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

• US 7,599,835 B2
• Filed: 03/10/2003
• Issued: 10/06/2009
• Est. Priority Date: 03/08/2002
• Status: Active Grant

• Current Assignee: Nippon Telegraph and Telephone Corporation
• Original Assignee: Nippon Telegraph and Telephone Corporation
• Inventors: Ikeda, Kazunaga, Jin, Akio, Mori, Takeshi, Moriya, Takehiro
• Primary Examiner(s): Vo; Huyen X.
• Application Number:
  US10/505,485
• Publication Number:
  US 20050091051A1
• Time in Patent Office: 2,402 Days
• Field of Search: 704500-504, 704/219, 704/220, 704/222, 704/221, 704/230, 704/227, 704/226, 704/229
• 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 encoding method comprising:

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

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 from the signal lower in attribute rank to produce an error code, and

outputting the main code and the error code;

wherein the step (b) comprises lossless encoding a predictive error signal of the error signal with the frequency axis thereof inverted to produce the error code.

2. A digital signal encoding method comprising:

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

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 from the signal lower in attribute rank to produce an error code, and

outputting the main code and the error code;

wherein letting m and n represent variable integers, 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 as the main code, and

wherein letting M and N represent predetermined integers, 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 to produce 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 to produce 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 to produce 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) error code.

3. A digital signal encoding method according to claim 2, 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.

4. A digital signal encoding method according to claim 2, 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.

5. A digital signal encoding method comprising:

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

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 from the signal lower in attribute rank to produce an error code, and

outputting the main code and the error code;

wherein letting m and n represent variable integers, the step (a) comprises, for a set of m=1 and n=1, compression encoding an (m, n) digital signal, and generating an (m, n) code as the main code,

wherein letting M and N represent predetermined integers, 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) error signal, and generating an (m−

1, n) error 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 higher than the n-th sampling frequency, and

generating an (m−

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

1, n+1) error signal.

6. A digital signal encoding method comprising:

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

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 from the signal lower in attribute rank to produce an error code, and

outputting the main code and the error code;

wherein letting m and n represent variable integers, 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 to produce the main code, and

wherein letting M and N represent predetermined integers, 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) error code, and generating an (m, n+1) sub code indicating which of the error signals is selected.

7. A digital signal encoding method comprising:

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

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 from the signal lower in attribute rank to produce an error code, and

outputting the main code and the error code;

wherein letting m and n represent variable integers, 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 ofm=1 and n=1 to produce the main code, and

wherein letting M and N represent predetermined integers, 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) error code by lossless compression encoding the error signal.

8. A digital signal encoding method comprising:

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

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 from the signal lower in attribute rank to produce an error code, and

outputting the main code and the error code;

wherein letting m and n represent variable integers, 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 m=1 and n=1 and outputting an (m, n) code as the main code, and

wherein letting M and N represent predetermined integers, 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) error 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) error code.

9. A digital signal encoding method according to claim 8, 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.

10. A digital signal encoding apparatus comprising main code generating means including a processor 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 to produce a main code,

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 to produce an error code, and

output means for outputting the main code and the error code;

wherein letting m and n represent variable integers, 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 as the main code, and

wherein letting M and N represent predetermined integers, the error signal encoding means comprises an (m, n+1) 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 to produce 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 to produce the compression encoded signal as an (m, n+1) error code,

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 to produce an (m+1, n) precision converted signal, and

an (m+1, n) encoder for compression coding 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 the outputting the compression encoded signal as an (m+1, n) error code.

11. A digital signal encoding apparatus comprising main code generating means including a processor 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 to produce a main code,

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 to produce an error code,

output means for outputting the main code and the error code;

and

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, where m and n represent variable integers,

wherein the main code generating means comprises an (m, n) compressor for generating an (m, n) code as the main code by lossless compression encoding the (m, n) digital signal for a set of m=1 and n=1, and

wherein letting M and N represent predetermined integers, the error signal encoding means comprises;

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) error code by compression encoding the (m−

1, n) error signal,

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)-th sampling 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.

12. A digital signal encoding apparatus comprising main code generating means including a processor 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 to produce a main code,

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 to produce an error code, and

output means for outputting the main code and the error code;

wherein, letting m and n represent variable integers, 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 to produce the main code, and

wherein letting M and N represent predetermined integers, 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)-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 having the m-th quantization precision and the (n+1)-th sampling 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) error code, and

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

13. A digital signal encoding apparatus comprising main code generating means including a processor 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 to produce a main code,

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 to produce an error code, and

output means for outputting the main code and the error code;

wherein letting m and n represent variable integers, 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 to produce the main code, and

wherein letting M and N represent predetermined integers, 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) error code by lossless compression encoding the error signal.

14. A digital signal encoding apparatus comprising main code generating means including a processor 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 to produce a main code,

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 to produce an error code, and

output means for outputting the main code and the error code;

wherein letting m and n represent variable integers, 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 as the main code,

wherein letting M and N represent predetermined integers, 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) error 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) error code.

15. A digital signal encoding method comprising:

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

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 from the signal lower in attribute rank to produce an error code, and

a step (c) for outputting the main code and the error code;

wherein the signal to be encoded is a digital signal of one channel in a first group including a plurality of channels,

wherein one of a signal lower in attribute rand and 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;

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 to produce the main code, 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 to produce an error code 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 to produce an error code of the first group.

16. A digital signal encoding method according to claim 15 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.

17. A digital signal encoding apparatus comprising:

main code generating means including a processor 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 to produce a main code,

lossless coding 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 to produce an error code, and

output means for outputting the main code and the error code;

wherein the signal to be encoded is a digital signal of one channel in a first group including a plurality of channels,

wherein one of a signal lower in attribute rand and 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;

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 to produce the main code, 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 to produce a plurality of first error signals,

a compression encoder for lossless encoding the error signal of the second group to produce an error code 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 to produce an error code of the first group.

18. A digital signal encoding apparatus according to claim 17, 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.

19. A digital signal encoding method comprising:

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

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 from the signal lower in attribute rank to produce an error code, and

a step (c) for outputting the main code and the error code;

wherein the signal to be encoded is a digital signal of one channel in a first group including a plurality of channels,

wherein one of a signal lower in attribute rand and 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;

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 to produce the main code, 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 to produce an error code 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 to produce an error code of the first group.

20. A digital signal encoding apparatus comprising:

main code generating means including a processor 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 to produce a main code,

lossless coding 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 to produce an error code, and

output means for outputting the main code and the error code;

wherein the signal to be encoded is a digital signal of one channel in a first group including a plurality of channels,

wherein one of a signal lower in attribute rand and 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;

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 to produce the main code, 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 an error code of the second group 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 first group, a difference between at least one of the frequency domain signals and the conversion signal, and

a second compression encoder for outputting an error code of the first group by compression encoding the error signal of the first group.