Speech coder methods and systems

Inactive Publication Date: 2012-01-10
ALCATEL LUCENT SAS
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  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0009]In particular, spectral warping spreads frequency ranges that substantially effect the perceptual quality of corresponding synthesized speech and compress perceptually less significant frequency ranges. In a corresponding manner, the non-linear transformation performs a magnitude warping operation on the spectral magnitude values. Such transformation amplifies and / or attenuates spectral magnitude values to enhance the characterization of the perceptual quality of a corresponding synthesized speech signal.
[0011]In contrast, the present invention processes the spectral component values by spectral warping and / or non-linear transformation to produce a transformed and / or warped characterization that causes subsequent spectral coding, such as by linear predictive analysis, to provide more coding resources for perceptually more significant spectral components and less coding resources to those spectral components that are less perceptually significant. Accordingly, the resulting synthesized voiced speech produced from such a coded signal would have an improved perceptual quality while maintaining an advantageous coding efficiency relative to the coding process alone.
[0012]A corresponding decoder according to the invention employs a complementary inverse non-linear transformation and / or spectral warping process to obtain the corresponding approximation of the original short-term frequency spectrum of the respective frames of the speech signal with improved perceptual quality.

Problems solved by technology

In other words, typical coding techniques do not perform coding of frequency components of the short-term frequency spectrum characterization based on the perceptual accuracy such frequency components produce in a corresponding synthesized speech signal.

Method used

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  • Speech coder methods and systems
  • Speech coder methods and systems

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Embodiment Construction

[0025]The invention advantageously employs processing of successive frames of a speech signal by performing a non-linear transformation and / or spectral warping process on a spectral magnitude value sequences characterizing the short-term frequency spectrum of respective voiced speech frames prior to spectral coding by, for example, linear predictive analysis. As used herein, “short-term frequency spectrum” refers to spectral characteristics arising from the short-term correlation in the speech signal excluding the correlation resulting from the pitch periodicity. The short-term frequency spectrum is alternatively referred to as the short-time frequency spectrum in the art, and is described in greater detail in L. R. Rabiner and R. W. Schafer, Digital Processing of Speech Signals, sects. 6.0-6.1, pp. 250-282 (Prentice-Hall, New Jersey, 1978), which is incorporated by reference herein in its entirety.

[0026]Spectral warping spreads or compresses particular frequency ranges represented ...

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Abstract

Coding systems that provide a perceptually improved approximation of the short-term characteristics of speech signals compared to typical coding techniques such as linear predictive analysis while maintaining enhanced coding efficiency. The invention advantageously employs a non-linear transformation and / or a spectral warping process to enhance particular short-term spectral characteristic information for respective voiced intervals of a speech signal. The non-linear transformed and / or warped spectral characteristic information is then coded, such as by linear predictive analysis to produce a corresponding coded speech signal. The use of the non-linear transformation and / or spectral warping operation of the particular spectral information advantageously causes more coding resources to be used for those spectral components that contribute greater to the perceptible quality of the corresponding synthesized speech. It is possible to employ this coding technique in a variety of speech coding techniques including, for example, vocoder and analysis-by-synthesis coding systems.

Description

FIELD OF THE INVENTION[0001]The invention relates generally to speech communication systems and more specifically to systems for encoding and decoding speech.BACKGROUND OF THE INVENTION[0002]Digital speech communication systems including voice storage and voice response systems use speech coding and data compression techniques to reduce the bit rate needed for storage and transmission. Voiced speech is produced by a periodic excitation of the vocal tract by the vocal chords. As a consequence, a corresponding signal for voiced speech contains a succession of similarly but evolving waveforms having a substantially common period which is referred to as the pitch period. Typical speech coding systems take advantage of short-term redundancies within a pitch period interval to achieve data compression in a coded speech signal.[0003]In a typical voice coder (vocoder) system, such as that described in U.S. Pat. No. 3,624,302, which is incorporated by reference herein, the speech signal is p...

Claims

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Application Information

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IPC IPC(8): G10L19/02G10L19/00G10L19/04G10L19/06H03M7/30H04B14/04
CPCG10L19/0212G10L19/06
InventorLAROIA, RAJIVYEO, BOON-LOCK
OwnerALCATEL LUCENT SAS