Phase quantization method and apparatus

Details Phase quantization method and apparatus Phase quantization method and apparatus

1999-01-29

2001-09-18

Korzuch, William (Department: 2641)

Data processing: speech signal processing, linguistics, language

Speech signal processing

For storage or transmission

C704S207000, C704S219000, C704S220000, C704S229000

Reexamination Certificate

active

06292777

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a method and apparatus for detecting and quantizing the phase of high harmonics components in sine wave synthesis encoding.
2. Description of the Related Art
There are known a variety of encoding methods for audio signals (inclusive of speech and acoustic signals) in which the signals are compressed by exploiting statistic properties in the time domain and in the frequency domain of the audio signals and psychoacoustic characteristics of the human being. These encoding methods may be roughly classified into time-domain encoding, frequency domain encoding and analysis-synthesis encoding.
Examples of the high efficiency encoding of speech signals etc include sinusoidal coding, such as harmonic encoding, multi-band excitation (MBE) encoding, sub-band coding, linear predictive coding (LPC), discrete cosine transform (DCT) encoding, modified DCT (MDCT) encoding and fast Fourier transform (FET).
Meanwhile, in high efficiency speech coding, employing the above-mentioned MBE encoding, harmonics encoding or sinusoidal transform coding (STC) for input speech signals, or employing the sinusoidal coding for linear prediction coding residuals (LPC residuals) of input speech signals, the information concerning the amplitude or the spectral envelope of respective sine waves (harmonics) as elements of analysis/synthesis is transmitted. However, the phase is not transmitted and simply the phase is calculated suitably at the time of synthesis.
Thus, a problem is raised that the speech waveform, reproduced on decoding, differs from the waveform of the original input speech waveform. That is, for realizing the replica of the original speech signal waveform, it is necessary to detect the phase information of the respective harmonics components frame-by-frame and to quantize the information with high efficiency to transmit the resulting quantized signals.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a phase quantization method and apparatus whereby it is possible to produce the replica of the original waveform.
With the phase quantization method and device according to the present invention, the phase of respective harmonics of signals derived from the input speech signals is quantized depending on the number of assigned bits as found by calculations to quantize the phase information of the input signal waveform derived from the speech signals efficiently.
The input signal waveform may be the speech signal waveform itself or the signal waveform of short-term prediction residuals of the speech signals.
Also, with the phase quantization method and device according to the present invention, the optimum number of assigned quantization bits of the respective harmonics is calculated from the spectral amplitude characteristics of the input speech signals and the phase of the harmonics components of the input speech signals and short-term prediction residual signals of the input speech signal is scalar-quantized, under separation of fixed delay components if so required, in order to effect phase quantization efficiently.
With the phase quantization method and device according to the present invention, the phase of the respective harmonics components of signals derived from the input speech signals is quantized responsive to the number of assigned bits as found by calculations in order to effect phase quantization efficiently.
By the above configuration, the decoding side is able to detect the phase information of the original waveform to improve the waveform reproducibility. In particular, if the present method and device are applied to speech encoding for sinusoidal synthesis encoding, waveform reproducibility can be improved to prohibit the non-spontaneous synthesized speech.


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