Abstract: Every extreme value in an audio waveform represented by a digital audio signal having a sequence of samples is detected. A number of samples between samples corresponding to the first and second latest extreme values is detected. A corrective value is generated in response to the detected sample number and a difference between the first and second latest extreme values. Ones are designated among samples in response to the detected sample number. The designated samples include at least (1) a sample adjacently following the sample corresponding to the second latest extreme value, (2) a sample adjacently preceding the sample corresponding to the first latest extreme value, and (3) one of the sample corresponding to the first latest extreme value and the sample corresponding to the second latest extreme value. The designated samples are corrected in response to at least one of current, previous, and feature corrective values.

Abstract: An audio signal processing apparatus includes first and second tables. The first table has coefficients. The second table has corrective values for correction of the coefficients in the first table. The corrective values are assigned to different sample numbers in at least two successive half-wave signal portions. Detection is made as to a sample number in a corrected-object half-wave portion of a digital audio signal and a sample number in a half-wave portion of the digital audio signal which precedes the corrected-object half-wave portion. The coefficients in the first table are corrected into correction-resultant coefficients in response to the detected sample numbers while the corrective values in the second table are used. Samples in the corrected-object half-wave portion of the digital audio signal are corrected in response to the correction-resultant coefficients.

Abstract: Every extreme value in an audio waveform represented by a digital audio signal having a sequence of samples is detected. A number of samples between samples corresponding to the first and second latest extreme values is detected. A corrective value is generated in response to the detected sample number and a difference between the first and second latest extreme values. Ones are designated among samples in response to the detected sample number. The designated samples include at least (1) a sample adjacently following the sample corresponding to the second latest extreme value, (2) a sample adjacently preceding the sample corresponding to the first latest extreme value, and (3) one of the sample corresponding to the first latest extreme value and the sample corresponding to the second latest extreme value. The designated samples are corrected in response to at least one of current, previous, and feature corrective values.

Abstract: A digital audio signal has a sequence of samples. Extreme values in an audio waveform represented by the digital audio signal are detected. The extreme values include a maximum value and a minimum value. An audio frequency represented by the digital audio signal is detected in response to the number of samples between two temporally-adjacent extreme-corresponding samples. A difference between each extreme value and a value of a sample which immediately precedes the present extreme-corresponding sample is calculated. The calculated differences are multiplied by selected one of predetermined coefficients to get corrective values respectively. A decision is made as to whether or not the detected audio frequency is in one selected from predetermined frequency bands. When the detected audio frequency is in the selected frequency band, a corresponding corrective value is added to the maximum value and a corresponding corrective value is subtracted from the minimum value.

Abstract: Maximal and minimal values represented by samples of a digital audio signal are detected. A number of samples from a sample representing a minimal value to a maximal-value-corresponding sample is detected. A number of samples from a sample representing a maximal value to a minimal-value-corresponding sample is detected. Calculation is given of a first difference between the maximal-value-corresponding sample and the immediately-preceding sample. Calculation is given of a second difference between the minimal-value-corresponding sample and the immediately-preceding sample. First and second coefficients are calculated from the detected sample numbers. The first coefficient and the first difference are multiplied to generate a first multiplication result. The second coefficient and the second difference are multiplied to generate a second multiplication result. The maximal value represented by the maximal-value-corresponding sample is incremented by the first multiplication result.

Abstract: A harmonic generation circuit compares audio data supplied from the outside every sample, detects a top-peak and an under-peak of the audio data on the basis of the comparison outputs, and detects patterns of the comparison output between continuous top-peak and under-peak. The harmonic generation circuit forms an addition-subtraction data corresponding to harmonic depending on the patterns, and supplies the addition-subtraction data to an adder at a timing depending on the patterns. The adder performs an addition-subtraction process for adding/subtracting the addition-subtraction data formed by the harmonic generation circuit to/from the audio data supplied from the outside. In this manner, with a compact, simple, and low-price circuit arrangement for performing only addition-subtraction, a harmonic component can be added to original audio data, and audio data having a wide frequency band can be formed.

Abstract: A digital audio signal to be replayed is processed in a waveform thereof. A frequency bandwidth of the audio signal is expanded through conversion of a sampling frequency, and then the audio signal is low-pass-filtered with a low-pass cut-off frequency corresponding to the converted sampling frequency. An interval of time between two waveform peaks of the audio signal is detected, and then difference data between current data of the audio signal and past data thereof is calculated. The difference data are subject to weighting depending on the interval, and then output data are produced based on both the low-pass-filtered audio signal and the weighted difference data. This processing, which can be realized by activation of software, improves audio quality when compressed audio data is replayed.

Abstract: An audio signal processing apparatus includes first and second tables. The first table has coefficients. The second table has corrective values for correction of the coefficients in the first table. The corrective values are assigned to different sample numbers in at least two successive half-wave signal portions. Detection is made as to a sample number in a corrected-object half-wave portion of a digital audio signal and a sample number in a half-wave portion of the digital audio signal which precedes the corrected-object half-wave portion. The coefficients in the first table are corrected into correction-resultant coefficients in response to the detected sample numbers while the corrective values in the second table are used. Samples in the corrected-object half-wave portion of the digital audio signal are corrected in response to the correction-resultant coefficients.

Abstract: A tone-quality improving portion applies a bit expansion process, an oversampling process, and a bandwidth expansion process to audio information that is decoded by a decoder, and then supplies resultant information to a D/A converter. Accordingly, the audio information can be played back in high tone quality without complicating a configuration of the D/A converter.

Abstract: A digital audio signal has a sequence of samples. Extreme values in an audio waveform represented by the digital audio signal are detected. The extreme values include a maximum value and a minimum value. An audio frequency represented by the digital audio signal is detected in response to the number of samples between two temporally-adjacent extreme-corresponding samples. A difference between each extreme value and a value of a sample which immediately precedes the present extreme-corresponding sample is calculated. The calculated differences are multiplied by selected one of predetermined coefficients to get corrective values respectively. A decision is made as to whether or not the detected audio frequency is in one selected from predetermined frequency bands. When the detected audio frequency is in the selected frequency band, a corresponding corrective value is added to the maximum value and a corresponding corrective value is subtracted from the minimum value.

Abstract: A harmonic generation circuit compares audio data supplied from the outside every sample, detects a top-peak and an under-peak of the audio data on the basis of the comparison outputs, and detects patterns of the comparison output between continuous top-peak and under-peak. The harmonic generation circuit forms an addition-subtraction data corresponding to harmonic depending on the patterns, and supplies the addition-subtraction data to an adder at a timing depending on the patterns. The adder performs an addition-subtraction process for adding/subtracting the addition-subtraction data formed by the harmonic generation circuit to/from the audio data supplied from the outside. In this manner, with a compact, simple, and low-price circuit arrangement for performing only addition-subtraction, a harmonic component can be added to original audio data, and audio data having a wide frequency band can be formed.

Abstract: An interface circuit that is suitable for use in a recording system and a system for manufacturing optical disks, which is provided with this interface circuit, have an analog-side interface circuit 100A and a digital-side interface circuit 100B, these interface circuits being optically linked, either acoustically, or electromagnetically, so as to enable mutual transmitting and receiving of a digital signal therebetween. The interface circuits 100A and 100B, which serve as a receiving side with respect to the other sides, detect the logic of the digital signal with a timing that does not include the jitter component that is included in the transmitted digital signal, the detected digital signal logic being used as the basis for generating a new digital signal.

Abstract: Maximal and minimal values represented by samples of a digital audio signal are detected. A number of samples from a sample representing a minimal value to a maximal-value-corresponding sample is detected. A number of samples from a sample representing a maximal value to a minimal-value-corresponding sample is detected. Calculation is given of a first difference between the maximal-value-corresponding sample and the immediately-preceding sample. Calculation is given of a second difference between the minimal-value-corresponding sample and the immediately-preceding sample. First and second coefficients are calculated from the detected sample numbers. The first coefficient and the first difference are multiplied to generate a first multiplication result. The second coefficient and the second difference are multiplied to generate a second multiplication result. The maximal value represented by the maximal-value-corresponding sample is incremented by the first multiplication result.

Abstract: An interface circuit that is suitable for use in a recording system and a system for manufacturing optical disks, which is provided with this interface circuit, have an analog-side interface circuit 100A and a digital-side interface circuit 100B, these interface circuits being optically linked, either acoustically, or electromagnetically, so as to enable mutual transmitting and receiving of a digital signal therebetween. The interface circuits 100A and 100B, which serve as a receiving side with respect to the other sides, detect the logic of the digital signal with a timing that does not include the jitter component that is included in the transmitted digital signal, the detected digital signal logic being used as the basis for generating a new digital signal.

Abstract: A digital audio signal to be replayed is processed in a waveform thereof. A frequency bandwidth of the audio signal is expanded through conversion of a sampling frequency, and then the audio signal is low-pass-filtered with a low-pass cut-off frequency corresponding to the converted sampling frequency. An interval of time between two waveform peaks of the audio signal is detected, and then difference data between current data of the audio signal and past data thereof is calculated. The difference data are subject to weighting depending on the interval, and then output data are produced based on both the low-pass-filtered audio signal and the weighted difference data. This processing, which can be realized by activation of software, improves audio quality when compressed audio data is replayed.

Abstract: An interface circuit that is suitable for use in a recording system and a system for manufacturing optical disks, which is provided with this interface circuit, have an analog-side interface circuit 100A and a digital-side interface circuit 100B, these interface circuits being optically linked, either acoustically, or electromagnetically, so as to enable mutual transmitting and receiving of a digital signal therebetween. The interface circuits 100A and 100B, which serve as a receiving side with respect to the other sides, detect the logic of the digital signal with a timing that does not include the jitter component that is included in the transmitted digital signal, the detected digital signal logic being used as the basis for generating a new digital signal.

Abstract: A signal processing apparatus transforms N-bit coded data into M-bit coded data, where M is larger than N. The N-bit coded data is obtained by converting an analog signal into a digital signal in the resolution of 1/2.sup.N. First cyclic data of K number sequential N-bit coded data of a sampling period Ts/K is generated in response to input N-bit coded data of a sampling period Ts, where K is a natural number of two or more. The first cyclic data is processed to output second cyclic data of K number sequential M-bit coded data of the sampling period Ts/K.

Abstract: N-bit digital signals are transformed into M-bit digital signals (M>N), the N-bit signals being obtained by converting an analog signal into digital signals. Detected are transition points on a time axis and intervals between the transition points at which successive digital signals of the N-bit signals vary. (M-N) bit additional signals are generated which correct errors of the N-bit signals within a range of .+-.0.5 least significant bit of the N-bit signals in response to the transition points and the intervals. The additional signals are delayed so as to correspond to least significant bit of the N-bit signals. The delayed additional signals are combined with the N-bit signals to generate the M-bit signals. Instead of the transition points and intervals, detected are transition patterns of successive digital signals of the N-bit signals over transition points. (M-N) bit additional signals are generated which correct errors of the N-bit signals within a range of .+-.0.

Abstract: A data signal processing method and apparatus capable of obtaining a high quality signal performs the following operation. M bits of code information are separated into upper N bits and lower (M-N) bits wherein M>N. A change mode of the upper N bits is detected using a first resolution wherein values are represented in units of 1/2.sup.N of the predetermined dynamic range of the signal. A change mode of the lower (M-N) bits is detected using a second resolution wherein values are represented in units of 1/2.sup.M of the predetermined dynamic range. Correction code data is generated at the time when an accumulated value of the lower (M-N) bits reaches the value associated with 1 LSB in the first resolution. The accumulated value is obtained for adding sequential sampling values using the second resolution in each period.

Abstract: A photo coupling device optically connects a transmission unit and a reception unit. The photo coupling device includes a photo emitter and a photo receptor connected via an optical path. The photo emitter is disposed in the transmission unit. The photo emitter is supplied with a transmission digital data signal and generates an optical signal corresponding to the transmission digital data signal. The photo receptor is disposed in the reception unit and receives the optical signal. The photo receptor is switched by short electrical pulses. The photo receptor samples the optical signal and converts the sampled optical signal into a corresponding digital signal at moments of occurrence of the short electrical pulses. A sync signal is transmitted from the transmission unit to the reception unit. The sync signal has a fixed timing relationship with the transmission digital data signal.