Sound reproducing speed converter

Details Sound reproducing speed converter Sound reproducing speed converter

1998-07-01

2000-09-05

Dorvil, Richemond

Data processing: speech signal processing, linguistics, language

Speech signal processing

Synthesis

704262, G10L 1302

Patent

active

061156876

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

The present invention relates to an apparatus for converting a voice reproducing rate to reproduce digitized voice signals at an arbitrary rate without transforming (changing) a pitch of voice.
In this specification(description), "voice" and "voice signal" are used to represent all acoustic signals generated from instruments and others, not only voice uttered from a person.


BACKGROUND ART

As a method to convert a reproducing rate into an arbitrary rate without transforming a pitch of voice, PICOLA (Pointer Interval Control Overlap and Add) method is known. The principle of PICOLA method is introduced by "Time-Scale Modification Algorithm for Speech by Use of Pointer Interval Control Overlap and Add (PICOLA) and Its Evaluation" written by MORITA, Naotaka and ITAKURA, Fumitada in Proceeding of National Meeting of The Acoustic Society of Japan 1-4-14 (October, 1986).
And, the application of PICOLA method for voice signals divided into frames to convert a reproducing rate with fewer buffer memories is disclosed in Japanese unexamined patent publication No.8-137491.
FIG. 9 illustrates a block diagram of a conventional apparatus for converting a voice reproducing rate in PICOLA method. In the apparatus for converting a voice reproducing rate illustrated in FIG. 9, digitized voice signals are recorded in recording media 1, and framing section 2 fetches a voice signal in a frame of a predetermined length LF sample from recording media 1. The voice signal fetched by framing section 2 is provided into pitch period calculating section 6 along with stored in buffer memory 3 temporarily. Pitch period calculating section 6 calculates pitch period Tp of the voice signal to provide it into waveform overlapping section 4 along with storing a pointer of processing start position into buffer memory 3. Waveform overlapping section 4 overlaps waveforms of voice signals stored in buffer memory 3 using the pitch period of the input voice, then outputs the overlapped waveform into waveform synthesizing section 5. Waveform synthesizing section 5 synthesizes an output voice signal waveform from the voice signal waveform stored in buffer memory 3 and the overlapped waveform processed at waveform overlapping section 4 to provide the output voice.
In this apparatus for converting a voice reproducing rate, a reproducing rate is converted without transforming a pitch according to the process in the following.
First, a processing method for high rate reproducing is explained with FIG. 10 and FIG. 11. In the figures, P0 is a pointer indicating a head of a waveform overlap processing frame. In the waveform overlap processing, a processing frame is a LW sample with a length of two periods of voice pitch period Tp. And, when a rate of input voice is 1 and a desired reproducing rate is given r, L is the number of samples given by the following formulation. input voice of Tp+L sample is reproduced as an output voice of L sample as mentioned later. Accordingly, r=(Tp+L)/L is given, then the formulation (1) is introduced.
An input voice fetched from recording media 1 by framing section 2 is stored in buffer memory 3. Concurrently, pitch period calculating section 6 calculates pitch period Tp of the input voice to input it to waveform overlapping section 4. And, pitch period calculating section 6 calculates L from pitch period Tp using the formulation (1), determines P0' that is a starting position for next processing and provides it into buffer memory 3 as a pointer in the buffer memory.
Waveform overlapping section 4 fetches a waveform of waveform overlap processing frame LW (=2Tp) sample from a processing starting point indicated by pointer P0 from buffer memory 3, decreases the first part of the processing frame (waveform A) in the time axis direction and increases the latter part of the processing frame (waveform B) in the time axis direction according to the the triangle window function, adds waveform A and waveform B, then calculates overlapped waveform c.
Waveform synthesizing section 5 removes the waveform of the wave

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An article by Morita et al., entitled "Time-Scale Modification Algorithm For Speech By Use of Pointer Interval Control Overlap and Add (PICOLA) and its Evaluation", Proceeding of National Meeting of the Acoustic Society of Japan, 1-4-14, Oct. 1986.
An English Language abstract of Morita et al. article.
An English Language abstract of JP 7-077999.
An English Language abstract of JP 1-267700.
An English Language abstract of JP 9-152889.
An English Language abstract of JP 8-137491.
An English Language abstract of JP 8-202397.
An English Language abstract of JP8-022300.
An English Language abstract of JP 7-319496.

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