A method and apparatus for control in 6DoF rendering

Abstract

A method and apparatus for assisting six degrees-of-freedom rendering of an audio scene when a listener position is external to a capture area. The method and apparatus comprise: obtaining information

Description

Field The present application relates to apparatus and methods for exterior rendering control in 6 degrees-of-freedom rendering and not specifically with 6 degrees-of-freedom systems of microphone-array captured audio. Background Spatial audio capture approaches attempt to capture an audio environment or audio scene such that the audio environment or audio scene can be perceptually recreated to a listener in an effective manner and furthermore may permit a listener to move and / or rotate within the recreated audio environment. For spatial audio capture and recording spatial sound linearly at one position at the recording space, a high-end microphone array is needed. One such microphone is the spherical 32-microphone Eigenmike. From the high-end microphone array higher-order Ambisonics (HOA) signals can be obtained and used for rendering. With the HOA audio signals, the spatial audio can be rendered so that sounds arriving from different directions are satisfactorily separated in a reasonable auditory bandwidth. In some systems multiple microphone locations enable a multi-point HOA (MPHOA) capture system where there are multiple HOA audio signals at locations within an audio scene. In some embodiments even basic microphone array for up to first order ambisonics may also be used for recording the the audio scene. In some other embodiments, the audio scene may comprise two or more synthetic FOA or HOA sources. Audio rendering, where the captured audio signals are presented to a listener can be part of a virtual reality (VR) or augmented reality (AR) system. The audio rendering furthermore can be performed as part of a VR or AR where the listener can freely move within the environment or audio scene and rotate their head, which is known as a 6 degrees of freedom (6DoF) configuration. Furthmore the audio rendering can be Multi-Point HOA (MPHOA) audio rendering where the audio scene comprises multiple HOA audio signals recordings which are rendered to a user in a 6DoF manner. That is, the user is able to listen to the recorded scene from positions that may be other than the positions of the recorded HOA sources. Summary There is provided according to a first aspect a method for assisting six degrees-of-freedom rendering of an audio scene when a listener position is external to a capture area, the method comprising: obtaining information associated with an audio source; determining a position of the audio source relative to the capture area; when the position of the audio source is external to the capture area, obtaining a parameter; defining a rendering parameter for assisting the rendering of an audio signal when the listener position is external to the capture area; and encoding at least the rendering parameter based on the provided parameter. The capture area may be defined relative to: at least one microphone position or at least one higher order ambisonics position; and a perimeter defined by at least two microphones positions or at least two higher order Ambisonics positions. The rendering parameter for assisting the rendering of an audio signal may comprise an exterior rendering projection radius value, for mapping the audio source as a target audio source when the listener position is external to the capture area. The rendering parameter for assisting the rendering of an audio signal may further comprise an indicator that the exterior rendering projection radius value is an adaptive value. The exterior rendering projection radius value may define a distance for assisting a mapping of the audio source position to a distance perpendicular from either the at least one microphone position or at least one higher order ambisonics position or the perimeter. Defining a rendering parameter for assisting the rendering of an audio signal when the listener position is external to the capture area when the rendering parameter is the exterior rendering projection radius value may comprise: determining the exterior renering projection radius value based on an input; determining a quality check on the determined exterior rendering projection radius value; and providing the exterior renering projection radius value based on an input as the exterior rendering projection value when the quality check is passed or modifying the exterior renering projection radius value otherwise. The method may further comprise: obtaining audio data associated with the at least one audio source; and encoding the audio data to generate an audio data bitstream. Obtaining audio data associated with the at least one audio source may comprise obtaining at least three audio signals from: at least three microphones; or at least three higher order Ambisonics, wherein the at least three microphones or at least three higher order ambisonics audio signals are associated with positions within the audio scene. Determining the position of the audio source relative to the capture area may comprise a determining the position of the audio source based on the at least three audio signals and positions associated with the at least three microphones or the at least three higher order Ambisonics. The method may further comprise determining the position of the audio source is external by: triangulating positions within the audio scene of the at least three microphones or the at least three higher order ambisonics; identifying the position of the audio source within the audio scene is exterior to the triangulation of the positions within the audio scene of the at least three microphones or the at least three higher order ambisonics. The method may further comprise determining the exterior rendering projection radius value from a distance between the position of the audio source within the audio scene and a line between two closest positions of the at least three microphones or the at least three higher order ambisonics. The information associated with the audio source may further comprise a position of the audio source within the audio scene. The method may further comprise receiving a listener position, wherein the information indicating the audio source is a target audio source within the audio scene may be based on the distance between an audio source position and the listener position. According to a second aspect there is provided a method for six degrees-of-freedom rendering of an audio scene when a listener position is external to a capture area, the method comprising: obtaining information associated with an audio souce; obtaining a rendering parameter for assisting the rendering of an audio signal when the listener position is external to the capture area; obtaining the listener position, the listener position being external to the capture area and within the audio scene; mapping a position of the audio source to a mapped position around the listener position based on the rendering parameter; generating at least one audio output based on the mapped position within the audio scene to achieve a localized rendering with respect ot the listener position. The method may further comprise obtaining an indicator identifying the audio source is a target audio source within the audio scene. The method may further comprise determining the audio souce is a target audio source based on the position of the audio source and the listerner position. The capture area may be defined relative to: at least one microphone position or at least one higher order ambisonics position; and a perimeter defined by at least two microphones positions or at least two higher order Ambisonics positions. The rendering parameter for assisting the rendering of an audio signal may comprise an exterior rendering projection radius value for the mapping of the audio source when the listener position is external to the capture area. The rendering parameter for assisting the rendering of an audio signal may further comprise an indicator that the exterior rendering projection radius value is an adaptive value, wherein mapping the audio source may comprise adaptively mapping the audio source when the indicator indicates that the exterior rendering projection radius value is an adaptive value. The exterior rendering projection radius value may define a distance for assisting the mapping of the audio source position to the distance perpendicular from the capture area. The method may further comprise determining spatial metadata based on the exterior rendering projection radius value, wherein generating at least one audio output may be further based on determined spatial metadata. The method may further comprise obtaining an audio data bitstream comprising audio data from at least one position within the audio scene associated with the at least one audio source, wherein generating the at least one audio output may be further based on the audio data bitstream. The audio data may comprise at least three audio signals from: at least three microphones; or at least three higher order Ambisonics, wherein the at least three microphones or at least three higher order ambisonics audio signals are associated with positions within the audio scene. The position of the audio source may be obtained based on the positions of the at least three audio signals. Defining a rendering parameter for assisting the rendering of an audio signal when the listener position is external to the capture area when the rendering parameter is the exterior rendering projection radius value may comprise: triangulating positions within the audio scene of the at least three microphones or the at least three higher order ambisonics; identifying the position of the audio source within the audio scene is exterior to the triangulation of the positions within the audio scene of the at least three microphones or the at least three higher order ambisonics; determining the exterior rendering projection radius value from a distance between the position of the audio source within the audio scene and a line between two closest positions of the at least three microphones or the at least three higher order ambisonics. The method may further comprise determining spatial metadata based on the rendering parameter. Determining spatial metadata based on the rendering parameter may comprise: determining a spatial metadata parameter based on the listener position and the audio data bitstream; and applying an adjustment to the determined metadata based on the rendering parameter where the listener position is exterior to a triangulation of audio data bitstream sources. The information associated with the audio source may further comprise a position of the audio source within the audio scene. According to a third aspect there is provided an apparatus for assisting six degrees-of-freedom rendering of an audio scene when a listener position is external to a capture area, the apparatus comprising means configured to perform:, obtaining information associated with an audio source; determining a position of the audio source relative to the capture area; when the position of the audio source is external to the capture area, obtaining a parameter; defining a rendering parameter for assisting the rendering of an audio signal when the listener position is external to the capture area; and encoding at least the rendering parameter based on the provided parameter. The capture area may be defined relative to: at least one microphone position or at least one higher order ambisonics position; and a perimeter defined by at least two microphones positions or at least two higher order Ambisonics positions. The rendering parameter for assisting the rendering of an audio signal may comprise an exterior rendering projection radius value, for mapping the audio source as a target audio source when the listener position is external to the capture area. The rendering parameter for assisting the rendering of an audio signal may further comprise an indicator that the exterior rendering projection radius value is an adaptive value. The exterior rendering projection radius value may define a distance for assisting a mapping of the audio source position to a distance perpendicular from either the at least one microphone position or at least one higher order ambisonics position or the perimeter. The means configured to perform defining a rendering parameter for assisting the rendering of an audio signal when the listener position is external to the capture area when the rendering parameter is the exterior rendering projection radius value may further be configured to perform: determining the exterior renering projection radius value based on an input; determining a quality check on the determined exterior rendering projection radius value; and providing the exterior renering projection radius value based on an input as the exterior rendering projection value when the quality check is passed or modifying the exterior renering projection radius value otherwise. The means may further be configured to perform: obtaining audio data associated with the at least one audio source; and encoding the audio data to generate an audio data bitstream. The means configured to perform obtaining audio data associated with the at least one audio source may further be configured to perform obtaining at least three audio signals from: at least three microphones; or at least three higher order Ambisonics, wherein the at least three microphones or at least three higher order ambisonics audio signals are associated with positions within the audio scene. The means configured to perform determining the position of the audio source relative to the capture area may further be configured to perform determining the position of the audio source based on the at least three audio signals and positions associated with the at least three microphones or the at least three higher order Ambisonics. The means may further be configured to perform determining the position of the audio source is external by: triangulating positions within the audio scene of the at least three microphones or the at least three higher order ambisonics; identifying the position of the audio source within the audio scene is exterior to the triangulation of the positions within the audio scene of the at least three microphones or the at least three higher order ambisonics. The means may further be configured to perform determining the exterior rendering projection radius value from a distance between the position of the audio source within the audio scene and a line between two closest positions of the at least three microphones or the at least three higher order ambisonics. The information associated with the audio source may further comprise a position of the audio source within the audio scene. The means may further be configured to perform receiving a listener position, wherein the information indicating the audio source is a target audio source within the audio scene may be based on the distance between an audio source position and the listener position. According to a fourth aspect there is provided an apparatus for six degrees-of-freedom rendering of an audio scene when a listener position is external to a capture area, the apparatus comprising means configured to perform: obtaining information associated with an audio souce; obtaining a rendering parameter for assisting the rendering of an audio signal when the listener position is external to the capture area; obtaining the listener position, the listener position being external to the capture area and within the audio scene; mapping a position of the audio source to a mapped position around the listener position based on the rendering parameter; generating at least one audio output based on the mapped position within the audio scene to achieve a localized rendering with respect ot the listener position. The means may further be configured to perform obtaining an indicator identifying the audio source is a target audio source within the audio scene. The means may further be configured to perform determining the audio souce is a target audio source based on the position of the audio source and the listerner position. The capture area may be defined relative to: at least one microphone position or at least one higher order ambisonics position; and a perimeter defined by at least two microphones positions or at least two higher order Ambisonics positions. The rendering parameter for assisting the rendering of an audio signal may comprise an exterior rendering projection radius value for the mapping of the audio source when the listener position is external to the capture area. The rendering parameter for assisting the rendering of an audio signal may further comprise an indicator that the exterior rendering projection radius value is an adaptive value, wherein the means configured to perform mapping the audio source may further be configured to perform adaptively mapping the audio source when the indicator indicates that the exterior rendering projection radius value is an adaptive value. The exterior rendering projection radius value may define a distance for assisting the mapping of the audio source position to the distance perpendicular from the capture area. The means may further be configured to perform determining spatial metadata based on the exterior rendering projection radius value, wherein the means may further be configured to perform generating at least one audio output further based on determined spatial metadata. The means may further be configured to perform obtaining an audio data bitstream comprising audio data from at least one position within the audio scene associated with the at least one audio source, wherein the means configured to perform generating the at least one audio output may further perform generating the at least one audio output based on the audio data bitstream. The audio data may comprise at least three audio signals from: at least three microphones; or at least three higher order Ambisonics, wherein the at least three microphones or at least three higher order ambisonics audio signals are associated with positions within the audio scene. The position of the audio source may be obtained based on the positions of the at least three audio signals. The means configured to perform defining a rendering parameter for assisting the rendering of an audio signal when the listener position is external to the capture area when the rendering parameter is the exterior rendering projection radius value may be configured to perform: triangulating positions within the audio scene of the at least three microphones or the at least three higher order ambisonics; identifying the position of the audio source within the audio scene is exterior to the triangulation of the positions within the audio scene of the at least three microphones or the at least three higher order ambisonics; determining the exterior rendering projection radius value from a distance between the position of the audio source within the audio scene and a line between two closest positions of the at least three microphones or the at least three higher order ambisonics. The means may further be configured to perform determining spatial metadata based on the rendering parameter. The means configured to perform determining spatial metadata based on the rendering parameter may further be configured to perform: determining a spatial metadata parameter based on the listener position and the audio data bitstream; and the means configured to perform applying an adjustment to the determined metadata may be based on the rendering parameter where the listener position is exterior to a triangulation of audio data bitstream sources. The information associated with the audio source may further comprise a position of the audio source within the audio scene. According to a fifth aspect there is provided an apparatus for assisting six degrees-of-freedom rendering of an audio scene when a listener position is external to a capture area, the apparatus comprising at least one processor and at least one memory storing instructions that, when executed by the at least one processor, cause the system at least to perform: obtaining information associated with an audio source; determining a position of the audio source relative to the capture area; when the position of the audio source is external to the capture area, obtaining a parameter; defining a rendering parameter for assisting the rendering of an audio signal when the listener position is external to the capture area; and encoding at least the rendering parameter based on the provided parameter. The capture area may be defined relative to: at least one microphone position or at least one higher order ambisonics position; and a perimeter defined by at least two microphones positions or at least two higher order Ambisonics positions. The rendering parameter for assisting the rendering of an audio signal may comprise an exterior rendering projection radius value, for mapping the audio source as a target audio source when the listener position is external to the capture area. The rendering parameter for assisting the rendering of an audio signal may further comprise an indicator that the exterior rendering projection radius value is an adaptive value. The exterior rendering projection radius value may define a distance for assisting a mapping of the audio source position to a distance perpendicular from either the at least one microphone position or at least one higher order ambisonics position or the perimeter. The apparatus caused to perform defining a rendering parameter for assisting the rendering of an audio signal when the listener position is external to the capture area when the rendering parameter is the exterior rendering projection radius value may be caused to perform: determining the exterior renering projection radius value based on an input; determining a quality check on the determined exterior rendering projection radius value; and providing the exterior renering projection radius value based on an input as the exterior rendering projection value when the quality check is passed or modifying the exterior renering projection radius value otherwise. The apparatus may be further caused to perform: obtaining audio data associated with the at least one audio source; and encoding the audio data to generate an audio data bitstream. The apparatus caused to perform obtaining audio data associated with the at least one audio source may be caused to perform obtaining at least three audio signals from: at least three microphones; or at least three higher order Ambisonics, wherein the at least three microphones or at least three higher order ambisonics audio signals are associated with positions within the audio scene. The apparatus caused to perform determining the position of the audio source relative to the capture area may be caused to perform determining the position of the audio source based on the at least three audio signals and positions associated with the at least three microphones or the at least three higher order Ambisonics. The apparatus may be caused to perform determining the position of the audio source is external by: triangulating positions within the audio scene of the at least three microphones or the at least three higher order ambisonics; identifying the position of the audio source within the audio scene is exterior to the triangulation of the positions within the audio scene of the at least three microphones or the at least three higher order ambisonics. The apparatus may be caused to perform determining the exterior rendering projection radius value from a distance between the position of the audio source within the audio scene and a line between two closest positions of the at least three microphones or the at least three higher order ambisonics. The information associated with the audio source may further comprise a position of the audio source within the audio scene. The apparatus may be caused to perform receiving a listener position, wherein the information indicating the audio source is a target audio source within the audio scene may be based on the distance between an audio source position and the listener position. According to a sixth aspect there is provided an apparatus for six degrees-of-freedom rendering of an audio scene when a listener position is external to a capture area, the apparatus comprising at least one processor and at least one memory storing instructions that, when executed by the at least one processor, cause the system at least to perform: obtaining information associated with an audio souce; obtaining a rendering parameter for assisting the rendering of an audio signal when the listener position is external to the capture area; obtaining the listener position, the listener position being external to the capture area and within the audio scene; mapping a position of the audio source to a mapped position around the listener position based on the rendering parameter; generating at least one audio output based on the mapped position within the audio scene to achieve a localized rendering with respect ot the listener position. The apparatus may be caused to perform obtaining an indicator identifying the audio source is a target audio source within the audio scene. The apparatus may be caused to perform determining the audio souce is a target audio source based on the position of the audio source and the listerner position. The capture area may be defined relative to: at least one microphone position or at least one higher order ambisonics position; and a perimeter defined by at least two microphones positions or at least two higher order Ambisonics positions. The rendering parameter for assisting the rendering of an audio signal may comprise an exterior rendering projection radius value for the mapping of the audio source when the listener position is external to the capture area. The rendering parameter for assisting the rendering of an audio signal may further comprise an indicator that the exterior rendering projection radius value is an adaptive value, wherein mapping the audio source may comprise adaptively mapping the audio source when the indicator indicates that the exterior rendering projection radius value is an adaptive value. The exterior rendering projection radius value may define a distance for assisting the mapping of the audio source position to the distance perpendicular from the capture area. The apparatus may be caused to perform determining spatial metadata based on the exterior rendering projection radius value, wherein generating at least one audio output may be further based on determined spatial metadata. The apparatus may be caused to perform obtaining an audio data bitstream comprising audio data from at least one position within the audio scene associated with the at least one audio source, wherein generating the at least one audio output may be further based on the audio data bitstream. The audio data may comprise at least three audio signals from: at least three microphones; or at least three higher order Ambisonics, wherein the at least three microphones or at least three higher order ambisonics audio signals are associated with positions within the audio scene. The position of the audio source may be obtained based on the positions of the at least three audio signals. The apparatus caused to perform defining a rendering parameter for assisting the rendering of an audio signal when the listener position is external to the capture area when the rendering parameter is the exterior rendering projection radius value may be caused to perform: triangulating positions within the audio scene of the at least three microphones or the at least three higher order ambisonics; identifying the position of the audio source within the audio scene is exterior to the triangulation of the positions within the audio scene of the at least three microphones or the at least three higher order ambisonics; determining the exterior rendering projection radius value from a distance between the position of the audio source within the audio scene and a line between two closest positions of the at least three microphones or the at least three higher order ambisonics. The apparatus may be further caused to perform determining spatial metadata based on the rendering parameter. The apparatus caused to perform determining spatial metadata based on the rendering parameter may be further caused to perform: determining a spatial metadata parameter based on the listener position and the audio data bitstream; and applying an adjustment to the determined metadata based on the rendering parameter where the listener position is exterior to a triangulation of audio data bitstream sources. The information associated with the audio source may further comprise a position of the audio source within the audio scene. According to a seventh aspect there is provided an apparatus for assisting six degrees-of-freedom rendering of an audio scene when a listener position is external to a capture area, the apparatus comprising: obtaining circuitry configured to obtain information associated with an audio source; determining circuitry configured to determine a position of the audio source relative to the capture area; obtaining circuitry configured to, when the position of the audio source is external to the capture area, obtain a parameter; defining circuitry configured to define a rendering parameter for assisting the rendering of an audio signal when the listener position is external to the capture area; and encoding circuitry configured to encode at least the rendering parameter based on the provided parameter. According to an eighth aspect there is provided an apparatus for six degrees-of-freedom rendering of an audio scene when a listener position is external to a capture area, the apparatus comprising: obtaining circuitry configured to obtain information associated with an audio souce; obtaining circuitry configured to obtain a rendering parameter for assisting the rendering of an audio signal when the listener position is external to the capture area; obtaining circuitry configured to obtain the listener position, the listener position being external to the capture area and within the audio scene; mapping circuitry configured to map a position of the audio source to a mapped position around the listener position based on the rendering parameter; generating circuitry configured to generate at least one audio output based on the mapped position within the audio scene to achieve a localized rendering with respect ot the listener position. According to a ninth aspect there is provided a computer program comprising instructions [or a computer readable medium comprising instructions] for causing an apparatus, for assisting six degrees-of-freedom rendering of an audio scene when a listener position is external to a capture area, the apparatus caused to perform at least the following: obtaining information associated with an audio source; determining a position of the audio source relative to the capture area; when the position of the audio source is external to the capture area, obtaining a parameter; defining a rendering parameter for assisting the rendering of an audio signal when the listener position is external to the capture area; and encoding at least the rendering parameter based on the provided parameter. According to a tenth aspect there is provided a computer program comprising instructions [or a computer readable medium comprising instructions] for causing an apparatus, for six degrees-of-freedom rendering of an audio scene when a listener position is external to a capture area, the apparatus caused to perform at least the following: obtaining information associated with an audio souce; obtaining a rendering parameter for assisting the rendering of an audio signal when the listener position is external to the capture area; obtaining the listener position, the listener position being external to the capture area and within the audio scene; mapping a position of the audio source to a mapped position around the listener position based on the rendering parameter; generating at least one audio output based on the mapped position within the audio scene to achieve a localized rendering with respect ot the listener position. According to an eleventh aspect there is provided a non-transitory computer readable medium comprising program instructions for causing an apparatus, for assisting six degrees-of-freedom rendering of an audio scene when a listener position is external to a capture area, to perform at least the following: obtaining information associated with an audio source; determining a position of the audio source relative to the capture area; when the position of the audio source is external to the capture area, obtaining a parameter; defining a rendering parameter for assisting the rendering of an audio signal when the listener position is external to the capture area; and encoding at least the rendering parameter based on the provided parameter. According to a twelfth aspect there is provided a non-transitory computer readable medium comprising program instructions for causing an apparatus, for six degrees-of-freedom rendering of an audio scene when a listener position is external to a capture area, to perform at least the following: obtaining information associated with an audio souce; obtaining a rendering parameter for assisting the rendering of an audio signal when the listener position is external to the capture area; obtaining the listener position, the listener position being external to the capture area and within the audio scene; mapping a position of the audio source to a mapped position around the listener position based on the rendering parameter; generating at least one audio output based on the mapped position within the audio scene to achieve a localized rendering with respect ot the listener position. According to a thirteenth aspect there is provided an apparatus, for assisting six degrees-of-freedom rendering of an audio scene when a listener position is external to a capture area, comprising: means for obtaining information associated with an audio source; means for determining a position of the audio source relative to the capture area; means for, when the position of the audio source is external to the capture area, obtaining a parameter; means for defining a rendering parameter for assisting the rendering of an audio signal when the listener position is external to the capture area; and means for encoding at least the rendering parameter based on the provided parameter. According to a fourteenth aspect there is provided an apparatus, for six degrees-of-freedom rendering of an audio scene when a listener position is external to a capture area, comprising: means for obtaining information associated with an audio souce; means for obtaining a rendering parameter for assisting the rendering of an audio signal when the listener position is external to the capture area; means for obtaining the listener position, the listener position being external to the capture area and within the audio scene; means for mapping a position of the audio source to a mapped position around the listener position based on the rendering parameter; means for generating at least one audio output based on the mapped position within the audio scene to achieve a localized rendering with respect ot the listener position. According to an fifteenth aspect there is provided a computer readable medium comprising instructions for causing an apparatus, for assisting six degrees-of-freedom rendering of an audio scene when a listener position is external to a capture area, to perform at least the following: obtaining information associated with an audio source; determining a position of the audio source relative to the capture area; when the position of the audio source is external to the capture area, obtaining a parameter; defining a rendering parameter for assisting the rendering of an audio signal when the listener position is external to the capture area; and encoding at least the rendering parameter based on the provided parameter. According to a sixteenth aspect there is provided a computer readable medium comprising instructions for causing an apparatus, for six degrees-of-freedom rendering of an audio scene when a listener position is external to a capture area, to perform at least the following: obtaining information associated with an audio souce; obtaining a rendering parameter for assisting the rendering of an audio signal when the listener position is external to the capture area; obtaining the listener position, the listener position being external to the capture area and within the audio scene; mapping a position of the audio source to a mapped position around the listener position based on the rendering parameter; generating at least one audio output based on the mapped position within the audio scene to achieve a localized rendering with respect ot the listener position. An apparatus comprising means for performing the actions of the method as described above. An apparatus configured to perform the actions of the method as described above. A computer program comprising program instructions for causing a computer to perform the method as described above. A computer program product stored on a medium may cause an apparatus to perform the method as described herein. An electronic device may comprise apparatus as described herein. A chipset may comprise apparatus as described herein. Embodiments of the present application aim to address problems associated with the state of the art. Summary of the Figures For a better understanding of the present application, reference will now be made by way of example to the accompanying drawings in which: Figures 1a to 1g show example audio scenes within which a user can freely move according to some embodiments; Figure 2 shows schematically an example apparatus suitable for implementing some emboidments; Figure 3 shows a flow diagram of the example apparatus as shown in Figure 2 for implementing some emboidments; Figure 4 shows an example direction parameter adjustment based on exterior projection radius according to some embodiments; Figures 5a to 5c show example projections of outside informed source positions and listener positions from the edge of the HOA source area according to some emboidments; Figures 6a and 6b shows an example projection of outside informed source positions and listener positions to 1.0m from the edge of the HOA source area for scenes with 2 or 1 HOA sources; Figure 7 shows an example system within which some embodiments can be implemented; Figure 8 shows a flow diagram of an example encoder side processing according to some embodiments; Figure 9 shows a flow diagram of a further example encoder side processing according to some embodiments; Figure 10 shows a flow diagram of an example decoder side processing according to some embodiments; Figure 11 shows a flow diagram of a further example decoder side processing according to some embodiments; and Figure 12 shows apparatus suitable for implementing some embodiments wherein a capture apparatus can be separate from the rendering apparatus elements. Embodiments of the Application The concept as discussed herein in further detail with respect to the following embodiments is related to the rendering of audio scenes. As discussed above 6DoF is presently commonplace in virtual reality, such as VR games, where movement at the audio scene is straightforward to render as all spatial information is readily available (i.e., the position of each sound source as well as the audio signal of each source separately). In the following examples the audio signal sets are generated by microphones (or microphone-arrays). For example a microphone arrangement may comprise one or more microphones and generate for the audio signal set one or more audio signals. In some embodiments the audio signal set comprises audio signals which are virtual or generated audio signals (for example a virtual speaker audio signal with an associated virtual speaker location). In some embodiments the microphone-arrays are furthermore separate from or physically located away from any processing apparatus, however this does not preclude examples where the microphones are located on the processing apparatus or are physically connected to the processing apparatus. The current MPEG-I Immersive audio standard (ISO / IEC 23090-4 WD3) renderer such as described in GB2007710.8 supports 6 degrees-of-freedom (6DoF) rendering of audio scenes comprising multiple first order or higher-order Ambisonics (FOA, HOA) microphone recordings or synthesized signals. The renderer is able to provide a binaural signal at the listener position (and orientation) based on the recorded FOA / HOA signals and their positions. That is, the renderer is able to provide a binaural signal at a non-sampled position in the scene, thus providing a 6DoF experience for the listener. For example Figure 1a shows an example scene 100 with microphone positions, shown in Figure 1a as microphone positions rm 101, m2 103, m3 105 forming a first triangle (with one side in common with the second triangle and another side in common with the third triangle), microphone positions m4 107, m2 103, m3 105 forming a second triangle (with one side in common with the first triangle and another side in common with the fourth triangle), microphone positions rm 101, ms 109, m3105 forming a third triangle (with one side in common with the first triangle and another side in common with the fourth triangle), and microphone positions m4107, ms 109, m3105 forming a fourth triangle (with one side in common with the second triangle and another side in common with the third triangle). Additionally is shown an example listener position p / 111 which in Figure 1a is within the first triangle. The (MPEG-I) immersive audio renderer can be configured to utilize information (e.g., position) about audio sources present in the scene (e.g., during the recording), as shown in UK patent application GB2020239.6. The positions of any of the audio sources present in the recorded or synthetic audio scene may be provided as input information to the renderer in addition to the audio signals and positions of the FOA or HOA microphones. Using this additional information about the audio sources allows the renderer to provide improved sound quality through improved localization and distance attenuation behaviour for the known sources. To achieve this, the renderer is configured to perform beamforming (from a FOA / HOA signal) towards a known source to estimate the source properties (energy at different frequency bands). Based on this and the position of the known source, the renderer is able to determine from which direction, from the listener’s perspective, and in which frequency bands, how much energy is being contributed by the known source. For example as shown in Figure 1b, the example audio scene 100 shown in Figure 1a is modified by showing the positions of two ‘known’ sources ps? 131 and pS2121, and the beamforming projecting from the microphone rm 101 to the source pS2121 and projecting from the microphone m2103 to the source ps? 131. This type of rendering is known as ‘interior’ rendering where the listener is located within in the interior of the area defined by the microphones. The example shown in Figure 1c, is one where the example audio scene 100 differs from the one shown in Figure 1 a in that the listener position p / 111 which in Figure 1 a is within the first triangle is located outside any of the triangles, in other words, is external to the HOA capture region. Rendering an output audio signal in such circumstances is known as ‘exterior’ rendering. An example of exterior rendering is shown in Figures 1d and 1e and is described in further detail in EP21201766.9. The interior rendering methods, as discussed above determines spatial parameters at the listener position based on weighted interpolation of spatial parameters calculated from the microphone signals of the microphones defining the triangle that the listener is in. The closer a listener is to a microphone, the more weight is given to the spatial parameters calculated at that microphone position. However, when the listener moves outside of the microphone area, and thus is not inside any of the triangles, a weighted interpolation method such as described above cannot be used. Thus previously the rendering of exterior listening positions employs spatial parameters interpolated from the spatial parameters calculated at the microphones defining the outside edge that the listener is closest to and modify the parameters based on the distance of the listener to the edge and an exterior rendering radius. In some situations a direction of arrival and diffuseness parameters (which are a subset of spatial parameters) can be modified based on an assumption that audio sources outside of the capture area are approximately at a distance from the microphone array area equal to the exterior rendering radius. For example as shownin Figure 1d the listener position p / 141 is projected to the side of the triangle connecting the two closest microphone positions, in other words point 143 between microphone positions mi 101, m2 103, with the exterior rendering radius modified based on the distance of the known sources from the microphone area and the position of the listener. The exterior rendering radius is set to the distance of the closest informed source to the listener form the edge of the microphone area. Figure 1 e further shows the effect of application of the sound direction, Where as sound direction-of-arrival is adjusted based on assumption that sound sources are on the circle 153. In these embodiments the distance to the sound source is not known, only direction information for frequency bands is known. The radius of the circle can be an estimate of distance of outside audio sources, this is currently a constant in the MPEG-I immersive Audio renderer implementation as defined by ISO / IEC 23090-4 WD4 (or working draft 4 of the MPEG-I Immersive audio). This in the implementation standard has the value of 4.0m. In this example the direction of arrival of the sound source changes as listener is moving and can be implemented by adjusting spatial parameters estimated for the projected listener position and using the adjusted spatial parameters as the estimate for the spatial parameters at the listener position. An example scenario of such a scene could be a recording of a couple of musicians playing on a busy street. There are people around the musicians as well as people walking on the street. Some people on the street are listening and contribution to the audio scene by applauding or talking. The song is recorded using multiple Ambisonics mics, placed some distance apart. The positions of at least some of the musicians are known. The scene is captured and then subsequently turned into a VR scene by the content creator. The content creator creates a scene with associated scene description with the positions of the recording microphones and any of the known sources. The scene description can be in any suitable format, including, Encoder Input Format (EIF) or any other suitable format. The scene description is then encoded into a bitstream along with the audio and is provided to the listener for consumption via VR, for example. However there can be potential problems in obtaining believable audio source localizations when the listener is outside of the HOA source region for sources which are outside the HOA source region using the known methods.. In such a scenario, an assumed distance (or radius) between the listener position on the edge at the boundary of the HOA source region and the audio source can be used to achieve believable localization performance. However, the audio sources positions outside the HOA source region can change for different audio scenes. Furthermore, there may be more than one audio source which can result in a nonunique distance which should be used to achieve desired localization performance and which can be further impacted by non-signal properties such as content creator intent. Some audio sources may have greater subjective significance than others or there may need to be a balanced compromise for the localization accuracy. The problem is further explained in context of MPEG-I Immersive audio implementation as an example illustration as shown by Figres 1f and 1g. Figure 1f shows spatial metadata direction information adjusted based on exterior radius 171 to get estimate of spatial metadata at listener position. If the exterior rendering radius 181 (as shown in Figure 1g) does not match the distance to the audio sources 151, 161 outside the HOA source 101, 103, 105 constellation boundary, the adjustment employed to the direction-of-arrival parameters is not optimal. In other words, exterior rendering as described in EP21201766.9 does not produce effectively good results. As the discrepancy between the radius and the distance of the outside audio sources increases, the errors in the direction-of-arrival estimates increases. In some cases, the distances of the outside audio sources vary (some are closer, some further away) and an exterior radius that matches all distances is impossible to find. A single best value does not exist, and any determination is a compromise and should be set based on the content creator intent. Currently, at the time of drafting this document), the MPEG-I Immersive audio (ISO / IEC 23090-4) is undergoing standardization in MPEG WG6 (ISO / IETC JTC1 SC29 WG6) and is in the Work Draft state (WD4). in the MPEG-I Immersive audio renderer, the exterior rendering radius has a constant value of 4.0 meters and the content creator does not have control over the radius value. In Figure 1f, since the exterior projection radius 171 is close to the outside audio sources 151, 161, the modified DOA parameters 191, 193 are a reasonable approximation to the correct directions 192, 914 respectively. In Figure 1g, the exterior projection radius 181 does not match the outside audio sources and the modified DOA directions 195, 197 are significantly different to the correct directions 192, 194 causing localization issues. In the case of informed outside sources (i.e. audio sources in the scene with known audio sources positions outside of the microphone area, which need not be captured with a close-up microphone), the current approaches (for example MPEG-I Immersive audio) employed in audio rendering adjusts the exterior rendering radius according to the closest informed source to the user. As the closest informed source to the listener changes, there is an abrupt change in the radius which may cause unwanted abrupt changes in the rendered audio. Furthermore, there may be additional audio sources outside of the microphone area in addition to the known sources and setting the radius just based on the known sources can produce errors. For example, if there is a single exterior informed source in the scene and it is known that no other audio sources are present, the optimal solution is to set the exterior rendering radius as the distance from the microphone area to the exterior informed source. However, the presence of audio sources other than the informed sources is more common, especially in real or live event recordings. Hence, methods are required for setting the exterior rendering radius so that optimal rendering quality according to the content creator intent is obtained for the case when there are: Only audio sources that are not informed (or no informed sources) outside the HOA capture region; Presence of audio sources in the scene (either within or outside the HOA capture region), in addition to the informed sources outside the HOA capture; an audio scene with a single HOA source or microphone capture position, with presence of informed sources and audio sources without known positions (in this case all audio sources and informed audio sources are exterior or outside the HOA capture region); an audio scene with a single HOA source or microphone capture position, without any audio source with known audio source position. As discussed above the concept addressed by the following embodiments relates to rendering of audio signals and specifically (binaural) rendering of 6DoF audio scenes captured with multiple higher-order Ambisonics microphones (HOA) where there is provided a method for rendering when the listener is outside of the capture area to achieve believable localization rendering quality by control of the setting the exterior projection radius based on content creator instructions or content creator rendering control or information or content creator rendering control information delivered as bitstream as part of the MPEG-I Immersive audio bitstream (or any other suitable bitstream) to the renderer. In some emboidments, the believable localization rendering quality prioritizes improved localization for the desired audio source outside the HOA source region. Furthermore in some embodiments, the content creator instructions comprise at least an exterior rendering projection radius determined by the content creator during bitstream creation (or some point in the capture or encoding operations). The exterior rendering projection radius can be signalled as part of the rendering metadata bitstream relevant for 6DoF HOA rendering. The content creator in some embodiments is configured to determine the exterior rendering projection radius based on the subjective priority of localization performance for the one or more audio sources in the audio scene. The audio sources may furthermore be sources without a precise known position. In some further embodiments, the exterior projection radius is modified, or adjusted or controlled by the renderer based on the known source positions (or informed sources) and listener position. In these embodiments, the known source positions or informed sources refer to audio sources in the audio scene whose position is known but not captured as an audio object (for example, as an audio object with close-up microphone). In summary, the embodiments as described herein show when the listener is outside of the microphone capture area, audio sources are mapped to a projection radius around the listener. The microphone capture area (or HOA source region or HOA capture region) is defined as the area formed by connecting the peripheral HOA sources. A higher quality of rendering can be obtained when the projection radius matches the distance of outside audio source to the edge of the capture area. In some embodiments, the projection radius can be set or controlled based on content creator instructions in the bitstream / scene description in order to prioritize based on a certain audio source of interest or a compromise radius in case of multiple audio sources of interest. In some further embodiments the renderer is configured to set or control the projection radius based on based on position information of audio sources (e.g., informed audio sources) outside of the capture area. In some other embodiments, the signalled projection radius (in the bitstream) is employed as a default value but can be superseded or adjusted by the user with interactive selection during content consumption or modified by dynamic updates arriving during content consumption. In an example case of MPEG-I Immersive audio implementation, this information can be delivered as a run time dynamic update. With respect to Figure 2 is shown a schematic view of an example apparatus within which some embodiments can be employed. The example in Figure 2 shows how embodiments can be implemented on a MPEG-I Immersive audio system for 6DoF Multi-Point HOA rendering of audio scenes comprising HOA / FOA content (recorded or synthesized). It would be understood that the embodiments can be employed to render such a scene using other encoded implementations. In some embodimements the renderer comprises a pre-precessor 201. The pre-processor 201 is configured to initialize the rendering after receiving information of the scene such as positions of HOA / FOA sources p1 Ns 202 and also receiving head-related impulse responses (HRIRs) 200. The pre-processor 201 is configured to obtain the positions 202 and performs Delaunay triangulation to provide a set of triangles TrNr 212 that partition the scene into triangle sections. This triangulation is for example shown in the Figures 1a to 1g. The pre-processor 201 is also configured to convert the head-related impulse responses (HRIRs) 200 which are converted to frequency domain head-related transfer functions (HRTF) 220. In some embodiments this can be implemented by a short-term Fourier transform. In a MPEG-I Immersive audio case, the alias-free STFT algorithm is used such as described in Pulkki, V., S. Delikaris-Manias, and A. Politis, Parametric Time-frequency Domain Spatial Audio. 2018: John Wiley &Sons, Incorporated. In some embodiments the HRTFs 220 can be used to calculate an Ambisonics-to-binaural transform matrix MH0A2bin(b), for each frequency band b. In some embodiments the renderer further comprises a position preprocessor 203. The position pre-processor 203 is configured to determine HOA / FOA sources that are close to the listener for later processing purposes. During rendering, for each input frame j, the position pre-processor 203 is configured to take as an input the listener position pt 204, the HOA / FOA source positions p^Ns 202 and the set of triangles Nt 212 created in the pre-processor 201. Based on the input, the position pre-processor 203 determines interpolation weights wc(i,j) 216 for the HOA / FOA sources pt 202. This is done by determining in which triangle Tt, the listener is in and calculating the barycentric coordinates for the triangle Tt and the listener position. The barycentric coordinates are used as the weights. The weights sum to one and the closer the listener is to an HOA / FOA source, the higher the weight will be. At an edge of a triangle, the weight for the HOA / FOA source that is not part of that edge is 0. The weights wc(i,j) 216 and the triangle that the listener is in (active triangle) TA(j) 214 are provided as outputs. In some embodiments, when the listener moves from a triangle to another, the switching of the active triangle may be delayed, and only switched after a few frames of audio. This is because processing of the audio for HOA / FOA sources for the new triangle requires a few frames of audio to provide meaningful output. Thus, the active triangle is not always the triangle that the listener is in. The position preprocessor 203 can also determines the HOA / FOA source that is closest to the listener. In some embodiments the renderer comprises a spatial analyzer 211. The spatial analyzer 211 provides spatial metadata parameters for frames of HOA / FOA signals that positioned near the listener. These are later used, in the metadata interpolator 209, to estimate spatial metadata parameters at the listener position. The spatial analyzer 211 is configured to receive as an input a frame (for example, 256 samples) of HOA / FOA source signals sESD(i,f) 210 for each source i and frame j and the current active triangle TA(f) 214. For each HOA / FOA source i, belonging to the triangle TA(j} 214, the spatial analyzer 211 performs STFT processing to obtain time-frequency domain signals S(i,j,k) 222, where k refers to a sub-frame (for example, 128 samples). The spatial analyzer 211 then calculates spatial metadata from the time-frequency domain signals. The spatial metadata comprises the energy, direction information (azimuth and elevation) and diffuseness information (direct-to-total energy ratio) and is obtained as follows: First, a signal analysis vector s(i,j,k,b) is calculated: s(i,j,k,b) = ’ Sbl(i,j,k) * 1.0 ’ ^,2(07, fc) *0.5774 ^,3(07, k) *0.5774 k) *0.5774 where S^i,^ is the value in matrix S(i,j,k) corresponding to channel c and frequency bin b. From the signal analysis vector, a signal intensity vector is calculated: s^ij, k,b) k.b) -si(i>j>k,b) * k,6)T *s2(ij, k, b) ■ * s3(ij, where sc(i,j, k, b) denotes the complex conjugate of sc(i,j, k, by Signal energy is then calculated as follows: 1 4 e(i,j,k,b) = — sc(i,j,k,b) * sc(i,j,k,b) C=1 An average intensity vector and average energy is calculated as follows: N°f Nsf The direction data (azimuth and elevation) are calculated as follows: 6(i,j,b) = atan2(i2(i,j, h), &)) ii (t j, b)~ Mkj, by where in(i,j, b) is the nth element of the average intensity vector by S(kj, b) is the azimuth and b) is the elevation. The direct-to-total energy ration is calculated as follows: The energy for the subframes k are then obtained as follows: e(i,j, k, b) = e(i, j, b), k G l..NSf Thus the output also comprises 0(i,j,b) 228, <p(i,j,b) 230 r(i,j,b) 232 and e(i,J,k,b) 224. The renderer furthermore comprises a spatial metadata interpolator 209 which is configured to provide an estimate of the spatial metadata at the listener position based on the spatial metadata for the HOA / FOA sources belonging to the triangle that the listener is in, and the interpolation weights calculated in the position pre-processing block. First, the spatial metadata is converted into vector form: —sin(0(i, j, b)) cos(<jo(i,j, b)) sin(<p(ij,b)) —cos{<p(i,j, b)) cos(<p(i, j, b)) The vectors are rotated according to the listener’s head and source orientations: KiJ,b) = R head (j)Rsource An interpolated spatial metadata vector is then calculated by a weighted average of spatial metadata vectors: where the interpolation weights are the barycentric coordinates calculated in the position pre-processing block. And finally, the interpolated spatial metadata vector is converted to spatial metadata parameters as follows: Azimuth: 0(j, k, b) = atan2(—14( / , k, b), —v3(j, k, b)) Elevation: (p(j, k, b} = atan2 (-v2( / , k, b), 7(-^( / , k, b))2 + k, b))2 Direct-to-total energy ratio: f( / , k, b) = 7(^, ( / Ab))2 + (v2( / ,fc,b))2 + (v3(j,k,by)2 Energy: These §(J,k,b') 236, <p(J,k,b) 238, f(J,k,b) 240 and efj.k.b') 242 can be output. The signal interpolator 205 is configured to provide an “interpolated signal” at the listener position, that is, an estimate of the signal at the listener position. This is used later (in the mixer 207) in conjunction with the interpolated metadata at the listener position to provide the final binaural output. The interpolated signal SbiC(j,k) is obtained by taking the HOA / FOA signal that is closest to the listener and applying an EQ on the signal: Sb.ctj’k) = Geq(j,k,b)Sbc(mc(j),j,k) where mc(j) is index of the HOA source chosen for interpolation (closest to listener in most cases) and: The value S(j, k, b) 218 can be output to the mixer 207. The renderer further can comprise a mixer 207, which takes as an input the interpolated spatial metadata at the listener position and the interpolated signal at the listener position and provides the binaural time-frequency domain output signal. The mixer 207 can create a signal covariance matrix from the interpolated spatial metadata which describes the desired (or target) spatial characteristics of the signal at the listener position. An optimal mixing algorithm is then used to obtain a mixing matrix that when multiplied with the interpolated signal, the resulting signal is inline with the desired spatial characteristics. First, a binaural prototype signal is created from the interpolated signal: Sb,l(j>Nsf) — MH0A2bin(b^ * Rsh(j) * Bb,NCh(J’ 1) •" ^b,NCh(j’^sf\ Where Rsh(f) is a rotation matrix taking into account the listener and HOA / FOA source rotation and MHOA2btn(b) is the Ambisonics to binaural matrix. Then, a signal covariance matrix Cx is calculated for the prototype signal: C™w(j,b)=B(j,b)B(j,br Recursive averaging is applied to get the signal covariance matrix for frame Cx(j,b) = (1 - d)C™w(j,b) + dCx(j - l,b) Where d = 0.9. Next, a signal covariance matrix Cy is calculated from the interpolated spatial metadata at the listener position. First the direct portion of Cy is calculated: C^rect(J,b) = T ^0' k,b)f(j,k, h 'lllib where H(b, d) refers to the HRTF value at frequency bin b, in direction. Second, the diffuse portion of Cy is calculated. Nsf i) = ^(1 - r(j-, k. b))eQ, k, b-) Cdlrm k=l where: r ... l^HCb.dyH^b.d) =------------ Cy is then obtained as follows: C™w(j,b) = C^irectQ,b} + Cyiffuse(j,b') And recursive averaging: Cy(j,b) = (1 - d)C™w(j,b) + dCy(j - 1,6) where d = 0.9. The signal covariance matrices are then used to obtain mixing matrices which are used to obtain the binaural output like so: O(j, k, b) = M(j, k, b) * B(j — 1, k, b) * D(J, b) Where D(j, 6) is a decorrelated time-frequency domain signal obtained from a buffer of previous binaural signals B. The matrices M(j,k,b) and Mr(j,k,b) are obtained from the optimal mixing procedure outlined in []. After applying the mixing matrices on the binaural prototype signal B, the result output 0 244 has the spatial characteristics of the spatial metadata at the listener position. The renderer can furthermore comprise an output processor 213 which is configured to receive the obtained binaural output signal O(j,k,b) and perform an inverse STFT on it to produce the final time domain binaural output signal sOut(i,j) 246. With respect to Fiugre 3 is shown a flow diagram of the example operations of the renderer shown in Figure 2 according to some embodiments. For example there is shown by 301 in Figure 3, obtaining HRIR and positions p / Then as shown by 303 in Figure 3, pre-processing to generate Ti..nt and HRTFs. Furthermore then is shown obtaining p / in Figure 3 by 305. Then as shown in Figure 3 by 307, position-preprocessing to generate TaQ) and Wc(i,j) . Also is the operatiom of obtaining sesdCJ) as shown in Figure 3 by 309. Foillowing ths as shown in Figure 3 by 311 is apatial analyzing to generate S(i,j,k,b), e(i,j,k,b), q(i,j,b), j(i,j,b), r(i,j,b) 311. This can be followed by spatial metadata interpolating to generate e(j,k,b) q(j,k,b) j(j,k,b), r(j,k,b) as shown in Figure 3 by 315. Then can be signal interpolating to generate S(j,k,b) as shown in Fiugre 3 by 317. Then as shown in Figure 3 by 319 is generation of mixing O(j,k,b). Followed by the outputting of Spatialized audio sOut(i,j) (e.g., binaural, surround loudspeakers, Ambisonics) as shown by Figure 3 by 321. When the listener moves outside of the microphone area, the spatial metadata interpolator 209 is configured to adjust the interpolated spatial metadata (0(j,k,b\ $(j,k,b\ r(j,k,by) based on listener distance to the microphone area and the exterior rendering radius to give the listener a 6DoF listening experience outside of the microphone area. Furthermore when implementing exterior rendering the pre-processor 201 and the spatial analyzer 211 can be configured to implement the following. In the position pre-processing block, the triangle in which the listener is in is determined. This, as mentioned earlier, can be implemented by calculating barycentric coordinates for the listener position for all triangles T1..TNt found by the Delaunay triangulation. The listener is inside a triangle if all barycentric coordinates are positive. In the case there are no triangles for which all barycentric coordinates are positive, it is determined that the listener is outside of the microphone area. In such cases, the following can be implemented Firstly the closest HOA source (m^ and edge (ekJ) to the listener position (pL) is calculated Then a distance to the closest HOA sources to the listener is obtained by calculating the squared horizontal distance from the listener to the HOA sources as follows: (Pmk,x Pl,x) + (Pm^y Ph,y) The closest edge can then be determined by finding the distance Dw from the listener position pL to all edges ek!: / if dot^ — 0 , else where pLimJs the position of the listener in HOA source mk space: VL,mk Pt Pmk and where dotvn is the dot product between the normalized edge vector Vki and the normal of the edge n^. dotvn vkl • Tlki. If the closest HOA source to the listener is closer than any of the outside edges, the listener position is projected to the HOA source position: Vb,proj P^Mosest When this is not the case, the listener is projected on to the closest exterior edge Pl,proj WklPmk T (1 ™kdPmi The weights wtj are obtained by: == o 1--j-------— 11vkl I , else < dotvn “ dotvn In the spatial metadata interpolator 209, the interpolation weights can be determined when implementing exterior rendering and an adjustment to the obtained spatial metadata is performed as described below: Determining Interpolation weights If the listener was projected on a HOA source, the interpolation weight for that source is set to 1 and the interpolation weight for all other sources is set to 0. If the listener was projected to an outside edge, the interpolation weights are calculated as follows (for frame i): w(fcj) = wkl w(ZJ) = 1 - wkl Where k and I are the indices of the HOA sources defining the edge that the listener is closest to. Adjusting spatial metadata Spatial metadata is interpolated as described above, for the non-exterior rendering case (except with the interpolation weights calculated as directly above). After interpolation the spatial metadata is adjusted as follows. Figure 4 shows an example situation, where pL 403 is located external to the triangle. First a DOA vectoruDOX 407 is calculated (for each frequency band) from the interpolated spatial metadata: UDOA —sin(0) cos(<p) sin(<p) —cos(0) cos(<p) where 0 and cp are the interpolated azimuth and elevation parameters. Note that the audio frame ( / ) and frequency band indices ( / ) are not shown for clarity. A weighted DOA vector is also calculated: UDOA ~ UDOA^proj where Rproj 401 is the exterior projection radius. A modified DOA vectoruD(M mod 405 is calculated based on the projected pL: pLiPrOj 400 ^DOA.mod ~ Pl,pro J + Upp / j Pt A unit length version is also calculated: _ ^DOA,mod ^DOA,mod 1 T ]^DOA,mod | A modified direct-to-total energy ratio is also calculated: , „ ^DOAmodk rmOd = min (r,—------) Kpro j A directional weighting is applied to the modified parameters to modify parameters more heavily from sound sources outside the capturing region, while applying less modifications to sources inside the capturing region: 1 - 2 Wdir 22 (1 + ^-L.proj ‘ Where nLiProj is a “listener normal” which is a vector pointing away from the HOA source area. ^DOA,mod,weighted ^dir^DOA,mod T (1 ^dir^^DOA Yrnod,weighted mln (1, WcnrTmoci + (1 ^dir)^) Modified spatial metadata values are then obtained from uD0A,mod,weighted and processing is continued as in the non-exterior rendering case: Azimuth: 0 atan2 ^DOA,mod,weighted^’ ^DOA,mod,weighted3^ Elevation: ( 17 7 - atan2 ( -UD0A,mod,weighted 2>-yJ[~uDOA,mod,weighted^ + (-UDOAmod,weighted3) j Direct-to-total energy ratio: 1~mod,weighted As mentioned earlier, information about known audio sources in the scene may be used to improve rendering quality. The improvement comes via being able to calculate a more accurate target signal covariance matrix Cy via the use of beamforming to estimate the characteristics of the known audio sources. Note that no audio signal is required from the known audio sources, only their positions. This processing is described next, it is also described in further detail in GB2020239.6. The informed source information is provided by the content creator in the EIF as follows. <lnformedSource> An informed source description for MPHOA rendering. The informed sources represent the known audio sources within the scene. Attribute Type Flags Default Description id ID R Identifier position Position M Position listenerThreshold Value 0 3.0 Distance from the listener to the informed source in meters where the informed source is active. 0.0 distance disables the threshold. If not defined in EIF, 3.0 will be used. hoaSourceThreshold Value 0 3.0 Distance from the HOASources to the informed source in meters where the informed source is active. 0.0 distance disables the threshold. If not defined in EIF, 3.0 will be used. priorityValue Integer 0 0 Determines the processing priority between informed sources that are close to each other. The EIF information can be encoded into the bitstream using the following syntax: Syntax No. of bits Mnemonic lnformedSourcelnfoStruct() { informedSourceld = GetlD(); informedSourcePositionX; 31 uimsbf informedSourcePositionY; 31 uimsbf informedSourcePositionZ; 31 uimsbf listenerThresholdPresent; 1 bslbf hoaSourceThresholdPresent; 1 bslbf if (listenerThresholdPresent == True) { IpdlnformedSourceEnableThreshold; 16 uimsbf } if (hoaSourceThresholdPresent == True) { hpdlnformedSourceEnableThreshold; 16 uimsbf } priorityValue; 6 uimsbf In addition to the pre-processor operations described previously the preprocessor can be configured to implement the following when informed sources are present: First vectors from each informed source position pSmto HOA / FOA source position Pi is determined, v(i,m) = pSm - Pi which are then rotated according to the orientation of the HOA / FOA source: vrot(i,m) = RH0A(i)v(i,m) where Rhoa^S) is the rotation matrix for according to the orientation of HOA / FOA source i. The time-delay (in samples) between the HOA / FOA source / informed source pairs is calculated as follows: samples'^>^) * Js where c is the speed of sound and fs is the sampling frequency. The time-delay between two HOA sources for an informed source is obtained with: ^-samples rn) = dsamples^iz’ ^-samples^l'^) The delay in short-time Fourier transform (STFT) hop sizes shall be obtained with: . z. A , / d-samplesO-l’ ^2> dhopVi’ = round ---------------- \ ‘-'hop / where Lhov is the set hop length. In addition, for each informed source, the closest HOA / FOA source icjosest(m) is determined based on the lengths of v(i,m). The attenuation gain between iciosest(m) and some other HOA source i for informed source m is obtained with: m) ||v(i,m)|| In addition, beamforming weights w(icjosest(m),m) that focus a beam pattern from the closest HOA / FOA source towards the informed source m are calculated: w(tdosesf(m),m) = —-------—— ^closestCm) + 1) where Y(icjosest(m), m) is the set of real spherical harmonic functions for the pair (idosest(m),m) for all the orders n e [0, nfc;osest(m)] and degrees k e [~n,n]. Real spherical harmonics defined as: I (n-lklV. [V2Sin(|m if k <0 Y^(0,a) = j(2n+l) ——Pf (cos a) * <1, if k ==0 ’ IV2 cos(|k|0), if k >0 for each HOA source i and informed source m pairs, the outer product of Y(i,m) and Y(i,m)T is also calculated up to order 1: yy(t, m) = Y(i, m)Y(i, m)T, for n <1 Furthermore in addition to the operations of the position pre-processor described above, when informed sources are present, the active informed sources are determined. An Informed source is active when the certain conditions hold: 1. The listener is closer than a set threshold (IpdlnformedSourceEnableThreshold in the bitstream) to an informed source 2. The closest HOA source to an informed source is closer than a set threshold (hpdlnformedSourceEnableThreshold in the bitstream) In the spatial analyzer as described previously, it was mentioned that spatial analysis is performed for HOA / FOA sources that belong to the triangle that the listener is in. In addition, spatial analysis is also performed for HOA / FOA sources which are the closest sources to active informed sources. In some embodiments, for each informed source, a signal is obtained via beamforming. The beamformed signals are post-filtered and time-aligned at the HOA source positions and at the listener position. For each active informed source for the current frame, beamforming is performed as follows: Ssrc(j,k,b,m) = w(iciosest(m\m}S^^^ The obtained signal is post-filtered: SSrcQ’ k, b, m) = Gpost(j, k, b, m)Ssrc(j, k, b, m) where a cross-pattern coherence (CroPaC) based post-filter is used. Time-alignment at HOA source positions is implemented as follows: Ssrc(j,k,b,i,m) = Ssrc(t(j,i,Tri),k,b,m) where t(j,i,m) =j - min (dhop(i, iciosest(m),m), d'hop,max') Time-alignment at listener position: §l.src(j> k’ b> m) = Ssrc(t(j> h,closest ™)> k, b, m) The spatial metadata parameters which have contribution from the informed sources can then be determined for the active HOA / FOA sources. The signal covariance matrix from the time-aligned beamformed signals Ssrc(j, k, b, i, m) for the active HOA / FOA sources is determined: CSrc (j' b,i) = gatt (i, m)2 * Esrc (j, b, i, m) *yy(i, m) 771 ^-active The signal covariance matrix from the listener towards a source is obtained as follows: / 9i,att(j’ iciosest^m^i'n) * Ei,src(j, b,in) I* HRTF(y,„t(j, m), b) . HRTF(ytrot(j, m). b)“ where HRTF(ylrot(j,m),b) is the HRTF from the listener towards the informed source m and giiatt(j>hiosest(.m)>m) is an attenuation gain and Et src(J,b,m) is the energy of the time-aligned signal §isrc(j, b,m). Now, Ci is the signal covariance matrix at the listener position with contribution only from the informed sources. For the output the contribution for all other sources present in the scene are needed. Note that the signal covariance matrix Cy as calculated previously has the contribution from all sources in the scene (informed and non-informed). This was calculated based on interpolated spatial metadata at the listener position. Thus, it would be beneficial to be able to calculate interpolated spatial metadata at the listener position without the contribution of the informed sources. This is implemented as follows: First, calculate intensity vectors and energy at the HOA / FOA sources from the signal covariance matrices Csrc(j,b,i) (informed source contribution at the HOA / FOA sources): '(^(j, b, / ,1,4)1 VcO) k, b, i) = Csrc(j, b, i, 1,2) / (V3 * %) Csrc(j, b, i, 1,3)] Esrc(j,k,b,i) = 2jh=i CSrc(J> ^) 4 * NSf Similarly, intensity in0A(j> k, b,i) and energy EH0A(j, k, b, i) are calculated for the HOA / FOA signals. These contain the contribution from all sources in the scene. Next, obtain intensity and energy which has only the contribution from non-informed sources by subtraction: iresO) k,b,i) = iHOA(j,k, b, i) - isrc(j, k, b,i) Eres(j, k, b, i) = EHOA(j, k, b, i) - Esrc(j, k, b, i) From these, spatial metadata at HOA / FOA source positions is obtained that have contribution only from the non-informed sources: Azimuth: 0res(j, k, b, i) = atan2(ires(j, k, b, i, 2), ires(j, k, b, i, 1)) Elevation: <pres(j> k, b, i) = atan2 QresQ', k, b, i, 3), jires(j,k,b,i,I)2 + ires(j,k,b,i,2)2^ Direct-to-total energy ratio: rres(j,k,b,i) = \l ires(j >k> b, I, 1) + ifesQ, k, b, i, 2) + ^res^J’ k, b, i, 3) EresCj, k, b, l) These are then interpolated in the same manner as in the metadata interpolation block described previously resulting in EreSilntrp(j,k,b), A signal covariance matrix is calculated from the interpolated metadata in the same manner as Cy was calculated previously. This provides a signal covariance matrix Cres with contribution from only the non-informed sources. The final target covariance matrix is then obtained as follows: €^) = 6^) + 6^(]^) Note that when performing exterior rendering (listener outside the microphone area), the metadata adjustments are implemented on the residual metadata. Furthermore, if there are exterior informed sources, the exterior projection radius is modified dynamically to be equal to the distance from the 5 closest active exterior informed source to the listener from the microphone area. In some embodiments the exterior Projection Radius is set in the scene description In these embodiments, the exterior projection radius control indication or information can be inserted into the scene description either by the content creator 10 (based on listening, knowledge of the scene) or automatically by the encoder based on, for example positions of exterior informed sources. The information can in some embodiments be carried in the bitstream as a float value as shown below, as underlined. Syntax No.of bits Mnemonic hoaGroups() { hoaGroupsCount = GetCountOrlndex(); for (int i = 0; i <hoaGroupsCount; i++) { hoaGroupId = GetlD(); hoaGroupHasRegion; 1 bslbf if (hoaGroupHasRegion) { hoaGroupRegionld = GetlD(); J coSourceCount = GetCountOrlndex(); for (int j = 0; j <coSourceCount; j++) { coSourceld = GetlD(); } FreqBandConfig(); exteriorRenderinqProjectionRadius; 32 float hoaGroupHasInformedSources; 1 bslbf if (hoaGroupHasInformedSources == True) { informedSourceCount; 16 uimsbf maxSimulInformedSources; 8 uimsbf for (j = 0; j <informedSourceCount; j++) { InformedSourcelnfoStructO } } } When setting the radius (automatically) in the encoder, the encoder can be configured to use information about the positions of any exterior informed sources. For example, the exterior projection radius may be set to the average or maximum distance of the exterior informed sources from the HOA source area. This in some embodiments can be implemented in the encoder by following the summary of operations: 1. Perform Delaunay triangulation of the HOA source space 2. Find outside edges and HOA sources of the HOA source space 3. Determine the presence of any exterior informed sources and calculate their distance to the closest edge or closest HOA source to them (whichever is closest) 4. Use the maximum of the distances of the informed sources as the exterior projection radius (or the average of the distances) With respect to Figure 8 is shown a flow diagram showing an example operation of the encoder according to some embodiments, where the content creator function or user is configured to set the exterior projection radius and signal it to the decoder or renderer. For example firstly the scene data is obtained as shown in Figure 8 by 801. Then a exterior rendering projection radius is determined by a suitable input, for example from a user as shown in Figure 8 by 803. A determination or check that it is likely to result in a sufficient quality output (at the renderer) is then performed as shown in Figure 8 by 805. When it is determined that the quality output is not likely to be achieved than the method can loop back to determining a ‘new’ exterior rendering projection radius (in other words passing back to 803). When it is determined that the quality is likely to be acceptable then the scene is encoded based on the scene data and the determined exterior rendering projection value as shown in Figure 8 by 807. With respect to Figure 9 is shown a further embodiment where the radius is determined automatically (or in other words without significant content creator user input). Firstly the scene data is obtained as shown in Figure 9 by 901. Then a triangulation of HOA source positions is performed as shown in Figure 9 by 903. Then a check is made to determine whether there are any informed sources outside of the area defined by the triangulation of the HOA source positions as shown in Figure 9 by 905. Where there are no outside informed sources present then the scene is encoded based on the scene data as shown in Figure 9 by 907. Where there is at least one outside informed source present then there is a detemination of the distance from the outside informed source to the edge of the triangulated HOA source area as shown in Figure 9 by 909. Furthermore there is a calculation of the exterior rendering projection radius based on an average of the determined outside informed source distances as shown in Figure 9 by 911. Then the scene is encoded based on the scene data and the determined exterior rendering projection value as shown in Figure 9 by 913. With respect to Figure 10 is furthermore shown an example operation of the decoder or renderer according to some embodiments. The first operation is one of obtaining or otherwise receiving the bitstream as shown in Figure 10 by 1001. Then the bitstream (comprising the scene data) is decoded and the exterior rendering projection radius is obtained as shown in Figure 10 by 1003. Then a triangulation of HOA source space is performed as shown in Figure 10 by 1005. Furthermore the user position is obtained as shown in Figure 10 by 1007. The renderer is then caused to calculate or determine spatial metadata at the listener position as shown in Figure 10 by 1009. Then a check is made to determine whether the user is inside HOA source space as shown in Figure 10 by 1011. Where the user is within the HOA source space then the audio is rendered according to the spatial metadata at the listener position as shown in Figure 10 by 1013. Where the user is outside the HOA source space then the metadata is adjusted based on the signalled exterior rendering projection radius (and using the methods described previously) as shown in Figure 10 by 1015. After adjustment of the spatial metadata when the audio is rendered according to the adjusted spatial metadata at the listener position as shown in Figure 10 by 1017. In some embodiments the encoder processing is implemented at the renderer once the scene description is received. An flow diagram of an example operation of a renderer implementing these embodiments is shown in Figure 11. The first operation is one of obtaining or otherwise receiving the bitstream as shown in Figure 11 by 1101. The bitstream (comprising the scene data) is decoded and the scene data obtained as shown in Figure 11 by 1103. Then a triangulation of HOA source space is performed as shown in Figure 11 by 1105. Furthermore the user position is obtained as shown in Figure 11 by 1107. The renderer is then caused to calculate or determine spatial metadata at the listener position as shown in Figure 11 by 1109. Then a check is made to determine whether the user is inside HOA source space as shown in Figure 11 by 1111. Where the user is within the HOA source space then the audio is rendered according to the spatial metadata at the listener position as shown in Figure 11 by 1113. Where the user is outside the HOA source space then a check is made to determine whether there are any informed sources outside of the area defined by the triangulation of the HOA source space as shown in Figure 11 by 1115. Where there are no outside informed sources present then a default value for exterior rendering projection radius is selected as shown in Figure 11 by 1121. Where there is at least one outside informed source present then there is a detemination of the distance from the outside informed source to the edge of the triangulated HOA source area as shown in Figure 11 by 1117. Furthermore there is a calculation of the exterior rendering projection radius based on an average of the determined outside informed source distances as shown in Figure 11 by 1119. Then using either the determined or default exterior rendering projection radius as selected or determined above, the metadata is adjusted (and using the methods described previously) as shown in Figure 11 by 1123. After adjustment of the spatial metadata when the audio is rendered according to the adjusted spatial metadata at the listener position as shown in Figure 11 by 1125. A current implementation of the MPEG-I Immersive audio renderer is configured to always adjust the projection radius based on which of them are active (close to listener) and their distance to the HOA source area. Of the active exterior informed sources, the renderer chooses the one that is closest to the HOA source area and uses that distance as the exterior projection radius. As mentioned above, this can cause abrupt changes in the rendering as the list of active exterior informed sources changes as the listener moves. If there are no outside informed sources in the scene (active or non-active), the exterior projection radius is set as a default one (for example 4.0 meters). If there are non-active exterior informed sources, the average distance from the HOA source area to all of the outside sources is used as the projection radius. In some embodiments in order to improve on such implementations the adaptive exterior projection radius is configured to adapt in a non-abrupt manner so that abrupt changes in audio are not heard. An example of which is shown in Figures 5a to 5d. For example Figure 5a shows the scene as shown previously, with informed sources 501, 503, 505, 509 external to the HOA source area. Addionally is shown an outside edge perimeter 560 which is located 1.0 m from the HOA source area. This perimeter 560 can comprise straight edges, for example between 532 and 535, 537 and 536, 534 and 533, and 531 and 530. The perimeter further can comprise curves with radius of 1,0m centred at the corners of the HOA source area, for example a curve between 530 and 532 centred at 109, a curve between 535 and 537 centred at 107, a curve between 536 and 534 centred at 103, and a curve between 533 and 531 centred at 101. The renderer can then in some embodiments perform the following: 1. Find set of exterior informed sources: If there are no informed sources external to the HOA source area then employ a constant value for exterior projection radius (for example using the above methods such as described in Figures 8 to 10); If there is only one exterior informed source use the distance from the exterior informed source to the edge of the HOA source area as the exterior projection radius. Alternatively, in the case where there is a single exterior informed source the exterior projection radius can, in some embodiments, be set to be the distance from the projected listener position to the informed or target source. The projected listener position can be defined as the listener position projected to a closest position on the exterior edge as defined by the HOA source(s). In other words the projected listener position is located either on a position on an exterior edge or at the position of an exterior HOA source. 2. For each exterior informed source find the closest exterior edge or exterior HOA source (whichever is closest). The term exterior HOA source refers to a HOA source that is from the exterior edge in case of an audio scene with multiple HOA sources, or a HOA source in an audio scene with a single HOA source. This can be implemented using the same method as above when calculating the closest HOA source or edge to the listener position. Examples of exterior HOA sources, that are HOA source on the edge of the HOA area are for example rm 101, m2 103, m4 107 and ms 109 in Figure 1 a for example. 3. Project the exterior informed source to a set distance (1,0m) from the closest exterior edge or HOA source 4. Find the closest exterior edge or exterior HOA source (whichever is closest) to the listener. An exterior edge is an edge connecting the closet exterior HOA sources. For example the edge connecting rm 101 and m2 103 as mentioned above as shown in Figure 1a. 5. Project the listener (511) to a set distance (1.0m) from the closest exterior edge or HOA source. Line (shown by 512), find the distance between the projected listener position and two adjacent (to the projected listener position) projected informed source positions (508, 510). a) If the listener is projected to an exterior edge, the adjacent projected informed sources are obtained based on sorting the informed sources projected to the projection line and the projected listener position by the x-coordinate value (y coordinate, if the projection line is vertical). b) If the listener is projected to an HOA source, adjacent informed sources are determined based on the angles of the informed source positions and listener position with respect to HOA source position. c) The search for adjacent informed source may extend over several edges and HOA sources. d) Distances between projected adjacent informed source positions are calculated along the projection line. For positions projected to an edge, the distance calculation is a simple Euclidian distance. For positions projected to the arc around a source, distance is calculated along the arc. 6. Calculate a weighted average of the distances 520, 522 of the adjacent exterior informed sources 507, 509 projections 508, 510 to the HOA source area (with the weights calculated based on the distances calculated here). The weighting could be applied for source A as wA = 1 - D(L,A) / (D(L,A) + D(L,B)), where D(L,A) is the distance from the projected listener position to the projected position of the informed source A. D(L,B) is the same for informed source B. A and B are the adjacent informed sources for the listener. Other implementations for generating a weighting can be implemented in some other embodiments. The projection radius in embodiments where there are informed sources that are exterior to the HOA source region or capture area (for example where there is an audio scene with multiple HOA sources) or informed sources as part of an audio scene with a single HOA source, the projection radius can be calculated as a mean, median, mode or any suitable parameter derived from the distance of the informed sources from one of the following: • the exterior edge • exterior HOA source • a HOA source in an audio scene with single HOA source. In some further embodiments, the projection radius in an audio scene with single or multiple HOA source(s) with multiple informed or target sources is derived based on the priority of the informed or target sources in the audio scene. 7. Use the weighted average distance as the exterior projection radius. A further example can be shown in Figure 5b, where the sources 551 and 553 are projected to the curve surface at positions 552 and 554 and projected such that the projections are the intersection of the curve and the line between the external informed source and HOA source. Also is shown the projection between a further source 563 to the surface at position 564. Further is shown the listener position 561 also projected to the surface at position 562. Figure 5c shows the determination of the weightings based on the distance 573 from the listener projection 562 and informed source projection 564 and distance 571 from the listener projection 562 and informed source projection 554. Figures 6a and 6b further show projections to a exterior edge defined by a pair of sources and a single source. In other words the above shows that within a scene there can be shown a capture area defined by the capture sources (the HOA sources or microphones or content created sources), and that the listening position can be external to the capture area but within the scene. Furthermore there can be sources or target sources of audio energy (which can be determined from the capture area sources) which can be external to the capture area. The exterior projection radius furthermore can be a rendering parameter for the assisting of the rendering of an audio signal when the listener position is external to the capture area. For example it can be used to map the audio source as a target audio source to a position which is the distance perpendicular from either a capture area boundary edge defined by two capture area sources or from a capture area source. When setting the exterior projection radius in this manner, there are no jumps in the exterior projection radius as the listener moves. Whenever the projected listener and projected informed source position are the same the exterior projection radius is exactly the distance from informed source position to the edge of the HOA source area. The above adaptive exterior projection radius calculation may be controlled or set in the scene description by the content creator. For example a new field (underlined below) adaptiveExteriorRenderingProjectionRadius can be added to the hoaGroups() definition. Setting this to 1 causes the adaptive exterior projection to be used. If the value is set to 0, the exteriorRenderingProjectionRadius value is used as default. Syntax No. of bits Mnemonic hoaGroups() { hoaGroupsCount = GetCountOrlndex(); for (int i = 0; i <hoaGroupsCount; i++) { hoaGroupId = GetlD(); hoaGroupHasRegion; 1 bslbf if (hoaGroupHasRegion) { hoaGroupRegionld = GetlD(); } coSourceCount = GetCountOrlndex(); for (int j = 0; j <coSourceCount; j++) { coSourceld = GetlD(); } FreqBandConfig(); exteriorRenderingProjectionRadius; 32 float hoaGroupHasInformedSources; 1 bslbf if (hoaGroupHasInformedSources == True) { informedSourceCount; 16 uimsbf maxSimulInformedSources; 8 uimsbf for (j = 0; j <informedSourceCount; j++){ lnformedSourcelnfoStruct() } adaptiveExteriorRenderinqProjection Radius; 1 bslbf } } An example system employing some emodiments is described in Figure 7. The figure illustrates an end to end system overview for an audio scene comprising 5 multiple HOA sources, which is rendered according to the above examples. The renderer receives the scene description and audio bitstreams and performs rendering accordingly. The system can comprise a content creator 701 which can be implemented on any suitable computer or processing device. The content creator 701 comprises an (MPEG-I Immersive audio) encoder 703 which is configured to receive the audio scene description 700 and the audio signals or data 702. The audio scene description 700 can be provided in the MPEG-I Immersive audio Encoder Input Format (EIF) or in other suitable format. Generally, the audio scene description contains an acoustically relevant description of the contents of the audio scene, and contains, for example, the scene geometry as a mesh or voxel, acoustic materials, acoustic environments with reverberation parameters, positions of sound sources, and other audio element related parameters such as whether reverberation is to be rendered for an audio element or not. The MPEG-I Immersive audio encoder 703 is configured to output encoded data 704. The content creator 701 furthermore in some embodiments comprises a MPEG-H encoder 705 and generates MPEG-H audio bitstream. The MPEG-H audio bitstream 706 and 6DoF audio bitstream 704 in some embodiments can be streamed to end-user devices or made available for download or stored. Additionally the system comprises a server 711 configured to obtain the bitstreams, and store them (in bitstream storage 713) and supply them (for example as a six degrees of freedom (6-DoF) audio bitstream 712) to the player 721. The relevant bitstream 712 is retrieved by the player 721. In some embodiments other implementation options are feasible such as broadcast, multicast. The player 721 in some embodiments comprises a playback device 723 configured to obtain or receive the 6DoF audio bitstream 712, and furthermore can be configured to receive or otherwise obtain the 6 DoF tracking information (listener orientation or position information) 726 from a suitable listener user interface, for example from the head mounted device (HMD) 729. These can for example be generated by sensors within the HMD 729 or from sensors in the environment sensing the orientation or position of the listener. In some embodiments the playback device 723 comprises a bitstream parser 725 configured to obtain the encoded bitstream 712 and decode these in an opposite or inverse operation to the encoders 703, 705 to generate audio and metadata 724 which can be passed to a MPEG-I Immersive audio renderer 727. In some embodiments the playback device 723 comprises the MPEG-I Immersive audio renderer 727 configured to implement the rendering operations as described above and generate audio output signals 728 which can be output to the head mounted device 729. The playback device 723 can be implemented in different form factors depending on the application. In some embodiments the playback device is equipped with its own listener position tracking apparatus or receives the listener position information from an external apparatus. The playback device can in some embodiments be also equipped with headphone connector to deliver output of the rendered binaural audio to the headphones. With respect to Figure 12 an example electronic device which may be used as the computer, encoder processor, decoder processor or any of the functional blocks described herein is shown. The device may be any suitable electronics device or apparatus. For example in some embodiments the device 1600 is a mobile device, user equipment, tablet computer, computer, audio playback apparatus, etc. In some embodiments the device 1600 comprises at least one processor or central processing unit 1607. The processor 1607 can be configured to execute various program codes such as the methods such as described herein. In some embodiments the device 1600 comprises a memory 1611. In some embodiments the at least one processor 1607 is coupled to the memory 1611. The memory 1611 can be any suitable storage means. In some embodiments the memory 1611 comprises a program code section for storing program codes implementable upon the processor 1607. Furthermore in some embodiments the memory 1611 can further comprise a stored data section for storing data, for example data that has been processed or to be processed in accordance with the embodiments as described herein. The implemented program code stored within the program code section and the data stored within the stored data section can be retrieved by the processor 1607 whenever needed via the memory-processor coupling. In some embodiments the device 1600 comprises a user interface 1605. The user interface 1605 can be coupled in some embodiments to the processor 1607. In some embodiments the processor 1607 can control the operation of the user interface 1605 and receive inputs from the user interface 1605. In some embodiments the user interface 1605 can enable a user to input commands to the device 1600, for example via a keypad. In some embodiments the user interface 1605 can enable the user to obtain information from the device 1600. For example the user interface 1605 may comprise a display configured to display information from the device 1600 to the user. The user interface 1605 can in some embodiments comprise a touch screen or touch interface capable of both enabling information to be entered to the device 1600 and further displaying information to the user of the device 1600. In some embodiments the device 1600 comprises an input / output port 1609. The input / output port 1609 in some embodiments comprises a transceiver. The transceiver in such embodiments can be coupled to the processor 1607 and configured to enable a communication with other apparatus or electronic devices, for example via a wireless communications network. The transceiver or any suitable transceiver or transmitter and / or receiver means can in some embodiments be configured to communicate with other electronic devices or apparatus via a wire or wired coupling. The transceiver can communicate with further apparatus by any suitable known communications protocol. For example in some embodiments the transceiver can use a suitable universal mobile telecommunications system (UMTS) protocol, a wireless local area network (WLAN) protocol such as for example IEEE 802.X, a suitable short-range radio frequency communication protocol such as Bluetooth, or infrared data communication pathway (IRDA). The transceiver input / output port 1609 may be configured to transmit / receive the audio signals, the bitstream and in some embodiments perform the operations and methods as described above by using the processor 1607 executing suitable code. In general, the various embodiments of the invention may be implemented in hardware or special purpose circuits, software, logic or any combination thereof. For example, some aspects may be implemented in hardware, while other aspects may be implemented in firmware or software which may be executed by a controller, microprocessor or other computing device, although the invention is not limited thereto. While various aspects of the invention may be illustrated and described as block diagrams, flow charts, or using some other pictorial representation, it is well understood that these blocks, apparatus, systems, techniques or methods described herein may be implemented in, as non-limiting examples, hardware, software, firmware, special purpose circuits or logic, general purpose hardware or controller or other computing devices, or some combination thereof. The embodiments of this invention may be implemented by computer software executable by a data processor of the mobile device, such as in the processor entity, or by hardware, or by a combination of software and hardware. Further in this regard it should be noted that any blocks of the logic flow as in the Figures may represent program steps, or interconnected logic circuits, blocks and functions, or a combination of program steps and logic circuits, blocks and functions. The software may be stored on such physical media as memory chips, or memory blocks implemented within the processor, magnetic media, and optical media. The memory may be of any type suitable to the local technical environment and may be implemented using any suitable data storage technology, such as semiconductor-based memory devices, magnetic memory devices and systems, optical memory devices and systems, fixed memory and removable memory. The data processors may be of any type suitable to the local technical environment, and may include one or more of general purpose computers, special purpose computers, microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASIC), gate level circuits and processors based on multi-core processor architecture, as non-limiting examples. Embodiments of the inventions may be practiced in various components such as integrated circuit modules. The design of integrated circuits is by and large a highly automated process. Complex and powerful software tools are available for converting a logic level design into a semiconductor circuit design ready to be etched and formed on a semiconductor substrate. Programs, such as those provided by Synopsys, Inc. of Mountain View, California and Cadence Design, of San Jose, California automatically route conductors and locate components on a semiconductor chip using well established rules of design as well as libraries of pre-stored design modules. Once the design for a semiconductor circuit has been completed, the resultant design, in a standardized electronic format (e.g., Opus, GDSII, or the like) may be transmitted to a semiconductor fabrication facility or "fab" for fabrication. The foregoing description has provided by way of exemplary and non-5 limiting examples a full and informative description of the exemplary embodiment of this invention. However, various modifications and adaptations may become apparent to those skilled in the relevant arts in view of the foregoing description, when read in conjunction with the accompanying drawings and the appended claims. However, all such and similar modifications of the teachings of this 10 invention will still fall within the scope of this invention as defined in the appended claims.

Claims

1. A method for assisting six degrees-of-freedom rendering of an audio scene when a listener position is external to a capture area, the method comprising: obtaining information associated with an audio source;determining a position of the audio source relative to the capture area;when the position of the audio source is external to the capture area, obtaining a parameter;defining a rendering parameter for assisting the rendering of an audio signal when the listener position is external to the capture area; andencoding at least the rendering parameter based on the provided parameter.

2. The method as claimed in claim 1, wherein the capture area is defined relative to:at least one microphone position or at least one higher order ambisonics position; anda perimeter defined by at least two microphones positions or at least two higher order Ambisonics positions.

3. The method as claimed in any of claims 1 or 2, wherein the rendering parameter for assisting the rendering of an audio signal comprises an exterior rendering projection radius value, for mapping the audio source as a target audio source when the listener position is external to the capture area.

4. The method as claimed in claim 3, wherein the rendering parameter for assisting the rendering of an audio signal further comprises an indicator that the exterior rendering projection radius value is an adaptive value.

5. The method as claimed in any of claims 3 or 4 when dependent on claim 2, wherein the exterior rendering projection radius value defines a distance for assisting a mapping of the audio source position to a distance perpendicular fromeither the at least one microphone position or at least one higher order ambisonics position or the perimeter.

6. The method as claimed in any of claims 3 to 5, wherein defining a rendering parameter for assisting the rendering of an audio signal when the listener position is external to the capture area when the rendering parameter is the exterior rendering projection radius value comprises:determining the exterior renering projection radius value based on an input;determining a quality check on the determined exterior rendering projection radius value; andproviding the exterior renering projection radius value based on an input as the exterior rendering projection value when the quality check is passed or modifying the exterior renering projection radius value otherwise.

7. The method as claimed in any of claims 1 to 6, further comprising: obtaining audio data associated with the at least one audio source; and encoding the audio data to generate an audio data bitstream.

8. The method as claimed in claim 7, wherein obtaining audio data associated with the at least one audio source comprises obtaining at least three audio signals from:at least three microphones; orat least three higher order Ambisonics, whereinthe at least three microphones or at least three higher order ambisonics audio signals are associated with positions within the audio scene.

9. The method as claimed in claim 8, wherein determining the position of the audio source relative to the capture area comprises a determining the position of the audio source based on the at least three audio signals and positions associated with the at least three microphones or the at least three higher order Ambisonics.

10. The method as claimed in claim 9 further comprising determining the position of the audio source is external by:triangulating positions within the audio scene of the at least three microphones or the at least three higher order ambisonics;identifying the position of the audio source within the audio scene is exterior to the triangulation of the positions within the audio scene of the at least three microphones or the at least three higher order ambisonics.

11. The method as claimed in claim 10, when depenent on claim 3, further comprising determining the exterior rendering projection radius value from a distance between the position of the audio source within the audio scene and a line between two closest positions of the at least three microphones or the at least three higher order ambisonics.

12. The method as claimed in any of claims 1 to 11, wherein the information associated with the audio source further comprises a position of the audio source within the audio scene.

13. The method as claimed in any of claims 1 to 12, further comprising receiving a listener position, wherein the information indicating the audio source is a target audio source within the audio scene is based on the distance between an audio source position and the listener position.

14. A method for six degrees-of-freedom rendering of an audio scene when a listener position is external to a capture area, the method comprising:obtaining information associated with an audio souce;obtaining a rendering parameter for assisting the rendering of an audio signal when the listener position is external to the capture area;obtaining the listener position, the listener position being external to the capture area and within the audio scene;mapping a position of the audio source to a mapped position around the listener position based on the rendering parameter;generating at least one audio output based on the mapped position within the audio scene to achieve a localized rendering with respect ot the listener position.

15. The method as claimed in claim 14, further comprising obtaining an indicator identifying the audio source is a target audio source within the audio scene.

16. The method as claimed in claim 14, further comprising determining the audio souce is a target audio source based on the position of the audio source and the listerner position.

17. The method as claimed in any of claims 14 to 16, wherein the capture area is defined relative to:at least one microphone position or at least one higher order ambisonics position; anda perimeter defined by at least two microphones positions or at least two higher order Ambisonics positions.

18. The method as claimed in any of claims 14 to 17, wherein the rendering parameter for assisting the rendering of an audio signal comprises an exterior rendering projection radius value for the mapping of the audio source when the listener position is external to the capture area.

19. The method as claimed as claim 18, wherien the rendering parameter for assisting the rendering of an audio signal further comprises an indicator that the exterior rendering projection radius value is an adaptive value, wherein mapping the audio source comprises adaptively mapping the audio source when the indicator indicates that the exterior rendering projection radius value is an adaptive value.

20. The method as claimed in any of claims 18 or 19, wherein the exterior rendering projection radius value defines a distance for assisting the mapping of the audio source position to the distance perpendicular from the capture area.

21. The method as claimed in claim 20, further comprising determining spatial metadata based on the exterior rendering projection radius value, whereingenerating at least one audio output is further based on determined spatial metadata.

22. The method as claimed in any of claim 14 to 21, further comprising obtaining an audio data bitstream comprising audio data from at least one position within the audio scene associated with the at least one audio source, wherein generating the at least one audio output is further based on the audio data bitstream.

23. The method as claimed in claim 17, wherein the audio data comprises at least three audio signals from:at least three microphones; orat least three higher order Ambisonics, wherein the at least three microphones or at least three higher order ambisonics audio signals are associated with positions within the audio scene.

24. The method as claimed in claim 23, wherein wherein the position of the audio source is obtained based on the positions of the at least three audio signals.

25. The method as claimed in claim 24, wherein defining a rendering parameter for assisting the rendering of an audio signal when the listener position is external to the capture area when the rendering parameter is the exterior rendering projection radius value comprises:triangulating positions within the audio scene of the at least three microphones or the at least three higher order ambisonics;identifying the position of the audio source within the audio scene is exterior to the triangulation of the positions within the audio scene of the at least three microphones or the at least three higher order ambisonics;determining the exterior rendering projection radius value from a distance between the position of the audio source within the audio scene and a line between two closest positions of the at least three microphones or the at least three higher order ambisonics.

26. The method as claimed in claim 23 or any claim dependent on claim 23, further comprising determining spatial metadata based on the rendering parameter.

27. The method as claimed in claim 26, wherein determining spatial metadata based on the rendering parameter comprises:determining a spatial metadata parameter based on the listener position and the audio data bitstream; andapplying an adjustment to the determined metadata based on the rendering parameter where the listener position is exterior to a triangulation of audio data bitstream sources.

28. The method as claimed in any of claims 14 to 27, wherein the information associated with the audio source further comprises a position of the audio source within the audio scene.

29. An apparatus for assisting six degrees-of-freedom rendering of an audio scene when a listener position is external to a capture area, the apparatus comprising means configured to:obtain information associated with an audio source;determine a position of the audio source relative to the capture area;when the position of the audio source is external to the capture area, obtain a parameter;define a rendering parameter for assisting the rendering of an audio signal when the listener position is external to the capture area; andencode at least the rendering parameter based on the provided parameter.

30. An apparatus for six degrees-of-freedom rendering of an audio scene when a listener position is external to a capture area, the apparatus comprising means configured to:obtain information associated with an audio souce;obtain a rendering parameter for assisting the rendering of an audio signal when the listener position is external to the capture area;obtain the listener position, the listener position being external to the capture area and within the audio scene;map a position of the audio source to a mapped position around the listener position based on the rendering parameter; and5 generate at least one audio output based on the mapped position within theaudio scene to achieve a localized rendering with respect ot the listener position.

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