Method of and apparatus for performing time-scale modification of speech signals

• US 5,630,013 A
• Filed: 01/25/1994
• Issued: 05/13/1997
• Est. Priority Date: 01/25/1993
• Status: Expired due to Term

• Current Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Original Assignee: Matsushita Electric Industrial Company Limited (Panasonic Holdings Corporation)
• Inventors: Suzuki, Ryoji, Misaki, Masayuki
• Primary Examiner(s): MacDonald, Allen R.
• Assistant Examiner(s): ONKA, THOMAS
• Application Number:
  US08/187,295
• Time in Patent Office: 1,204 Days
• Field of Search: 381/34, 395/2.25
• US Class Current: 704/216
• CPC Class Codes: G10L 21/04 Time compression or expansion

Abstract

An apparatus for transforming an input signal having a time length L into an output signal having a time length αL in accordance with a given time-scale modification ratio α, including a correlator for calculating a value of a correlation function between a first signal and a second signal having a time length T and for determining a time delay T_c at which the value of the correlation function becomes the greatest; an adder for adding the first signal multiplied by a first window function to the second signal multiplied by a second window function with a displacement of the time delay T_c ; and an outputting circuit for selectively outputting the output of the adder and a third signal succeeding the output of the adder so that the sum of a time length of the output of the adder and a time length of the third signal is substantially equal to a time length defined by the time-scale modification ratio α, the time delay T_c and the time length T.

Claims

1. An apparatus for transforming an input signal having a time length L into an output signal having a time length L in accordance with a given time-scale modification ratio α

, said apparatus comprising;

input means for inputting a first signal which has a time length T and a second signal which has said time length T and succeeds said first signal;

correlating means for calculating a value of a correlation function between said first signal and said second signal and for determining a time delay T_c at which said value of said correlation function becomes the greatest;

window function generating means for generating a first window function and a second window function according to said time-scale modification ratio α and

said time delay T_c ;

first multiplying means for multiplying said first signal by said first window function;

second multiplying means for multiplying said second signal by said second window function;

adding means for adding the output of said first multiplying means to the output of said second multiplying means with a displacement of said time delay T_c ; and

outputting means for selectively outputting the output of said adding means and a third signal succeeding said output of said adding means so that the sum of a time length of said output of said adding means and a time length of said third signal is substantially equal to a time length defined by α

(T-T_c)/(α

-1) or α

(T-T_c)/(1-α

).

2. A method for transforming an input signal having a time length L into an output signal having a time length α

L in accordance with a given time-scale modification ratio α

, said method comprising the steps of;

(a) inputting a first signal which has a time length T from a starting point and a second signal which has said time length T and succeeds said first signal;

(b) calculating a value of a correlation function between said first signal and said second signal and determining a time delay T_c at which said value of said correlation function becomes the greatest;

(c) generating a first window function and a second window function according to said time-scale modification ratio α and

said time delay T_c ;

(d) obtaining a first multiplied result by multiplying said first signal by said first window function;

(e) obtaining a second multiplied result by multiplying said second signal by said second window function;

(f) obtaining an added result by adding said first multiplied result to said second multiplied result with a displacement of said time delay T_c ;

(g) selectively outputting said added result and a third signal succeeding said added result so that the sum of a time length of said added result and a time length of said third signal is substantially equal to a predetermined first time length defined by α

(T-T_c)/(α

-1) or α

(T-T_c)/(1-α

);

(h) adding a predetermined second time length defined by said time-scale modification ratio α

, said time delay T_c and said time length T to said starting point of said first signal; and

(i) repeating said step (a) to said step (h).

3. A method according to claim 2, wherein said time-scale modification ratio α

satisfies a condition of α

≧

1, said first window function monotonically increases and said second window function monotonically decreases in a manner complementary to said first window function, said predetermined first time length is represented by α

(T-T_c)/(α

-1), said third signal is a signal exceeding said first signal, said predetermined second time length is represented by (T-T_c)/(α

-1).

4. A method according to claim 2, wherein said time-scale modification ratio α

satisfies a condition of α

≦

1, said first window function monotonically decreases and said second window function monotonically increases in a manner complementary to said first window function, said predetermined first time length is represented by an equation of α

(T-T_c)/(1-α

), said third signal is a signal exceeding said second signal, said predetermined second time length is represented by an equation of (T-T_c)/(1-α

).

5. An apparatus for transforming an input signal having a time length L into an output signal having a time length α

L in accordance with a given time-scale modification ratio α

, said apparatus comprising;

input means for inputting a first signal which has a time length M (T≦

M<

2T) and a second signal which has said time length M, a starting point of said second signal being delayed from a starting point of said first signal by a time length T;

correlating means for calculating a value of a correlation function between said first signal and said second signal and for determining a time delay T_c at which said value of said correlation function becomes the greatest;

window function generating means for generating a first window function and a second window function according to said time-scale modification ratio α and

said time delay T_c ;

reading means for reading a portion of said first signal and a portion of said second signal according to said time delay T_c ;

first multiplying means for multiplying said portion of said first signal by said first window function;

second multiplying means for multiplying said portion of said second signal by said second window function;

adding means for adding the output of said first multiplying means to the output of said second multiplying means with a displacement of said time delay T_c and with an overlap of said time length T; and

outputting means for selectively outputting the output of said adding means and a third signal succeeding said output of said adding means so that the sum of a time length of said output of said adding means and a time length of said third signal is substantially equal to a time length defined by said time-scale modification ratio α

, said time delay T_c and said time length T.

6. A method for transforming an input signal having a time length L into an output signal having a time length α

L in accordance with a given time-scale modification ratio α

which satisfies a condition of α

≧

1, said method comprising the steps of;

(a) inputting a first signal which has a time length T from a starting point and a second signal which has said time length T and succeeds said first signal;

(b) calculating a value of a correlation function between said first signal and said second signal and determining a time delay T_c at which said value of said correlation function becomes the greatest;

(c) obtaining a third signal which has said time length T and delays from said first signal by said time delay T_c and a fourth signal which has said time length T and delays from said second signal by said time delay (-T_c);

(d) generating a first window function which monotonically increases and a second window function which monotonically decreases in a manner complementary to said first window function according to said time-scale modification ratio α and

said time delay T_c ;

(e) performing a first output step, when said time delay T_c satisfies a condition of T_c <

0, said first step including the steps of;

(e1) obtaining a fifth signal which has said time length (-T_c) from a start point of said second signal;

(e2) obtaining a first multiplied result by multiplying said first signal by said first window function;

(e3) obtaining a second multiplied result by multiplying said fourth signal by said second window function;

(e4) obtaining an added result by adding said first multiplied result to said second multiplied result; and

(e5) selectively outputting said fifth signal, said added result and a sixth signal succeeding said first signal so that the sum of a time length of said fifth signal, a time length of said added result and a time length of said sixth signal is substantially equal to a predetermined first time length defined by said time-scale modification ratio α

, said time delay T_c and said time length T;

(f) performing a second output step, when said time delay T_c satisfies a condition of T_c ≧

0, said second step including the steps of;

(f1) obtaining a first multiplied result by multiplying said third signal by said first window function;

(f2) obtaining a second multiplied result by multiplying said second signal by said second window function;

(f3) obtaining an added result by adding said first multiplied result to said second multiplied result; and

(f4) selectively outputting said added result and a seventh signal succeeding said third signal so that the sum of a time length of said added result and a time length of said seventh signal is substantially equal to a predetermined first time length defined by said time-scale modification ratio α

, said time delay T_c and said time length T;

(g) adding a predetermined second time length defined by said time-scale modification ratio α

, said time delay T_c and said time length T to said starting point of said first signal; and

(h) repeating said step (a) to said step (g).

7. A method according to claim 6, wherein said predetermined first time length is represented by an equation of α

(T-T_c)/(α

-1) and said predetermined second time length is represented by an equation of (T-T_c)/(α

-1).

8. A method according to claim 6, wherein said step (b) includes the steps of:

calculating a value of a correlation function between said first signal and a signal which has said time length T and delays from said second signal by (-τ

) for -T<

τ

<

0;

calculating a value of said correlation function between said second signal and a signal which has said time length T and delays from said first signal by τ

for 0≦

τ

<

T;

determining a time delay T_c at which said value of said correlation function becomes the greatest for -T<

τ

<

T.

9. A method according to claim 8, wherein said correlation function is defined by:

##EQU7## for -T<

τ

<

0; and

##EQU8## for 0≦

τ

<

T;

where, ip1 denotes a starting point of said first signal and ip2 denotes a stating point of said second signal.

10. A method for transforming an input signal having a time length L into an output signal having a time length α

L in accordance with a given time-scale modification ratio α

which satisfies a condition of α

≦

1, said method comprising the steps of;

(a) inputting a first signal which has a time length T from a starting point and a second signal which has said time length T and succeeds said first signal;

(b) calculating a value of a correlation function between said first signal and said second signal and determining a time delay T_c at which said value of said correlation function becomes the greatest;

(c) obtaining a third signal which has said time length T and delays from said first signal by said time delay T_c and a fourth signal which has said time length T and delays from said second signal by said time delay (-T_c);

(d) generating a first window function which monotonically decreases and a second window function which monotonically increases in a manner complementary to said first window function according to said time-scale modification ratio α and

said time delay T_c ;

(e) performing a first output step, when said time delay T_c satisfies a condition of T_c >

0, said first step including the steps of;

(e1) obtaining a fifth signal which has said time length T_c from a start point of said first signal;

(e2) obtaining a first multiplied result by multiplying said third signal by said first window function;

(e3) obtaining a second multiplied result by multiplying said second signal by said second window function;

(e4) obtaining an added result by adding said first multiplied result to said second multiplied result; and

(e5) selectively outputting said fifth signal, said added result and a sixth signal succeeding said second signal so that the sum of a time length of said fifth signal, a time length of said added result and a time length of said sixth signal is substantially equal to a predetermined first time length defined by said time-scale modification ratio α

, said time delay T_c and said time length T;

(f) performing a second output step, when said time delay T_c satisfies a condition of T_c ≦

0, said second step including the steps of;

(f1) obtaining a first multiplied result by multiplying said first signal by said first window function;

(f2) obtaining a second multiplied result by multiplying said fourth signal by said second window function;

(f3) obtaining an added result by adding said first multiplied result to said second multiplied result; and

(f4) selectively outputting said added result and a seventh signal succeeding said fourth signal so that the sum of a time length of said added result and a time length of said seventh signal is substantially equal to a predetermined first time length defined by said time-scale modification ratio α

, said time delay T_c and said time length T;

(g) adding a predetermined second time length defined by said time-scale modification ratio α

, said time delay T_c and said time length T to said starting point of said first signal; and

(h) repeating said step (a) to said step (g).

11. A method according to claim 10, wherein said predetermined first time length is represented by an equation of α

(T-T_c)/(1-α

) and said predetermined second time length is represented by an equation of (T-T_c)/(1-α

).

12. A method according to claim 10, wherein said step (b) includes the steps of:

calculating a value of a correlation function between said first signal and a signal which has said time length T and delays from said second signal by (-τ

) for -T<

τ

<

0;

calculating a value of said correlation function between said second signal and a signal which has said time length T and delays from said first signal by τ

for 0≦

τ

<

T;

determining a time delay T_c at which said value of said correlation function becomes the greatest for -T<

τ

<

T.

13. A method according to claim 12, wherein said correlation function is defined by:

##EQU9## for -T<

τ

<

0; and

##EQU10## for 0≦

τ

<

T;

where, ip1 denotes a starting point of said first signal and ip2 denotes a stating point of said second signal.