BINAURAL RENDERING OF SPHERICAL HARMONIC COEFFICIENTS

• US 20140355794A1
• Filed: 05/27/2014
• Published: 12/04/2014
• Est. Priority Date: 05/29/2013
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Morrell, Martin James, Peters, Nils Gnther, Sen, Dipanjan
• Granted Patent: US 9,420,393 B2
• Time in Patent Office: Days
• US Class Current: 381/303
• CPC Class Codes: G10K 15/12 using electronic time-delay networks
• 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: H04S 1/002 Non-adaptive circuits, e.g. manually adjustable or static, for enhancing the sound image or the spatial distribution control circuits for electronic adaptation of the sound field H04S7/30
• CPC Class Codes: H04S 1/005 For headphones
• 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 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 2420/07 Synergistic effects of band splitting and sub-band processing
• CPC Class Codes: H04S 2420/11 Application of ambisonics in stereophonic audio systems
• CPC Class Codes: H04S 3/004 For headphones
• CPC Class Codes: H04S 5/00 Pseudo-stereo systems, e.g. in which additional channel signals are derived from monophonic signals by means of phase shifting, time delay or reverberation
• 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 7/306 For headphones
• CPC Class Codes: H04S 7/307 Frequency adjustment, e.g. tone control H04S7/301 takes precedence

Abstract

A device comprises one or more processors configured to apply a binaural room impulse response filter to spherical harmonic coefficients representative of a sound field in three dimensions so as to render the sound field.

Claims

1. A method of binaural audio rendering comprising:

applying a binaural room impulse response filter to spherical harmonic coefficients representative of a sound field in three dimensions so as to render the sound field.

2. The method of claim 1, wherein applying the binaural room impulse response filter comprises applying an irregular binaural room impulse response filter to the spherical harmonic coefficients so as to render the sound field, wherein the irregular binaural room impulse response filter comprises one or more binaural room impulse response filters for an irregular arrangement of speakers.

3. The method of claim 1,

wherein applying the binaural room impulse response filter comprises applying a regular binaural room impulse response filter to the spherical harmonic coefficients so as to render the sound field, and

wherein the regular binaural room impulse response filter comprises one or more binaural room impulse response filters for a regular arrangement of speakers.

4. The method of claim 1, wherein applying the binaural room impulse response filter to spherical harmonic coefficients representative of the sound field in three dimensions so as to render the sound field generates left and right modified spherical harmonic coefficients, the method further comprising:

summing first modified spherical harmonic coefficients over the number of orders and sub-orders associated with the spherical harmonic coefficients to generate a first frequency domain speaker feed, the first modified spherical harmonic coefficients comprising either the left modified spherical harmonic coefficients or the right modified spherical harmonic coefficients;

inverting spherical harmonic coefficients of the first modified spherical harmonic coefficients that are associated with a negative sub-order to generate inverted spherical harmonic coefficients; and

summing the inverted spherical harmonic coefficients over the number of orders and sub-orders to generate a second frequency domain speaker feed.

5. The method of claim 1, wherein an order of spherical basis functions to which the spherical harmonic coefficients correspond is greater than one.

6. The method of claim 1, further comprising:

interpolating an irregular binaural room impulse response filter to generate a regular binaural room impulse response filter, wherein the irregular binaural room impulse response filter comprises one or more binaural room impulse response filters for an irregular arrangement of speakers and the regular binaural room impulse response filter comprises one or more binaural room impulse response filters for a regular arrangement of speakers, and

wherein applying the binaural room impulse response filter comprises applying the regular binaural room impulse response filter to the spherical harmonic coefficients so as to render the sound field.

7. The method of claim 1, further comprising:

applying a windowing function to the binaural room impulse response filter to generate a windowed binaural room impulse response filter,

wherein applying the binaural room impulse response filter comprises applying the windowed binaural room impulse response filter to the spherical harmonic coefficients so as to render the sound field.

8. The method of claim 1, further comprising:

transforming the binaural room impulse response filter from a time domain to a frequency domain so as to generate a transformed binaural room impulse response filter,

wherein applying the binaural room impulse response filter comprises applying the transformed binaural room impulse response filter to the spherical harmonic coefficients so as to render the sound field.

9. The method of claim 1, further comprising:

transforming the binaural room impulse response filter from a time domain to a frequency domain so as to generate a transformed binaural room impulse response filter; and

transforming the spherical harmonic coefficients from the time domain to the frequency domain so as to generate a transformed spherical harmonic coefficients,

wherein applying the binaural room impulse response filter comprises applying the transformed binaural room impulse response filter to the transformed spherical harmonic coefficients so as to render a frequency domain representation of the sound field, and

wherein the method further comprises applying an inverse transform to the frequency domain representation of the sound field to render the sound field.

10. The method of claim 1, wherein applying the binaural room impulse response filter comprises applying the binaural room impulse response filter directly to the spherical harmonic coefficients.

11. A device comprising:

one or more processors configured to apply a binaural room impulse response filter to spherical harmonic coefficients representative of a sound field in three dimensions so as to render the sound field.

12. The device of claim 11, wherein the one or more processors are further configured to, when applying the binaural room impulse response filter, apply an irregular binaural room impulse response filter to the spherical harmonic coefficients so as to render the sound field, wherein the irregular binaural room impulse response filter comprises one or more binaural room impulse response filters for an irregular arrangement of speakers.

13. The device of claim 11, wherein the one or more processors are further configured to, when applying the binaural room impulse response filter, apply a regular binaural room impulse response filter to the spherical harmonic coefficients so as to render the sound field, wherein the regular binaural room impulse response filter comprises one or more binaural room impulse response filters for a regular arrangement of speakers.

14. The device of claim 11, wherein the one or more processors are further configured to:

apply the binaural room impulse response filter to spherical harmonic coefficients representative of the sound field in three dimensions so as to render the sound field to generate left and right modified spherical harmonic coefficients;

sum first modified spherical harmonic coefficients over the number of orders and sub-orders associated with the spherical harmonic coefficients to generate a first frequency domain speaker feed, the first modified spherical harmonic coefficients comprising either the left modified spherical harmonic coefficients or the right modified spherical harmonic coefficients;

invert spherical harmonic coefficients of the first modified spherical harmonic coefficients that are associated with a negative sub-order to generate inverted spherical harmonic coefficients; and

sum the inverted spherical harmonic coefficients over the number of orders and sub-orders to generate a second frequency domain speaker feed.

15. The device of claim 11, wherein an order of spherical basis functions to which the spherical harmonic coefficients correspond is greater than one.

16. The device of claim 11,

wherein the one or more processors are further configured to interpolate an irregular binaural room impulse response filter to generate a regular binaural room impulse response filter, wherein the irregular binaural room impulse response filter comprises one or more binaural room impulse response filters for an irregular arrangement of speakers and the regular binaural room impulse response filter comprises one or more binaural room impulse response filters for a regular arrangement of speakers, and

wherein the one or more processors are further configured to, when applying the binaural room impulse response filter, apply the regular binaural room impulse response filter to the spherical harmonic coefficients so as to render the sound field.

17. The device of claim 11,

wherein the one or more processors are further configured to apply a windowing function to the binaural room impulse response filter to generate a windowed binaural room impulse response filter, and

wherein the one or more processors are further configured to, when applying the binaural room impulse response filter, apply the windowed binaural room impulse response filter to the spherical harmonic coefficients so as to render the sound field.

18. The device of claim 11,

wherein the one or more processors are further configured to transform the binaural room impulse response filter from a time domain to a frequency domain so as to generate a transformed binaural room impulse response filter, and

wherein the one or more processors are further configured to, when applying the binaural room impulse response filter, apply the transformed binaural room impulse response filter to the spherical harmonic coefficients so as to render the sound field.

19. The device of claim 11,

wherein the one or more processors are further configured to transform the binaural room impulse response filter from a time domain to a frequency domain so as to generate a transformed binaural room impulse response filter, and transform the spherical harmonic coefficients from the time domain to the frequency domain so as to generate a transformed spherical harmonic coefficients,

wherein the one or more processors are further configured to, when applying the binaural room impulse response filter, apply the transformed binaural room impulse response filter to the transformed spherical harmonic coefficients so as to render a frequency domain representation of the sound field, and

wherein the one or more processors are further configured to apply an inverse transform to the frequency domain representation of the sound field to render the sound field.

20. The device of claim 11, wherein the one or more processors are further configured to, when applying the binaural room impulse response filter, apply the binaural room impulse response filter directly to the spherical harmonic coefficients.

21. An apparatus comprising:

means for determining spherical harmonic coefficients representative of a sound field in three dimensions; and

means for applying a binaural room impulse response filter to spherical harmonic coefficients representative of a sound field so as to render the sound field.

22. The apparatus of claim 21, wherein the means for applying the binaural room impulse response filter comprises means for applying an irregular binaural room impulse response filter to the spherical harmonic coefficients so as to render the sound field, wherein the irregular binaural room impulse response filter comprises one or more binaural room impulse response filters for an irregular arrangement of speakers.

23. The apparatus of claim 21, wherein the means for applying the binaural room impulse response filter comprises means for applying a regular binaural room impulse response filter to the spherical harmonic coefficients so as to render the sound field, wherein the regular binaural room impulse response filter comprises one or more binaural room impulse response filters for a regular arrangement of speakers.

24. The apparatus of claim 21,

wherein the means for applying the binaural room impulse response filter to spherical harmonic coefficients representative of the sound field in three dimensions so as to render the sound field generate left and right modified spherical harmonic coefficients, the apparatus further comprising:

means for summing first modified spherical harmonic coefficients over the number of orders and sub-orders associated with the spherical harmonic coefficients to generate a first frequency domain speaker feed, the first modified spherical harmonic coefficients comprising either the left modified spherical harmonic coefficients or the right modified spherical harmonic coefficients;

means for inverting spherical harmonic coefficients of the first modified spherical harmonic coefficients that are associated with a negative sub-order to generate inverted spherical harmonic coefficients; and

means for summing the inverted spherical harmonic coefficients over the number of orders and sub-orders to generate a second frequency domain speaker feed.

25. The apparatus of claim 21, wherein an order of spherical basis functions to which the spherical harmonic coefficients correspond is greater than one.

26. The apparatus of claim 21, further comprising means for interpolating an irregular binaural room impulse response filter to generate a regular binaural room impulse response filter, wherein the irregular binaural room impulse response filter comprises one or more binaural room impulse response filters for an irregular arrangement of speakers and the regular binaural room impulse response filters comprise one or more binaural room impulse response filters for a regular arrangement of speakers, and

wherein the means for applying the binaural room impulse response filter comprises means for applying the regular binaural room impulse response filter to the spherical harmonic coefficients so as to render the sound field.

27. The apparatus of claim 21, further comprising:

means for applying a windowing function to the binaural room impulse response filter to generate a windowed binaural room impulse response filter,

wherein the means for applying the binaural room impulse response filter comprises means for applying the windowed binaural room impulse response filter to the spherical harmonic coefficients so as to render the sound field.

28. The apparatus of claim 21, further comprising means for transforming the binaural room impulse response filter from a time domain to a frequency domain so as to generate a transformed binaural room impulse response filter,

wherein the means for applying the binaural room impulse response filter comprises means for applying the transformed binaural room impulse response filter to the spherical harmonic coefficients so as to render the sound field.

29. The apparatus of claim 21, further comprising:

means for transforming the binaural room impulse response filter from a time domain to a frequency domain so as to generate a transformed binaural room impulse response filter; and

means for transforming the spherical harmonic coefficients from the time domain to the frequency domain so as to generate a transformed spherical harmonic coefficients,

wherein the means for applying the binaural room impulse response filter comprises means for applying the transformed binaural room impulse response filter to the transformed spherical harmonic coefficients so as to render a frequency domain representation of the sound field, and

wherein the apparatus further comprises means for applying an inverse transform to the frequency domain representation of the sound field to render the sound field.

30. A non-transitory computer-readable storage medium having stored thereon instructions that, when executed, cause one or more processors to:

apply a binaural room impulse response filter to spherical harmonic coefficients representative of a sound field in three dimensions so as to render the sound field.