Crossfading between higher order ambisonic signals

1. A method comprising:

obtaining, by an audio encoder, a decomposition of spherical harmonic coefficients (SHCs) that correspond to a first set of ambient SHCs, the decomposition including a first set of vectors representing spatial characteristics of an ambient sound field and a second set of vectors representing temporal and energy characteristics of the ambient sound field;

performing, by the audio encoder, energy compensation with respect to the first set of vectors to obtain a set of energy compensated vectors;

multiplying, by the audio encoder, the set of energy compensated vectors by the second set of vectors to obtain a first set of energy compensated ambient SHCs;

crossfading, by the audio encoder, between the first set of energy compensated ambient spherical harmonic coefficients (SHCs) and a second set of energy compensated ambient SHCs to obtain a first set of crossfaded energy compensated ambient SHCs.

2. The method of claim 1 ,

wherein the first set of SHCs include SHCs corresponding to basis functions having an order greater than one, and

wherein the second set of SHCs include SHCs corresponding to basis functions having an order greater than one.

3. The method of claim 1 , wherein performing the energy compensation comprises performing the energy compensation using a windowing function obtained as a function, at least in part, of one or more bits indicative of a frame length.

4. The method of claim 1 ,

wherein the first set of energy compensated ambient SHCs correspond to a current frame, and

wherein the second set of energy compensated ambient SHCs correspond to a previous frame.

5. The method of claim 1 , wherein crossfading comprises modifying a portion of the first set of energy compensated ambient SHCs based on a portion of the second set of energy compensated ambient SHCs.

6. An audio decoding device comprising:

a memory configured to store a first set of vectors representing spatial characteristics of a foreground sound field, a second set of vectors representing temporal and energy characteristics of the foreground sound field, a first set of energy compensated ambient spherical harmonic coefficients (SHCs), and a second set of energy compensated ambient SHCs, wherein the first set of energy compensated ambient SHCs describe a first ambient sound field and the second set of energy compensated ambient SHCs describe a second ambient sound field, and

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

crossfade between the first set of energy compensated ambient SHCs and the second set of energy compensated ambient SHCs to obtain a first set of crossfaded energy compensated ambient SHCs; and

render, based on the first set of vectors, the second set of vectors, and the first set of crossfaded energy compensated ambient SHCs, one or more speaker feeds.

7. The audio decoding device of claim 6 ,

wherein the first set of SHCs include SHCs corresponding to basis functions having an order greater than one, and

wherein the second set of SHCs include SHCs corresponding to basis functions having an order greater than one.

8. The audio decoding device of claim 6 ,

wherein the first set of energy compensated ambient SHCs correspond to a current frame, and

wherein the second set of energy compensated ambient SHCs correspond to a previous frame.

9. The audio decoding device of claim 6 , wherein the one or more processors are configured to crossfade by at least modifying a portion of the first set of energy compensated ambient SHCs based on a portion of the second set of energy compensated ambient SHCs.

10. The audio decoding device of claim 6 , further comprising a speaker configured to reproduce, based on the speaker feeds, a sound field.

11. An audio encoding device comprising:

one or more processors configured to:

obtain a decomposition of spherical harmonic coefficients (SHCs) that correspond to a first set of ambient SHCs, the decomposition including a first set of vectors representing spatial characteristics of an ambient sound field and a second set of vectors representing temporal and energy characteristics of the ambient sound field;

perform energy compensation with respect to the first set of vectors to obtain a set of energy compensated vectors;

multiply the set of energy compensated vectors by the second set of vectors to obtain a first set of energy compensated ambient SHCs;

a memory, coupled to the one or more processors, configured to store the first set of energy compensated ambient spherical harmonic coefficients (SHCs) and a second set of energy compensated ambient SHCs, and

wherein the one or more processors are further configured to crossfade between the first set of energy compensated ambient SHCs and the second set of energy compensated ambient SHCs to obtain a first set of crossfaded energy compensated ambient SHCs.

12. The audio encoding device of claim 11 ,

wherein the first set of SHCs include SHCs corresponding to basis functions having an order greater than one, and

wherein the second set of SHCs include SHCs corresponding to basis functions having an order greater than one.

13. The audio encoding device of claim 11 , wherein the one or more processors are configured to perform the energy compensation using a windowing function obtained as a function, at least in part, of one or more bits indicative of a frame length.

14. The audio encoding device of claim 11 ,

wherein the first set of energy compensated ambient SHCs correspond to a current frame, and

wherein the second set of energy compensated ambient SHCs correspond to a previous frame.

15. The audio encoding device of claim 11 , wherein the one or more processors are configured to crossfade by at least modifying a portion of the first set of energy compensated ambient SHCs based on a portion of the second set of energy compensated ambient SHCs.

16. The audio encoding device of claim 11 , further comprising a microphone configured to capture audio data indicative of the first and second sets of ambient SHCs.

17. The method of claim 1 , wherein the device is the audio encoder, the method further comprises capturing, by a microphone coupled to the audio encoder, audio data representative of a first set of ambient SHCs and a second set of ambient SHCs.

18. The method of claim 1 , wherein the device is the audio decoder, the method further comprises:

rendering one or more loudspeaker feeds based on the first set of crossfaded energy compensated ambient SHCs; and

reproducing, by one or more loudspeakers coupled to the audio decoder and based on the one or more loudspeaker feeds, a crossfaded ambient soundfield represented by the first set of crossfaded energy compensated ambient SHCs.

19. The audio decoding device of claim 6 ,

wherein the audio decoding device further comprises one or more speakers coupled to the one or more processors and configured to reproduce, based on the one or more speaker feeds, a sound field.

20. A method comprising:

obtain, by an audio decoder, a first set of vectors representing spatial characteristics of a foreground sound field and a second set of vectors representing temporal and energy characteristics of the foreground sound field,

obtain, by the audio decoder, a first set of energy compensated ambient spherical harmonic coefficients (SHCs) and a second set of energy compensated ambient SHCs, wherein the first set of energy compensated ambient SHCs describe a first ambient sound field and the second set of energy compensated ambient SHCs describe a second ambient sound field, and

crossfading, by the audio decoder, between the first set of energy compensated ambient SHCs and the second set of energy compensated ambient SHCs to obtain a first set of crossfaded energy compensated ambient SHCs; and

render, by the audio decoder and based on the first set of vectors, the second set of vectors, and the first set of crossfaded energy compensated ambient SHCs, one or more speaker feeds.

21. The method of claim 20 ,

wherein the first set of SHCs include SHCs corresponding to basis functions having an order greater than one, and

wherein the second set of SHCs include SHCs corresponding to basis functions having an order greater than one.

22. The method of claim 20 ,

wherein the first set of energy compensated ambient SHCs correspond to a current frame, and

wherein the second set of energy compensated ambient SHCs correspond to a previous frame.

23. The method of claim 20 , wherein crossfading between the first set of energy compensated ambient SHCs and the second set of energy compensated SHCs comprises crossfading by at least modifying a portion of the first set of energy compensated ambient SHCs based on a portion of the second set of energy compensated ambient SHCs.

24. The method of claim 20 , further comprising reproducing, by one or more speakers and based on the one or more speaker feeds, a sound field.

25. The method of claim 20 , wherein obtaining the first set of energy compensated SHCs and the second set of energy compensated SHCs comprises obtaining a bitstream that includes a representation of the crossfaded energy compensated ambient SHCs and a representation of crossfaded foreground SHCs that correspond to the crossfaded energy compensated ambient SHCs.

26. The method of claim 20 , wherein the first set of vectors and the second set of vectors represent crossfaded foreground SHCs, and wherein obtaining the first set of vectors and the second set of vectors comprises obtaining a bitstream that includes a representation of the crossfaded foreground SHCs.