Patent ID: 7263407

Claim:
A method of processing a digital audio signal having a sequence of samples, the method comprising the steps of: detecting extreme values in an audio waveform represented by the digital audio signal, the detected extreme values including a detected maximum value and a detected minimum value; counting samples between a sample corresponding to first one of the detected extreme values and a sample corresponding to second one of the detected extreme values to get a count result; detecting an audio frequency represented by the digital audio signal in response to the count result; calculating a difference between each of the detected extreme values and a value of a sample which immediately precedes a sample corresponding to the present detected extreme value; selecting one from predetermined frequency bands different from each other; selecting one from predetermined coefficients different from each other; multiplying the calculated differences by the selected coefficient to get corrective values respectively; deciding whether or not the detected audio frequency represented by the digital audio signal is in the selected frequency band; and when it is decided that the detected audio frequency is in the selected frequency band, adding, to the detected maximum value, corresponding one of the corrective values, and subtracting, from the detected minimum value, corresponding one of the corrective values.