Method and system for an overlap-add technique for predictive decoding based on extrapolation of speech and ringinig waveform

1. A method of extrapolating a waveform based upon synthesizing a corrupted frame output from a decoder including one or more predictive filters, the corrupted frame being representative of one segment of a decoded signal, the method comprising:

copying a first number (L) of (N f ) stored samples of the decoded signal (s(q)) in accordance with a time lag (ppfe) and a scaling factor (ptfe);

calculating a first number (L) of ringing samples (r(n)) output from at least one of the filters;

merging the copied first (L) number of stored samples (s(q)) and the calculated first number (L) of ringing samples (r(n)), the merging forming an overlap signal;

extrapolating a remaining number (N f −L) of samples for the corrupted frame; and

updating the stored samples for the corrupted frame.

2. The method of claim 1 , wherein the copying is performed in accordance with the expression:

sq ( n ) =ptfe×sq ( n−ppfre ), for n=N+ 1 , N+ 2 , . . . , N+L

wherein,

(N) represents a number of stored samples.

3. The method of claim 1 , wherein the merging is based upon an overlap-add technique.

4. The method of claim 3 , wherein the overlap-add technique includes applying respective weighting functions to each of the (L) number of ringing samples (r(n)) and the copied (L) number of stored samples (s(q)).

5. The method of claim 4 , wherein the weighting function are windowing functions including at least one of (i) a raised cosine window and (ii) a triangular window.

6. The method of claim 5 , wherein a first triangular window is applied to the (L) number of ringing samples (r(n)) and a second triangular window is applied to the copied (L) number of stored samples (s(q)).

7. The method of claim 6 , wherein the first triangular window ramps down within a range of about 1 to 0; and

wherein the second triangular window ramps up within a range of about 0 to 1.

8. The method of claim 4 , wherein the overlap add technique is performed in accordance with the expression:

sq ( N+n )← w u ( n ) sq ( N+n ) +w d ( n ) r ( n ), for n= 1,2 , . . . ,L

wherein,

the sign “←” means the quantity on its right-hand side overwrites the variable values on its left-hand side

w u (n) represents the overlap-add window that is ramping up; and

w d (n) represents the overlap-add window that is ramping down;

wherein N represents a number of stored sample.

9. The method of claim 8 , wherein if the time lag (ppfe) is greater than or equal to (N f ), then the remaining number of the (N f −L) samples (sq(n)) are determined in accordance with the expression;

sq ( n ) =ptfe×sq ( n−ppfe ), for n=N+L+ 1 , N+L+ 2 , . . . , N+N f

wherein,

(N f ) represents the number of samples in the replacement frame.

10. The method of claim 9 , wherein if the final time lag (ppfe) is less than (N f ), then the remaining number of the (N f −L) samples (sq(n)) are determined in accordance with the of the expression;

sq ( n ) =ptfe×sq ( n−ppfe ), for n=N+L+ 1 , N+L+ 2 , . . . , N+ppfe,

and then

sq ( n ) =sq ( n−ppfe ), for n=N+ppfe+ 1 ,N+ppfe+ 2 , . . . , N+N f

wherein,

(N f ) represents the number of samples in the replacement frame.

11. An apparatus for extrapolating a waveform based upon synthesizing a corrupted frame output from a decoder including one or more predictive filters, the corrupted frame being representative of one segment of a decoded signal, the apparatus comprising:

means for copying a first number (L) of (N f ) stored samples of the decoded signal (s(q)) in accordance with a time lag (ppfe) and a scaling factor (ptfe); and

means for calculating a first number (L) of ringing samples (r(n)) output from at least one of the filters;

means for merging the copied first (L) number of stored samples (s(q)) and the calculated first number (L) of ringing samples (r(n)), the merging forming an overlap signal; and

means for extrapolating a remaining number (N f −L) of samples for the corrupted frame.

12. The apparatus of claim 11 , wherein the copying is performed in accordance with the expression:

sq ( n ) =ptfe×sq ( n−ppfe ), for n=N+ 1 , N+ 2 , . . . , N+L

wherein,

(N) represents a number of stored samples.

13. The apparatus of claim 11 , wherein the merging is based upon an overlap-add technique.

14. The apparatus of claim 13 , wherein the overlap-add technique includes applying respective weighting functions to each of the (L) number of ringing samples (r(n)) and the copied (L) number of stored samples (s(q)).

15. The apparatus of claim 14 , wherein the weighting functions are windowing functions including at least one of (i) a raised cosine window and (ii) a triangular window.

16. The apparatus of claim 15 , wherein a first triangular window is applied to the (L) number of ringing samples (r(n)) and a second triangular window is applied to the copied (L) number of stored samples (s(q)).

17. The apparatus of claim 16 , wherein the first triangular window ramps down within a range of about 1 to 0; and

wherein the second triangular window ramps up within a range of about 0 to 1.

18. The apparatus of claim 14 , wherein the overlap add technique is performed in accordance with the expression:

sq ( N+n ) ←w u ( n ) sq ( N+n ) +w d ( n ) r ( n ), for n= 1, 2 , . . . , L

wherein,

the sign “←” means the quantity on its right-hand side overwrites the variable values on its left-hand side

w u (n) represents the overlap-add window that is ramping up; and

w d (n) represents the overlap-add window that is ramping down;

wherein N represents a number of stored samples.

19. The apparatus of claim 18 , wherein if the time lag (ppfe) is greater than or equal to (N f ), then the remaining number of the (N f −L) samples (sq(n)) are determined in accordance with the expression;

sq ( n ) =ptfe×sq ( n−ppfe ), for n=N+L+ 1 , N+L+ 2 , . . . , N+N f

wherein,

(N f ) represents the number of samples in the replacement frame.

20. The apparatus of claim 18 , wherein if the final time lag (ppfe) is less than (N f ), then the remaining number of the (N f −L) samples (sq(n)) are determined in accordance with the of the expression;

sq ( n ) =ptfe×sq ( n−ppfe ), for n=N+L+ 1 , N+L+ 2 , . . . , N+ppfe,

and then

sq ( n ) =sq ( n−ppfe ), for n=N+ppfe+ 1 , N+ppfe+ 2 , . . . , N+N f

wherein,

(N f ) represents the number of samples in the replacement frame.

21. A computer readable medium carrying one or more sequences of one or more instructions for execution by one or more processors to perform a method of removing discontinuities associated with synthesizing a corrupted frame output from a decoder including one or more predictive filters, the corrupted frame being representative of one segment of a decoded signal, the instructions when executed by the one or more processors, cause the one or more processors to perform the steps of:

copying a first number (L) of (N f ) stored samples of the decoded signal (s(q)) in accordance with a time lag (ppfe) and a scaling factor (ptfe); and

calculating a first number (L) of ringing samples (r(n)) output from at least one of the filters;

merging the copied first (L) number of stored samples (s(q)) and the calculated first number (L) of ringing samples (r(n)), the merging forming an overlap signal; and

extrapolating a remaining number (N f −L) of samples for the corrupted frame.

22. The computer readable medium of claim 21 , wherein the copying is performed in accordance with the expression:

sq ( n ) =ptfe×sq ( n−ppfe ), for n=N+ 1 , N+ 2 , . . . , N+L

wherein,

(N) represents a number of stored samples.

23. The computer readable medium of claim 21 , wherein the merging is based upon an overlap-add technique.

24. The computer readable medium of claim 23 , wherein the overlap-add technique includes applying respective weighting functions to each of the (L) number of ringing samples (r(n)) and the copied (L) number of stored samples (s(q)).

25. The computer readable medium of claim 24 , wherein the weighting function are windowing functions including at least one of (i) a raised cosine window and (ii) a triangular window.

26. The computer readable medium of claim 25 , wherein a first triangular window is applied to the (L) number of ringing samples (r(n)) and a second triangular window is applied to the copied (L) number of stored samples (s(q)).

27. The computer readable medium of claim 26 , wherein the first triangular window ramps down within a range of about 1 to 0; and

wherein the second triangular window ramps up within a range of about 0 to 1.

28. The computer readable medium of claim 24 , wherein the overlap add technique is performed in accordance with the expression:

sq ( N+n ) ←w u ( n ) sq ( N+n ) +w d ( n ) r ( n ), for n= 1, 2 , . . . , L

wherein,

the sign “←” means the quantity on its right-hand side overwrites the variable values on its left-hand side

w u (n) represents the overlap-add window that is ramping up; and

w d (n) represents the overlap-add window that is ramping down.

wherein (N) represents a number of stored samples.

29. The computer readable medium of claim 28 , wherein if the time lag (ppfe) is greater than or equal to (N f ), then the remaining number of the (N f −L) samples (sq(n)) are determined in accordance with the expression;

sq ( n ) =ptfe×sq ( n−ppfe ), for n=N+L+ 1 , N+L+ 2 , . . . , N+N f

wherein,

(N f ) represents the number of samples in the replacement frame.

30. The computer readable medium of claim 29 , wherein if the final time lag (ppfe) is less than (N f ), then the remaining number of the (N f −L) samples (sq(n)) are determined in accordance with the of the expression;

sq ( n ) =ptfe×sq ( n−ppfe ), for n=N+L+ 1 , N+L+ 2 , . . . , N+ppfe,

and then

sq ( n ) =sq ( n−ppfe ), for n=N+ppfe+ 1 , N+ppfe+ 2 , . . . , N+N f

wherein,

(N f ) represents the number of samples in the replacement frame.