Abstract: A low-pass filter of over-sampling type oversamples an input digital audio signal T1 and filters and removes the low frequency components of the produced aliasing noise. A spectrum analyzer circuit calculates the spectrum intensity of a predetermined band of an output signal from the low-pass filter. An expanded signal generating circuit generates an expanded signal having frequency components of the output signal from the low-pass filter. A level control circuit controls the level of the expanded signal according to the spectrum analyzer circuit. An adder adds the level-controlled expanded signal to the output signal from the low-pass filter thereby to generate a digital audio signal T2.

Abstract: For audio data configured in units of frames with a header at the top and compressed in a way such that data corresponding to a specific frame is also present in a different frame, the present invention executes at least one of the following processing (1) and processing (2) at dividing this compressed audio into two pieces of audio data, i.e., front and rear pieces, at a predetermined position. (1) A step to divide the audio data into front and rear pieces, and a step to add data of a predetermined number of bytes at the beginning of the rear audio data to an end of the front audio data. (2) A step to divide the audio data into front and rear pieces, and a step to add data of a predetermined number bytes from an end of the front audio data to the front of the beginning of the rear audio data. This prevents the generation of abnormal noise even when data is compressed in a way, typically in MP3, such that location of a frame and location of data for that frame do not always match.

Abstract: It purposes to provide a D/A conversion apparatus of a high accuracy oversampling method by noise shaping which is not needed a high frequency clock or accurate working, and a high accuracy A/D conversion apparatus having a configuration to which said D/A conversion technology is applied. It has configuration outputting the digital signal by dividing to plural 1-bit D/A converters, and by using said D/A converters so as to circulate, correlation of the signal and the output value of a specified 1-bit D/A converter is canceled, and noise or distortion due to a relative error of the 1-bit D/A converter is reduced.

Abstract: An offset reducer includes an adder for adding an input signal and an offset cancel signal to reduce an offset component of the input signal. A converter serves to measure a difference between a sum of past periods during which an output signal of the adder was positive and a sum of past periods during which the output signal of the adder was negative. The converter outputs an offset detection signal of a given value which depends on a sign of the measured difference when an absolute value of the measured difference exceeds a given difference. The converter initializes the measured difference to a given initial difference when the offset detection signal is outputted. An integrator serves to accumulate the offset detection signal outputted from the converter. The integrator generates the offset cancel signal in accordance with a result of the accumulating the offset detection signal. The output signal of the adder constitutes an offset-free signal corresponding to the input signal.