Patent ID: 6353808
Filing Date: 2002-03-05
Classification: G10L

Abstract:
A signal coding apparatus for coding an input signal on a time base frame by frame, said frames being used as coding units, the apparatus comprising:normalization means for removing correlation of a waveform of the input signal based on parameters obtained by performing linear prediction coding (LPC) analysis and pitch analysis on each frame of said input signal and outputting a residual signal; envelope extraction means for extracting an envelope from each frame of said residual signal; gain smoothing means for gain-smoothing said residual signal based on the envelope extracted by said envelope extraction means; orthogonal transform means for performing an orthogonal transform operation on an output of said gain smoothing means; and quantization means for quantizing an output of said orthogonal transform means, wherein said envelope extraction means divides said frame into a plurality of sub-frames and calculates a root mean square (rms) value of each sub-frame and outputs said rms values as said envelope, and said quantization means quantizes said rms value of each sub-frame and said gain smoothing means uses the rms value of each sub-frame for a gain smoothing operation.