Abstract: An autocorrelation calculation unit 21 calculates an autocorrelation RO(i) from an input signal. A prediction coefficient calculation unit 23 performs linear prediction analysis by using a modified autocorrelation R?O(i) obtained by multiplying a coefficient wO(i) by the autocorrelation RO(i). It is assumed here, for each order i of some orders i at least, that the coefficient wO(i) corresponding to the order i is in a monotonically increasing relationship with an increase in a value that is negatively correlated with a fundamental frequency of the input signal of the current frame or a past frame.

Abstract: In encoding, the number of bits to be assigned to codes corresponding to noise or a pulse sequence obtained according to prediction analysis applied to time series signals included in a predetermined time interval is switched according to whether an index that indicates a level of periodicity and/or stationarity of input time series signals satisfies a condition that indicates high periodicity and/or high stationarity or a condition that indicates low periodicity and/or low stationarity, to acquire the codes corresponding to the noise and the pulse sequence. In decoding, a decoding mode for codes corresponding to noise or a pulse sequence included in codes corresponding to a predetermined time interval is switched according to the same criterion as that described above to decode the codes corresponding to the noise or the pulse sequence to acquire noise or a pulse sequence corresponding to the predetermined time interval.

Abstract: In a speech coding scheme based on a speech production model, such as a CELP-based scheme, an object of the present invention is to provide a decoding method that can reproduce natural sound even if the input signal is a noise-superimposed speech. The decoding method includes a speech decoding step of obtaining a decoded speech signal from an input code, a noise generating step of generating a noise signal that is a random signal, and a noise adding step of outputting a noise-added signal, the noise-added signal being obtained by summing the decoded speech signal and a signal obtained by performing, on the noise signal, a signal processing that is based on at least one of a power corresponding to a decoded speech signal for a previous frame and a spectrum envelope corresponding to the decoded speech signal for the current frame.

Abstract: Between a method in which an integer signal code is obtained by using an encoding method based on periodicity and a method in which an integer signal code is obtained using an encoding method which is not based on periodicity using an index indicating a degree of periodicity of a sample sequence in a frequency domain, processing of a first coder is executed only in a method for which the number of bits of the integer signal code is expected to be reduced, and a gain obtained through the processing of the first coder in the method for which the number of bits of the integer signal code is expected to be reduced is utilized in a method for which the number of bits of the integer signal code is not expected to be reduced.

Abstract: In encoding for putting one or more files and/or one or more files in a folder into a single archive file, original hierarchy information and standard hierarchy information generated by converting characters in a special character coding in each file name to characters in a standard character coding are recorded in the archive file. If the character coding used in the original hierarchy information in the archive file cannot be used in the system environment used in decoding, a file name in the standard character coding is generated from the standard hierarchy information and is converted to a character coding that can be used in the system environment.

Abstract: A value of gain is updated so that the greater the difference between the number of bits or estimated number of bits in a code obtained by encoding a string of integer value samples obtained by dividing each sample in a sample string derived from an input audio signal in a given interval by gain before the update and a predetermined number B of allocated bits, the greater the difference between the gain before the update and the updated gain. A gain code corresponding to the updated gain and an integer signal code obtained by encoding a string of integer value samples obtained by dividing each sample in the sample string by the gain are obtained.

Abstract: A frequency-domain sample interval corresponding to a time-domain pitch period L corresponding to a time-domain pitch period code of an audio signal in a given time period is obtained as a converted interval T1, a frequency-domain pitch period T is chosen from among candidates including the converted interval T1 and integer multiples U×T1 of the converted interval T1, and a frequency-domain pitch period code indicating how many times the frequency-domain pitch period T is greater than the converted interval T1 is obtained. The frequency-domain pitch period code is output so that a decoding side can identify the frequency-domain pitch period T.

Abstract: A lossless coding technique for near-logarithmic companded PCM that achieves high compression performance is provided. In coding, the coding method that produces the smaller code amount is selected between the prediction coding method, which performs linear prediction of samples in a frame and codes the amplitude of the prediction error, and the normalization coding method, which normalizes the amplitude of the samples in the frame and codes the normalized amplitude, and a selection code that indicates the selection result is output. The samples in the frame are coded according to the selected coding method to produce a compression code. In decoding, the compression code is decoded according to a decoding process corresponding to the coding method specified by the selection code.

Abstract: On a criterion to minimize the entropy of the linear prediction residual of the input signal used for calculation of the input PARCOR coefficient sequence, PARCOR coefficients with larger absolute values are quantized with higher quantization precisions so as to reduce the increase of the code amount of the linear prediction residual caused by the quantization error of the PARCOR coefficients. If the PARCOR coefficient is represented by a value formed by a predetermined number of bits, the number of effective bits from the most significant bit toward the least significant bit included in the output value increases with the absolute value of the PARCOR coefficient.

Abstract: To improve the encoding compressibility of prediction residuals. An encoder performs prediction analysis of input time-series signals to generate prediction residuals expressed by integers, and sets an integer separation parameter that depends on the amplitude of the prediction residuals for each certain time segment. The encoder selects a side information code table corresponding to an index representing the prediction effectiveness of the time-series signals from a set of side information code tables including a side information code table used for variable length coding of side information corresponding to the separation parameter.

Abstract: An object of the present invention is to achieve high coding efficiency for a companded signal sequence and reduce the amount of codes. A coding method according to the present invention includes an analysis step and a signal sequence transformation step. The analysis step is to check whether or not there is a number that is included in a particular range but does not occur in a second signal sequence (a number sequence that indicates the magnitude (magnitude relationship) of original signals) and output information that indicates the number that does not occur.

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.

Abstract: In encoding, the number of bits to be assigned to codes corresponding to noise or a pulse sequence obtained according to prediction analysis applied to time series signals included in a predetermined time interval is switched according to whether an index that indicates a level of periodicity and/or stationarity of input time series signals satisfies a condition that indicates high periodicity and/or high stationarity or a condition that indicates low periodicity and/or low stationarity, to acquire the codes corresponding to the noise and the pulse sequence. In decoding, a decoding mode for codes corresponding to noise or a pulse sequence included in codes corresponding to a predetermined time interval is switched according to the same criterion as that described above to decode the codes corresponding to the noise or the pulse sequence to acquire noise or a pulse sequence corresponding to the predetermined time interval.

Abstract: An encoding technique encoding a sound signal at a low bit rate with reduced processing. The technique includes: an interval determination determining an interval T between samples corresponding to periodicity of an audio signal or an integer multiple of a fundamental frequency of the audio signal from a set S of candidates for the interval T; and a side information generating encoding the determined interval T to obtain side information. The interval determining determines the interval T from a set S of Y candidates (Y<Z) including Z2 candidates (Z2<Z) selected from among Z candidates for the interval T representable with the side information without depending on a candidate subjected to the interval determination in a previous frame a predetermined number of frames before the current frame and including a candidate subjected to the interval determination in the previous frame the predetermined number of frames before the current frame.

Abstract: A frame formed of a plurality of code words encoded with an encoding mode in which two different types of code words are assigned one-to-one to two smallest quantization intervals is checked to determine whether it contains just the two types of code words assigned to the two smallest quantization intervals, and lossless encoding is applied to the frame containing just the two types of code words. A code obtained by this lossless encoding is decoded with a decoding method corresponding to the lossless encoding.

Abstract: Provided that a first segment is an earliest time segment included in a discrete time segment, and a second segment is a time segment subsequent to the first segment, a positive second-segment parameter that corresponds to a weakly monotonically increasing function value of an average amplitude of prediction residuals in a time segment including the second segment is used as a parameter for variable length coding of prediction residuals in the second segment. In addition, a value that corresponds to a weakly monotonically increasing function value of the sum of the second-segment parameter and a positive additional value that corresponds to an index representing the prediction effectiveness of time-series signals in the time segment including the second segment is used as a parameter for variable length coding of the prediction residual at a certain discrete time in the first segment.

Abstract: An integer value sequence is used as an input, and [1] codes corresponding to integers (referred to as specified integers) and [2] codes (referred to as extension codes) corresponding to sets of a plurality of integers other than the specified integers are previously determined. Coding is performed in such a manner that the code corresponding to the specified integer is adopted as the result of the coding if an integer value to be coded in the integer value sequence is the specified integer, and a code obtained by combining the extension code and a code obtained by applying a predetermined coding method corresponding to the extension code to the integer value to be coded is adopted as the result of the coding if the integer value to be coded in the integer value sequence is not the specified integer.

Abstract: Information that includes first information identifying integer quotients obtained by divisions using prediction residuals or integers not smaller than 0 that increase monotonically with increases in the amplitude of the prediction residuals, as dividends, and a separation parameter decided for a time segment corresponding to the prediction residuals or a mapped integer value of the separation parameter, as a modulus, and second information identifying the remainders obtained when the dividends are divided by the modulus is generated as a code corresponding to the prediction residuals, and each piece of side information that includes the separation parameter is subjected to variable length coding.

Abstract: In encoding for putting one or more files and/or one or more files in a folder into a single archive file, original hierarchy information and standard hierarchy information generated by converting characters in a special character coding in each file name to characters in a standard character coding are recorded in the archive file. If the character coding used in the original hierarchy information in the archive file cannot be used in the system environment used in decoding, a file name in the standard character coding is generated from the standard hierarchy information and is converted to a character coding that can be used in the system environment.

Abstract: In encoding for putting one or more files and/or one or more files in a folder into a single archive file, original hierarchy information and standard hierarchy information generated by converting characters in a special character coding in each file name to characters in a standard character coding are recorded in the archive file. If the character coding used in the original hierarchy information in the archive file cannot be used in the system environment used in decoding, a file name in the standard character coding is generated from the standard hierarchy information and is converted to a character coding that can be used in the system environment.