| 摘要 |
<p>PROBLEM TO BE SOLVED: To improve subjective quality of reproduced sound by effectively removing quantization noise when decrypting and reproducing an acoustic signal encoded with a prediction encoding method.SOLUTION: A filter for removing quantization noise is selected from among a plurality of digital filters whose characteristics are regulated with a group of filter functions with tap length as parameters and whose filter coefficients have positive/negative symmetry. In the group of filter functions, the filter coefficients are decided such that the gain has a curve monotonously decreasing from 1 in a zero frequency to 0 in a Nyquist frequency in the transfer function. The selection of a specific filter function from the group of filter functions is performed on the basis of the difference of energies obtained for each tap length by calculating energies removed when each of the plurality of filters regulated with a group of functions with tap length as parameters is applied for an original signal and the quantization noise.</p> |
