Qualcomm Patent | Privacy restrictions for audio rendering

Patent: Privacy restrictions for audio rendering

Drawings: Click to check drawins

Publication Number: 20210006976

Publication Date: 20210107

Applicant: Qualcomm

Abstract

A method and device for processing one or more audio streams based on privacy restrictions is described. A device may be configured to receive the one or more audio streams from audio elements represented in an acoustic environment that comprises one or more sub-acoustic spaces, each of the one or more audio streams representative of a respective soundfield, determine unrestricted audio streams of the one or more audio streams based on privacy restrictions associated with the one or more audio streams, determine restricted audio streams of the one or more audio streams based on the privacy restrictions associated with the one or more audio streams, generate the corresponding respective soundfields of the unrestricted audio streams, and restrict playback of the corresponding respective soundfields of the restricted audio streams.

Claims

  1. A device configured to process one or more audio streams, the device comprising: a memory configured to store the one or more audio streams; and one or more processors coupled to the memory, and configured to: receive the one or more audio streams from audio elements represented in an acoustic environment that comprises one or more sub-acoustic spaces, each of the one or more audio streams representative of a respective soundfield; determine unrestricted audio streams of the one or more audio streams based on privacy restrictions associated with the one or more audio streams; determine restricted audio streams of the one or more audio streams based on the privacy restrictions associated with the one or more audio streams; generate the corresponding respective soundfields of the unrestricted audio streams; and restrict playback of the corresponding respective soundfields of the restricted audio streams.

  2. The device of claim 1, wherein the privacy restriction associated with the one or more audio streams are embedded in the one or more audio streams, and wherein the one or more processors are further configured to: extract the privacy restrictions from the one or more audio streams.

  3. The device of claim 1, wherein the one or more processors are configured to: receive metadata that includes the privacy restrictions associated with the one or more audio streams.

  4. The device of claim 1, wherein to restrict playback of the corresponding respective soundfields of the restricted audio streams, the one or more processors are further configured to: toggle off the restricted audio streams.

  5. The device of claim 1, wherein to restrict playback of the corresponding respective soundfields of the restricted audio streams, the one or more processors are further configured to: mask the restricted audio streams.

  6. The device of claim 1, wherein to restrict playback of the corresponding respective soundfields of the restricted audio streams, the one or more processors are further configured to: null the restricted audio streams.

  7. The device of claim 1, wherein to restrict playback of the corresponding respective soundfields of the restricted audio streams, the one or more processors are further configured to: apply an acoustic occluder to the restricted audio streams.

  8. The device of claim 1, wherein the privacy restrictions indicate if one or more of the one or more audio streams are restricted or unrestricted for each of a plurality of privacy settings ranks, and wherein the one or more processors are further configured to: determine a privacy setting rank from the plurality of privacy setting ranks; determine unrestricted audio streams of the one or more audio streams based on privacy restrictions associated with the one or more audio streams and the privacy setting rank; and determine restricted audio streams of the one or more audio streams based on the privacy restrictions associated with the one or more audio streams and the privacy setting rank.

  9. The device of claim 1, wherein the privacy restrictions indicate if a single audio stream of the one or more audio streams is restricted or unrestricted.

  10. The device of claim 1, wherein the privacy restrictions indicate if a cluster of audio stream of the one or more audio streams is restricted or unrestricted, wherein the cluster of audio streams are associated with a sub-acoustic space of the one or more sub-acoustic spaces.

  11. The device of claim 10, wherein the privacy restrictions indicate if respective audio streams from a first cluster of audio elements are restricted or unrestricted, and wherein the privacy instructions further indicate if respective audio streams from a second cluster of audio elements share the same privacy restrictions as the first cluster of audio elements.

  12. The device of claim 1, wherein the audio elements include one or more of a single microphone, an array of microphones, a mobile device, or a synthesized audio source.

  13. The device of claim 1, wherein the device comprises an extended reality headset.

  14. The device of claim 1, further comprising a head-mounted display configured to present a displayed world, wherein the privacy restrictions further include respective audio element location information representative of a respective location in the displayed world at which a respective audio stream of the one or more audio streams was generated, and wherein the one or more processors are configured to: determine device location information representative of a location of the device in the displayed world; select, based on the device location information and the audio element location information, a subset of the one or more audio streams, the subset of the one or more audio streams excluding at least one of one or more audio streams; and generate, based on the subset of the one or more audio streams, the corresponding soundfields.

  15. The device of claim 1, further comprising a modem, the modem configured to receive the one or more audio streams via a wireless link.

  16. The device of claim 15, wherein the wireless link is one or more of 5G, WiFI, or Bluetooth.

  17. A method of processing one or more audio streams, the method comprising: receiving the one or more audio streams from audio elements represented in an acoustic environment that comprises one or more sub-acoustic spaces, each of the one or more audio streams representative of a respective soundfield; determining unrestricted audio streams of the one or more audio streams based on privacy restrictions associated with the one or more audio streams; determining restricted audio streams of the one or more audio streams based on the privacy restrictions associated with the one or more audio streams; generating the corresponding respective soundfields of the unrestricted audio streams; and restricting playback of the corresponding respective soundfields of the restricted audio streams.

  18. The method of claim 17, wherein the privacy restriction associated with the one or more audio streams are embedded in the one or more audio streams, the method further comprising: extracting the privacy restrictions from the one or more audio streams.

  19. The method of claim 17, further comprising: receiving metadata that includes the privacy restrictions associated with the one or more audio streams.

  20. The method of claim 17, wherein restricting playback of the corresponding respective soundfields of the restricted audio streams comprises: toggling off the restricted audio streams.

  21. The method of claim 17, wherein restricting playback of the corresponding respective soundfields of the restricted audio streams comprises: masking the restricted audio streams.

  22. The method of claim 17, wherein restricting playback of the corresponding respective soundfields of the restricted audio streams comprises: nulling the restricted audio streams.

  23. The method of claim 17, wherein restricting playback of the corresponding respective soundfields of the restricted audio streams comprises: applying an acoustic occluder to the restricted audio streams.

  24. The method of claim 17, wherein the privacy restrictions indicate if one or more of the one or more audio streams are restricted or unrestricted for each of a plurality of privacy settings ranks, the method further comprising: determining a privacy setting rank from the plurality of privacy setting ranks; determining unrestricted audio streams of the one or more audio streams based on privacy restrictions associated with the one or more audio streams and the privacy setting rank; and determining restricted audio streams of the one or more audio streams based on the privacy restrictions associated with the one or more audio streams and the privacy setting rank.

  25. The method of claim 17, wherein the privacy restrictions indicate if a single audio stream of the one or more audio streams is restricted or unrestricted.

  26. The method of claim 17, wherein the privacy restrictions indicate if a cluster of audio stream of the one or more audio streams is restricted or unrestricted, wherein the cluster of audio streams are associated with a sub-acoustic space of the one or more sub-acoustic spaces.

  27. The method of claim 17, wherein the method is performed by an extended reality headset.

  28. The method of claim 17, further comprising: displaying, with a head-mounted display, a displayed world, wherein the privacy restrictions further include respective audio element location information representative of a respective location in the displayed world at which a respective audio stream of the one or more audio streams was generated; determining device location information representative of a location of the device in the displayed world; selecting, based on the device location information and the audio element location information, a subset of the one or more audio streams, the subset of the one or more audio streams excluding at least one of one or more audio streams; and generating, based on the subset of the one or more audio streams, the corresponding soundfields.

  29. A non-transitory computer-readable medium storing instructions that, when executed, causes one or more processors of a device configured to process one or more audio streams to: receive the one or more audio streams from audio elements represented in an acoustic environment that comprises one or more sub-acoustic spaces, each of the one or more audio streams representative of a respective soundfield; determine unrestricted audio streams of the one or more audio streams based on privacy restrictions associated with the one or more audio streams; determine restricted audio streams of the one or more audio streams based on the privacy restrictions associated with the one or more audio streams; generate the corresponding respective soundfields of the unrestricted audio streams; and restrict playback of the corresponding respective soundfields of the restricted audio streams.

  30. An apparatus configured to process one or more audio streams, the apparatus comprising: means for receiving the one or more audio streams from audio elements represented in an acoustic environment that comprises one or more sub-acoustic spaces, each of the one or more audio streams representative of a respective soundfield; means for determining unrestricted audio streams of the one or more audio streams based on privacy restrictions associated with the one or more audio streams; means for determining restricted audio streams of the one or more audio streams based on the privacy restrictions associated with the one or more audio streams; means for generating the corresponding respective soundfields of the unrestricted audio streams; and means for restricting playback of the corresponding respective soundfields of the restricted audio streams.

Description

[0001] This application claims the benefit of U.S. Provisional Application No. 62/870,473, filed Jul. 3, 2019, the entire content of which is incorporated by reference herein.

TECHNICAL FIELD

[0002] This disclosure relates to processing of media data, such as audio data.

BACKGROUND

[0003] Computer-mediated reality systems are being developed to allow computing devices to augment or add to, remove or subtract from, or generally modify existing reality experienced by a user. Computer-mediated reality systems (which may also be referred to as “extended reality systems,” or “XR systems”) may include, as examples, virtual reality (VR) systems, augmented reality (AR) systems, and mixed reality (MR) systems. The perceived success of computer-mediated reality systems is generally related to the ability of such computer-mediated reality systems to provide a realistically immersive experience in terms of both the video and audio experience where the video and audio experience align in ways expected by the user. Although the human visual system is more sensitive than the human auditory systems (e.g., in terms of perceived localization of various objects within the scene), ensuring an adequate auditory experience is an increasingly important factor in ensuring a realistically immersive experience, particularly as the video experience improves to permit better localization of video objects that enable the user to better identify sources of audio content.

SUMMARY

[0004] This disclosure relates generally to auditory aspects of the user experience of computer-mediated reality systems, including virtual reality (VR), mixed reality (MR), augmented reality (AR), computer vision, and graphics systems. Various aspects of the techniques may provide for user control of audio rendering of an acoustical space for extended reality systems. As used herein, an acoustic environment is represented as either an indoor environment or an outdoor environment, or both an indoor environment and an outdoor environment. The acoustic environment may include one or more sub-acoustic spaces that may include various acoustic elements. A sub-acoustic space may, for example, be a room, or an area within a room or building, the cabin of a vehicle, a classroom, an area within a classroom, or any subset of any type of acoustic space. An example of an outdoor environment could include a car, buildings, walls, a forest, etc.

[0005] An acoustic space may be an example of an acoustic environment and may be an indoor space or an outdoor space. As used herein, an audio element may be a sound captured by a microphone (e.g., directly captured from near-filed sources or reflections from far-field sources whether real or synthetic), a sound captured by an array of microphones, a soundfield previously synthesized, a mono sound synthesized from text to speech, and/or a reflection of a virtual sound from an object in the acoustic environment.

[0006] When rendering an XR scene (e.g., a six degrees of freedom (6DOF) XR scene) with many audio sources which may be obtained from audio elements of a live scene, certain audio elements or clusters of audio elements may contain sensitive information and/or may be meant for restricted or exclusive access. In accordance with the techniques of this disclosure, an audio playback device (e.g., a VR or XR device) may be configured to determine one or more audio streams from privacy restrictions that indicate if one or more of the plurality of audio streams are restricted or unrestricted.

[0007] The privacy restrictions may be embedded in information in the audio streams and/or may be transmitted in metadata that accompanies the audio streams. The audio playback device may then generate the corresponding soundfields based on the privacy restrictions, including restricting playback for certain audio streams that are indicated as being restricted. The privacy restrictions also may apply to individual audio elements and/or a clusters of audio elements. In some examples, the privacy restrictions may be ranked. The techniques of this disclosure allow for both flexible and fine-grained control of audio streams that may be played back in a VR/XR scenario. The techniques of this disclosure may also reduce bandwidth consumption.

[0008] In one example, this disclosure describes a device configured to process one or more audio streams, the device comprising a memory configured to store the one or more audio streams, and one or more processors coupled to the memory, and configured to receive the one or more audio streams from audio elements represented in an acoustic environment that comprises one or more sub-acoustic spaces, each of the one or more audio streams representative of a respective soundfield, determine unrestricted audio streams of the one or more audio streams based on privacy restrictions associated with the one or more audio streams, determine restricted audio streams of the one or more audio streams based on the privacy restrictions associated with the one or more audio streams, generate the corresponding respective soundfields of the unrestricted audio streams, and restrict playback of the corresponding respective soundfields of the restricted audio streams.

[0009] In another example, this disclosure describes a method of processing one or more audio streams, the method comprising receiving the one or more audio streams from audio elements represented in an acoustic environment that comprises one or more sub-acoustic spaces, each of the one or more audio streams representative of a respective soundfield, determining unrestricted audio streams of the one or more audio streams based on privacy restrictions associated with the one or more audio streams, determining restricted audio streams of the one or more audio streams based on the privacy restrictions associated with the one or more audio streams, generating the corresponding respective soundfields of the unrestricted audio streams, and restricting playback of the corresponding respective soundfields of the restricted audio streams.

[0010] In another example, this disclosure describes a non-transitory computer-readable medium storing instructions that, when executed, causes one or more processors of a device configured to process one or more audio streams to receive the one or more audio streams from audio elements represented in an acoustic environment that comprises one or more sub-acoustic spaces, each of the one or more audio streams representative of a respective soundfield, determine unrestricted audio streams of the one or more audio streams based on privacy restrictions associated with the one or more audio streams, determine restricted audio streams of the one or more audio streams based on the privacy restrictions associated with the one or more audio streams, generate the corresponding respective soundfields of the unrestricted audio streams, and restrict playback of the corresponding respective soundfields of the restricted audio streams.

[0011] In another example, this disclosure describes an apparatus configured to process one or more audio streams, the apparatus comprising means for receiving the one or more audio streams from audio elements represented in an acoustic environment that comprises one or more sub-acoustic spaces, each of the one or more audio streams representative of a respective soundfield, means for determining unrestricted audio streams of the one or more audio streams based on privacy restrictions associated with the one or more audio streams, means for determining restricted audio streams of the one or more audio streams based on the privacy restrictions associated with the one or more audio streams, means for generating the corresponding respective soundfields of the unrestricted audio streams, and means for restricting playback of the corresponding respective soundfields of the restricted audio streams.

[0012] The details of one or more examples of this disclosure are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of various aspects of the techniques will be apparent from the description and drawings, and from the claims.

BRIEF DESCRIPTION OF DRAWINGS

[0013] FIGS. 1A and 1B are diagrams illustrating systems that may perform various aspects of the techniques described in this disclosure.

[0014] FIG. 2 is a diagram illustrating an example of a VR device worn by a user.

[0015] FIGS. 3A-3D are diagrams illustrating, in more detail, example operation of the stream selection unit shown in the example of FIG. 1A.

[0016] FIGS. 4A-4E are diagrams illustrating example operations of privacy restrictions performed by the source device and/or content consumer device shown in the examples of FIGS. 1A and 1B.

[0017] FIG. 5 is a diagram illustrating an example of a wearable device that may operate in accordance with various aspect of the techniques described in this disclosure.

[0018] FIGS. 6A and 6B are diagrams illustrating other example systems that may perform various aspects of the techniques described in this disclosure.

[0019] FIG. 7 is a block diagram illustrating example components of one or more of the source device and the content consumer device shown in the example of FIG. 1.

[0020] FIGS. 8A-8C are flowcharts illustrating example operation of the stream selection unit shown in the examples of FIGS. 1A and 1B in performing various aspects of the stream selection techniques.

[0021] FIG. 9 is a flowchart illustrating an example process for processing one or more audio streams based on privacy restrictions using the techniques of this disclosure.

[0022] FIG. 10 illustrates an example of a wireless communications system that supports privacy restrictions in accordance with aspects of the present disclosure.

DETAILED DESCRIPTION

[0023] There are a number of different ways to represent a soundfield. Example formats include channel-based audio formats, object-based audio formats, and scene-based audio formats. Channel-based audio formats refer to the 5.1 surround sound format, 7.1 surround sound formats, 22.2 surround sound formats, or any other channel-based format that localizes audio channels to particular locations around the listener in order to recreate a soundfield.

[0024] Object-based audio formats may refer to formats in which audio objects, often encoded using pulse-code modulation (PCM) and referred to as PCM audio objects, are specified in order to represent the soundfield. Such audio objects may include metadata identifying a location of the audio object relative to a listener or other point of reference in the soundfield, such that the audio object may be rendered to one or more speaker channels for playback in an effort to recreate the soundfield. The techniques described in this disclosure may apply to any of the foregoing formats, including scene-based audio formats, channel-based audio formats, object-based audio formats, or any combination thereof.

[0025] Scene-based audio formats may include a hierarchical set of elements that define the soundfield in three dimensions. One example of a hierarchical set of elements is a set of spherical harmonic coefficients (SHC). The following expression demonstrates a description or representation of a soundfield using SHC:

p i ( t , r r , .theta. r , .PHI. r ) = .omega. = 0 .infin. [ 4 .pi. n = 0 .infin. j n ( k r r ) m = – n n A n m ( k ) Y n m ( .theta. r , .PHI. r ) ] e j .omega. t , ##EQU00001##

[0026] The expression shows that the pressure pi at any point {r.sub.r, .theta..sub.r, .phi..sub.r} of the soundfield, at time t, can be represented uniquely by the SHC, A.sub.n.sup.m(k). Here,

k = .omega. c , ##EQU00002##

c is the speed of sound (.about.343 m/s), {r.sub.r, .theta..sub.r, .phi..sub.r} is a point of reference (or observation point), j.sub.n( ) is the spherical Bessel function of order n, and Y.sub.n.sup.m(.theta..sub.r, .phi..sub.r) are the spherical harmonic basis functions (which may also be referred to as a spherical basis function) of order n and suborder m. It can be recognized that the term in square brackets is a frequency-domain representation of the signal (i.e., S(.omega., r.sub.r, .theta..sub.r, .phi..sub.r)) which can be approximated by various time-frequency transformations, such as the discrete Fourier transform (DFT), the discrete cosine transform (DCT), or a wavelet transform. Other examples of hierarchical sets include sets of wavelet transform coefficients and other sets of coefficients of multiresolution basis functions.

[0027] The SHC A.sub.n.sup.m(k) can either be physically acquired (e.g., recorded) by various microphone array configurations or, alternatively, they can be derived from channel-based or object-based descriptions of the soundfield. The SHC (which also may be referred to as ambisonic coefficients) represent scene-based audio, where the SHC may be input to an audio encoder to obtain encoded SHC that may promote more efficient transmission or storage. For example, a fourth-order representation involving (1+4).sup.2 (25, and hence fourth order) coefficients may be used.

[0028] As noted above, the SHC may be derived from a microphone recording using a microphone array. Various examples of how SHC may be physically acquired from microphone arrays are described in Poletti, M., “Three-Dimensional Surround Sound Systems Based on Spherical Harmonics,” J. Audio Eng. Soc., Vol. 53, No. 11, 2005 Nov., pp. 1004-1025.

[0029] The following equation may illustrate how the SHCs may be derived from an object-based description. The coefficients A.sub.n.sup.m(k) for the soundfield corresponding to an individual audio object may be expressed as:

A.sub.n.sup.m(k)=g(.omega.)(-4.pi.ik)h.sub.n.sup.(2)(kr.sub.s)Y.sub.n.su- p.m*(.theta..sub.s,.phi..sub.s),

where i is {square root over (-1)}, A.sub.n.sup.(2)( ) is the spherical Hankel function (of the second kind) of order n, and {r.sub.s, .theta..sub.s, .phi..sub.s} is the location of the object. Knowing the object source energy g(.omega.) as a function of frequency (e.g., using time-frequency analysis techniques, such as performing a fast Fourier transform on the pulse code modulated–PCM–stream) may enable conversion of each PCM object and the corresponding location into the SHC A.sub.n.sup.m(k). Further, it can be shown (since the above is a linear and orthogonal decomposition) that the A.sub.n.sup.m(k) coefficients for each object are additive. In this manner, a number of PCM objects can be represented by the A.sub.n.sup.m(k) coefficients (e.g., as a sum of the coefficient vectors for the individual objects). The coefficients may contain information about the soundfield (the pressure as a function of 3D coordinates), and the above represents the transformation from individual objects to a representation of the overall soundfield, in the vicinity of the observation point {r.sub.r, .theta..sub.r, .phi..sub.r}.

[0030] Computer-mediated reality systems (which may also be referred to as “extended reality systems,” or “XR systems”) are being developed to take advantage of many of the potential benefits provided by ambisonic coefficients. For example, ambisonic coefficients may represent a soundfield in three dimensions in a manner that potentially enables accurate three-dimensional (3D) localization of sound sources within the soundfield. As such, XR devices may render the ambisonic coefficients to speaker feeds that, when played via one or more speakers, accurately reproduce the soundfield.

[0031] As another example, the ambisonic coefficients may be translated (e.g., rotated) to account for user movement without overly complex mathematical operations, thereby potentially accommodating the low latency requirements of XR. In addition, the ambisonic coefficients are hierarchical and thereby naturally accommodate scalability through order reduction (which may eliminate ambisonic coefficients associated with higher orders), and thereby potentially enable dynamic adaptation of the soundfield to accommodate latency and/or battery requirements of XR devices.

[0032] The use of ambisonic coefficients for XR may enable development of a number of use cases that rely on the more immersive soundfields provided by the ambisonic coefficients, particularly for computer gaming applications and live video streaming applications. In these highly dynamic use cases that rely on low latency reproduction of the soundfield, the XR devices may prefer ambisonic coefficients over other representations that are more difficult to manipulate or involve complex rendering. More information regarding these use cases is provided below with respect to FIGS. 1A and 1B.

[0033] While described in this disclosure with respect to the VR device, various aspects of the techniques may be performed in the context of other devices, such as a mobile device. In this instance, the mobile device (such as a so-called smartphone) may present the displayed world via a screen, which may be mounted to the head of the user 1102 or viewed as would be done when normally using the mobile device. As such, any information on the screen can be part of the mobile device. The mobile device may be able to provide tracking information 41 and thereby allow for both a VR experience (when head mounted) and a normal experience to view the displayed world, where the normal experience may still allow the user to view the displayed world proving a VR-lite-type experience (e.g., holding up the device and rotating or translating the device to view different portions of the displayed world).

[0034] This disclosure relates generally to auditory aspects of the user experience of computer-mediated reality systems, including virtual reality (VR), mixed reality (MR), augmented reality (AR), computer vision, and graphics systems. Various aspects of the techniques may provide for user control of audio rendering of an acoustical space for extended reality systems. As used herein, an acoustic environment is represented as either an indoor environment or an outdoor environment, or both an indoor environment and an outdoor environment. The acoustic environment may include one or more sub-acoustic spaces that may include various acoustic elements. A sub-acoustic space may, for example, be a room, or an area within a room or building, the cabin of a vehicle, a classroom, an area within a classroom, or any subset of any type of acoustic space. An example of an outdoor environment could include a car, buildings, walls, a forest, etc. An acoustic space may be an example of an acoustic environment and may be an indoor space or an outdoor space. As used herein, an audio element may be a sound captured by a microphone (e.g., directly captured from near-filed sources or reflections from far-field sources whether real or synthetic), a sound captured by an array of microphones, a soundfield previously synthesized, a mono sound synthesized from text to speech, and/or a reflection of a virtual sound from an object in the acoustic environment.

[0035] When rendering an XR scene (e.g., a six degrees of freedom (6DOF) XR scene) with many audio sources which may be obtained from audio elements of a live scene, certain audio elements or clusters of audio elements may contain sensitive information and/or may be meant for restricted or exclusive access. In accordance with the techniques of this disclosure, an audio playback device (e.g., a VR or XR device) may be configured to determine one or more audio streams from privacy restrictions that indicate if one or more of the plurality of audio streams are restricted or unrestricted.

[0036] The privacy restrictions may be embedded in information in the audio streams and/or may be transmitted in metadata that accompanies the audio streams. The audio playback device may then generate the corresponding soundfields based on the privacy restrictions, including restricting playback for certain audio streams that are indicated as being restricted. The privacy restrictions also may apply to individual audio elements and/or a clusters of audio elements. In some examples, the privacy restrictions may be ranked. The techniques of this disclosure allow for both flexible and fine-grained control of audio streams that may be played back in a VR/XR scenario. The techniques of this disclosure may also reduce bandwidth consumption.

[0037] FIGS. 1A and 1B are diagrams illustrating systems that may perform various aspects of the techniques described in this disclosure. As shown in the example of FIG. 1A, system 10 includes a source device 12 and a content consumer device 14. While described in the context of the source device 12 and the content consumer device 14, the techniques may be implemented in any context in which any representation of a soundfield is encoded to form a bitstream representative of the audio data. Moreover, the source device 12 may represent any form of computing device capable of generating the representation of a soundfield, and is generally described herein in the context of being a VR content creator device. Likewise, the content consumer device 14 may represent any form of computing device capable of implementing rendering metadata techniques described in this disclosure as well as audio playback, and is generally described herein in the context of being a VR client device.

[0038] The source device 12 may be operated by an entertainment company or other entity that may generate multi-channel audio content for consumption by operators of content consumer devices, such as the content consumer device 14. In some VR scenarios, the source device 12 generates audio content in conjunction with video content. The source device 12 includes a content capture device 20, a content editing device 22, and a soundfield representation generator 24. The content capture device 20 may be configured to interface or otherwise communicate with a microphone 18.

[0039] The microphone 18 may represent an Eigenmike.RTM. or other type of 3D audio microphone capable of capturing and representing the soundfield as audio data 19, which may refer to one or more of the above noted scene-based audio data (such as ambisonic coefficients), object-based audio data, and channel-based audio data. Although described as being 3D audio microphones, the microphone 18 may also represent other types of microphones (such as omni-directional microphones, spot microphones, unidirectional microphones, etc.) configured to capture the audio data 19.

[0040] The content capture device 20 may, in some examples, include an integrated microphone 18 that is integrated into the housing of the content capture device 20. The content capture device 20 may interface wirelessly or via a wired connection with the microphone 18. Rather than capture, or in conjunction with capturing, the audio data 19 via microphone 18, the content capture device 20 may process the audio data 19 after the audio data 19 is input via some type of removable storage, wirelessly and/or via wired input processes. As such, various combinations of the content capture device 20 and the microphone 18 are possible in accordance with this disclosure.

[0041] The content capture device 20 may also be configured to interface or otherwise communicate with the content editing device 22. In some instances, the content capture device 20 may include the content editing device 22 (which in some instances may represent software or a combination of software and hardware, including the software executed by the content capture device 20 to configure the content capture device 20 to perform a specific form of content editing). The content editing device 22 may represent a unit configured to edit or otherwise alter content 21 received from content capture device 20, including the audio data 19. The content editing device 22 may output edited content 23 and associated metadata 25 to the soundfield representation generator 24.

[0042] The soundfield representation generator 24 may include any type of hardware device capable of interfacing with the content editing device 22 (or the content capture device 20). Although not shown in the example of FIG. 1A, the soundfield representation generator 24 may use the edited content 23, including the audio data 19 and metadata 25, provided by the content editing device 22 to generate one or more bitstreams 27. In the example of FIG. 1A, which focuses on the audio data 19, the soundfield representation generator 24 may generate one or more representations of the same soundfield represented by the audio data 19 to obtain a bitstream 27 that includes the representations of the soundfield and the audio metadata 25.

[0043] For instance, to generate the different representations of the soundfield using ambisonic coefficients (which again is one example of the audio data 19), soundfield representation generator 24 may use a coding scheme for ambisonic representations of a soundfield, referred to as Mixed Order Ambisonics (MOA) as discussed in more detail in U.S. application Ser. No. 15/672,058, entitled “MIXED-ORDER AMBISONICS (MOA) AUDIO DATA FOR COMPUTER-MEDIATED REALITY SYSTEMS,” filed Aug. 8, 2017, and published as U.S. patent publication no. 20190007781 on Jan. 3, 2019.

[0044] To generate a particular MOA representation of the soundfield, the soundfield representation generator 24 may generate a partial subset of the full set of ambisonic coefficients. For instance, each MOA representation generated by the soundfield representation generator 24 may provide precision with respect to some areas of the soundfield, but less precision in other areas. In one example, an MOA representation of the soundfield may include eight (8) uncompressed ambisonic coefficients, while the third order ambisonic representation of the same soundfield may include sixteen (16) uncompressed ambisonic coefficients. As such, each MOA representation of the soundfield that is generated as a partial subset of the ambisonic coefficients may be less storage-intensive and less bandwidth intensive (if and when transmitted as part of the bitstream 27 over the illustrated transmission channel) than the corresponding third order ambisonic representation of the same soundfield generated from the ambisonic coefficients.

[0045] Although described with respect to MOA representations, the techniques of this disclosure may also be performed with respect to first-order ambisonic (FOA) representations in which all of the ambisonic coefficients associated with a first order spherical basis function and a zero order spherical basis function are used to represent the soundfield. In other words, rather than represent the soundfield using a partial, non-zero subset of the ambisonic coefficients, the soundfield representation generator 24 may represent the soundfield using all of the ambisonic coefficients for a given order N, resulting in a total of ambisonic coefficients equaling (N+1).sup.2.

[0046] In this respect, the ambisonic audio data (which is another way to refer to the ambisonic coefficients in either MOA representations or full order representation, such as the first-order representation noted above) may include ambisonic coefficients associated with spherical basis functions having an order of one or less (which may be referred to as “1.sup.st order ambisonic audio data”), ambisonic coefficients associated with spherical basis functions having a mixed order and suborder (which may be referred to as the “MOA representation” discussed above), or ambisonic coefficients associated with spherical basis functions having an order greater than one (which is referred to above as the “full order representation”).

[0047] The content capture device 20 or the content editing device 22 may, in some examples, be configured to wirelessly communicate with the soundfield representation generator 24. In some examples, the content capture device 20 or the content editing device 22 may communicate, via one or both of a wireless connection or a wired connection, with the soundfield representation generator 24. Via the connection between the content capture device 20 and the soundfield representation generator 24, the content capture device 20 may provide content in various forms of content, which, for purposes of discussion, are described herein as being portions of the audio data 19.

[0048] In some examples, the content capture device 20 may leverage various aspects of the soundfield representation generator 24 (in terms of hardware or software capabilities of the soundfield representation generator 24). For example, the soundfield representation generator 24 may include dedicated hardware configured to (or specialized software that when executed causes one or more processors to) perform psychoacoustic audio encoding (such as a unified speech and audio coder denoted as “USAC” set forth by the Moving Picture Experts Group (MPEG), the MPEG-H 3D audio coding standard, the MPEG-I Immersive Audio standard, or proprietary standards, such as AptX.TM. (including various versions of AptX such as enhanced AptX–E-AptX, AptX live, AptX stereo, and AptX high definition–AptX-HD), advanced audio coding (AAC), Audio Codec 3 (AC-3), Apple Lossless Audio Codec (ALAC), MPEG-4 Audio Lossless Streaming (ALS), enhanced AC-3, Free Lossless Audio Codec (FLAC), Monkey’s Audio, MPEG-1 Audio Layer II (MP2), MPEG-1 Audio Layer III (MP3), Opus, and Windows Media Audio (WMA).

[0049] The content capture device 20 may not include the psychoacoustic audio encoder dedicated hardware or specialized software and instead may provide audio aspects of the content 21 in a non-psychoacoustic-audio-coded form. The soundfield representation generator 24 may assist in the capture of content 21 by, at least in part, performing psychoacoustic audio encoding with respect to the audio aspects of the content 21.

[0050] The soundfield representation generator 24 may also assist in content capture and transmission by generating one or more bitstreams 27 based, at least in part, on the audio content (e.g., MOA representations and/or third order ambisonic representations) generated from the audio data 19 (in the case where the audio data 19 includes scene-based audio data). The bitstream 27 may represent a compressed version of the audio data 19 and any other different types of the content 21 (such as a compressed version of spherical video data, image data, or text data).

[0051] The soundfield representation generator 24 may generate the bitstream 27 for transmission, as one example, across a transmission channel, which may be a wired or wireless channel, a data storage device, or the like. The bitstream 27 may represent an encoded version of the audio data 19, and may include a primary bitstream and another side bitstream, which may be referred to as side channel information or metadata. In some instances, the bitstream 27 representing the compressed version of the audio data 19 (which again may represent scene-based audio data, object-based audio data, channel-based audio data, or combinations thereof) may conform to bitstreams produced in accordance with the MPEG-H 3D audio coding standard and/or the MPEG-I Immersive Audio standard.

[0052] In some examples of the disclosure, the source device 12 may be configured to generate a plurality of audio streams for transmission to the content consumer device 14. The source device 12 may be configured to generate each of the plurality of audio streams a single content capture device 20 and/or a cluster (e.g., multiple) content capture devices 20. In some use cases, it may be desirable to be able to control which of the plurality of audio streams generated by the source device 12 are available for playback by the content consumer device 14.

[0053] For example, audio from certain capture devices of the content capture devices 20 may contain sensitive information and/or the audio from certain capture devices of the content capture devices 20 may not be meant for exclusive access (e.g., unrestricted access by all users). In some examples, it may be desirable to restrict access to audio from certain capture devices of the content capture devices 20 based on the type of information captured by the content capture device 20 and/or based on the location of physical zone in which the content capture device 20 resides.

[0054] In accordance with example techniques of the disclosure, the source device 12 may further include a controller 31 configured to generate privacy restrictions (e.g., in audio metadata) that indicates privacy restrictions (privacy restriction metadata) in a side channel 33 for one or more of the plurality of audio streams generated by the source device 12. In other examples, controller 31 may embed the privacy restrictions in data within the audio streams. In one example, the privacy restriction indicate if one or more of the plurality of audio streams are restricted or unrestricted. In other examples, the controller 31 may only generate the privacy restriction that indicate if audio streams that restricted. In this example, the content consumer device 14 may infer that audio streams not having associated the privacy restrictions indicting a restricted audio stream are unrestricted. The content consumer device 14 may receive the privacy restrictions and determine one or more audio streams available for decoding and/or playback based on the privacy restrictions. The content consumer device 14 may generate the corresponding soundfields based on the determined one or more audio streams.

[0055] In the example, of FIG. 1A, the controller 31 transmits the privacy restrictions as metadata in side channel 33. In other examples, the controller 31 may transmit the privacy restrictions as metadata in the bitstream 27. In other examples, the controller 31 may embed the privacy restrictions in data in the audio streams in bitstream. For example, the controller 31 may embed the privacy restrictions in a few bits (e.g., the least significant bits) of an audio sample or part of an ambisonic coefficient (e.g., the first 12 or 13 bits could represent the ambisonic coefficient and last 3 or 4 bits could be the privacy restriction). In some examples, the controller 31 need not be a separate physical unit. Rather, the controller 31 may be integrated into the content editing device 22 or the soundfield representation generator 24.

[0056] The content consumer device 14 may be operated by an individual, and may represent a VR client device. Although described with respect to a VR client device, content consumer device 14 may represent other types of devices, such as an augmented reality (AR) client device, a mixed reality (MR) client device (or other XR client device), a standard computer, a headset, headphones, a mobile device (including a so-called smartphone), or any other device capable of tracking head movements and/or general translational movements of the individual operating the content consumer device 14. As shown in the example of FIG. 1A, the content consumer device 14 includes an audio playback system 16A, which may refer to any form of audio playback system capable of rendering the audio data for playback as multi-channel audio content.

[0057] While shown in FIG. 1A as being directly transmitted to the content consumer device 14, the source device 12 may output the bitstream 27 to an intermediate device positioned between the source device 12 and the content consumer device 14. The intermediate device may store the bitstream 27 for later delivery to the content consumer device 14, which may request the bitstream 27. The intermediate device may comprise a file server, a web server, a desktop computer, a laptop computer, a tablet computer, a mobile phone, a smart phone, or any other device capable of storing the bitstream 27 for later retrieval by an audio decoder. The intermediate device may reside in a content delivery network capable of streaming the bitstream 27 (and possibly in conjunction with transmitting a corresponding video data bitstream) to subscribers, such as the content consumer device 14, requesting the bitstream 27.

[0058] Alternatively, the source device 12 may store the bitstream 27 to a storage medium, such as a compact disc, a digital video disc, a high definition video disc or other storage media, most of which are capable of being read by a computer and therefore may be referred to as computer-readable storage media or non-transitory computer-readable storage media. In this context, the transmission channel may refer to the channels by which content (e.g., in the form of one or more bitstreams 27) stored to the mediums are transmitted (and may include retail stores and other store-based delivery mechanism). In any event, the techniques of this disclosure should not therefore be limited in this respect to the example of FIG. 1A.

[0059] As noted above, the content consumer device 14 includes the audio playback system 16A. The audio playback system 16A may represent any system capable of playing back multi-channel audio data. The audio playback system 16A may include a number of different renderers 32. The renderers 32 may each provide for a different form of rendering, where the different forms of rendering may include one or more of the various ways of performing vector-base amplitude panning (VBAP), and/or one or more of the various ways of performing soundfield synthesis. As used herein, “A and/or B” means “A or B”, or both “A and B”.

[0060] The audio playback system 16A may further include an audio decoding device 34. The audio decoding device 34 may represent a device configured to decode bitstream 27 to output audio data 19’ (where the prime notation may denote that the audio data 19’ differs from the audio data 19 due to lossy compression, such as quantization, of the audio data 19). Again, the audio data 19’ may include scene-based audio data that in some examples, may form the full first (or higher) order ambisonic representation or a subset thereof that forms an MOA representation of the same soundfield, decompositions thereof, such as a predominant audio signal, ambient ambisonic coefficients, and the vector based signal described in the MPEG-H 3D Audio Coding Standard, or other forms of scene-based audio data.

[0061] Other forms of scene-based audio data include audio data defined in accordance with an HOA (Higher Order Ambisonic) Transport Format (HTF). More information regarding the HTF can be found in a Technical Specification (TS) by the European Telecommunications Standards Institute (ETSI) entitled “Higher Order Ambisonics (HOA) Transport Format,” ETSI TS 103 589 V1.1.1, dated June 2018 (2018-06), and also in U.S. Patent Publication No. 2019/0918028, entitled “PRIORITY INFORMATION FOR HIGHER ORDER AMBISONIC AUDIO DATA,” filed Dec. 20, 2018. In any event, the audio data 19’ may be similar to a full set or a partial subset of the audio data 19’, but may differ due to lossy operations (e.g., quantization) and/or transmission via the transmission channel.

[0062] The audio data 19’ may include, as an alternative to, or in conjunction with the scene-based audio data, channel-based audio data. The audio data 19’ may include, as an alternative to, or in conjunction with the scene-based audio data, object-based audio data. As such, the audio data 19’ may include any combination of scene-based audio data, object-based audio data, and channel-based audio data.

[0063] The audio renderers 32 of audio playback system 16A may, after audio decoding device 34 has decoded the bitstream 27 to obtain the audio data 19’, render the audio data 19’ to output speaker feeds 35. The speaker feeds 35 may drive one or more speakers (which are not shown in the example of FIG. 1A for ease of illustration purposes). Various audio representations, including scene-based audio data (and possibly channel-based audio data and/or object-based audio data) of a soundfield may be normalized in a number of ways, including N3D, SN3D, FuMa, N2D, or SN2D.

[0064] To select the appropriate renderer or, in some instances, generate an appropriate renderer, the audio playback system 16A may obtain speaker information 37 indicative of a number of speakers (e.g., loudspeakers or headphone speakers) and/or a spatial geometry of the speakers. In some instances, the audio playback system 16A may obtain the speaker information 37 using a reference microphone and may drive the speakers (which may refer to the output of electrical signals to cause the transducer to vibrate) in such a manner as to dynamically determine the speaker information 37. In other instances, or in conjunction with the dynamic determination of the speaker information 37, the audio playback system 16A may prompt a user to interface with the audio playback system 16A and input the speaker information 37.

[0065] The audio playback system 16A may select one of the audio renderers 32 based on the speaker information 37. In some instances, the audio playback system 16A may, when none of the audio renderers 32 are within some threshold similarity measure (in terms of the speaker geometry) to the speaker geometry specified in the speaker information 37, generate the one of audio renderers 32 based on the speaker information 37. The audio playback system 16A may, in some instances, generate one of the audio renderers 32 based on the speaker information 37 without first attempting to select an existing one of the audio renderers 32.

[0066] When outputting the speaker feeds 35 to headphones, the audio playback system 16A may utilize one of the renderers 32 that provides for binaural rendering using head-related transfer functions (HRTF) or other functions capable of rendering to left and right speaker feeds 35 for headphone speaker playback, such as binaural room impulse response renderers. The terms “speakers” or “transducer” may generally refer to any speaker, including loudspeakers, headphone speakers, bone-conducting speakers, earbud speakers, wireless headphone speakers, etc. One or more speakers may then playback the rendered speaker feeds 35 to reproduce a soundfield.

[0067] Although described as rendering the speaker feeds 35 from the audio data 19’, reference to rendering of the speaker feeds (e.g., audio data 19’) may refer to other types of rendering, such as rendering incorporated directly into the decoding of the audio data from the speaker feeds 35 from the bitstream 27. An example of the alternative rendering can be found in Annex G of the MPEG-H 3D Audio standard, where rendering occurs during the predominant signal formulation and the background signal formation prior to composition of the soundfield. As such, reference to rendering of the audio data 19’ should be understood to refer to both rendering of the actual audio data 19’ or decompositions or representations thereof of the audio data 19’ (such as the above noted predominant audio signal, the ambient ambisonic coefficients, and/or the vector-based signal–which may also be referred to as a V-vector or as a multi-dimensional ambisonic spatial vector).

[0068] The audio playback system 16A may also adapt the audio renderers 32 based on tracking information 41. That is, the audio playback system 16A may interface with a tracking device 40 configured to track head movements and possibly translational movements of a user of the VR device. The tracking device 40 may represent one or more sensors (e.g., a camera–including a depth camera, a gyroscope, a magnetometer, an accelerometer, light emitting diodes–LEDs, etc.) configured to track the head movements and possibly translation movements of a user of the VR device. The audio playback system 16A may adapt, based on the tracking information 41, the audio renderers 32 such that the speaker feeds 35 reflect changes in the head and possibly translational movements of the user to correct reproduce the soundfield that is responsive to such movements.

[0069] As described above, the content consumer device 14 may represent a VR device in which a human wearable display (which may also be referred to a “head mounted display”) is mounted in front of the eyes of the user operating the VR device. FIG. 2 is a diagram illustrating an example of a VR device 1100 worn by a user 1102. The VR device 1100 is coupled to, or otherwise includes, headphones 1104, which may reproduce a soundfield represented by the audio data 19’ through playback of the speaker feeds 35. The speaker feeds 35 may represent an analog or digital signal capable of causing a membrane within the transducers of headphones 1104 to vibrate at various frequencies, where such process is commonly referred to as driving the headphones 1104.

[0070] Video, audio, and other sensory data may play important roles in the VR experience. To participate in a VR experience, the user 1102 may wear the VR device 1100 (which may also be referred to as a VR headset 1100) or other wearable electronic device. The VR client device (such as the VR headset 1100) may include a tracking device (e.g., the tracking device 40) that is configured to track head movement of the user 1102, and adapt the video data shown via the VR headset 1100 to account for the head movements, providing an immersive experience in which the user 1102 may experience a displayed world shown in the video data in visual three dimensions. The displayed world may refer to a virtual world (in which all of the world is simulated), an augmented world (in which portions of the world are augmented by virtual objects), or a physical world (in which a real world image is virtually navigated).

[0071] While VR (and other forms of XR, AR and/or MR) may allow the user 1102 to reside in the virtual world visually, often the VR headset 1100 may lack the capability to place the user in the displayed world audibly. In other words, the VR system (which may include a computer responsible for rendering the video data and audio data–that is not shown in the example of FIG. 2 for ease of illustration purposes, and the VR headset 1100) may be unable to support full three-dimension immersion audibly (and in some instances realistically in a manner that reflects the displayed scene presented to the user via the VR headset 1100).

[0072] While described in this disclosure with respect to the VR device, various aspects of the techniques may be performed in the context of other devices, such as a mobile device. In this instance, the mobile device (such as a so-called smartphone) may present the displayed world via a screen, which may be mounted to the head of the user 1102 or viewed as would be done when normally using the mobile device. As such, any information on the screen can be part of the mobile device. The mobile device may be able to provide tracking information 41 and thereby allow for both a VR experience (when head mounted) and a normal experience to view the displayed world, where the normal experience may still allow the user to view the displayed world proving a VR-lite-type experience (e.g., holding up the device and rotating or translating the device to view different portions of the displayed world).

[0073] In any event, returning to the VR device context, the audio aspects of VR have been classified into three separate categories of immersion. The first category provides the lowest level of immersion, and is referred to as three degrees of freedom (3DOF). 3DOF refers to audio rendering that accounts for movement of the head in the three degrees of freedom (yaw, pitch, and roll), thereby allowing the user to freely look around in any direction. 3DOF, however, cannot account for translational head movements in which the head is not centered on the optical and acoustical center of the soundfield.

[0074] The second category, referred to 3DOF plus (3DOF+), provides for the three degrees of freedom (yaw, pitch, and roll) in addition to limited spatial translational movements due to the head movements away from the optical center and acoustical center within the soundfield. 3DOF+ may provide support for perceptual effects such as motion parallax, which may strengthen the sense of immersion.

[0075] The third category, referred to as six degrees of freedom (6DOF), renders audio data in a manner that accounts for the three degrees of freedom in term of head movements (yaw, pitch, and roll) but also accounts for translation of the user in space (x, y, and z translations). The spatial translations may be induced by sensors tracking the location of the user in the physical world or by way of an input controller.

[0076] 3DOF rendering is the current state of the art for the audio aspects of VR. As such, the audio aspects of VR are less immersive than the video aspects, thereby potentially reducing the overall immersion experienced by the user. However, VR is rapidly transitioning and may develop quickly to supporting both 3DOF+ and 6DOF that may expose opportunities for additional use cases.

[0077] For example, interactive gaming application may utilize 6DOF to facilitate fully immersive gaming in which the users themselves move within the VR world and may interact with virtual objects by walking over to the virtual objects. Furthermore, an interactive live streaming application may utilize 6DOF to allow VR client devices to experience a live stream of a concert or sporting event as if present at the concert themselves, allowing the users to move within the concert or sporting event.

[0078] There are a number of difficulties associated with these use cases. In the instance of fully immersive gaming, latency may need to remain low to enable gameplay that does not result in nausea or motion sickness. Moreover, from an audio perspective, latency in audio playback that results in loss of synchronization with video data may reduce the immersion. Furthermore, for certain types of gaming applications, spatial accuracy may be important to allow for accurate responses, including with respect to how sound is perceived by the users as that allows users to anticipate actions that are not currently in view.

[0079] In the context of live streaming applications, a large number of source devices 12 may stream content 21, where the source devices 12 may have widely different capabilities. For example, one source device may be a smartphone with a digital fixed-lens camera and one or more microphones, while another source device may be production level television equipment capable of obtaining video of a much higher resolution and quality than the smartphone. However, all of the source devices, in the context of the live streaming applications, may offer streams of varying quality from which the VR device may attempt to select an appropriate one to provide an intended experience.

[0080] Moreover, similar to the gaming applications, latency in audio data such that loss of synchronization occurs with the video data may result in less immersion. Moreover, spatial accuracy may also be important such that the users may better understand the context or location of different audio sources. Further, when users are live streaming using cameras and microphones, privacy may become an issue, as users may not want to live streams fully available to the public.

[0081] In the context of streaming application (live or recorded), there may be a large number of audio streams associated with varying levels of quality and/or content. The audio streams may represent any type of audio data, including scene-based audio data (e.g., ambisonic audio data, including FOA audio data, MOA audio data and/or HOA audio data), channel-based audio data, and object-based audio data. Selecting only one of a potentially large number of audio streams from which to recreate a soundfield may not provide an experience that ensures an adequate level of immersion. However, selecting multiple audio streams may create distractions due to different spatial localization between the multiple audio streams, thereby potentially reducing immersion.

[0082] In accordance with example techniques described in this disclosure, the audio decoding device 34 may adaptively select between audio streams available via the bitstream 27 (which are represented by the bitstream 27 and hence the bitstream 27 may be referred to as “audio streams 27”). The audio decoding device 34 may select between different audio streams of the audio streams 27 based on capture location information (CLI) 45A included as metadata accompanying the audio streams 27, where the capture location information may define capture coordinates in the displayed world for the microphones that capture the respective audio streams 27. The CLI 45A may be representative of a capture location in a displayed world at which the corresponding one of the audio streams 27 was captured. The audio decoding device 34 may select, based on the CLI 45A, a subset of the audio streams 27, where the subset of the audio streams 27 excludes at least one of the audio streams 27. The audio decoding device 34 may output the subset of audio streams 27 as audio data 19’ (which may also be referred to as “audio streams 19’”). The adaptive audio stream selection techniques of this disclosure may be used together with any of the privacy restriction techniques described below.

[0083] In addition, the audio decoding device 34 may obtain the tracking information 41, which the content consumer device 14 may translate into virtual location information (VLI) 45B. The VLI 45B may represent a virtual location of the content consumer device 14 in the displayed world, which may be defined as one or more device coordinates in the displayed world. The content consumer device 15 may provide the VLI 45B to the audio decoding device 34. The audio decoding device 34 may then select, based on the CLI 45A and the VLI 45B, the audio streams 19’ from the audio streams 27. The audio playback system 16A may then reproduce, based on the audio streams 19’, the corresponding soundfields.

[0084] In this respect, the audio decoding device 34 may adaptively select a subset of the audio streams 27 to obtain the audio streams 19’ that may result in a more immersive experience (compared to selecting a single audio stream or all of the audio streams 19’). As such, various aspects of the techniques described in this disclosure may improve operation of the audio decoding device 34 (and the audio playback system 16A and the content consumer device 14) itself by possibly enabling the audio decoding device 34 to better spatialize sound sources within the soundfield and thereby improve immersion.

[0085] In operation, the audio decoding device 34 may interface with one or more source devices 12 to determine the CLI 45A for each of the audio streams 27. As shown in the example of FIG. 1A, the audio decoding device 34 may include a stream selection unit 44, which may represent a unit configured to perform various aspects of the audio stream selection techniques described in this disclosure.

[0086] The stream selection unit 44 may generate, based on the CLI 45A, a constellation map (CM) 47. The CM 47 may define the CLI 45A for each of the audio streams 27. The stream selection unit 44 may also perform an energy analysis with respect to each of the audio streams 27 to determine an energy map for each of the audio streams 27, storing the energy map along with the CLI 45A in the CM 47. The energy maps may jointly define an energy of a common soundfield represented by the audio streams 27.

[0087] The stream selection unit 44 may next determine a distance between the virtual location represented by the VLI 45B and the capture location represented by the CLI 45A associated with at least one and possible each of the audio streams 27. The stream selection unit 44 may then select, based on the at least one and possibly each of the distance(s), the audio streams 19’ from the audio streams 27 as discussed in more detail below with respect to FIGS. 3A-3D.

[0088] Further, in some examples, the stream selection unit 44 may also select, based on the energy maps stored to the CM 47, the CLI 45A, and the VLI 45B (jointly where the CLI 45A and the VLI 45B are presented in the form of the above noted distances, which may also be referred to as “relative distances”), the audio streams 19’ from the audio streams 27. For example, the stream selection unit 44 may analyze the energy maps presented in the CM 47 to determine an audio source location (ASL) 49 of an audio source in the common soundfield emitting sound that is captured by microphones (such as the microphone 18) and represented by the audio streams 27. The stream selection unit 44 may then determine, based on CLI 45A, the VLI 45B, and the ASL 49, the audio streams 19’ from the audio streams 27. More information regarding how the stream selection unit 44 may select the streams is discussed below with respect to FIGS. 3A-3D.

[0089] Furthermore, in accordance with other techniques of this disclosure, the content consumer device 14 may be configured to determine one or more audio streams from ap plurality of audio streams based on privacy restrictions. For example, the content consumer device 14 may be configured to receive one or more audio streams from audio elements represented in an acoustic environment that comprises one or more sub-acoustic spaces, each of the one or more audio streams representative of a respective soundfield, determine unrestricted audio streams of the one or more audio streams based on privacy restrictions associated with the one or more audio streams, determine restricted audio streams of the one or more audio streams based on the privacy restrictions associated with the one or more audio streams, generate the corresponding respective soundfields of the unrestricted audio streams, and restrict playback of the corresponding respective soundfields of the restricted audio streams.

[0090] FIG. 1B is a block diagram illustrating another example system 50 configured to perform various aspects of the techniques described in this disclosure. The system 50 is similar to the system 10 shown in FIG. 1A, except that the audio renderers 32 shown in FIG. 1A are replaced with a binaural renderer 42 capable of performing binaural rendering using one or more head-related transfer functions HRTFs or the other functions capable of rendering to left and right speaker feeds 43.

[0091] The audio playback system 16B may output the left and right speaker feeds 43 to headphones 1104, which may represent another example of a wearable device and which may be coupled to additional wearable devices to facilitate reproduction of the soundfield, such as a watch, the VR headset noted above, smart glasses, smart clothing, smart rings, smart bracelets or any other types of smart jewelry (including smart necklaces), and the like. The headphones 1104 may couple wirelessly or via wired connection to the additional wearable devices.

[0092] Additionally, the headphones 1104 may couple to the audio playback system 16B via a wired connection (such as a standard 3.5 mm audio jack, a universal system bus (USB) connection, an optical audio jack, or other forms of wired connection) or wirelessly (such as by way of a Bluetooth.TM. connection, a wireless network connection, and the like). The headphones 1104 may recreate, based on the left and right speaker feeds 43, the soundfield represented by the audio data 19’. The headphones 1104 may include a left headphone speaker and a right headphone speaker which are powered (or, in other words, driven) by the corresponding left and right speaker feeds 43.

[0093] FIGS. 3A-3D are diagrams illustrating, in more detail, example operation of the stream selection unit shown in the example of FIG. 1A. As shown in the example of FIG. 3A, the stream selection unit 44 may determine that the VLI 45B indicates that the content consumer device 14 (shown as the VR device 1100) is at virtual location 300A.

[0094] The stream selection unit 44 may next determine the CLI45A for one or more of audio elements 302A-302J (which may represent not just microphones, such as the microphone 18 shown in FIG. 1A, but other types of capture devices, including arrays of microphones, other XR devices, synthetic audio sources, mobile phones–including so-called smartphones–and the like).

[0095] As described above, the stream selection unit 44 may obtain the audio streams 27. The stream selection unit 44 may interface with audio elements 302A-302J to obtain the audio streams 27. In some examples, the stream selection unit 44 may interact with an interface (such as a modem, receiver, a transmitter and/or a transceiver) to obtain the audio streams 27 in accordance with a fifth generation (5G) cellular standard, WiFi, a personal area network (PAN), such as Bluetooth.TM., or some other open-source, proprietary or standardized communication protocol. Wireless communication of the audio streams is denoted as a lightning bolt in the examples of FIGS. 3A-3D, where the selected audio stream 19’ is shown as being communication from the selected one or more of the audio elements 302 to the VR device 1100.

[0096] In any event, the stream selection unit 44 may next obtain energy maps in the manner described above, analyzing the energy maps to determine the audio source location 304, which may represent one example of the ASL 49 shown in the example of FIG. 1A. The energy maps may denote audio source location 304 as the energy at the audio source location 304 may be higher than the surrounding area. Given that each of the energy maps may denote this higher energy, the stream selection unit 44 may triangulate, based on the higher energy in the energy maps, the audio source location 304.

[0097] Next, the stream selection unit 44 may determine an audio source distance 306A as a distance between the audio source location 304 and the virtual location 300A of the VR device 1100. The stream selection unit 44 may compare the audio source distance 306A to an audio source distance threshold. The stream selection unit 44 may, in some examples, derive the audio source distance threshold based on the energy of the audio source 308. That is, when the audio source 308 has a higher energy (or, in other words, when the audio source 308 is louder), the stream selection unit 44 may increase the audio source distance threshold. When the audio source 308 has a lower energy (or, in other words, when the audio source 308 is quieter), the stream selection unit 44 may decrease the audio source distance threshold. In other examples, the stream selection unit 44 may obtain a statically defined audio source distance threshold, which may be statically defined or specified by the user 1102.

[0098] In any event, the stream selection unit 44 may select, when the audio source distance 306A is greater than the audio source distance threshold (which is assumed in this example for purposes of illustration), a single audio stream of the audio streams 27 captured by the audio elements 302A-302J (“audio elements 302”) (i.e., the audio stream captured by the audio element 302A in the example of FIG. 3A). The stream selection unit 44 may output the corresponding one of the audio streams 27, which the audio decoding device 34 may decode and output as the audio stream 19’.

[0099] Assuming that the user moves from the virtual location 300A to the virtual location 300B, the stream selection unit 44 may determine an audio source distance 306B as a distance between the audio source location 304 and the virtual location 300B. In some examples, the stream selection unit 44 may only update after some configurable release time, which may refer to a time until the receiver region increases after the listener stops moving.

[0100] In any event, the stream selection unit 44 may again compare the audio source distance 306B to the audio source distance threshold. The stream selection unit 44 may select, when the audio source distance 306 is less than or equal than the audio source distance threshold (which is assumed in this example for purposes of illustration), multiple audio streams of the audio streams 27 captured by the audio elements 302A-302J (“audio elements 302”) (i.e., the audio stream captured by the audio elements 302F-302J in the example of FIG. 3A). The stream selection unit 44 may output the corresponding one of the audio streams 27, which the audio decoding device 34 may decode and output as the audio stream 19’.

[0101] The stream selection unit 44 may also determine a proximity distance between the virtual location 300A and one or more (and possibly each) of the capture locations represented by the CLI 45A to obtain one or more proximity distances. The stream selection unit 44 may then compare the one or more proximity distances to a threshold proximity distance. The stream selection unit 44 may select, when the one or more proximity distances are greater than the threshold proximity distance, a smaller number of the audio streams 27 compared to when the proximity distance is less than or equal to the threshold proximity distance to obtain the audio streams 19’. However, the stream selection unit 44 may select, when the one or more of the proximity distances are less than or equal to the threshold proximity distance, a larger number of the audio streams 27 compared to when the proximity distance is less than or equal to the threshold proximity distance to obtain the audio streams 19’.

[0102] In other words, the stream selection unit 44 may attempt to select those of the audio streams 27 such that the audio streams 19’ are most closely aligned to the virtual location 300B and surround the virtual location 300B. The proximity distance threshold may define such a threshold, which the user 1100 may set or the stream selection unit 44 may again determine dynamically based on a quality of the audio elements 302F-302J, the gain or loudness of the audio source 308, tracking information 41 (e.g., to determine whether the user is facing the audio source 308), or any other factors.

[0103] In this respect, the stream selection unit 44 may increase audio spatialization accuracy when at the listener is at the location 300B. Furthermore, when at the location 300A, the stream selection unit 44 may reduce a bitrate, as only the audio stream captured by audio element 302A is used to reproduce the soundfield rather than multiple audio streams captured by audio elements 302B-302J.

[0104] Referring next to the example of FIG. 3B, the stream selection unit 44 may determine that the audio stream captured by the audio element 302A is corrupted, noisy, or unavailable. The stream selection unit 44 may remove the audio stream from the CM 47 and reiterate through the audio streams 27 in accordance with the techniques described in more detail above to select a single one of the audio streams 27 (i.e., the audio stream captured by the audio element 302B in the example of FIG. 3B) given that the audio source distance 306A is greater than the audio source distance threshold.

[0105] Referring next to the example of FIG. 3C, the stream selection unit 44 may obtain a new audio stream (generated by the audio element 302K) and corresponding new audio metadata that includes CLI 45A. The stream selection unit 44 may add the new audio streams to the CM 47 representative of the audio streams 27. The stream selection unit 44 may then reiterate through the audio streams 27 in accordance with the techniques described in more detail above to select a single one of the audio streams 27 (i.e., the audio stream captured by the audio element 302B in the example of FIG. 3C) given that the audio source distance 306A is greater than the audio source distance threshold.

[0106] In the example of FIG. 3D, the audio elements 302 are replaced with specific devices 320A-320J (“devices 320”), where device 320A represents a dedicated microphone 320A, while devices 320B, 320C, 320D, 320G, 320H, and 320J represent smartphones 320. The devices 320E, 320F, and 320I may represent VR devices 320.

[0107] Each of devices 320 may include the audio elements 302, which capture audio streams 27 that are selected in accordance with various aspects of the stream selection techniques described in this disclosure.

[0108] FIGS. 4A-4E are diagrams illustrating example operations of privacy restrictions performed by the source device and/or content consumer device shown in the examples of FIGS. 1A and 1B. As described above, in some use cases, it may be desirable to be able to control which of the plurality of audio streams generated by the source device 12 are available for playback by the content consumer device 14.

[0109] For example, audio from certain capture devices of the content capture devices 20 may contain sensitive information and/or the audio from certain capture devices of the content capture devices 20 (FIG. 1A and FIG. 1B) and/or the audio elements 302 (FIGS. 3A-3D) may not be meant for exclusive access (e.g., unrestricted access by all users). It may be desirable to restrict access to audio from certain capture devices of the content capture devices 20 and/or the audio elements 302 based on the type of information captured/generated and/or based on the location of physical zone in which the content capture device 20 and/or the audio elements 302 resides.

[0110] As shown in the example of FIG. 4A, the stream selection unit 44 may determine that the VLI 45B indicates that the content consumer device 14 (shown as the VR device 400) is at virtual location 401. The VR device 400 may be a listener on a 6DoF playback system. The stream selection unit 44 may next determine the CLI45A for one or more of audio elements 402A-402H (which may represent not just microphones, such as the microphone 18 shown in FIG. 1A, but other types of capture and/or audio generation devices, including microphone arrays, clusters of microphones, synthetic audio sources, other XR devices, mobile phones–including so-called smartphones–and the like).

[0111] As described above, the stream selection unit 44 may obtain the audio streams 27. The stream selection unit 44 may interface with audio elements 402A-402H and/or with source device 12 to obtain the audio streams 27. In some examples, the stream selection unit 44 may interact with an interface (such as a modem, receiver, a transmitter and/or a transceiver) to obtain the audio streams 27 in accordance with a fifth generation (5G) cellular standard, a personal area network (PAN), such as Bluetooth.TM., or some other open-source, proprietary or standardized communication protocol. Wireless communication of the audio streams is denoted as a lightning bolt in the examples of FIG. 4A, where the selected audio stream 19’ is shown as being communication from the selected one or more of the audio elements 402 and/or source device 12 to the VR device 400.

[0112] In the example of FIG. 4A, the VR device 400 is at location 401, which is in the vicinity of an audio source 409. Using the techniques described above, and in greater detail below, the VR device 400 may use energy maps to determine that audio source 409 is at the location 401. FIG. 4A shows the audio elements 402D-402H at the location 401. The audio elements 402A-402C may not be in the vicinity of the VR device 400.

[0113] Audio elements 402A-402F are captured and/or generated in an acoustic environment. As used herein, an acoustic environment is represented as either an indoor environment or an outdoor environment, or both an indoor environment and an outdoor environment. The acoustic environment may include one or more sub-acoustic spaces that may include various acoustic elements. A sub-acoustic space may, for example, be a room, or an area within a room or building, the cabin of a vehicle, a classroom, an area within a classroom, or any subset of any type of acoustic space. An example of an outdoor environment could include a car, buildings, walls, a forest, etc. An acoustic space may be an example of an acoustic environment and may be an indoor space or an outdoor space. As used herein, an audio element may be a sound captured by a microphone (e.g., directly captured from near-filed sources or reflections from far-field sources whether real or synthetic), a sound captured by an array of microphones, a soundfield previously synthesized, a mono sound synthesized from text to speech, and/or a reflection of a virtual sound from an object in the acoustic environment.

[0114] In one example of the disclosure, the source device 12 may be configured to generate privacy restrictions for the plurality of audio streams. For example, as shown in FIG. 4A, the source device 12 may be configured to generate privacy restrictions that indicate that the audio stream associated with the audio element 402H is restricted for the user of the VR device 400 (or any other content consumer device). In one example, source device 12 transmits the privacy restrictions as metadata in side channel 33. In other examples, the source device 12 may transmit the privacy restrictions as metadata in the bitstream 27. In other examples, the source device 12 may embed the privacy restrictions in data in the audio streams in bitstream (e.g., in audio stream associated with audio element 402H). For example, the source device 12 may embed the privacy restrictions in a few bits (e.g., the least significant bits) of an audio sample or part of an ambisonic coefficient (e.g., the first 12 or 13 bits could represent the ambisonic coefficient and last 3 or 4 bits could be the privacy restriction). The source device 12 may transmit the privacy restrictions to the VR device 400 (or any other content consumer device).

[0115] The VR device 400 may be configured to receive the plurality of audio streams and corresponding privacy restrictions and store them in a memory. Each of the audio streams is representative of a soundfield, and the privacy restrictions include restrictions for one or more of the plurality of audio streams. The VR device 400 may be configured determine one or more audio streams based on the privacy restrictions. For example, the VR device 400 may be configured to determine audio streams that are able to be played back based on the privacy restrictions. The VR device 400 may then generate the corresponding soundfields based on the one or more audio streams. Likewise, the VR device 400 may be configured to determine one or more restricted audio streams (e.g., the audio stream associated with the audio element 402H) from the audio metadata based on the privacy restrictions, and not generate the corresponding soundfields for the one or more restricted audio streams.

[0116] Accordingly, in one example of the disclosure the VR device 400 may be configured to receive one or more audio streams from the audio elements 402 represented in an acoustic environment that comprises one or more sub-acoustic spaces. In this example, each of the one or more audio streams is representative of a respective soundfield. The audio elements 402 may be any source of audio data, including one or more of a single microphone, an array of microphones, a mobile device, or a synthesized audio source.

[0117] The VR device 400 may be further configured to determine unrestricted audio streams (e.g., audio streams from audio elements 402A-G) of the one or more audio streams based on privacy restrictions associated with the one or more audio streams, and determine restricted audio streams (e.g., an audio stream from audio element 402H) of the one or more audio streams based on the privacy restrictions associated with the one or more audio streams. In one example, the privacy restriction associated with the one or more audio streams are embedded in the one or more audio streams. In this example, the VR device 400 may be configured to extract the privacy restrictions from the one or more audio streams. In another example, the VR device 400 may be configured to receive metadata that includes the privacy restrictions associated with the one or more audio streams.

[0118] The VR device 400 may then generate the corresponding respective soundfields of the unrestricted audio streams, and restrict playback of the corresponding respective soundfields of the restricted audio streams. In one example, to restrict playback of the corresponding respective soundfields of the restricted audio streams, the VR device 400 is further configured to toggle off the restricted audio streams. In another example, to restrict playback of the corresponding respective soundfields of the restricted audio streams, the VR device 400 is further configured to mask the restricted audio streams. In another example, to restrict playback of the corresponding respective soundfields of the restricted audio streams, the VR device 400 is further configured to null the restricted audio streams. In another example, to restrict playback of the corresponding respective soundfields of the restricted audio streams, the VR device 400 is further configured to apply an acoustic occluder to the restricted audio streams.

[0119] FIG. 4B is a block diagram illustrating the operation of the controller 31 in one example of the disclosure. In one example, the controller 31 may be implemented as a processor 712. The processor 712 is described in more detail below with reference to FIG. 7. As described above with reference to FIG. 1A, the source device 12 may capture and/or generate audio data using the content capture device 20. The content capture device 20 may capture and/or generate audio data from the audio elements 402. The audio elements 402 may include static sources, such as static single microphones or clusters of microphones. The audio elements 402 may be live sources. Alternatively or in addition, the audio elements 402 may include dynamic audio sources (e.g., dynamic in terms of use and/or position), such as mobile phones. In some examples, dynamic audio sources may be synthetic audio sources. The audio streams may come from single, physically spaced audio sources, or from clusters of audio sources in a single physical location.

[0120] In some examples, it may be beneficial to group audio sources (e.g., real or synthetic audio elements) that are located physically close to each other into a cluster, as each individual audio source in a physically co-located cluster may sense some or all of the audio as each of the other audio sources in the cluster. As such, in some examples of the disclosure, the controller 31 may be configured to toggle audio streams from a cluster of audio elements (marked C in FIG. 4B), as well to toggle audio streams from individual audio elements (marked R in FIG. 4B). In this context, toggle may refer to marking an audio stream or groups of audio streams as unrestricted (e.g., able to be decoded and/or played) or restricted (e.g., not able to be decoded and/or played). A privacy toggle of on (e.g., restricted) indicates the VR device 400 should mute and/or generally not decode or playback the audio stream. A privacy toggle of off (e.g., unrestricted or common access) indicates that any user may decode and playback the audio stream. In this way, the audio engineer or the content creator may grant exclusive access to certain audio sources for non-restricted users or based on hierarchical privacy setting ranks.

[0121] As shown in FIG. 4B, the controller 31 may be configured to receive and/or access the plurality of audio streams captured by the content capture device 20. The controller 31 may be configured to check if there are any privacy settings associated with the audio streams. That is, the controller 31 may be configured to determine one or more unrestricted audio streams and one or more restricted audio streams from the plurality of audio streams.

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