Patent ID: 7243061

Claim:
An audio signal coding apparatus which receives an audio signal which is subjected to time-frequency transform to output index information, comprising: a plurality of stages of sub-quantization units, at least the i-th stage sub-quantization unit including a plurality of band division quantizers each of which being operable to perform coding using vector quantization for a respective part of a divided frequency band; each of the (i+1)th and subsequent stage sub-quantization units being operable to perform coding using vector quantization on a quantization error of the band division quantizer that has performed decoding on a part of the band at the previous stage; and a quantization band selection unit operable to select the parts of the divided frequency band for quantization by the band division quantizers in the (i+1)th and subsequent stage sub-quantization units, on the basis of the magnitude of the quantization errors from a previous stage sub-quantization unit; wherein: the index information includes a stage-specific index indicating a vector coded by the sub-quantization unit of each stage; and the stage-specific index includes a band-specific index for each part of the divided frequency band at the stage in which codings with dividing the frequency band are performed by the plurality of band division quantizers.