Pitch period equalizing apparatus and pitch period equalizing method, and speech coding apparatus, speech decoding apparatus, and speech coding method

摘要

To provide a speech coding technology that realizes a low bit rate and can suppress distortion of reproduction speech as compared with a conventional technology.;There are provided pitch detecting means 5 that detects a pitch frequency of an input speech signal, residual calculating means 6 that calculates the difference (residual frequency) between the pitch frequency and a reference frequency, a frequency shifter 4 that shifts a frequency of the input speech signal in proportional to the residual frequency in a direction for being close to the reference frequency and equalizes a pitch period, and orthogonal transforming means that orthogonally transforms the speech signal (pitch-equalizing speech signal) output by the frequency shifter 4 by a constant number of the pitch intervals and generates transforming coefficient data, and waveform coding means that encodes the transforming coefficient data.