| 摘要 |
PURPOSE:To improve reproducing sound quality by preventing foldover distortion by suppressing the change of each remainder pitch waveform in a frame, and sampling a representative remainder pitch waveform from a smoothed remainder pitch waveform. CONSTITUTION:A shift part 16 performs the phase matching of each remainder pitch, and a Fourier transformation part 17 performs the Fourier transformation of the remainder pitch waveform. Two-dimensional Fourier transformation for the remainder pitch waveform is performed by the transformation part 17 and a Fourier transformation part 19 at the next stage. Since a high-order component represents large change between the remainder pitch waveforms as a result of two-dimensional Fourier transformation, smoothing processing is performed by suppressing a component with such large change, and such processing is performed at a coefficient processing part 20. Thence, inverse Fourier transformation is performed at a two-dimensional inverse Fourier transformation part 21, and the smoothed remainder pitch waveform can be found. The latest remainder pitch waveform is sampled at a representative remainder pitch waveform sampling part 22 as the representative remainder pitch waveform of the frame, and it is quantized at a quantization part 23, then, it is sent to a reception side. |
