PROBLEM TO BE SOLVED: To adjust a bit rate by arithmetically encoding additional information hierarchically, corresponding to data for which input audio signals are quantized for respective prescribed encoding bands by a probability model in an order from a most significant bit sequence composed of the bit of highest importance and a bit sequence composed of the bit of low importance and forming a bit stream. SOLUTION: The signals of a frequency area obtained by converting input signals in a time/frequency mapping part 200 are connected to an appropriate band in a psychoacoustic part 210, and a masking band value is obtained. In a quantization part 220, quantization is performed for the respective prescribed encoding bands so as to make the quantization noise of the respective bands smaller than that of the masking band value. In a bit packing part 240, the quantized data are indicated by the prescribed same number of the bits, gathered by a bit unit, connected and arithmetically encoded by using a prescribed probability model in the order from the most significant bit sequence to the least significant bit sequence from the divided bit. Similar procedures apply for respective hierarchies.
AUDIO ENCODING/DECODING METHOD CAPABLE OF ADJUSTING BIT RATE, DEVICE THEREFOR AND RECORDING MEDIUM WITH THE METHOD RECORDED THEREIN