Audio encoding apparatus and spectrum modifying method
View Patent ↗A spectrum modifying method and the like wherein the efficiencies of the signal estimation and prediction can be improved and the spectrum can be more efficiently encoded. According to this method, the pitch period is calculated from an original signal, which serves as a reference signal, and then a basic pitch frequency (f 0 ) is calculated. Thereafter, the spectrum of a target signal, which is a target of spectrum modification, is divided into a plurality of partitions. It is specified here that the width of each partition be the basic pitch frequency. Then, the spectra of bands are interleaved such that a plurality of peaks having similar amplitudes are unified into a group. The basic pitch frequency is used as an interleave pitch.
1. A speech coding apparatus, comprising:
an acquiring section that acquires a pitch frequency, or an iterative pattern of a frequency spectrum, of a speech signal;
an interleaving section that interleaves a plurality of spectral coefficients for the speech signal, based on the pitch frequency or the iterative pattern, such that similar spectral coefficients are grouped together out of the plurality of spectral coefficients of the frequency spectrum and adaptively adjusts a duration of an interleaving interval for each frame according to the pitch frequency; and
a coding section that encodes the interleaved spectral coefficients.
2. The speech coding apparatus according to claim 1 , further comprising:
a dividing section that divides the interleaved spectral coefficients into a plurality of bands;
a computing section that computes a ratio of energy of the plurality of bands to energy of a reference signal; and
a gain coding section that encodes the energy ratio.
3. The speech coding apparatus according to claim 1 , further comprising:
a detecting section that detects an interval in which the pitch frequency is present in the speech signal,
wherein the interleaving section performs interleaving processing on the detected interval.
4. A communication terminal apparatus, comprising the speech coding apparatus according to claim 1 .
5. A base station apparatus, comprising the speech coding apparatus according to claim 1 .
6. The speech coding apparatus according to claim 1 ,
wherein the interleaving section interleaves the plurality of spectral coefficients when a current speech frame is determined to be a periodic and stationary signal, and does not interleave the plurality of spectral coefficients when the current speech frame is determined to be a non-period and non-stationary signal.
7. The speech coding method according to claim 1 , further comprising:
a dividing section that divides the plurality of spectral coefficients interleaved by the interleaving section so as to be equal to the interleaving interval or be a multiple of the interleaving interval.
8. The speech coding apparatus according to claim 7 , further comprising:
a deciding section that decides a ratio of an energy of a target signal and an energy of a reference signal in each band divided by the dividing section; and
a gain section that decides a gain for each rate decided by the deciding section and generates a gain signal combined with each decided gain,
wherein the encoding section encodes the gain signal in addition to encoding the spectral coefficients.
9. A spectrum modification method, executed by a speech coding apparatus, comprising:
acquiring, by an acquiring section, a pitch frequency or an iterative pattern of a frequency spectrum of a speech signal;
grouping similar spectral coefficients for the speech signal into a plurality of groups out of a plurality of spectral coefficients of the frequency spectrum, based on the pitch frequency or the iterative pattern; and
interleaving, by an interleaving section, the plurality of spectral coefficients for the speech signal, such that the plurality of spectral coefficients are grouped together into the plurality of groups,
and adaptively adjusting a duration of the interleaving interval for each frame according to the pitch frequency.