EP0496829B1 - Auf dem lpc-verfahren beruhende sprachsynthese mit adaptivem pitchvorfilter - Google Patents

Auf dem lpc-verfahren beruhende sprachsynthese mit adaptivem pitchvorfilter Download PDF

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Publication number
EP0496829B1
EP0496829B1 EP90916987A EP90916987A EP0496829B1 EP 0496829 B1 EP0496829 B1 EP 0496829B1 EP 90916987 A EP90916987 A EP 90916987A EP 90916987 A EP90916987 A EP 90916987A EP 0496829 B1 EP0496829 B1 EP 0496829B1
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EP
European Patent Office
Prior art keywords
signal
pitch
excitation signal
filter
speech
Prior art date
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Expired - Lifetime
Application number
EP90916987A
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English (en)
French (fr)
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EP0496829A1 (de
EP0496829A4 (en
Inventor
Ira Alan Gerson
Mark Antoni Jasiuk
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Motorola Solutions Inc
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Motorola Inc
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Publication date
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    • G—PHYSICS
    • G10—MUSICAL INSTRUMENTS; ACOUSTICS
    • G10L—SPEECH ANALYSIS TECHNIQUES OR SPEECH SYNTHESIS; SPEECH RECOGNITION; SPEECH OR VOICE PROCESSING TECHNIQUES; SPEECH OR AUDIO CODING OR DECODING
    • G10L19/00—Speech or audio signals analysis-synthesis techniques for redundancy reduction, e.g. in vocoders; Coding or decoding of speech or audio signals, using source filter models or psychoacoustic analysis
    • G10L19/04—Speech or audio signals analysis-synthesis techniques for redundancy reduction, e.g. in vocoders; Coding or decoding of speech or audio signals, using source filter models or psychoacoustic analysis using predictive techniques
    • G10L19/26—Pre-filtering or post-filtering

Definitions

  • This invention relates generally to speech synthesis, and more particularly to linear predictive coding based speech synthesis.
  • the synthesis of speech through use of a linear predictive coding (LPC) based platform is known in the art.
  • a prior art radio that embodies such a platform is depicted generally in Fig. 1 by the reference numeral 100.
  • the radio (100) receives a speech coded signal (101) through an appropriate energy transducer (102), such as an antenna.
  • An RF unit (103) converts the received signal (101) to baseband and demodulates the signal to recover the speech coded information.
  • a parameter decoder (105) develops control parameters for various subsequent processes from this information.
  • An excitation source (104) utilizes the parameters provided to it to create an excitation signal and then provides that excitation signal (which excitation signal includes pitch information that has been inserted by a pitch filter) to an LPC filter (106) which in turn provides, at its output, a synthesized speech signal.
  • This synthesized speech signal is then filtered in an adaptive pitch postfilter (107) and an adaptive spectral postfilter (108), as well as a post emphasis filter (109), to enhance the perception of natural speech and to minimize the impact of various distortions and artifacts introduced in the synthesis process.
  • the enhanced synthesized speech signal is then properly processed in an audio processing unit (111) and rendered audible through an appropriate audio transducer (112).
  • the pitch postfilter (107) serves an important function, in that it provides additional control of the pitch content of the synthesized speech. Without this filter, the resultant synthesized speech product may be rougher and of lower quality. Notwithstanding this important benefit, the pitch postfilter (107) frequently contributes artifacts to the resultant synthesized speech, which artifacts can themselves noticeably disturb the perception of natural speech. Accordingly, a need exists for providing appropriate pitch enhancement filtering in an LPC based speech synthesizing unit that minimizes a concurrent perceptible expression of artifacts in a resultant synthesized speech signal.
  • EP 0294020 describes a vector adaptive coding method for speech and audio, while the article by Holm entitled “Automatic generation of mixed excitation in linear predictive speech synthesizer", and published in International Conference on Acoustics Speech and Signal Processing, vol.1, 30 March 1981, Atlanta, USA, pages 118-120, describes the addition of the fricative excitation model to the LPC synthesis model to improve the quality of speech reproduction.
  • a method of synthesizing speech comprising: A) providing an excitation signal that includes pitch information that has been inserted by a pitch filter; further characterized by the steps of: B) filtering the excitation signal in an adaptive pitch enhancement filter to provide a pitch filtered excitation signal; C) filtering the pitch filtered excitation signal in a LPC speech synthesis filter to provide a synthesized speech signal.
  • a receiving coded information signal may be used to provide the excitation signal.
  • a radio comprising: A) RF means for receiving a broadcast signal and for recovering a coded information signal included therewith; B) excitation source means operably coupled to the RF means for providing an excitation signal that includes pitch information, which pitch information has been inserted by a pitch filter, in response to the coded information signal; wherein the radio is further characterized by: C) adaptive pitch enhancement filter means operably coupled to the excitation source means for filtering the excitation signal to provide a pitch filtered excitation signal; D) LPC filter means for receiving the pitch filtered excitation signal and for providing a synthesized speech signal in response thereto.
  • the pitch enhancement postfilter is moved from a position of processing the LPC filter output to a position where it processes the excitation input to the LPC filter.
  • the subsequent processing of the LPC filter itself functions to minimize the perceptible effect of any artifacts introduced by the pitch enhancement prefilter in the resultant synthesized speech signal.
  • a radio embodying the invention includes an antenna (102) for receiving a speech coded signal (101).
  • An RF unit (103) processes the received signal to recover the speech coded information.
  • This information is provided to a parameter decoder (105) that develops control parameters for various subsequent processes.
  • An excitation source (104) as described above utilizes the parameters provided to it to create an excitation signal.
  • This resultant excitation signal from the excitation source (104) is provided to a pitch prefilter (201) that functions to filter the pitch information contained in the excitation signal.
  • the resultant filtered signal then passes to the LPC filter (106) which yields a synthesized speech signal in accordance with the coded information.
  • this resultant signal is then further processed in an adaptive spectral postfilter (108) and post emphasis filter (109) to further enhance the quality of the synthesized speech, and is then processed in an audio processing unit (111) and rendered audible by an audio transducer (112).

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Multimedia (AREA)
  • Health & Medical Sciences (AREA)
  • Audiology, Speech & Language Pathology (AREA)
  • Human Computer Interaction (AREA)
  • Computational Linguistics (AREA)
  • Acoustics & Sound (AREA)
  • Signal Processing (AREA)
  • Compression, Expansion, Code Conversion, And Decoders (AREA)
  • Noise Elimination (AREA)
  • Stereophonic System (AREA)
  • Filters That Use Time-Delay Elements (AREA)
  • Reduction Or Emphasis Of Bandwidth Of Signals (AREA)
  • Transmission Systems Not Characterized By The Medium Used For Transmission (AREA)

Claims (3)

  1. Verfahren zur Sprachsynthese, umfassend:
    a) Bereitstellung eines Erregersignals, das eine Tonhöheninformation enthält, die durch einen Pitchfilter (Tonhöhenfilter) eingefügt worden ist; weiterhin durch die folgenden Schritte gekennzeichnet:
    b) Filterung des Erregersignals in einem adaptiven Pitchanreicherungsfilter, um ein pitchgefiltertes Erregersignal bereitzustellen;
    c) Filterung des pitchgefilterten Erregersignals in einem LPC-Sprachsynthesefilter, um ein synthetisiertes Sprachsignal bereitzustellen.
  2. Verfahren nach Anspruch 1, das weiterhin den Schritt des Empfangens eines kodierten Informationssignals enthält, und wobei das kodierte Informationssignal genutzt wird, um ein Erregersignal bereitzustellen.
  3. Funkgerät, umfassend:
    (a) Funkfrequenzmittel zum Empfangen eines Rundfunksignals und zur Wiedergewinnung eines darin enthaltenen kodierten Informationssignals;
    (b) Erregerquellenmittel, das betriebsbereit mit dem Funkfrequenzmittel gekoppelt ist, zur Bereitstellung eines Erregersignals, das eine Tonhöheninformation enthält, und diese Tonhöheninformation durch einen Pitchfilter in Reaktion auf das kodierte Informationssignal eingefügt worden ist; und wobei das Funkgerät weiterhin gekennzeichnet ist durch:
    (c) adaptive Pitchanreicherungsfiltermittel, die betriebsbereit mit dem Erregerquellenmittel zur Filterung des Erregersignal verbunden sind, um ein pitchgefiltertes Erregersignal bereitzustellen;
    (d) LPC-Filtermittel zum Empfangen des pitchgefilterten Erregersignals und zur Bereitstellung eines synthetisierten Sprachsignals, in Reaktion darauf.
EP90916987A 1989-10-17 1990-09-17 Auf dem lpc-verfahren beruhende sprachsynthese mit adaptivem pitchvorfilter Expired - Lifetime EP0496829B1 (de)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
US42287189A 1989-10-17 1989-10-17
US422871 1989-10-17
PCT/US1990/005191 WO1991006091A1 (en) 1989-10-17 1990-09-17 Lpc based speech synthesis with adaptive pitch prefilter

Publications (3)

Publication Number Publication Date
EP0496829A1 EP0496829A1 (de) 1992-08-05
EP0496829A4 EP0496829A4 (en) 1993-08-18
EP0496829B1 true EP0496829B1 (de) 2000-12-06

Family

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Family Applications (1)

Application Number Title Priority Date Filing Date
EP90916987A Expired - Lifetime EP0496829B1 (de) 1989-10-17 1990-09-17 Auf dem lpc-verfahren beruhende sprachsynthese mit adaptivem pitchvorfilter

Country Status (6)

Country Link
EP (1) EP0496829B1 (de)
CN (1) CN1051100A (de)
AU (1) AU644119B2 (de)
CA (1) CA2066568A1 (de)
DE (1) DE69033672T2 (de)
WO (1) WO1991006091A1 (de)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP3328080B2 (ja) * 1994-11-22 2002-09-24 沖電気工業株式会社 コード励振線形予測復号器
GB9512284D0 (en) * 1995-06-16 1995-08-16 Nokia Mobile Phones Ltd Speech Synthesiser
DE19629946A1 (de) * 1996-07-25 1998-01-29 Joachim Dipl Ing Mersdorf Ein LPC-basiertes Verfahren zur Analyse und Synthese von Sprachgrundfrequenzverläufen mittels Filterparametrisierung und Restsignalapproximation

Family Cites Families (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4220819A (en) * 1979-03-30 1980-09-02 Bell Telephone Laboratories, Incorporated Residual excited predictive speech coding system
US4969192A (en) * 1987-04-06 1990-11-06 Voicecraft, Inc. Vector adaptive predictive coder for speech and audio

Also Published As

Publication number Publication date
AU6725690A (en) 1991-05-16
CN1051100A (zh) 1991-05-01
DE69033672T2 (de) 2001-05-10
EP0496829A1 (de) 1992-08-05
EP0496829A4 (en) 1993-08-18
AU644119B2 (en) 1993-12-02
CA2066568A1 (en) 1991-04-18
DE69033672D1 (de) 2001-01-11
WO1991006091A1 (en) 1991-05-02

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