Systems and methods for generating haptic effects associated with an envelope in audio signals

1. A system for outputting haptic effects comprising:

a processor configured to:

receive an audio signal;

determine an envelope signal associated with the audio signal, wherein determining the envelope signal comprises:

determining a Fast Fourier Transform of the audio signal within two or more time windows;

determining a magnitude for the Fast Fourier Transform for each time window;

determine a haptic effect based in part on the envelope signal;

output a haptic signal associated with the haptic effect;

an audio output device configured to receive the audio signal and output an audible effect;

a data store configured to receive the haptic signal and store the haptic effect in a haptic track on the data store; and

a haptic output device in communication with the processor, the haptic output device configured to receive the haptic signal and output the haptic effect.

2. The system of claim 1 , wherein the haptic effect comprises one or more of: a variation in coefficient of friction, a simulated texture, or a vibration.

3. The system of claim 1 , wherein determining an envelope signal associated with the audio signal further comprises:

determining a normalized signal by normalizing the magnitudes; and

determining the positive values from the normalized signal.

4. The system of claim 3 , wherein the time windows are overlapping.

5. The system of claim 4 , wherein the envelope signal is the positive values of the normalized signal.

6. The system of claim 1 , wherein determining an envelope signal associated with the audio signal comprises:

determining a power spectral density of the audio signal within two or more time windows;

determining a sum signal by summing the power spectral density values for each time window;

sampling the sum signal to determine a sample signal; and

interpolating and normalizing the sample signal.

7. The system of claim 6 , wherein the envelope signal is the interpolated and normalized sample signal.

8. The system of claim 1 , wherein the processor is further configured to filter the envelope signal.

9. The system of claim 8 , wherein filtering the envelope signal comprises one or more of: filtering the envelope signal using a threshold and filtering the envelope signal using a level of haptic silence.

10. A method for outputting haptic effects comprising:

receiving, by a processor, an audio signal;

determining, by the processor, an envelope signal associated with the audio signal, wherein determining the envelope signal comprises:

determining a Fast Fourier Transform of the audio signal within two or more time windows;

determining a magnitude for the Fast Fourier Transform for each time window;

determining a haptic effect based in part on the envelope signal;

storing a haptic signal associated with the haptic effect in a haptic track on a data store;

outputting the haptic signal to a haptic output device configured to receive the haptic signal and output the haptic effect; and

receiving the audio signal by an audio output device configured to receive the audio signal and output an audible effect.

11. The method of claim 10 , wherein the haptic effect comprises one or more of: a variation in coefficient of friction, a simulated texture, or a vibration.

12. The method of claim 10 , wherein determining an envelope signal associated with the audio signal further comprises:

determining a normalized signal by normalizing the magnitudes; and

determining the positive values from the normalized signal.

13. The method of claim 12 , wherein the time windows are overlapping.

14. The method of claim 12 , wherein the envelope signal is the positive values of the normalized signal.

15. The method of claim 10 , wherein determining an envelope signal associated with the audio signal comprises:

determining a power spectral density of the audio signal within two or more time windows;

determining a sum signal by summing the power spectral density values for each time window;

sampling the sum signal to determine a sample signal; and

interpolating and normalizing the sample signal.

16. The method of claim 15 , wherein the envelope signal is the interpolated and normalized sample signal.

17. The method of claim 10 , wherein the processor is further configured to filter the envelope signal.

18. The method of claim 17 , wherein filtering the envelope signal comprises one or more of: filtering the envelope signal using a threshold and filtering the envelope signal using a level of haptic silence.

19. A non-transitory computer readable medium comprising program code, which when executed by a processor, is configured to cause the processor to:

receive an audio signal;

determine an envelope signal associated with the audio signal, wherein determining the envelope signal comprises:

determining a Fast Fourier Transform of the audio signal within two or more time windows;

determining a magnitude for the Fast Fourier Transform for each time window;

determine a haptic effect based in part on the envelope signal;

storing a haptic signal associated with the haptic effect in a haptic track on a data store;

output the haptic signal to a haptic output device configured to receive the haptic signal and output the haptic effect; and

output the audio signal to an audio output device configured to output an audible effect.

20. The non-transitory computer readable medium of claim 19 , wherein the haptic effect comprises one or more of: a variation in coefficient of friction, a simulated texture, or a vibration.

21. The non-transitory computer readable medium of claim 19 , wherein determining an envelope signal associated with the audio signal further comprises:

determining a normalized signal by normalizing the magnitudes; and

determining the positive values from the normalized signal.

22. The non-transitory computer readable medium of claim 21 , wherein the time windows are overlapping.

23. The non-transitory computer readable medium of claim 21 , wherein the envelope signal is the positive values of the normalized signal.

24. The non-transitory computer readable medium of claim 19 , wherein determining an envelope signal associated with the audio signal comprises:

determining a power spectral density of the audio signal within two or more time windows;

determining a sum signal by summing the power spectral density values for each time window;

sampling the sum signal to determine a sample signal; and

interpolating and normalizing the sample signal.

25. The non-transitory computer readable medium of claim 24 , wherein the envelope signal is the interpolated and normalized sample signal.

26. The non-transitory computer readable medium of claim 19 , wherein the processor is further configured to filter the envelope signal.

27. The non-transitory computer readable medium of claim 26 , wherein filtering the envelope signal comprises one or more of: filtering the envelope signal using a threshold and filtering the envelope signal using a level of haptic silence.