PITCH PERIOD EQUALIZING APPARATUS, PITCH PERIOD EQUALIZING METHOD, SPEECH ENCODING APPARATUS, SPEECH DECODING APPARATUS, SPEECH ENCODING METHOD AND COMPUTERPROGRAM PRODUCTS

摘要

A sound encoding technique capable of achieving a low bit rate and reducing the distortion of reproduced sounds as compared with the prior art. There are included a pitch detecting means (5) for detecting the pitch frequency of an input sound signal; a residual calculating means (6) for calculating the difference (residual frequency) between the pitch frequency and a reference frequency; a frequency shifter (4) for shifting the frequency of the input sound signal in proportion to the residual frequency in such a direction that the frequency of the input sound signal becomes closer to the reference frequency, thereby equalizing the pitch periods; an orthogonal transform means for performing, by use of a given number of pitch intervals, an orthogonal transform of the sound signal (pitch-equalized sound signal) outputted from the frequency shifter (4), thereby producing transform factor data ; and a waveform encoding means for encoding the transform factor data.