Data processing: speech signal processing – linguistics – language – Speech signal processing – For storage or transmission
Reexamination Certificate
1999-01-05
2001-10-16
Korzuch, William (Department: 2641)
Data processing: speech signal processing, linguistics, language
Speech signal processing
For storage or transmission
C704S220000, C704S205000, C704S217000, C704S258000
Reexamination Certificate
active
06304843
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a method and apparatus for reconstructing a linear prediction filter excitation signal. Such signal reconstruction is commonly employed in speech coding algorithms where a speech signal is decomposed to a spectral envelope and a residual signal for efficient transmission.
BACKGROUND OF THE INVENTION
The demand for very low bit-rate speech coders (2.4 kb/s and below) has increased significantly in recent years. Applications for these coders include mobile telephony, internet telephony, automatic answering machines and military communication systems as well as voice paging networks. Many speech coding algorithms have been developed for these applications. These algorithms include: Mixed Excitation Linear Prediction Coding (MELP), Prototype Waveform Interpolation Coding (PWI), Sinusoidal Transform Coding (STC) and Multiband Excitation Coding (MBE). In all of these algorithms, only the magnitude information of an LP filter residual signal or a speech signal is transmitted. In use of these algorithms, the phase information is recovered at the decoder by modeling, or simply omitted.
However, omitting phase information in this way results in a synthetic and “buzzing” quality in the decoded speech. Although phase information may be derived from the encoded magnitude spectrum using Sinusoidal Transform Coding, synthetic and “buzzing” qualities still exist in the decoded speech owing to minimum phase assumptions in the speech production model. Improved speech quality has been reported when the phase spectra of some pre-stored waveforms are used, but only a little information from the pre-stored waveforms is revealed using this technique.
It is an object of this invention to provide a method and apparatus for reconstructing a linear prediction systhesis filter excitation signal, for use in speech processing, wherein the above mentioned disadvantages may be alleviated.
BRIEF SUMMARY OF THE INVENTION
In accordance with a first aspect of the present invention there is provided an apparatus for reconstructing a linear prediction filter excitation signal.
In accordance with a second aspect of the present invention there is provided a method of reconstructing a linear prediction filter excitation signal.
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Choi Hung-Bun
Wong Harvey Hau-Fai
Wong Wing Tak Kenneth
Chawan Vijay B
Korzuch William
Motorola Inc.
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