Patent ID: 8482439

Claim:
An ADPCM encoding apparatus, adapted to input a sampled PCM signal and obtain a differential value between a signal value of the inputted PCM signal at a predetermined time and a decoded signal value one sample before the signal value to obtain an ADPCM signal, comprising: a high-frequency measuring section adapted to detect a first signal that indicates a short-period change of the PCM signal; a low-frequency measuring section adapted to detect a second signal that indicates a long-period change of the PCM signal; an adaptive quantizing section adapted to select a function for changing an adaptive quantization characteristic based on the first signal and the second signal, and use the selected function to quantize the differential value, so as convert the differential value into an ADPCM value; and an adaptive inverse-quantizing section adapted to adaptively inverse-quantize the ADPCM value to obtain the decoded signal value, wherein the adaptive quantizing section comprises a quantizing section which includes a plurality of registers adapted to overwrite the differential value having been subjected to a predetermined calculation by the selected function, and among the plurality of registers, a part of registers are fixed to zero value, and the bits corresponding to the registers fixed to zero value are deleted, so that the differential value is quantized.