Encoding method, decoding method, encoder, decoder, program, and recording medium

• US 10,515,643 B2
• Filed: 03/26/2012
• Issued: 12/24/2019
• Est. Priority Date: 04/05/2011
• Status: Active Grant

• Current Assignee: Nippon Telegraph and Telephone Corporation
• Original Assignee: Nippon Telegraph and Telephone Corporation
• Inventors: Moriya, Takehiro, Harada, Noboru, Kamamoto, Yutaka, Hiwasaki, Yusuke, Fukui, Masahiro
• Primary Examiner(s): Blankenagel, Bryan S
• Application Number:
  US14/007,844
• Publication Number:
  US 20140019145A1
• Time in Patent Office: 2,829 Days
• Field of Search: 704219-223, 704229-230, 704500-504
• 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
• CPC Class Codes: G10L 19/005 Correction of errors induced by the transmission channel, if related to the coding algorithm
• CPC Class Codes: G10L 19/008 Multichannel audio signal coding or decoding using interchannel correlation to reduce redundancy, e.g. joint-stereo, intensity-coding or matrixing
• CPC Class Codes: G10L 19/0212 using orthogonal transformation
• CPC Class Codes: G10L 19/032 Quantisation or dequantisation of spectral components
• CPC Class Codes: G10L 19/035 Scalar quantisation
• CPC Class Codes: G10L 19/038 Vector quantisation, e.g. TwinVQ audio
• CPC Class Codes: G10L 19/167 Audio streaming, i.e. formatting and decoding of an encoded audio signal representation into a data stream for transmission or storage purposes
• CPC Class Codes: G10L 19/24 Variable rate codecs, e.g. for generating different qualities using a scalable representation such as hierarchical encoding or layered encoding
• CPC Class Codes: G10L 21/038 using band spreading techniques

Abstract

In encoding, a frequency-domain sample sequence derived from an acoustic signal is divided by a weighted envelope and is then divided by a gain, the result obtained is quantized, and each sample is variable-length encoded. The error between the sample before quantization and the sample after quantization is quantized with information saved in this variable-length encoding. This quantization is performed under a rule that specifies, according to the number of saved bits, samples whose errors are to be quantized. In decoding, variable-length codes in an input sequence of codes are decoded to obtain a frequency-domain sample sequence; an error signal is further decoded under a rule that depends on the number of bits of the variable-length codes; and from the obtained sample sequence, the original sample sequence is obtained according to supplementary information.

Claims

1. An encoding method for encoding, with a predetermined number of bits, a frequency-domain sample sequence derived from an acoustic signal in a predetermined time interval, the encoding method comprising:

an encoding step of encoding, by variable-length encoding, an integer obtained by dividing a value of each sample in the frequency-domain sample sequence by a gain to generate a variable-length code, wherein every integer is encoded regardless of whether the obtained integer is 0 or not;

an error calculation step of calculating error values each obtained by subtracting the integer obtained by dividing the value of each sample in the frequency-domain sample sequence by the gain from a value of a sample obtained by dividing the value of each sample in the frequency-domain sample sequence by the gain; and

an error encoding step of encoding information indicating whether each of the error values is positive or negative with one bit, with a number of surplus bits obtained by subtracting a number of bits of the variable-length code from the predetermined number of bits to generate error codes, the surplus bits being saved by performing the variable-length encoding,

wherein, among said error values, error values whose corresponding integers are not 0 are encoded with priority in the error encoding step.

2. The encoding method according to claim 1, wherein

a value determined based on the integer is regarded as an absolute value of a reconstructed value, the absolute value of the reconstructed value is regarded as a reconstructed value corresponding to each of said error values when the each of said error values is positive, and a value obtained by subtracting the absolute value of the reconstructed value from 0 is regarded as a reconstructed value corresponding to each of said error values when the each of said error values is negative, and

when the number of surplus bits is larger than a number of error samples constituting a sequence of error values, information indicating whether a value obtained by subtracting the reconstructed value corresponding to each error sample from the value of the error sample is positive or negative is further encoded with one bit in the error encoding step.

3. The encoding method according to claim 2, wherein a first absolute value of a first reconstructed value obtained when a first integer is not 0 is larger than a second absolute value of a second reconstructed value obtained when a second integer is 0.

4. A non-transitory computer-readable recording medium having stored thereon a program for causing a computer to execute the steps of the method according to claim 1.

5. An encoder for encoding, with a predetermined number of bits, a frequency-domain sample sequence derived from an acoustic signal in a predetermined time interval, the encoder comprising:

circuitry configured to

encode, by variable-length encoding, an integer obtained by dividing a value of each sample in the frequency-domain sample sequence by a gain to generate a variable-length code, wherein every integer is encoded regardless of whether the obtained integer is 0 or not;

calculate error values each obtained by subtracting the integer obtained by dividing the value of each sample in the frequency-domain sample sequence by the gain from a value of a sample obtained by dividing the value of each sample in the frequency-domain sample sequence by the gain; and

encode information indicating whether each of the error values is positive or negative with one bit, with a number of surplus bits obtained by subtracting a number of bits of the variable-length code from the predetermined number of bits to generate error codes, the surplus bits being saved by performing the variable-length encoding,

wherein the circuitry encodes, among said error values, error values whose corresponding integers are not 0 with priority.