| 摘要 |
PURPOSE:To attain processing in a short time, to minimize the deterioration in sound quality and to decrease a bit rate by setting a quantization characteristic in the case of quantization based on a specific allowable noise level. CONSTITUTION:The coder is provided with a masking spectrum calculation circuit 75 being a 1st noise level setting means setting a 1st allowable noise level based on energy of each frequency component within a prescribed period in outputs of FFT(Fast Fourier Transforming) circuits 20,40,60. Moreover, period delay circuits 23,43,63 or the like being a 2nd noise level setting means setting 2nd allowable noise level based on energy one of data preceding and succeeding timewise within a prescribed period in outputs of the FFT circuits 20,40,60 are provided. Then the quantization characteristic of the quantization circuits 29,49,69 is set based on the output of the 1st and 2nd noise level setting means. Thus, processing in a short time is attained, the deterioration in sound quality is minimized and a bit rate is decreased. |
