Method and device for applying dynamic range compression to a higher order ambisonics signal

• US 9,936,321 B2
• Filed: 03/24/2015
• Issued: 04/03/2018
• Est. Priority Date: 03/24/2014
• Status: Active Grant

• Current Assignee: Dolby Laboratories Licensing Corporation (Dolby Laboratories Incorporated)
• Original Assignee: Dolby Laboratories Licensing Corporation (Dolby Laboratories Incorporated)
• Inventors: Boehm, Johannes, Keiler, Florian
• Primary Examiner(s): HOLDER, REGINA NEAL
• Application Number:
  US15/127,775
• Publication Number:
  US 20170171682A1
• Time in Patent Office: 1,106 Days
• CPC Class Codes: G10L 19/008 Multichannel audio signal coding or decoding using interchannel correlation to reduce redundancy, e.g. joint-stereo, intensity-coding or matrixing
• CPC Class Codes: H04S 2420/01 Enhancing the perception of the sound image or of the spatial distribution using head related transfer functions [HRTF's] or equivalents thereof, e.g. interaural time difference [ITD] or interaural level difference [ILD]
• CPC Class Codes: H04S 2420/11 Application of ambisonics in stereophonic audio systems
• CPC Class Codes: H04S 3/008 in which the audio signals are in digital form, i.e. employing more than two discrete digital channels data reduction aspects thereof based on psychoacoustics G10L19/02
• CPC Class Codes: H04S 3/02 of the matrix type, i.e. in which input signals are combined algebraically, e.g. after having been phase shifted with respect to each other

Abstract

Dynamic Range Control (DRC) cannot be simply applied to Higher Order Ambisonics (HOA) based signals. A method for performing DRC on a HOA signal comprises transforming the HOA signal to the spatial domain, analyzing the transformed HOA signal, and obtaining, from results of said analyzing, gain factors that are usable for dynamic compression. The gain factors can be transmitted together with the HOA signal. When applying the DRC, the HOA signal is transformed to the spatial domain, the gain factors are extracted and multiplied with the transformed HOA signal in the spatial domain, wherein a gain compensated transformed HOA signal is obtained. The gain compensated transformed HOA signal is transformed back into the HOA domain, wherein a gain compensated HOA signal is obtained.

Claims

1. A method for dynamic range compression (DRC), the method comprising:

applying DRC in a Quadature Mirror Filter (QMF)-filter bank domain;

receiving a Higher Order Ambisonics (HOA) audio representation and a gain value g(n, m) corresponding to a time frequency tile (n, m);

applying the gain value and a Discrete Spherical Harmonics Transform (DSHT) matrix to the HOA audio representation,

wherein the gain value is applied based on

{hacek over (w)}_DRC(n, m)=diag(g(n, m))ŵ

_DSHT(n, m), wherein ŵ

_DSHT(n, m) is a vector of spatial channels for the time frequency tile (n, m), and wherein the vector ŵ

_DSHT(n, m) is determined based on an application of the DSHT matrix to HOA audio representation.

2. The method of claim 1, further comprising combining the DSHT matrix and rendering to loudspeaker channels based on

w(n, m)=D D_DSHT⁻

1{hacek over (w)}_DRC(n, m), wherein D_DSHT<sup>−

1</sup> is an inverse of the DSHT matrix and D is a HOA rendering matrix.

3. The method of claim 1, wherein the DSHT matrix is based on a prototype matrix Ď

₂ and a row-vector e.

4. The method of claim 1, further comprising receiving an indication of a simplified mode and, based on the simplified mode indication, multiplying the HOA audio representation with only one gain factor corresponding to the gain value.

5. The method of claim 1, wherein the HOA audio representation is divided into frequency subbands and the gain value is applied to each subband separately.

6. The method of claim 1, wherein at least if (N+1)²<

τ

, with N being an HOA order and τ

being a DRC block size, the method further comprising

transforming a gain vector to an HOA domain according to G=D_L<sup>−

1</sup> diag(g) D_L, with G being a gain matrix and D_L, being a DSHT matrix defining said DSHT; and

applying the gain matrix G to HOA coefficients of the HOA audio representation B according to B_DRC=GB, wherein a DRC compressed HOA signal B_DRC is obtained.

7. An apparatus for dynamic range compression (DRC), the apparatus comprising:

a receiver configured to obtain a Higher Order Ambisonics (HOA) audio representation and a gain value g(n, m) corresponding to a time frequency tile (n, m); and

an audio decoder configured to apply DRC in a Quadature Mirror Filter (QMF)-filter bank domain by applying the gain value and a Discrete Spherical Harmonics Transform (DSHT) matrix to the HOA audio representation,

wherein the gain value is applied based on

{hacek over (w)}_DRC(n, m)=diag(g(n, m))ŵ

_DSHT(n, m), wherein ŵ

_DSHT(n, m) is a vector of spatial channels for the time frequency tile (n, m), and wherein the vector ŵ

_DSHT(n, m) is determined based on an application of the DSHT matrix to HOA audio representation.

8. The apparatus of claim 7, wherein the decoder is further configured to combine the DSHT matrix and rendering to loudspeaker channels based on

w(n, m)=D D_DSHT⁻

1{hacek over (w)}_DRC(n, m), wherein D_DSHT<sup>−

1</sup> is an inverse of the DSHT matrix and D is a HOA rendering matrix.

9. The apparatus of claim 7, wherein the DSHT matrix is based on a prototype matrix Ď

₂ and a row-vector e.

10. The apparatus of claim 7, further comprising receiving an indication of a simplified mode, and, based on the simplified mode indication, multiplying the HOA audio representation with only one gain factor corresponding to the gain value.

11. The apparatus of claim 7, wherein the HOA audio representation is divided into frequency subbands and the gain value is applied to each subband separately.

12. The apparatus of claim 7, wherein at least if (N+1)²<

τ

, with N being the HOA order and r being a DRC block size, wherein the audio decoder is further configured to

transform a gain vector to an HOA domain according to G=D_L<sup>−

1</sup> diag(g) D_L, with G being a gain matrix and D_L, being a DSHT matrix defining said DSHT; and

apply the gain matrix G to HOA coefficients of the HOA audio representation B according to B_DRC=GB, wherein a DRC compressed HOA signal B_DRC is obtained.

13. A non-transitory computer readable storage medium having computer executable instructions that when executed on a computer cause the computer to perform a method for applying dynamic range compression (DRC), the method comprising:

applying DRC in a Quadature Mirror Filter (QMF)-filter bank domain;

receiving a Higher Order Ambisonics (HOA) audio representation and a gain value g(n, m) corresponding to a time frequency tile (n, m);

applying the gain value and a Discrete Spherical Harmonics Transform (DSHT) matrix to the HOA audio representation,

wherein the gain value is applied based on

{hacek over (w)}_DRC(n, m)=diag(g(n, m))ŵ

_DSHT(n, m), wherein ŵ

_DSHT(n, m) is a vector of spatial channels for the time frequency tile (n, m), and wherein the vector ŵ

_DSHT(n, m) is determined based on an application of the DSHT matrix to HOA audio representation.