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Bitstream-based feature extraction method for a front-end speech recognizer

a feature extraction and front-end speech technology, applied in speech analysis, speech recognition, instruments, etc., can solve the problem that the schema cannot generate synthesized speech of the quality produced by the system

Inactive Publication Date: 2005-06-30
NUANCE COMM INC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0009] In accordance with the present invention, the bitstream of the encoded speech is applied in parallel as inputs to both a front-end speech decoder and feature extractor. The feature parameters consist of both spectral envelope and voicing information. The spectral envelope is derived from the quantized line spectrum pairs (LSPs) followed by conversion to LPC cepstral coefficients. The voiced / unvoiced information is directly obtained from the bits corresponding to adaptive and fixed codebook gains of a speech coder. Thus, the cepstrum is directly converted in the speech decoder from the spectral information bits of the speech coder. The use of both the spectral envelope information and the voiced / unvoiced information yields a front-end feature extractor that is greatly improved over the prior art models.

Problems solved by technology

However, this scheme is not able to generate synthesized speech of the quality produced by the system as shown in FIG. 1(a).

Method used

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  • Bitstream-based feature extraction method for a front-end speech recognizer
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Embodiment Construction

[0020] A bitstream-based approach for providing speech recognition in a wireless communication system in accordance with the present invention is illustrated in FIG. 2. As shown, a system 30 utilizes a conventional speech encoder 32 at the transmission end, where for explanatory purposes it will be presumed that an IS-641 speech coder is used, however, various other coders also function reliably in the arrangement of the present invention (in particular, code-excited linear prediction—CELP encoders). The encoded speech thereafter propagates along a (wireless) communication channel 34 and is applied as simultaneous inputs to both a speech decoder 36 and a speech recognition feature extractor 38, where the interaction of these various components will be discussed in detail below.

[0021]FIG. 3 includes a simplified block diagram of the linear predictive coding (LPC) analysis associated with speech coding performed using an IS-641 speech coder. As shown, the speech coder first removes u...

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Abstract

A feature extraction process for use in a wireless communication system provides automatic speech recognition based on both spectral envelope and voicing information. The shape of the spectral envelope is used to determine the LSPs of the incoming bitstream and the adaptive gain coefficients and fixed gain coefficients are used to generate the “voiced” and “unvoiced” feature parameter information.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application claims the priority of Provisional Application No. 60 / 170,170, filed Dec. 10, 1999.TECHNICAL FIELD [0002] The present invention relates to automatic speech recognition and, more particularly, to a bitstream-based feature extraction process for wireless communication applications. BACKGROUND OF THE INVENTION [0003] In the provisioning of many new and existing communication services, voice prompts are used to aid the speaker in navigating through the service. In particular, a speech recognizing element is used to guide the dialogue with the user through voice prompts, usually questions aimed at defining which information the user requires. An automatic speech recognizer is used to recognize what is being said and the information is used to control the behavior of the service rendered to the user. [0004] Modern speech recognizers make use of phoneme-based recognition, which relies on phone-based sub-word models to perform ...

Claims

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Application Information

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IPC IPC(8): G10L15/02
CPCG10L15/02
Inventor COX, RICHARD VANDERVOORTKIM, HONG KOOK
Owner NUANCE COMM INC