Data processing: speech signal processing – linguistics – language – Speech signal processing – For storage or transmission
Reexamination Certificate
1999-01-26
2001-08-21
{haeck over (S)}mits, T{overscore (a)}livaldis Ivars (Department: 2641)
Data processing: speech signal processing, linguistics, language
Speech signal processing
For storage or transmission
C704S207000, C704S265000, C704S269000
Reexamination Certificate
active
06278971
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a phase detection apparatus and method, and an audio coding apparatus and method, for detecting phases of harmonics components in a sinusoidal wave combine coding or the like.
2. Description of the Prior Art
Various coding methods are known to carry out signal compression utilizing statistical features and human hearing sense characteristics in a time region and frequency region of an audio signal (including a voice signal and an acoustic signal). These coding methods can be briefly classified into time region coding, frequency region coding, and analysis-synthesis coding.
As a high-efficiency coding of an audio signal or the like, there are known sinusoidal coding schemes such as harmonic coding and multi-band excitation (MBE) coding, and sub-band coding (SBC), linear predictive coding (LPC), or discrete cosine transform (DCT), modified DCT (MDCT), fast Fourier transform (FFT), and the like.
In the high-efficiency audio coding using the sinusoidal coding such as the MBE coding, harmonic coding, and sinusoidal transform coding (STC) for an input audio signal or using these sinusoidal coding methods for an input audio signal LPC, information is transmitted on an amplitude or spectrum envelope of each sinusoidal wave (harmonics, higher harmonics) serving as a component of analysis-synthesis. However, no information on phase is transmitted. The phase is calculated during synthesis if necessary.
Accordingly, there is a problem that an audio waveform reproduced after decoding is different from a waveform of the original input audio signal. That is, in order to reproduce the original waveform, it is necessary to detect and transmit phase information of each harmonics (higher harmonics) component for each frame.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a phase detection apparatus and method for realizing reproduction of an original waveform as well as an audio coding apparatus and method employing this phase detection technique.
In the phase detection apparatus and method according to the present invention, one-pitch cycle of an input signal waveform based on an audio signal is cut out on a time axis. The cut-out one-pitch cycle of samples is subjected to an orthogonal conversion such as FFT. According to a real part and an imaginary part of data which has been orthogonally converted, phase information is detected for each higher harmonics component of the aforementioned input signal.
According to another aspect of the present invention, the aforementioned phase detection is applied to an audio coding such as sinusoidal coding.
Here, the aforementioned input signal waveform may be an audio signal waveform itself or a signal waveform of a short-term prediction residue of the audio signal.
Moreover, it is preferable that the aforementioned cut-out waveform data is filled with zeroes into 2
N
samples (where N is an integer, 2
N
is equal to or greater than the number of samples of the aforementioned one-pitch cycle) when subjected to an orthogonal conversion, which is preferably the fast Fourier transform.
Furthermore, the aforementioned phase detection may be performed by using a real part and an imaginary part of the data obtained by the orthogonal conversion, so as to calculate an inverse tangent (tan
−1
) to obtain a phase of each higher harmonics component.
REFERENCES:
patent: 5504833 (1996-04-01), George et al.
patent: 5884253 (1999-03-01), Kleijn
patent: 5911130 (1999-06-01), Shimizu et al.
patent: 5987413 (1999-11-01), Dutoit et al.
patent: 6115685 (2000-09-01), Inoue et al.
patent: 0698876 (1996-02-01), None
patent: 08330971 (1996-12-01), None
Vocal system phase decoder for sinusoidal speech, S. Torres and F.J. Casajús-Quirós, Electroncis Letters, vol. 33, No. 20, pp. 1683-1685.
Inoue Akira
Nishiguchi Masayuki
Maioli Jay H.
Sony Corporation
{haeck over (S)}mits T{overscore (a)}livaldis Ivars
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