METHODS AND DEVICES FOR RENDERING A HIGHER-ORDER AMBISONIC AUDIO SIGNAL (HOA), AND COMPUTER-READABLE STORAGE MEDIUM

Description

1 / 29 “METHODS AND DEVICES FOR RENDERING A HIGHER-ORDER AMBISONIC AUDIO SIGNAL (HOA), AND COMPUTER-READABLE STORAGE MEDIUM” REFERENCE BY WAY TO RELATED REQUEST

[001] This application claims priority over the following priority applications: US Patent Application No. 63 / 330,687 (reference: D21151USP1), filed April 13, 2022, EP Patent Application No. 22168180.2 (reference: D21151EP), filed April 13, 2022, and IN Patent Application No. 202241005922 (reference: D21151 IN), filed February 3, 2022. TECHNICAL FIELD

[002] This document refers to the efficient rendering of an ambisonic audio signal. BACKGROUND

[003] The sound or sound field in the listening environment of a listener placed in a listening position can be described using an ambisonic (audio) signal. The ambisonic signal can be viewed as a multichannel audio signal, with each channel corresponding to a particular directivity pattern of the sound field at the listener's listening position. An ambisonic signal can be described using a three-dimensional (3D) Cartesian coordinate system, with the origin of the coordinate system corresponding to the listening position, the x-axis pointing forward, the y-axis pointing left, and the z-axis pointing upward.

[004] By increasing the number of audio signals or channels and by increasing the number of corresponding directivity patterns (and corresponding panning functions), one can increase the precision with which a sound field is described. As an example, a first-order ambisonic signal comprises N = 4 channels or waveforms, namely, a W channel indicating an omnidirectional component of the sound field, an X channel describing the sound field with a Petition 870260033113, dated 09 / 04 / 2026, page 13 / 83 2 / 29 dipole directivity pattern corresponding to the x-axis, a Y channel describing the sound field with a dipole directivity pattern corresponding to the y-axis, and a Z channel describing the sound field with a dipole directivity pattern corresponding to the z-axis. A second-order ambisonic signal comprises N = 9 channels including the 4 channels of the first-order ambisonic signal (also called B-format) plus 5 additional channels, an n-order i ambisonic signal. In general, an n-order i ambisonic signal comprises N = (n + l)2 channels including the n2 channels of the (n — 1)-order ambisonic signals plus [(η + I)2— n2] additional channels for additional directivity patterns (when using a 3D ambisonic format), ambisonic signals of order for n > 1 can be called higher-order ambisonic signals (HOA).

[005] A HOA signal can be used to describe a 3D sound field independently of a speaker array, which is used to render the HOA signal. Example speaker arrays comprise headphones or one or more speaker arrays or a virtual reality rendering environment. Consequently, it can be advantageous to provide an HOA signal to an audio renderer, to allow the audio renderer to flexibly adapt the rendering of the HOA signal to different speaker arrays. SUMMARY

[006] This document deals with the technical problem of rendering an ambisonic audio signal in an efficient mode. The technical problem is solved by the independent claims. Preferred examples are described in the dependent claims.

[007] According to a first aspect, a method is described for rendering an ambisonic signal using a loudspeaker array comprising S loudspeakers. The method comprises converting a set of N ambisonic channel signals into a set of unfiltered pre-rendered signals, wherein N > 1 and S > 1 and wherein n may differ from S. Additionally, the method comprises performing compensation of Petition 870260033113, dated 09 / 04 / 2026, page 14 / 83 3 / 29 proximity field called NFC, filter M unfiltered pre-rendered signals from the set of unfiltered pre-rendered signals to provide a set of S filtered speaker channel signals for rendering using the corresponding S speakers. M may depend on the number of speakers S and an order n of a higher-order ambisonic signal (HOA) corresponding to the set of N ambisonic channel signals. More specifically, M = S*(n+l- mJ ), where m1 is the number of non-order n ambisonic channel modes of the HOA signal filtered by an NFC all-pass filter. If no NFC all-pass filter is used, mi = 0. The set of ambisonic channel signals can be a higher-order ambisonic signal (HOA). Additionally, or alternatively, N = (n + l)2, with n being an order of the HOA signal, with n > 1. Additionally, S can be greater than 2. In specific examples, S can be equal to 6 or 16.

[008] In some embodiments, performing NFC filtering of M unfiltered prerendered signals from the set of unfiltered prerendered signals to provide a set of S filtered loudspeaker channel signals for rendering using the corresponding S loudspeakers may include determining a set of M filtered prerendered signals from M unfiltered prerendered signals from the set of unfiltered prerendered signals based on NFC coefficients. In particular, this determination may include frequency domain multiplication of each of the S unfiltered prerendered signals from M unfiltered prerendered signals from the set of unfiltered prerendered signals with an NFC coefficient d(m), for each m, 0 < m < n.Alternatively, this determination may include time-domain convolution of each of the S unfiltered pre-rendered signals from the M unfiltered pre-rendered signals set to the unfiltered pre-rendered signals set with an NFC dm filter for each m, 0 < m < η. The method may additionally include summing the filtered pre-rendered signals and the remaining unfiltered signals corresponding to a loudspeaker, for each loudspeaker S providing the set. Petition 870260033113, dated 09 / 04 / 2026, page 15 / 83 4 / 29 of S filtered speaker channel signals. The number of filtered pre-rendered signals can be n + 1 — m - 1. Note that in the end, the sum will include the m unfiltered pre-rendered signals corresponding to a speaker. This is because the remaining S * m unfiltered pre-rendered signals still need to be made available and considered (although no actual filtering is applied due to the pass-all property) to properly obtain the final S filtered speaker channel signals.

[009] In some embodiments, the method may additionally include determining whether (N — mo) is less than M, where mo > 0 and depends on a number of non-order n ambisonic channel modes of the HOA signal filtered by an NFC pass-all filter, mo may be a number of ambisonic channel indices corresponding to the number of ambisonic channel modes filtered by an NFC pass-all filter. If no NFC pass-all filter is used, mo = 0. Additionally, performing proximity field compensation, called NFC, filtering M unfiltered pre-rendered signals from the set of unfiltered pre-rendered signals to provide a set of S filtered speaker channel signals for rendering using the corresponding S speakers may include performing NFC filtering on N unfiltered pre-rendered signals from the set of unfiltered pre-rendered signals if, in particular and only if, (N — mo) > M or (N — mo) > M.

[010] In some embodiments, before converting a set of N ambisonic channel signals into a set of unfiltered pre-rendered signals, the method may additionally include determining whether (N — mo) is less than M, where mo > 0 and depends on a number of ambisonic channel modes out of order n of the HOA signal filtered by an NFC pass-all filter, mo may be a number of ambisonic channel indices corresponding to the number of ambisonic channel modes filtered by an NFC pass-all filter. If no NFC pass-all filter is used, mo = 0. Depending on the determination of whether (N — mo) is less than M, performing NFC filtering on M unfiltered pre-rendered signals from the set of unfiltered pre-rendered signals Petition 870260033113, dated 09 / 04 / 2026, page 16 / 83 5 / 29 or the inversion of the order of NFC conversion and filtering. In particular, if (N — mo) > M, NFC filtering can be performed on M unfiltered pre-rendered signals from the set of unfiltered pre-rendered signals. Otherwise, the order of NFC conversion and filtering can be reversed. The inversion of the order can be understood as performing NFC filtering on the set of N ambisonic channel signals to generate a set of N filtered ambisonic channel signals, and converting the set of N filtered ambisonic channel signals into the set of S filtered loudspeaker channel signals. In other words, NFC filtering is performed on the HOA signal, if necessary, and conversion is performed on the already filtered HOA signal.

[011] In some embodiments, performing NFC filtering on M unfiltered prerendered signals from the set of unfiltered prerendered signals may include performing time-domain filtering using a digital finite impulse response filter or a digital infinite impulse response filter on each of the M unfiltered prerendered signals individually.

[012] In some embodiments, the method may additionally include determining a reference distance from the set of N ambisonic channel signals, in particular based on a bit stream of the ambisonic signal. Additionally, a filter may be determined, in particular filter coefficients, to perform NFC filtering based on the reference distance.

[013] In some embodiments, the conversion of the set of N ambisonic channel signals into the set of M unfiltered pre-rendered signals may be executable using a matrix multiplication of an ambisonic signal matrix C representing a frame of the set of N ambisonic channel signals with a rendering matrix Rk, for a given loudspeaker k. The rendering matrix Rk for a given loudspeaker k is, in particular, an (n + 1) x N matrix.

[014] According to a second aspect, a rendering device is described for rendering an ambisonic signal using a loudspeaker array. Petition 870260033113, dated 09 / 04 / 2026, page 17 / 83 6 / 29 comprising S speakers. The rendering device is configured to execute the first aspect method and any optional modes pertaining to the first aspect.

[015] According to a third aspect, a software program is described. The software program can be adapted for execution on a processor and to execute the method of the first aspect and any optional embodiments relating to the first aspect.

[016] According to a fourth aspect, a storage medium is described. The storage medium may comprise a software program adapted for execution on a processor and to execute the method of the first aspect and any optional embodiments relating to the first aspect.

[017] According to a fifth aspect, a computer program product is described. The computer program may comprise executable instructions for performing the method of the first aspect and any optional embodiments relating to the first aspect.

[018] According to a sixth aspect, a decoder is described that is configured to decode a bitstream indicative of an ambisonic signal that is to be rendered by a loudspeaker array comprising S loudspeaker, wherein the decoder comprises a rendering device according to the second aspect.

[019] It should be noted that the methods, devices and systems, including their preferred embodiments, as outlined in this patent application, may be used alone or in combination with the other methods, devices and systems disclosed herein. Additionally, all aspects of the methods, devices and systems outlined in this patent application may be arbitrarily combined. In particular, the features of the claims may be combined with each other in an arbitrary manner. Petition 870260033113, dated 09 / 04 / 2026, page 18 / 83 7 / 29 BRIEF DESCRIPTION OF THE FIGURES

[020] The invention is explained below in an exemplary manner with reference to the accompanying drawings, in which figure 1 shows an exemplary rendering device for rendering an ambisonic audio signal; Figure 2a shows an example rendering device with modified NFC processing; Figure 2b shows an example rendering device with flexible NFC processing before or after "ambisonic-to-speaker" conversion; Figure 3 shows a flowchart of an example method for rendering an ambisonic audio signal; and Figure 4 shows a flowchart of an example method for performing NFC filtering on unfiltered pre-rendered signals. DETAILED DESCRIPTION

[021] As outlined above, this document refers to the efficient rendering of ambisonic, in particular HOA signals, as used, for example, in the MPEG-H 3D Audio standard. MPEG-H 3D Audio is an encoding standard that supports channel-based, object-based, and scene-based audio encoding to provide enhanced immersive 3D sound experiences.

[022] The MPEG-H 3D Audio Low Complexity Profile decoder supports all formats, including channel-based audio, object-based audio, and scene-based audio via higher-order ambisonics (HOA). The MPEG-H 3D Audio Low Complexity Profile decoder according to ISO / IEC 23008-3:2019 / AMD 2:2020 also supports the MPEG-H 3D Audio Baseline Profile, which is a subset of the MPEG-H 3D Audio Low Complexity Profile. The ISO / IEC 23008-3:2019 / AMD 2:2020 document is incorporated herein by reference. Petition 870260033113, dated 09 / 04 / 2026, page 19 / 83 8 / 29

[023] As per NC Processing section 12.4.3.4 (Near Field Compensation Processing) of the ISO / IEC 23008-3:2019(E) specification document (which is incorporated by reference) and as shown in the Ambisonic Renderer (in particular HOA) 100 of Figure 1, an NFC filtering block 110 can be used before a “HOA to speaker conversion” block 120. In particular, the Ambisonic Renderer 100 can be configured to receive N ambisonic channel signals (notably, HOA) 111 from a decoding block, wherein the decoding block is configured to generate the ambisonic channel signals 111 from an encoded bitstream. In the case of headphone rendering, the ambisonic channel signals 111 can be provided to an “ambisonic-to-headphone (H2B) conversion” block 130, which can be configured to perform binaural rendering of the N ambisonic channel signals 111.In the case of loudspeaker rendering, the ambisonic channel signals 111 can be supplied to the “ambisonic to loudspeaker conversion” block 120, which is configured to generate S loudspeaker signals 114 for the corresponding S loudspeakers of the loudspeaker array based on the N ambisonic channel signals 111. The loudspeaker signals 114 can be generated using the ambisonic rendering matrix R 113 (which can be determined based on the arrangement of the S loudspeakers).

[024] The processing in the “HOA to speaker conversion” block 120 may, in particular, involve a matrix multiplication: P = RxC where R is the HOA 113 rendering matrix, where C is the HOA 111 decoded output channel matrix (also referred to here as the ambisonic channel signals) and where P is the Renderer 114 output (also referred to here as speaker channel signals), as shown below. ' r0,0 7*0,1 r0,N-2 r0,Nl ' Tl,0 7*1,1 rl,N—2 rl,Nl R = rS—2,0 rS—2,1 rS-2,N-2 rS—2,N—l -rS-l,0 rS-l,l rS—í,N—2 rS-l,Nl- Petition 870260033113, dated 09 / 04 / 2026, p. 20 / 83 9 / 29 c0,0 c0,l c0,L—lc = cl,0 cl,l C1,L-1 ,CN—1,0 Po,o CN—1,1 Po,i CN—1,L—1 Po,L—l P = Pi,o Ρι,ι Pl.Ll .Ps-1,0 Ps-1,1 Ps—1,L—1.

[025] The definitions of the variables, L, S, N are given in Table 1. s Total number of loudspeakers in the loudspeaker layout n HOA order N Number of HOA transport channels, (n + l~)2 for 3D configuration, (2n + 1) for 2D configuration L Length of audio data processing frame (time domain) Table 1

[026] The elements of the HOA 113 rendering matrix, η7· V 0 < i < S and 0 < j < N, are typically scalar weights for a given loudspeaker layout. Consequently, the process of obtaining the final rendered output of a particular channel (i.e., a loudspeaker channel for a particular loudspeaker) can be viewed as a weighted sum of the NOA cJikV channel samples 0 < j < N and 0 < k < L, i.e., where the element pikY0 <i<Se0<k<L da matriz P pode ser visto como uma soma ponderada de cjkV 0 < j < N onde os pesos são as linhas da matriz de renderização R.

[027] As illustrated in Figure 1, the ambisonic channel signals 111 can be subjected to NFC processing in the NFC processing block 110 before rendering, if it is decided in the decision block 101 that NFC processing should be applied. The bitstream that is received from a corresponding ambisonic encoder can indicate in a variable or signal “UsesNfc” whether NFC processing should be applied or not. Alternatively or in addition, the stream Petition 870260033113, dated 09 / 04 / 2026, page 21 / 83 10 / 29 bits can indicate an “NfcReferenceDistance” variable that indicates the reference distance at which sound sources and / or loudspeakers were assumed to be located during encoding.

[028] Decision block 101 can be configured to decide whether or not to apply NFC processing based on the variables “UsesNfc” and / or “NfcReferenceDistance”. In particular, NFC processing can only be applied if the variable “UsesNfc” indicates that NFC processing should be used (for example, using the value “1”). Additionally, NFC processing can only be applied if the variable “NfcReferenceDistance” is greater than the value rmax, which is the maximum distance at which a speaker in the actual speaker array is located from the listener's position. The speakers can be arranged, for example, in one or more circles around the listener's position.

[029] If NFC processing is to be applied, the ambisonic channel signals 111 can be filtered in the NFC processing block 1110 to provide filtered channel signals 112. The filtered channel signals 112 can then be processed in the conversion block 120 to provide the (filtered) speaker channel signals 114. The ambisonic C channel signals 111 can then be replaced by the corresponding filtered channel signals 112 in the aforementioned matrix multiplication.

[030] NFC processing may comprise, in particular, may consist of applying a digital filter, in particular a finite impulse response (FIR) and / or infinite impulse response (IIR) filter, to individual ambisonic channel signals 111. The filter coefficients may be determined based on the variable “NfcReferenceDistance”. For a given HOA order n, the filter coefficients may be equal for all ambisonic channels corresponding to a HOA “mode” m in a given HOA order n, where 0 < m < n. Therefore, for a given HOA order n, a total of (n + 1) different NFC filter sets (corresponding to the number of HOA “modes”) are used. The grouping of ambisonic channels for different HOA orders Petition 870260033113, dated 09 / 04 / 2026, page 22 / 83 11 / 29 from 1 to 6 is presented in Table 2. n Number of NFC filter sets Groups of ambisonic channel signals that correspond to increasing “mode” indices. Channel indexing starts from 0. nn + 1 ambisonic channel indices for modes (m=0),(m=1),... (m=n) 1 2 (0), (1,2, 3) 2 3 (0), (1,2, 3), (4, 5, 6, 7, 8) 3 4 (0), (1,2, 3), (4, 5, 6, 7, 8), (9, 10, 11, 12, 13, 14, 15) 4 5 (0), (1,2, 3), (4, 5, 6, 7, 8), (9, 10, 11, 12, 13, 14, 15), (16, 17, 18, 19, 20, 21, 22, 23, 24) 5 6 (0), (1,2, 3), (4, 5, 6, 7, 8), (9, 10, 11, 12, 13, 14, 15), (16, 17, 18, 19, 20, 21, 22, 23, 24), (25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35) 6 7 (0), (1,2, 3), (4, 5, 6, 7, 8), (9, 10, 11, 12, 13, 14, 15), (16, 17, 18, 19, 20, 21, 22, 23, 24), (25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35), (36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48) Table 2

[031] The NFC processing block 110 can be configured to apply NFC filtering in the time domain. Details regarding NFC processing are described in ISO / IEC 23008-3:20191, notably section 12.4.3.4, which is incorporated here by reference.

[032] It can be shown that the filtering operation that is performed in the NFC processing block 110 and the matrix multiplication operation that is performed Petition 870260033113, dated 09 / 04 / 2026, page 23 / 83 12 / 29 in conversion block 120 can be rearranged (without impacting the final result). Consequently, an alternative configuration 200 of the Ambisonic Renderer 100 can be provided, as illustrated in Figure 2a. In configuration 200, conversion of ambisonic signals into loudspeaker signals is performed in two stages, where in the first stage 220 sets of (n + 1) of S unfiltered pre-rendered loudspeaker signals 211 are obtained from the ambisonic channel signals 111. Parallel processing can be applied to obtain each of the (n + 1) sets of S unfiltered pre-rendered loudspeaker signals. For each of the (n + 1) sets of S unfiltered pre-rendered speaker signal, a conversion is performed by a weighted sum of ambisonic channel signals 111. The weights used to process each set are taken from a subset of the rendering matrix R 113.For example, for each set m, 0 < m < η the subset R(m) of the rendering matrix R 113 can be multiplied with the ambisonic channel signal matrix C 111, that is,. Pu(m) = R(m)· C , \sxlf (SxN) (Nxl) where Pu(m) is the vector of unfiltered pre-rendered loudspeaker signals for an m-mode. Note that for simplicity, the size L=1 in the matrix C is justified during processing in the frequency domain where C becomes a vector of a particular frequency binary.

[033] For example, the weights for the first set (m = 0) of S pre-rendered loudspeaker signals 211 correspond to the first column of the rendering matrix R 113 and the weights for the second set (m = 1) of S pre-rendered loudspeaker signals 211 correspond to a matrix of the second, third and fourth columns of the rendering matrix R 113. Note that this assignment is derived from the grouping as illustrated in Table 2 where for the first set only one ambisonic channel is involved, i.e. the first channel (0), consequently the first column of rendering matrix R 113, whereas for the second set a group of 3 Petition 870260033113, dated 09 / 04 / 2026, page 24 / 83 13 / 29 subsequent ambisonic channels are involved, that is, channels (1, 2, 3), consequently the following three columns of the R 113 rendering matrix.

[034] In the second stage, NFC filtering 210 is applied to the set or a subset of pre-rendered speaker signals 211. In particular, for each of the (n + 1) sets of S unfiltered pre-rendered speaker signals 211 or a subset thereof, NFC filtering is applied individually to provide (n + 1) sets of S filtered pre-rendered speaker signals 213 or a subset thereof. For example, one of the (n + 1) sets of S filtered pre-rendered speaker signals 213 is calculated as Pf(m) = d(m) Pu(m), ^sxí) Τϊχϊί csxif where d(m) is an NC filter coefficient and Pf(m) is the vector of pre-rendered loudspeaker signals filtered for m-mode. Note that for simplicity the multiplication operation assumes frequency domain processing, the corresponding convolution operation is performed in the time domain.

[035] The resulting (n + 1) sets of S filtered prerendered loudspeaker signals 213 are summed in block 212 to obtain the corresponding loudspeaker channel signals 114. If only a subset of the (n + 1) sets is filtered, the subset and the remaining unfiltered signals are summed, i.e., a total of (n + 1) signals for each loudspeaker S. For example, loudspeaker channel signals 114 are calculated as P = Em=oW where P is the vector of loudspeaker channel signals 114.

[036] In other words, in block 212, for each loudspeaker, (n + 1) signals, which correspond to the same particular loudspeaker, are summed, providing a total of S rendered and filtered loudspeaker signals 114. Notably, the loudspeaker channel signals 114 in Figure 2a are identical to the loudspeaker channel signals 114 in Petition 870260033113, dated 09 / 04 / 2026, page 25 / 83 14 / 29 figure 1.

[037] If NFC processing is not required in this configuration, a direct conversion to the speaker channel signals 114 can also be done by processing the ambisonic channel signals 114 with the R rendering matrix 113.

[038] In the configuration of Figure 1, NFC processing is applied to N ambisonic channel signals 111, whereas in the configuration of Figure 2a, NFC processing is applied to S * (n + 1) signals. Consequently, the configuration of Figure 2a is computationally more efficient than the configuration of Figure 1 if the following holds true: S * (n + 1) < N or S < (n + 1) for the 3D configuration. Note that this document mainly describes the 3D configuration, but it can easily be extended to the 2D configuration. Consequently, in the case of an NFC “all-pass” filter being applied in one of the modes, as is commonly done for m = 0 for example, the above condition must be adjusted, for example, S * n < N — 1.More generally, the condition can be expressed as S * (n + 1 - < N - m0, where mi is a number of ambisonic channel modes, out of order n of the HOA signal, filtered by an NFC pass-all filter, and mo is a number of ambisonic channel indices corresponding to the number of ambisonic channel modes mi.

[039] Table 3 illustrates the reduction in filtration operations that can be obtained for different scenarios. (n,S) Number of channels that are subjected to NFC filtering % reduction in operations Fig. 1 configuration Fig. 2a configuration (2,4) 9 12 -33.33 (2,2) 9 6 33.33 (3,2) 16 8 50.00 (4,3) 25 15 20.00 Petition 870260033113, dated 09 / 04 / 2026, page 26 / 83 15 / 29 (5.5) 36 30 16.66 (6.6) 49 42 14.28 (7.6) 64 48 25.00 (8.6) 81 54 33.33 (9.6) 100 60 40.00 (10.6) 121 66 45.45 Table 3

[040] Consequently, the configuration in Figure 2a is efficient at relatively high ambisonic orders n, for the relatively common loudspeaker layout with S = 6 loudspeakers supported by the MPEG-H LC decoder. In general, the configuration in Figure 2a is more efficient when the number N of HOA channels is higher than the number S * (n + 1) of loudspeakers in the target loudspeaker layout.

[041] Figure 2b illustrates an Ambisonic Renderer 300 that makes use of a decision unit 201 that is configured to change the order of conversion processing and NFC processing, depending on the number N of ambisonic channels and the number S of speaker channels. In the case of S > (n + 1), NFC processing (in block 110) can be executed before conversion processing (in block 120). Conversely, in the case of S < (n + 1), NFC processing (in block 210) can be executed subsequent to conversion processing (in block 220). As a result, particularly efficient processing can be obtained as illustrated in Table 4. (n,S) Number of channels that are subjected to NFC filtering % reduction in Fig. 1 configuration Fig. 2b configuration (2,4) 9 9 0.00 (2,2) 9 6 33.33 Petition 870260033113, dated 09 / 04 / 2026, page 27 / 83 16 / 29 (3,2) 16 8 50.00 (4,3) 25 15 20.00 (5,5) 36 30 16.66 (6,6) 49 42 14.28 (7, 6) 64 48 25.00 (8, 6) 81 54 33.33 (9, 6) 100 60 40.00 (10, 6) 121 66 45.45 Table 4

[042] Figure 3 shows a flowchart of an example (computer-implemented) method 400 for rendering an ambisonic audio signal using a loudspeaker array comprising S loudspeakers. The ambisonic audio signal can be provided in a bitstream. The method 400 can be executed by a decoder that is configured to decode the bitstream. In particular, a set of N ambisonic channel signals 111 can be derived from the bitstream. The set of N ambisonic channel signals 111 can be a higher-order ambisonic signal (HOA). The number N of ambisonic channel signals 111 can be N = (n + l)2, with n being the order of the ambisonic signal, for example, with n > 1.

[043] Method 400 may comprise converting 401 the set of N ambisonic channel signals 111 into a set of unfiltered pre-rendered signals 211. For example, the size of the set of unfiltered pre-rendered signals 211 is equal to S * (n + 1). Typically, N > 1 and typically S > 1. In particular, S > 2, for example, S = 6 or S = 16. Consequently, the loudspeaker channel signals 114 may be derived from the HOA signal.

[044] The conversion of the set of N ambisonic channel signals 111 into the set of unfiltered pre-rendered signals 211 may be executable and / or may be Petition 870260033113, dated 09 / 04 / 2026, page 28 / 83 17 / 29 executed using a matrix multiplication of an ambisonic signal matrix C (representing a frame of the set of N ambisonic channel signals 111) with a rendering matrix R(m), where 0 < m < n, for each of the “mode” m given the ambisonic order η. The rendering matrix R(m), for each “mode” m, can be an S x N matrix full of zeros, but with non-zero elements from a subset of column vectors of the rendering matrix R. The column vector indices are taken from Table 2. For example, for n = 2, the non-zero elements of the rendering matrix R(m), for m = 2 are the (5th, 6th, 7th, 8th, 9th) column vectors of the rendering matrix R that correspond to the ambisonic channel indices in the group (4, 5, 6, 7, 8) of Table 2. Note that the column vector indices are merely an offset (+1) of the ambisonic channel indices and are placed in the same positions in R(m) as in R.In a real-world implementation, it is not necessary to construct such a redundant matrix; multiplications in the element-wise direction are sufficient to perform this operation.

[045] Consequently, the conversion of the HOA signal into different loudspeaker channel signals can be performed by calculating linear combinations of the different ambisonic channel signals using different sets of weights (from the R rendering matrix).

[046] Additionally, method 400 comprises performing 402 proximity field compensation (NFC), filtering M unfiltered pre-rendered signals 211 from the set of unfiltered pre-rendered signals 211 to provide a set of M filtered pre-rendered signals 213. For example, M is equal to S * (n + 1). An example of step 402 is shown in figure 4.

[047] Figure 4 shows a flowchart of an example method (computer implemented) 500 to perform NFC filtering of the set of M unfiltered prerendered signals.

[048] In step 501, a set of M filtered pre-rendered signals 213 is determined from the set of unfiltered pre-rendered signals 211 based Petition 870260033113, dated 09 / 04 / 2026, page 29 / 83 18 / 29 in NFC coefficients. In particular, the unfiltered prerendered signals 211 from the set of unfiltered prerendered signals 211 can be multiplied by corresponding NFC filter coefficients to provide the set of M filtered prerendered signals 213.

[049] In step 502, for each speaker, the filtered pre-rendered signals 213 corresponding to the speaker are summed to provide the set of filtered speaker channel signals 114. The set of filtered speaker channel signals 114 can be rendered for the corresponding speakers.

[050] Method 400 may comprise providing the filtered S speaker channel signals 114 to the corresponding S speakers, respectively. Alternatively, or in addition, method 400 may comprise rendering the filtered S speaker channel signals 114 using the corresponding S speakers, respectively.

[051] Performing NFC filtering on the set of unfiltered pre-rendered signals 211 may comprise performing time-domain filtering using a finite digital impulse response (FIR) filter and / or an infinite digital impulse response (IIR) filter on each of the M unfiltered pre-rendered signals 211 individually. The filter for NFC processing may be determined based on data provided in the bitstream of the ambisonic audio signal. In particular, method 400 may comprise determining a reference distance from the set of N ambisonic channel signals 111, in particular based on the bitstream of the ambisonic signal. Additionally, method 400 may comprise determining the filter, in particular filter coefficients, to perform NFC processing based on the reference distance.

[052] NFC processing can be used to compensate for the fact that loudspeakers that are positioned at a limited distance from the listener's position do not emit ideal planar sound waves, in which the sound field representation Petition 870260033113, dated 09 / 04 / 2026, page 30 / 83 The 19 / 29 model used for ambisonics typically assumes the emitted sound waves to be planar waves.

[053] Consequently, a method 400 is described, which applies NC processing to loudspeaker channel signals (in contrast to applying NFC processing to ambisonic channel signals). This can lead to substantial reductions in computational complexity without impacting perceptual quality.

[054] The method may further comprise determining whether the number S of speakers is less than or equal to (and equal to) the number (n + 1), n ​​being the HOA order. M may be S * (n + 1). NFC filtering may be performed on the set of unfiltered prerendered signals S * (n + 1) 211 if, in particular, only if, (n + 1) > S or (n + 1) > S. as a result of this, the computational complexity may be reduced.

[055] Consequently, the method can involve determining whether the number S of loudspeakers is less than or equal to the number (n + 1), n ​​being the order HOA. Depending on this, NC filtering can be performed either on the set of unfiltered prerendered signals S * (n + 1) 211 or on the set of N ambisonic channel signals 111. In particular, NFC filtering can be performed on the set of unfiltered prerendered signals S * (n + 1) 211 if (n + 1) > S. Conversely, NFC filtering can be performed on the set of N ambisonic channel signals 111 if (n + 1) < S. In particular, if (n + 1) < S, method 400 can perform NFC filtering on the set of N ambisonic channel signals 111 to generate a set of N filtered ambisonic channel signals 112, and convert the set of N filtered ambisonic channel signals 112 into the set of S filtered loudspeaker channel signals 114.Consequently, in the case of (n + 1) < S, NFC filtering can be selectively performed before the “ambisonic to loudspeaker” conversion. As a result, computational complexity can be reduced in a particularly extensive way.

[056] Consequently, method 400 can flexibly perform NFC filtering before or after the “ambisonic to loudspeaker” conversion. By doing so, Petition 870260033113, dated 09 / 04 / 2026, p. 31 / 83 20 / 29, computational complexity can be reduced.

[057] In the present document, a method and a rendering device have been described that allow ambisonic signals, in particular HOA, to be rendered by a loudspeaker layout in a particularly efficient way.

[058] It should be noted that the description and drawings merely illustrate the principles of the proposed methods and systems.Those skilled in the art will be able to implement various arrangements which, while not explicitly described or shown herein, embody the principles of the invention and are included within its spirit and scope. Additionally, all examples and embodiments outlined herein are primarily intended expressly as being for explanatory purposes only to assist the reader in understanding the principles of the proposed methods and systems. Furthermore, all statements in the present invention providing principles, aspects and embodiments of the invention, as well as specific examples thereof, are intended to encompass their equivalents.

[059] Several aspects of the present invention can be recognized from the following enumerated example embodiments (EEEs).

[060] EEE1) A method (400) for rendering an ambisonic signal using a loudspeaker array comprising S loudspeakers, wherein the method (400) comprises - converting (401) a set of N ambisonic channel signals (111) into a set of unfiltered pre-rendered signals (211), wherein N > 1 and S > 1. e. - perform (402) proximity field compensation, called NFC, filtering M unfiltered prerendered signals (211) from the set of unfiltered prerendered signals (211) to provide a set of S filtered speaker channel signals (114) for rendering using the corresponding S speakers.

[061] EEE2) EEE2 method (400), wherein the execution (402) of NFC filtering of M unfiltered pre-rendered signals (211) from the set of pre-rendered signals Petition 870260033113, dated 09 / 04 / 2026, page 32 / 83 21 / 29 unfiltered (211) to provide a set of filtered S speaker channel signals (114) for rendering using the corresponding S speakers comprises, - determine a set of M filtered pre-rendered signals from the set of M unfiltered pre-rendered signals based on NFC coefficients; and - sum the filtered pre-rendered signals and the remaining unfiltered pre-rendered signals, corresponding to a speaker, for each speaker S provide the set of S filtered speaker channel signals (114).

[062] EEE3) Method (400) according to any previous EEE, wherein M depends on the number of loudspeakers S and an order n of a higher-order ambisonic signal (HOA) corresponding to the set of N ambisonic channel signals (111).

[063] EEE4) Method (400) according to any previous EEE, wherein: M = S*(n+l — mi is a number of non-order n ambisonic channel modes of the HOA signal filtered by an NFC pass-all filter.

[064] EEE5) Method (400) according to EEEs 4, when depending on EEE2, wherein the filtered pre-rendered signals and remaining unfiltered pre-rendered signals, corresponding to a loudspeaker, are a number of n + 1 - mi and mi signals, respectively.

[065] EEE6) Method (400) according to any of the EEEs 4 to 5, where mi = 0.

[066] EEE7) Method (400) according to any of EEEs 3 to 6, when depending on EEE 2, wherein the determination of a set of M filtered prerendered signals from the set of unfiltered prerendered signals based on NFC coefficients comprises - frequency multiplication in the domain of each of the S unfiltered prerendered signals of the M unfiltered prerendered signals (211) of the set of unfiltered prerendered signals with an NFC coefficient d(m), for each m, 0 < Petition 870260033113, dated 09 / 04 / 2026, page 33 / 83 22 / 29 m < η; - or time-domain convolution of each of the S unfiltered prerendered signals of the M unfiltered prerendered signals (211) of the set of unfiltered prerendered signals with an NFC filter dm, for each m, 0 < m < n .

[067] EEE8) Method (400) according to any of EEEs 3 to 7, wherein method (400) comprises - determining whether N — mo) is less than M, wherein mo > 0 and depends on a number of non-order ambisonic channel modes of the HOA signal filtered by an NFC all-pass filter; and wherein the execution (402) of proximity field compensation, called NFC, filtering M unfiltered pre-rendered signals (211) from the set of unfiltered pre-rendered signals (211) to provide a set of S filtered loudspeaker channel signals (114) for rendering using the corresponding S loudspeakers comprises - perform (402) NFC filtering on M unfiltered prerendered signals (211) from the set of unfiltered prerendered signals (211) if, in particular only if (N — mo) > M or (N — mo) > M.

[068] EEE9) Method (400) according to any of EEEs 3 to 8, wherein before conversion (401) of a set of N ambisonic channel signals (111) into a set of unfiltered pre-rendered signals (211), method (400) further comprises - determine if (N — mo) is less than M, where mo > 0 and depends on a number of non-order n ambisonic channel modes of the HOA signal filtered by an NFC all-pass filter; and - depending on the same, perform (402) NFC filtering on M unfiltered prerendered signals (211) from the set of unfiltered prerendered signals (211) or reverse the order of conversion and NFC filtering. Petition 870260033113, dated 09 / 04 / 2026, page 34 / 83 23 / 29

[069] EEE10) Method (400) according to EEE9, where: - execute (402) NFC filtering on M unfiltered pre-rendered signals (211) from the set of unfiltered pre-rendered signals (211) if, (N — mo) > M; and - reverse the order of NFC conversion and filtering if (N — mo) < M.

[070] EEE11) Method (400) according to any of the EEEs 9 to 10, wherein the inversion of the order of conversion and NFC filtering comprises - perform NFC filtering on the set of N ambisonic channel signals (111) to generate a set of N filtered ambisonic channel signals (112); and - convert the set of N filtered ambisonic channel signals (112) into the set of S filtered loudspeaker channel signals (114).

[071] EEE12) Method (400) according to any of the EEEs 8 to 12, wherein mo is a number of ambisonic channel indices corresponding to the number of ambisonic channel modes filtered by an NFC pass-all filter.

[072] EEE13) Method (400) according to EEE 12, where mo = 0.

[073] EEE14) Method (400) according to any previous EEE, wherein the execution (402) of NFC filtering on M unfiltered prerendered signals (211) of the set of unfiltered prerendered signals (211) comprises performing time-domain filtering using a digital finite impulse response filter or a digital infinite impulse response filter on each of the M unfiltered prerendered signals (211) individually.

[074] EEE15) Method (400) in accordance with any previous EEE, wherein the method comprises - determine a reference distance from the set of N ambisonic channel signals (111), in particular based on a bit stream of the ambisonic signal; and - Determine a filter, in particular the coefficients of a filter, to perform NFC filtering based on the reference distance.

[075] EEE16) Method (400) in accordance with any previous EEEs, wherein: Petition 870260033113, dated 09 / 04 / 2026, page 35 / 83 24 / 29 - the set of N ambisonic channel signals (111) is a higher-order ambisonic signal (HOA); and / or - N = (n+l)2, with n being an order of the HOA signal, with n > 1,

[076] EEE17) Method (400) in accordance with any previous EEEs, wherein: - S > 2; and / or - S = 6; or - S = 16.

[077] EEE18) Method (400) in accordance with any previous EEEs, wherein: - the conversion (401) of the set of N ambisonic channel signals (111) into the set of M unfiltered pre-rendered signals (211) is executable using a matrix multiplication of an ambisonic signal matrix C representing a frame of the set of N ambisonic channel signals (111) with a rendering matrix Rk, for a given speaker k. The rendering matrix Rk for a given speaker k is, in particular, an (n + 1) x N matrix.

[078] EEE19) Computer program product comprising instructions which, when executed by a computer, cause the computer to perform method (400) in accordance with any of the preceding EEEs.

[079] EEE20) A rendering device (100) for rendering an ambisonic signal using a loudspeaker array comprising S loudspeakers, wherein the rendering device (100) is configured for - convert (401) a set of N ambisonic channel signals (111) into a set of unfiltered pre-rendered signals (211), where N > 1 and S > 1; and - perform (402) proximity field compensation, called NFC, filtering M unfiltered prerendered signals (211) from the set of unfiltered prerendered signals (211) to provide a set of S filtered speaker channel signals (114) for rendering using the corresponding S speakers. Petition 870260033113, dated 09 / 04 / 2026, page 36 / 83 25 / 29

[080] EEE21) A method (400) for rendering an ambisonic signal using a loudspeaker array comprising S loudspeakers, wherein the method (400) comprises - convert (401) a set of N ambisonic channel signals (111) into a set of unfiltered loudspeaker channel signals (214), wherein N > 1 and S > 1; and - perform (402) proximity field compensation, called NFC, filtering of the set of unfiltered S speaker channel signals (214) to provide a set of filtered S speaker channel signals (114) for rendering using the corresponding S speakers.

[081] EEE22) Method (400) according to EEE 21, wherein method (400) comprises - determine whether the number N of ambisonic channel signals (111) is greater or not than the number S of loudspeakers; and - perform (402) NFC filtering on the set of unfiltered (214) speaker channel signals if, in particular only if, N>S or N>S.

[082] EEE23) Method (400) according to any of the EEEs 21 to 22, wherein method (400) comprises - determine whether the number N of ambisonic channel signals (111) is greater or not than the number S of loudspeakers; and - depending on the same, perform (402) NFC filtering on the set of S unfiltered speaker channel signals (214) or perform NFC filtering on the set of N ambisonic channel signals (111).

[083] EEE24) Method (400) according to EEE 23, wherein method (400) comprises - perform (402) NFC filtering on the set of unfiltered S speaker channel signals (214) if, N>S; and - perform NFC filtering on the set of N ambisonic channel signals (111), if Petition 870260033113, dated 09 / 04 / 2026, page 37 / 83 26 / 29 N< S.

[084] EEE25) Method (400) according to any of the EEEs 23 to 25, wherein method (400) comprises, if N <S, - perform NFC filtering on the set of N ambisonic channel signals (111) to generate a set of N filtered ambisonic channel signals (112); and - convert the set of N filtered ambisonic channel signals (112) into the set of S filtered loudspeaker channel signals (114).

[085] EEE26) Method (400) according to any of EEEs 21 to 25, wherein performing NFC filtering on the set of S unfiltered loudspeaker channel signals (214) comprises performing time-domain filtering using a digital finite impulse response filter or a digital infinite impulse response filter on each of the S unfiltered loudspeaker channel signals (214) individually.

[086] EEE27) Method (400) according to any of the EEEs 21 to 26 in which the method comprises - determine a reference distance from the set of N ambisonic channel signals (111), in particular based on a bit stream of the ambisonic signal; and - Determine a filter, in particular the coefficients of a filter, to perform NFC processing based on the reference distance.

[087] EEE28) Method (400) according to any of the EEEs 21 to 27 where - the set of N ambisonic channel signals (111) is a higher-order ambisonic signal; and / or - N = (n +1 )2, with n being an order of the ambisonic signal, with n > 1.

[088] EEE29) Method (400) according to any of the EEEs 21 to 28 in which - S > 2; and / or - S = 6; or Petition 870260033113, dated 09 / 04 / 2026, page 38 / 83 27 / 29 - S = 16.

[089] EEE30) Method (400) according to any of the EEEs 21 to 29 where - the conversion (401) of the set of N ambisonic channel signals (111) into the set of S unfiltered loudspeaker channel signals (214) is executable using a matrix multiplication of an ambisonic signal matrix C representing a frame of the set of N ambisonic channel signals (111) with a rendering matrix R to provide a loudspeaker signal matrix P representing a frame of the set of S unfiltered loudspeaker channel signals (214) and The rendering matrix R is, in particular, an S x N matrix.

[090] EEE31) Method (400) according to any of the EEEs 21 to 30 in which method (400) comprises - test the filtered S speaker channel signals (114) for the corresponding S speakers, respectively and / or - render the filtered S speaker channel signals (114) using the corresponding S speakers, respectively.

[091] EEE32) A method (500) for rendering an ambisonic signal using a loudspeaker array comprising S loudspeakers, wherein the method (500) comprises - perform (501) joint synthesis and render into a set of ambisonic ambience signals (301), to determine a set of S ambience loudspeaker signals; - perform (502) joint synthesis and render into a set of predominant sound signals (302), to determine a set of S predominant speaker signals; and - combine (503) the set of S ambient loudspeaker signals and the set of S predominant loudspeaker signals to provide a set of S channel signals Petition 870260033113, dated 09 / 04 / 2026, page 39 / 83 28 / 29 unfiltered loudspeaker (214), where S>1; and - perform (504) proximity field compensation, called NFC, filtering of the set of unfiltered S speaker channel signals (214) to provide a set of filtered S speaker channel signals (114) for rendering using the corresponding S speakers.

[092] EEE33) Computer program product comprising instructions which, when executed by a computer, cause the computer to perform method (300, 400) in accordance with any of EEEs 21 to 32.

[093] EEE34) A rendering device (100) for rendering an ambisonic signal using a loudspeaker array comprising S loudspeakers, wherein the rendering device (100) is configured for - convert a set of N ambisonic channel signals (111) into a set of unfiltered loudspeaker channel signals (214), where N > 1 and S > 1. and - perform proximity field compensation, called NFC, filtering the set of unfiltered S speaker channel signals (214) to provide a set of filtered S speaker channel signals (114) for rendering using the corresponding S speakers.

[094] EEE35) A rendering device for rendering an ambisonic signal using a loudspeaker array comprising S loudspeakers, wherein the rendering device is configured to: - perform joint synthesis and rendering on a set of ambisonic ambience signals (301), to determine a set of S ambience loudspeaker signals; - perform joint synthesis and rendering on a set of predominant sound signals (302), to determine a set of S predominant speaker signals; and - combine the set of S ambient speaker signals and the set of S Petition 870260033113, dated 09 / 04 / 2026, page 40 / 83 29 / 29 predominant loudspeaker signals to provide a set of S unfiltered loudspeaker channel signals (214), where S>1; and - perform proximity field compensation, called NFC, filtering the set of unfiltered S speaker channel signals (214) to provide a set of filtered S speaker channel signals (114) for rendering using the corresponding S speakers.

[095] EEE36) A decoder (300) configured to decode a bit stream indicative of an ambisonic signal to be rendered by a loudspeaker arrangement comprising S loudspeaker, wherein the decoder (300) comprises a rendering device (100) according to any of EEEs 34 to 35. Petition 870260033113, dated 09 / 04 / 2026, page 41 / 83

Claims

1 / 5 CLAIMS 1. Method (400) for rendering a higher-order ambisonic (HOA) signal using a loudspeaker array comprising S loudspeakers, CHARACTERIZED in that the method (400) comprises - converting (401) a set of N ambisonic channel signals (111) into a set of unfiltered pre-rendered signals (211); wherein S > 1 and N > 1, since N=(n+1)2 for 3D configuration and N=(2n+1) for 2D configuration, wherein n is the ambisonic signal order, such that for HOA signals, n>1; and - perform (402) proximity field compensation, called NFC, filtering M unfiltered prerendered signals (211) from the set of unfiltered prerendered signals (211) to provide a set of S filtered loudspeaker channel signals (114) for rendering using the corresponding S loudspeakers, wherein M = S*(n + l- and m1 is a number of ambisonic channel modes out of order n of the filtered HOA signal by an NFC pass-all filter.

2. Method (400), according to claim 1, CHARACTERIZED in that performing (402) NFC filtering of M unfiltered prerendered signals (211) from the set of unfiltered prerendered signals (211) to provide a set of S filtered speaker channel signals (114) for rendering using the corresponding S speakers comprises, - determining a set of M filtered prerendered signals from the set of M unfiltered prerendered signals based on NFC coefficients; and - summing the filtered prerendered signals and remaining unfiltered prerendered signals, corresponding to a speaker, for each speaker S to provide the set of S filtered speaker channel signals (114).

3. Method (400), according to claim 1 or 2, CHARACTERIZED in that M depends on the number of loudspeakers S and an order n of a higher-order ambisonic signal (HOA) corresponding to the set of N ambisonic channel signals Petition 870260033113, dated 09 / 04 / 2026, page 42 / 83 2 / 5 (111).

4. Method (400), according to claim 1, CHARACTERIZED in that the filtered pre-rendered signals and remaining unfiltered pre-rendered signals, corresponding to a loudspeaker, are a number of n + 1 - m1 and m1 signals, respectively.

5. Method (400), according to claim 1 or 4, CHARACTERIZED in that m1 = 0.

6. Method (400), according to any one of claims 3 to 5, when dependent on claim 2, CHARACTERIZED in that the determination of a set of M filtered prerendered signals from the set of unfiltered prerendered signals based on NFC coefficients comprises - frequency domain multiplication of each of the S unfiltered prerendered signals of the M unfiltered prerendered signals (211) of the set of unfiltered prerendered signals with an NFC coefficient d(m), for each m, 0 < m < n ; - or time domain convolution of each of the S unfiltered prerendered signals of the M unfiltered prerendered signals (211) of the set of unfiltered prerendered signals with an NFC filter dm, for each m, 0 < m < n . 7.Method (400), according to any one of claims 3 to 6, CHARACTERIZED in that the method (400) comprises - determining whether (N - m0) is less than M, wherein m0 > 0 and depends on a number of non-order ambisonic channel modes of the HOA signal filtered by an NFC filter passes all; and wherein the implementation (402) of proximity field compensation, called NFC, filtering M unfiltered pre-rendered signals (211) from the set of unfiltered pre-rendered signals (211) to provide a set of filtered loudspeaker channel signals (114) for rendering using the corresponding S loudspeakers Petition 870260033113, dated 09 / 04 / 2026, p. 43 / 83 3 / 5 comprises - perform (402) NFC filtering on M unfiltered prerendered signals (211) from the set of unfiltered prerendered signals (211) if, in particular only if (N — m0) > Mou (N- m0) > M.

8. Method (400), according to any one of claims 3 to 7, CHARACTERIZED in that before conversion (401) of a set of N ambisonic channel signals (111) into a set of unfiltered prerendered signals (211), the method (400) further comprises - determining whether (N - m0) is less than M, wherein m0 > 0 and depends on a number of out-of-order ambisonic channel modes of the HOA signal filtered by an NFC filter passes all; and - depending on the same, performing (402) NFC filtering on M unfiltered prerendered signals (211) from the set of unfiltered prerendered signals (211) or reversing the order of conversion and NFC filtering.

9. Method (400), according to claim 8, CHARACTERIZED in that - performs (402) NFC filtering on M unfiltered pre-rendered signals (211) from the set of unfiltered pre-rendered signals (211), if (N - m0) > M; and - reverses the order of conversion and NFC filtering, if (N - m0) < M.

10. Method (400), according to claim 8 or 9, CHARACTERIZED in that the inversion of the order of NFC conversion and filtering comprises - performing NFC filtering on the set of N ambisonic channel signals (111) to generate a set of N filtered ambisonic channel signals (112); and - converting the set of N filtered ambisonic channel signals (112) into the set of S filtered loudspeaker channel signals (114).

11. Method (400), according to any one of claims 7 to 10, CHARACTERIZED in that mo is a number of ambisonic channel indices Petition 870260033113, dated 09 / 04 / 2026, page 44 / 83 4 / 5 corresponding to the number of ambisonic channel modes filtered by an NFC pass-all filter.

12. Method (400), according to claim 11, CHARACTERIZED in that m0 = 0.

13. Method (400), according to any one of claims 1 to 12, CHARACTERIZED in that performing (402) NFC filtering on M unfiltered prerendered signals (211) from the set of unfiltered prerendered signals (211) comprises performing time-domain filtering using a finite digital impulse response filter or an infinite digital impulse response filter on each of the M unfiltered prerendered signals (211) individually.

14. Method (400), according to any one of claims 1 to 13, CHARACTERIZED in that the method comprises - determining a reference distance from the set of N ambisonic channel signals (111), in particular based on a bit stream of the ambisonic signal; and - determining a filter, in particular coefficients of a filter, to perform NFC filtering based on the reference distance.

15. Method (400), according to any one of claims 1 to 14, CHARACTERIZED in that: - S > 2; and / or - S = 6; or - S = 16.

16. Method (400), according to any one of claims 1 to 15, CHARACTERIZED in that: - the conversion (401) of the set of N ambisonic channel signals (111) into the set of M unfiltered pre-rendered signals (211) is executable using a matrix multiplication of an ambisonic signal matrix C representing a frame of the set of N ambisonic channel signals (111) with a rendering matrix Rk, Petition 870260033113, 09 / 04 / 2026, p. 45 / 83 5 / 5 for a given loudspeaker k; - the rendering matrix Rk for a given loudspeaker k is, in particular, an (n + 1) x N matrix.

17. Computer-readable storage medium, CHARACTERIZED in that it comprises instructions which, when executed by a computer, cause the computer to perform method (400) as defined in any one of claims 1 to 16.

18. Rendering device (100) for rendering a higher-order ambisonic signal (HOA) using a loudspeaker array comprising S loudspeakers, CHARACTERIZED in that the rendering device (100) is configured to - convert (401) a set of N ambisonic channel signals (111) into a set of unfiltered pre-rendered signals (211); wherein S > 1 and N > 1, since N=(n+1)2 for 3D configuration and N=(2n+1) for 2D configuration, where n is the ambisonic signal order, such that for HOA signals, n>1;and - perform (402) proximity field compensation, called NFC, filtering M unfiltered prerendered signals (211) from the set of unfiltered prerendered signals (211) to provide a set of S filtered loudspeaker channel signals (114) for rendering using the corresponding S loudspeakers, wherein M = S*(n + l- and m1 is a number of non-order n ambisonic channel modes of the filtered HOA signal by an NFC pass-all filter. Petition 870260033113, dated 09 / 04 / 2026, p. 46 / 83;

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