EP0360265A2
Expired / Lapsed
EP
⏱️ 0.0 years remaining
Communication system capable of improving a speech quality by classifying speech signals
Assignee: NEC Corp
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Filing: 1989-09-21
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Granted: —
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Expires: 2009-09-21
Abstract
Abstract In an encoder device which is for use in combination with a decoder device in a communication system and which encodes a sequence of digital speech signals into a sequence of output signals by the use of a spectrum parameter and a pitch parameter, a subsidiary parameter of the digital speech signals is detected and by a monitoring circuit to classify the digital speech signals into a voiced sound and a voiceless sound or into vocality, nasal, fricative, and explosive at every frame. On detection of the voiced sound or the vocality, a predetermined number of excitation pulses are calculated only during a representative subframe after dividing each frame into a plurality of subframes by the use of the pitch parameter and are produced as primary sound source signals together with a subsidiary information signal which is produced during the remaining subframes and which may be representative of a correction factor of an amplitude and a phase in each of the subframes. On detection of the voiceless sound or the nasal, the fricative, and the explosive, noise signals and/or a plurality of excitation pulses are calculated for each frame and produced as secondary sound source signals. Alternatively, the subsidiary parameter may represent periodicity of an impulse response of a synthesizing filter formed by the spectrum parameter.
Inventors
- 👤 Kazunori Ozawa
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-10-29 04:59
CPC Classifications
G; G10; G10L; G10L19/00; G10L19/04
Claims Analysis
Total Claims: 11
Claim 1
Independent Claim
345 words
In an encoder device supplied with a sequence of digital speech signals at every frame to produce a sequence of output signals, said encoder device comprising parameter calculation means responsive to said digital speech signals for calculating first and second primary parameters which specify a spectrum envelope and a pitch of the digital speech signals at every frame to produce first and second parameter signals representative of said spectrum envelope and said pitch, respectively, primary calculation means coupled to said parameter calculation means for calculating a set of calculation result signals representative of said digital speech signals, and output signals producing means for producing said set of the calculation result signals as said output signal sequence, the improvement wherein said encoder device comprises: subsidiary parameter monitoring means operable in cooperation with said parameter calculation means for monitoring a subsidiary parameter which is different from said first and said second primary parameters to specify said digital speech signals at every frame, said subsidiary monitoring means thereby producing a monitoring result signal representative of a result of monitoring said subsidiary parameter; said primary calculation means comprising: processing means supplied with said digital speech signals, said first and said second primary parameter signals, and said monitoring result signal for processing said digital speech signals to selectively produce a first set of primary sound source signals and a second set of secondary sound source signals different from said first set of the primary sound source signals, said first set of the primary sound source signals being formed by as set of excitation pulses calculated with respect to a selected one of subframes which result from dividing every frame in dependency upon said second primary parameter signal and each of which is shorter than said frame and a subsidiary information signal calculated with respect to the remaining subframes except said selected one of the subframes on production of said set of the excitation pulses; and means for supplying a combination of said primary and said secondary sound source signals to said output signal producing means as said calculation result signals.
Claim 2
Dependent Claim
345 words
In an encoder device supplied with a sequence of digital speech signals at every frame to produce a sequence of output signals, said encoder device comprising parameter calculation means responsive to said digital speech signals for calculating first and second primary parameters which specify a spectrum envelope and a pitch of the digital speech signals at every frame to produce first and second parameter signals representative of said spectrum envelope and said pitch, respectively, primary calculation means coupled to said parameter calculation means for calculating a set of calculation result signals representative of said digital speech signals, and output signals producing means for producing said set of the calculation result signals as said output signal sequence, the improvement wherein said encoder device comprises: subsidiary parameter monitoring means operable in cooperation with said parameter calculation means for monitoring a subsidiary parameter which is different from said first and said second primary parameters to specify said digital speech signals at every frame, said subsidiary monitoring means thereby producing a monitoring result signal representative of a result of monitoring said subsidiary parameter; said primary calculation means comprising: processing means supplied with said digital speech signals, said first and said second primary parameter signals, and said monitoring result signal for processing said digital speech signals to selectively produce a first set of primary sound source signals and a second set of secondary sound source signals different from said first set of the primary sound source signals, said first set of the primary sound source signals being formed by as set of excitation pulses calculated with respect to a selected one of subframes which result from dividing every frame in dependency upon said second primary parameter signal and each of which is shorter than said frame and a subsidiary information signal calculated with respect to the remaining subframes except said selected one of the subframes on production of said set of the excitation pulses; and means for supplying a combination of said primary and said secondary sound source signals to said output signal producing means as said calculation result signals.
Claim 3
Dependent Claim
94 words
An encoder device as claimed in Claim 1, said subsidiary parameter being representative of species of the digital speech signals, wherein said subsidiary parameter monitoring means comprises: classifying means supplied with said digital speech signals for classifying said subsidiary parameter into a plurality of classes determined for the respective species of the digital speech signals to produce a class identification signal representative of said classes after extraction of said subsidiary parameter from said digital speech signals; and means for supplying said class identification signal to said primary calculation means as said monitoring result signal.
Claim 4
Dependent Claim
60 words
An encoder device as claimed in Claim 2, the species of said digital speech signals being classified into vocality, nasal, fricative, and explosive, wherein said processing means selectively produces the first set of the primary sound source signals when the monitoring result signal is representative of said vocality and, otherwise, to produce the second set of the sound source signals.
Claim 5
Dependent Claim
84 words
An encoder device as claimed in Claim 3, wherein said processing means comprises: excitation pulse producing means supplied with said digital speech signals at every frame for producing said set of the excitation pulses during said selected one of the subframes when said monitoring result signal is representative of said vocality; and subsidiary information producing means for producing, during the remaining subframes, said subsidiary information signal which is for adjusting at least one of an amplitude and a phase of said primary excitation pulses.
Claim 6
Dependent Claim
167 words
An encoder device as claimed in any one of Claims 1 to 4, wherein said subsidiary parameter monitoring means monitors, as said subsidiary parameter, periodicity of an impulse response of a synthesizing filter determined by said first primary parameter to decide whether or not the periodicity of the impulse response is higher than a predetermined threshold level and comprises: threshold means for producing said predetermined threshold level; periodicity detecting means coupled to said parameter calculation means and said threshold means and supplied with said first primary parameter for detecting whether or not said periodicity of the impulse response is higher than said predetermined threshold level to produce a periodicity signal when said periodicity is higher than said predetermined threshold level; and means for supplying said periodicity signal to said parameter calculation means as said monitoring result signal to weight said first primary parameter on the basis of said periodicity signal and to make said parameter calculation means produce the first primary parameter weighted by said periodicity signal.
Claim 7
Dependent Claim
219 words
A decoder device communicable with the encoder device claimed in any one of Claims 1 to 5 produce a sequence of synthesized speech signals, said decoder device being supplied with said output signal sequence as a sequence of reception signals which carries said first set of the primary sound source signals, said second set of the secondary sound source signals, said first and said second primary parameters, and said subsidiary parameter, said decoder device comprising: demultiplexing means supplied with said reception signal sequence for demultiplexing said reception signal sequence into the primary and the secondary sound source signals, the first and the second primary parameters, and the subsidiary parameter as primary and secondary sound source codes, first and second parameter codes, and a subsidiary parameter code, respectively, said primary sound source codes conveying said set of the excitation pulses and said subsidiary information signal which are demultiplexed into excitation pulse codes and a subsidiary information code, respectively; reproducing means coupled to said demultiplexing means for reproducing said primary and said secondary sound source codes into a sequence of driving sound source signals by using said subsidiary information signal, said first and said second parameter codes, and said subsidiary parameter code; and means coupled to said reproducing means for synthesizing said driving sound source signals into said synthesized speech signals.
Claim 8
Dependent Claim
154 words
A decoder device as claimed in Claim 6, wherein said reproducing means comprises: first decoding mens supplied with said primary and said secondary sound source codes and said subsidiary parameter code for decoding said primary and said secondary sound source codes into primary and secondary decoded sound sourace signals, respectively; second decoding means supplied with said subsidiary information code from said demultiplexing means for decoding said subsidiary information code into a decoded subsidiary code; third decoding means supplied with said first and said second parameter codes from said demultiplexing means for decoding said first and said second parameter codes into and second decoded parameter codes, respectively; means coupled to said first through said third decoding means for reproducing said primary and said secondary decoded sound source signals into said driving sound source signals by the use of said decoded subsidiary code, said first and said second decoded parameter codes, and said subsidiary parameter code.
Claim 9
Dependent Claim
294 words
In a encoder device supplied with a sequence of digital speech signals at every frame to produce a sequence of output signals, said encoder device comprising parameter calculation means responsive to said digital speech signals for calculating first and second primary parameters which specify a spectrum envelope and. a pitch of the digital speech signals at every frame to produce first and second parameter signals representative of said spectrum envelope and said pitch, respectively, primary calculation means coupled to said parameter calculation means for calculating a set of calculation result signals representative of said digital speech signals, and output signal producing means for producing said set of the calculation result signals as said output signal sequence, said digital speech signals being classifying a voiced sound and a voiceless sound, the improvement wherein said primary calculation means comprises: processing means supplied with said digital speech signals and said first and said second primary parameters for processing said digital speech signals to selectively produce a first set of primary sound source signals and a second set of secondary sound source signals during said voiced sound and said voiceless sound, respectively, said first set of the primary sound source signals being formed by as set of excitation pulses calculated with respect to a selected one of subframes which result from dividing every frame in dependency upon said second primary parameter signal and each of which is shorter than said frame and a subsidiary information signal calculated with respect to the remaining subframes except said selected one of the subframes on production of said set of the excitation pulses; and means for supplying a combination of said first and said second sets of the sound source signals to said output signal producing means as said calculation result signals.
Claim 10
Dependent Claim
294 words
In a encoder device supplied with a sequence of digital speech signals at every frame to produce a sequence of output signals, said encoder device comprising parameter calculation means responsive to said digital speech signals for calculating first and second primary parameters which specify a spectrum envelope and. a pitch of the digital speech signals at every frame to produce first and second parameter signals representative of said spectrum envelope and said pitch, respectively, primary calculation means coupled to said parameter calculation means for calculating a set of calculation result signals representative of said digital speech signals, and output signal producing means for producing said set of the calculation result signals as said output signal sequence, said digital speech signals being classifying a voiced sound and a voiceless sound, the improvement wherein said primary calculation means comprises: processing means supplied with said digital speech signals and said first and said second primary parameters for processing said digital speech signals to selectively produce a first set of primary sound source signals and a second set of secondary sound source signals during said voiced sound and said voiceless sound, respectively, said first set of the primary sound source signals being formed by as set of excitation pulses calculated with respect to a selected one of subframes which result from dividing every frame in dependency upon said second primary parameter signal and each of which is shorter than said frame and a subsidiary information signal calculated with respect to the remaining subframes except said selected one of the subframes on production of said set of the excitation pulses; and means for supplying a combination of said first and said second sets of the sound source signals to said output signal producing means as said calculation result signals.
Claim 11
Dependent Claim
204 words
A decoder device communicable with the encoder device claimed in Claim 8 to produce a sequence of synthesized speech signals, said decoder device being supplied with said output signal sequence as a sequence of reception signals which carries said first set of the primary sound source signals, said second set of the secondary sound source signals, said first and said second primary parameters, said decoder device comprising: demultiplexing means supplied with said reception signal sequence for demultiplexing said reception signal sequence into the primary and the secondary sound source signals and the first and the second primary parameters as primary and secondary sound source codes and first and second parameter codes, respectively, said primary sound source codes conveying said set of the excitation pulses and said subsidiary information signal which are demultiplexed into excitation pulse codes and a subsidiary information code by said demultiplexing means, respectively; reproducing means coupled to said demultiplexing means for reproducing said primary and said secondary sound source codes into a sequence of driving sound source signals by using said first and said second parameter codes, and said subsidiary information code; and means coupled to said reproducing means for synthesizing said driving sound source signals into said synthesized speech signals.
References Cited (Backward Citations)
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