Method and apparatus for changing the relative positions of sound objects contained within a Higher-Order Ambisonics representation

Patent metadata

Field	Value
Publication number	US-9338574-B2
Application number	US-201214130074-A
Country	US
Kind code	B2
Filing date	Jun 15, 2012
Priority date	Jun 30, 2011
Publication date	May 10, 2016
Grant date	May 10, 2016

Abstract

Higher-order Ambisonics HOA is a representation of spatial sound fields that facilitates capturing, manipulating, recording, transmission and playback of complex audio scenes with superior spatial resolution, both in 2D and 3D. The sound field is approximated at and around a reference point in space by a Fourier-Bessel series. The invention uses space warping for modifying the spatial content and/or the reproduction of sound-field information that has been captured or produced as a higher-order Ambisonics representation. Different warping characteristics are feasible for 2D and 3D sound fields. The warping is performed in space domain without performing scene analysis or decomposition. Input HOA coefficients with a given order are decoded to the weights or input signals of regularly positioned (virtual) loudspeakers.

First claim

The invention claimed is:

1. A method for changing the relative positions of sound objects contained within a two-dimensional or a three-dimensional Higher-Order Ambisonics (HOA) representation of an audio scene, wherein an input vector A in with dimension O in determines the coefficients of a Fourier series of the input signal and an output vector A out with dimension O out determines the coefficients of a Fourier series of the correspondingly changed output signal, said method comprising:
decoding said input vector A in of input HOA coefficients into input signals s in in space domain for regularly positioned loudspeaker positions using a pseudo inverse of a mode matrix Ψ 1 by calculating

s

i
⁢

⁢
n

=

Ψ
T

⁡

(

Ψ
⁢

⁢

Ψ
T

)

-
1

⁢

A

i
⁢

⁢
n

;

and
warping and encoding in space domain said input signals s in into said output vector A out of adapted output HOA coefficients by calculating A out =Ψ 2 s in , wherein the mode vectors of the mode matrix Ψ 2 are modified with respect to the mode vectors of mode matrix Ψ 1 according to a warping function ƒ(φ) by which the angles of the regularly positioned loudspeaker positions are one-to-one mapped into the target angles of the target loudspeaker positions in said output vector A out .

2. The method of claim 1 , wherein said space domain input signals s in are weighted by a gain function g(φ) or g(θ,φ) prior to said warping and encoding.

3. The method of claim 2 , wherein for two-dimensional Ambisonics said gain function is

g
⁡

(
ϕ
)

=

ⅆ

f
⁡

(
ϕ
)

ⅆ
ϕ

,

and for three-dimensional Ambisonics said gain function is g(θ,φ)

g
⁡

(

θ
,
ϕ

)

=

ⅆ

f
θ

⁡

(
θ
)

ⅆ
θ

·

arc
⁢

⁢

cos
⁡

(

(

cos
⁢

⁢

f
θ

⁡

(

θ

i
⁢

⁢
n

)

)

2

+

(

sin
⁢

⁢

f
θ

⁡

(

θ

i
⁢

⁢
n

)

)

Assignees

• Jax Peter
• Batke Johann-Markus
• Thomson Licensing

Inventors

• Jax Peter
• Batke Johann-Markus

Classifications

• H04S2400/11

  Positioning of individual sound objects, e.g. moving airplane, within a sound field (H04S2420/13 takes precedence) · CPC title

• G10L21/00 Primary

  Speech or voice signal processing techniques to produce another audible or non-audible signal, e.g. visual or tactile, in order to modify its quality or its intelligibility (G10L19/00 takes precedence) · CPC title

• H04R2205/024

  Positioning of loudspeaker enclosures for spatial sound reproduction · CPC title

• H04S3/002

  Non-adaptive circuits, e.g. manually adjustable or static, for enhancing the sound image or the spatial distribution (control circuits for electronic adaptation of the sound field H04S7/30) · CPC title

• H04S2420/11

  Application of ambisonics in stereophonic audio systems · CPC title