Methods, apparatus and systems for representation, encoding, and decoding of discrete directivity information

Abstract

To provide a method for processing audio contents that include directivity information on at least one sound source.SOLUTION: A method for decoding audio contents: receives a bitstream containing the audio contents; extracts a first set of directivity unit vectors and an associated first directivity gain from the bitstream; determines the number of vectors for placement on a surface of a 3D sphere as count number based on desired representation accuracy; uses a predetermined placement algorithm to generate a second set of second directivity unit vectors, for distributing the number of unit vectors on the surface of the 3D sphere; determines a related second directivity gain, based on the first directivity gain for the second directivity unit vectors; and determines a target directivity gain for a target directivity unit vector, based on the second directivity gain, for the target directivity unit vector indicating a direction of a listener's position from a sound source.SELECTED DRAWING: Figure 11

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS This application claims priority to the following priority applications: U.S. Provisional Application No. 62 / 869,622, filed July 2, 2019 (Reference No. D19038USP1), and European Application No. 19183862.2, filed July 2, 2019 (Reference No. D19038EP), the disclosures of both applications being incorporated herein in their entireties by reference.

[0002] The present disclosure relates to providing methods and apparatus for processing and encoding audio content that includes discrete directivity information (directional data) for at least one sound source. In particular, the present disclosure relates to the representation, encoding, and decoding of discrete directivity information. [Background technology]

[0003] Real-world sound sources, whether natural or artificial (e.g., loudspeakers, musical instruments, voices, mechanical devices), radiate sound non-isotropically. Characterizing the complex radiation patterns (or "directivity") of sound sources can be crucial for proper rendering, especially in interactive environments such as video games and virtual / augmented reality applications. In these environments, users can typically interact with directional audio objects by walking around them, thus changing the user's auditory perspective of the generated sound. Users may also be able to grab and dynamically rotate virtual objects, again requiring rendering of the corresponding sound source radiation patterns in different directions. In addition to more realistic rendering of the direct propagation effect from the sound source to the listener, radiation characteristics also affect reverberant sound, as they play a large role in higher-order acoustic coupling between the sound source and its environment (e.g., virtual environments in video games). This, in turn, affects other spatial cues, such as perceived distance.

[0004] The radiation pattern of the sound source, or a parametric representation of it, needs to be transmitted as metadata to a six degree of freedom (6DoF) audio renderer. The radiation pattern can be represented, for example, by a spherical harmonic decomposition or discrete vector data.

[0005] However, direct application of traditional discrete directional representations has proven to be suboptimal for 6DoF rendering. Summary of the Invention [Problem to be solved by the invention]

[0006] Therefore, there is a need for methods and apparatus for improved representation and / or improved encoding of discrete directional data (directional information) of directional sound sources. [Means for solving the problem]

[0007] One aspect of the present disclosure relates to a method for processing audio content including directional information for at least one sound source. The method may be performed in an encoder in case of encoding. Alternatively, the method may be performed in a decoder prior to rendering. The sound source may be, for example, a directional sound source and / or may relate to an audio object. The directional information may be discrete directional information. Furthermore, the directional information may be associated with an audio object. The directional information may be part of the metadata for the object. The directional information may include a first set of first directional unit vectors representing directional directions and associated first directional gains. The first directional unit vectors may be distributed non-uniformly on the surface of the 3D sphere. A unit vector means a vector of unit length. The method may include determining, as a count number, a number of unit vectors to place on the surface of the 3D sphere based on a desired representation accuracy. The determining step may also be said to relate to determining a number of unit vectors to be generated for placement on the surface of the 3D sphere based on the desired representation accuracy. The determined number of unit vectors may be defined as a cardinality of a set of unit vectors. The desired representation accuracy may be, for example, a desired angular accuracy or a desired directional accuracy. Furthermore, the desired representation accuracy may correspond to a desired angular resolution (e.g., in degrees). The method may further include generating a second set of second directional unit vectors by using a predefined arrangement algorithm to distribute the determined number of unit vectors on a surface of a 3D sphere. The predefined arrangement algorithm may be an algorithm for approximately uniformly spherically distributing the unit vectors on a surface of a 3D sphere. The predefined arrangement algorithm may be scalable according to the number of unit vectors to be arranged / generated (i.e., the number may be a control parameter of the predefined arrangement algorithm). The method may further include determining, for the second directional unit vector, an associated second directional gain based on a first directional gain of one or more first directional unit vectors of the group of first directional unit vectors that are closest to the respective second directional unit vector. The group of first directional unit vectors may be a suitable subgroup or a suitable subset of the first set of first directional unit vectors.

[0008] In such a configuration, the proposed method provides a representation of the discrete directional information (i.e. the determined number and second directional gain) that can be rendered at the decoder without the need for interpolation to provide a "uniform response" to object-to-listener orientation changes. Furthermore, the representation of the discrete directional information can be coded at a low bit rate, since the perceptually relevant directional unit vectors are not stored in the representation, but can be calculated at the decoder. Finally, the proposed method reduces the computational complexity at rendering.

[0009] In some embodiments, the number of unit vectors may be determined such that, when the unit vectors are distributed over the surface of a 3D sphere by a predetermined placement algorithm, they approximate, with up to a desired representation accuracy, the direction indicated by the first directional unit vector of the first set.

[0010] In some embodiments, the number of unit vectors may be determined such that, for each first directional unit vector in the first set, there is at least one unit vector whose directional difference with respect to the respective first directional unit vector is less than a desired representation accuracy when the unit vectors are distributed on the surface of the 3D sphere by a predetermined placement algorithm. The directional difference may be, for example, an angular distance. The directional difference may be defined with respect to a suitable directional difference norm.

[0011] In some embodiments, determining the number of unit vectors may include using a pre-established functional relationship between the representation accuracy and the number of corresponding unit vectors that are distributed on the surface of the 3D sphere by a pre-defined placement algorithm and that approximate at most the direction indicated by the first directional unit vector of the first set with the respective representation accuracy.

[0012] In some embodiments, determining an associated second directional gain for a given second directional unit vector may include setting the second directional gain to a first directional gain associated with a first directional unit vector that is closest (for purposes of this disclosure, closeness is defined by an appropriate distance criterion) to the given second directional unit vector. Alternatively, this determination may include, for example, stereo projection or triangulation.

[0013] In some embodiments, the predetermined placement algorithm may include superimposing a spiral path on a surface of the 3D sphere, the spiral path extending from a first point on the 3D sphere to a second point on the 3D sphere opposite the first point, and placing unit vectors successively along the spiral path, where based on the number of unit vectors, a spacing of the spiral path and / or an offset between every two adjacent unit vectors along the spiral path may be determined.

[0014] In some embodiments, determining the number of unit vectors may further include mapping (rounding) the number of unit vectors to one of a predefined number. The predefined number may be transmitted by a bitstream parameter. For example, the bitstream parameter may be a 2-bit parameter such as a directivity_precision parameter. In case of encoding, the method may include encoding the determined number into a value of the bitstream parameter.

[0015] In some embodiments, the desired rendering accuracy may be determined based on a model of the perceptual directional sensitivity thresholds of a human listener (eg, a human reference listener).

[0016] In some embodiments, the cardinality of the second directional unit vector of the second set may be smaller than the cardinality of the first directional unit vector of the first set, which may imply that the desired representational precision is smaller than the representational precision provided by the first directional unit vector of the first set.

[0017] In some embodiments, the first and second directional unit vectors may be expressed in spherical or Cartesian coordinate systems. For example, the first directional unit vector may be uniformly distributed in the azimuth-elevation plane, which implies a non-uniform (spherical) distribution on the surface of a 3D sphere. The second directional unit vector may be non-uniformly distributed in the azimuth-elevation plane in such a manner that it is (quasi-)uniformly distributed on the surface of a 3D sphere.

[0018] In some embodiments, the directional information represented by the first set of first directional unit vectors and associated first directional gains may be stored in a Spatial Oriented Format for Acoustics (SOFA) format. SOFA formats include formats standardized by the Audio Engineering Society (see, for example, AES69-2015). Additionally or alternatively, the directional information represented by the second set of first directional unit vectors and associated second directional gains may be stored in the SOFA format.

[0019] In some embodiments, the method may be a method for encoding audio content and may further comprise encoding the determined number of unit vectors together with the second directivity gain into a bitstream. The method may further comprise outputting the bitstream. This assumes that at least a part of the proposed method is performed on the encoder side.

[0020] Another aspect of the present disclosure is an audio control system including directional information for at least one sound source. The directional information may include a number (e.g., a count) indicating the number of unit vectors distributed approximately uniformly on the surface of a 3D sphere, and for each such unit vector, an associated directional gain. The unit vectors may be assumed to be distributed on the surface of the 3D sphere by a predefined constellation algorithm, where the predefined constellation algorithm may be an algorithm for spherically distributing the unit vectors approximately uniformly on the surface of the 3D sphere. The method may include receiving a bitstream including the audio content. The method may further include extracting the number and the directional gain from the bitstream. The method may further include determining (e.g., generating) a set of directional directional unit vectors by using the predefined constellation algorithm to distribute the number of unit vectors on the surface of the 3D sphere. In this sense, the number of unit vectors may serve as a control parameter of the predefined constellation algorithm. The method may further include associating each directional unit vector with its directional gain. This aspect assumes that the proposed method is distributed between the encoder and decoder sides.

[0021] In some embodiments, the method may further include, for a given target directional unit vector pointing in a direction from the sound source to the listener position, determining a target directional gain for the target directional unit vector based on associated directional gains of one or more directional unit vectors of a group of directional unit vectors that are closest to the target directional unit vector. The group of directional unit vectors may be a suitable subgroup or a suitable subset of the set of directional unit vectors.

[0022] In some embodiments, determining the target directional gain for the target directional unit vector may include setting the target directional gain to a directional gain associated with a directional unit vector that is closest to the target directional unit vector.

[0023] Another aspect of the present disclosure relates to a method for decoding audio content including directional information for at least one sound source. The directional information may include a first set of first directional unit vectors representing directional directions and associated first directional gains. The method may include receiving a bitstream including the audio content. The method may further include extracting the first set of directional unit vectors and associated first directional gains from the bitstream. The method may further include determining a number of unit vectors to place on a surface of a 3D sphere based on a desired representation accuracy as a count number. The method may further include generating a second set of second directional unit vectors by using a predetermined placement algorithm to distribute the determined number of unit vectors on the surface of the 3D sphere. Here, the predetermined placement algorithm may be an algorithm for approximately uniformly spherically distributing the unit vectors on the surface of the 3D sphere. The method may further comprise, for a second directional unit vector, determining an associated second directional gain based on a first directional gain of one or more first directional unit vectors of the group of first directional unit vectors that are closest to the respective second directional unit vector. The method may further comprise, for a given target directional unit vector pointing in a direction from the sound source to the listener position, determining a target directional gain for the target directional unit vector based on an associated second directional gain of one or more second directional unit vectors of the group of second directional unit vectors that are closest to the target directional unit vector. The group of second directional unit vectors may be a suitable subgroup or a suitable subset of the second set of second directional unit vectors. This aspect assumes that all of the proposed method is performed on the decoder side.

[0024] In some embodiments, the target pointing to the target directional unit vector Determining the directional gain may include setting the target directional gain to a second directional gain associated with a second directional unit vector that is closest to the target directional unit vector.

[0025] In some embodiments, the method may further include extracting from the bitstream an indication of whether a second set of directional unit vectors should be generated. The indication may be a one-bit flag, e.g., a directivity_type parameter. If the indication indicates that a second set of directional unit vectors should be generated, the method may further include determining the number of unit vectors and generating a second set of second directional unit vectors. Otherwise, the number of unit vectors and the (second) directional gain may be extracted from the bitstream.

[0026] Another aspect of the present disclosure relates to an apparatus for processing audio content including directional information for at least one sound source. The directional information may include a first set of first directional unit vectors representing directional directions and associated first directional gains. The apparatus may include a processor configured to perform the steps of the method of the first aspect and any of its embodiments.

[0027] Another aspect of the present disclosure is an apparatus for decoding audio content including directional information for at least one sound source. The directional information may include a count indicating the number (e.g., count number) of unit vectors approximately uniformly distributed on the surface of a 3D sphere, and for each such unit vector, an associated directional gain. The unit vectors may be assumed to be distributed on the surface of the 3D sphere by a predefined placement algorithm, where the predefined placement algorithm may be an algorithm for approximately uniformly spherically distributing the unit vectors on the surface of the 3D sphere. The apparatus may include a processor configured to perform the steps of the method of the second aspect and any of its embodiments.

[0028] Another aspect of the present disclosure relates to an apparatus for decoding audio content including directional information for at least one sound source. The directional information may include a first set of first directional unit vectors representing directional directions and associated first directional gains. The apparatus may include a processor configured to perform the steps of the method of the third aspect and any of its embodiments.

[0029] Another aspect of the present disclosure relates to a computer program comprising instructions which, when executed by a processor, cause the processor to perform the method of any one of the above first to third aspects and any of the embodiments thereof.

[0030] Another aspect of the present disclosure relates to a computer readable medium storing the computer program of the preceding aspect.

[0031] Another aspect of the present disclosure relates to an audio decoder including a processor connected to a memory storing instructions for the processor, the processor being configured to perform a method according to each one of the aspects or embodiments described above.

[0032] Another aspect of the present disclosure relates to an audio encoder including a processor connected to a memory storing instructions for the processor, the processor may be configured to perform a method according to each one of the aspects or embodiments described above.

[0033] Further aspects of the present disclosure relate to corresponding computer programs and computer readable storage media.

[0034] It will be understood that method steps and apparatus features are in various ways interchangeable. In particular, it will be understood by those skilled in the art that details of a disclosed method can be implemented as an apparatus configured to perform some or all of the method steps, and vice versa. In particular, it will be understood that each term referred to in the context of a method applies equally to the corresponding apparatus, and vice versa. [Brief description of the drawings]

[0035] Example embodiments of the present disclosure will now be described with reference to the accompanying drawings, in which like or similar elements are designated with like reference numerals, and in which:

[0036] [Figure 1A] FIG. 1A is a diagram that illustrates a schematic example of a representation of directional information including discrete directional unit vectors and associated directional gains. [Figure 1B] FIG. 1B is a diagram that illustrates a schematic example of a representation of directional information including discrete directional unit vectors and associated directional gains. [Figure 1C] FIG. 1C is a diagram that illustrates a schematic example of a representation of directional information including discrete directional unit vectors and associated directional gains. [Diagram 2] FIG. 2 is a diagram illustrating a schematic example of a directional unit vector and an associated directional gain. [Diagram 3] FIG. 3 is a diagram illustrating a schematic example of an arrangement of directional unit vectors on the surface of a 3D sphere according to a desired representation accuracy. [Figure 4] FIG. 4 is a diagram illustrating another example of the arrangement of directional unit vectors on the surface of a 3D sphere according to a desired representation accuracy. [Diagram 5] FIG. 5 is a graph that illustrates a schematic of the relationship between the number of unit vectors and the resulting representation accuracy, given a given placement algorithm for placing unit vectors on the surface of a 3D sphere. [Figure 6] FIG. 6 is a graph that illustrates a modeled relationship between the number of unit vectors and the resulting representation accuracy, given a given placement algorithm for placing unit vectors on the surface of a 3D sphere. [Figure 7A] FIG. 7A is a diagram that diagrammatically illustrates an example representation of directional information including discrete directional unit vectors and associated directional gains, according to an embodiment of the present disclosure. [Figure 7B]FIG. 7B is a diagram that diagrammatically illustrates an example representation of directional information including discrete directional unit vectors and associated directional gains, according to an embodiment of the present disclosure. [Figure 7C] FIG. 7C is a diagram that diagrammatically illustrates an example representation of directional information including discrete directional unit vectors and associated directional gains, according to an embodiment of the present disclosure. [Figure 8A] FIG. 8A is a diagram illustrating a schematic of a conventional representation of discrete directional information for different representation accuracy. [Figure 8B] FIG. 8B is a diagram illustrating a schematic representation of discrete directional information for different representation accuracy according to an embodiment of the present disclosure. [Figure 9] FIG. 9 illustrates, in flow chart form, a schematic diagram of a method for processing or encoding audio content including directional information for at least one sound source, according to an embodiment of the present disclosure. [Figure 10] FIG. 10 is a diagram illustrating, in flow chart form, a schematic example of a method for decoding audio content including directional information for at least one sound source, according to an embodiment of the present disclosure. [Figure 11] FIG. 11 is a diagram illustrating, in flow chart form, another example of a method for decoding audio content including directional information for at least one sound source, according to an embodiment of the present disclosure. [Figure 12] FIG. 12 is a diagram that diagrammatically illustrates an apparatus for processing or encoding audio content including directional information for at least one sound source, according to an embodiment of the present disclosure. [Figure 13] FIG. 13 is a diagram that diagrammatically illustrates an apparatus for decoding audio content that includes directional information for at least one sound source, according to an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0037] As mentioned above, in this disclosure, the same or similar elements are indicated by the same or similar reference numerals, and repeated description is omitted for the sake of brevity.

[0038] Audio formats that include directional data (directional information) about sound sources can be used for 6DoF rendering of audio content. In some of these audio formats, the directional data is discrete directional data stored (e.g., in SOFA format) as a set of discrete vectors consisting of direction (e.g., azimuth, elevation) and magnitude (e.g., gain). However, as mentioned above, it has been found that directly applying such conventional discrete directional representations for 6DoF rendering is less than optimal. In particular, for conventional discrete directional representations, the vector directions are typically significantly non-equidistantly spaced in 3D space, which requires interpolation between the vector directions during rendering (e.g., 6DoF rendering). Furthermore, the directional data includes redundancy and irrelevance, which increases the bitstream size for encoding the representation.

[0039] An example of a conventional representation of discrete directional information of a sound source is illustrated diagrammatically in Figures 1A, 1B, and 1C. The conventional representation includes a number of discrete directional unit vectors 10 and associated directional gains 15. Figure 1A illustrates a 3D view of the directional unit vectors 10 arranged on the surface of a 3D sphere. In this example, these directional unit vectors 10 are uniformly (i.e., equidistantly) arranged in the azimuth-elevation plane, resulting in a non-uniform spherical arrangement on the surface of the 3D sphere. This can be seen in Figure 1B, which illustrates a top view of the 3D sphere on which the directional unit vectors 10 are arranged. Finally, Figure 1C illustrates the directional gains 15 for the directional unit vectors 10, thereby illustrating the radiation pattern (or "directivity") of the sound source.

[0040] Although the representation of discrete directional information can be improved since the direction can be calculated at the decoder side (e.g., via a formula, table, or other pre-computed look-up information), such conventional representations may include directional sampling that is unnecessarily fine from a psychoacoustic point of view.

[0041] This disclosure provides a set of M discrete acoustic source directional gains. Assume an initial (e.g., conventional) representation of discrete directional information about a sound source (acoustic source) containing the data JPEG2025023937000002.jpg54. JPEG2025023937000003.jpg54 is a non-uniformly distributed directional unit vector It is defined on JPEG2025023937000004.jpg512. Here, each directional unit vector JPEG2025023937000005.jpg53 is the directional gain associated with itself. JPEG2025023937000006.jpg516. A directional unit vector is a directional vector of unit length. JPEG2025023937000007.jpg53, 210, and associated directional gain JPEG2025023937000008.jpg54 is illustrated in FIG. JPEG2025023937000009.jpg53 is placed on the surface 230 of a 3D sphere, which is a unit sphere. A set of directional unit vectors JPEG2025023937000010.jpg53 may be referred to for purposes of this disclosure as a first directional unit vector of the first set. JPEG2025023937000011.jpg54 may be referred to as a first directional gain associated with each of the first directional vectors.

[0042] As mentioned above, the directional unit vector The non-uniform distribution of JPEG2025023937000012.jpg53 requires the decoder to adjust the directional gain to achieve a uniform response to object-to-listener orientation changes. JPEG2025023937000013.jpg54 requires interpolation.

[0043] To address this issue, the present disclosure provides a method for reproducing the original data in a manner that produces equivalent (e.g., subjectively non-distinguishable) 6DoF audio rendering output. Optimized directional representation approximating JPEG2025023937000014.jpg53 The purpose of the present invention is to provide a directional unit vector JPEG2025023937000015.jpg53. JPEG2025023937000016.jpg53 and / or directional unit vector JPEG2025023937000017.jpg53 may be represented, for example, in a spherical coordinate system or a Cartesian coordinate system.

[0044] Optimized Representation JPEG2025023937000018.jpg53 is a directional vector It is defined on the quasi-uniform distribution of JPEG2025023937000019.jpg53. This results in a smaller bitstream size Bs. That is, JPEG2025023937000020.jpg523 and / or allows for a computationally efficient decoding process. For the purposes of this disclosure, quasi-uniform means uniform up to a given (e.g., desired) representational accuracy.

[0045] To do so, this disclosure assumes that the object-to-listener orientation is arbitrary with respect to uniform probability distribution and that the object-to-listener orientation representation accuracy (i.e., the desired representation accuracy) is known, e.g., defined based on the subjective directional sensitivity threshold of a human listener (e.g., a human reference listener).

[0046] The present disclosure provides at least the following technical advantages: The first technical advantage relates to the advantage of parameterizing the directional information to utilize a uniform directional representation in 3D space (not in the azimuth-elevation plane). The second ... This benefits from discarding the directional information contained in JPEG2025023937000021.jpg53.

[0047] A uniform representation of directionality is not easy because JPEG2025023937000022.jpg53-way uniform distribution problem (e.g., finding N points equidistantly spaced on the surface of a 3D unit sphere) is in general impossible to solve exactly for any number N>4, and numerical approximations for generating (quasi-)equidistantly distributed points on a 3D unit sphere are often very complex (e.g., iterative, stochastic, computationally intensive).

[0048] Original data Reducing irrelevance and redundancy in JPEG2025023937000023.jpg53 is also not easy, since it is highly related to the definition of orientation representation accuracy, which is based on psychoacoustic considerations.

[0049] Based on at least these technical advantages, the present disclosure proposes an efficient approximation method for uniform directional representation that avoids interpolation of directional gains at the decoder side and allows for significant bitrate reduction without degrading the psychoacoustic directional perception obtained from the 6DoF rendered output.

[0050] 9 illustrates in flow chart form an example of a method 900 for processing (or encoding) audio content including (discrete) directional information for at least one sound source (e.g., audio object) according to an embodiment of the present disclosure. The directional information is assumed to relate to directional information G defined above, i.e., to include a first set of first directional unit vectors representing directional directions and associated first directional gains. The directional information G may be included in the audio content as part of metadata for the sound source (e.g., audio object).

[0051] As an initial step (not shown in the flowchart), the method 900 may obtain audio content. Directivity information represented by a first set of first directional vectors and associated first directional gains may be stored in a SOFA format.

[0052] In step S910, the number N of unit vectors for placement on the surface of the 3D sphere is determined (e.g., calculated) as a count number based on a desired representation accuracy D. This may involve determining (e.g., based on calculation) the number N of (quasi-)equidistantly distributed direction or (directional) unit vectors (e.g., based on a given orientation representation accuracy D). Here, quasi-equidistantly distributed is understood to mean equidistantly distributed with a maximum representation accuracy D. The representation accuracy D may correspond, for example, to an angular accuracy or a directional accuracy. In this sense, the representation accuracy may correspond to an angular resolution. In some implementations, the desired representation accuracy may be determined based on a model of a perceptual directional threshold of a human listener (e.g., a human reference listener).

[0053] In particular, the output of this step is an integer, namely the number N of directional unit vectors. The actual generation of directional unit vectors is performed in step S920, described below. In other words, step S910 determines the cardinality of the set of directional unit vectors to be generated. The number N of unit vectors is determined by the following equation: JPEG2025023937000024.jpg53 unit vectors may be determined to approximate the direction indicated by the first directional vector of the first set with up to a desired representation accuracy D. Thus, for a given alignment, The algorithm may be an algorithm for approximately uniform spherical distribution of unit vectors (e.g., at most representation accuracy) on the surface of a 3D sphere. Examples of such placement algorithms are described below. In other words, the number N of unit vectors may be determined such that, when the unit vectors are distributed by the given placement algorithm on the surface of the 3D sphere, for each first directional unit vector in the first set, there exists at least one unit vector among the unit vectors whose directional difference with respect to the respective first directional unit vector is smaller than the desired representation accuracy D. The number N may function as a scalar (i.e., control parameter) for the given placement algorithm. That is, the given placement algorithm may be suitable for distributing any number of unit vectors on the surface of a 3D sphere.

[0054] In the above, the direction difference may be, for example, an angular distance (e.g., an angle). The direction difference may be defined with respect to a suitable direction difference norm (e.g., a direction difference norm depending on the scalar product of the directional unit vectors involved).

[0055] In step S920, a second set of second directional unit vectors is generated by using a predefined placement algorithm to distribute the determined number N of unit vectors on the surface of a 3D sphere. As described above, the predefined placement algorithm is an algorithm for approximately uniformly distributing the unit vectors on the surface of the 3D sphere. The second directional unit vectors are the directional unit vectors defined above. This step therefore uses a predefined placement algorithm controlled by the scaler N to find the directional vector JPEG2025023937000026.jpg511. Preferably, the cardinality of the second directional unit vector of the second set is smaller than the cardinality of the first directional unit vector of the first set. This assumes that the desired representation accuracy D is smaller than the representation accuracy provided by the first directional unit vector of the first set.

[0056] In step S930, for a second directional unit vector, an associated second directional gain is determined (e.g., calculated) based on the first directional gain. For example, this determination may be based on the first directional gain of one or more first directional unit vectors of a group of first directional unit vectors that are closest to the second directional unit vector. For example, this determination may include stereo projection or triangulation. In a particularly simple implementation, the second directional gain for a given second directional unit vector is set to the first directional gain associated with the first directional unit vector that is closest to the given second directional vector (i.e., has the shortest directional distance to the given second directional vector). In general, this step may be performed by: JPEG2025023937000027.jpg53 of the original data G defined above Directivity approximation defined on JPEG2025023937000028.jpg53 JPEG2025023937000029.jpg53. The directional information represented by the second set of second directional vectors and associated second directional gains may be present (e.g., stored) in a SOFA format.

[0057] If the method 900 is an encoding method, the method 900 further includes steps S940 and S950 described below, in which case the method 900 may be performed in an encoder.

[0058] In step S940, the determined number N of unit vectors is coded into the bitstream together with the second directivity gain. The second set of second directivity vectors and associated second directivity gains may be present (e.g., stored) in a SOFA format.

[0059] In step S950, the bitstream is output. For example, the bitstream may be output for transmission to a decoder or for storage in a suitable storage medium.

[0060] FIG. 10 illustrates in flow chart form an example of a method 1000 for decoding audio content including (discrete) directivity information for at least one sound source (e.g. audio object) according to an embodiment of the present disclosure. The method 1000 may be performed in a decoder. The audio content may be encoded in a bitstream, for example by steps S910-S950 of the method 900 described below. Thus, the directivity information may include a number N indicating the number of unit vectors approximately uniformly distributed on the surface of a 3D sphere, and (a representation of) an associated directivity gain for each such unit vector. The associated directivity gain may be the second directivity gain (data) defined above. The unit vectors may be determined by a given alignment algorithm (e.g., audio content alignment). The vectors may be assumed to be distributed on the surface of a 3D sphere by a predetermined constellation algorithm (the same as that used to process / encode the original content), where the predetermined constellation algorithm is an algorithm for approximately uniform spherical distribution of unit vectors on the surface of a 3D sphere.

[0061] In step S1010, a bitstream containing audio content is received.

[0062] In step S1020, the number N and the directional gain are extracted from the bit stream (e.g., by a demultiplexer). Decode the bitstream containing JPEG2025023937000032.jpg53 and the number N to obtain the data JPEG2025023937000033.jpg53 and a count N.

[0063] In step S1030, a set of directional unit vectors is determined (e.g., generated) by using a predefined arrangement algorithm to distribute the N unit vectors on the surface of a 3D sphere. This step may proceed in the same manner as step S920 above. Each directional unit vector determined in this step has an associated directional gain among the directional gains extracted from the bitstream in step S1020. Assuming that the same predefined arrangement algorithm is used in processing / encoding the audio content and decoding the audio content, the directional unit vectors generated in step S1030 are determined in the same order as the second directional unit vectors generated in step S920. Then, encoding the second directional gains as an ordered set in the bitstream in step S940 allows unambiguous assignment of directional gains to each of the generated directional unit vectors in step S1030.

[0064] In step S1040, for a given target directional unit vector pointing in a direction from the sound source to the listener's position, a target directional gain for the target directional unit vector is determined (e.g., calculated) based on the associated directional gain of the directional unit vector. For example, the target directional gain may be determined (e.g., calculated) based on the associated directional gain of one or more directional unit vectors in a group of directional unit vectors that are closest to the target directional unit vector.

[0065] For example, this determination may involve stereo projection or triangulation. In a particularly simple implementation, the target directional gain for a target directional unit vector is set to the directional gain associated with the directional unit vector closest to the target directional vector (i.e., the directional unit vector with the shortest directional distance to the target directional vector). In general, this process is performed using a directional gain that is based on the directional gain of the target directional unit vector. Defined above as JPEG2025023937000034.jpg53 It may involve using JPEG2025023937000035.jpg53.

[0066] Alternatively, the steps outlined above can be distributed differently between the encoder and the decoder. For example, in the case of a situation where the encoder cannot perform the operations of the method 900 listed above (e.g., the accuracy of the proposed approximation (representation accuracy) can be defined only on the decoder side), the necessary steps can be performed only on the decoder side. This does not result in a smaller bitstream size, but still has the advantage of saving computational complexity on the decoder side for rendering.

[0067] FIG. 11 illustrates in the form of a flow chart a corresponding example of a method 1100 for decoding audio content including (discrete) directional information for at least one sound source (e.g., audio object) according to an embodiment of the present disclosure. It is assumed that the directional information relates to directional information G defined above, i.e., includes a first set of first directional unit vectors representing directional directions and associated first directional gains. In this sense, contrary to the method 1000, the method 1100 receives as input audio content whose directional information has not yet been optimized by the method according to the present disclosure. The directional information G may be included in the audio content as part of metadata for the sound source (e.g., audio object).

[0068] In step S1110, a bitstream containing audio content is received, or the audio content may be obtained by any other possible means, depending on the application.

[0069] In step S1120, a first set of directional unit vectors and associated first directional gains are extracted from the bitstream (or obtained by any other possible means, depending on the application). In one example, the directional vectors and associated first directional gains can be de-multiplexed from the bitstream.

[0070] In step S1130, the number of vectors for placement on the surface of the 3D sphere is determined as a count based on the desired representation accuracy. This step may proceed in the same manner as step S910 above.

[0071] In step S1140, a second set of second oriented vectors is generated by using a predetermined placement algorithm to distribute the determined number of unit vectors on the surface of a 3D sphere. A characteristic unit vector is generated. The predetermined placement algorithm is an algorithm for approximately uniformly distributing the unit vectors on the surface of a 3D sphere. This step may proceed in the same manner as step S920 above.

[0072] In step S1150, for the second directional unit vector, an associated second directional gain is determined based on the first directional gain. For example, for the second directional unit vector, the associated second directional gain may be determined based on the first directional gain of one or more directional unit vectors of a group of first directional unit vectors that are closest to the respective second directional unit vector. Thus, this step may proceed in the same manner as step S930 above.

[0073] In step S1160, for a given target directional unit vector pointing in a direction from the sound source to the listener's position, a target directional gain for the target directional unit vector is determined based on the second directional gain. For example, the target directional gain may be determined for the target directional unit vector based on the associated second directional gain of one or more second directional unit vectors that are closest to the target directional unit vector among a group of second directional unit vectors. This step may proceed in the same manner as step S1040 above.

[0074] In a particularly simple implementation, the target directional gain for a target directional unit vector is set to the second directional gain associated with the second directional unit vector that is closest to the target directional vector (i.e., has the shortest directional distance to the target directional vector).

[0075] Since there may be flexibility that steps are performed at the encoder side and at the decoder side, it is further suggested to transmit to the decoder which steps it should perform (or, in other words, which format the directional data has). This can be easily done with one bit of information, for example, using the bitstream syntax for directional representation transmission shown in Table 1 below. Possible bitstream variable definitions for directional representation transmission are shown in Table 2 below.

[0076] [Table 1]

[0077] [Table 2]

[0078] In accordance with the above, a method for decoding audio content according to an embodiment of the present disclosure includes: determining from the bitstream whether a second set of directional unit vectors should be generated; Further, the method may include determining the number of unit vectors and generating a second set of second directional unit vectors if (and only if) the indication indicates that a second set of directional unit vectors should be generated. The indication may be a one-bit flag, e.g., the directivity_type parameter defined above.

[0079] Using the methods of the present disclosure, a representation of discrete directional data can be generated that does not require interpolation during 6DoF rendering to provide a "uniform response" to object-to-listener orientation changes. Furthermore, perceptually relevant directional unit vectors Because JPEG2025023937000038.jpg53 is computed rather than stored, a lower bit rate can be achieved in transmitting the representation.

[0080] An example of a representation of the discrete directional data of a sound source that can be achieved by the method according to the present disclosure is illustrated diagrammatically in Figures 7A, 7B and 7C. This representation should be compared with the representations illustrated diagrammatically in Figures 1A, 1B and 1C. Figure 7A shows a (second) directional unit vector placed on the surface of a 3D sphere. JPEG2025023937000039.jpg53, 20, 3D view. These directional unit vectors 20 are spatially uniformly distributed on the surface of a 3D sphere. This implies a non-uniform distribution in the azimuth-elevation plane. This can be seen in FIG. 7B, which is a top view of the 3D sphere on which the directional unit vectors 20 are located. Finally, FIG. 7C illustrates the (second) directional gain 25 for the (second) directional unit vector 20. This gives an indication of the radiation pattern (or "directivity") of the sound source. The envelope of this pattern is substantially identical to the envelope of the pattern illustrated in FIG. 1C, and contains the same amount of relevant psychoacoustic information.

[0081] FIG. 8A and FIG. 8B are different JPEG2025023937000040.jpg illustrates a further example comparing a conventional representation of discrete directional data of a sound source with a representation according to an embodiment of the present disclosure for 53 directional unit vectors (and corresponding orientation representation accuracy D). 8B (bottom) illustrates a representation according to an embodiment of the present disclosure. The leftmost panel is JPEG2025023937000042.jpg53. JPEG2025023937000043.jpg511 and This is relevant for the case JPEG2025023937000044.jpg511. The second panel from the left is JPEG2025023937000045.jpg511 and This is relevant for the case of JPEG2025023937000046.jpg511. The third panel from the left is JPEG2025023937000047.jpg512 and This concerns the case of JPEG2025023937000048.jpg511. The rightmost panel is JPEG2025023937000049.jpg512 and This is relevant for the case JPEG2025023937000050.jpg511.

[0082] A specific implementation example of the above method steps of the method according to the embodiment of the present disclosure will now be described.

[0083] For specific implementation examples of these, JPEG2025023937000051.jpg Assume that the original set of 53 discrete acoustic source directivity measurements (estimates) G is given by the following radiation pattern format:

number

[0084] Using the above assumptions, step S920 of method 900 (or step S1140 of method 1100) may proceed as follows.

[0085] N directional vectors that approximate a uniform directional distribution in 3D space (i.e., positions on a 3D unit sphere) Any suitable numerical approximation method (placement algorithm) may be used to calculate (i.e., generate) JPEG2025023937000058.jpg511 (see, for example, DPHardina, T. Michaelsab, EBSaff “A Comparison of Popular Point Configurations on S 2 ” (2016) Dolomites Research Notes on Approximation: Volume 9, Pages 16-49). However, this disclosure is not intended to be limited by, but may include, but is not limited to, Kogan, Jonathan “A New Computationally Efficient We propose to consider a specific approximation method (placement algorithm) based on “Method for Spacing n Points on a Sphere” (2017) Rose-Hulman Undergraduate Mathematics Journal: Volume 18, Issue 2, Article 5. The reason for this selection is that the method has low computational complexity and that it uses a single control parameter It depends on JPEG2025023937000059.jpg53, and there is no restriction on its control parameter N ( JPEG2025023937000060.jpg59).

[0086] The following equation (for example, solved in the encoder and decoder): Define JPEG2025023937000061.jpg53 and in the bitstream Avoid explicitly storing JPEG2025023937000062.jpg53.

number

number

number

[0087] More generally, the predetermined placement algorithm may include superimposing a spiraling path on the surface of a 3D sphere. The spiraling path extends from a first point on the sphere (e.g., one pole) to a second point on the sphere opposite the first point (e.g., the other pole). The predetermined placement algorithm may then sequentially place unit vectors along the spiraling path. The spacing of the spiraling path and the offset (e.g., step) between each two adjacent unit vectors along the spiraling path may be determined based on the number N of unit vectors.

[0088] Use the following example of a MatLab function to calculate a directional vector JPEG2025023937000068.jpg53 can be generated.

number

[0089] Using the following example MatLab script, we can calculate the vector It can represent JPEG2025023937000070.jpg53.

number

[0090] Using the above assumptions, step S910 of method 900 (or step S1130 of method 1100) may proceed as follows.

[0091] Directed Vector To calculate JPEG2025023937000072.jpg53, the control parameter It is necessary to specify JPEG2025023937000073.jpg53.

number

[0092] In simple terms, any (∀) direction For JPEG2025023937000075.jpg53, the corresponding direction JPEG2025023937000076.jpg54 (defined, for example, by the method of step S920) At least one (symbol: F) index that differs from JPEG2025023937000077.jpg53 by a value equal to or less than the orientation representation accuracy D JPEG2025023937000078.jpg52 exists.

[0093] This is illustrated diagrammatically in Figure 3. In Figure 3, the directional unit vector The maximum distance 310 from the nearest directional unit vector of JPEG2025023937000079.jpg53, 20 is less than the desired representation accuracy D. This is because the surface of the 3D sphere is The periphery of JPEG2025023937000080.jpg53 is subdivided into multiple cells, and each cell is determined by its directional unit vector JPEG2025023937000081.jpg53, any other directional unit vector If we assume that we include all directions closer than JPEG2025023937000082.jpg53, then the nearest directional unit vector This can be achieved by ensuring that the directional difference in any direction on the cell boundaries for JPEG2025023937000083.jpg53 is no greater than the desired representation accuracy D.

[0094] The representation accuracy (orientation representation accuracy) value D therefore represents the worst case, which is illustrated diagrammatically in FIG. JPEG2025023937000084.jpg54 has a non-zero value and zero for all other directions: JPEG2025023937000085.jpg518. In this case, a directional radiation pattern with orientation representation accuracy D (e.g., expressed in degrees) JPEG2025023937000086.jpg53 represents a cone 420 with radius D, 410.

[0095] In some implementations, determining the number N of unit vectors may include using a pre-established functional relationship between the representation accuracy D and the corresponding number N of unit vectors. The unit vectors are distributed on the surface of the 3D sphere by a pre-defined placement algorithm, and a first set of first directional unit vectors (e.g., The directions indicated by the JPEG2025023937000087.jpg53) are approximated with a maximum representation accuracy of D.

[0096] For example, such a functional relationship can be obtained by a brute force method, for example by repeatedly distributing different numbers N of directional unit vectors on the surface and determining the resulting representation accuracy, in the manner illustrated with reference to Figure 3. The placement algorithm described above with reference to Equations (2)-(4) can be used to determine the representation accuracy as illustrated in the graph of Figure 5 (circular marker 510). JPEG2025023937000088.jpg53 and JPEG2025023937000089.jpg53, which can be approximated using a linear function (continuous line 520 in FIG. 5).

number

[0097] Thus, in this example, the minimum number N of quasi-equidistantly distributed points N on a unit sphere required to achieve a desired directional representation accuracy D can be calculated by the following functional relationship N=N(D):

number

[0098] The method has an efficiency range for N < 2000, and the resulting orientation representation accuracy D is approximately equal to the subjective directional sensitivity threshold. JPEG2025023937000092.jpg56. Figure 6 illustrates this relationship 610 on a log-log scale. The dashed rectangle in this graph illustrates the efficiency range for N<~2000. The modeled relationship between the number of unit vectors N and representation accuracy D is also illustrated in Table 3 below for selected values.

[0099] [Table 3]

[0100] Step S930 of method 900 (or step S1150 of method 1100) may proceed as follows.

[0101] JPEG2025023937000094.jpg53 of the original data G (e.g., a first set of first directional unit vectors and associated first directional gains) defined above. Directional data approximation defined on JPEG2025023937000095.jpg53 Any approximation (e.g., stereo projection) method can be used to obtain JPEG2025023937000096.jpg53 (e.g., the associated second directivity gain). If this operation is performed on the encoder side (e.g., step S930 of method 900), it does not play a significant role in computational complexity.

[0102] On the other hand, directional data approximation A particularly simple procedure for determining the JPEG2025023937000097.jpg53 (e.g., the second directional gain) is For JPEG2025023937000098.jpg53 (e.g., the second directional unit vector), The directional unit vector with the smallest directional difference for JPEG2025023937000099.jpg53 Directivity gain of JPEG2025023937000100.jpg53 (e.g., the first directional unit vector) JPEG2025023937000101.jpg53( JPEG2025023937000102.jpg53) (for example, the first directivity gain). Selecting the "closest neighbor" of JPEG2025023937000103.jpg53 could proceed as follows:

number

[0103] Bitstream encoding (eg, at step S940 of method 900) and bitstream decoding (eg, at step S1020 of method 1000) may proceed according to the following considerations.

[0104] The generated bitstream is JPEG2025023937000105.jpg53 generation process (e.g., in step S1030 of method 1000) and the corresponding set of directional gains To control JPEG2025023937000106.jpg59, we need to include the encoding scalar value N.

[0105] Directional Data To transport JPEG2025023937000107.jpg53, there are two possible modes:

[0106] One possible mode (the first mode) is the directional gain The goal of the present invention is to encode the complete set of JPEG2025023937000108.jpg527, where the bitstream is encoded in the corresponding direction, for example according to the order in the bitstream. N gain values ​​assigned to JPEG2025023937000109.jpg53 would contain the complete sequence JPEG2025023937000110.jpg59.

[0107] Another possible mode (the second mode) is to send a partial subset to the bitstream, JPEG2025023937000111.jpg58, JPEG2025023937000112.jpg529, In this case, the bitstream is encoded as JPEG2025023937000113.jpg518, for example, by an explicit index in the bitstream. JPEG2025023937000114.jpg52 sent (i.e. index in subset The corresponding direction indicated by the transmission of JPEG2025023937000115.jpg52 1 array N assigned to JPEG2025023937000116.jpg53 subset Gain values It will only contain JPEG2025023937000117.jpg58.

[0108] The bitstream size Bs for both possible modes can be estimated as follows: For the first mode, the bitstream size Bs can be estimated as follows:

number

[0109] For the second mode, the bitstream size Bs may be estimated as follows:

number

[0110] To achieve better bitstream coding efficiency for JPEG2025023937000120.jpg511, in some implementations, numerical approximation methods (e.g., curve fitting) can be used. One particular advantage of the present disclosure is that it is possible to apply 1D approximation methods (assuming that the data G is fitted to a 1D spiral path s i (Because the azimuth-elevation plane is defined above and uniformly distributed.) A conventional representation of discrete directional information using uniformly distributed directional unit vectors within JPEG2025023937000121.jpg511 would require applying 2D approximation methods and taking into account boundary conditions.

[0111] In order to achieve better bitstream encoding efficiency for JPEG2025023937000122.jpg55, in some implementations, determining the number N of unit vectors may include mapping the number N of unit vectors to one of a set of predetermined numbers, for example, by rounding to the nearest number of the set of predetermined numbers. The predetermined number can then be transmitted to the decoder by a bitstream parameter (e.g., bitstream parameter directivity_precision). In this case, there may be an agreement between the encoder side and the decoder side on the relationship between the value of the bitstream parameter and the corresponding number of the predetermined number. This agreement may be established, for example, by storing the same lookup table at the encoder side and the decoder side.

[0112] In other words, to achieve better bitstream coding efficiency, For JPEG2025023937000123.jpg53, we want to find the optimal binary representation (e.g., It may be recommended to use preselected settings that result in a resolution of 100% (JPEG2025023937000124.jpg55=2 bits) and accuracy D.

[0113] [Table 4]

[0114] An example of the bitstream syntax for directivity size transmission is shown in Table 5 below.

[0115] [Table 5]

[0116] An example of a possible bitstream variable definition for directivity size transmission is shown in Table 6 below.

[0117] [Table 6]

[0118] The audio directivity modeling of the method in 6DoF rendering (eg, in step S1040 of method 1000 or step S1160 of method 1100) may proceed as follows.

[0119] For each given object-to-listener relative direction P (target directivity vector), the closest directional vector The index corresponding to JPEG2025023937000128.jpg54 JPEG2025023937000129.jpg52 is determined as follows:

number

[0120] A corresponding directional gain is then applied to render the sound source at the listener's position. JPEG2025023937000131.jpg59 is applied to this object signal.

[0121] For convenience of description and explanation, the radiation pattern of the sound source is assumed to be broadband, constant, and S 2 We have assumed that all of space is covered, but the present disclosure is equally applicable to spectral frequency dependent radiation patterns (e.g., by performing the proposed method band by band). Furthermore, the present disclosure is equally applicable to time dependent radiation patterns and to radiation patterns that include any subset of directions.

[0122] Furthermore, the concepts and techniques described in this disclosure may be specified in a frequency and time varying manner, may be applied directly in the spatial or time domain, may be defined in a global or object dependent manner, may be hard coded into the audio renderer, or may be specified via a corresponding input interface.

[0123] The methods and systems described herein may be implemented as software, firmware and / or hardware. Certain components may be implemented as software running on a digital signal processor or microprocessor. The components of may be implemented as hardware and / or as application specific integrated circuits. The signals appearing in the above described methods and systems may be stored in a medium such as a random access memory or an optical storage medium. They may be transferred over a network such as a radio, satellite, wireless or wired network, e.g., the Internet. Typical devices utilizing the methods and systems described herein are portable electronic devices or other consumer devices used to store and / or render audio signals.

[0124] FIG. 12 illustrates a schematic example of an apparatus 1200 (e.g., an encoder) for encoding audio content according to an embodiment of the present disclosure. The apparatus 1200 may include an interface system 1210 and a control system 1220. The interface system 1210 may include one or more network interfaces, one or more interfaces between the control system and a memory system, one or more interfaces between the control system and another device, and / or one or more external device interfaces. The control system 1220 may include at least one of a general-purpose single or multi-chip processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, or discrete hardware components. Thus, in some implementations, the control system 1220 may include one or more processors and one or more non-transitory storage media operably connected to the one or more processors.

[0125] According to some such examples, the control system 1220 may be configured to receive, via the interface system 120, audio content to be processed / encoded. The control system 1220 may be further configured to determine a number of unit vectors to place on the surface of the 3D sphere as a count number based on a desired representation accuracy (e.g., as in step S910 above); generate a second set of second directional unit vectors by using a predefined placement algorithm to distribute the determined number of unit vectors on the surface of the 3D sphere (wherein the predefined placement algorithm is an algorithm for approximately uniformly spherically distributing the unit vectors on the surface of the 3D sphere) (e.g., as in step S920 above); for the second directional unit vectors, determine an associated second directional gain based on a first directional gain of one or more first directional unit vectors of the group of first directional unit vectors that are closest to the respective second directional unit vector (e.g., as in step S930 above); and encode the determined number together with the second directional gain into the bitstream (e.g., as in step S940 above). The control system 1220 may be further configured to output the bitstream (eg, as in step S950 above) via the interface system.

[0126] FIG. 13 illustrates a schematic example of an apparatus 1300 (e.g., a decoder) for decoding audio content according to an embodiment of the present disclosure. The apparatus 1300 may include an interface system 1310 and a control system 1320. The interface system 1310 may include one or more network interfaces, one or more interfaces between the control system and a memory system, one or more interfaces between the control system and another device, and / or one or more external device interfaces. The control system 1320 may include at least one of a general-purpose single or multi-chip processor, a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, or discrete hardware components. Thus, in some implementations, the control system 1320 may include one or more The system may include a processor and one or more non-transitory storage media operably connected to the one or more processors.

[0127] According to some such examples, the control system 1320 may be configured to receive a bitstream including audio content via the interface system 1310. The control system 1320 may be further configured to extract the number and the directional gain from the bitstream (e.g., as in step S1010 above), generate a set of directional unit vectors by using a predefined placement algorithm to distribute the number of unit vectors on a surface of a 3D sphere (e.g., as in step S1020 above), and, for a given target directional unit vector pointing in a direction from a sound source to a listener position, determine a target directional gain for the target directional unit vector based on an associated directional gain of one or more directional unit vectors of the group of directional unit vectors that are closest to the target directional unit vector (e.g., as in step S1030 above).

[0128] Also, according to some such examples, the control system 1320 may be configured to receive a bitstream including audio content via the interface system 1310 (e.g., as in step S111 above). The control system 1320 may include steps of: extracting a first set of directional vectors and associated first directional gains from the bitstream (e.g., as in step S1120 above); determining a number of unit vectors to place on a surface of a 3D sphere as a count number based on a desired representation accuracy (e.g., as in step S1130 above); generating a second set of second directional unit vectors by using a predefined placement algorithm to distribute the determined number of unit vectors on the surface of the 3D sphere (wherein the predefined placement algorithm is an algorithm for approximately uniformly spherically distributing the unit vectors on the surface of the 3D sphere) (e.g., as in step S1140 above); The method may be further configured to, for a directional unit vector, determine an associated second directional gain based on a first directional gain of one or more first directional unit vectors of the group of first directional unit vectors that are closest to the respective second directional unit vector (e.g., as in step S1150 above), and to, for a given target directional unit vector pointing in a direction from the sound source to the listener position, determine a target directional gain for the target directional unit vector based on an associated second directional gain of a second directional unit vector of the group of second directional unit vectors that is closest to the target directional unit vector (e.g., as in step S1160 above).

[0129] In some examples, either or each of the above apparatuses 1200 and 1300 may be implemented in a single device. However, in some implementations, an apparatus may be implemented in more than one device. In some such implementations, the functionality of the control system may be included in more than one device. In some examples, an apparatus may be a component of another device.

[0130] Unless otherwise indicated, and as will be apparent from the description that follows, throughout this disclosure, descriptions using terms such as "processing," "operation," "calculation," "determination," "analyze," and the like will be understood to refer to the operations and / or processing of a computer or computing system or similar electronic computing device that manipulates and / or converts data represented as physical quantities, such as quantities of electrons, into other data also represented in physical quantities.

[0131] Similarly, the term "processor" may refer to any device or part of a device that processes electronic data, for example from a register and / or memory, and transforms the electronic data into other electronic data (which may, for example, be stored in a register and / or memory). A "computer" or "computing machine" or "computing platform" may include one or more processors.

[0132] The methodology described herein is executable by one or more processors that accept computer-readable (machine-readable) code, in one example embodiment, including a set of instructions that, when executed by the one or more processors, executes at least one of the methods described herein. Any processor capable of executing a set of instructions (sequential or otherwise) that specify operations to be performed is included. Thus, one example is a typical processing system including one or more processors. Each processor may include one or more of a CPU, a graphics processing unit, and a programmable DSP unit. The processing system may further include a memory subsystem including a main RAM and / or a static RAM and / or a ROM. A bus subsystem may be included for communication between components. The processing system may further include a distributed processing system having processors connected by a network. If the processing system requires a display, such a display may be, for example, a liquid crystal display (LCD) or a cathode ray tube display (CRT), etc. If manual data entry is required, the processing system also includes an input device, such as one or more of an alphanumeric input unit such as a keyboard, a pointing control device such as a mouse, etc. The processing system may also include a storage system, such as a disk drive unit. In some configurations, the processing system may include a sound output device and a network interface device. The memory subsystem thus includes a computer-readable carrier medium that holds computer-readable code (e.g., software) that includes a set of instructions that, when executed by one or more processors, causes the execution of one or more of the methods described herein. It should be noted that, when the method includes several elements, e.g., several steps, no ordering of such elements is implied unless specifically stated. The software may reside in a hard disk, or may reside, completely or at least partially, in a RAM and / or in a processor during execution by the computer system.Thus, the memory and the processor also constitute a computer-readable carrier medium carrying computer-readable code, which may further form or be included in a computer program product.

[0133] In alternative exemplary embodiments, the one or more processors may operate as standalone devices or may be connected (e.g., connected via a network) to other processors in a networked deployment, the one or more processors may operate in the capacity of a server or user machine in a server-user network environment, or as a peer machine in a peer-to-peer or distributed network environment. The one or more processors may form a personal computer (PC), tablet PC, personal digital assistant (PDA), mobile phone, web appliance, network router, switch or bridge, or any machine capable of executing a set of instructions (sequential or otherwise) that specify operations to be performed by the machine.

[0134] Also, it should be noted that the term "machine" is intended to include any collection of machines that individually or collectively execute a set of instructions (or multiple sets) for performing any one or more of the methodologies described herein.

[0135] Thus, one exemplary embodiment of each of the methods described herein may include a computer program that holds a set of instructions, e.g., a computer program, for execution on one or more processors, e.g., one or more processors that are part of a web server configuration. The present disclosure may be implemented as a method, an apparatus such as a dedicated device, an apparatus such as a data processing system, or a computer-readable carrier medium, e.g., a computer program product, as will be appreciated by those skilled in the art. The computer-readable carrier medium carries computer-readable code that includes a set of instructions that, when executed on one or more processors, cause the processor to implement the method. Thus, aspects of the present disclosure may take the form of a method, an entirely hardware exemplary embodiment, an entirely software exemplary embodiment, or an exemplary embodiment combining software and hardware aspects. Furthermore, the present disclosure may take the form of a carrier medium (e.g., a computer program product on a computer-readable storage medium) carrying computer-readable program code embodied in the medium.

[0136] The software may further be transmitted and received over a network via a network interface device. Although the carrier medium is a single medium in the illustrated embodiment, the term "carrier medium" should be interpreted to include a single medium or multiple media (e.g., a centralized or distributed database and / or associated caches and servers) that store one or more sets of instructions. The term "carrier medium" should also be interpreted to include any medium that can store, encode, or hold a set of instructions to be executed by one or more processors, causing the one or more processors to perform any one or more of the methodologies of the present disclosure. Carrier media may take many forms, including, but not limited to, non-volatile media, volatile media, and transmission media. Non-volatile media include, for example, optical disks, magnetic disks, and magneto-optical disks. Volatile media include dynamic memory, such as main memory. Transmission media include coaxial cables, copper wire, and fiber optics, including the wires that comprise a bus subsystem. Transmission media may also take the form of acoustic or light waves, such as those generated during radio wave and infrared data communications. Thus, for example, the term "carrier medium" should be interpreted to include, but is not limited to, computer products embodied in solid-state memories, optical and magnetic media, media carrying propagated signals detectable by at least one processor or more processors and representing a set of instructions that when executed implement a method, and transmission media in a network carrying propagated signals detectable by at least one of one or more processors and representing a set of instructions.

[0137] It will be understood that the steps of the described method are performed, in one example embodiment, by a suitable processor (or processors) of a processing (e.g., computer) system executing instructions (e.g., computer-readable code) stored in storage. It will also be understood that the present disclosure is not limited to any particular implementation or programming technique, and that the present disclosure may be implemented using any suitable technique for implementing the functions described herein. The present disclosure is not limited to any particular programming language or operating system.

[0138] References throughout this disclosure to "one exemplary embodiment," "some exemplary embodiments," or "exemplary embodiments" mean that a particular feature, structure, or property described in connection with an exemplary embodiment is included in at least one exemplary embodiment of the disclosure. Thus, the appearances of the phrases "in one exemplary embodiment," "in some exemplary embodiments," or "in exemplary embodiments" in various places throughout this disclosure do not necessarily all refer to the same exemplary embodiment. Furthermore, particular features, structures, or properties may be combined in any suitable manner in one or more exemplary embodiments, as would be apparent to one of ordinary skill in the art from this disclosure.

[0139] As used herein, unless otherwise specified, the use of the ordinal adjectives "first," "second," "third," etc. to describe a common object is intended merely to indicate that different instances of a similar object are being referred to, and is not intended to imply that the objects so described must be arranged in a given order, in time, space, precedence, or in any other manner.

[0140] In the following claims and in this specification, the terms "comprise" or "include" are both open terms meaning that the terms include at least the elements / features in question, but do not exclude others. Thus, the terms "comprise" or "include", when used in the claims, should not be interpreted as limiting the means or elements or steps to which they are recited. For example, the scope of an expression "a device comprising A and B" should not be limited to a device consisting of elements A and B only. As used in this specification, the terms "comprise" or "include" are also both open terms meaning that the terms include at least the elements / features in question, but do not exclude others. Thus, "comprise" is synonymous with and means "comprise".

[0141] In the above description of the exemplary embodiments of the present disclosure, it should be understood that various features of the present disclosure may be grouped together in a single exemplary embodiment, figure, or description thereof in order to simplify the disclosure and aid in understanding one or more of the various inventive aspects. However, this method of disclosure should not be interpreted as reflecting an intention that the claims require more features than are expressly recited in each claim. Rather, as the following claims reflect, aspects of the present invention exist in less than all features of a single disclosed exemplary embodiment described above. Thus, the claims that follow this specification are expressly incorporated herein, with each claim standing on its own as a separate exemplary embodiment of the present disclosure.

[0142] Moreover, it will be understood by those skilled in the art that some exemplary embodiments described herein include some of the features included in other exemplary embodiments and not others, meaning that combinations of features of different exemplary embodiments are within the scope of the present disclosure and form different exemplary embodiments. For example, in the following claims, any of the claimed embodiments can be used in any combination.

[0143] In the description provided herein, many specific details are set forth. However, it is understood that example embodiments of the present disclosure may be practiced without these specific details. In other instances, details of well-known methods, structures and techniques have been omitted so as not to obscure an understanding of this description.

[0144] Thus, while what is believed to be the best mode of the disclosure has been described, those skilled in the art will recognize that other and further modifications may be made thereto without departing from the spirit of the disclosure, and that all such variations and modifications are intended to be claimed within the scope of the disclosure. For example, any formulas given above are merely representative of procedures that may be used. Functions may be added to or deleted from the block diagrams, and operations may be interchanged between functional blocks. Steps may be added or deleted to methods described within the scope of the disclosure.

[0145] Various aspects of the present invention can be understood from the enumerated example embodiments (EEE) set forth below. 1. A method for processing audio content including directional information for at least one sound source, the directional information including a first set of first directional unit vectors representing directional directions and associated first directional gains, the method comprising: determining a number of unit vectors to place on a surface of a 3D sphere, as a count number, said number of unit vectors being related to a desired representation accuracy; generating a second set of second directional unit vectors by using a predefined placement algorithm to distribute the determined number of unit vectors over the surface of the 3D sphere, the predefined placement algorithm being an algorithm for approximately uniformly distributing the unit vectors spherically over the surface of the 3D sphere; determining, for each of the second directional unit vectors, an associated second directional gain based on a first directional gain of one or more first directional unit vectors of a group of first directional unit vectors that are closest to the respective second directional unit vector; The method includes: 2.A method as described in EEE1, wherein the number of unit vectors is determined such that, when the unit vectors are distributed over the surface of the 3D sphere by the predetermined placement algorithm, they approximate the direction indicated by a first directional unit vector of the first set with at most the desired representation accuracy. 3. A method as described in EEE1 or 2, wherein the number of unit vectors is determined such that, for each of the first directional unit vectors in the first set, when the unit vectors are distributed on the surface of the 3D sphere by the predetermined placement algorithm, there is at least one unit vector among the unit vectors whose directional difference with respect to the respective first directional unit vector is less than the desired representation accuracy. 4. A method according to any one of the preceding EEE, wherein determining the number of unit vectors comprises using a pre-established functional relationship between a representation accuracy and a number of corresponding unit vectors that are distributed on the surface of the 3D sphere by the predetermined placement algorithm and that approximate the direction indicated by a first directional unit vector of the first set at most with the respective representation accuracy. 5. A method according to any one of the preceding claims, wherein the step of determining an associated second directional gain for a given second directional unit vector comprises: setting the second directional gain to the first directional gain associated with the first directional unit vector that is closest to the given second directional unit vector. A method comprising: 6. A method according to any one of the preceding EEE, wherein the predetermined placement algorithm comprises superimposing on the surface of the 3D sphere a helical path extending from a first point on the 3D sphere to a second point on the 3D sphere opposite the first point, and placing the unit vectors successively along the helical path; determining a spacing of the helical path and an offset between every two adjacent unit vectors along the helical path based on the number of unit vectors; method. 7. A method according to any one of the preceding EEE, wherein determining the number of unit vectors further comprises mapping the number of unit vectors to one of a predetermined number, the predetermined number being signalable by a bitstream parameter. 8. A method according to any one of the preceding EEE, wherein the desired representation accuracy is determined based on a model of a human listener's perceptual directional sensitivity threshold. 9. A method according to any one of the preceding EEE, wherein a cardinality of the second directional unit vector of the second set is less than a cardinality of the first directional unit vector of the first set. 10. A method according to any one of the preceding EEE, wherein the first and second directional unit vectors are expressed in a spherical coordinate system or a Cartesian coordinate system. 11. The method of any one of the preceding EEE, comprising: and the directional information represented by the directional unit vector of the first directional gain is stored in a SOFA format; and / or the directional information represented by the second set of first directional unit vectors and associated second directional gains is stored in a SOFA format. method. 12. A method according to any one of the preceding claims, comprising: encoding the determined number of unit vectors together with the second directivity gain into a bitstream; outputting the bitstream; The method further comprises: 13. A method of decoding audio content including directional information for at least one sound source, the directional information including a count indicating a number of unit vectors approximately uniformly distributed on a surface of a 3D sphere and, for each such unit vector, an associated directional gain, the unit vectors being assumed to be distributed on the surface of the 3D sphere by a predefined constellation algorithm, the predefined constellation algorithm being an algorithm for approximately uniformly spherically distributing the unit vectors on the surface of the 3D sphere, the method comprising: receiving a bitstream containing the audio content; extracting said number and said directivity gain from said bitstream; generating a set of directional unit vectors by using the predefined placement algorithm to distribute the number of unit vectors onto the surface of the 3D sphere; The method includes: 14. A method according to any preceding EEE, comprising: determining, for a given target directional unit vector pointing in a direction from the sound source to a listener position, a target directional gain for the target directional unit vector based on associated directional gains of one or more directional unit vectors of a group of directional unit vectors that are closest to the target directional unit vector. The method further includes: 15. A method according to any preceding claim, wherein the step of determining the target directivity gain for the target directivity unit vector comprises: setting the target directional gain to the directional gain associated with the directional unit vector that is closest to the target directional unit vector. The method includes: 16. A method of decoding audio content including directional information for at least one sound source, the directional information including a first set of first directional unit vectors representing directional directions and associated first directional gains, the method comprising: receiving a bitstream containing the audio content; extracting the first set of directional unit vectors and the associated first directional gains from the bitstream; determining a number of unit vectors to place on a surface of a 3D sphere, as a count number, said number of unit vectors being related to a desired representation accuracy; generating a second set of second directional unit vectors by using a predefined placement algorithm to distribute the determined number of unit vectors over the surface of the 3D sphere, the predefined placement algorithm being an algorithm for approximately uniformly distributing the unit vectors spherically over the surface of the 3D sphere; determining, for each of the second directional unit vectors, an associated second directional gain based on a first directional gain of one or more first directional unit vectors of a group of first directional unit vectors that are closest to the respective second directional unit vector; and, for a given target directional unit vector pointing in a direction from the sound source to a listener position, determining a target directional gain for the target directional unit vector based on associated second directional gains of one or more second directional unit vectors of a group of second directional unit vectors that are closest to the target directional unit vector; The method includes: 17. The method according to claim 16, wherein determining the target directivity gain for the target directivity unit vector comprises: setting the target directional gain to the second directional gain associated with the second directional unit vector that is closest to the target directional unit vector. The method includes: The method according to claim 18.EEE16 may extracting from the bitstream an indication of whether the second set of directional unit vectors should be generated; if the indication indicates that the second set of directional unit vectors should be generated, determining the number of unit vectors and generating a second set of directional unit vectors; The method further comprises: 19. An apparatus for processing audio content including directional information for at least one sound source, the directional information including a first set of first directional unit vectors representing directional directions and associated first directional gains, the apparatus comprising a processor configured to perform steps of the method according to any one of claims 1 to 12. Device. 20. An apparatus for decoding audio content comprising directivity information for at least one sound source, the directivity information comprising a count indicating a number of unit vectors approximately uniformly distributed on a surface of a 3D sphere and, for each such unit vector, an associated directivity gain, the unit vectors being assumed to be distributed on the surface of the 3D sphere by a predefined constellation algorithm, the predefined constellation algorithm being an algorithm for approximately uniformly spherically distributing the unit vectors on the surface of the 3D sphere, the apparatus comprising a processor configured to perform the steps of the method according to any one of EEE13 to EEE15. Device. 21. An apparatus for decoding audio content comprising directional information for at least one sound source, the directional information comprising a first set of first directional unit vectors representing directional directions and associated first directional gains, the apparatus comprising a processor configured to perform steps of the methods described in any one of EEE16 to EEE18. 22. A computer program comprising instructions which, when executed by a processor, cause the processor to perform a method according to any one of EEE1 to EEE18. 23. A computer readable medium storing a computer program according to EEE22.

Claims

1. 1. A method for decoding audio content comprising directional information for at least one sound source of the audio content, comprising: receiving a bitstream including the audio content; extracting a first parameter indicative of the number of unit vectors approximately uniformly distributed on the surface of a 3D sphere and, for each unit vector, a second parameter indicative of an associated directivity gain; generating a set of directional unit vectors based on the first parameters, the second parameters, and an algorithm for approximately uniformly distributing the unit vectors on a surface of the 3D sphere; The method includes:

2. The method of claim 1 , further comprising rendering the at least one sound source based on the set of directional unit vectors.

3. A non-transitory computer program comprising instructions that, when executed by a processor, cause the processor to perform the method of claim 1.

4. 1. An apparatus for decoding an audio content comprising directional information for at least one sound source of the audio content, the apparatus comprising: a receiver for receiving a bitstream containing said audio content; a first processor for extracting a first parameter indicative of a number of unit vectors approximately uniformly distributed on a surface of a 3D sphere, and for each unit vector a second parameter indicative of an associated directivity gain; a second processor for generating a set of directional unit vectors based on the first parameters, the second parameters, and an algorithm for approximately uniformly spherically distributing the unit vectors on a surface of the 3D sphere; An apparatus comprising:

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