Patent ID: 8521522

Claim:
An audio coding device including processing circuitry and programmed to execute a program via the processing circuitry, the program comprising: a time frequency transformation unit configured to perform time-frequency transform on an input audio signal to generate a frequency spectrum; a quantization unit configured to (a) generate total quantization information indicating a quantization bit number on the basis of predetermined normalization information, (b) allocate the total quantization information, by setting a predetermined limit to a first quantization information, allocating, up to the predetermined limit, the total quantization information to the first quantization information, and allocating an excess beyond the predetermined limit to the second quantization information, and (c) in each of a plurality of stages, (i) generate the first quantization information and the second quantization information, each indicating a respective quantization bit number, and (ii) normalize the frequency spectrum for every frequency component by use of a first normalization coefficient corresponding to the normalization information to generate a normalized frequency spectrum, each stage having a predetermined limit to quantization information, and if quantization information allocated for a k-th stage, ‘k’ being an integer greater than zero, exceeds a limit in the k-th stage, an excess for quantization information is allocated to a (k+1)-th stage, the limit being based on a predetermined allowed quantization bit number for each of the respective plurality of stages; a first quantization unit configured to linearly quantize the normalized frequency spectrum by use of a first quantization coefficient corresponding to the first quantization information, to generate a quantized frequency spectrum; a subtraction unit configured to subtract from the frequency spectrum, a frequency spectrum obtained by inversely quantizing and inversely normalizing the quantized frequency spectrum, to generate a differential frequency spectrum; a normalization unit configured to normalize the differential frequency spectrum by use of a second normalization coefficient corresponding to the normalization information and the first quantization information, to generate a differential normalized frequency spectrum; a second normalization unit configured to linearly quantize the differential normalized frequency spectrum by use of a second quantization coefficient corresponding to the second quantization information, to generate a differential quantized frequency spectrum; and a code unit configured to code the normalization information, the first quantization information, the second quantization information, the quantized frequency spectrum, and the differential quantized frequency spectrum, to output a code string.