Patent ID: 7613603

Claim:
An audio coding device for encoding an audio signal, comprising: a spatial transform unit that subjects samples of a given audio signal to a spatial transform process, thereby producing transform coefficients grouped into a plurality of subbands according to frequency ranges thereof; a quantization step size calculator that estimates quantization noise from a representative value selected out of the transform coefficients of each subband, and calculates in an approximative way a quantization step size for each subband from the estimated quantization noise, as well as from a masking power threshold that is determined from psycho-acoustic characteristics; a quantizer that quantizes the transform coefficients, based on the calculated quantization step sizes, so as to produce quantized values of the transform coefficients; a scalefactor calculator that calculates a common scalefactor and an individual scalefactor for each subband from the quantization step sizes, the common scalefactor serving as an offset applicable to an entire frame of the audio signal; and a coder that encodes at least one of the quantized values, the common scalefactor, and the individual scalefactors, wherein the quantization step size calculator estimates the quantization noise for nonlinear compression by calculating first an approximate quantization noise of the selected representative value and then multiplying the approximate quantization noise by a correction coefficient.