Apparatus and method for creating pitch wave signals and apparatus and method compressing, expanding and synthesizing speech signals using these pitch wave signals

• US 20070174056A1
• Filed: 03/09/2007
• Published: 07/26/2007
• Est. Priority Date: 08/31/2001
• Status: Active Grant

• Current Assignee: Rakuten Group, Inc.
• Original Assignee: Kabushiki Kaisha Kenwood (JVC Kenwood Corporation)
• Inventors: Sato, Yasushi
• Granted Patent: US 7,647,226 B2
• Time in Patent Office: Days
• US Class Current: 704/260
• CPC Class Codes: G10L 13/08 Text analysis or generation of parameters for speech synthesis out of text, e.g. grapheme to phoneme translation, prosody generation or stress or intonation determination
• CPC Class Codes: G10L 19/09 Long term prediction, i.e. removing periodical redundancies, e.g. by using adaptive codebook or pitch predictor
• CPC Class Codes: G10L 21/003 Changing voice quality, e.g. pitch or formants
• CPC Class Codes: G10L 21/013 Adapting to target pitch
• CPC Class Codes: G10L 21/04 Time compression or expansion

Abstract

A pitch wave signal creation method as a preliminary process for efficiently coding a speech wave signal having a fluctuated pitch period is provided. A speech signal compressing/expanding apparatus and a speech signal synthesizing apparatus using the method, and a signal processing associated therewith are further provided. The pitch wave creation method of the invention is essentially comprised of a method of detecting the instantaneous pitch period of each pitch wave element of the speech wave signal, and a process of converting a corresponding pitch wave element into a normalized pitch wave element having a predetermined fixed time length by expanding and compressing the pitch wave element on a time axis while retaining its wave pattern based on the each detected instantaneous pitch period. The speech signal having a pitch fluctuation can be compressed in high quality and high efficiency by coding or synthesizing the speech wave signal using the pitch wave signal creation method of the invention.

Claims

1. A speech synthesizing apparatus, the apparatus comprising:

storage means for storing rhythm information representing the rhythm of a sample of unit speech sound, pitch information representing the pitch of the sample, and spectrum information showing variation with time in the fundamental frequency component and harmonic wave component of a pitch wave signal created by making substantially identical the time lengths of sections each equivalent to the unit pitch of a speech signal. representing the wave of the sample with such information brought into correspondence with the sample;

prediction means for inputting text information representing a text, and creating prediction information representing the result of predicting the pitch and spectrum of a unit speech sound constituting the text based on the text information;

retrieval means for identifying a sample having a pitch and spectrum having the highest correlation with the pitch and spectrum of the unit speech sound constituting the text based on the pitch information, spectrum information and prediction information; and

signal synthesizing means for creating a synthesized speech signal representing a speech sound in which the speech sound has a rhythm represented by the rhythm information brought into correspondence with the sample identified by the retrieval means, the variation with time in the fundamental frequency component and harmonic wave component is represented by the spectrum information brought into correspondence with the sample identified by the retrieval means, and the time length of the section equivalent to the unit pitch is a time length represented by the pitch information brought into correspondence with the sample identified by the retrieval means.

2. The speech synthesizing apparatus according to claim 1, wherein the spectrum information is constituted by data representing the result of nonlinearly quantizing the volume representing variation with time in the fundamental frequency component and harmonic wave component of the pitch wave signal.

3. A speech synthesis method, wherein rhythm information representing the rhythm of a sample of unit speech sound, pitch information representing the pitch of the sample, and spectrum information showing variation with time in the fundamental frequency component and harmonic wave component of a pitch wave signal created by making substantially identical the time lengths of sections each equivalent to the unit pitch of a speech signal representing the wave of the sample are stored with such information brought into correspondence with the sample;

text information representing a text is inputted, and prediction information representing the result of predicting the pitch and spectrum of a unit speech sound constituting the text is created based on the text information;

a sample having a pitch and spectrum having the highest correlation with the pitch and spectrum of the unit speech sound constituting the text is identified based on the pitch information, spectrum information and prediction information; and

a synthesized speech signal representing a speech sound in which the speech sound has a rhythm represented by the rhythm information brought into correspondence with the identified sample, the variation with time in the fundamental frequency component and harmonic wave component is represented by the spectrum information brought into correspondence with the sample identified by the retrieval means, and the time length of the section equivalent to the unit pitch is a time length represented by the pitch information brought into correspondence with the sample identified by the retrieval means is created.