Pitch period segmentation of speech signals
A method for automatic segmentation of pitch periods of speech waveforms takes a speech waveform, a corresponding fundamental frequency contour of the speech waveform, that can be computed by some standard fundamental frequency detection algorithm, and optionally the voicing information of the speech waveform, that can be computed by some standard voicing detection algorithm, as inputs and calculates the corresponding pitch period boundaries of the speech waveform as outputs by iteratively •calculating the Fast Fourier Transform (FFT) of a speech segment having a length of approximately two periods, the period being calculated as the inverse of the mean fundamental frequency associated with these speech segments, •placing the pitch period boundary either at the position where the phase of the third FFT coefficient is −180 degrees, or at the position where the correlation coefficient of two speech segments shifted within the two period long analysis frame maximizes, or at a position calculated as a combination of both measures stated above, and repeatedly shifting the analysis frame one period length further until the end of the speech waveform is reached.
1. A method for automatic segmentation of pitch periods of speech waveforms, the method comprising:
taking the speech waveform and the corresponding fundamental frequency contour of the speech waveform as inputs; and
calculating the corresponding pitch period boundaries of the speech waveform as outputs by iteratively calculating the Fast Fourier Transform (FFT) of a speech segment of approximately two period length, calculated as the inverse of the mean fundamental frequency associated with these speech segments, placing the pitch period boundary at the position where the phase of the third FFT coefficient is −180 degrees, and shifting the analysis frame one period length further until the end of the speech waveform is reached.
2. Method as claimed in claim 1 , wherein the method comprises computing corresponding fundamental frequency contour of the speech waveform by a fundamental frequency detection algorithm.
3. Method as claimed in claim 1 , wherein the method comprises computing voicing information of the speech waveform by a voicing detection algorithm.
4. Method as claimed in claim 1 , wherein the method comprises computing, in combination with calculating the FFT, the correlation coefficient of two speech sub-segments shifted relative to one another and separated by a period boundary within the two period long analysis frame as a periodicity measure, and setting the pitch period boundary at a weighted mean position of these two periodicity measures.
5. Method as claimed in claim 4 , wherein the method comprises setting the pitch period boundary at the mean position of these two periodicity measures.
6. A device for automatic segmentation of pitch periods of speech waveforms, the device comprising:
an input unit configured for taking a speech waveform and a corresponding fundamental frequency contour of the speech waveform as inputs, and
a calculating unit configured for calculating the corresponding pitch period boundaries of the speech waveform as outputs by iteratively choosing an analysis frame, the frame comprising a speech segment having a length of n periods with n being larger than 1 , a period being calculated as the inverse of the mean fundamental frequency associated with this speech segment, and then
either calculating the Fast Fourier Transform (FFT) of the speech segment and placing the pitch period boundary at the position where the phase of the (n+1) th FFT coefficient takes on a predetermined value; or
calculating a correlation coefficient of two speech sub-segments shifted relative to one another and separated by a period boundary within the analysis frame, and setting the pitch period boundary such that this correlation coefficient is maximal; or
at a position calculated as a combination of the two positions calculated in the manner described above, and
shifting the analysis frame one period length further and repeating the preceding steps until the end of the speech waveform is reached.
7. Device as claimed in claim 6 , wherein the input unit is configured for using voicing information corresponding to the speech waveform, computed by a voicing detection algorithm as additional input in such a way that only within voiced segments of the speech waveform the corresponding pitch period boundaries of the speech waveform are calculated as claimed in claim 6 .
8. Device as claimed in claim 6 , wherein an analysis frame comprising a speech segment having a length of 2 periods is used and the pitch period boundary is placed at the position where the phase of the third FFT coefficient takes on a value of −180 degrees.
9. Device as claimed in claim 6 , wherein an analysis frame comprising a speech segment having a length of 3 periods is used and the pitch period boundary is placed at the position where the phase of the 4 th FFT coefficient takes on a value of −180 degrees.
10. Device as claimed in claim 6 , wherein an analysis frame comprising a speech segment having a length of 4 periods is used and the pitch period boundary is placed at the position where the phase of the 5 th FFT coefficient takes on a value of 0 degrees.
11. Device as claimed in claims 6 , wherein the pitch period boundary is set at a position calculated as a weighted mean of a combination of positions.
12. Device as claimed in claim 11 , wherein the pitch period boundary is set at a position calculated as mean of the position where the phase of the third FFT coefficient takes on a value of −180 degrees and a position determined by the correlation coefficient of two speech sub-segments shifted relative to one another and separated by a period boundary within this analysis frame, wherein the pitch period boundary is set such that this correlation coefficient is maximal.
13. The device of claim 6 , wherein the input configured for taking the speech waveform is responsive to a voicing detection algorithm having identified that speech is present.
14. The device of claim 6 , wherein the calculating unit is responsive to a voicing detection algorithm having identified that speech is present.
15. The device of claim 6 , wherein the predetermined value is 0 degrees.
16. The device of claim 6 , wherein the predetermined value is −180 degrees.
17. A non-transitory computer-readable medium, in which a computer program is stored, which computer program, when being executed by a processor performs a method comprising:
receiving a speech waveform;
receiving a corresponding fundamental frequency contour of the speech waveform;
calculating pitch period boundaries of the speech waveform by iteratively choosing an analysis frame, the frame comprising a speech segment of approximately n periods, where n is an integer greater than 1, a period calculated as the inverse of the mean fundamental frequency associated with the speech segment;
placing the pitch period boundary at a position identified by one of:
calculating a Fast Fourier Transform (FFT) of the speech segment and identifying the position where the phase of the (n+1) th FFT coefficient takes on a predetermined value; or
calculating a correlation coefficient of two speech sub-segments shifted relative to one another and separated by a period boundary within the analysis frame and identifying the position such that the correlation coefficient is at a maximum; or
calculating a position as a combination of the two positions calculated in the manner described above; and
shifting the analysis frame one period length further until the end of the speech waveform is reached.
18. The non-transitory computer-readable medium of claim 17 , wherein receiving the speech waveform is responsive to a voicing detection algorithm having identified that speech is present.
19. The non-transitory computer-readable medium of claim 17 , wherein calculating pitch period boundaries is responsive to a voicing detection algorithm having identified that speech is present.
20. The non-transitory computer-readable medium of claim 17 , wherein the predetermined value is one of 0 degrees or −180 degrees.