Patent Publication Number: US-11395087-B2

Title: Level-based audio-object interactions

Description:
BACKGROUND 
     Technical Field 
     The exemplary and non-limiting embodiments relate generally to rendering of free-viewpoint audio for presentation to a user using a spatial rendering engine. 
     Brief Description of Prior Developments 
     Free-viewpoint audio generally allows for a user to move around in the audio (or generally, audio-visual or mediated reality) space and experience the audio space in a manner that correctly corresponds to his location and orientation in it. This may enable various virtual reality (VR) and augmented reality (AR) use cases. The spatial audio may consist, for example, of a channel-based bed and audio-objects, audio-objects only, or any equivalent spatial audio representation. While moving in the space, the user may come into contact with audio-objects, the user may distance themselves considerably from other objects, and new objects may also appear. The listening/rendering point may thereby adapt to the user&#39;s movement, and the user may interact with the audio-objects, and/or the audio content may otherwise evolve due to the changes relative to the rendering point or user action. 
     SUMMARY 
     The following summary is merely intended to be exemplary. The summary is not intended to limit the scope of the claims. 
     In accordance with one aspect, an example method comprises, obtaining a listening position in an audio space; obtaining audio and metadata corresponding to a rendering at the listening position; obtaining a listening environment and determining an effect of the listening environment on the rendering at the listening position; detecting audio interaction at the listening position by comparing an audio rendering level against a corresponding level threshold metadata; applying, by a processing device, an audio modification according to the audio interaction detection; and rendering audio at the listening position based on the applied audio modification. 
     In accordance with another aspect, an example apparatus comprises at least one processor; and at least one non-transitory memory including computer program code, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus to: obtain a listening position in an audio space; obtain audio and metadata corresponding to a rendering at the listening position; obtain a listening environment and determine an effect of the listening environment on the rendering at the listening position; detect audio interaction at the listening position by comparing an audio rendering level against a corresponding level threshold metadata; apply an audio modification according to the audio interaction detection; and render audio at the listening position based on the applied audio modification. 
     In accordance with another aspect, an example apparatus comprises a non-transitory program storage device readable by a machine, tangibly embodying a program of instructions executable by the machine for performing operations, the operations comprising: obtaining a listening position associated with a user; obtaining audio and metadata corresponding to a rendering at the listening position; obtaining a listening environment and determining an effect of the listening environment on the rendering at the listening position; detecting audio interaction at the listening position by comparing an audio rendering level against a corresponding level threshold metadata; applying an audio modification according to the audio interaction detection; and rendering audio at the listening position based on the applied audio modification. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing aspects and other features are explained in the following description, taken in connection with the accompanying drawings, wherein: 
         FIG. 1  is a diagram illustrating a reality system comprising features of an example embodiment; 
         FIG. 2  is a diagram illustrating some components of the system shown in  FIG. 1 ; 
         FIGS. 3 a  and 3 b    are diagrams illustrating characteristics of free-viewpoint content consumption; 
         FIGS. 4 a  and 4 b    are diagrams illustrating a VR user listening to the same audio source in an open space ( FIG. 4 a   ) and a space with strong reflections ( FIG. 4 b   ); 
         FIG. 5  is an example high-level block diagram of interaction detection and audio-object modification; 
         FIG. 6  is an example block diagram illustrating a level based audio object rendering system; 
         FIG. 7  is an example high-level block diagram of interaction detection and audio-object modification implementing Level-based audio-object interactions; and 
         FIG. 8  shows a method in accordance with example embodiments which may be performed by an apparatus. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Referring to  FIG. 1 , a diagram is shown illustrating a reality system  100  incorporating features of an example embodiment. The reality system  100  may be used by a user for augmented-reality (AR), virtual-reality (VR), or presence-captured (PC) experiences and content consumption, for example, which incorporate free-viewpoint audio. Although the features will be described with reference to the example embodiments shown in the drawings, it should be understood that features can be embodied in many alternate forms of embodiments. 
     The system  100  generally comprises a visual system  110 , an audio system  120 , a relative location system  130  and a level based audio object rendering system  140 . The visual system  110  is configured to provide visual images to a user. For example, the visual system  12  may comprise a virtual reality (VR) headset, goggles or glasses. The audio system  120  is configured to provide audio sound to the user, such as by one or more speakers, a VR headset, or ear buds for example. The relative location system  130  is configured to sense a location of the user, such as the user&#39;s head for example, and determine the location of the user in the realm of the reality content consumption space. The movement in the reality content consumption space may be based on actual user movement, user-controlled movement, and/or some other externally-controlled movement or pre-determined movement, or any combination of these. The user is able to move and turn their head in the content consumption space of the free-viewpoint. The relative location system  130  may be able to change what the user sees and hears based upon the user&#39;s movement in the real-world; that real-world movement changing what the user sees and hears in the free-viewpoint rendering. 
     The movement of the user, interaction with audio-objects and things seen and heard by the user may be defined by predetermined parameters including an effective distance parameter and a reversibility parameter. An effective distance parameter may be a core parameter that defines the distance from which user interaction is considered for the current audio-object. In some embodiments, the effective distance parameter may also be considered a modification adjustment parameter, which may be applied to modification of interactions, as described in U.S. patent application Ser. No. 15/293,607, filed Oct. 14, 2016, which is hereby incorporated by reference. A reversibility parameter may also be considered a core parameter, and may define the reversibility of the interaction response. The reversibility parameter may also be considered a modification adjustment parameter. Although particular modes of audio-object interaction are described herein for ease of explanation, brevity and simplicity, it should be understood that the methods described herein may be applied to other types of audio-object interactions. 
     The user may be virtually located in the free-viewpoint content space, or in other words, receive a rendering corresponding to a location in the free-viewpoint rendering. Audio-objects may be rendered to the user at this user location. The area around a selected listening point may be defined based on user input, based on use case or content specific settings, and/or based on particular implementations of the audio rendering. Additionally, the area may in some embodiments be defined at least partly based on an indirect user or system setting such as the overall output level of the system (for example, some sounds may not be audible when the sound pressure level at the output is reduced). In such instances the output level input to an application may result in particular sounds being not rendered because the sound level associated with these audio-objects may be considered imperceptible from the listening point. In other instances, distant sounds with higher output levels (such as, for example, an explosion or similar loud event) may be exempted from the requirement (in other words, these sounds may be rendered). A process such as dynamic range control may also affect the rendering, and therefore the area, if the audio output level is considered in the area definition. 
     The level based audio object rendering system  140  is configured to implement a parameterized audio-object interaction detection and rendering control via tracking of the listening position for audio rendering volume level. By considering the sound pressure level of the audio at the listening position, the contribution of the spatial audio environment automatically is taken into account. The level based audio object rendering system  140  may furthermore determine metadata for parameterized audio-object interaction detection and rendering control via tracking of the listening position for audio rendering volume level. 
     The audio-object interaction may be defined as a modification of the audio-object rendering for presentation to the user due to a triggering based on at least a user position in the spatial audio scene overlapping with an audio object position. While this locational conflict abnormality may be defined in some systems or example embodiments based on a metadata parameter specifying at least a first distance between the user and the audio object, the level based audio object rendering system  140  may require no distance metadata to determine an overlap or audio-object interaction. Instead, the level based audio object rendering system  140  may use metadata related to perception of the audio (for example, the volume or level per frequency bin) to determine the overlap. Thus, the level based audio object rendering system  140  may automatically take into account the room acoustics contribution of an individual audio object for its interaction control. The level estimation may generally be done per frequency bin and these measures may then be combined into a single measure, for example, in a manner incorporating psychoacoustics. 
     Considering the above, level based audio object rendering system  140  may allow both 1) an alternative implementation for audio-object interactions significantly differing from the distance based systems and 2) an improvement over the distance based systems in terms of providing a capability to adjust for sound pressure and a spatial environment. 
     Referring also to  FIG. 2 , the reality system  100  generally comprises one or more controllers  210 , one or more inputs  220  and one or more outputs  230 . The input(s)  220  may comprise, for example, location sensors of the relative location system  130  and the level based audio object rendering system  140 , rendering information for level based audio object rendering system  140 , reality information from another device, such as over the Internet for example, or any other suitable device for inputting information into the system  100 . The output(s)  230  may comprise, for example, a display on a VR headset of the visual system  110 , speakers of the audio system  120 , and a communications output to communication information to another device. The controller(s)  210  may comprise one or more processors  240  and one or more memory  250  having software  260  (or machine-readable instructions). 
     Referring also to  FIGS. 3 a  and 3 b   , diagrams  300 ,  350  illustrating characteristics of free-viewpoint content consumption are shown. 
       FIG. 3 a    illustrates a user  310  navigating around an audiovisual free-viewpoint VR experience  300 . The user  310  is surrounded by a nature scene, where the user  310  hears, for example, birds singing  320  around the user  310  and bees buzzing  330  at some distance in front of the user  310 . As the user  310  moves forward ( FIG. 3 b   ), the user  310  may come into contact with the beehive  340  that may, in terms of audio (or audio-wise), consist, for example, of a single audio-object. This is an example use case in which a definition for an interaction between the user and the audio-object is required for an immersive free-viewpoint audio experience. 
     In instances in which sound is detected by microphones (in a similar manner as by ears), the sound is determined based on sound pressure. In acoustics, the sound pressure of a spherical wave-front that radiates from a point source is known to decrease by 6.02 dB with a doubling of the distance. This corresponds to a decrease of 50%, or a halving, of the sound pressure. Accordingly, the sound pressure decreases as 1/r, while the sound intensity decreases as 1/r 2 . This may be reflected in the sound that the user  310  experiences as they move throughout the audiovisual free-viewpoint VR experience  300 . 
     Referring also to  FIGS. 4 a  and 4 b   , diagrams illustrating a VR user listening to the same audio source in an open space ( 4   a ) and a space with strong reflections ( 4   b ) are shown. 
       FIGS. 4 a  and 4 b    present a user  410  listening to 6DoF free-viewpoint audio content, illustrated in this instance as sound emanating from audio source  420  (illustrated as a dinosaur). In an open space ( FIG. 4 a   ), the user  410  mainly hears the direct sound component  430  from a sound source  420 . However, when the same audio source is placed into a reverberant space  440 , such as a room or a cave ( FIG. 4 b   ), the user  410  may increasingly receive (and hear) additional reflections  450  as well as the direct sound  430 . The characteristics of the environment and the relative positions of the user  410  and the sound source  420  may determine how these components are combined and what the sum  460  (of direct sound and reflections) will sound like. Embodiments described herein provide functionality for immersive 6DoF use cases, based on level based audio object rendering system  140  considering the differences between the spatial audio environments. 
     Referring back to  FIGS. 4 a  and 4 b   , implementation of an audio-object interaction system that does not incorporate the effect of reflections, the same inherent audio-object interaction for the two cases of  FIGS. 4 a  and 4 b    may be determined. However, level based audio object rendering system  140  may determine (for example, observe) that the reflections (in  FIG. 4 b   ) contribute to the received sound pressure 1) picked up by our ears in the real world, or 2) to the presentation level through headphones in the virtual 6DOF free-viewpoint world), and may adjust to compensate for the difference between the two cases to the user percept. In instances in which the difference is not compensated for, problems may arise for two reasons, among other reasons. Firstly, the percept in case of  FIG. 4 b    may be louder. As the audio-object interaction may result in increase of the playback volume, the additional loudness caused by the environment may become disturbing. Secondly, the audio-object interaction may result in an audio rendering modification such as, for example, added reverberance (for example, added reverberant or echoing sounds may result). The spatial audio environment may similarly add reverberance to the percept. These two different modification components may interact in a way which does not result in the desired output percept. For example, the volume may greatly vary over time or the reverberance may become very strong or noisy. 
     Level based audio object rendering system  140  may provide support for processes of audio-object interactions in spatial audio environments. Level based audio object rendering system  140  may process the interactions such that for two instances of an audio object, such as those illustrated in  FIGS. 4 a  and 4 b   , will behave differently because their rendering instructions (metadata) are different and an interaction definition based on object-to-user distance takes the environment into account. Level based audio object rendering system  140  may implement processes that overcome the liabilities to ad hoc approaches to correcting the difference in spatial environment (for example, ad hoc approaches such as adapting an audio object to different known environments through manual work by the content creator (and with support of additional metadata)). Level based audio object rendering system  140  may provide capability to adapt rendering in a highly interactive audiovisual space that may also be modified during consumption. Thus, in response to changes in the acoustic and/or “physical” properties of the space during the content consumption, Level based audio object rendering system  140  may provide controls that take these changes into account in rendering. For example, the roof or walls of a building may be opened, or the audio objects may be moved, for example, from a very large room to a much smaller room. One example of this is a multi-user use case of sharing content from a first space into a second space. Level based audio object rendering system  140  may provide tools to address these changes in a direct manner. 
     Level based audio object rendering system  140  may consider the spatial audio environment for audio-object interactions. Level based audio object rendering system  140  may factor the environment into renderings in order to provide the most immersive user experience for the user. Level based audio object rendering system  140  may provide processes that correspond to the dynamic nature of the audiovisual environment itself, and reduce or eliminate a necessity for manual controls of the spatial audio environment through separate parameters, which may become a time and/or resource consuming task. Level based audio object rendering system  140  may allow for creating (or be incorporated into) more efficient content creation tools. 
     Level based audio object rendering system  140  may implement a parameterized audio-object interaction detection and rendering control system, based on tracking of the listening position audio rendering volume level. The listening position in the audio space may be associated with a user and, in some example embodiments, may be a free-view and in other example embodiments 3DoF AR/VR. The audio space may refer to the AR/VR space populated by one or more audio sources. The user may have a listening position in this space, and the listening position (which may include the head rotation of the user) affects the rendering. By considering the sound pressure or volume level of the audio at the listening position in an audio space, level based audio object rendering system  140  may automatically take into account the contribution of the spatial audio environment. This is because the environment directly contributes to the listening position sound pressure through reflections etc. In instances in which the level based audio object rendering system  140  only considers the direct sound (for example, for complexity reasons) the level based audio object interaction rendering system  140  may behave similarly (for example, determine audio objects interactions in a similar manner) to systems which determine tracking solely based on distance information. Level based audio object rendering system  140  may track the distance between the listening position and the audio object. The acoustic space may not have an effect on this distance. Level based audio object rendering system  140  may detect and measure the effect of the environment on the audio-object interaction. 
     The listening environment may refer to the part of the audio space that may affect (for example, by modeling of the geometry etc.) the rendering of at least the audio source under consideration (for example, an audio interaction) at the user&#39;s listening position in the audio space. The listening environment may in some instances refer to the physical space of the user but does not necessarily correspond to the physical space. For example, with regard to VR use cases, the listening environment may not correspond to a physical space as the system attempts to remove the user from the real world. In instances of AR, the physical space may actually be the listening environment. However, in an example advanced AR use case, the rendering may take into account the physical space around the user as well as a virtual (augmented) element of the audio space. 
     In some example embodiments, the spatial audio environment effects such as reverberation may be evaluated and utilized for the audio-object interaction detection and control separately from the direct sound pressure. 
     Level based audio object rendering system  140  may improve a content creator&#39;s ability to take into account various aspects of the 6DoF audio environment and experience thus allowing for improved user experience. In some instances, a content creator may provide instructions to have the spatial audio environment not implement an effect on the audio-object interactions, for example by defining a metadata flag to override this functionality. Level based audio object rendering system  140  may therefore allow the content creator to enable either 1) audio object interactions that do not factor the spatial environment or 2) audio object interactions that factor the spatial environment, depending on the use case. 
     Level based audio object rendering system  140  may be implemented in a standalone audio-interaction rendering system, and may also be used in conjunction with systems that determine renderings of audio object interactions based (for example, only) on distance metadata. Level based audio object rendering system  140  may be implemented, for example, through defining a set of parameters that are stored and transmitted as audio-object metadata. Alternatively, such metadata may refer to a channel, a track, or, for example, a set of directional audio sub-band components or parameters. Level based audio object rendering system  140  may be implemented in a spatial audio rendering software product and in any hardware product that allows for 6DoF immersive audio experiences. 
     Level based audio object rendering system  140  may enable intuitive audio-object interactions that may automatically take room acoustic properties into account to provide improved realism and immersion. 
     Referring also to  FIG. 5 , an example illustration  500  of a high-level block diagram of interaction detection and audio-object modification is shown. 
       FIG. 5  illustrates interaction detection and audio-object modification based on distance parameters. The processes illustrated in  FIG. 5  may be implemented in some example embodiments together with systems for level based audio object rendering. 
     As shown in  FIG. 5 , at step  510 , a system that determines renderings of audio object interactions based on distance metadata (not shown, for example, a system such as further described in U.S. patent application Ser. No. 15/293,607, filed Oct. 14, 2016, which is hereby incorporated by reference), may monitor for and detect an audio object interaction. The system may determine whether a change in interaction has been detected  520 . If no change  530  in interaction is detected, the system may continue to monitor for interactions  510 . 
     In instances in which a reduced interaction is detected (step  540 ), the system may apply adjustment based on reversibility  570  and send the modification information to an audio object spatial rendering engine  580 . In instances in which an increased audio object interaction is detected (step  550 ), the system may apply adjustment based on effective distance  560  and send the modification information to an audio object spatial rendering engine  580 . The audio object spatial modification engine may take care of applying the modification of the audio-object for rendering/presentation to the user. 
     Referring also to  FIG. 6 , an example block diagram illustrating a level based audio object rendering system  140  is shown. Level based audio object rendering system  140  includes an audio object default rendering component  610 , an audio object interaction adjustment component  620 , and an audio object spatial rendering engine  630 . 
     Level based audio object rendering system  140  may apply processes so that the audio-object interaction modification of a single audio object performed by the modification engine acoustically differs between an open space and a closed space. Level based audio object rendering system  140  may provide the content creator with intuitive and efficient tools to take requirements of differences between open spaces and closed spaces into account in designing an overall user experience. Level based audio object rendering system  140  may provide an alternative method of interaction detection to adding parameters to the framework proposed in U.S. patent application Ser. No. 15/293,607, filed Oct. 14, 2016. 
     Audio object default rendering component  610  may determine a default audio rendering based on an audio-object interaction paradigm based on tracking at least one object-to-user distance. As the distance between the audio source and the listener also relates to a change in sound pressure, audio object default rendering component  610  may use the sound pressure of the audio object as observed at the listening position as the basis for determining the triggering and the strength of the audio-object interaction. 
     Audio object default rendering component  610  may (at least to some degree) define the effect of the spatial audio environment to listener percept in terms of the volume level (or sound pressure). Further, to control further changes in user&#39;s percept due to the spatial audio environment, such as reverberance, audio object interaction adjustment component  620  may also consider measures or parameters related to such effects. 
     Audio object default rendering component  610  may observe at least the rendering of each audio object in the current spatial audio environment at the user&#39;s listening position (for example, the rendering position). Audio object default rendering component  610  may define as ‘default rendering’ the rendering of the audio-object at the user listening position in absence of any audio-interaction. 
     Audio object interaction adjustment component  620  may obtain (for example, at least in some embodiments also) the corresponding rendering under an ongoing audio-object interaction. Audio object interaction adjustment component  620  may thereby take into account for example a position change of the audio object due to the audio-object interaction. 
     The default rendering may in some example embodiments include the effect of the spatial audio environment, meaning the reflections or even obstacles (which may in some example embodiments include other users) that may affect the direct sound. In some example embodiments, the default rendering may not include these effects related to the environment. In these instances, audio object interaction adjustment component  620  may provide an implementation of the audio object interactions in which no explicit distance metadata is used. 
     Audio object interaction adjustment component  620  may compare the default rendering against at least one threshold that the content creator may provide instructions to the system to generally define (for example, via an entry to a metadata field that is part of a content download). This may be a relative measure based on the direct audio object time-domain signal where the time of travel between the audio source and the user&#39;s listening point has been compensated for. Thus, the measure may be a single value or it may be, for example, a time-varying threshold envelope depending on the implementation. The threshold may be a measure of sound pressure or a measure related to sound pressure. The threshold may be, for example, a value expressed in decibels (dB). This time-varying threshold envelope may allow a different interaction response strength at different times. The interaction response may vary according to playback time of the audio, playback time of the whole experience, or a particular time-based input that is provided. 
     Audio object interaction adjustment component  620  may determine the case of an ongoing audio-object interaction and the detection of a new audio-object interaction in separate manners. This is for two reasons. Firstly, audio object interaction adjustment component  620  may implement separate thresholds for triggering an audio-object interaction and maintaining one. 
     Audio object interaction adjustment component  620  may implement these different thresholds in a similar manner as the first distance parameter effective distance and other modification parameter reversibility are implemented, by way of example, in  FIG. 5 . The effective distance and reversibility parameters, however, do not allow for directly taking into account the spatial audio environment, which the audio object interaction adjustment component  620  may achieve. Further, audio object interaction adjustment component  620  may provide a capability to allow for a different set of modification parameters to take effect when an audio-object interaction is ended. The audio object default rendering and the interaction may be implemented by the audio object spatial rendering engine  630 . 
     Level based audio object rendering system  140  may be implemented with other audio object interaction systems such as a spatial audio rendering point extension (for example using a system such as described in U.S. patent application Ser. No. 15/412,561, filed Jan. 23, 2017, which is hereby incorporated by reference) and smooth rendering of overlapping audio-object interactions (for example using a system such as described in U.S. patent application Ser. No. 15/463,513, filed Mar. 20, 2017, which is hereby incorporated by reference). These systems may be exploited in conjunction with level based audio object rendering system  140 , which may provide audio-object interaction detection based on the level of the percept. 
       FIG. 7  is an example high-level block diagram  700  of interaction detection and audio-object modification. 
       FIG. 7  illustrates a high-level block diagram of the audio-object interaction detection and interaction modification of an audio object that may be implemented by level based audio object rendering system  140 , for example using processes as described herein with respect to  FIG. 6  hereinabove. 
     As shown in  FIG. 7 , at block  705 , the system may obtain an audio object default rendering. 
     At step  710 , the system may determine whether the audio object rendering was previously under interaction. If the audio object rendering was previously under interaction ( 715 , yes), the system may compare a sound pressure measure (for example, related to interaction of the rendering) against an active threshold  720  and determine if the sound pressure measure is equal to or exceeds the threshold  725 . If the sound pressure measure equals or exceeds the threshold (yes, over  735 ), the system may apply an audio object interaction adjustment  740  and send modification information to audio object spatial rendering engine  630 . If the sound pressure measure is under the threshold (no,  770 ), the system may phase out interaction and send corresponding information to audio object spatial rendering engine  630  (step  750 ). 
     At step  710 , if the audio object rendering was not previously under interaction  725 , no, the system may compare the sound pressure measure against a trigger threshold  730  and determine if the sound pressure measure is equal to or exceeds the threshold  755 . If the sound pressure measure equals or exceeds the trigger threshold (yes, over  760 ), the system may apply an audio object interaction adjustment  740  and send modification information to audio object spatial rendering engine  630 . If the sound pressure measure is under the trigger threshold (no,  775 ), the system may send default information to audio object spatial rendering engine  630  (step  765 ). 
     Step  765  (for example, send default information to audio object spatial rendering engine  630 ) and step  750  (for example, phase out interaction and send corresponding information to audio object spatial rendering engine) may be the same in some example embodiments. At least in some example embodiments, an audio-object interaction that ends may be phased out using a specific set of modification parameters that differ from both the default rendering and the audio-object interaction rendering. The content creator may, for example, provide instructions to make it clear for a user that an audio-object interaction has just ended. The content creator may define a response, for example, based on an audio effect/processing that is rendered according to a metadata setting that is stored in the content stream. This may be achieved, for example, by using a specific (for example, particular visual, haptic and/or aural) effect. The user may be presented with audio according to the set metadata. The user may experience the effect and thereby understand that a change in rendering, the interaction has ended. 
     The sound pressure measure and the (active and trigger) thresholds relate to the audio-object audio, which may be available for the system (or rendered by the system). Thus, the system may require no other calibration or reference volume level. However, in some example embodiments there may be at least one calibration level or other reference (such as a reference signal), which may be utilized for example for purposes of dynamic range control (DRC). 
     In some example embodiments, the system may separately compare the direct sound and reflections. This may be done, for example, in order not to duplicate a reverberation effect. Such duplication may happen, for example, if a user interacts with an audio object in a highly reverberant space and the interaction metadata associated with the audio source or object (including instructions provided by the content, reflecting the content creator&#39;s choice of interaction effect) also consists of a reverb effect. Thus, the audio object spatial modification engine  630  may in such instances ignore a specific audio-object interaction modification (such as the reverb effect), and it may, at least in some example embodiments, substitute this with another effect. In some example embodiments, a secondary effect may be communicated by the content creator using a metadata entry. 
       FIG. 8  shows a method in accordance with example embodiments which may be performed by an apparatus.  FIG. 8  illustrates a summary overview of processes according to an example embodiment. While some example embodiments may specifically consider object-based audio, other embodiments described herein may address 6DoF audio more generally. 
     At block  810 , the system may obtain the listening position (the virtual user position). This may include the listening position and rotation associated with the user. 
     At block  820 , based on the listening position, the system may then obtain the audio (such as audio objects) to be rendered to the user for this position. At least in some example embodiments, the user rotation may already be considered in these steps. 
     At block  830 , the system may obtain the listening environment description or model of the environment. This model may specify how the audio rendering is modified by the environment at the listening position. This may include reflections, damping by various materials, and in some example embodiments, active scene understanding such as the effect of other users. 
     In some example embodiments, the listening environment may include a VR model or a real AR space of a user. The AR implementations (for example, for different use cases) may be processed as an extension of VR use case, in which a capture device in AR consumption may obtain (at a minimum) a base model of the real room acoustics and after that utilize the similar steps as for the VR use case. 
     The effect of the listening environment for the percept may be based on the accuracy of particular implementation. For example, a simple example implementation may consider the direct sound and a single reflection only, or a direct sound with a reverberation effect derived based on the model. A complex example implementation, on the other hand, may consider a high number of reflections or the real room impulse response (RIR). 
     Thus, the (default) rendering of the audio is available for the spatial audio rendering system  630 . In a more advanced system, any effects of the spatial audio environment are similarly available for the renderer. 
     The system (at block  840 ) may detect interaction at listening position by comparing audio rendering level against corresponding level threshold metadata. For example, the system may compare the sound pressure of the audio rendering (in some example embodiments, including the spatial audio environment effects) against the at least one threshold after having defined and made available metadata related to at least one sound pressure threshold. This allows for detection of the audio interactions and also the control of their extent. 
     At block  850 , the system may apply the modification to the audio according to the audio interaction detection results. 
     At block  860 , the audio may be rendered at the listening position and presented to the user. At least at this step, the rotation of the user&#39;s head may also be considered in order to correctly present the spatial audio directions. 
     Without in any way limiting the scope, interpretation, or application of the claims appearing below, a technical effect of one or more of the example embodiments disclosed herein is that the system enables intuitive audio-object interactions that may automatically take room acoustic properties into account to provide improved realism and immersion. Another advantage of the system is that, when particular conditions are fulfilled, the system may use modification parameters, such as location, scale, rotation, amplification, equalization, directiveness (for example, the direction in which the sound propagates), and time shift. In addition, further modification parameters, such as spatial extent and reverb may be used. 
     It is furthermore noted that in some example implementations, both the volume-based (for example as implemented by level based audio object rendering system  140 ) and the distance-based aspects may be considered together. For example, a specific content may support only one of these methods. A renderer implementation may then utilize the set of processes that enables the intended experience for the user given the available metadata. In another example embodiment, a content creator may provide instructions to differentiate between a first set of audio-object interactions that depend on the spatial audio environment and a second set that do not. This may be achieved via use of a dedicated metadata flag. 
     The example embodiments may provide tools that allow a content creator to define their content&#39;s rendering as well as possible (for example, with greater correspondence to a physical audio environment). Taking into account the effects of the spatial audio environment enables this. Additionally, a metadata flag may allow for switching between the two modes of operation for each audio-object (and, in some instances, the flag may be time-varying), which greatly enhances the content creator&#39;s creative choices. This increases the accuracy of representations as one of the key differentiators of 6DoF AR/VR is the user&#39;s ability to roam the scene and both have the scene react to the user and allow the user to directly interact with various objects. 
     In accordance with an example, a method may include obtaining a listening position associated with a user; obtaining audio and metadata corresponding to a rendering at the listening position; obtaining a listening environment and determining an effect of the listening environment on the rendering at the listening position; detecting audio interaction at the listening position by comparing an audio rendering level against a corresponding level threshold metadata; applying, by a processing device, an audio modification according to the audio interaction detection; and rendering audio at the listening position based on the applied audio modification. 
     In accordance with another example, wherein detecting the audio interaction at the listening position by comparing the audio rendering level against the corresponding level threshold metadata further comprises: determining whether the audio at the listening position was previously under interaction; in response to a determination that the audio at the listening position was previously under interaction, comparing the audio at the listening position to an active threshold; and in response to a determination that the audio is over the active threshold, applying an audio interaction adjustment and sending modification information to an audio object spatial rendering engine. 
     In accordance with another example, in response to a determination that the audio is under the active threshold, phasing out the audio interaction and sending corresponding information to the audio object spatial rendering engine. 
     In accordance with another example, providing a specific effect to notify a user than an audio object interaction has ended. 
     In accordance with another example, wherein detecting the audio interaction at the listening position by comparing the audio rendering level against the corresponding level threshold metadata further comprises: determining whether the audio at the listening position was previously under interaction; in response to a determination that the audio at the listening position was not previously under interaction, comparing the audio at the listening position to a trigger threshold; and in response to a determination that the audio is over the trigger threshold, applying an audio interaction adjustment and sending modification information to an audio object spatial rendering engine. 
     In accordance with another example, in response to a determination that the audio is under the trigger threshold, sending default information to the audio object spatial rendering engine. 
     In accordance with another example, wherein the audio rendering level comprises at least one of a sound pressure level and a volume level. 
     In accordance with another example, wherein detecting the audio interaction at the listening position by comparing the audio rendering level against the corresponding level threshold metadata further comprises: comparing separately a direct sound and a reflected sound; and ignoring a reverb effect if the reverb effect is detected. 
     In accordance with another example, substituting a secondary effect for the reverb effect. 
     In accordance with another example, checking a metadata flag to determine whether to apply the audio modification. 
     In accordance with another example, wherein the audio and the metadata further comprises: one or more of at least one track, at least one channel, and a set of directional sub-band components. 
     In accordance with another example, an example apparatus may comprise at least one processor; and at least one non-transitory memory including computer program code, the at least one memory and the computer program code configured to, with the at least one processor, cause the apparatus to: obtain a listening position associated with a user; obtain audio and metadata corresponding to a rendering at the listening position; obtain a listening environment and determine an effect of the listening environment on the rendering at the listening position; detect audio interaction at the listening position by comparing an audio rendering level against a corresponding level threshold metadata; apply an audio modification according to the audio interaction detection; and render audio at the listening position based on the applied audio modification. 
     In accordance with another example, an example apparatus may comprise a non-transitory program storage device readable by a machine, tangibly embodying a program of instructions executable by the machine for performing operations, the operations comprising: obtaining a listening position associated with a user; obtaining audio and metadata corresponding to a rendering at the listening position; obtaining a listening environment and determining an effect of the listening environment on the rendering at the listening position; detecting audio interaction at the listening position by comparing an audio rendering level against a corresponding level threshold metadata; applying an audio modification according to the audio interaction detection; and rendering audio at the listening position based on the applied audio modification. 
     In accordance with another example, an example apparatus comprises: means for obtaining a listening position associated with a user; means for obtaining audio and metadata corresponding to a rendering at the listening position; obtaining a listening environment and determining an effect of the listening environment on the rendering at the listening position; means for detecting audio interaction at the listening position by comparing an audio rendering level against a corresponding level threshold metadata; means for applying an audio modification according to the audio interaction detection; and means for rendering audio at the listening position based on the applied audio modification. 
     Any combination of one or more computer readable medium(s) may be utilized as the memory. The computer readable medium may be a computer readable signal medium or a non-transitory computer readable storage medium. A non-transitory computer readable storage medium does not include propagating signals and may be, for example, but not limited to, an electronic, magnetic, optical, electromagnetic, infrared, or semiconductor system, apparatus, or device, or any suitable combination of the foregoing. More specific examples (a non-exhaustive list) of the computer readable storage medium would include the following: an electrical connection having one or more wires, a portable computer diskette, a hard disk, a random access memory (RAM), a read-only memory (ROM), an erasable programmable read-only memory (EPROM or Flash memory), an optical fiber, a portable compact disc read-only memory (CD-ROM), an optical storage device, a magnetic storage device, or any suitable combination of the foregoing. 
     It should be understood that the foregoing description is only illustrative. Various alternatives and modifications can be devised by those skilled in the art. For example, features recited in the various dependent claims could be combined with each other in any suitable combination(s). In addition, features from different embodiments described above could be selectively combined into a new embodiment. Accordingly, the description is intended to embrace all such alternatives, modifications and variances which fall within the scope of the appended claims.