Method and Device For Noise Filling

• US 20130218577A1
• Filed: 01/31/2013
• Published: 08/22/2013
• Est. Priority Date: 08/27/2007
• Status: Active Grant

• Current Assignee: Telefonaktiebolaget LM Ericsson
• Original Assignee: Telefonaktiebolaget LM Ericsson
• Inventors: Taleb, Anisse, Briand, Manuel, Ullberg, Gustaf
• Granted Patent: US 9,111,532 B2
• Time in Patent Office: Days
• US Class Current: 704/500
• CPC Class Codes: G10L 19/028 Noise substitution, i.e. substituting non-tonal spectral components by noisy source comfort noise for discontinuous speech transmission G10L19/012
• CPC Class Codes: G10L 19/035 Scalar quantisation
• CPC Class Codes: G10L 21/0364 for improving intelligibility

Abstract

A method for perceptual spectral decoding comprises decoding of spectral coefficients recovered from a binary flux into decoded spectral coefficients of an initial set of spectral coefficients. The initial set of spectral coefficients are spectrum filled. The spectrum filling comprises noise filling of spectral holes by setting spectral coefficients in the initial set of spectral coefficients not being decoded from the binary flux equal to elements derived from the decoded spectral coefficients. The set of reconstructed spectral coefficients of a frequency domain formed by the spectrum filling is converted into an audio signal of a time domain. A perceptual spectral decoder comprises a noise filler, operating according to the method for perceptual spectral decoding.

Claims

1. A method for perceptual spectral decoding, comprising the steps of:

decoding spectral coefficients recovered from a binary flux into decoded spectral coefficients of an initial set of spectral coefficients;

spectrum filling said initial set of spectral coefficients into a set of reconstructed spectral coefficients, said spectrum filling comprising noise filling of spectral holes by setting spectral coefficients in said initial set of spectral coefficients not being decoded from said binary flux equal to elements derived from said decoded spectral coefficients; and

converting said set of reconstructed spectral coefficients of a frequency domain into an audio signal of a time domain.

2. The method according to claim 1, wherein said noise filling comprises creation of a spectral codebook dependent on said decoded spectral coefficients, whereby said noise filling of spectral holes comprises setting of spectral coefficients in said initial set of spectral coefficients equal to elements selected from said spectral codebook.

3. The method according to claim 2, wherein said spectral codebook comprises elements based on perceptually relevant decoded spectral coefficients from a present frame.

4. The method according to claim 2, wherein said spectral codebook comprises elements based on perceptually relevant decoded spectral coefficients from at least one of a past frame and a future frame.

5. The method according to claim 2, wherein said elements are selected from said spectral codebook according to at least one criterion.

6. The method according to claim 5, wherein said elements are selected from said spectral codebook in index order as a circular buffer, starting from a low frequency end.

7. The method according to claim 5, wherein said elements are selected from said spectral codebook based on a spectral distance between a spectral hole to be filled and said selected element.

8. The method according to claim 5, wherein said elements are selected from said spectral codebook based on an energy of a decoded spectral coefficient adjacent to a spectral hole to be filled and an energy of said selected element.

9. The method according to claim 2, wherein said noise filling further comprises post-processing of said spectral codebook, whereby said elements are selected from said post-processed spectral codebook.

10. The method according to claim 1, wherein said spectrum filling further comprises bandwidth extension.

11. The method according to claim 10, wherein said noise filling is performed for frequencies below a transition frequency (f_t) and said bandwidth extension is performed for frequencies above said transition frequency (f_t).

12. The method according to claim 10, wherein said bandwidth extension comprises spectral folding.

13. The method according to claim 1, wherein said noise filling is performed in a normalized domain.

14. The method according to claim 13, further comprising the step of applying a spectral fill envelope on said set of spectral coefficients in order to conserve an initial energy.

15. The method according to claim 1, wherein said converting comprises inverse transformation using at least one of an inverse transform and an inverse filter bank.

16. A method for signal handling in perceptual spectral decoding, comprising the steps of:

obtaining decoded spectral coefficients of an initial set of spectral coefficients;

spectrum filling said initial set of spectral coefficients into a set of reconstructed spectral coefficients, said spectrum filling comprising noise filling of spectral holes by setting spectral coefficients in said initial set of spectral coefficients having a zero magnitude or being non-decoded equal to elements derived from said decoded spectral coefficients; and

outputting said set of reconstructed spectral coefficients.

17. A perceptual spectral decoder, comprising:

an input for a binary flux;

a spectral coefficient decoder arranged for decoding spectral coefficients recovered from said binary flux into decoded spectral coefficients of an initial set of spectral coefficients;

a spectrum filler connected to said spectral coefficient decoder and arranged for spectrum filling said set of spectral coefficients, said spectrum filler comprising a noise filler for noise filling of spectral holes by setting spectral coefficients in said initial set of spectral coefficients not being decoded from said binary flux equal to elements derived from said decoded spectral coefficients;

a converter connected to said spectrum filler and arranged for converting said set of reconstructed spectral coefficients of a frequency domain into an audio signal of a time domain; and

an output for said audio signal.

18. The perceptual spectral decoder according to claim 17, wherein said noise filler in turn comprising a spectral codebook generator;

said spectral codebook generator being arranged for creating a spectral codebook from said decoded spectral coefficients, and

whereby said noise filler being arranged for filling said spectral holes with elements selected from said spectral codebook.

19. The perceptual spectral decoder according to claim 18, wherein said spectral codebook generator is arranged for creating said spectral codebook to comprise elements based on perceptually relevant decoded spectral coefficients from a present frame.

20. The perceptual spectral decoder according to claim 18, wherein said spectral codebook generator is arranged for creating said spectral codebook to comprise elements based on perceptually relevant decoded spectral coefficients from at least one of a past frame and a future frame.

21. The perceptual spectral decoder according to claim 18, wherein said noise filler being further arranged to select said elements from said spectral codebook according to at least one criterion.

22. The perceptual spectral decoder according to claim 21, wherein said noise filler being further arranged to select said elements from said spectral codebook in index order as a circular buffer, starting from a low frequency end.

23. The perceptual spectral decoder according to claim 21, wherein said noise filler being further arranged to select said elements from said spectral codebook based on a spectral distance between a spectral hole to be filled and said selected element.

24. The perceptual spectral decoder according to claim 21, wherein said noise filler being further arranged to select said elements from said spectral codebook based on an energy of a recovered spectral coefficient adjacent to a spectral hole to be filled and an energy of said selected element.

25. The perceptual spectral decoder according to claim 18, wherein said noise filler further comprises a postprocessor arranged for postprocessing said spectral codebook, whereby said noise filler being arranged for selecting said elements from said postprocessed spectral codebook.

26. The perceptual spectral decoder according to claim 17, wherein said spectrum filler further comprises a bandwidth extender.

27. The perceptual spectral decoder according to claim 26, wherein said noise filler is arranged for performing noise filling for frequencies below a transition frequency (f_t) and said bandwidth extender being arranged for extending a bandwidth for frequencies above said transition frequency (f_t).

28. The perceptual spectral decoder according to claim 26, wherein said bandwidth extender comprises a spectral folding section.

29. The perceptual spectral decoder according to claim 17, wherein said noise filler is arranged to operate in a normalized domain.

30. The perceptual spectral decoder according to claim 29, further comprising a spectral fill envelope applier arranged for applying a spectral fill envelope on said set of spectral coefficients in order to conserve an initial energy.

31. The perceptual spectral decoder according to claim 17, wherein said converter comprises at least one of an inverse transform section and an inverse filter bank.

32. A signal handling device for use in a perceptual spectral decoder, comprising:

an input for decoded spectral coefficients of an initial set of spectral coefficients;

a spectrum filler connected to said input and arranged for spectrum filling of said initial set of spectral coefficients into a set of reconstructed spectral coefficients, said spectrum filler comprising a noise filler for noise filling of spectral holes by setting spectral coefficients in said initial set of spectral coefficients having a zero magnitude or being non-decoded equal to elements derived from said decoded spectral coefficients; and

an output for said set of reconstructed spectral coefficients.