Signal adaptation for higher band coding in a codec utilizing band split coding

• US 20050004793A1
• Filed: 05/04/2004
• Published: 01/06/2005
• Est. Priority Date: 07/03/2003
• Status: Abandoned Application

• Current Assignee: Nokia Corporation
• Original Assignee: Nokia Corporation
• Inventors: Ojala, Pasi, Vainio, Janne
• Application Number:
  US10/838,641
• Publication Number:
  US 20050004793A1
• Time in Patent Office: Days
• US Class Current: 704/219
• CPC Class Codes: G10L 19/0208 Subband vocoders
• CPC Class Codes: G10L 19/24 Variable rate codecs, e.g. for generating different qualities using a scalable representation such as hierarchical encoding or layered encoding
• CPC Class Codes: G10L 21/038 using band spreading techniques

Abstract

The present invention describes a novel methodology for adjusting a bandwidth extension algorithm by adapting one or more of enhancing perception parameters (e.g., a signal level, a signal energy and/or a gain) of a high-band encoded signal based on the characteristics of the input signal and an encoding performance in a low band with a codec utilizing audio-band-split coding by separate encoders and decoders for each audio band. The adaptation is based on the low-band coding algorithm. It can be at least two types of such an algorithm: e.g., an algebraic code excitation linear prediction (ACELP) algorithm for a speech-like input signal and a transform algorithm of a non-speech-like input signal, such that when the ACELP coding is selected, the corresponding enhancing perception parameter is gradually tuned down and when the encoding algorithm is changed to the transform coding, the corresponding enhancing perception parameter is gradually tuned up.

Claims

1. A method of adjusting a bandwidth extension algorithm for band-split encoding and decoding using analysis and synthesis filterbanks and separate encoders and decoders for each band, comprising the steps of:

receiving by a high-band encoder an indication signal generated by a low-band encoder in response to a low-band signal from said analysis filterbank; and

adjusting by the high-band encoder an enhancing perception parameter of a high-band encoded signal generated by the high-band encoder in response to a high-band signal from said analysis filterbank and based on said indication signal thus adjusting said bandwidth extension algorithm,

wherein the high-band signal and the low-band signal represent two signals out of M frequency-band signals generated by the analysis filterbank by splitting an input signal into M frequency bands, M is an integer of at least a value of two and a band frequency range of said high-band signal is higher than the band frequency range of said low-band signal, and wherein the high-band and low-band encoders with the analysis filterbank form a transmitter of the input signal and the high-band and low-band decoders with the synthesis filterbank form a receiver of a re-transmitted input signal which is spectrally encoded in said M bands with said adjustment applied to the high-band encoded signal.

2. The method of claim 1, wherein prior to said adjustment said enhancing perception parameter is generated in response to an excitation signal from the low-band encoder or from a random signal generator.

3. The method of claim 1, wherein said enhancing perception parameter is a signal level, a gain, or a signal energy, or their combination thereof.

4. The method of claim 1, wherein M=2.

5. The method of claim 1, wherein said indication signal is an indicator of an algebraic code excitation linear prediction (ACELP) type of coding used by the low-band encoder for generating the low-band signal for the input signal which is speech-like.

6. The method of claim 5, wherein, based on said indication signal, said enhancing perception parameter is gradually adjusted downwards towards a minimum threshold value until said threshold value is reached.

7. The method of claim 1, wherein said indication signal is an indicator of a transform type of coding used by the low-band encoder for generating the low-band signal for the input signal which is non-speech-like.

8. The method of claim 7, wherein, based on said indication signal, said enhancing perception parameter is gradually adjusted upwards towards a maximum threshold value until said threshold value is reached.

9. The method of claim 1, wherein, based on said indication signal, said enhancing perception parameter is gradually adjusted towards a threshold value until said threshold value is reached.

10. The method of claim 9, wherein said threshold value is a predetermined value, determined based on the input signal or provided by a sender of the input signal.

11. The method of claim 9, wherein, said threshold value is a minimum threshold value and said enhancing perception parameter is gradually adjusted downwards towards said minimum threshold value until said minimum threshold value is reached or wherein said threshold value is a maximum threshold value and said enhancing perception parameter is gradually adjusted upwards towards a maximum threshold value until said maximum threshold value is reached.

12. The method of claim 11, wherein the maximum threshold or the minimum threshold is a predetermined value.

13. The method of claim 1, wherein said enhancing perception parameter of the high-band encoded signal is quantized before said adjusting and, in response to the high-band encoded signal received by a high-band decoder, said enhancing perception parameter of a high-band decoded signal generated by said high-band decoder is adjusted by said high-band decoder based on a further indication signal containing identical information as said indication signal and generated by a low-band decoder in response to a low-band encoded signal from the low band encoder, thus further adjusting said bandwidth extension algorithm to keep synchronization with said adjustment performed by the high-band encoder.

14. A computer program product comprising:

a computer readable storage structure embodying computer program code thereon for execution by a computer processor with said computer program code characterized in that it includes instructions for performing the steps of the method of claim 1 indicated as being performed by any component of the transmitter or of the receiver.

15. A system for adjusting a bandwidth extension algorithm for band-split encoding and decoding, comprising:

an analysis filterbank, responsive to an input signal, for providing M frequency-band signals generated by splitting the input signal into M frequency bands, wherein M is an integer of at least a value of two;

a high-band encoder, responsive to a high-band signal and to an indication signal, for providing a high-band encoded signal and for adjusting an enhancing perception parameter of the high-band encoded signal thus adjusting said bandwidth extension algorithm; and

a low-band encoder, responsive to a low-band signal, for providing said indication signal,

wherein the high-band signal and the low-band signal represent two signals out of said M frequency-band signals generated by the analysis filterbank and a band frequency range of said high-band signal is higher than the band frequency range of said low-band signal.

16. The system of claim 15, wherein prior to said adjustment said enhancing perception parameter is generated in response to an excitation signal from the low-band encoder or from a random signal generator.

17. The system of claim 15, wherein said enhancing perception parameter is a signal level, a gain, or a signal energy, or their combination thereof

18. The system of claim 15, wherein M=2.

19. The system of claim 15, wherein said indication signal is an indicator of an algebraic code excitation linear prediction (ACELP) type of coding used by the low-band encoder for generating the low-band signal for the input signal which is speech-like.

20. The system of claim 19, wherein, based on said indication signal, said enhancing perception parameter is gradually adjusted downwards towards a minimum threshold value until said threshold value is reached.

21. The system of claim 15, wherein said indication signal is an indicator of a transform type of coding used by the low-band encoder for generating the low-band signal for the input signal which is non-speech-like.

22. The system of claim 21, wherein, based on said indication signal, said enhancing perception parameter is gradually adjusted upwards towards a maximum threshold value until said threshold value is reached.

23. The system of claim 15, wherein, based on said indication signal, said enhancing perception parameter is gradually adjusted towards a threshold value until said threshold value is reached.

24. The system of claim 23, wherein said threshold value is a predetermined value, determined based on the input signal or provided by a sender of the input signal.

25. The system of claim 23, wherein said threshold value is a minimum threshold value and said enhancing perception parameter is gradually adjusted downwards towards said minimum threshold value until said minimum threshold value is reached or wherein said threshold value is a maximum threshold value and said enhancing perception parameter is gradually adjusted upwards towards a maximum threshold value until said maximum threshold value is reached.

26. The system of claim 25, wherein the maximum threshold or the minimum threshold is a predetermined value.

27. The system of claim 15, wherein said system is contained in a portable electronic device, an electronic communication device, a mobile electronic device, a mobile phone or a communication network element.

28. The system of claim 15, further comprising

a high-band decoder, responsive to the high-band encoded signal for providing a high-band decoded signal;

a low-band decoder, responsive to a low-band encoded signal generated by the low-band encoder, for providing a low-band decoded signal; and

a synthesis filterbank, responsive to the high-band decoded signal and to the low-band decoded signal, for providing a synthesized output signal,

wherein the high-band and low-band encoders with the analysis filterbank form a transmitter of the input signal and the high-band and low-band decoders with the synthesis filterbank form a receiver of a re-transmitted input signal which is spectrally encoded in said M bands with said adjustment applied to the high-band encoded signal.

29. An electronic device, capable of adjusting a bandwidth extension algorithm for band-split encoding, comprising:

an analysis filterbank, responsive to an input signal, for providing M frequency-band signals generated by splitting the input signal into M frequency bands, wherein M is an integer of at least a value of two;

a high-band encoder, responsive to a high-band signal and to an indication signal, for providing a high-band encoded signal and for adjusting an enhancing perception parameter of the high-band encoded signal thus adjusting said bandwidth extension algorithm; and

a low-band encoder, responsive to a low-band signal, for providing said indication signal and for providing a low-band encoded signal,

wherein the high-band signal and the low-band signal represent two signals out of said M frequency-band signals generated by the analysis filterbank and a band frequency range of said high-band signal is higher than the band frequency range of said low-band signal.

30. The electronic device of claim 29, wherein said electronic device is a portable electronic device, an electronic communication device, a mobile electronic device, a mobile phone or a communication network element.

31. The electronic device of claim 29, wherein prior to said adjustment said enhancing perception parameter is generated in response to an excitation signal from the low-band encoder or from a random signal generator.

32. The electronic device of claim 29, wherein said enhancing perception parameter is a signal level, a gain, or a signal energy, or their combination thereof.

33. The electronic device of claim 29, wherein M=2.

34. The electronic device of claim 29, wherein said indication signal is an indicator of an algebraic code excitation linear prediction (ACELP) type of coding used by the low-band encoder for generating the low-band signal for the input signal which is speech-like.

35. The electronic device of claim 34, wherein, based on said indication signal, said enhancing perception parameter is gradually adjusted downwards towards a minimum threshold value until said threshold value is reached.

36. The electronic device of claim 29, wherein said indication signal is an indicator of a transform type of coding used by the low-band encoder for generating the low-band signal for the input signal which is non-speech-like.

37. The electronic device of claim 36, wherein, based on said indication signal, said enhancing perception parameter is gradually adjusted upwards towards a maximum threshold value until said threshold value is reached.

38. The electronic device of claim 29, wherein, based on said indication signal, said enhancing perception parameter is gradually adjusted towards a threshold value until said threshold value is reached.

39. The electronic device of claim 38, wherein said threshold value is a predetermined value, determined based on the input signal or provided by a sender of the input signal.

40. The electronic device of claim 38, wherein said threshold value is a minimum threshold value and said enhancing perception parameter is gradually adjusted downwards towards said minimum threshold value until said minimum threshold value is reached or wherein said threshold value is a maximum threshold value and said enhancing perception parameter is gradually adjusted upwards towards a maximum threshold value until said maximum threshold value is reached.

41. The electronic device of claim 40, wherein the maximum threshold or the minimum threshold is a predetermined value.