Spatial relation coding of higher order ambisonic coefficients

1. A device configured to decode audio data, the device comprising:

a memory configured to store at least a portion of a bitstream, the bitstream including a first indication representative of an HOA coefficient associated with the spherical basis function having an order of zero, and a second indication representative of one or more angles; and

one or more processors coupled to the memory, and configured to:

perform angle expansion with respect to the one or more angles to obtain one or more expanded angles; and

synthesize, based on the one or more expanded angles and the HOA coefficient associated with the spherical basis function having the order of zero, one or more HOA coefficients associated with one or more spherical basis functions having an order greater than zero.

2. The device of claim 1 , wherein the one or more processors are configured to perform an interpolation with respect to the one or more angles to obtain the one or more expanded angles.

3. The device of claim 1 , wherein the one or more processors are configured to perform a linear interpolation with respect to the one or more angles to obtain the one or more expanded angles.

4. The device of claim 1 ,

wherein the one or more angles include a first angle from a first frame of the bitstream and a second angle from a second frame of the bitstream, and

wherein the one or more processors are configured to perform a linear interpolation with respect to the first angle and the second angle to obtain the one or more expanded angles.

5. The device of claim 1 ,

wherein the one or more angles include a first angle from a first frame of the bitstream and a second angle from a second frame of the bitstream, the first frame occurring temporally directly before the second frame, and

wherein the one or more processors are configured to perform a linear interpolation with respect to the first angle and the second angle to obtain the one or more expanded angles.

6. The device of claim 1 ,

wherein the one or more angles include a first angle from a first frame of the bitstream and a second angle from a second frame of the bitstream, the first frame occurring temporally directly before the second frame, and

wherein the one or more processors are configured to perform a linear interpolation with respect to the first angle and the second angle to obtain an expanded angle of the one or more expanded parameters angle for each sample in the second frame.

7. The device of claim 1 , wherein the bitstream does not include the one or more HOA coefficients associated with the one or more spherical basis functions having the order greater than zero.

8. The device of claim 1 , wherein the one or more angles include a statistical mode value indicative of a value of the one or more angles that occurs most often.

9. The device of claim 8 ,

wherein the one or more angles comprises a plurality of angles, and wherein the bitstream includes the statistical mode value in place of the plurality of angles and the one or more HOA coefficients associated with the one or more spherical basis functions having the order greater than zero.

10. The device of claim 1 , wherein the one or more processors are further configured to perform speech decoding with respect to the first indication to obtain the HOA coefficient associated with the spherical basis function having the order of zero.

11. The device of claim 10 , wherein the one or more processors are configured to perform enhanced voice services (EVS) speech decoding with respect to the first indication to obtain the HOA coefficient associated with the spherical basis function having the order of zero.

12. The device of claim 10 , wherein the one or more processors are configured to perform adaptive multi-rate wideband (AMR-WB) speech decoding with respect to the first indication to obtain the HOA coefficient associated with the spherical basis function having the order of zero.

13. The device of claim 1 ,

wherein the one or more processors are further configured to:

render, based on the HOA coefficient associated with the spherical basis function having the order of zero and the one or more HOA coefficients associated with the one or more spherical basis functions having the order greater than zero, a speaker feed; and

output the speaker feed to a speaker.

14. The device of claim 1 , further comprising a receiver coupled to the one or more processors, and configured to receive at least the portion of the bitstream.

15. The device of claim 14 , wherein the receiver is configured to receive the bitstream in accordance with an enhanced voice services (EVS) standard.

16. A method of decoding audio data, the method comprising:

performing an angle expansion with respect to one or more angles to obtain one or more expanded angles; and

synthesizing, based on the one or more expanded angles and an HOA coefficient associated with a spherical basis function having an order of zero, one or more HOA coefficients associated with one or more spherical basis functions having an order greater than zero.

17. The method of claim 16 ,

wherein the one or more angles include a first angle, and

wherein the one or more expanded angles include a second angle.

18. The method of claim 16 ,

wherein the one or more angles include a first azimuth angle, and

wherein the one or more expanded angles include a second azimuth angle.

19. The method of claim 16 ,

wherein the one or more angles include a first elevation angle, and

wherein the one or more expanded angles include a second elevation angle.

20. The method of claim 16 ,

wherein the one or more angles include a first azimuth angle and a first elevation angle, and

wherein the one or more expanded angles include a second azimuth angle and a second elevation angle.

21. The method of claim 16 , wherein the one or more angles indicate an energy position within a frame of the HOA coefficient associated with the spherical basis function having the order of zero.

22. The method of claim 16 , wherein the one or more angles indicate an energy position within a portion of a frame of the HOA coefficient associated with the spherical basis function having the order of zero.

23. The method of claim 22 , wherein the portion of a frame includes a sub-frame.

24. The method of claim 22 , wherein the one or more angles indicate an energy position within each of four sub-frames of a frame of the HOA coefficient associated with the spherical basis function having the order of zero.

25. The method of claim 16 , wherein the one or more angles comprises a statistical mode value indicative of a value of the one or more angles that appears more frequently than other values of the one or more angles.

26. The method of claim 16 ,

wherein the bitstream further includes an indication representative of a prediction error, the prediction error representative of a difference between the one or more synthesized HOA coefficients and the one or more HOA coefficients associated with one or more spherical basis functions having an order greater than zero,

wherein the method further comprises updating, based on the prediction error, the one or more synthesized HOA coefficients.

27. A device configured to encode audio data, the device comprising:

a memory configured to store the audio data, the audio data representative of a higher order ambisonic (HOA) coefficient associated with a spherical basis function having an order of zero, and one or more HOA coefficients associated with one or more spherical basis functions having an order greater than zero; and

one or more processors coupled to the memory, and configured to:

obtain a plurality of angles from which to synthesize the one or more HOA coefficients associated with the one or more spherical basis functions having the order greater than zero;

obtain, based on the plurality of angles, a statistical mode value indicative of a value of the plurality of angles that appears more frequently than other values of the plurality of angles; and

generate a bitstream to include first indication representative of an HOA coefficient associated with the spherical basis function having an order of zero, and a second indication representative of the statistical mode value.

28. The device of claim 27 , wherein the one or more processors obtain the plurality of angles using a closed loop process in which determination of a prediction error is performed.

29. The device of claim 27 , further comprising:

a microphone coupled to the one or more processors, and configured to capture the audio data; and

a transmitter coupled to the one or more processors, and configured to transmit the bitstream, wherein the transmitter is configured to transmit the bitstream in accordance with an enhanced voice services (EVS) standard.

30. A method of encoding audio data, the method comprising:

obtaining a plurality of angles from which to synthesize one or more HOA coefficients associated with one or more spherical basis functions having an order greater than zero;

obtaining, based on the plurality of angles, a statistical mode value indicative of a value of the plurality of angles that appears more frequently than other values of the plurality of angles; and

generating a bitstream to include a first indication representative of an HOA coefficient associated with the spherical basis function having an order of zero, and a second indication representative of the statistical mode value.