1. A method of switching from a first sound signal coding mode to a second sound signal coding mode at the junction between a previous frame coded according to the first coding mode and a current frame coded according to the second coding mode, wherein the sound signal is filtered through a weighting filter to produce, in the current frame, a weighted signal, comprising:
calculating a zero-input response of the weighting filter;
windowing the zero-input response so that said zero-input response has an amplitude monotonically decreasing to zero after a predetermined time period; and
in the current frame, removing from the weighted signal the windowed zero-input response.', 'calculating a zero-input response of the weighting filter;', 'windowing the zero-input response so that said zero-input response has an amplitude monotonically decreasing to zero after a predetermined time period; and', 'in the current frame, removing from the weighted signal the windowed zero-input response.

2. A method of switching from a first sound signal coding mode to a second sound signal coding mode as defined in claim 1, wherein calculating a zero-input response of the weighting filter comprises calculating a zero-input response in the weighted domain.

3. A method of switching from a first sound signal coding mode to a second sound signal coding mode as defined in claim 1, wherein the first coding mode is an ACELP coding mode and the second coding mode is a TCX coding mode.

4. A method of switching from a first sound signal coding mode to a second sound signal coding mode as defined in claim 1, wherein windowing the zero-input response comprises truncating said zero-input response to the predetermined time period.

5. A method of switching from a first sound signal coding mode to a second sound signal coding mode as defined in claim 1, comprising, after the windowed zero-input response has been removed from the weighted signal, windowing the weighted signal into a TCX frame of predetermined duration.

6. A method of switching from a first sound signal coding mode to a second sound signal coding mode as defined in claim 5, further comprising transforming into the frequency domain the weighted signal windowed into a TCX frame of predetermined duration.

7. A method of switching from a first sound signal coding mode to a second sound signal coding mode as defined in claim 1, wherein the weighting filter is a perceptual weighting filter.

8. A device for switching from a first sound signal coding mode to a second sound signal coding mode at the junction between a previous frame coded according to the first coding mode and a current frame coded according to the second coding mode, wherein the sound signal is filtered through a weighting filter to produce, in the current frame, a weighted signal, comprising:
means for calculating a zero-input response of the weighting filter;
means for windowing the zero-input response so that said zero-input response has an amplitude monotonically decreasing to zero after a predetermined time period; and
means for removing, in the current frame, the windowed zero-input response from the weighted signal.', 'means for calculating a zero-input response of the weighting filter;', 'means for windowing the zero-input response so that said zero-input response has an amplitude monotonically decreasing to zero after a predetermined time period; and', 'means for removing, in the current frame, the windowed zero-input response from the weighted signal.

9. A device for switching from a first sound signal coding mode to a second sound signal coding mode at the junction between a previous frame coded according to the first coding mode and a current frame coded according to the second coding mode, wherein the sound signal is filtered through a weighting filter to produce, in the current frame, a weighted signal, comprising:
a calculator of a zero-input response of the weighting filter;
a window generator for windowing the zero-input response so that said zero-input response has an amplitude monotonically decreasing to zero after a predetermined time period; and
an adder for removing, in the current frame, the windowed zero-input response from the weighted signal.', 'a calculator of a zero-input response of the weighting filter;', 'a window generator for windowing the zero-input response so that said zero-input response has an amplitude monotonically decreasing to zero after a predetermined time period; and', 'an adder for removing, in the current frame, the windowed zero-input response from the weighted signal

10. A device for switching from a first sound signal coding mode to a second sound signal coding mode as defined in claim 9, wherein the zero-input response calculator calculates a zero-input response in the weighted domain

11. A device for switching from a first sound signal coding mode to a second sound signal coding mode as defined in claim 9, wherein the first coding mode is an ACELP coding mode and the second coding mode is a TCX coding mode

12. A device for switching from a first sound signal coding mode to a second sound signal coding mode as defined in claim 9, wherein the window generator truncates the zero-input response to the predetermined time period

13. A device for switching from a first sound signal coding mode to a second sound signal coding mode as defined in claim 9, comprising another window generator for windowing, after the windowed zero-input response has been removed from the weighted signal, the weighted signal into a TCX frame of predetermined duration

14. A device for switching from a first sound signal coding mode to a second sound signal coding mode as defined in claim 13, further comprising a frequency transform module which, in operation, transforms in the frequency domain the weighted signal windowed into a TCX frame of predetermined duration

15. A device for switching from a first sound signal coding mode to a second sound signal coding mode as defined in claim 9, wherein the weighting filter is a perceptual weighting filter

16. A method for producing from a decoded target signal an overlap-add target signal in a current frame coded according to a first coding mode, comprising:
windowing the decoded target signal of the current frame in a given window;
skipping a left portion of the window;
calculating a zero-input response of a weighting filter of the previous frame coded according to a second coding mode,
windowing the zero-input response so that said zero-input response has an amplitude monotonically decreasing to zero after a predetermined time period; and
adding the calculated zero-input response to the decoded target signal to reconstruct said overlap-add target signal.', 'windowing the decoded target signal of the current frame in a given window;', 'skipping a left portion of the window;', 'calculating a zero-input response of a weighting filter of the previous frame coded according to a second coding mode,', 'windowing the zero-input response so that said zero-input response has an amplitude monotonically decreasing to zero after a predetermined time period; and', 'adding the calculated zero-input response to the decoded target signal to reconstruct said overlap-add target signal

17. A method for producing an overlap-add target signal as defined in claim 16, comprising weighting the calculated zero-input response prior to windowing said calculated zero-input response

18. A method for producing an overlap-add target signal as defined in claim 17, wherein weighting the calculated zero-input response comprises perceptually weighting said calculated zero-input response

19. A method for producing an overlap-add target signal as defined in claim 16, comprising saving in a buffer a last portion of samples of the current frame.

20. A method for producing an overlap-add target signal as defined in claim 16, wherein the windowed, calculated zero-input response has an amplitude monotonically decreasing to zero after 10 ms.

21. A device for producing from a decoded target signal an overlap-add target signal in a current frame coded according to a first coding mode, comprising:
means for windowing the decoded target signal of the current frame in a given window;
means for skipping a left portion of the window;
means for calculating a zero-input response of a weighting filter of the previous frame coded according to a second coding mode,
means for windowing the zero-input response so that said zero-input response has an amplitude monotonically decreasing to zero after a predetermined time period; and
means for adding the calculated zero-input response to the decoded target signal to reconstruct said overlap-add target signal.', 'means for windowing the decoded target signal of the current frame in a given window;', 'means for skipping a left portion of the window;', 'means for calculating a zero-input response of a weighting filter of the previous frame coded according to a second coding mode,', 'means for windowing the zero-input response so that said zero-input response has an amplitude monotonically decreasing to zero after a predetermined time period; and', 'means for adding the calculated zero-input response to the decoded target signal to reconstruct said overlap-add target signal.

22. A device for producing from a decoded target signal an overlap-add target signal in a current frame coded according to a first coding mode, comprising:
a first window generator for windowing the decoded target signal of the current frame in a given window;
means for skipping a left portion of the window;
a calculator of a zero-input response of a weighting filter of the previous frame coded according to a second coding mode,
a second window generator for windowing the zero-input response so that said zero-input response has an amplitude monotonically decreasing to zero after a predetermined time period; and
an adder for adding the calculated zero-input response to the decoded target signal to reconstruct said overlap-add target signal.', 'a first window generator for windowing the decoded target signal of the current frame in a given window;', 'means for skipping a left portion of the window;', 'a calculator of a zero-input response of a weighting filter of the previous frame coded according to a second coding mode,', 'a second window generator for windowing the zero-input response so that said zero-input response has an amplitude monotonically decreasing to zero after a predetermined time period; and', 'an adder for adding the calculated zero-input response to the decoded target signal to reconstruct said overlap-add target signal.

23. A device for producing an overlap-add target signal as defined in claim 22, comprising a filter for weighting the calculated zero-input response prior to windowing said calculated zero-input response.

24. A device for producing an overlap-add target signal as defined in claim 23, wherein the weighting filter is a perceptual weighting filter.

25. A device for producing an overlap-add target signal as defined in claim 22, comprising a buffer for saving a last portion of samples of the current frame.

26. A device for producing an overlap-add target signal as defined in claim 22, wherein the windowed, calculated zero-input response has an amplitude monotonically decreasing to zero after 10 ms.']