Method for generating filter for audio signal, and parameterization device for same

• US 10,433,099 B2
• Filed: 11/01/2018
• Issued: 10/01/2019
• Est. Priority Date: 12/23/2013
• Status: Active Grant

• Current Assignee: GCOA Company Limited, Wilus Institute of Standards & Technology, Inc. (Good Day to Invent, Inc.)
• Original Assignee: Wilus Institute of Standards & Technology, Inc. (Good Day to Invent, Inc.)
• Inventors: Lee, Taegyu, Oh, Hyunoh
• Primary Examiner(s): Laekemariam, Yosef K
• Application Number:
  US16/178,581
• Publication Number:
  US 20190082285A1
• Time in Patent Office: 334 Days
• Field of Search: 381 1, 381 17, 381 18, 381 23, 381 61, 381 63, 381306, 381307, 381309
• CPC Class Codes: G10L 19/008 Multichannel audio signal coding or decoding using interchannel correlation to reduce redundancy, e.g. joint-stereo, intensity-coding or matrixing
• CPC Class Codes: G10L 19/0204 using subband decomposition
• CPC Class Codes: H04S 2400/01 Multi-channel, i.e. more than two input channels, sound reproduction with two speakers wherein the multi-channel information is substantially preserved
• CPC Class Codes: H04S 2400/03 Aspects of down-mixing multi-channel audio to configurations with lower numbers of playback channels, e.g. 7.1 -> 5.1 H04S2400/01 takes precedence
• CPC Class Codes: H04S 2420/01 Enhancing the perception of the sound image or of the spatial distribution using head related transfer functions [HRTF's] or equivalents thereof, e.g. interaural time difference [ITD] or interaural level difference [ILD]
• CPC Class Codes: H04S 2420/03 Application of parametric coding in stereophonic audio systems
• CPC Class Codes: H04S 2420/07 Synergistic effects of band splitting and sub-band processing
• CPC Class Codes: H04S 3/008 in which the audio signals are in digital form, i.e. employing more than two discrete digital channels data reduction aspects thereof based on psychoacoustics G10L19/02
• CPC Class Codes: H04S 7/305 Electronic adaptation of stereophonic audio signals to reverberation of the listening space H04S7/301 takes precedence
• CPC Class Codes: H04S 7/307 Frequency adjustment, e.g. tone control H04S7/301 takes precedence

Abstract

The present invention relates to a method for generating a filter for an audio signal and a parameterization device for the same, and more particularly, to a method for generating a filter for an audio signal, to implement filtering of an input audio signal with a low computational complexity, and a parameterization device therefor.

To this end, provided are a method for generating a filter for an audio signal, including: receiving at least one binaural room impulse response (BRIR) filter coefficients for binaural filtering of an input audio signal; converting the BRIR filter coefficients into a plurality of subband filter coefficients; obtaining average reverberation time information of a corresponding subband by using reverberation time information extracted from the subband filter coefficients; obtaining at least one coefficient for curve fitting of the obtained average reverberation time information; obtaining flag information indicating whether the length of the BRIR filter coefficients in a time domain is more than a predetermined value; obtaining filter order information for determining a truncation length of the subband filter coefficients, the filter order information being obtained by using the average reverberation time information or the at least one coefficient according to the obtained flag information and the filter order information of at least one subband being different from filter order information of another subband; and truncating the subband filter coefficient by using the obtained filter order information and a parameterization device therefor.

Claims

1. A method for processing an audio signal, comprising:

receiving an input audio signal;

receiving binaural room impulse response (BRIR) filter coefficients;

obtaining flag information indicating whether a length of the BRIR filter coefficients is more than a predetermined value in a time domain;

converting the BRIR filter coefficients into a set of subband filter coefficients for each subband;

obtaining average reverberation time information of a subband by using reverberation time information extracted from the set of subband filter coefficients;

obtaining one or more coefficients for curve fitting the average reverberation time information;

obtaining filter order information for determining a truncation length of the set of subband filter coefficients, wherein the filter order information is obtained, based on the flag information, by using the average reverberation time information or by using the one or more coefficients, and the filter order is determined to be variable in a frequency domain;

truncating the set of subband filter coefficients by using the filter order information, wherein an energy compensation is performed to the truncated set of subband filter coefficients based on the flag information; and

filtering each subband signal of the input audio signal by using the truncated set of subband filter coefficients corresponding thereto.

2. The method of claim 1, wherein when the flag information indicates that the length of the BRIR filter coefficients is more than the predetermined value, the filter order is determined based on a curve-fitted value by using the one or more coefficients.

3. The method of claim 2, wherein the curve-fitted value is determined to be a value of power of 2 having an approximated integer value as an index, and

the approximated integer value is obtained by performing a polynomial curve-fitting using the one or more coefficients.

4. The method of claim 1, wherein when the flag information indicates that the length of the BRIR filter coefficients is not more than the predetermined value, the filter order is determined based on the average reverberation time information of the subband without performing a curve fitting.

5. The method of claim 4, wherein the filter order is determined to be a value of power of 2 having a log-scaled approximated integer value of the average reverberation time information as an index.

6. The method of claim 1, wherein the filter order is determined to be a smaller value between a reference truncation length of the subband determined based on the average reverberation time information and an original length of the set of subband filter coefficients.

7. The method of claim 1, wherein the average reverberation time is an average value of reverberation time extracted from a set of subband filter coefficients for each channel in the same subband.

8. The method of claim 1, wherein the energy compensation is performed when the flag information indicates that the length of the BRIR filter coefficients is not more than a predetermined value.

9. The method of claim 1, wherein the energy compensation is performed by dividing the truncated set of subband filter coefficients by filter power up to a truncation point, and multiplying total filter power of the set of subband filter coefficients, and

wherein the truncation point is determined based on the filter order information.

10. The method of claim 1, wherein the method further comprises:

performing reverberation processing of each subband signal corresponding to a period subsequent to the truncated set of subband filter coefficients among the set of subband filter coefficients when the flag information indicates that the length of the BRIR filter coefficients is more than the predetermined value.

11. An apparatus for processing an audio signal, the apparatus configured to:

receive an input audio signal;

receive binaural room impulse response (BRIR) filter coefficients;

obtain flag information indicating whether a length of the BRIR filter coefficients is more than a predetermined value in a time domain;

convert the BRIR filter coefficients into a set of subband filter coefficients for each subband;

obtain average reverberation time information of a subband by using reverberation time information extracted from the set of subband filter coefficients;

obtain one or more coefficients for curve fitting the average reverberation time information;

obtain filter order information for determining a truncation length of the set of subband filter coefficients, wherein the filter order information is obtained, based on the flag information, by using the average reverberation time information or by using the one or more coefficients, and the filter order is determined to be variable in a frequency domain;

truncate the set of subband filter coefficients by using the filter order information, wherein an energy compensation is performed to the truncated set of subband filter coefficients based on the flag information; and

filter each subband signal of the input audio signal by using the truncated set of subband filter coefficients corresponding thereto.

12. The apparatus of claim 11, wherein when the flag information indicates that the length of the BRIR filter coefficients is more than the predetermined value, the filter order is determined based on a curve-fitted value by using the one or more coefficients.

13. The apparatus of claim 12, wherein the curve-fitted value is determined to be a value of power of 2 having an approximated integer value as an index, and

the approximated integer value is obtained by performing a polynomial curve-fitting using the one or more coefficients.

14. The apparatus of claim 11, wherein when the flag information indicates that the length of the BRIR filter coefficients is not more than the predetermined value, the filter order is determined based on the average reverberation time information of the subband without performing a curve fitting.

15. The apparatus of claim 14, wherein the filter order is determined to be a value of power of 2 having a log-scaled approximated integer value of the average reverberation time information as an index.

16. The apparatus of claim 11, wherein the filter order is determined to be a smaller value between a reference truncation length of the subband determined based on the average reverberation time information and an original length of the set of subband filter coefficients.

17. The apparatus of claim 11, wherein the average reverberation time is an average value of reverberation time extracted from a set of subband filter coefficients for each channel in the same subband.

18. The apparatus of claim 11, wherein the energy compensation is performed when the flag information indicates that the length of the BRIR filter coefficients is not more than a predetermined value.

19. The apparatus of claim 11, wherein the energy compensation is performed by dividing the truncated set of subband filter coefficients by filter power up to a truncation point, and multiplying total filter power of the set of subband filter coefficients, and

wherein the truncation point is determined based on the filter order information.

20. The apparatus of claim 11, wherein the apparatus is further configured to:

obtain the flag information indicating whether a length of the BRIR filter coefficients is more than a predetermined value in a time domain; and

perform reverberation processing of each subband signal corresponding to a period subsequent to the truncated set of subband filter coefficients among the set of subband filter coefficients when the flag information indicates that the length of the BRIR filter coefficients is more than the predetermined value.