Speech synthesis method, speech synthesis system, and speech synthesis program

• US 7,668,717 B2
• Filed: 11/26/2004
• Issued: 02/23/2010
• Est. Priority Date: 11/28/2003
• Status: Expired due to Fees

• Current Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Original Assignee: Kabushiki Kaisha Toshiba (Toshiba Corporation)
• Inventors: Kagoshima, Takehiko, Mizutani, Tatsuya
• Primary Examiner(s): Vo; Huyen X.
• Application Number:
  US10/996,401
• Publication Number:
  US 20050137870A1
• Time in Patent Office: 1,915 Days
• Field of Search: 704/200, 704258-269, 704/270, 704/270.1, 704/243, 704/236
• US Class Current: 704/261
• CPC Class Codes: G10L 13/04 Details of speech synthesis systems, e.g. synthesiser structure or memory management
• CPC Class Codes: G10L 13/06 Elementary speech units used in speech synthesisers; Concatenation rules

Abstract

A speech synthesis system stores a group of speech units in a memory, selects a plurality of speech units from the group based on prosodic information of target speech, the speech units selected corresponding to each of segments which are obtained by segmenting a phoneme string of the target speech and minimizing distortion of synthetic speech generated from the speech units selected to the target speech, generates a new speech unit corresponding to the each of the segments, by fusing the speech units selected, to obtain a plurality of new speech units corresponding to the segments respectively, and generates synthetic speech by concatenating the new speech units.

Claims

1. A speech synthesis method, comprising:

storing a group of speech units and prosodic information corresponding to each of the speech units of the group in a memory;

segmenting a phoneme string of a target speech to obtain a plurality of segments;

selecting, from the group in the memory, a speech unit for each of the segments based on prosodic information of the target speech to obtain an optimal speech unit sequence including speech units selected for the respective segments;

selecting M (M represents a positive integer greater than one) speech units for each of the segments from the group in the memory, based on the optimal speech unit sequence; and

generating a new speech unit corresponding to each of the segments, by fusing the M speech units selected for each of the segments, to obtain a plurality of new speech units corresponding to the segments respectively;

wherein the selecting the M speech units for each of the segments includes;

setting each of the segments as a target segment;

calculating a first cost for each speech unit of the group in the memory, the first cost representing a difference between the target segment in the target speech and the speech unit of the group;

calculating a second cost for each speech unit of the group in the memory, the second cost representing a degree of distortion produced when the speech unit of the group is concatenated with speech units before and after the target segment in the optimal speech unit sequence; and

selecting the M speech units for the target segment based on the first cost and the second cost of each speech unit of the group.

2. A method according to claim 1, wherein the prosodic information includes at least one of fundamental frequency, duration, and power.

3. A method according to claim 1, wherein generating the new speech unit includes generating M pitch-cycle waveform sequences each including the same numbers of pitch-cycle waveforms, from M pitch-cycle waveform sequences corresponding to the M speech units selected respectively;

and

generating the new speech unit by fusing the M pitch-cycle waveform sequences generated.

4. A method according to claim 3, wherein the new speech unit is generated by calculating a centroid of each pitch-cycle waveform of the new speech unit.

5. A speech synthesis system comprising:

a memory to store a group of speech units and prosodic information corresponding to each of the speech units of the group;

a first selecting unit configured to select, from the group in the memory, a speech unit for each of segments which are obtained by segmenting a phoneme string of a target speech, based on prosodic information of the target speech, to obtain an optimal speech unit sequence including speech units selected for the respective segments;

a second selecting unit configured to select, based on the optimal speech unit sequence, M (M represents a positive integer greater than one) speech units for each segment of the segments from the group in the memory; and

a generating unit configured to generate a new speech unit corresponding to each of the segments, by fusing the M speech units selected for the segment, to obtain a plurality of new speech units corresponding to the segments respectively;

wherein the second selecting unit is configured to;

set each segment of the segments as a target segment;

calculate a first cost for each speech unit of the group in the memory, the first cost representing a difference between the target segment in the target speech and the speech unit of the group;

calculate a second cost for each speech unit of the group in the memory, the second cost representing a degree of distortion produced when the speech unit of the group is concatenated with speech units before and after the target segment in the optimal speech unit sequence; and

select the M speech units for the target segment based on the first cost and the second cost of each speech unit of the group.