Device and method for estimating harmonics in voice encoder

• US 20030204543A1
• Filed: 04/30/2003
• Published: 10/30/2003
• Est. Priority Date: 04/30/2002
• Status: Abandoned Application

• Current Assignee: LG-Ericsson Company Limited (Telefonaktiebolaget LM Ericsson)
• Original Assignee: LG Electronics, Inc. (LG Corporation)
• Inventors: Yoon, Sung Wan, Choi, Yong Soo, Youn, Dae Hee
• Application Number:
  US10/425,743
• Publication Number:
  US 20030204543A1
• Time in Patent Office: Days
• US Class Current: 708/300
• CPC Class Codes: G06F 17/142 Fast Fourier transforms, e.g. using a Cooley-Tukey type algorithm

Abstract

The present invention relates to methods and devices for estimating harmonics that reduce the calculation amount and can be used very effectively in a low transmission rate voice encoder by adjusting a harmonic interval with centering on a multiple of a basic frequency or extracting a peak so that the error between an original signal spectrum and estimated harmonic spectrum is reduced.

Claims

1. A harmonic estimating method comprising:

applying a window spectrum to an input signal, performing fast Fourier transformation of a predetermined amplitude on a generated spectrum, and calculating an input signal spectrum;

generating a synthesized signal spectrum of a fractional pitch candidate using the window spectrum scaled by a first basic frequency, harmonic amplitude, and high frequency signal amplitude;

calculating error energy of the input signal spectrum and the synthesized signal spectrum on each frequency band, and calculating a second basic frequency at which the error energy is minimized; and

calculating maximum harmonic amplitude at the second basic frequency.

2. The method according to claim 1, wherein the second basic frequency at which the error energy is minimized is selected by repeating the step of calculating the input signal spectrum and the synthesized signal spectrum of M fractional pitch candidates.

3. A harmonic estimating method comprising:

applying a window spectrum to an input signal, performing fast Fourier transformation of amplitude of N1 on a generated spectrum, and calculating an input signal spectrum;

applying a window spectrum scaled by harmonic amplitude to an integer pitch candidate, performing fast Fourier transformation of amplitude of N2 on a generated spectrum, and calculating a synthesized signal spectrum;

calculating an adjustment value of a high frequency at which error energy of the input signal spectrum and the synthesized signal spectrum for each band is minimized in range of the adjustment value of a harmonic frequency using the integer pitch candidate; and

calculating maximum harmonic amplitude by using the adjustment value of the high frequency at which the error energy for each band is minimized.

4. The method according to claim 3, wherein the adjustment value of the high frequency at which the error energy for each band is minimized is selected by squaring difference between an absolute value of the input signal spectrum and an absolute value of the synthesized signal spectrum, accumulating the squared difference from a start point of the band to an end point of the band, and selecting the adjustment value of the high frequency at which the error energy is minimized in range of a limit value of the adjustment value of the high frequency among the accumulated value.

5. The method according to claim 3, wherein the harmonic amplitude is estimated by:

if the input signal spectrum and the synthesized signal spectrum are found, calculating a maximum point in each harmonic band and a limit value of the harmonic frequency adjustment value;

calculating error energy for each band of the found input signal spectrum and the synthesized signal spectrum;

calculating a found harmonic frequency adjustment value and a found maximum point at which the error energy is minimized; and

calculating a final harmonic amplitude by using the found harmonic frequency adjustment value and the found maximum point.

6. The method according to claim 5, wherein the error energy is found by squaring a difference between an absolute value of the input signal spectrum and an absolute value of the synthesized signal spectrum and accumulating the squared differences for all harmonic bands.

7. The method according to claim 5, wherein the limit value of the harmonic frequency adjustment value is found by:

8. A harmonic estimating device comprising:

a harmonic frequency adjusting means for calculating a range of a harmonic frequency adjustment value using an integer unit pitch, and for selecting a frequency adjustment value at which error energy is minimized by using the harmonic frequency adjustment value belonging to the range; and

a harmonic amplitude estimating means for estimating a maximum harmonic amplitude by harmonics using the harmonic frequency adjustment value at which the error energy is minimized, the harmonic frequency adjustment value being found by the harmonic frequency adjusting means.

9. The device according to claim 8, wherein the range of the harmonic frequency adjustment value is proportional to a frequency and the range is small at a low frequency band and large at a high frequency band.

10. The device according to claim 8, wherein the error energy is found by squaring a difference between an absolute value of an input signal spectrum and an absolute value of a synthesized signal spectrum that are affected by the harmonic frequency adjustment value, and accumulating the squared difference from a start point of the harmonic to an end point of the harmonic.

11. The device according to claim 8, wherein the harmonic amplitude is estimated using the harmonic frequency adjustment value at which the error energy is minimized and a peak that coincides in harmonics of an original spectrum and a synthesized spectrum over the entire frequency band.

12. The device according to claim 11, further comprising a peak extracting means for extracting the peak in the entire frequency band.

13. The device according to claim 8, wherein the harmonic frequency adjusting means for selecting a value at which the harmonic amplitude is maximized selects an optimal frequency adjustment value by using a value that belongs to a range of harmonic frequency adjustment value.

14. A harmonic estimating device comprising:

a means for calculating an input signal spectrum of an input signal, and applying window spectrum to an integer pitch candidate, and a synthesized signal spectrum;

a means for extracting a peak point from each harmonic band, and calculating a limit value of frequency adjustment of each harmonic band;

a means for calculating error energy of the input signal spectrum and the synthesized signal spectrum for each band by using the limit value of frequency adjustment and the peak point;

a means for calculating a harmonic frequency adjustment value at which the error energy is minimized; and

a means for calculating a harmonic amplitude using the harmonic frequency adjustment value and the peak point.

15. The device according to claim 14, wherein the means for calculating the error energy adjusts a harmonic interval if the harmonic frequency adjustment value is not an adjustment value at which the error energy is minimized.

16. A harmonic estimating method comprising:

generating an input signal spectrum;

generating a synthesized signal spectrum;

calculating an adjustment value within a range of adjustment values at which error energy of the input signal spectrum and the synthesized signal spectrum for each band is minimized; and

estimating a maximum harmonic amplitude for each band by using the adjustment value for each band.

17. The method according to claim 16, wherein the error energy is determined by squaring a difference between an absolute value of the input signal spectrum and an absolute value of the synthesized signal spectrum, and accumulating the squared difference from a start point of the band to an end point of the band.

18. The method according to claim 16, further comprising:

determining a peak point in each band;

determining the adjustment value at which the error energy is minimized using the peak point; and

calculating the maximum harmonic amplitude using the harmonic frequency adjustment value and the peak point.

19. The method according to claim 16, wherein the error energy is found by squaring a difference between an absolute value of the input signal spectrum and an absolute value of the synthesized signal spectrum and accumulating the squared differences for the entire band.

20. The method according to claim 16, wherein the range is determined as ±

a limit value of the harmonic frequency adjustment value, wherein the limit value is found by;

21. The method according to claim 16, wherein the range for the harmonic adjustment value is proportional to frequency so that the range increases as frequency increases.

22. The method according to claim 16, further comprising:

changing the adjustment value to another value within the range if the adjustment value is not an adjustment value at which the error energy is minimized.

23. A harmonic estimating device comprising:

a harmonic frequency adjuster that calculates a range of harmonic frequency adjustment values, and that selects a harmonic frequency adjustment value within the range at which error energy is minimized for each band; and

a harmonic amplitude estimator that estimates a maximum harmonic amplitude for each band using the harmonic frequency adjustment value at which the error energy is minimized.

24. The device according to claim 23, wherein the range of the harmonic frequency adjustment value is proportional to a frequency and the range is small at a low frequency band and large at a high frequency band.

25. The device according to claim 23, wherein the error energy is found by squaring a difference between an absolute value of an input signal spectrum and an absolute value of a synthesized signal spectrum, and accumulating the squared difference from a start point of the band to an end point of the band.

26. The device according to claim 23, wherein the harmonic amplitude is estimated using the harmonic frequency adjustment value at which the error energy is minimized and a peak that coincides in harmonics of an original spectrum and a synthesized spectrum for each band.

27. The device according to claim 23, further comprising a peak extractor for extracting a peak value that coincides in harmonics of an original spectrum and a synthesized spectrum for each band.

28. The device according to claim 23, wherein the harmonic frequency adjuster selects a value at which the harmonic amplitude is maximized using an optimal frequency adjustment value within the range.

29. The method according to claim 23, wherein the harmonic frequency adjuster adjusts the adjustment value to another value within the range if the adjustment value is not an adjustment value at which the error energy is minimized.