Digital signal encoding method, decoding method, encoding device, decoding device, digital signal encoding program, and decoding program

• US 20050091051A1
• Filed: 03/10/2003
• Published: 04/28/2005
• Est. Priority Date: 03/08/2002
• Status: Active Grant

• Current Assignee: Nippon Telegraph and Telephone Corporation
• Original Assignee: Nippon Telegraph and Telephone Corporation
• Inventors: Mori, Takeshi, Moriya, Takehiro, Ikeda, Kazunaga, Jin, Akio
• Granted Patent: US 7,599,835 B2
• Time in Patent Office: Days
• US Class Current: 704/229
• CPC Class Codes: G10L 19/00 Speech or audio signals analysis-synthesis techniques for redundancy reduction, e.g. in vocoders; Coding or decoding of speech or audio signals, using source filter models or psychoacoustic analysis in musical instruments G10H
• CPC Class Codes: G10L 19/0017 Lossless audio signal coding; Perfect reconstruction of coded audio signal by transmission of coding error G10L19/24 takes precedence

Abstract

A down sampler 13 down samples a digital signal in the sampling frequency thereof from 96 kHz to 48 kHz on a frame-by-frame basis. The converted signal is compression encoded and output as a main code Im. An up sampler 16 converts a partial signal corresponding to the main code Im to a signal having the original sampling frequency 96 kHz, for example. An error signal between the up sampled signal and an input digital signal is generated. An array converting and encoding unit 18 array converts bits of sample chains of the error signal, thereby outputting an error code Pe. On a decoding side, a high fidelity reproduced signal is obtained based on the main code Im and the error code Pe, or a reproduced signal is obtained based on the main code Im only.

Claims

1. A digital signal encoding method comprising:

a step (a) for generating and encoding a signal lower in attribute rank than a signal to be encoded or a signal modified from the signal lower in attribute, and

a step (b) for lossless encoding an error signal between the signal to be encoded and one of the signal lower in attribute rank and the signal modified the signal lower in attribute rank.

2. A digital signal encoding method according to claim 1, wherein the step (a) comprises converting a digital signal at a first sample frequency to a digital signal at a second sampling frequency lower than the first sampling frequency on a frame-by-frame basis,

and compression encoding the digital signal at the second sampling frequency and then outputting the compression encoded digital signal as a main code, and

wherein the step (b) comprises converting a partial signal corresponding to the main code to a partial signal at the first sampling frequency,

calculating, as the error signal, an error signal between the partial signal at the first sampling frequency and the digital signal at the first sampling frequency,

generating a predictive error signal of the error signal, and

lossless encoding an equidistant bit string striding samples of the predictive error signal at each of bit positions that represent the amplitude of each sample of the predictive error signal, and outputting the encoded equidistant bit string as an error code.

3. A digital signal encoding method according to claim 1, wherein the step (b) comprises lossless encoding a predictive error signal of the error signal with the frequency axis thereof inverted.

4. A digital signal encoding method according to claim 2, wherein the step (b) comprises a step for converting the error signal to an error signal at a sampling frequency lower than the first sampling frequency,

a step for generating a predictive signal of the converted version of the error signal, and converting the predictive signal to a predictive signal at the first sampling frequency, and

a step for determining the predictive error signal from the converted version of the predictive signal and the error signal at the first sampling frequency.

5. A digital signal encoding method according to claim 2, wherein the step (b) comprises a step for linear predictive analyzing the error signal and generating a predictive signal by processing the error signal with a predictive coefficient of the linear predictive analysis, and

a step for generating the predictive error signal by determining a difference between the predictive signal and the error signal, and encoding the predictive coefficient to output a coefficient code.

6. A digital signal encoding method according to claim 1, wherein the step (a) comprises, for a set of m=1 and n=1, a step of compression encoding an (m, n) digital signal having an m-th quantization precision and an n-th sampling frequency to output an (m, n) code, and

wherein the step (b) comprises, for a set of (m, n) within ranges of m=1 and 1≦

n≦

N−

1, up sampling the (m, n) digital signal to an (n+1)-th sampling frequency higher than the n-th sampling frequency, and outputting an (m, n+1) up sampled signal,

compression encoding an (m, n+1) error signal that is an error signal between an (m, n+1) digital signal sampled with the m-th quantization precision and the (n+1)-th sampling frequency and the (m, n+1) up sampled signal, and outputting the compression encoded signal as an (m, n+1) code,

for a set of (m, n) within ranges of 1≦

m≦

M−

1 and 1≦

n≦

N, precision converting the (m, n) digital signal to an (m+1)-th quantization precision higher than an m-th quantization precision, and generating an (m+1, n) precision converted signal, and compression encoding an (m+1, n) error signal that is an error signal between an (m+1, n) digital signal sampled with the (m+1)-th quantization precision and the n-th sampling frequency and the (m+1, n) precision converted signal, and outputting the compression encoded signal as an (m+1, n) code.

7. A digital signal encoding method according to claim 6, wherein the step (b) comprises encoding (m, n+1) sub information representing an adjusting parameter that minimizes power of the (m, n+1) error signal with respect to the (m, n+1) up sampled signal that has been adjusted based on the adjusting parameter, and outputting the encoded information as an (m, n+1) sub code.

8. A digital signal encoding method according to claim 6, wherein the step (b) comprises encoding (m+1, n) sub information representing an adjusting parameter that minimizes power of the (m, n) error signal with respect to the (m+1, n) precision converted signal that has been adjusted based on the adjusting parameter, and outputting the encoded information as an (m+1, n) sub code.

9. A digital signal encoding method according to claim 1, wherein the step (a) comprises, for a set of m=1 and n=1, compression encoding an (m, n) error signal, and generating an (m, n) code,

wherein the step (b) comprises, for a set of (m, n) within ranges of 2≦

m≦

M and 1≦

n≦

N, compression encoding an (m−

1, n) digital signal, and generating an (m−

1, n) code,

for a set of (m, n) within ranges of 2≦

m≦

M and 1≦

n N−

1, generating an (m−

1, n+1) error signal that is an error between an (m−

1, n) digital signal and an (m−

1, n+1) digital signal having an (m−

1)-th quantization precision and an (n+1)-th sampling frequency hither than the n-th sampling frequency, and

generating an (m−

1, n+1) code by compression encoding the (m−

1, n+1) error signal.

10. A digital signal encoding method according to claim 1, wherein the step (a) comprises compression encoding an (m, n) digital signal having an m-th quantization precision and an n-th sampling frequency for a set of m=1 and n=1, and

wherein the step (b) comprises, for a set of (m, n) within ranges of 2≦

m≦

M and 1≦

n≦

N−

1, generating, as the error signals, an (m, n) error signal and an (m−

1, n+1) error signal, the (m, n) error signal being an error signal between the (m, n+1) digital signal having the m-th quantization precision and the (n+1)-th sampling frequency and the (m, n) digital signal and the (m−

1, n+1) error signal being an error signal between the (m, n+1) digital signal and an (m−

1, n+1) digital signal, and

selecting the (m, n) error signal or the (m−

1, n+1) error signal whichever is smaller in distortion, lossless compression encoding the selected error signal to generate an (m, n+1) code, and generating an (m, n+1) sub code indicating which of the error signals is selected.

11. A digital signal encoding method according to claim 1, wherein the step (a) comprises compression encoding an (m, n) digital signal having an m-th quantization precision and an n-th sampling frequency for a set of m=1 and n=1, and

wherein the step (b) comprises, for a set of (m, n) within ranges of 2≦

m≦

M and 1≦

n≦

N−

1, generating, an (m, n+1) sum signal by weighted-summing the (m, n) digital signal and the (m−

1, n+1) digital signal, and generating, as the error signal, a difference between the (m, n+1) sum signal and an (m, n+1) digital signal, and

generating an (m, n+1) code by lossless compression encoding the error signal.

12. A digital signal encoding method according to claim 1, wherein the step (a) comprises compression encoding an (m, n) digital signal having an m-th quantization precision and an n-th sampling frequency for a set of m=1 and n=1 and outputting an (m, n) code, and

wherein the step (b) comprises, for a set of (m, n) within ranges of 1≦

m≦

M and 1≦

n≦

N−

1, up sampling the (m, n) digital signal to an (n+1)-th sampling frequency higher than the n-th sampling frequency and outputting an (m, n+1) up sampled signal,

compression coding an (m, n+1) error signal that is an error signal between the (m, n+1) digital signal having the m-th quantization precision and the (n+1)-th sampling frequency and the (m,n+1) up sampled signal, and outputting the compression encoded signal as an (m, n+1) code, and

for a set of (m, n) within ranges of m=1 and 1≦

n≦

N−

1, precision converting the (m, n) digital signal to an (m+1)-th quantization precision higher than an m-th quantization precision, and generating an (m+1, n) precision converted signal, and

compression encoding an (m+1, n) error signal that is an error signal between an (m+1, n) digital signal having an (m+1)-th quantization precision and an n-th sampling frequency and the (m+1, n) precision converted signal, and outputting the compression encoded signal as an (m+1, n) code.

13. A digital signal encoding method according to claim 12, wherein the step (b) comprises a step for encoding an adjusting parameter that minimizes power of the (m, n+1) error signal with respect to the (m, n+1) up sampled signal that has been adjusted based on the adjusting parameter, and outputting the encoded parameter as an (m, n+1) sub code, or

a step of encoding an adjusting parameter that minimizes the (m+1, n) error signal with respect to the (m+1, n) precision converted signal that is adjusted by the adjusting parameter, and outputting the encoded parameter as an (m+1, n) sub code.

39. A digital signal encoding method according to claim 1, wherein the signal to be encoded is a digital signal of one channel in a first group including a plurality of channels,

and wherein one of a signal lower in attribute rank and a signal modified therefrom is a digital signal of one channel of a second group including channels smaller in number than the first group, or a linear coupling of the digital signals of the plurality of channels.

40. A digital signal encoding method according to claim 39, wherein the digital signals of the second group comprise a monophonic signal having a first quantization precision and a first sampling frequency, and a plurality of channel signals, each having a second quantization precision and a second sampling frequency and higher in attribute rank than the monophonic signal, the digital signals of the first group have the second quantization precision and the second sampling frequency, and the first group comprises the channel signals in number equal to or higher than the second group,

wherein the step (a) comprises a step for encoding the monophonic signal, and

wherein the step (b) comprises:

a step (b-1) for generating a conversion signal that is upgraded from the monophonic signal in attribute rank to the second quantization precision and the second sampling frequency,

a step (b-2) for generating and encoding, as an error signal of the second group, a difference between the conversion signal and the channel signal of the second group, and

a step (b-3) for generating and encoding an error signal between the channel signal of the second group and the channel signal of the first group.

41. A digital signal encoding method according to claim 40, wherein the second group comprises a left-channel signal and a right-channel signal, and wherein the step (b-2) comprises a step for generating and encoding, as one of the error signals of the second group, a difference signal between the left-channel signal and the right-channel signal, and

a step for generating a sum signal of the left-channel signal and the right-channel signal, and generating and encoding, as the other of the error signals, a difference signal between the conversion signal and the sum signal.

51. A digital signal encoding method according to claim 1, wherein the signal to be encoded is a digital signal of one channel of a first group including a plurality of channels, and

wherein a signal lower in attribute rank or a signal modified therefrom is a digital signal of one channel of a second group including channels smaller in number than the first group, or a linear coupling of the digital signals of the plurality of channels.

52. A digital signal encoding method according to claim 51, wherein the digital signals of the second group comprise a monophonic signal having a first quantization precision and a first sampling frequency, and a plurality of channel signals, each having a second quantization precision and a second sampling frequency and higher in attribute rank than the monophonic signal, the digital signals of the first group have the second quantization precision and the second sampling frequency, and the first group comprises the channel signals in number and equal to or higher than the second group,

wherein the step (a) comprises a step for compression encoding the monophonic signal having the first quantization precision and the second sampling frequency, and

wherein the step (b) comprises:

a step for generating a conversion signal that is upgraded from the monophonic signal in attribute rank to the second quantization precision and the second sampling frequency,

a step for generating and encoding, as an error signal of the second group, a difference between the conversion signal and the channel signal of the second group, and

a step for generating a frequency domain signal by inter-channel orthogonal transforming the channel signal of the first group,

a step for generating, as the error signal of the first group, a difference between at least one of the frequency domain signals and the conversion signal, and

a step for compression encoding the error signal of the first group and the frequency domain signal.

59. A computer executable encoding program describing the procedure of the digital encoding method according to claim 1.

14. A digital signal encoding apparatus comprising main code generating means for generating and encoding a signal lower in attribute rank than a signal to be encoded or a signal modified from the signal lower in attribute rank, and

error signal encoding means for lossless encoding an error signal between the signal to be encoded and one of the signal lower in attribute rank and the signal modified from the signal lower in attribute rank.

15. A digital signal encoding apparatus according to claim 14, wherein the main code generating means comprises a down sampler for converting a signal at a first sample frequency to a digital signal at a second sampling frequency lower than the first sampling frequency on a frame-by-frame basis, and

an encoder for compression encoding the digital signal at the second sampling frequency and then outputting the compression encoded signal as a main code, and

wherein the error signal encoding means comprises an up sampler for converting a partial signal corresponding to the main code to a partial signal at the first sampling frequency,

an error calculator for calculating, as the error signal, an error signal between the partial signal at the first sampling frequency and the digital signal at the first sampling frequency, and

a predictive error generator for generating a predictive error signal of the error signal, and

an array converter for lossless encoding an equidistant bit string striding samples of the predictive error signal at each of bit positions that represent the amplitude of each sample of the predictive error signal, and for outputting the lossless encoded bit string as an error code.

16. A digital signal encoding apparatus according to claim 14, wherein the main code generating means comprises an (m, n) encoder for compression encoding an (m, n) digital signal for a set of m=1 and n=1 and outputting an (m, n) code, and

wherein the error signal encoding means comprises an up sampler for up sampling, for a set of (m, n) within ranges of m=1 and 1≦

n≦

N−

1, the (m, n) digital signal to an (n+1)-th sampling frequency higher than the n-th sampling frequency and outputting an (m, n+1) up sampled signal,

an (m, n+1) encoder for compression coding, for a set of (m, n) within ranges of m=1 and 1≦

n≦

N−

1, an (m, n+1) error signal that is an error signal between the (m, n+1) up sampled signal and the (m, n+1) digital signal, and outputting the compression encoded signal as an (m, n+1) code, and

an (m+1, n) precision converter for precision converting, for a set of (m, n) within ranges of 1≦

m≦

M−

1 and 1≦

n≦

N, the (m, n) digital signal to an (m+1)-th quantization precision higher than an m-th quantization precision, and generating an (m+1, n) precision converted signal.

17. A digital signal encoding apparatus according to claim 14, wherein the main code generating means comprises a splitter for splitting the (m, n) digital signal having the m-th quantization precision and the n-th sampling frequency into a digital signal having an (m−

1)-th quantization precision lower than the m-th quantization precision and the n-th sampling frequency and an (m, n) error signal that is an error between the (m−

1, n) digital signal and the (m, n) digital signal,

an (m, n) compressor for generating an (m, n) code by lossless compression encoding the (m, n) error signal for a set of m=1 and n=1, and

an (m−

1, n) compressor for generating, for a set of (m, n) within ranges of 2≦

m≦

M and 1≦

n≦

N−

1, an (m−

1, n) code by compression encoding the (m−

1, n) digital signal, or an input (m−

1, n) digital signal, and

wherein the error signal encoding means comprises an (m−

1, n+1) error generator for generating an (m−

1, n+1) error signal that is an error between the (m−

1, n) digital signal used for generating the (m−

1, n) code and an (m−

1, n+1) digital signal having an (m−

1)-th quantization precision and an (n+1 frequency higher than the n-th sampling frequency, and an (m−

1, n+1) compressor for generating an (m−

1, n+1) code by lossless compression

encoding the (m, n+1) error signal.

18. A digital signal encoding apparatus according to claim 14, wherein the main code generating means comprises (m, n) encoding means for compression encoding an (m, n) digital signal having an m-th quantization precision and an n-th sampling frequency for a set of m=1 and n=1, and

wherein the error signal encoding means comprises an (m−

1, n+1) encoding means for compression encoding, for a set of (m, n) within range of 1≦

m≦

M and 1≦

n≦

N−

1, an (m−

1, n+1) digital signal having an (m−

1)-th quantization precision lower than the m-th quantization precision and an (n+1)-th sampling frequency higher than the n-th sampling frequency,

error signal generating means for generating an (m, n) error signal and an (m−

1, n+1) error signal, the (m, n) error signal being an error signal between the (m, n+1) digital signal having the m-th quantization precision and the (n+1 frequency and the (m, n) digital signal, and the (m−

1, n+1) error signal being an error signal between the (m, n+1) digital signal having the m-th quantization precision and the (n+1 frequency and the (m−

1, n+1) digital signal,

an (m, n+1) compressor for selecting one of the (m, n) error signal and the (m−

1, n+1) error signal whichever is smaller in distortion, and lossless compression encoding the selected error signal to generate an (m, n+1) code, and

an (m, n+1) sub code encoder for generating an (m, n+1) sub code that indicates which error code is selected.

19. A digital signal encoding apparatus according to claim 14, wherein the main code generating means comprises (m, n) encoding means for compression encoding an (m, n) digital signal having an m-th quantization precision and an n-th sampling frequency for a set of m=1 and n=1, and

wherein the error signal encoding means comprises an (m, n+1) mixer for generating, for a set of (m, n) within ranges of 2≦

m≦

M and 1≦

n≦

N−

1, an (m, n+1) sum signal by weighted-summing the (m, n) digital signal and an (m−

1, n+1) digital signal, and generating, as the error signal, a difference between the (m, n+1) sum signal and an (m, n+1) digital signal, and

an (m, n+1) compressor for generating an (m, n+1) code by lossless compression encoding the error signal.

20. A digital signal encoding apparatus according to claim 14, wherein the main code generating means comprises (m, n) encoding means for compression encoding an (m, n) digital signal having an m-th quantization precision and an n-th sampling frequency for a set of m=1 and n=1, and outputting an (m, n) code,

wherein the error signal encoding means comprises an (m, n+1) up sampler for generating, for a set of (m, n) within ranges of 1≦

m≦

M and 1≦

n≦

N−

1, an (m, n+1) up sampled signal by up sampling the (m, n) digital signal to an (n+1)-th sampling frequency higher than the n-th sampling frequency,

an (m, n+1) compressor for compression coding an (m, n+1) error signal that is an error signal between the (m, n+1) digital signal having the m-th quantization precision and the (n+1)-th sampling frequency and the (m, n+1) up sampled signal, and outputting the compression encoded signal as an (m, n+1) code, and

an (m+1, n) precision converter for precision converting, for a set of (m, n) within ranges of 1≦

m≦

M−

1 and 1≦

n≦

N, the (m, n) digital signal to an (m+1)-th quantization precision higher than an m-th quantization precision, and generating an (m+1, n) precision converted signal, and

an (m+1, n) compressor for compression encoding an (m+1, n) error signal that is an error signal between the (m+1, n) digital signal having the (m+1)-th quantization precision and the n-th sampling frequency and the (m+1, n) precision converted signal, and outputting the compression encoded signal as an (m+1, n) code.

42. A digital signal encoding apparatus according to claim 14, wherein the signal to be encoded is a digital signal of one channel in a first group including a plurality of channels,

and wherein one of a signal lower in attribute rank or a signal modified therefrom is a digital signal of one channel of a second group including channels smaller in number than the first group, or a linear coupling of the digital signals of the plurality of channels.

43. A digital signal encoding apparatus according to claim 42, wherein the digital signals of the second group comprise a monophonic signal having a first quantization precision and a first sampling frequency, and a plurality of channel signals, each having a second quantization precision and a second sampling frequency and higher in attribute rank than the monophonic signal, the digital signals of the first group have the second quantization precision and the second sampling frequency, and the first group comprises the channel signals in number equal to or higher than the second group,

wherein the main code generating means is means for compression encoding the monophonic signal, and

wherein the error signal generating means comprises:

upgrading means for generating a conversion signal that is upgraded from the monophonic signal in attribute rank to the second quantization precision and the second sampling frequency,

a plurality of second group subtractors for determining an error between the conversion signal and the channel signal of the second group, and outputting a plurality of first error signals,

a compression encoder for lossless encoding the error signal of the second group,

a plurality of first group subtractors for generating a plurality of first group error signals between the channel signal of the second group and the channel signal of the first group, and

a plurality of first group compression encoders for lossless encoding the plurality of first group error signals.

44. A digital signal encoding apparatus according to claim 43, wherein the channel signals of the second group comprises a left-channel signal and a right-channel signal, and the channel signals of the first group comprises at least two multi-channel signals, and

wherein the second group subtractors for generating the error signal of the second group, comprises:

a subtractor for generating a difference signal between the left-channel signal and the right-channel signal as one of the error signals of the second group,

an adder for generating a sum signal of the left-channel signal and the right-channel signal, and a subtractor for generating a difference between the sum signal and the conversion signal as the error signal of the second group.

55. A digital signal encoding apparatus according to claim 14, wherein the signal to be encoded is a digital signal of one channel of a first group including a plurality of channels, and

wherein a signal lower in attribute rank or a signal modified therefrom is a digital signal of one channel of a second group including channels smaller in number than the first group, or a linear coupling of the digital signals of the plurality of channels.

56. A digital signal encoding apparatus according to claim 55, wherein the digital signals of the second group comprise a monophonic signal having a first quantization precision and a first sampling frequency, and a plurality of channel signals, each having a second quantization precision and a second sampling frequency and higher in attribute rank than the monophonic signal, the digital signals of the first group have the second quantization precision and the second sampling frequency, and the first group comprises the channel signals in number equal to or higher than the second group,

wherein the main code generating means is means for compression encoding the monophonic signal having the first quantization precision and the first sampling frequency, and

wherein the error signal generating means comprises:

an upgrader for generating a conversion signal that is upgraded from the monophonic signal in attribute rank to the second quantization precision and the second sampling frequency,

a second group subtractor for generating, as an error signal of the second group, a difference between the component of the channel signal of the second group and the conversion signal,

a first compression encoder for outputting the error signal by compression encoding the error signal of the second group,

an inter-channel orthogonal transformer for generating a frequency domain signal by inter-channel orthogonal transforming the channel signal of the first group,

a first group subtractor for generating, as the error signal of the second group, a difference between at least one of the frequency domain signals and the conversion signal, and

a first group subtractor for generating, the error signal of the first group, an error signal between the frequency domain signal and the error signal of the second group.

21. A digital signal decoding method comprising:

a step (a) of generating an error signal by decoding an input code, and

a step (b) of generating a decoded signal by synthesizing the error signal, and a decoded signal or a signal modified from the decoded signal, the decoded signal being decoded from a main code and lower in attribute rank than the error signal.

22. A digital signal decoding method according to claim 21, wherein the step (a) comprises decoding an input error code as an input code, and reproducing a predictive error signal at a first sampling frequency formed of a bit string at the same bit position straddling samples at each of bit positions, and

wherein the step (b) comprises reproducing the error signal by synthesizing the predictive error signal, converting the decoded signal decoded from the main code to a signal having the first sampling frequency higher than the sampling frequency thereof, and summing the converted decoded signal and the error signal to a reproduced digital signal.

23. A digital signal decoding method according to claim 21, wherein the step (b) comprises summing the error signal and the decoded signal with the frequency axis thereof inverted.

24. A digital signal decoding method according to claim 22, wherein the step (b) comprises converting the predictive error signal to a predictive error signal at a second sampling frequency lower than the first sampling frequency,

converting a predictive signal of the predictive error signal at the second sampling frequency to a predictive signal at the first sampling frequency, and

generating the error signal by summing the predictive signal at the first sampling frequency and the predictive error signal at the first sampling frequency.

25. A digital signal decoding method according to claim 22, wherein the step (b) comprises generating a predictive signal by linear predicting the predictive error signal based on a linear predictive coefficient decoded from an input coefficient code, and

acquiring the error signal by summing the predictive signal and the predictive error signal.

26. A digital signal decoding method according to claim 21, wherein the step (a) comprises at least one of a first procedure and a second procedure, wherein the first procedure comprises, for a set of (m, n) within ranges of m=1 and 1≦

n≦

N−

1, up sampling an (m, n) digital signal, as a lower ranking attribute signal, having an m-th quantization precision and an n-th sampling frequency to an (n+1)-th sampling frequency higher than the n-th sampling frequency and generating an (m, n+1) up sampled signal, and

for a set of (m, n) within ranges of 1≦

m≦

M and 1≦

n≦

N−

1, generating an (m, n+1) error signal having the m-th quantization precision and the (n+1)-th sampling frequency by decoding an (m, n+1) code as an input signal, and generating an (m, n+1) reproduction signal by adding the (m, n+1) error signal and the (m, n+1) up sampled signal, and

wherein the second procedure comprises generating, for a set of (m, n) within ranges of 1≦

m≦

M−

1 and 1≦

n≦

N, an (m+1, n) precision conversion signal by converting the (m, n) digital signal, as a signal having a lower ranking attribute, to an (m+1)-th quantization precision higher than the m-th quantization precision, generating an (m+1, n) error signal having an (m+1)-th quantization precision and the n-th sampling frequency by decoding an (m+1, n) code as an input code, and generating an (m+1, n) digital signal by summing the (m+1, n) error signal and the (m+1, n) precision conversion signal, and

wherein the step (b) comprises generating the (m, n) digital signal by decoding an (m, n) code for a set of m=1 and n=1.

27. A digital signal decoding method according to claim 26, wherein, for a set of (m, n) within ranges of 1≦

m≦

M and 1≦

n≦

N−

1, the step (a) comprises a step for generating an adjusting parameter of the (m, n+1) up sampled signal by decoding (m, n+1) sub information, and

generating an (m, n+1) reproduction signal by summing the (m, n+1) error signal and the (m, n+1) up sampled signal that is adjusted using the adjusting parameter.

28. A digital signal decoding method according to claim 26, wherein the step (a) comprises generating, for a set of (m, n) within ranges of 1≦

m≦

M−

1 and 1≦

n≦

N, an adjusting parameter of the (m+1, n) precision conversion signal by decoding an (m+1, n) sub code, and

generating an (m+1, n) digital signal by summing the (m+1, n) precision conversion signal and an (m+1, n) precision conversion signal that is adjusted using the adjusting parameter.

29. A digital signal decoding method according to claim 21, wherein the step (a) comprises generating, for a set of (m, n) within ranges of 1≦

m≦

M and 1≦

n≦

N−

1, an (m, n+1) error signal having the m-th quantization precision and the (n+1)-th sampling frequency by lossless extension decoding an (m, n+1) code as a signal having a lower ranking attribute, and

reproducing an (m, n+1) digital signal by summing, for a set of (m, n) within ranges of 2≦

m≦

M and 1≦

n≦

N−

1, one of an (m, n) digital signal as a lower ranking attribute signal and an (m−

1, n) digital signal, designated by selection signal that is decoded from an (m, n+1) sub code, and the (m, n+1) error signal, and reproducing an (m, n+1) digital signal,

wherein the step (b) comprises generating the (m, n) digital signal by decoding an (m, n) code for a set of (m, n) with m=1 and n=1.

30. A digital signal decoding method according to claim 21, wherein the step (a) comprises generating, for a set of (m, n) within ranges of 1≦

m≦

M and 1≦

n≦

N−

1 except m=1 and n=1, an (m, n+1) error signal having an m-th quantization precision and an (n+1)-th sampling frequency by lossless expansion decoding an (m, n+1) code,

generating, for a set of (m, n) within ranges of 2≦

m≦

M and 1≦

n≦

N−

1, an (m, n+1) sum signal having an m-th quantization precision and an (n+1)-th sampling frequency by weighted summing an (m, n) digital signal, as a signal lower in attribute rank, and an (m−

1, n+1) digital signal with information decoded from an (m, n+1) sub code, and

reproducing an (m, n+1) digital signal by summing the (m, n+1) sum signal and the (m, n+1) error signal, and

wherein the step (b) comprises generating the (m, n) digital signal by decoding an (m, n) code for a set of m=1 and n=1.

31. A digital signal decoding method according to claim 21, wherein the step (a) generates a decoded signal by performing one of a first procedure and a second procedure,

wherein the first procedure comprises generating, for a set of (m, n) within ranges of 1≦

m≦

M and 1≦

n≦

N−

1, an (m, n+1) up sampled signal by up sampling an (m, n) digital signal, as a signal lower in attribute rank, to an (n+1)-th sampling frequency higher than the n-th sampling frequency, and

generating an (m, n+1) error signal having an m-th quantization precision and an (n+1)-th sampling frequency by decoding an (m, n+1) code as the input code,

generating, for a set of (m, n) within ranges of 1≦

m≦

M−

1 and 1≦

n≦

N, an (m+1, n) precision conversion signal by precision converting the (m, n) digital signal to a (m+1)-th quantization precision higher than the m-th quantization precision, and

generating, for a set of (m, n) within ranges of 1≦

m≦

M and 1≦

n≦

N−

1, an (m, n+1) digital signal by summing the (m, n+1) error signal and the (m, n+1) up sampled signal as a modified signal lower in attribute rank,

wherein the second procedure comprises generating, for a set of (m, n) within ranges of 1≦

m≦

M−

1 and 1≦

n≦

N, an (m+1, n) digital signal by summing the (m+1, n) error signal and the (m+1, n) precision conversion signal as a modified signal lower in attribute rank, and

wherein the step (b) comprises generating the (m, n) digital signal by decoding an (m, n) code for a set of m=1 and n=1.

32. A digital signal decoding method according to claim 31, wherein the first procedure comprises adjusting the (m, n+1) up sampled signal that is summed based on an adjusting parameter decoded from an (m, n+1) sub code, and the second procedure comprises adjusting the (m+1, n) precision conversion signal by decoding an (m+1, n) sub code based on the generated adjusting parameter.

45. A digital signal decoding method according to claim 21, wherein the error signal is a digital error signal of one channel of a first group including a plurality of channels, and

wherein the decoded signal lower in attribute rank or the decoded signal is a digital signal of one channel of a second group including channels smaller in number than the first group, or a linear coupling of the digital signals of the plurality of channels.

46. A digital signal decoding method according to claim 45, wherein the digital signals of the second group comprise a monophonic signal having a first quantization precision and a first sampling frequency, and a plurality of channel signals, each having a second quantization precision and a second sampling frequency and higher in attribute rank than the monophonic signal, the digital error signals of the first group have the second quantization precision and the second sampling frequency, and the first group comprises the channel signals in number equal to or higher than the second group,

wherein the step (a) comprises a step for decoding the error code of the channel signal of the second group and the error code of the channel signal of the first group, and generating a second group error signal and a first group error signal, and

wherein the step (b) comprises:

a step (b-1) for reproducing the monophonic signal by decoding a main code,

a step (b-2) for generating a conversion signal that is upgraded from the monophonic signal in attribute rank to the second quantization precision and the second sampling frequency,

a step (b-3) for reproducing the channel signal of the second group by summing the conversion signal and the first error signal, and

a step (b-4) for reproducing the channel signal of the first group by summing the reproduced channel signal of the second group and the error signal of the first group.

47. A digital signal decoding method according to claim 46, wherein the channel signals of the second group comprises a left-channel signal and a right-channel signal, and the step (b-3) comprises a step for generating a sum signal and a difference signal of the left-channel signal and the right-channel signal by decoding the error signal of the second group, and a step for reproducing the left-channel signal and the right-channel signal by summing the difference signal and the sum signal and subtracting the difference signal from the sum signal.

53. A digital signal decoding method according to claim 21, wherein the error signal is a digital error signal of one channel of a first group including a plurality of channels, and

wherein the decoded signal lower in attribute rank or the decoded signal is a digital signal of one channel of a second group including channels smaller in number than the first group, or a linear coupling of the digital signals of the plurality of channels.

54. A digital signal decoding method according to claim 53, wherein the digital signals of the second group comprise a monophonic signal having a first quantization precision and a first sampling frequency, and a plurality of channel signals, each having a second quantization precision and a second sampling frequency and higher in attribute rank than the monophonic signal, the digital error signals of the first group have the second quantization precision and the second sampling frequency, and the first group comprises the channel signals in number and equal to or higher than the second group,

wherein the step (b) comprises reproducing the monophonic signal by decoding a main code, and

wherein the step (a) comprises generating a conversion signal that is upgraded from the monophonic signal in attribute rank to the second quantization precision and the second sampling frequency, generating the error signal of the second group by decoding the error signal of the second group, reproducing the channel signal of the second group by summing one of the error signals of the first group and the conversion signal, and

reproducing the time domain signal as the channel signal of the second group by inverse orthogonal transforming the resulting sum and the remaining frequency domain signals.

60. A computer executable decoding program describing the procedure of the digital decoding method according to claim 21.

33. A digital signal decoding apparatus comprising:

error signal generating means for generating an error signal by decoding an input code, and

signal synthesizing means for generating a decoded signal by synthesizing the error signal and a decoded signal lower in attribute rank than the error signal or a signal modified from the decoded signal lower in attribute rank.

34. A digital signal decoding apparatus according to claim 33, wherein the error signal generating means comprises:

an array converter which produces a predictive error signal at a first sampling frequency by acquiring a bit string by decoding an input error code, and by extracting, from one frame of the acquired bit string, bits at the same bit position in the direction of bit array, and

a prediction synthesizer which reproduces an error signal by prediction synthesizing the predictive error signal, and

wherein the signal synthesizing means comprises;

a decoder which acquires a decoded signal by decoding an input main code,

an up sampler which converts the decoded signal to a decoded signal at the first sampling frequency higher than the sampling frequency thereof, and

an adder which provides a reproduced digital signal by summing the converted decoded signal and the error signal.

35. A digital signal decoding apparatus according to claim 33, wherein the signal synthesizing means comprises one of (m, n+1) reproducing means and (m+1, n) reproducing means,

wherein the (m, n+1) reproducing means comprises:

an up sampler for generating, for a set of (m, n) within ranges of m=1 and 1≦

n≦

N−

1, an (m, n+1) up sampled signal by up sampling an (m, n) digital signal, as a signal lower in attribute rank, having an m-th quantization precision and an n-th sampling frequency to an (n+1)-th sampling frequency higher than the n-th sampling frequency,

an (m, n+1) decoder for generating, for a set of (m, n) within ranges of 1≦

m≦

M and 1≦

n≦

N−

1, an (m, n+1) error signal having the m-th quantization precision and the (n+1)-th sampling frequency by decoding an (m, n+1) code, and

an adder for generating an (m, n+1) reproduction signal by summing the (m, n+1) error signal and the (m, n+1) up sampled signal,

wherein the (m+1, n) reproducing means comprises;

a precision converter for generating, for a set of (m, n) within ranges of 1≦

m≦

M−

1 and 1≦

n≦

N, an (m+1, n) precision conversion signal by converting the (m, n) digital signal, lower in attribute rank, to an (m+1)-th quantization precision higher than the m-th quantization precision,

an (m+1, n) decoder for generating an (m+1, n) error signal having an (m+1)-th quantization precision and the n-th sampling frequency by decoding an (m+1, n) code, and

an adder for generating an (m+1, n) digital signal by summing the (m+1, n) error signal and the (m+1, n) precision conversion signal, and

wherein the signal synthesizing means comprises an (m, n) decoder for generating the (m, n) digital signal by decoding an (m, n) code for a set of m=1 and n=1.

36. A digital signal decoding apparatus according to claim 33, wherein the error signal generating means comprises:

reproducing means for decoding, for a set of (m, n) within ranges of 2≦

m≦

M and 1≦

n≦

N−

1 except m=1 and n=1, decoding a plurality of codes and reproducing an (m, n) digital signal having an m-th quantization precision and an n-th sampling frequency, and an (m−

1, n+1) digital signal having an (m-i)-th quantization precision lower than the m-th quantization precision and an (n+1)-th sampling frequency higher than the n-th sampling frequency,

an (m, n+1) expander for generating an (m, n+1) error signal having an m-th quantization precision and an (n+1)-th sampling frequency by lossless expansion decoding an (m, n+1) code, and

an (m, n+1) adder for reproducing an (m, n+1) digital signal by summing, for a set of (m, n) within ranges of 2≦

m≦

M and 1≦

n≦

N−

1, one of an (m, n) digital signal as a signal lower in attribute rank and an (m−

1, n) digital signal, designated by selection signal that is decoded from an (m, n+1) sub code, and the (m, n+1) error signal, and

wherein the signal synthesizing means comprises an (m, n) decoder for generating the (m, n) digital signal by decoding an (m, n) code for a set of (m, n) with m=1 and n=1.

37. A digital signal decoding apparatus according to claim 33, wherein the error signal generating means comprises:

an (m, n+1) expander for generating, for a set of (m, n) within ranges of 1≦

m≦

M and 1≦

n≦

N−

1 except m=1 and n=1, an (m, n+1) error signal having an m-th quantization precision and an (n+1)-th sampling frequency by lossless expansion decoding an (m, n+1) code,

an (m, n+1) sub decoder for determining sub information that designates a summing method by decoding an (m, n+1) sub code,

an (m, n+1) mixer for generating, for a set of (m, n) within ranges of 2≦

m≦

M and 1≦

n≦

N−

1, an (m, n+1) sum signal, as a modified signal lower in attribute rank, by weighted summing an (m, n) digital signal, as a signal lower in attribute rank, and an (m−

1, n+1) digital signal based on the sub information, and

an (m, n+1) adder for reproducing an (m, n+1) digital signal having an m-th quantization precision and an (n+1)-th sampling frequency by summing the (m, n+1) sum signal and the (m, n+1) error signal.

38. A digital signal decoding apparatus according to claim 33, wherein the error signal generating and synthesizing means comprises at least one of (m, n+1) reproducing means, (m+1, n) reproducing means, and the (m+1, n) reproducing means and (m+1, n+1) reproducing means,

wherein the (m, n+1) reproducing means comprises:

an (m, n+1) up sampler for generating, for a set of (m, n) within ranges of 1≦

m≦

M and 1≦

n≦

N−

1, an (m, n+1) up sampled signal as a modified signal lower in attribute rank by up sampling an (m, n) digital signal, as a signal lower in attribute rank, to an (n+1)-th sampling frequency higher than the n-th sampling frequency,

an (m, n+1) expander for generating an (m, n+1) error signal having an m-th quantization precision and an (n+1)-th sampling frequency by decoding an (m, n+1) code as the input code, and

an adder for generating, for a set of (m, n) within ranges of 1≦

m≦

M−

1 and 1≦

n≦

N, an (m, n+1) digital signal by summing the (m, n+1) error signal and the (m, n+1) up sampled signal as a modified signal lower in attribute rank,

wherein the (m+1, n) reproducing means comprises;

an (m+1, n) precision converter for generating, for a set of (m, n) within ranges of 1≦

m≦

M−

1 and n=1, an (m+1, n) precision conversion signal by precision converting the (m, n) digital signal to an (m+1)-th quantization precision higher than the m-th quantization precision,

an (m+1, n) expander for generating an (m+1, n) error signal having an (m+1)-th quantization precision and an N-th sampling frequency by decoding an (m+1, n) code, and

an adder for generating an (m+1, n) digital signal by summing the (m+1, n) error signal and the (m+1, n) precision conversion signal, and

wherein the signal synthesizing means comprises an (m, n) expander for generating the (m, n) digital signal by decoding an (m, n) code for a set of m=1 and n=1.

48. A digital signal decoding apparatus according to claim 33, wherein the error signal is a digital error signal of one channel of a first group including a plurality of channels, and

wherein the decoded signal lower in attribute rank or the decoded signal is a digital signal of one channel of a second group including channels smaller in number than the first group, or a linear coupling of the digital signals of the plurality of channels.

49. A digital signal decoding apparatus according to claim 48, wherein the digital signals of the second group comprise a monophonic signal having a first quantization precision and a first sampling frequency, and a plurality of channel signals, each having a second quantization precision and a second sampling frequency and higher in attribute rank than the monophonic signal, the error signals of the first group have the second quantization precision and the second sampling frequency, and the first group comprises the channel signals in number equal to or higher than the first group,

wherein the error signal generating means comprises a second group decoder for acquiring the error signal of the second group by decoding the error signal of the second group, and a first group decoder for acquiring the error signal of the first group by decoding the error of the first group, and

wherein the signal synthesizing means comprises a monophonic signal decoder for reproducing the monophonic signal by decoding a main code, an upgrader for generating a conversion signal that is upgraded from the monophonic signal in attribute rank to the second quantization precision and the second sampling frequency at the same attribute rank as the channel signal of the second group, a second group adder for reproducing the channel signal of the second group by summing the conversion signal and the error signal of the second group, and a first group adder for reproducing the channel signal of the first group by summing the reproduced channel signal of the second group and the error signal of the first group.

50. A digital signal decoding apparatus according to claim 49, wherein the channel signals of the first group include a left-channel signal and a right-channel signal, one of the decoded error signals of the second group is a difference signal, and the second group adders comprise a first adder for generating a sum signal of the left-channel signal and the right-channel signal by summing the conversion signal and one of the decoded error signals of the second group, and a second adder and a subtractor for reproducing the left-channel signal and the right-channel signal by summing the difference signal and the sum signal and subtracting the difference signal from the sum signal, respectively.

57. A digital signal decoding apparatus according to claim 33, wherein the error signal is a digital error signal of one channel of a first group including a plurality of channels, and

wherein the decoded signal lower in attribute rank or the decoded signal is a digital signal of one channel of a second group including channels smaller in number than the first group, or a linear coupling of the digital signals of the plurality of channels.

58. A digital signal decoding apparatus according to claim 57, wherein the signal synthesizing means comprises:

a main code decoder for reproducing a monophonic signal by decoding a main code,

a second group decoder for generating a second group error signal by decoding an error code of the second group,

a first group decoder for generating a frequency domain signal and a first group error signal by decoding a first group code containing at least one error code,

an upgrader for generating a conversion signal that is upgraded from the monophonic signal to a second quantization precision and a second sampling frequency,

a second group adder for reproducing the channel signal of the second group by summing the conversion signal and the error signal of the second group, and

an inverse orthogonal transformer for reproducing the channel signal of the first group by summing the conversion signal and the error signal of the first group, and by inverse orthogonal transforming the resulting sum and the frequency domain into a time domain signal.