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

A method for transforming an input signal having a time length L into an output signal having a time length .alpha.L in accordance with a given time-scale modification ratio .alpha., 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.sub.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 .alpha. and said time delay T.sub.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.sub.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 .alpha.(T-T.sub.c)/(.alpha.-1) or .alpha.(T-T.sub.c)/(1-.alpha.);
• (h) adding a predetermined second time length defined by said time-scale modification ratio .alpha., said time delay T.sub.c and said time length T to said starting point of said first signal;
• and
• (i) repeating said step (a) to said step (h).

An apparatus for transforming an input signal having a time length L into an output signal having a time length .alpha.L in accordance with a given time-scale modification ratio .alpha., said apparatus comprising:

• input means for inputting a first signal which has a time length M (T.ltoreq.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.sub.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 .alpha. and said time delay T.sub.c ;
• reading means for reading a portion of said first signal and a portion of said second signal according to said time delay T.sub.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.sub.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 .alpha., said time delay T.sub.c and said time length T.

A method for transforming an input signal having a time length L into an output signal having a time length .alpha.L in accordance with a given time-scale modification ratio .alpha. which satisfies a condition of .alpha..gtoreq.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.sub.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.sub.c and a fourth signal which has said time length T and delays from said second signal by said time delay (-T.sub.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 .alpha. and said time delay T.sub.c ;
• (e) performing a first output step, when said time delay T.sub.c satisfies a condition of T.sub.c <0, said first step including the steps of:
• (e1) obtaining a fifth signal which has said time length (-T.sub.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 .alpha., said time delay T.sub.c and said time length T;
• (f) performing a second output step, when said time delay T.sub.c satisfies a condition of T.sub.c .gtoreq.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 .alpha., said time delay T.sub.c and said time length T;
• (g) adding a predetermined second time length defined by said time-scale modification ratio .alpha., said time delay T.sub.c and said time length T to said starting point of said first signal;
• and
• (h) repeating said step (a) to said step (g).

A method for transforming an input signal having a time length L into an output signal having a time length .alpha.L in accordance with a given time-scale modification ratio .alpha. which satisfies a condition of .alpha..ltoreq.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.sub.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.sub.c and a fourth signal which has said time length T and delays from said second signal by said time delay (-T.sub.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 .alpha. and said time delay T.sub.c ;
• (e) performing a first output step, when said time delay T.sub.c satisfies a condition of T.sub.c >0, said first step including the steps of:
• (e1) obtaining a fifth signal which has said time length T.sub.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 .alpha., said time delay T.sub.c and said time length T;
• (f) performing a second output step, when said time delay T.sub.c satisfies a condition of T.sub.c .ltoreq.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 .alpha., said time delay T.sub.c and said time length T;
• (g) adding a predetermined second time length defined by said time-scale modification ratio .alpha., said time delay T.sub.c and said time length T to said starting point of said first signal;
• and
• (h) repeating said step (a) to said step (g).