Method and apparatus for rendering audio sound field representation for audio reproduction

Abstract

To provide a method and an apparatus for rendering a Higher Order Ambisonics (HOA) format audio representation for any loudspeaker setup.SOLUTION: A method for rendering an audio sound field representation for an arbitrary spatial loudspeaker setup includes the steps of obtaining a decoding matrix for rendering to a given arrangement of target loudspeakers by obtaining the number of target speakers and their positions, the positions of a spherical modeling grid and an HOA order, generating a mixing matrix from the positions of the modeling grid and the positions of the speakers, generating a mode matrix from the positions of the spherical modeling grid and the HOA order, calculating a first decoding matrix from the mixing matrix and the mode matrix, and smoothing and scaling the first decoding matrix using smoothing and scaling factors.SELECTED DRAWING: None

Description

[Technical field]

[0001] The present invention relates to a method and apparatus for rendering an audio sound field representation for audio playback, in particular an audio representation in Ambisonics format. [Background technology]

[0002] Accurate localization / localization is a primary goal for any spatial audio reproduction system. Such reproduction systems are highly applicable for conferencing systems, games or other virtual environments that benefit from 3D sound. Sound scenes in 3D can be synthesized or captured as natural sound fields. A sound field signal, e.g. Ambisonics, carries a representation of the desired sound field. The Ambisonics format is based on a spherical harmonic decomposition of the sound field. The basic Ambisonics format or B-format uses spherical harmonics of orders 0 and 1, while the so-called Higher Order Ambisonics (HOA) also uses further spherical harmonics of at least second order. To obtain the individual loudspeaker signals from such Ambisonics format signals, a decoding or rendering process is required. The spatial arrangement of the loudspeakers is referred to as the loudspeaker setup in this paper. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] International Publication No. 2011 / 117399 (Johann-Markus Batke, Florian Keiler, and Johannes Boehm, Method and device for decoding an audio soundfield representation for audio playback (PD100011)) [Non-patent literature]

[0004] [Non-Patent Document 1] TD Abhayapala, Generalized framework for spherical microphone arrays: Spatial and frequency decomposition, Proc. IEEE International Conference on Acoustics, Speech, and Signal Processing (ICASSP), (Accepted) Vol. X, pp. , April 2008, Las Vegas, USA [Non-Patent Document 2] [This translation is missing a number (Patent Document 1)] [Non-Patent Document 3] Jerome Daniel, Rozenn Nicol, and Sebastien Moreau, Further investigations of high order ambisonics and wavefield synthesis for holophonic sound imaging, AES Convention Paper 5788 Presented at the 114th Convention, March 2003. Paper 4795 presented at the 114th Convention [Non-Patent Document 4] Jerome Daniel, Representation de champs acoustiques, application a la transmission et a la reproduction de scenes sonores complexes dans un contexte multimedia, PhD thesis, Universite Paris 6, 2001 [Non-Patent Document 5] James R. Driscoll and Dennis M. Healy Jr., Computing Fourier transforms and convolutions on the 2-sphere, Advances in Applied Mathematics, 15:202-250, 1994 [Non-Patent Document 6] Jorg Fliege, Integration nodes for the sphere, http: / / www.personal.soton.ac.uk / jf1w07 / nodes / nodes.html, online, accessed 2012-06-01 [Non-Patent Document 7] Jorg Fliege and Ulrike Maier, A two-stage approach for computing cubature formula for the sphere, Technical Report, Fachbereich Mathematik, Universitat Dortmund, 1999 [Non-Patent Document 8] RH Hardin and NJA Sloane, Webpage: Spherical designs, spherical t-designs, http: / / www2.research.att.com / ~njas / sphdesigns / [Non-Patent Document 9] RH Hardin and NJA Sloane, Mclaren's improved snub cube and other new spherical designs in three dimensions, Discrete and Computational Geometry, 15:429-441, 1996 [Non-Patent Document 10] MA Poletti, Three-dimensional sound surround systems based on spherical harmonics., J. Audio Eng. Soc, 53(11):1004-1025, November 2005 [Non-Patent Document 11] Ville Pulkki, Spatial Sound Generation and Perception by Amplitude Panning Techniques, PhD thesis, Helsinki University of Technology, 2001 [Non-Patent Document 12] Boaz Rafaely, Plane-wave decomposition of the sound field on a sphere by spherical convolution, J. Acoust. Soc. Am., 4(116):2149-2157, October 2004 [Non-Patent Document 13] Earl G. Williams, Fourier Acoustics, volume 93 of Applied Mathematical Sciences. Academic Press, 1999 [Non-Patent Document 14] F. Zotter, H. Pomberger, and M. Noisternig, Energy-preserving ambisonic decoding, Acta Acustica united with Acustica, 98(1):37-47, January / February 2012 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the known rendering approaches are only suitable for normal loudspeaker setups, whereas arbitrary loudspeaker setups are much more common. If such rendering approaches are applied to arbitrary loudspeaker setups, problems arise with the directivity of the sound. [Means for solving the problem]

[0006] The present invention describes a method for rendering / decoding audio sound field representations for both regular and non-regular spatial loudspeaker distributions, said rendering / decoding offering significantly improved localization properties and being energy-conserving. In particular, the present invention provides a new method for obtaining a decoding matrix for sound field data, for example in HOA format. The HOA format describes a sound field that is not directly related to loudspeaker positions. Since the resulting loudspeaker signals are necessarily channel-based audio formats, the decoding of HOA signals is always closely related to the rendering of audio signals. Thus, the present invention relates to both the decoding and the rendering of sound field related audio formats.

[0007] One advantage of the present invention is that an energy-conserving decoding with very good directional attributes is achieved. The term "energy-conserving" means that the energy in the HOA directional signal is preserved after decoding, so that for example a directional spatial sweep of constant amplitude is perceived at constant loudness. The term "good directional attributes" refers to a loudspeaker directivity characterized by a directional main lobe and small side lobes, which is enhanced compared to normal rendering / decoding.

[0008] The present invention discloses a rendering of a Higher Order Ambisonics (HOA)-like sound field signal for any loudspeaker setup that gives significantly improved localization properties and is energy-conserving. This is obtained by a new type of decoding matrix for sound field data and a new method for obtaining said decoding matrix. In a method for rendering an audio sound field representation for any spatial loudspeaker setup, the decoding matrix for said rendering to a given arrangement of target loudspeakers is obtained by obtaining the number of target speakers and their positions, the positions of a spherical modeling grid and the HOA order, generating a mixing matrix from the positions of the modeling grid and the positions of the speakers, generating a mode matrix from the positions of the spherical modeling grid and the HOA order, calculating a first decoding matrix from the mixing matrix and the mode matrix, and smoothing and scaling the first decoding matrix with smoothing and scaling factors to obtain an energy-conserving decoding matrix.

[0009] In one embodiment the invention relates to a method for decoding and / or rendering an audio sound field representation for audio reproduction according to claim 1. In another embodiment the invention relates to an apparatus for decoding and / or rendering an audio sound field representation for audio reproduction according to claim 9. In yet another embodiment the invention relates to a computer readable medium having stored thereon executable instructions for causing a computer to perform a method for decoding and / or rendering an audio sound field representation for audio reproduction according to claim 15.

[0010] In general, the invention uses the following approach: First, panning functions are derived that depend on the loudspeaker setup used for playback. Second, decoding matrices (e.g. Ambisonics decoding matrices) are calculated from these panning functions (or the mixing matrices derived from them) for all loudspeakers of the loudspeaker setup. In a third step, the decoding matrices are generated and processed to be energy-conserving. Finally, the decoding matrices are filtered to smooth the loudspeaker panning and suppress side lobes. The filtered decoding matrix is ​​used to render the audio signal for a given loudspeaker setup. Side lobes are a side effect of rendering and give the audio signal in undesired directions. Side lobes are annoying since the rendering is optimized for a given loudspeaker setup. It is an advantage of the invention that side lobes are minimized, thereby improving the directivity of the loudspeaker signals.

[0011] According to an embodiment of the present invention, a method for rendering / decoding an audio sound field representation for audio playback comprises the steps of buffering received HOA time samples b(t) to form blocks of M samples and time indexes μ, and filtering the coefficients B(μ) to form frequency-filtered coefficients B(μ).

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[0013] The decoding matrix D for the rendering step, i.e. for a given arrangement of target speakers, is derived by the steps of obtaining the number of target speakers and their positions, determining the positions of a spherical modeling lattice and an HOA order, generating a mixing matrix from the positions of the spherical modeling lattice and the positions of the speakers, generating a mode matrix from the spherical modeling lattice and the HOA order, and synthesizing the mixing matrix G and the mode matrix G.

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[0015] According to another aspect, an apparatus for decoding an audio sound field representation for audio reproduction comprises a rendering processing unit having a decoding matrix calculation unit for obtaining the decoding matrix D, the decoding matrix calculation unit comprising means for obtaining a number L of target speakers and positions of those speakers.

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[0024] According to yet another aspect, a computer-readable medium stores executable instructions which, when executed on a computer, cause the computer to perform a method for decoding an audio sound field representation for audio reproduction as disclosed above.

[0025] Further objects, features and advantages of the present invention will become apparent from the following description and appended claims when considered in conjunction with the accompanying drawings. [Brief description of the drawings]

[0026] Exemplary embodiments of the present invention will now be described with reference to the accompanying drawings. [Figure 1] 1 is a flowchart of a method according to an embodiment of the present invention. [Diagram 2] 4 is a flowchart of a method for constructing a mixing matrix G. [Diagram 3] FIG. 2 is a block diagram of a renderer. [Figure 4] 1 is a flow chart of the general steps of a decoding matrix generation process. [Diagram 5] FIG. 2 is a block diagram of a decoding matrix generation unit. [Figure 6] An exemplary 16 speaker setup where speakers are shown as connected nodes. [Figure 7] An exemplary 16-speaker setup in natural view, where nodes are shown as speakers. [Figure 8] FIG. 1 is an energy diagram showing the ratio ̂E / E being constant for perfect energy conservation properties for a decoding matrix obtained using the prior art (Non-Patent Document 14) with N=3. [Figure 9] Sound pressure diagram for a decoding matrix designed according to the prior art (Non-Patent Document 14) with N=3. The pan beam of the center loudspeaker has strong side lobes. [Figure 10]FIG. 1 is an energy diagram showing the ^E / E ratio with fluctuations greater than 4 dB for a decoding matrix obtained using the prior art (Patent Document 1) with N=3. [Figure 11] This is a sound pressure diagram for a decoding matrix designed according to the prior art (Patent Document 1) with N=3, where the pan beam of the center speaker has small side lobes. [Figure 12] 1 is an energy diagram showing the E / E ratio with less than 1 dB fluctuation obtained by a method or apparatus according to the invention. Spatial panning with constant amplitude is perceived with equal loudness. [Figure 13] Sound pressure diagram for a decoding matrix designed using the method according to the invention. The center loudspeaker has a pan beam with small side lobes. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] In general, the present invention relates to rendering (i.e. decoding) sound field formatted audio, such as Higher Order Ambisonics (HOA) audio signals, to loudspeakers, where the loudspeakers are symmetrical or asymmetrical, regularly or irregularly positioned. The audio signal may be suitable to feed more loudspeakers than are available. For example, the number of HOA coefficients may be greater than the number of loudspeakers. The present invention provides an energy-conserving decoding matrix for a decoder with very good directional properties, i.e. the speaker directivity lobes include a stronger directional main lobe and smaller side lobes than the speaker directivity lobes obtained using a normal decoding matrix. Energy-conserving means that the energy in the HOA directional signal is preserved after decoding, so that for example a directional spatial sweep of constant amplitude is perceived with constant loudness.

[0028] 1 is a flow chart of a method according to an embodiment of the present invention. In this embodiment, a method for rendering (i.e., decoding) an HOA audio sound field representation for audio playback uses a decoding matrix that is generated as follows: First, the number L of target loudspeakers, their positions,

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[0035] In one embodiment, the number of loudspeakers L and the number of HOA coefficient channels O 3D =(N+1) 2 Depending on the number of loudspeakers L, the smoothing coefficients can be obtained in one of two different ways: 3D If it is less, a new method for obtaining the smoothing coefficients is used.

[0036] In one embodiment, multiple decoding matrices corresponding to multiple different loudspeaker arrangements are generated and stored for later use, the multiple different loudspeaker arrangements may differ by at least one of the number of loudspeakers, the position of one or more loudspeakers and the order N of the input audio signal. Then, when initializing the rendering system, a matching decoding matrix is ​​determined, retrieved from storage according to the current needs and used for decoding.

[0037] In one embodiment, the decoding matrix D is the mode matrix

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[0042] In the alternative embodiment, the decoding matrix D is the Hermitian transposed modal matrix

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[0046] In one embodiment, the compact singular value decomposition is

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[0050] In one embodiment, the compact singular value decomposition is

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[0054] In one embodiment, two different methods are used to calculate the smoothing coefficients depending on the HOA order N and the number of target speakers L. 3D =(N 2 +1)>L, the smoothing and scaling coefficients

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[0059] In one embodiment, the scaling factor is obtained from the smoothed decoding matrix. In particular, in one embodiment,

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[0061] In the following the full rendering system is described. The main focus of the invention is the initialization phase of the renderer, where the decoding matrix D is generated as described above. Here the main focus is the technique of deriving said one or more decoding matrices, for example for a codebook. To generate the decoding matrices it is known how many target loudspeakers are available and where they are located (their loudspeaker positions).

[0062] 2 shows a flow chart of a method for constructing a mixing matrix G according to one embodiment of the present invention. In this embodiment, an initial mixing matrix with only zeros is generated (21), and the angular orientation Ω s =[θ s ,φ s ] T and radial r s For every virtual source with position [1,Ω s T ] T The three loudspeakers l1, l2, and l3 surrounding are determined (22), where unit radius is assumed.

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[0064] The section below gives a brief introduction to Higher Order Ambisonics (HOA) and defines the signal to be processed, i.e. rendered for loudspeakers.

[0065] Higher Order Ambisonics (HOA) is based on describing the sound field in a compact region of interest where no sound sources are assumed, where the time t and the position x=[r,θ,φ] (in spherical coordinates: radius r, tilt θ, azimuth φ) in the region of interest are T The spatial and temporal behavior of the sound pressure p(t,x) at x is completely determined physically by the homogeneous wave equation. If ω represents the angular frequency, then the Fourier transform of the sound pressure with respect to time, i.e.

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[0068] In formula (2), c s represents the speed of sound, and k=ω / c s represents the angular wave number. Furthermore, j n (·) denotes the nth order spherical Bessel function of the first kind, and Y n m(·) represents the spherical harmonic (SH) function of order n and degree m. The complete information about the sound field is actually given by the sound field coefficients A n m Included in (k).

[0069] It should be noted that SH is in general a complex-valued function, but by approximate linear combination it is possible to obtain real-valued functions and carry out the above expansion in terms of these functions.

[0070] Related to the pressure sound field description in equation (2), the source field can be defined as follows:

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[0073] The signal in the HOA domain can be expressed as the inverse Fourier transform of the source or sound field coefficients in the frequency or time domain. In the following description, we use the time domain representation of a finite number of source field coefficients.

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[0077] A two-dimensional representation of the sound field can be derived by an expansion in circular harmonics. This is done by assuming a fixed tilt angle θ=π / 2, different weights of the coefficients and O 2D This is a special case with the set reduced to m = ±n coefficients. Therefore, all the following considerations also apply to the 2D representation. In that case, the term sphere should be replaced by the term circle.

[0078] In one embodiment, metadata is sent along with the coefficient data, allowing unambiguous identification of the coefficient data. All necessary information to derive the time sample coefficient vector b(t) is given through the transmitted metadata or for a given context. Furthermore, the HOA order N or O 3Dand in some embodiments further indicating near-field recording, s Note that the special flags along with are known at the decoder.

[0079] Next, the rendering of the HOA signal to the loudspeaker is described. This section presents the basic principles of the decoding and some mathematical properties.

[0080] The basic decoding assumes, first, a plane wave loudspeaker signal, and, second, that the distance from the speaker to the origin is negligible.

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[0086] Next, the pseudo-inverse of a matrix is ​​written using Singular Value Decomposition (SVD). One common way to derive the pseudo-inverse is to first use the compact SVD: Ψ=USV H (12) The aim is to calculate

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[0089] In the following, the energy conservation property is described. The signal energy in the HOA region is E=b H b (14) and the corresponding energy in the spatial domain is

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[0091] In general, energy-conserving renderer designs are known in the art. 3D Energy-preserving decoder matrix design for D=VU H (16) Here, the ^S from (13) is forced to be ^S=I, so that it can be dropped in (16). The product D H D=UV H VU H =I and the ratio ^E / E becomes 1. The benefit of this design method is the energy conservation where spatial panning ensures a uniform spatial sound impression without fluctuations in perceived loudness. The drawback of this design is the loss of directional precision and strong loudspeaker beam sidelobes for asymmetric, non-regular speaker positions (see Figures 8-9). The present invention overcomes this drawback.

[0092] Renderer designs for irregularly positioned speakers are also known in the art. 3D and L <O 3D A decoder design method for is described that allows high accuracy rendering of the reproduced directionality. A drawback of this design method is that the derived renderer is not energy-conserving (see Figs. 10-11).

[0093] For spatial smoothing, spherical convolution can be used. This is a spatial filtering process or windowing (convolution) in the coefficient domain. The goal is to minimize the side lobes, the so-called panning lobes. The original HOA coefficients b n m and the zone factor h n 0 The weighted product of n m We are given new coefficients expressed as (Non-Patent Document 5):

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[0099] In the following, further details and embodiments of the disclosed solution are described. First, the renderer architecture is described in terms of its initialization, start-up behavior and processing.

[0100] Every time the loudspeaker setup, i.e. the number of loudspeakers or the position of any loudspeaker with respect to the listening position, changes, the renderer needs to run an initialization process that determines the set of decoding matrices for any HOA order N of the supported HOA input signals, as well as the individual speaker delays d l and speaker gain g l is determined from the distance between the speaker and the listening position. This process is described below. In one embodiment, the derived decoding matrix is ​​stored in a codebook. Each time the HOA audio input characteristics change, the renderer control unit determines the currently active characteristics and selects a matching decoding matrix from the codebook. The codebook key is the HOA order N or equivalently O 3D (see equation (6)).

[0101] The general steps of data processing for rendering are explained with reference to Fig. 3. Fig. 3 shows a block diagram of the processing blocks of the renderer: a first buffer 31, a frequency domain filtering unit 32, a rendering processing unit 33, a second buffer 34, a delay unit 35 for the L channels and a digital-to-analog converter and amplifier 36.

[0102] HOA time sample with time index t and O 3D The HOA coefficient channels b(t) are first stored in a first buffer 31 to form blocks of M samples with block index μ. The coefficients of B(μ) are frequency filtered in a frequency domain filtering unit 32 to obtain a frequency filtered block denoted by ^B(μ). This technique is known to compensate for the distance of spherical loudspeaker sources to be able to handle near-field recordings (Non-Patent Document 3). The frequency filtered block signal denoted by ^B(μ) is then converted in a rendering processing unit 33 into

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[0104] Renderer initialization works as follows:

[0105] First, the number and positions of the speakers do not need to be known. The first step of initialization is to determine the new number of speakers and their associated positions.

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[0109] L distances r l and r max is input to the delay line and gain compensation 35. The number of delay samples for each speaker channel, d l teeth

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[0112] For example, the calculation of the decoding matrix for the above codebook works as follows: The general steps of the method for generating the decoding matrix are shown in Fig. 4. Fig. 5 shows the processing blocks of the corresponding device for generating the decoding matrix in one embodiment. The input is the speaker direction.

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[0115] Speaker Direction

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[0121] The speaker directions and the spherical modeling lattice are input to a mixing matrix construction block 41, which generates the mixing matrix G. The spherical modeling lattice and the HOA order N are input to a mode matrix construction block 42, which generates the mode matrix G.

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[0125] In the mixing matrix construction block 42, G∈R L×S A mixing matrix G of the following is generated. Note that the mixing matrix G is referred to as W in Patent Document 1. The l-th row of the mixing matrix G is

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[0128] In the decoding matrix construction block 43, a compact singular value decomposition of the matrix product of the modal matrix and the transposed mixing matrix is ​​computed. This is an important aspect of the invention, and can be implemented in a variety of ways. In one embodiment, the modal matrix

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[0131] In an alternative embodiment, the mode matrix

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[0134] In one embodiment,

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[0145] L≧O 3D Regarding

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[0153] In one embodiment, the smoothed decoding matrix is ​​scaled. In one embodiment, the smoothing is performed in a decoding matrix smoothing block 44 as shown in FIG. 4a. In a different embodiment, the scaling is performed as a separate step in a matrix scaling block 45 as shown in FIG. 4b.

[0154] In one embodiment, the constant scaling factor is obtained from the decoding matrix. In particular, it can be obtained according to the so-called Frobenius norm of the decoding matrix:

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[0157] 5 shows an apparatus for decoding an audio sound field representation for audio reproduction according to an aspect of the invention, comprising a rendering processing unit 33 with a decoding matrix calculation unit 140 for obtaining the decoding matrix D, which in turn comprises means 1x for obtaining the number L of target speakers and their positions.

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[0167] Figure 6 shows the speaker positions in an exemplary 16-speaker setup in a node schematic where the speakers are shown as nodes to which they are connected. Foreground connections are shown as solid lines and background connections are shown as dashed lines. Figure 7 shows the same speaker setup with 16 speakers in a perspective view.

[0168] In the following, exemplary results obtained with loudspeaker setups as in Fig. 5 and Fig. 6 are described. The energy distribution of the sound signal and especially the ratio ^E / E in dB are shown on two spheres (all test directions). As an example of a loudspeaker pan beam, the center speaker beam (speaker 7 in Fig. 6) is shown. For example, the decoder matrix designed in

[14] with N=3 produces a ratio ^E / E as shown in Fig. 8. This gives almost perfect energy conservation properties, since the ratio ^E / E is almost constant: the difference between the dark areas (corresponding to lower volumes) and the light areas (corresponding to higher volumes) is less than 0.01 dB. However, as shown in Fig. 9, the corresponding pan beam of the center speaker has strong side lobes. This disturbs the spatial perception, especially for off-center listeners.

[0169] On the other hand, the decoder matrix designed in the patent document 1 with N=3 results in a ratio ^E / E as shown in Fig. 9. In the scale used in Fig. 10, the dark areas correspond to lower volumes up to -2 dB and the light areas correspond to higher volumes up to +2 dB. Thus, the ratio ^E / E shows a fluctuation of more than 4 dB. This is disadvantageous, since a spatial pan from, for example, above to a central speaker position at constant amplitude cannot be perceived with equal loudness. However, as shown in Fig. 11, the corresponding pan beam of the central speaker has very small side lobes, which is beneficial for off-center listening positions.

[0170] FIG. 12 shows the energy distribution of the sound signal obtained with a decoder matrix according to the invention, exemplarily N=3 for easy comparison. The scale of the ratio ^E / E (shown on the right side of FIG. 12) ranges from 3.15 to 3.45 dB. Thus, the fluctuation of this ratio is less than 0.31 dB and the energy distribution in the sound field is very even. As a result, any spatial pan with constant amplitude is perceived with equal loudness. As shown in FIG. 13, the pan beam of the center speaker has very small side lobes. This is beneficial for off-center listening positions where side lobes can become audible and annoying. Thus, the present invention provides the combined advantages achievable with the prior art in Non-Patent Document 14 and Patent Document 1, without suffering from their respective disadvantages.

[0171] Please note that whenever a speaker is mentioned in this document, a sound producing device such as a loudspeaker is intended.

[0172] The flowcharts and / or block diagrams in the Figures illustrate the architecture, operation and functionality of possible implementations of systems, methods and computer program products according to various embodiments of the present invention. In this regard, each block in the flowcharts or block diagrams may represent a module, segment or portion of code that includes one or more executable instructions for implementing a specified logical function(s).

[0173] Also, in some alternative implementations, the functions noted in the blocks may occur out of the order noted in the figures. For example, two blocks shown in succession may in fact be executed substantially in parallel, or the blocks may sometimes be executed in the reverse order, or the blocks may be executed in an alternative order, depending on the functionality involved. It is also noted that each block of the block diagrams and / or flowchart illustrations, and combinations of blocks in the block diagrams and / or flowchart illustrations, can be implemented by a special purpose hardware-based system that performs the specified functions or steps, or by a combination of special purpose hardware and computer instructions. Although not explicitly stated, the embodiments of the present application can be used in any combination or subcombination.

[0174] Moreover, as will be appreciated by those skilled in the art, aspects of the present principles may be embodied as a system, method, or computer readable medium. Thus, aspects of the present principles may take the form of an entirely hardware embodiment, an entirely software embodiment (including firmware, resident software, microcode, etc.), or an embodiment combining software and hardware aspects, all of which may be generally referred to herein as a "circuit," "module," or "system." Furthermore, aspects of the present principles may take the form of a computer readable storage medium. Any combination of one or more computer readable storage media may be utilized. A computer readable storage medium, as used herein, is considered to be a non-transitory storage medium given the inherent functionality of storing information therein and providing retrieval of information therefrom.

[0175] Those skilled in the art will also appreciate that the block diagrams presented herein represent conceptual views of illustrative system components and / or circuitry embodying the principles of the invention. Similarly, any flow charts, flow diagrams, state diagrams, and pseudo code may be substantially embodied in a computer-readable storage medium and thus represent various processes that may be executed by a computer or processor, whether or not such a computer or processor is explicitly shown.

[0176] Several aspects will be described. [Aspect 1] 1. A method for rendering a high-order Ambisonics sound field representation for audio reproduction, comprising the steps of: a buffering step (31) of received HOA time samples b(t), whereby blocks of M samples and time index μ are formed; The coefficient B(μ) is filtered to obtain a frequency-filtered coefficient

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Claims

1. 1. A method for decoding a Higher Order Ambisonics (HOA) representation of a sound or sound field, comprising the steps of: Mixing matrix G and mode matrix [0010] A smoothed decoding matrix based on [0025] receiving a mixing matrix G determined based on a position of a spherical modeling lattice and L speakers, and a mode matrix determined based on the spherical modeling lattice and an HOA order N; The smoothed decoding matrix is ​​obtained by subtracting a first decoding matrix from a second decoding matrix using a smoothing factor. [0030] and the first decoding matrix is ​​determined based on a smoothing of [0045] where U and V are unitary matrices, and the compact singular value decomposition of the mode matrix with the transposed mixing matrix is [0050] where S is based on a diagonal matrix with singular value elements, and ^S is a truncated compact singular value decomposition matrix that is an identity matrix or a modified diagonal matrix, the modified diagonal matrix being determined based on the diagonal matrix with singular value elements by replacing singular value elements equal to or greater than a threshold with ones and replacing singular value elements less than the threshold with zeros; rendering the coefficients of the HOA representation from the time domain to the spatial domain based on a rendering matrix D, the rendering matrix D being based on the Frobenius norm of the smoothed decoding matrix. method.

2. A non-transitory computer readable medium storing executable instructions that cause a computer to perform the method of claim 1.

3. 1. An apparatus for decoding a Higher Order Ambisonics (HOA) representation of a sound or sound field for audio reproduction, comprising: a decoder configured to decode coefficients of the HOA sound field representation, the decoder comprising: Mixing matrix G and mode matrix [006] A smoothed decoding matrix based on [0070] a receiver configured to receive a mixing matrix G determined based on a position of a spherical modeling lattice and L speakers, the mixing matrix G being determined based on the spherical modeling lattice and an HOA order N; The smoothed decoding matrix is ​​obtained by subtracting a first decoding matrix from a second decoding matrix using a smoothing factor. [0080] and the first decoding matrix is ​​determined based on a smoothing of [0090] and U and V are based on unitary matrices, The compact singular value decomposition of the mode matrix with the transposed mixing matrix is [0010] a receiver, wherein S is based on a diagonal matrix with singular value elements, and ^S is a truncated compact singular value decomposition matrix that is an identity matrix or a modified diagonal matrix, the modified diagonal matrix being determined based on the diagonal matrix with singular value elements by replacing singular value elements equal to or greater than a threshold with ones and replacing singular value elements less than the threshold with zeros; a renderer configured to render coefficients of the HOA representation from the time domain to the spatial domain based on a rendering matrix D, the rendering matrix D being based on a Frobenius norm of the smoothed decoding matrix. Device.

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