| 摘要 |
When a decoding audio signal is to be acquired by pitch-filtering a combined signal of a sub-frame length, a decoding audio signal is continuously changed at the boundary between sub-frames. The post filter includes: a first filter coefficient calculation unit (306) which obtains a pitch filter coefficient gP(0) of a current frame so as to asymptotically approach the intensity g of the pitch filter from an initial value 0; a second filter coefficient calculation unit (307) which obtains a pitch filter coefficient gP(-1) of a preceding frame so as to asymptotically approach 0 by setting the initial value to the value of the pitch filter coefficient obtained by the first filter coefficient calculation unit (306); a filter state setting unit (308) which sets a pitch filter state fsi for each of the sub-frames; and a pitch filter (309) which pitch-filters the combined signal xi by using the pitch filter coefficients gP(-1), gP(0), and past demodulation audio signals yi-P(-1), yi-P(0).
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