Bidirectional propagation of sound

1. A system, comprising:

a processor; and

storage storing computer-readable instructions which, when executed by the processor, cause the system to:

receive an input sound signal for a directional sound source having a source location and a source orientation in a scene;

identify an encoded departure direction parameter corresponding to the source location of the directional sound source in the scene, the encoded departure direction parameter specifying a departure direction of initial sound on a sound path in which sound travels from the source location to a listener location around an occlusion in the scene; and

based at least on the encoded departure direction parameter and the input sound signal, render a directional sound at the listener location in a manner that accounts for the source location and the source orientation of the directional sound source.

2. The system of claim 1 , wherein the computer-readable instructions, when executed by the processor, cause the system to:

identify the encoded departure direction parameter from a precomputed departure direction field based at least on the source location and the listener location.

3. The system of claim 2 , wherein the computer-readable instructions, when executed by the processor, cause the system to:

compute the departure direction field from a representation of the scene.

4. The system of claim 2 , wherein the computer-readable instructions, when executed by the processor, cause the system to:

obtain directivity characteristics of the directional sound source; and

render the initial sound accounting for the directivity characteristics and the source orientation of the directional sound source.

5. The system of claim 4 , wherein the computer-readable instructions, when executed by the processor, cause the system to:

obtain directional hearing characteristics of a listener at the listener location and a listener orientation of the listener; and

render the initial sound as binaural output that accounts for the directional hearing characteristics of the listener and the listener orientation.

6. The system of claim 5 , wherein the directivity characteristics of the directional sound source comprise a source directivity function, and the directional hearing characteristics of the listener comprise a head-related transfer function.

7. A system, comprising:

a processor; and

storage storing computer-readable instructions which, when executed by the processor, cause the system to:

receive an input sound signal for a directional sound source having a source location and a source orientation in a scene;

identify encoded directional reflection parameters that are associated with the source location of the directional sound source and a listener location, wherein the encoded directional reflection parameters comprise aggregate directional loudness components of reflection energy from corresponding combinations of departure and arrival directions, and the aggregate directional loudness components are aggregated from decomposed directional loudness components of reflections emitted from the source location and arriving at the listener location; and

based at least on the input sound signal and the encoded directional reflection parameters, render directional sound reflections at the listener location that account for the source location and the source orientation of the directional sound source.

8. The system of claim 7 , wherein the computer-readable instructions, when executed by the processor, cause the system to:

encode the directional reflection parameters for the source location and the listener location prior to receiving the input sound signal.

9. The system of claim 8 , wherein the computer-readable instructions, when executed by the processor, cause the system to:

perform reflection simulations in the scene and decompose reflection loudness values obtained during the reflection simulations to obtain the aggregate directional loudness components.

10. The system of claim 7 , wherein the computer-readable instructions, when executed by the processor, cause the system to:

obtain directivity characteristics of the directional sound source;

obtain directional hearing characteristics of a listener at the listener location; and

render the directional sound reflections accounting for the directivity characteristics of the directional sound source, the source orientation of the directional sound source, the directional hearing characteristics of the listener, and a listener orientation of the listener.

11. The system of claim 10 , wherein the encoded directional reflection parameters comprise a reflections transfer matrix associated with the source location and the listener location.

12. The system of claim 7 , provided in a gaming console configured to execute video games or a virtual reality device configured to execute virtual reality applications.

13. A method comprising:

receiving impulse responses corresponding to a scene, the impulse responses corresponding to multiple sound source locations and a listener location in the scene;

encoding the impulse responses to obtain encoded departure direction parameters for individual sound source locations and the listener location, the encoded departure direction parameters providing sound departure directions from the individual sound source locations to the listener location;

encoding the impulse responses to obtain encoded aggregate representations of reflection enemy for corresponding combinations of departure and arrival directions of reflections traveling from the individual sound source locations to the listener location, the encoded aggregate representations of reflection energy being obtained by decomposing reflections in the impulse responses into directional loudness components and aggregating the directional loudness components; and

outputting the encoded departure direction parameters and the encoded aggregate representations of reflection energy.

14. The method of claim 13 , wherein the encoded departure direction parameters convey respective directions of initial sound emitted from the individual sound source locations to the listener location.

15. The method of claim 13 , further comprising:

encoding initial loudness parameters for the individual sound source locations; and

outputting the encoded initial loudness parameters with the encoded departure direction parameters.

16. The method of claim 15 , further comprising:

determining the encoded departure direction parameters for initial sound during a first time period; and

determining the initial loudness parameters during a second time period that encompasses the first time period.

17. The method of claim 13 , wherein a particular encoded aggregate representation for a particular source location includes at least:

aggregate loudness of reflections arriving at the listener location from a first direction and departing from the particular source location in the first direction, a second direction, a third direction, and a fourth direction;

aggregate loudness of reflections arriving at the listener location from the second direction and departing from the particular source location in the first direction, the second direction, the third direction, and the fourth direction;

aggregate loudness of reflections arriving at the listener location from the third direction and departing from the particular source location in the first direction, the second direction, the third direction, and the fourth direction; and

aggregate loudness of reflections arriving at the listener location from the fourth direction and departing from the particular source location in the first direction, the second direction, the third direction, and the fourth direction.

18. The method of claim 17 , wherein the particular encoded aggregate representation comprises a reflections transfer matrix.

19. The method of claim 18 , further comprising:

generating and outputting multiple reflections transfer matrices for multiple source/listener location pairs in the scene.

20. The method of claim 13 , further comprising:

rendering sound emitted from a particular directional sound source at a particular source location to a listener at a particular listener location based at least on a particular encoded departure direction parameter, a particular encoded arrival direction parameter, and a particular encoded aggregate representation of reflection energy for the particular source location and the particular listener location.