Method and apparatus for obtaining a higher-order ambisonics (HOA) coefficient

An audio processing device comprising:

• a memory configured to store instructions;
• and
• one or more processors coupled to the memory and configured to execute the instructions to cause the audio processing device to:
• obtain location information of a virtual speaker on a preset spherical surface of a spherical space, wherein the location information comprises elevation information or azimuth information, wherein the elevation information comprises an elevation of the location information or an elevation index of the location information, wherein the elevation is φ, wherein the elevation index is φ′, wherein φ and φ′ have a relationship defined by the following formula:
• φ′=round(φ/(2πri×N)), wherein ri indicates a radius of the first circle of longitude, wherein rj is equal to the radius of the spherical space, wherein round( ) indicates rounding, wherein the preset spherical surface comprises M circles of longitude and N circles of latitude, wherein radii of the M circles of longitude are equal to a radius of the spherical space, wherein the M circles and the N circles intersect at reference points, wherein the reference points comprise first reference points on a first circle of the M circles and comprise second reference points on a second circle of the N circles, wherein a first quantity of the first reference points is greater than or equal to └N/4┘+1, wherein └ ┘ indicates rounding down, and wherein a second quantity of the second references points is greater than or equal to └M/4┘+1;
• obtain, based on the location information and a preset reference trigonometric function table, a first trigonometric function value corresponding to the location information, wherein the preset reference trigonometric function table comprises an elevation trigonometric function table, an azimuth trigonometric function table, or both the elevation trigonometric function table and the azimuth trigonometric function table, wherein the elevation trigonometric function table comprises a plurality of second trigonometric function values corresponding to elevation indexes of a plurality of first reference points, and the azimuth trigonometric function table comprises a plurality of third trigonometric function values corresponding to azimuth indexes of a plurality of second reference points;
• and
• obtain, based on the first trigonometric function value, a higher order ambisonics (HOA) coefficient for the virtual speaker,
• wherein a calculation formula for a 16-channel higher-order ambisonics (HOA) coefficient corresponding to a 3rd-order HOA signal comprises:
• m
• n
• Expression of HOA coefficient in polar coordinates
• 0
• 0
• 1
• 2
• ⁢
• π
• 1
• 0
• 1
• 2
• ⁢
• 3
• π
• ⁢
• cos
• ⁢
• θ
• +1
• 1
• 2
• ⁢
• 3
• π
• ⁢
• sin
• ⁢
• θcos
• ⁢
• φ
• −1
• 1
• 2
• ⁢
• 3
• π
• ⁢
• sin
• ⁢
• θsin
• ⁢
• φ
• 2
• 0
• 1
• 4
• ⁢
• 5
• π
• ⁢
• (
• 3
• ⁢
• cos
• 2
• ⁢
• θ
• -
• 1
• )
• +1
• 1
• 2
• ⁢
• 15
• π
• ⁢
• sin
• ⁢
• θcos
• ⁢
• θcosφ
• −1
• 1
• 2
• ⁢
• 15
• π
• ⁢
• sin
• ⁢
• θcos
• ⁢
• θsinφ
• +2
• 1
• 4
• ⁢
• 1
• ⁢
• 5
• π
• ⁢
• sin
• 2
• ⁢
• θcos2φ
• −2
• 1
• 4
• ⁢
• 15
• π
• ⁢
• sin
• 2
• ⁢
• θsin2φ
• 3
• 0
• 1
• 4
• ⁢
• 7
• π
• ⁢
• (
• 5
• ⁢
• cos
• 3
• ⁢
• θ
• -
• 3
• ⁢
• cos
• ⁢
• θ
• )
• +1
• 1
• 4
• ⁢
• 21
• 2
• ⁢
• π
• ⁢
• (
• 5
• ⁢
• cos
• 2
• ⁢
• θ
• -
• 1
• )
• ⁢
• sin
• ⁢
• θcos
• ⁢
• φ
• −1
• 1
• 4
• ⁢
• 21
• 2
• ⁢
• π
• ⁢
• (
• 5
• ⁢
• cos
• 2
• ⁢
• θ
• -
• 1
• )
• ⁢
• sin
• ⁢
• θsin
• ⁢
• φ
• +2
• 1
• 4
• ⁢
• 105
• π
• ⁢
• cos
• ⁢
• θsin
• 2
• ⁢
• θcos2
• ⁢
• φ
• −2
• 1
• 4
• ⁢
• 105
• π
• ⁢
• cos
• ⁢
• θsin
• 2
• ⁢
• θsin2
• ⁢
• φ
• +3
• 1
• 4
• ⁢
• 35
• 2
• ⁢
• π
• ⁢
• sin
• 3
• ⁢
• θcos
• ⁢
• 3
• ⁢
• φ
• −3
• 1
• 4
• ⁢
• 35
• 2
• ⁢
• π
• ⁢
• sin
• 3
• ⁢
• θsin3φ
• wherein θ indicates the azimuth information, wherein φ indicates the elevation information, wherein m indicates a sequence number of an HOA order, and wherein n indicates a direction parameter at each order.

A non-transitory computer-readable storage medium comprising computer-executable instructions that, when executed by a processor, cause an audio processing device to:

• obtain location information of a virtual speaker on a preset spherical surface of a spherical space, wherein the location information comprises elevation information, azimuth information, or both the elevation information and the azimuth information, wherein the elevation information comprises an elevation of the location information or an elevation index of the location information, wherein the elevation is φ, wherein the elevation index is φ′, wherein φ and φ′ have a relationship defined by the following formula:
• φ′=round(φ/(2πri×N)), wherein ri indicates a radius of the first circle of longitude, wherein rj is equal to the radius of the spherical space, wherein round( ) indicates rounding, wherein the preset spherical surface comprises M circles of longitude and N circles of latitude, wherein radii of the M circles of longitude are equal to a radius of the spherical space, and wherein the M circles and the N circles intersect at reference points, wherein the reference points comprise first reference points on a first circle of the M circles and comprise second reference points on a second circle of the N circles, wherein a first quantity of the first reference points is greater than or equal to └N/4┘+1, wherein └ ┘ indicates rounding down, and wherein a second quantity of the second references points is greater than or equal to └M/4┘+1;
• obtain, based on the location information and a preset reference trigonometric function table, a first trigonometric function value corresponding to the location information, wherein the preset reference trigonometric function table comprises an elevation trigonometric function table, an azimuth trigonometric function table, or both the elevation trigonometric function table and the azimuth trigonometric function table, wherein the elevation trigonometric function table comprises a plurality of second trigonometric function values corresponding to elevation indexes of a plurality of first reference points, and wherein the azimuth trigonometric function table comprises a plurality of third trigonometric function values corresponding to azimuth indexes of a plurality of second reference points, wherein the second reference points are on a first circle of latitude;
• and
• obtain, based on the first trigonometric function value, a higher order ambisonics (HOA) coefficient for the virtual speaker,
• wherein a calculation formula for a 16-channel higher-order ambisonics (HOA) coefficient corresponding to a 3rd-order HOA signal comprises:
• TABLE 1
• m
• n
• Expression of HOA coefficient in polar coordinates
• 0
• 0
• 1
• 2
• ⁢
• π
• 1
• 0
• 1
• 2
• ⁢
• 3
• π
• ⁢
• cos
• ⁢
• θ
• +1
• 1
• 2
• ⁢
• 3
• π
• ⁢
• sin
• ⁢
• θ
• ⁢
• cos
• ⁢
• φ
• −1
• 1
• 2
• ⁢
• 3
• π
• ⁢
• sin
• ⁢
• θ
• ⁢
• sin
• ⁢
• φ
• 2
• 0
• 1
• 4
• ⁢
• 5
• π
• ⁢
• (
• 3
• ⁢
• cos
• 2
• ⁢
• θ
• -
• 1
• )
• +1
• 1
• 2
• ⁢
• 15
• π
• ⁢
• sin
• ⁢
• θ
• ⁢
• cos
• ⁢
• θ
• ⁢
• cos
• ⁢
• φ
• −1
• 1
• 2
• ⁢
• 15
• π
• ⁢
• sin
• ⁢
• θ
• ⁢
• cos
• ⁢
• θ
• ⁢
• sin
• ⁢
• φ
• +2
• 1
• 4
• ⁢
• 15
• π
• ⁢
• sin
• 2
• ⁢
• θ
• ⁢
• cos
• ⁢
• 2
• ⁢
• φ
• −2
• 1
• 4
• ⁢
• 15
• π
• ⁢
• sin
• 2
• ⁢
• θ
• ⁢
• sin
• ⁢
• 2
• ⁢
• φ
• 3
• 0
• 1
• 4
• ⁢
• 7
• π
• ⁢
• (
• 5
• ⁢
• cos
• 3
• ⁢
• θ
• -
• 3
• ⁢
• cos
• ⁢
• θ
• )
• +1
• 1
• 4
• ⁢
• 2
• ⁢
• 1
• 2
• ⁢
• π
• ⁢
• (
• 5
• ⁢
• cos
• 2
• ⁢
• θ
• -
• 1
• )
• ⁢
• sin
• ⁢
• θ
• ⁢
• cos
• ⁢
• φ
• −1
• 1
• 4
• ⁢
• 2
• ⁢
• 1
• 2
• ⁢
• π
• ⁢
• (
• 5
• ⁢
• cos
• 2
• ⁢
• θ
• -
• 1
• )
• ⁢
• sin
• ⁢
• θ
• ⁢
• sin
• ⁢
• φ
• +2
• 1
• 4
• ⁢
• 1
• ⁢
• 0
• ⁢
• 5
• π
• ⁢
• cos
• ⁢
• θ
• ⁢
• sin
• 2
• ⁢
• θ
• ⁢
• cos
• ⁢
• 2
• ⁢
• φ
• −2
• 1
• 4
• ⁢
• 1
• ⁢
• 0
• ⁢
• 5
• π
• ⁢
• cos
• ⁢
• θ
• ⁢
• sin
• 2
• ⁢
• θ
• ⁢
• sin
• ⁢
• 2
• ⁢
• φ
• +3
• 1
• 4
• ⁢
• 35
• π
• ⁢
• sin
• 3
• ⁢
• θ
• ⁢
• cos
• ⁢
• 3
• ⁢
• φ
• −3
• 1
• 4
• ⁢
• 35
• π
• ⁢
• sin
• 3
• ⁢
• θ
• ⁢
• sin
• ⁢
• 3
• ⁢
• φ
• wherein θ indicates the azimuth information, wherein φ indicates the elevation information, wherein m indicates a sequence number of an HOA order, and wherein n indicates a direction parameter at each order.