Method, apparatus, and program for encoding digital signal, and method, apparatus, and program for decoding digital signal

• US 8,311,815 B2
• Filed: 07/14/2009
• Issued: 11/13/2012
• Est. Priority Date: 03/08/2002
• Status: Active Grant

• Current Assignee: Nippon Telegraph and Telephone Corporation
• Original Assignee: Nippon Telegraph and Telephone Corporation
• Inventors: Moriya, Takehiro, Jin, Akio, Ikeda, Kazunaga, Mori, Takeshi
• Primary Examiner(s): Vo, Huyen X.
• Application Number:
  US12/502,797
• Publication Number:
  US 20090279598A1
• Time in Patent Office: 1,218 Days
• Field of Search: 704500-504, 704/219, 704/220, 704/221, 704/222, 704/223, 704/229, 704/200, 704/262, 704/200.1, 704/226, 704/230
• US Class Current: 704/226
• 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 decoding method for decoding codes of digital signals, comprising:

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

a step (b) of generating a decoded main signal by decoding a main code, the decoded main signal being lower in both sampling frequency and quantization precision than the error signal,

a step (c) of generating a decoded signal by combining the error signal and the decoded main signal or a signal modified from the decoded main signal.

2. A digital signal decoding method comprising:

a step (a) of decoding an input error code to produce a sequence of input samples in the form of a first array of bits, and converting the first array of bits to produce a second array of bits which represents a sequence of samples of an error signal at a first sampling frequency, in which the first array of bits includes a plurality of equidistant bit strings that sequentially correspond to a sequence of bits which is a concatenation in the time direction of polarity bits of all the samples contained in the sequence of samples of the error signal and respective sequences of bits which are concatenations in the time direction of bits of all the samples at respective bit positions within amplitudes contained in the sequence of samples of the error signal, and in which the second array of bits includes a plurality of amplitude bit strings each of which is a concatenation of amplitude bits and a respective one of the polarity bits contained in the sequence of samples of the error signal,

a step (b) of generating a decoded main signal by decoding a main code, the decoded main signal being lower in both sampling frequency and quantization precision than the error signal,

a step (c) of generating a decoded signal by combining the error signal and the decoded main signal or a signal modified from the decoded main signal.

3. 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 combining the error signal and a decoded main signal or a signal modified from the decoded main signal, the decoded main signal being decoded from a main code and lower in attribute rank than the error signal,

wherein the step (b) comprises summing the error signal and the decoded signal with the frequency axis thereof inverted.

4. A digital signal decoding method comprising:

a step (a) of decoding an input error code to produce a sequence of input samples, and reproducing a sequence of samples of a predictive error signal at a first sampling frequency by converting an array of bits of the sequence of input samples so that each sample of the predictive error signal is formed of a bit string of those straddling the sequence of the input samples at respective one of bit positions thereof; and

a step (b) of reproducing an error signal by synthesizing the predictive error signal, converting a decoded main signal decoded from a main code to a converted decoded main signal having the first sampling frequency higher than the sampling frequency of the decoded main signal, and summing the converted decoded main signal and the error signal to generate a reproduced digital signal;

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.

5. A digital signal decoding method comprising:

a step (a) of decoding an input error code to produce a sequence of input samples in the form of a first array of bits, and converting the first array of bits to produce a second array of bits which represents a sequence of samples of an error signal at a first sampling frequency, in which the first array of bits includes a plurality of equidistant bit strings that sequentially correspond to a sequence of bits which is a concatenation in the time direction of polarity bits of all the samples contained in the sequence of samples of the error signal and respective sequences of bits which are concatenations in the time direction of bits of all the samples at respective bit positions within amplitudes contained in the sequence of samples of the error signal, and in which the second array of bits includes a plurality of amplitude bit strings each of which is a concatenation of amplitude bits and a respective one of the polarity bits contained in the sequence of samples of the error signal;

a step (b) of generating a decoded main signal by decoding a main code, and

a step (c) of reproducing an error signal by synthesizing the predictive error signal, the decoded main signal being lower in both sampling frequency and quantization precision than the error signal;

a step (d) of converting the decoded main signal to a converted decoded main signal having the first sampling frequency higher than the sampling frequency of the decoded main signal, and summing the converted decoded main signal and the error signal to generate a reproduced digital signal;

wherein the step (c) 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.

6. 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 combining the error signal and a decoded main signal or a signal modified from the decoded main signal, the decoded main signal being decoded from a main code and lower in attribute rank than the error signal;

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.

7. A digital signal decoding method according to claim 6, 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.

8. A digital signal decoding method according to claim 6, 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.

9. 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 combining the error signal and a decoded main signal or a signal modified from the decoded main signal, the decoded main signal being decoded from a main code and lower in attribute rank than the error signal;

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.

10. 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 combining the error signal and a decoded main signal or a signal modified from the decoded main signal, the decoded main signal being decoded from a main code and lower in attribute rank than the error signal;

wherein the step (a) comprises generating, for a set of (m, n) within ranges of and 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.

11. 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 combining the error signal and a decoded main signal or a signal modified from the decoded main signal, the decoded main signal being decoded from a main code and lower in attribute rank than the error signal;

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.

12. A digital signal decoding method according to claim 11, 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.

13. A digital signal decoding apparatus for decoding codes of digital signals, comprising:

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

main signal generating means for generating a decoded main signal by decoding a main code, the decoded main signal being lower in both sampling frequency and quantization precision than the error signal, and

signal combining means for generating a decoded signal by combining the error signal and the decoded main signal or a signal modified from the decoded main signal.

14. A digital signal decoding apparatus comprising:

an array converter which is configured to produce an error signal at a first sampling frequency by decoding an input error code to produce a sequence of input samples in the form of a first array of bits and converting the first array of bits to produce a second array of bits which represents a sequence of samples of an error signal at a first sampling frequency, in which the first array of bits includes a plurality of equidistant bit strings that sequentially correspond to a sequence of bits which is a concatenation in the time direction of polarity bits of all the samples contained in the sequence of samples of the error signal and respective sequences of bits which are concatenations in the time direction of bits of all the samples at respective bit positions within amplitudes contained in the sequence of samples of the error signal, and in which the second array of bits includes a plurality of amplitude bit strings each of which is a concatenation of amplitude bits and a respective one of the polarity bits contained in the sequence of samples of the error signal,

main signal generating means for generating a decoded main signal by decoding a main code, the decoded main signal being lower in both sampling frequency and quantization precision than the error signal, and

a signal combining means which is configured to combine the error signal and the decoded main signal or a signal modified from the decoded main signal to generate a decoded signal.

15. A digital signal decoding apparatus comprising:

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

signal combining means for generating a decoded signal by combining the error signal and a decoded main signal or a signal modified from the decoded main signal, the decoded main signal being decoded from a main code and lower in attribute rank than the error signal;

wherein the signal combining 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 combining 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.

16. A digital signal decoding apparatus comprising:

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

signal combining means for generating a decoded signal by combining the error signal and a decoded main signal or a signal modified from the decoded main signal, the decoded main signal being decoded from a main code and lower in attribute rank than the error signal;

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, 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−

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,

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 combining 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.

17. A digital signal decoding apparatus comprising:

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

signal combining means for generating a decoded signal by combining the error signal and a decoded main signal or a signal modified from the decoded main signal, the decoded main signal being decoded from a main code and lower in attribute rank than the error signal;

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.

18. A digital signal decoding apparatus comprising:

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

signal combining means for generating a decoded signal by combining the error signal and a decoded main signal or a signal modified from the decoded main signal, the decoded main signal being decoded from a main code and lower in attribute rank than the error signal;

wherein the error signal generating and signal combining means comprises at least one of (m, n+b 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 combining 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.

19. 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 combining the error signal and a decoded main signal or a signal modified from the decoded main signal, the decoded main signal being decoded from a main code and lower in attribute rank than the error signal;

wherein the error signal is a digital error signal of one channel of a first group including a plurality of channels,

wherein the decoded main 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,

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 the 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 group 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.

20. A digital signal decoding method according to claim 19, 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.

21. A digital signal decoding apparatus comprising:

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

signal combining means for generating a decoded signal by combining the error signal and a decoded main signal or a signal modified from the decoded main signal, the decoded main signal being decoded from a main code and lower in attribute rank than the error signal;

wherein the error signal is a digital error signal of one channel of a first group including a plurality of channels,

wherein the decoded main 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,

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 signal of the first group, and

wherein the signal combining means comprises a monophonic signal decoder for reproducing the monophonic signal by decoding the 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.

22. A digital signal decoding apparatus according to claim 21, 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.

23. 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 combining the error signal and a decoded main signal or a signal modified from the decoded main signal, the decoded main signal being decoded from a main code and lower in attribute rank than the error signal;

wherein the error signal is a digital error signal of one channel of a first group including a plurality of channels,

wherein the decoded main 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,

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.

24. A digital signal decoding apparatus comprising:

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

signal combining means for generating a decoded signal by combining the error signal and a decoded main signal or a signal modified from the decoded main signal, the decoded main signal being decoded from a main code and lower in attribute rank than the error signal;

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 main 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, and

wherein the signal combining 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.

25. A non-transitory computer readable medium having a computer readable program stored thereon, the program configured to perform a digital decoding method when executed on the computer, the method comprising:

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

a step (b) of generating a decoded main signal by decoding a main code, the decoded main signal being lower in both sampling frequency and quantization precision than the error signal, and

a step (c) of generating a decoded signal by combining the error signal and the decoded main signal or a signal modified from the decoded main signal.

26. A non-transitory computer readable medium having a computer readable program stored thereon, the program configured to perform a digital decoding method when executed on the computer, the method comprising:

a step (a) of decoding an input error code to produce a sequence of input samples in the form of a first array of bits, and converting the first array of bits to produce a second array of bits which represents a sequence of samples of an error signal at a first sampling frequency, in which the first array of bits includes a plurality of equidistant bit strings that sequentially correspond to a sequence of bits which is a concatenation in the time direction of polarity bits of all the samples contained in the sequence of samples of the error signal and respective sequences of bits which are concatenations in the time direction of bits of all the samples at respective bit positions within amplitudes contained in the sequence of samples of the error signal, and in which the second array of bits includes a plurality of amplitude bit strings each of which is a concatenation of amplitude bits and a respective one of the polarity bits contained in the sequence of samples of the error signal,

a step (b) of generating a decoded main signal by decoding a main code, the decoded main signal being lower in both sampling frequency and quantization precision than the error signal, and

a step (c) of generating a decoded signal by combining the error signal and the decoded main signal or a signal modified from the decoded main signal.

27. A non-transitory computer readable medium having a computer readable program stored thereon, the program configured to perform a digital decoding method when executed on the computer, the 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 combining the error signal and a decoded main signal or a signal modified from the decoded main signal, the decoded main signal being decoded from a main code and lower in attribute rank than the error signal;

wherein the error signal is a digital error signal of one channel of a first group including a plurality of channels,

wherein the decoded main 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,

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 the 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 group 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

28. A non-transitory computer readable medium having a computer readable program stored thereon, the program configured to perform a digital decoding method when executed on the computer, the 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 combining the error signal and a decoded main signal or a signal modified from the decoded main signal, the decoded main signal being decoded from a main code and lower in attribute rank than the error signal;

wherein the error signal is a digital error signal of one channel of a first group including a plurality of channels,

wherein the decoded main 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,

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.