Higher order ambisonics signal compression
Systems and techniques for compression and decoding of audio data are generally disclosed. An example device for compressing higher order ambisonic (HOA) coefficients representative of a soundfield includes a memory configured to store audio data and one or more processors configured to: determine when to use ambient HOA coefficients of the HOA coefficients to augment one or more foreground audio objects obtained through decomposition of the HOA coefficients based on one or more singular values also obtained through the decomposition of the HOA coefficients, the ambient HOA coefficients representative of an ambient component of the soundfield.
1. A method of compressing higher order ambisonic (HOA) coefficients representative of a soundfield, the method comprising:
determining whether to augment one or more foreground audio objects with ambient HOA coefficients of the HOA coefficients based on one or more singular values obtained through decomposition of the HOA coefficients, the ambient HOA coefficients representative of an ambient component of the soundfield, and the foreground audio objects and the ambient HOA coefficients being obtained through the decomposition of the HOA coefficients; wherein the HOA coefficients also include one or more foreground HOA coefficients representative of the one or more foreground audio objects of the soundfield, and
compressing, with an encoding device, the one or more foreground HOA coefficients; and
generating a bitstream including the compressed one or more foreground HOA coefficients.
2. The method of claim 1 , wherein determining whether to augment the one or more foreground audio objects in the bitstream with the ambient HOA coefficients comprises analyzing the one or more singular values obtained through the decomposition of the HOA coefficients.
3. The method of claim 1 , wherein determining whether to augment the one or more foreground audio objects in the bitstream with the ambient HOA coefficients comprises:
determining whether one or more ambient singular values of the one or more singular values are less than a threshold value, wherein the ambient singular values are associated with the ambient component of the soundfield; and
when the one or more ambient singular values associated with the ambient component are less than the threshold value, determining not to use the ambient HOA coefficients to augment the foreground audio objects.
4. The method of claim 3 , wherein determining whether to augment the one or more foreground audio objects in the bitstream with the ambient HOA coefficients comprises:
when the one or more ambient singular values are equal to or greater than the threshold value, determining to use the ambient HOA coefficients to augment the foreground audio objects.
5. The method of claim 1 , wherein each of the one or more singular values represents a square root of a corresponding energy value.
6. The method of claim 1 , wherein each of the one or more singular values represents a square root of a corresponding eigenvalue.
7. The method of claim 1 , further comprising coding one or more S matrices that include the one or more singular values.
8. The method of claim 1 , wherein determining whether to augment the one or more foreground audio objects in the bitstream with the ambient HOA coefficients is based on one or more amplitudes corresponding to one or more ambient singular values of the one or more singular values, the ambient singular values being associated with the ambient component of the soundfield.
9. The method of claim 1 , wherein determining whether to use the ambient HOA coefficients to augment the one or more foreground audio objects comprises:
determining to use the ambient HOA coefficients to augment the foreground audio objects; and
determining a number of bits to assign to the ambient component.
10. The method of claim 1 , further comprising compressing, with the encoding device, the ambient HOA coefficients, and wherein the bitstream also includes the compressed ambient coefficients.
11. A device for compressing higher order ambisonic (HOA) coefficients representative of a soundfield, the device comprising:
a memory configured to store the HOA coefficients of the soundfield; and
one or more processors configured to:
determine whether to augment one or more foreground audio objects in a bitstream with ambient HOA coefficients of the HOA coefficients, the ambient HOA coefficients representative of an ambient component of the soundfield, and the foreground audio objects and the ambient HOA coefficients being obtained through the decomposition of the HOA coefficients;
process the HOA coefficients, the HOA coefficients comprising one or more foreground HOA coefficients representative of the one or more foreground audio objects of the soundfield;
compress the one or more foreground HOA coefficients; and
generate a bitstream including the compressed one or more foreground HOA coefficients.
12. The device of claim 11 , wherein, to determine whether to augment the one or more foreground audio objects, the one or more processors are configured to analyze the one or more singular values obtained through the decomposition of the HOA coefficients.
13. The device of claim 11 , wherein, to determine whether to augment the one or more foreground audio objects in the bitstream with the ambient HOA coefficients, the one or more processors are configured to:
determine whether one or more ambient singular values of the one or more singular values are less than a threshold value, wherein the ambient singular values are associated with the ambient component of the soundfield; and
when the one or more ambient singular values associated with the ambient component are less than the threshold value, determine not to use the ambient HOA coefficients to augment the foreground audio objects.
14. The device of claim 13 , wherein, to determine whether to augment the one or more foreground audio objects in the bitstream with the ambient HOA coefficients, the one or more processors are configured to:
when the one or more ambient singular values are equal to or greater than the threshold value, augment the foreground audio objects in the bitstream with the ambient HOA coefficients.
15. The device of claim 11 , wherein the one or more processors are configured to
process the one or more singular values, each of the one or more singular values representing a square root of a corresponding energy value.
16. The device of claim 11 , wherein the one or more processors are configured to
process the one or more singular values, each of the one or more singular values representing a square root of a corresponding eigenvalue.
17. The device of claim 11 , wherein the one or more processors are further configured to code one or more S matrices that include the one or more singular values.
18. The device of claim 11 , wherein, to determine whether to augment the one or more foreground audio objects in the bitstream with the ambient HOA coefficients, the one or more processors are configured to determine whether to augment the one or more foreground audio objects in the bitstream with the ambient HOA coefficients based on one or more amplitudes corresponding to one or more ambient singular values of the one or more singular values, the ambient singular values being associated with the ambient component of the soundfield.
19. The device of claim 11 , wherein, to determine whether to augment the one or more foreground audio objects in the bitstream with the ambient HOA coefficients, the one or more processors are configured to:
determine to use the ambient HOA coefficients to augment the foreground audio objects; and
determine a number of bits to assign to the ambient component.
20. The device of claim 11 , further comprising a microphone array configured to capture audio data associated with the HOA coefficients representative of the soundfield.
21. The device of claim 20 , wherein the microphone array is configured to output the HOA coefficients representative of the soundfield.
22. The device of claim 20 , wherein the microphone array is included in a three-dimensional microphone.
23. The device of claim 11 , further comprising the one or more processors configured to compress the ambient HOA coefficients, and wherein the bitstream also includes the compressed ambient coefficients.
24. A device for compressing higher order ambisonic (HOA) coefficients representative of a soundfield, the device comprising:
means for determining whether to augment one or more foreground audio objects in a bitstream with ambient HOA coefficients of the HOA coefficients, the ambient HOA coefficients representative of an ambient component of the soundfield, and the foreground audio objects and the ambient HOA coefficients being obtained through the decomposition of the HOA coefficients;
means for processing the HOA coefficients, the HOA coefficients comprising one or more foreground HOA coefficients representative of the one or more foreground audio objects of the soundfield;
means for compressing the one or more foreground HOA coefficients; and
means for generating a bitstream including the compressed one or more foreground HOA coefficients.
25. The device of claim 24 , further comprising means for compressing the ambient HOA coefficients, and wherein the bitstream also includes the compressed ambient coefficients.