Fast and memory efficient encoding of sound objects using spherical harmonic symmetries

1. A method, comprising:

receiving a set of monophonic sound inputs, wherein each of the set of monophonic sound inputs includes position and orientation information of a sound object relative to a source position; and

encoding the set of monophonic sound inputs into a higher order ambisonic (HOA) sound field in a spherical harmonics domain based on a spherical harmonics dataset that contains spherical harmonic coefficients for only a first sphere quadrant and based on a symmetry relationship between the first sphere quadrant and at least a second sphere quadrant; and

decoding the HOA sound field to generate a set of loudspeaker signals.

2. The method of claim 1 , further comprising:

convolving two or more of the generated set of loudspeaker signals and summing a left channel signal and a right channel signal to generate a binaural sound output.

3. The method of claim 1 , further comprising:

storing the spherical harmonics dataset as a spherical harmonics lookup table.

4. The method of claim 3 , further comprising:

computing the spherical harmonics lookup table prior to performing sound object encoding.

5. The method of claim 3 , further comprising:

determining a spherical harmonic coefficient of a second sphere quadrant based on a corresponding spherical harmonic coefficient of the first sphere quadrant from the spherical harmonics lookup table and based on the symmetry relationship.

6. The method of claim 1 , further comprising:

applying a gain correction to each of a plurality of Ambisonic channels of the HOA sound field to change a source spread of the sound object.

7. The method of claim 6 , further comprising:

applying an energy-preserving gain correction to each of a plurality of Ambisonic channels of the HOA sound field to maintain a total energy level of the HOA sound field.

8. A sound object rendering device, comprising:

a spherical harmonics dataset including a subset of all spherical harmonic coefficients for only a first sphere quadrant; and

an encoder to receive a set of monophonic sound inputs, wherein each of the set of monophonic sound inputs includes position and orientation information of a sound object relative to a source position, and further wherein the encoder is to encode the set of monophonic sound inputs into a higher order ambisonic (HOA) sound field in a spherical harmonics domain based on the spherical harmonics dataset and a symmetry relationship between the first sphere quadrant and at least a second sphere quadrant.

9. The sound object rendering device of claim 8 , further comprising:

a rendering module to decode the HOA sound field to generate a set of loudspeaker signals, and wherein the rendering module is further to convolve two or more of the generated set of loudspeaker signals to generate a binaural sound output.

10. The sound object rendering device of claim 8 , further comprising:

a shelf filter module to apply a gain correction to each of a plurality of Ambisonic channels of the HOA sound field to change a source spread of the sound object.

11. The sound object rendering device of claim 10 , wherein the shelf filter module is further to apply an energy-preserving gain correction to each of a plurality of Ambisonic channels of the HOA sound field to maintain a total energy level of the HOA sound field.

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

receive a set of monophonic sound inputs, wherein each of the set of monophonic sound inputs includes position and orientation information of a sound object relative to a source position;

encode, based on a spherical harmonics dataset including spherical harmonic coefficients for only a first sphere quadrant and based on a symmetry relationship between the first sphere quadrant and at least a second sphere quadrant, the set of monophonic sound inputs into a higher order ambisonic (HOA) sound field in a spherical harmonics domain; and

decode the HOA sound field to generate a set of loudspeaker signals.

13. The non-transitory computer-readable storage medium of claim 12 , wherein the one or more processors is further to:

convolve two or more of the generated set of loudspeaker signals and summing a left channel signal and a right channel signal to generate a binaural sound output.

14. The non-transitory computer-readable storage medium of claim 12 , wherein the one or more processors is further to:

store the spherical harmonics dataset as a spherical harmonics lookup table.

15. The non-transitory computer-readable storage medium of claim 14 , wherein the one or more processors is further to:

compute the spherical harmonics lookup table prior to performing sound object encoding.

16. The non-transitory computer-readable storage medium of claim 15 , wherein the one or more processors is further to:

compute the spherical harmonics lookup table by computing the first sphere quadrant of all spherical harmonic coefficients.

17. The non-transitory computer-readable storage medium of claim 16 , wherein the one or more processors is further to:

determine, based on a symmetry look-up table representing the symmetry relationship, a spherical harmonic coefficient of the second sphere quadrant from a corresponding spherical harmonic coefficient from the spherical harmonics lookup table.

18. The non-transitory computer-readable storage medium of claim 12 , wherein the one or more processors is further to:

applying a gain correction to each of a plurality of Ambisonic channels of the HOA sound field to change a source spread of the sound object.

19. The non-transitory computer-readable storage medium of claim 18 , wherein the one or more processors is further to:

apply an energy-preserving gain correction to each of a plurality of Ambisonic channels of the HOA sound field to maintain a total energy level of the HOA sound field.

20. A sound object rendering device, comprising:

a spherical harmonics dataset including spherical harmonic coefficients;

an encoder to receive a set of monophonic sound inputs, wherein each of the set of monophonic sound inputs includes position and orientation information of a sound object relative to a source position, and further wherein the encoder is to encode the set of monophonic sound inputs into a higher order ambisonic (HOA) sound field in a spherical harmonics domain based on the spherical harmonics dataset; and

a shelf filter module to apply at least one of: a gain correction to each of a plurality of Ambisonic channels of the HOA sound field to change a source spread of the sound object; and an energy-preserving gain correction to each of a plurality of Ambisonic channels of the HOA sound field to maintain a total energy level of the HOA sound field.