PURPOSE: To further compress the information amount of a waveform in the case where the amplitude value of the waveform is represented with floating point data consisting of a mantissa part and an exponent part as to compression technology for the waveform that is used for an electronic musical instrument, etc.
CONSTITUTION: Differential waveform data 112 are converted into the floating point data consisting of the three-bit exponent part 114 and 7-bit mantissa part 115. Then only a 3-bit exponent part which is larger in value is selected between every two 3-bit exponent parts, the respective values of the selected data sequence are so limited that difference values between values of adjacent data are four values that are -1, 0, 1, and 2, and a compressed 3-bit difference compressed exponent part 133 is calculated. The 2-bit difference compressed exponent part 133 and a 7-bit mantissa part 127 which is recalculated from it are outputted as encoded data.
SATO HIROTAKE
TANAKA KIKUJI
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