a value corresponding to the quantized normalization value from a value corresponding to the magnitude of each of the samples to obtain a difference value and, when the difference value is positive and the value of each of the samples is positive, setting the difference value as an quantization candidate corresponding to the sample, when the difference value is positive and the value of each of the samples is negative, reversing the sign of the difference value and setting the sign-reversed value as an quantization candidate corresponding to the sample, and when the difference value is not positive, setting 0 as an quantization candidate corresponding to the sample; and

a vector quantization step of jointly vector-quantizing a plurality of quantization candidates corresponding to a plurality of samples to obtain a vector quantization index.

2. The coding method according to claim 1, wherein:

the value corresponding to the magnitude of the sample is the absolute value of the value of the sample; and

the value corresponding to the quantized normalization value is the product of the quantized normalization value and an adjustment constant C₁, the adjustment constant C₁ being a predetermined positive value.

3. The coding method according to claim 1 or 2, further comprising an quantization-candidate normalization value calculation step of calculating an quantization-candidate normalization value, the quantization-candidate normalization value being representative of the quantization candidates;

wherein the vector quantization step jointly vector-quantizes normalized values to obtain a vector quantization index, the normalized values obtained by normalizing a plurality of quantization candidates corresponding to the plurality of samples with the quantization-candidate normalization value.

4. The coding method according to claim 3, wherein the quantization-candidate normalization value is the product of the quantized normalization value and a predetermined adjustment constant C₂.

21. A program for causing a computer to executes the steps of the method according to claim 1 or 23.

22. A computer-readable recording medium on which the program according to claim 21 is recorded.

5. A decoding method comprising:

a normalization value decoding step of obtaining a decoded normalization value corresponding to an input normalization-value quantization index;

a vector decoding step of obtaining a plurality of values corresponding to an input vector quantization index as a plurality of decoded values;

a normalization value recalculation step of calculating a recalculated normalization value, the recalculated normalization value taking on a value decreasing with increasing sum of the absolute values of a predetermined number of the decoded values; and

a combining step of, when the decoded value is zero, obtaining as a decoded signal a value having an absolute value that is the recalculated normalization value multiplied by a first constant, and when the decoded value is not zero, obtaining as a decoded signal the linear sum of the decoded value or the absolute value of the decoded value and the decoded normalization value, the linear sum reflecting the sign of the decoded value.

10. (canceled)

11. A coding apparatus comprising:

a normalization value calculator calculating a normalization representative value representative of a predetermined number of input samples;

a normalization value quantizer quantizing the normalization value to obtain a quantized normalization value and a normalization-value quantization index corresponding to the quantized normalization value;

an quantization-candidate calculator subtracting a value corresponding to the quantized normalization value from a value corresponding to the magnitude of each of the samples to obtain a difference value and, when the difference value is positive and the value of each of the samples is positive, setting the difference value as an quantization candidate corresponding to the sample, when the difference value is positive and the value of each of the samples is negative, reversing the sign of the difference value and setting the sign-reversed value as an quantization candidate corresponding to the sample, and when the difference value is not positive, setting 0 as an quantization candidate corresponding to the sample; and

a vector quantizer jointly vector-quantizing a plurality of quantization candidates corresponding to a plurality of samples to obtain a vector quantization index.

12. The coding apparatus according to claim 11, wherein:

the value corresponding to the magnitude of the sample is the absolute value of the value of the sample; and

the value corresponding to the quantized normalization value is the product of the quantized normalization value and an adjustment constant C₁, the adjustment constant C₁ being a predetermined positive value.

13. The coding apparatus according to claim 11 or 12, further comprising an quantization-candidate normalization value calculator calculating an quantization-candidate normalization value, the quantization-candidate normalization value being representative of the quantization candidates;

wherein the vector quantizer jointly vector-quantizes normalized values to obtain a vector quantization index, the normalized values obtained by normalizing a plurality of quantization candidates corresponding to the plurality of samples with the quantization-candidate normalization value.

14. The coding apparatus according to claim 13, wherein the quantization-candidate normalization value is the product of the quantized normalization value and a predetermined adjustment constant C₂.

15. A decoding apparatus comprising:

a normalization value decoder obtaining a decoded normalization value corresponding to an input normalization-value quantization index;

a vector decoder obtaining a plurality of values corresponding to an input vector quantization index as a plurality of decoded values;

a normalization value recalculator calculating a recalculated normalization value, the recalculated normalization value taking on a value decreasing with increasing sum of the absolute values of a predetermined number of the decoded values; and

a synthesizer, when the decoded value is zero, obtaining as a decoded signal a value having an absolute value that is the recalculated normalization value multiplied by a first constant, and when the decoded value is not zero, obtaining as a decoded signal the linear sum of the decoded value or the absolute value of the decoded value and the decoded normalization value, the linear sum reflecting the sign of the decoded value.

16. The decoding apparatus according to claim 15 or 24, wherein the value having an absolute value that is the recalculated normalization value multiplied by the first constant is the recalculated normalization value multiplied by the first constant and has a randomly reversed sign.

17. The decoding apparatus according to claim 15 or 24, wherein:

the normalization value recalculator calculates the recalculated normalization value that is X⁼ defined by the following equation

18. The decoding apparatus according to claim 15 or 24, wherein when each of the decoded values is not zero, the synthesizer adds the absolute value of the decoded value to the decoded normalization value multiplied by an adjustment constant C₁ and multiplies the resulting value by the sign of the decoded value to obtain a decoded signal, the adjustment constant C₁ being a predetermined positive value.

19. The decoding apparatus according to claim 15 or 24, wherein when the recalculated normalization value is not zero, the normalization value recalculator obtains as the recalculated normalization value a weighted sum of the recalculated normalization value and a recalculated normalization value obtained in the immediately preceding recalculation.

20. (canceled)

23. A decoding method comprising:

a normalization value decoding step of obtaining a decoded normalization value corresponding to an input normalization-value quantization index;

a decoding-candidate normalization value calculating step of multiplying the decoded normalization value by a second constant to obtain a decoding-candidate normalization value;

the vector decoding step of multiplying each of a plurality of values corresponding to an input vector quantization index by the decoding-candidate normalization value to obtain a plurality of decoded values;

a normalization value recalculation step of calculating a recalculated normalization value, the recalculated normalization value taking on a value decreasing with increasing sum of the absolute values of a predetermined number of the decoded values; and

a combining step of, when the decoded value is zero, obtaining as a decoded signal a value having an absolute value that is the recalculated normalization value multiplied by a first constant, and when the decoded value is not zero, obtaining as a decoded signal the linear sum of the decoded value or the absolute value of the decoded value and the decoded normalization value, the linear sum reflecting the sign of the decoded value.

6. The decoding method according to claim 5 or 23, wherein the value having an absolute value that is the recalculated normalization value multiplied by the first constant is the recalculated normalization value multiplied by the first constant and has a randomly reversed sign.

7. The decoding method according to claim 5 or 23, wherein:

the normalization value recalculation step calculates the recalculated normalization value that is X⁼ defined by the following equation

8. The decoding method according to claim 5 or 23, wherein when each of the decoded values is not zero, the combining step adds the absolute value of the decoded value to the decoded normalization value multiplied by an adjustment constant C₁ and multiplies the resulting value by the sign of the decoded value to obtain a decoded signal, the adjustment constant C₁ being a predetermined positive value.

9. The decoding method according to claim 5 or 23, wherein when the recalculated normalization value is not zero, the normalization value recalculation step obtains as the recalculated normalization value a weighted sum of the recalculated normalization value and a recalculated normalization value obtained in the immediately preceding recalculation.

24. A decoding apparatus comprising:

a normalization value decoder obtaining a decoded normalization value corresponding to an input normalization-value quantization index;

a decoding-candidate normalization value calculator multiplying the decoded normalization value by a second constant to obtain a decoding-candidate normalization value;

the vector decoder multiplying each of a plurality of values corresponding to an input vector quantization index by the decoding-candidate normalization value to obtain a plurality of decoded values;

a normalization value recalculator calculating a recalculated normalization value, the recalculated normalization value taking on a value decreasing with increasing sum of the absolute values of a predetermined number of the decoded values; and

a synthesizer, when the decoded value is zero, obtaining as a decoded signal a value having an absolute value that is the recalculated normalization value multiplied by a first constant, and when the decoded value is not zero, obtaining as a decoded signal the linear sum of the decoded value or the absolute value of the decoded value and the decoded normalization value, the linear sum reflecting the sign of the decoded value.