Camera control data for a virtual camera in a virtual interactive scene defined by streamed media data

Abstract

An exemplary device for retrieving media data includes a memory configured to store the media data and one or more processors implemented with circuitry and configured to execute a presentation engine, the presentation engine being configured to: receive streamed media data representing a virtual three-dimensional scene including at least one virtual solid object; receive camera control data for the three-dimensional scene, the camera control data including data defining constraints for preventing a virtual camera from passing through the at least one virtual solid object; receive camera movement data from a user requesting that the virtual camera move through the at least one virtual solid object; and, in response to the camera movement data, use the camera control data to prevent the virtual camera from passing through the at least one virtual solid object.

Description

[Technical field]

[0001] This application claims priority to U.S. Patent Application No. 17 / 654,020, filed March 8, 2022, and U.S. Provisional Application No. 63 / 159,379, filed March 10, 2021, the entire contents of each of which are incorporated herein by reference. U.S. Patent Application No. 17 / 654,020, filed March 8, 2022, claims the benefit of U.S. Provisional Application No. 63 / 159,379, filed March 10, 2021.

[0002] FIELD This disclosure relates to the storage and transmission of encoded video data. [Background technology]

[0003] Digital video capabilities may be incorporated into a wide range of devices, including digital televisions, digital direct broadcast systems, wireless broadcast systems, personal digital assistants (PDAs), laptop or desktop computers, digital cameras, digital recording devices, digital media players, video game devices, video game consoles, cellular or satellite radiotelephones, video conferencing devices, etc. Digital video devices implement video compression techniques, such as those described in standards set forth by MPEG-2, MPEG-4, ITU-T H.263 or ITU-T H.264 / MPEG-4, Part 10, Advanced Video Coding (AVC), ITU-T H.265 (also known as High Efficiency Video Coding (HEVC)), and extensions to such standards, in order to more efficiently transmit and receive digital video information.

[0004] Video compression techniques perform spatial and / or temporal prediction to reduce or remove redundancy inherent in video sequences. For block-based video coding, a video frame or slice may be partitioned into macroblocks. Each macroblock may be further partitioned. Macroblocks in an intra-coded (I) frame or slice are coded using spatial prediction with respect to neighboring macroblocks. Macroblocks in an inter-coded (P or B) frame or slice may use spatial prediction with respect to neighboring macroblocks in the same frame or slice or temporal prediction with respect to other reference frames.

[0005] After the video data is encoded, it may be packetized for transmission or storage and assembled into a video file that conforms to any of a variety of standards, such as the International Organization for Standardization (ISO) Base Media File Format, such as AVC, and its extensions. [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] R. Fielding et al., RFC 2616, "Hypertext Transfer Protocol-HTTP / 1.1", Network Working Group, IETF, June 1999. [Non-Patent Document 2] T. Paila et al., “FLUTE-File Delivery over Unidirectional Transport”, Network Working Group, RFC 6726, November 2012 Summary of the Invention [Means for solving the problem]

[0007] Generally, this disclosure describes techniques related to streaming interactive media data. Such interactive media data may be, for example, virtual reality, augmented reality, or other such interactive content, e.g., other three-dimensional video content. Recent MPEG scene description elements include support for timed media in glTF2.0. The Media Access Function (MAF) provides an application programming interface (API) to a presentation engine through which the presentation engine may request timed media. A fetching unit running the MAF may process the fetched timed media data and pass the processed media data to the presentation engine in a desired format through a circular buffer. Current MPEG scene descriptions allow users to consume scene media data with six degrees of freedom (6DoF). Thus, users can generally move freely in a 3D scene (e.g., through walls displayed in the 3D scene). However, content creators may want to impose limits on viewer movement to some areas, for example, to prevent movement through walls or other objects displayed. This disclosure describes techniques for imposing such limits, which can improve the experience because by preventing a user from walking through obstacles in the virtual world, the user's experience can be made more realistic.

[0008] In one example, a method of retrieving media data includes the steps of receiving, by a presentation engine, streamed media data representing a virtual three-dimensional scene including at least one virtual solid object; receiving, by the presentation engine, camera control data for the three-dimensional scene, the camera control data including data defining constraints for preventing a virtual camera from passing through the at least one virtual solid object; receiving, by the presentation engine, camera movement data from a user requesting that the virtual camera move through the at least one virtual solid object; and in response to the camera movement data, using the camera control data, preventing, by the presentation engine, the virtual camera from passing through the at least one virtual solid object.

[0009] In another example, a device for retrieving media data includes a memory configured to store the media data and one or more processors implemented with circuitry and configured to execute a presentation engine, the presentation engine configured to: receive streamed media data representing a virtual three-dimensional scene including at least one virtual solid object; receive camera control data for the three-dimensional scene, the camera control data including data defining constraints for preventing a virtual camera from passing through the at least one virtual solid object; receive camera movement data from a user requesting that the virtual camera move through the at least one virtual solid object; and, in response to the camera movement data, use the camera control data to prevent the virtual camera from passing through the at least one virtual solid object.

[0010] In another example, a computer-readable storage medium having instructions stored thereon that, when executed, cause a processor of a client device to receive streamed media data representing a virtual three-dimensional scene including at least one virtual solid object; receive camera control data for the three-dimensional scene, the camera control data including data defining constraints for preventing a virtual camera from passing through the at least one virtual solid object; receive camera movement data from a user requesting that the virtual camera move through the at least one virtual solid object; and, in response to the camera movement data, use the camera control data to prevent the virtual camera from passing through the at least one virtual solid object.

[0011] In another example, a device for retrieving media data includes means for receiving streamed media data representing a virtual three-dimensional scene including at least one virtual solid object; means for receiving camera control data for the three-dimensional scene, the camera control data including data defining constraints for preventing a virtual camera from passing through the at least one virtual solid object; means for receiving camera movement data from a user requesting that the virtual camera move through the at least one virtual solid object; and means for using the camera control data to prevent the virtual camera from passing through the at least one virtual solid object, in response to the camera movement data.

[0012] In another example, a method of retrieving media data includes receiving, by a presentation engine, streamed media data representing a virtual three-dimensional scene including at least one virtual solid object; receiving, by the presentation engine, object collision data representing a boundary of the at least one virtual solid object; receiving, by the presentation engine, camera movement data from a user requesting that a virtual camera move through the at least one virtual solid object; and, in response to the camera movement data, preventing, by the presentation engine, the virtual camera from passing through the at least one virtual solid object using the object collision data.

[0013] In another example, a device for retrieving media data includes a memory configured to store the media data and one or more processors implemented with circuitry and configured to execute a presentation engine, the presentation engine configured to receive streamed media data representing a virtual three-dimensional scene including at least one virtual solid object, receive object collision data representing boundaries of the at least one virtual solid object, receive camera movement data from a user requesting that a virtual camera move through the at least one virtual solid object, and in response to the camera movement data, use the object collision data to prevent the virtual camera from passing through the at least one virtual solid object.

[0014] In another example, a computer-readable storage medium storing instructions that, when executed, cause a processor of a client device to receive streamed media data representing a virtual three-dimensional scene including at least one virtual solid object, receive object collision data representing a boundary of the at least one virtual solid object, receive camera movement data from a user requesting that a virtual camera move through the at least one virtual solid object, and, in response to the camera movement data, use the object collision data to prevent the virtual camera from passing through the at least one virtual solid object.

[0015] In another example, a device for retrieving media data includes means for receiving streamed media data representing a virtual three-dimensional scene including at least one virtual solid object, means for receiving object collision data representing a boundary of the at least one virtual solid object, means for receiving camera movement data from a user requesting that a virtual camera move through the at least one virtual solid object, and means for using the object collision data to prevent the virtual camera from passing through the at least one virtual solid object, in response to the camera movement data.

[0016] The details of one or more examples are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will become apparent from the description and drawings, and from the claims. [Brief description of the drawings]

[0017] [Figure 1] 1 is a block diagram illustrating an example system that implements techniques for streaming media data over a network. [Diagram 2] 2 is a block diagram illustrating an exemplary set of components of the removal unit of FIG. 1 in greater detail. [Diagram 3] FIG. 2 is a conceptual diagram illustrating exemplary multimedia content elements. [Figure 4] 1 is a block diagram illustrating elements of an exemplary video file that may correspond to segments of a presentation. [Diagram 5] 1 is a conceptual diagram illustrating an example camera path segment with a bounding volume in accordance with the techniques of this disclosure. [Figure 6] FIG. 1 is a conceptual diagram illustrating an exemplary virtual object, in this example a chair. [Figure 7] 1 is a flowchart illustrating an example method for retrieving media data in accordance with techniques of this disclosure. [Figure 8] 1 is a flowchart illustrating an example method for retrieving media data in accordance with techniques of this disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] The interactive media data may be streamed over a network. For example, a client device may retrieve the interactive media data using unicast, broadcast, multicast, etc. The interactive media data may be, for example, three-dimensional (3D) media data for extended reality (XR), augmented reality (AR), virtual reality (VR), etc. Thus, when presented to a user, the user can navigate a 3D virtual scene rendered according to the interactive media data.

[0019] An MPEG scene description may describe a three-dimensional (3D) scene for a virtual world or experience, e.g., for an XR, VR, AR, or other interactive media experience. According to techniques of this disclosure, an MPEG scene description may describe objects within the 3D scene, such as chairs, walls, tables, counters, doors, windows, or other solid objects. This disclosure describes techniques whereby an MPEG scene description (or other such description set of data) may be augmented to impose restrictions on virtual camera movement, e.g., to prevent the camera from passing through solid objects such as walls.

[0020] In particular, the scene description may describe a set of paths along which the camera is allowed to move. The paths may be described as a set of anchor points connected through path segments. For expressive enhancement of camera control, each path segment may be augmented with a bounding volume that allows some freedom of movement along the path.

[0021] Additionally or alternatively, the scene description may describe virtual solid objects in the scene. The scene description may provide information representing, for example, the boundaries of the objects, whether the objects can be affected by collision with a user or other objects (such as whether the objects move or remain stationary in response to such collisions), materials for the objects representing how colliding objects interact with the objects, and / or animation data representing animations that should be played or applied to the objects in response to a collision.

[0022] The techniques of this disclosure may be applied to video files that conform to video data encapsulated according to any of the ISO Base Media File Format, the Scalable Video Coding (SVC) file format, the Advanced Video Coding (AVC) file format, the 3rd Generation Partnership Project (3GPP®) file format, and / or the Multiview Video Coding (MVC) file format, or other similar video file formats.

[0023] In HTTP streaming, frequently used operations include HEAD, GET, and partial GET. The HEAD operation retrieves the header of a file associated with a given Uniform Resource Locator (URL) or Uniform Resource Name (URN) without retrieving the payload associated with the URL or URN. The GET operation retrieves the entire file associated with a given URL or URN. The partial GET operation receives a byte range as an input parameter and retrieves a consecutive number of bytes of a file, where the number of bytes corresponds to the byte range received. Thus, a movie fragment may be provided for HTTP streaming, since a partial GET operation can retrieve one or more individual movie fragments. In a movie fragment, there may be several track fragments of different tracks. In HTTP streaming, a media presentation may be a structured collection of data accessible to a client. A client can request and download media data information to present a streaming service to a user.

[0024] In an example of streaming 3GPP data using HTTP streaming, multiple representations may exist for video and / or audio data of the multimedia content. As described below, the different representations may correspond to different coding characteristics (e.g., different profiles or levels of a video coding standard), different coding standards or extensions of a coding standard (such as multiview and / or scalable extensions), or different bit rates. A manifestation of such representations may be defined in a Media Presentation Description (MPD) data structure. A media presentation may correspond to a structured collection of data accessible to an HTTP streaming client device. An HTTP streaming client device can request and download media data information to present a streaming service to a user of the client device. A media presentation may be described in an MPD data structure, which may include updates to the MPD.

[0025] A media presentation may include a sequence of one or more periods. Each period may extend until the start of the next period or, in the case of the last period, until the end of the media presentation. Each period may include one or more representations for the same media content. A representation may be one of several alternatively encoded versions of audio, video, timed text, or other such data. The representations may vary by type of encoding, e.g., bit rate, resolution, and / or codec for video data, and bit rate, language, and / or codec for audio data. The term representation may be used to refer to a section of encoded audio or video data that corresponds to a particular period of multimedia content and that has been encoded in a particular way.

[0026] Representations for a particular time period may be assigned to a group indicated by an attribute in the MPD indicating the adaptation set to which the representation belongs. Representations in the same adaptation set are generally considered as alternatives to each other in that a client device may dynamically and seamlessly switch between these representations, for example to perform bandwidth adaptation. For example, each representation of video data for a particular time period may be assigned to the same adaptation set, so that any of the representations may be selected for decoding to present media data, such as video data or audio data, of the multimedia content for the corresponding time period. In some examples, the media content within a time period may be represented by either one representation from group 0, if present, or a combination of at most one representation from each non-zero group. Timing data for each representation for a time period may be represented relative to a start time of the time period.

[0027] A representation may include one or more segments. Each representation may include an initialization segment, or each segment of a representation may be self-initializing. An initialization segment, if present, may include initialization information for accessing a representation. In general, an initialization segment does not include media data. A segment may be uniquely referenced by an identifier, such as a Uniform Resource Locator (URL), Uniform Resource Name (URN), or Uniform Resource Identifier (URI). The MPD may provide an identifier for each segment. In some examples, the MPD may also provide a byte range in the form of a range attribute, which may correspond to data for a segment within a file accessible by a URL, URN, or URI.

[0028] Different representations may be selected for retrieval substantially simultaneously for different types of media data. For example, a client device may select an audio representation, a video representation, and a timed text representation from which to retrieve segments. In some examples, a client device may select a particular adaptation set to perform bandwidth adaptation. That is, the client device may select an adaptation set including a video representation, an adaptation set including an audio representation, and / or an adaptation set including timed text. Alternatively, a client device may select an adaptation set for one type of media (e.g., video) and directly select a representation for another type of media (e.g., audio and / or timed text).

[0029] 1 is a block diagram illustrating an example system 10 that implements techniques for streaming media data over a network. In this example, system 10 includes a content preparation device 20, a server device 60, and a client device 40. Client device 40 and server device 60 are communicatively coupled by a network 74, which may include the Internet. In some examples, content preparation device 20 and server device 60 may also be coupled by network 74 or another network, or may be communicatively coupled directly. In some examples, content preparation device 20 and server device 60 may include the same device.

[0030] In the example of FIG. 1, content preparation device 20 includes audio source 22 and video source 24. Audio source 22 may comprise, for example, a microphone that generates electrical signals representative of captured audio data to be encoded by audio encoder 26. Alternatively, audio source 22 may comprise a storage medium that stores previously recorded audio data, an audio data generator such as a computerized synthesizer, or any other source of audio data. Video source 24 may comprise a video camera that generates video data to be encoded by video encoder 28, a storage medium encoded with previously recorded video data, a video data generation unit such as a computer graphics source, or any other source of video data. Content preparation device 20 is not necessarily communicatively coupled to server device 60 in all examples, although it may store multimedia content on a separate medium that is read by server device 60.

[0031] The raw audio and video data may include analog or digital data. Analog data may be digitized before being encoded by audio encoder 26 and / or video encoder 28. Audio source 22 may obtain audio data from a speaking participant while the speaking participant is speaking, and video source 24 may simultaneously obtain video data of the speaking participant. In other examples, audio source 22 may comprise a computer-readable storage medium containing stored audio data, and video source 24 may comprise a computer-readable storage medium containing stored video data. Thus, the techniques described in this disclosure may be applied to live, streaming, real-time audio and video data, or to archived, pre-recorded audio and video data.

[0032] An audio frame corresponding to a video frame is generally an audio frame that includes audio data captured (or generated) by audio source 22 contemporaneously with video data captured (or generated) by video source 24 that is included in the video frame. For example, audio source 22 captures audio data while a speaking participant is generally generating audio data by speaking, and video source 24 captures video data of the speaking participant contemporaneously, i.e., while audio source 22 is capturing audio data. Thus, an audio frame may correspond in time to one or more particular video frames. Thus, an audio frame corresponding to a video frame generally corresponds to a situation in which audio data and video data were captured contemporaneously, for which the audio frame and video frame, respectively, include contemporaneously captured audio data and video data.

[0033] In some examples, audio encoder 26 may encode in each encoded audio frame a timestamp representing the time the audio data for the encoded audio frame was recorded, and similarly, video encoder 28 may encode in each encoded video frame a timestamp representing the time the video data for the encoded video frame was recorded. In such examples, audio frames corresponding to a video frame may include an audio frame that includes a timestamp and a video frame that includes the same timestamp. Content preparation device 20 may include internal clocks from which audio encoder 26 and / or video encoder 28 may generate timestamps, or which audio source 22 and video source 24 may use to associate audio and video data, respectively, with timestamps.

[0034] In some examples, audio source 22 may send data to audio encoder 26 corresponding to the time the audio data was recorded, and video source 24 may send data to video encoder 28 corresponding to the time the video data was recorded. In some examples, audio encoder 26 may encode a sequence identifier in the encoded audio data to indicate the relative time order of the encoded audio data, although not necessarily indicating the absolute time the audio data was recorded, and similarly, video encoder 28 may use the sequence identifier to indicate the relative time order of the encoded video data. Similarly, in some examples, the sequence identifier may be mapped with or correlated to a timestamp.

[0035] The audio encoder 26 generally generates a stream of encoded audio data, and the video encoder 28 generates a stream of encoded video data. Each individual stream of data (whether audio or video) may be referred to as an elementary stream. An elementary stream is a single digitally coded (possibly compressed) component of a representation. For example, the coded video or audio portion of a representation may be an elementary stream. An elementary stream may be converted into a Packetized Elementary Stream (PES) before being encapsulated within a video file. Within the same representation, a stream ID may be used to distinguish PES packets belonging to one elementary stream from PES packets belonging to other elementary streams. The basic unit of data of an elementary stream is the Packetized Elementary Stream (PES) packet. Thus, coded video data generally corresponds to an elementary video stream. Similarly, audio data corresponds to one or more respective elementary streams.

[0036] Many video coding standards, such as ITU-T H.264 / AVC and the upcoming High Efficiency Video Coding (HEVC) standard, define syntax, semantics, and decoding processes for error-free bitstreams, any of which conform to a certain profile or level. Video coding standards do not generally prescribe an encoder, but an encoder is tasked with ensuring that the generated bitstream conforms to the standard for a decoder. In the context of a video coding standard, a "profile" corresponds to a subset of algorithms, features, or tools, and the constraints applied to these. As defined by the H.264 standard, for example, a "profile" is a subset of the entire bitstream syntax specified by the H.264 standard. A "level" corresponds to a constraint on the decoder's resource consumption, such as, for example, decoder memory and computation, which is related to picture resolution, bitrate, and block processing speed. A profile may be signaled by a profile_idc (profile indicator) value, while a level may be signaled by a level_idc (level indicator) value.

[0037] For example, the H.264 standard acknowledges that within the range imposed by the syntax of a given profile, it is still possible to require large variations in the performance of encoders and decoders depending on the values ​​taken by syntax elements in the bitstream, such as the specified size of the decoded picture. The H.264 standard further acknowledges that in many applications, it is neither practical nor economical to implement a decoder capable of handling all hypothetical uses of the syntax in a particular profile. Thus, the H.264 standard defines a "level" as a specified set of constraints imposed on the values ​​of syntax elements in the bitstream. These constraints may be simple limitations on values. Alternatively, these constraints may take the form of constraints on arithmetic combinations of values ​​(e.g., the product of the number of pictures decoded per second, the picture height, and the picture width). The H.264 standard further specifies that individual implementations may support different levels for each supported profile.

[0038] A decoder conforming to a profile usually supports all features defined in the profile. For example, as a coding feature, B-picture coding is not supported in the baseline profile of H.264 / AVC, but is supported in other profiles of H.264 / AVC. A decoder conforming to a level should be able to decode any bitstream that does not require resources beyond the limit defined in the level. Profile and level definitions may be useful for explainability. For example, during video transmission, a pair of profile and level definitions may be negotiated and agreed upon for the entire transmission session. More specifically, in H.264 / AVC, a level may define the number of macroblocks that need to be processed, the size of the decoded picture buffer (DPB), the size of the coded picture buffer (CPB), the range of motion vectors in the vertical direction, the limit on the maximum number of motion vectors per two consecutive MBs, and whether B blocks may have sub-macroblock partitions smaller than 8×8 pixels. In this way, a decoder can determine whether it is capable of properly decoding a bitstream.

[0039] In the example of Figure 1, encapsulation unit 30 of content preparation device 20 receives an elementary stream including coded video data from video encoder 28 and an elementary stream including coded audio data from audio encoder 26. In some examples, video encoder 28 and audio encoder 26 may each include a packetizer for forming PES packets from the coded data. In other examples, video encoder 28 and audio encoder 26 may each interface with a respective packetizer for forming PES packets from the coded data. In yet other examples, encapsulation unit 30 may include packetizers for forming PES packets from the coded audio data and the coded video data.

[0040] The video encoder 28 may encode the video data of the multimedia content in various ways to generate various representations of the multimedia content at various bit rates with various characteristics, such as pixel resolution, frame rate, compliance with various coding standards, compliance with various profiles and / or levels of profiles for various coding standards, representations with one or more views (e.g., for two-dimensional or three-dimensional playback), or other such characteristics. A representation as used in this disclosure may include one of audio data, video data, text data (e.g., for closed captioning), or other such data. The representation may include an elementary stream, such as an audio elementary stream or a video elementary stream. Each PES packet may include a stream_id that identifies the elementary stream to which the PES packet belongs. The encapsulation unit 30 is responsible for assembling the elementary streams into video files (e.g., segments) of the various representations.

[0041] Encapsulation unit 30 receives PES packets for the elementary streams of the representation from audio encoder 26 and video encoder 28 and forms corresponding network abstraction layer (NAL) units from the PES packets. Coded video segments may be organized into NAL units, which realize addressing applications of the video representation that are "network friendly," such as video telephony, storage, broadcast, or streaming. NAL units may be classified into video coding layer (VCL) NAL units and non-VCL NAL units. VCL units may contain the core compression engine and may contain block, macroblock, and / or slice level data. Other NAL units may be non-VCL NAL units. In some examples, a coded picture at one time instance may be contained within an access unit, which is typically presented as a primary coded picture and may contain one or more NAL units.

[0042] Non-VCL NAL units may include parameter set NAL units and SEI NAL units, among others. Parameter sets may contain sequence level header information (in sequence parameter sets (SPS)) and picture level header information that does not change frequently (in picture parameter sets (PPS)). With parameter sets (e.g., PPS and SPS), this infrequently changing information does not need to be repeated for each sequence or picture, thus improving coding efficiency. Furthermore, the use of parameter sets may enable out-of-band transmission of important header information, eliminating the need for redundant transmission for error recovery. In an example of out-of-band transmission, parameter set NAL units may be transmitted on a different channel than other NAL units, such as SEI NAL units.

[0043] Supplemental Enhancement Information (SEI) may include information that is not necessary for decoding coded picture samples from VCL NAL units, but may assist processes related to decoding, display, error recovery, and other purposes. SEI messages may be included in non-VCL NAL units. SEI messages are normative parts of some standard specifications and therefore are not always mandatory in the implementation of a decoder that conforms to the standard. The SEI messages may be sequence level SEI messages or picture level SEI messages. Some sequence level information may be included within SEI messages, such as the Scalability Information SEI message in the example of SVC and the View Scalability Information SEI message in MVC. These exemplary SEI messages may convey information, for example, regarding extraction of operation points and characteristics of the operation points. In addition, the encapsulation unit 30 may form a manifest file, such as a Media Presentation Descriptor (MPD) that describes characteristics of the representation. The encapsulation unit 30 may format the MPD according to the Extensible Markup Language (XML).

[0044] The encapsulation unit 30 may provide data for one or more representations of the multimedia content to the output interface 32 along with a manifest file (e.g., MPD). The output interface 32 may include an interface for writing to a storage medium, such as a network interface or a universal serial bus (USB) interface, a CD or DVD writer or burner, an interface to a magnetic or flash storage medium, or other interface for storing or transmitting media data. The encapsulation unit 30 may provide data for each of the representations of the multimedia content to the output interface 32, which may send the data to the server device 60 via a network transmission or a storage medium. In the example of FIG. 1, the server device 60 includes a storage medium 62 that stores various multimedia content 64, each of which includes a respective manifest file 66 and one or more representations 68A-68N (representations 68). In some examples, the output interface 32 may also send the data directly to a network 74.

[0045] In some examples, representations 68 may be separated into adaptation sets, i.e., various subsets of representations 68 may include respective common sets of characteristics, such as codec, profile and level, resolution, number of views, file format of the segments, text type information that may identify, e.g., by speaker, language or other characteristics of the text to be displayed along with the representation and / or audio data to be decoded and presented, camera angle information that may represent the camera angle or field of view of a real-world camera of the scene of the representation in the adaptation set, rating information that represents the suitability of the content for a particular viewer, etc.

[0046] The manifest file 66 may include data indicating a subset of representations 68 that correspond to a particular adaptation set, as well as common characteristics of the adaptation set. The manifest file 66 may also include data representing individual characteristics, such as bit rates, for each representation of the adaptation set. In this manner, the adaptation set may enable simplified network bandwidth adaptation. The representations in an adaptation set may be indicated using child elements of the adaptation set element of the manifest file 66.

[0047] Server device 60 includes a request processing unit 70 and a network interface 72. In some examples, server device 60 may include multiple network interfaces. Additionally, any or all of the features of server device 60 may be implemented on other devices of the content delivery network, such as routers, bridges, proxy devices, switches, or other devices. In some examples, intermediate devices of the content delivery network may cache data of multimedia content 64 and include components substantially conforming to those of server device 60. In general, network interface 72 is configured to transmit and receive data over network 74.

[0048] The request processing unit 70 is configured to receive network requests for data on the storage medium 62 from a client device, such as the client device 40. For example, the request processing unit 70 may implement the Hypertext Transfer Protocol (HTTP) version 1.1, as described in RFC 2616, "Hypertext Transfer Protocol-HTTP / 1.1," by R. Fielding et al., Network Working Group, IETF, June 1999. That is, the request processing unit 70 may be configured to receive HTTP GET or partial GET requests and provide data for the multimedia content 64 in response to those requests. The request may specify a segment of one of the representations 68, for example, using the URL of the segment. In some examples, the request may also specify one or more byte ranges of the segment, thus comprising a partial GET request. The request processing unit 70 may further be configured to respond to an HTTP HEAD request to provide header data for a segment of one of the representations 68. In either case, the request processing unit 70 may be configured to process the request to provide the requested data to a requesting device, such as the client device 40.

[0049] Additionally or alternatively, the request processing unit 70 may be configured to deliver the media data via a broadcast or multicast protocol, such as eMBMS. Content preparation device 20 may create DASH segments and / or subsegments in substantially the same manner as described, but server device 60 may deliver these segments or subsegments using eMBMS or another broadcast or multicast network transport protocol. For example, the request processing unit 70 may be configured to receive a multicast group join request from client device 40. That is, server device 60 may advertise to client devices, including client device 40, an Internet Protocol (IP) address associated with a multicast group associated with a particular multimedia content (e.g., a broadcast of a live event). Client device 40 may then submit a request to join the multicast group. This request may be propagated throughout network 74, e.g., to routers constituting network 74, such that the routers direct traffic destined for the IP address associated with the multicast group to subscribing client devices, such as client device 40.

[0050] 1, multimedia content 64 includes a manifest file 66, which may correspond to a media presentation description (MPD). Manifest file 66 may contain descriptions of various alternative representations 68 (e.g., video services of different qualities), which may include, for example, codec information, profile values, level values, bit rates, and other descriptive characteristics of representations 68. Client device 40 may retrieve the MPD of a media presentation to determine how to access segments of representation 68.

[0051] In particular, retrieval unit 52 may retrieve configuration data (not shown) of client device 40 to determine the decoding capabilities of video decoder 48 and the rendering capabilities of video output 44. Video output 44 may be included in a display device for extended reality, augmented reality, or virtual reality, such as a headset. Similarly, the configuration data may indicate whether video output 44 is capable of rendering 3D video data, for example, for extended reality, augmented reality, virtual reality, etc. The configuration data may also include any or all of a language preference selected by a user of client device 40, one or more camera fields of view corresponding to a depth preference set by the user of client device 40, and / or a rating preference selected by the user of client device 40.

[0052] Retrieval unit 52 may comprise, for example, a web browser or media client configured to submit HTTP GET and partial GET requests. Retrieval unit 52 may correspond to software instructions executed by one or more processors or processing units (not shown) of client device 40. In some examples, all or part of the functionality described with respect to retrieval unit 52 may be implemented in hardware or a combination of hardware, software, and / or firmware, in which case requisite hardware may be provided for executing instructions for the software or firmware.

[0053] The retrieval unit 52 may compare the decoding and rendering capabilities of the client device 40 with the characteristics of the representations 68 indicated by the information in the manifest file 66. The retrieval unit 52 may first retrieve at least a portion of the manifest file 66 to determine the characteristics of the representations 68. For example, the retrieval unit 52 may request a portion of the manifest file 66 that describes the characteristics of one or more adaptation sets. The retrieval unit 52 may select a subset of the representations 68 (e.g., an adaptation set) that has characteristics that can be satisfied by the coding and rendering capabilities of the client device 40. The retrieval unit 52 may then determine bit rates for the representations in the adaptation set, determine a currently available amount of network bandwidth, and retrieve a segment from one of the representations that has a bit rate that can be satisfied by the network bandwidth.

[0054] Generally, a higher bit rate of the representation may provide higher quality video playback, while a lower bit rate of the representation may provide sufficient quality video playback when the available network bandwidth is reduced. Thus, when the available network bandwidth is relatively high, retrieval unit 52 may retrieve data from a representation with a relatively high bit rate, and when the available network bandwidth is low, retrieval unit 52 may retrieve data from a representation with a relatively low bit rate. In this manner, client device 40 may stream multimedia data over network 74 while also adapting to the changing network bandwidth availability of network 74.

[0055] Additionally or alternatively, retrieval unit 52 may be configured to receive data according to a broadcast or multicast network protocol, such as eMBMS or IP multicast. In such an example, retrieval unit 52 may submit a request to join a multicast network group associated with a particular media content. After joining the multicast group, retrieval unit 52 may receive the data of the multicast group without issuing a further request to server device 60 or content preparation device 20. Retrieval unit 52 may submit a request to exit the multicast group when the data of the multicast group is no longer needed, e.g., to stop playback or to change the channel to a different multicast group.

[0056] Network interface 54 may receive and provide data for segments of a selected representation to retrieval unit 52, which may then provide the segments to de-encapsulation unit 50. De-encapsulation unit 50 may de-encapsulate elements of the video file into constituent PES streams and de-packetize the PES streams to retrieve the encoded data and pass it to either audio decoder 46 or video decoder 48, depending on whether the encoded data is part of an audio or video stream, e.g., as indicated by the stream's PES packet headers. Audio decoder 46 decodes the encoded audio data and passes the decoded audio data to audio output 42, while video decoder 48 decodes the encoded video data and passes the decoded video data, which may include multiple views of the stream, to video output 44.

[0057] Each of the video encoder 28, the video decoder 48, the audio encoder 26, the audio decoder 46, the encapsulation unit 30, the decapsulation unit 52, and the decapsulation unit 50 may be implemented as any of a variety of suitable processing circuitry, such as, where applicable, one or more microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), discrete logic circuitry, software, hardware, firmware, or any combination thereof. Each of the video encoder 28 and the video decoder 48 may be included within one or more encoders or decoders, any of which may be integrated as part of a composite video encoder / decoder (codec). Similarly, each of the audio encoder 26 and the audio decoder 46 may be included within one or more encoders or decoders, any of which may be integrated as part of a composite codec. An apparatus including the video encoder 28, the video decoder 48, the audio encoder 26, the audio decoder 46, the encapsulation unit 30, the decapsulation unit 52, and / or the decapsulation unit 50 may include an integrated circuit, a microprocessor, and / or a wireless communication device, such as a cellular telephone.

[0058] Client device 40, server device 60, and / or content preparation device 20 may be configured to operate in accordance with the techniques of this disclosure. By way of example, this disclosure describes these techniques with respect to client device 40 and server device 60. However, it should be understood that content preparation device 20 may be configured to implement these techniques in place of (or in addition to) server device 60.

[0059] Encapsulation unit 30 may form NAL units that include a header that identifies the program to which the NAL unit belongs, as well as a payload, e.g., audio data, video data, or data that describes the transport or program stream to which the NAL unit corresponds. For example, in H.264 / AVC, a NAL unit includes a one-byte header and a variable-sized payload. A NAL unit that includes video data within its payload may include various levels of granularity of the video data. For example, a NAL unit may include a block of video data, multiple blocks, a slice of video data, or an entire picture of video data. Encapsulation unit 30 may receive encoded video data from video encoder 28 in the form of PES packets of elementary streams. Encapsulation unit 30 may associate each elementary stream with a corresponding program.

[0060] Encapsulation unit 30 may also assemble an access unit from multiple NAL units. In general, an access unit may include one or more NAL units to represent a frame of video data, as well as audio data corresponding to the frame when such audio data is available. An access unit generally includes all NAL units for one output time instance, e.g., all audio data and video data for one time instance. For example, if each view has a frame rate of 20 frames per second (fps), each time instance may correspond to a time interval of 0.05 seconds. During this time interval, a particular frame for all views of the same access unit (same time instance) may be rendered simultaneously. In one example, an access unit may include a coded picture in one time instance, which may be presented as a primary coded picture.

[0061] Thus, an access unit may include all audio and video frames of a common time instance, e.g., all views corresponding to time X. This disclosure also refers to the coded pictures of a particular view as a "view component." That is, a view component may include coded pictures (or frames) for a particular view at a particular time. Thus, an access unit may be defined as including all view components of a common time instance. The decoding order of the access units is not necessarily the same as the output or display order.

[0062] A media presentation may include a media presentation description (MPD) that may contain descriptions of different alternative representations (e.g., video services with different qualities), and the description may include, for example, codec information, profile values, and level values. An MPD is an example of a manifest file, such as manifest file 66. Client device 40 may retrieve the MPD of a media presentation to determine how to access movie fragments of the various presentations. The movie fragments may be placed within a movie fragment box (moof box) of a video file.

[0063] Manifest file 66 (which may include, for example, an MPD) may advertise the availability of segments of representations 68. That is, the MPD may include information indicating the wall clock time at which a first segment of one of representations 68 becomes available, as well as information indicating the duration of the segment within representation 68. In this manner, retrieval unit 52 of client device 40 can determine when each segment is available based on the start time as well as the duration of the segment preceding a particular segment.

[0064] After the encapsulation unit 30 assembles the NAL units and / or access units into a video file based on the received data, the encapsulation unit 30 passes the video file to the output interface 32 for output. In some examples, the encapsulation unit 30 may store the video file locally or send the video file to a remote server via the output interface 32 instead of sending the video file directly to the client device 40. The output interface 32 may include, for example, a transmitter, a transceiver, a device for writing data to a computer-readable medium, such as, for example, an optical drive, a magnetic media drive (e.g., a floppy drive), a universal serial bus (USB) port, a network interface, or other output interface. The output interface 32 outputs the video file to a computer-readable medium, such as, for example, a transmission signal, a magnetic medium, an optical medium, a memory, a flash drive, or other computer-readable medium.

[0065] Network interface 54 may receive NAL units or access units over network 74 and provide the NAL units or access units to decapsulation unit 50 via retrieval unit 52. Decapsulation unit 50 may decapsulate elements of the video file into constituent PES streams, depacketize the PES streams to retrieve the encoded data, and send the encoded data to either audio decoder 46 or video decoder 48, depending on whether the encoded data is part of an audio or video stream, e.g., as indicated by the stream's PES packet headers. Audio decoder 46 decodes the encoded audio data and sends the decoded audio data to audio output 42, while video decoder 48 decodes the encoded video data and sends the decoded video data, which may include multiple views of the stream, to video output 44.

[0066] According to the techniques of this disclosure, a user of a client device 40 may obtain media data associated with a 3D virtual scene, e.g., for extended reality (XR), augmented reality (AR), virtual reality (VR), etc. The user may navigate through the 3D virtual scene using one or more devices in communication with the client device 40, such as a controller. Additionally or alternatively, the client device 40 may include sensors, cameras, etc. for determining that the user has moved within real-world space, and the client device 40 may translate such real-world movement into virtual space movement.

[0067] The 3D virtual scene may include one or more virtual solid objects. Such objects may include, for example, walls, windows, tables, chairs, or any other such objects that may appear in a virtual scene. In accordance with the techniques of this disclosure, the media data retrieved by retrieval unit 52 may include a scene description that describes such virtual solid objects. The scene description may, for example, conform to the MPEG scene description elements of glTF2.0.

[0068] In some examples, the scene description may include a description of allowed camera movements. For example, the scene description may describe one or more bounding volumes within which the virtual camera is permitted to move (e.g., according to a volume shaped like a sphere, cube, cone, pyramid, etc.) such that the virtual camera is not permitted to move beyond the limits of the shape. That is, the bounding volume may describe the allowed camera movement volume within which the virtual camera is permitted to move. Additionally or alternatively, the scene description may describe one or more vertices or anchor points, as well as permitted paths (e.g., segments) between the vertices or anchor points. The client device 40 may only permit the virtual camera to move along the permitted paths and / or within the bounding volume.

[0069] In some examples, additionally or alternatively, the scene description may describe one or more virtual solid objects in the scene that the virtual camera cannot pass through.

[0070] Figure 2 is a block diagram illustrating in more detail an exemplary set of components of retrieval unit 52 of Figure 1. In this example, retrieval unit 52 includes an eMBMS middleware unit 100, a DASH client 110, a media application 112, and a presentation engine 114.

[0071] In this example, the eMBMS middleware unit 100 further includes an eMBMS receiving unit 106, a cache 104, and a proxy server 102. In this example, the eMBMS receiving unit 106 may receive data via eMBMS in accordance with File Delivery over Unidirectional Transport (FLUTE), e.g., as described in T. Paila et al., “FLUTE - File Delivery over Unidirectional Transport,” Network Working Group, RFC 6726, November 2012, available at tools.ietf.org / html / rfc6726. That is, the eMBMS receiving unit 106 may receive files via broadcast from a server device 60, which may act as, e.g., a Broadcast / Multicast Service Center (BM-SC).

[0072] When the eMBMS middleware unit 100 receives data for a file, the eMBMS middleware unit may store the received data in cache 104. Cache 104 may include a computer-readable storage medium, such as flash memory, a hard disk, RAM, or any other suitable storage medium.

[0073] The proxy server unit 102 may act as a server for the DASH client 110. For example, the proxy server unit 102 may provide the DASH client 110 with an MPD file or other manifest file. The proxy server unit 102 may advertise availability times for the segments in the MPD file as well as in hyperlinks from which the segments can be retrieved. These hyperlinks may include a local host address prefix (e.g., 127.0.0.1 for IPv4) that corresponds to the client device 40. In this manner, the DASH client 110 may request the segments from the proxy server unit 102 using an HTTP GET or partial GET request. For example, for a segment available from the link http: / / 127.0.0.1 / rep1 / seg3, the DASH client 110 may construct an HTTP GET request that includes a request for http: / / 127.0.0.1 / rep1 / seg3 and submit the request to the proxy server unit 102. The proxy server unit 102 may retrieve requested data from the cache 104 and provide the data to the DASH client 110 in response to such a request.

[0074] The DASH client 110 provides the retrieved media data to the media application 112. The media application 112 may be, for example, a web browser, a game engine, or another application that receives and presents the media data. Furthermore, the presentation engine 114 represents an application that interacts with the media application 112 to present the retrieved media data in the 3D virtual environment. The presentation engine 114 may, for example, map two-dimensional media data onto a 3D projection. The presentation engine 114 may also receive input from other elements of the client device 40 to determine a user's location in the 3D virtual environment and an orientation in which the user is facing at that location. For example, the presentation engine 114 may determine the X, Y, and Z coordinates for the user's location and the orientation in which the user is looking to determine the appropriate media data to display to the user. Additionally, the presentation engine 114 may receive camera movement data representing real-world user movement data and translate the real-world user movement data into 3D virtual space movement data.

[0075] According to the techniques of this disclosure, the eMBMS middleware unit 100 may receive media data (e.g., by glTF2.0) by broadcast or multicast, and the DASH client 110 may then retrieve the media data from the eMBMS middleware unit 100. The media data may include a scene description including camera control information indicating how a virtual camera may move through a virtual scene. For example, the scene description may include data describing allowable paths through a virtual scene, e.g., along defined paths between anchor points. Additionally or alternatively, the scene description may include data describing a bounding volume that represents a volume within which the virtual camera is permitted to move. Additionally or alternatively, the scene description may include data describing one or more solid virtual objects in a 3D virtual environment, such as walls, tables, chairs, etc. For example, the data of the scene description may define collision boundaries of the 3D virtual object. The scene description may further include data representing what happens when a collision occurs with such an object, whether the object is static (e.g., as in the case of a wall) or dynamic (e.g., as in the case of a chair), such as an animation being played with the object.

[0076] The presentation engine 114 may use the scene description to determine what to present in the event of a collision with a 3D virtual object and / or an attempt to move outside of a permitted path or volume. For example, if the scene description includes data about a permitted path or bounding volume and the user attempts to move beyond the permitted path or bounding volume, the presentation engine 114 may only avoid updating the display, thereby indicating that such movement is not permitted. As another example, if the scene description includes data about a 3D virtual solid object and the user attempts to move through the 3D virtual solid object, the presentation engine 114 may avoid updating the display if the 3D virtual solid object is static. If the 3D virtual solid object is not static, the presentation engine 114 may determine an animation to display for the object, e.g., a translational and / or rotational movement to be applied to the object. For example, if the 3D virtual solid object is a chair, the animation data may indicate that the chair will be pushed along the floor or will fall over if a collision occurs.

[0077] FIG. 3 is a conceptual diagram illustrating elements of an exemplary multimedia content 120. The multimedia content 120 may correspond to the multimedia content 64 (FIG. 1) or another multimedia content stored in the storage medium 62. In the example of FIG. 3, the multimedia content 120 includes a media presentation description (MPD) 122 and a number of representations 124A-124N (representations 124). Representation 124A includes optional header data 126 and segments 128A-128N (segments 128), while representation 124N includes optional header data 130 and segments 132A-132N (segments 132). The letter N is used for convenience to designate the last movie fragment in each of the representations 124. In some examples, there may be different numbers of movie fragments between the representations 124.

[0078] MPD 122 may include a data structure separate from representation 124. MPD 122 may correspond to manifest file 66 of Figure 1. Similarly, representation 124 may correspond to representation 68 of Figure 1. In general, MPD 122 may include data generally representative of characteristics of representation 124, such as coding and rendering characteristics, adaptation sets, profiles to which MPD 122 supports, text type information, camera angle information, rating information, trick mode information (e.g., information indicative of a representation that includes a temporal subsequence), and / or information for retrieving discrete time periods (e.g., for insertion of targeted advertisements into the media content being played).

[0079] Header data 126, when present, may describe characteristics of segment 128, such as the temporal location of a random access point (RAP, also called a stream access point (SAP)), which of segments 128 contain a random access point, a byte offset to the random access point within segment 128, a uniform resource locator (URL) for segment 128, or other aspects of segment 128. Header data 130, when present, may describe similar characteristics of segment 132. Additionally or alternatively, such characteristics may be contained entirely within MPD 122.

[0080] Segments 128, 132 include one or more coded video samples, each of which may include a frame or slice of video data. Each of the coded video samples of segment 128 may have similar characteristics, e.g., height, width, and bandwidth requirements. Such characteristics may be described by data in MPD 122, although such data is not shown in the example of FIG. 3. MPD 122 may include characteristics as described by 3GPP specifications, plus any or all of the signaled information described in this disclosure.

[0081] Each of the segments 128, 132 may be associated with a unique Uniform Resource Locator (URL). Thus, each of the segments 128, 132 may be separately retrievable using a streaming network protocol such as DASH. In this manner, a destination device such as the client device 40 may retrieve a segment 128 or 132 using an HTTP GET request. In some examples, the client device 40 may retrieve a particular byte range of the segment 128 or 132 using an HTTP partial GET request.

[0082] FIG. 4 is a block diagram illustrating elements of an exemplary video file 150 that may correspond to a segment of a representation such as one of the segments 128, 132 of FIG. 3. Each of the segments 128, 132 may include data that substantially conforms to the arrangement of data shown in the example of FIG. 4. The video file 150 may be said to encapsulate a segment. As explained above, video files according to the ISO base media file format and its extensions store data in a series of objects called "boxes." In the example of FIG. 4, the video file 150 includes a file type (FTYP) box 152, a movie (MOOV) box 154, a segment index (sidx) box 162, a movie fragment (MOOF) box 164, and a movie fragment random access (MFRA) box 166. Although FIG. 4 represents an example video file, it should be understood that other media files may include other types of media data (e.g., audio data, timed text data, etc.) that are similarly arranged to the data of the video file 150 according to the ISO base media file format and its extensions.

[0083] The file type (FTYP) box 152 generally represents the file type of the video file 150. The file type box 152 may contain data that identifies specifications that represent the best use of the video file 150. The file type box 152 may alternatively be placed before the MOOV box 154, the Movie Fragment box 164, and / or the MFRA box 166.

[0084] In some examples, a segment such as video file 150 may include an MPD update box (not shown) before FTYP box 152. The MPD update box may include information indicating that the MPD corresponding to a representation that includes video file 150 should be updated, along with information for updating the MPD. For example, the MPD update box may provide a URI or URL of a resource used to update the MPD. As another example, the MPD update box may include data for updating the MPD. In some examples, the MPD update box may immediately follow a segment type (STYP) box (not shown) of video file 150, which may define the segment type of video file 150.

[0085] 4, MOOV box 154 includes a Movie Header (MVHD) box 156, a Track (TRAK) box 158, and one or more Movie Extension (MVEX) boxes 160. In general, MVHD box 156 may describe general characteristics of video file 150. For example, MVHD box 156 may include data representing when video file 150 was originally created, data representing when video file 150 was last modified, data representing a timescale of video file 150, data representing the playback length of video file 150, or other data generally describing video file 150.

[0086] TRAK box 158 may contain data for a track of video file 150. TRAK box 158 may contain a Track Header (TKHD) box that describes characteristics of the track that corresponds to TRAK box 158. In some examples, TRAK box 158 may contain coded video pictures, while in other examples, the coded video pictures for the track may be contained within a movie fragment 164 that may be referenced by data in TRAK box 158 and / or data in sidx box 162.

[0087] In some examples, video file 150 may include more than one track. Thus, MOOV box 154 may include a number of TRAK boxes equal to the number of tracks in video file 150. TRAK box 158 may describe characteristics of the corresponding track of video file 150. For example, TRAK box 158 may describe temporal and / or spatial information of the corresponding track. A TRAK box similar to TRAK box 158 of MOOV box 154 may describe characteristics of a parameter set track when encapsulation unit 30 (FIG. 3) includes the parameter set track in a video file such as video file 150. Encapsulation unit 30 may signal the presence of a sequence level SEI message for a parameter set track within a TRAK box describing the parameter set track.

[0088] MVEX box 160 may describe characteristics of the corresponding movie fragment 164, for example, to signal that video file 150 includes movie fragment 164 in addition to the video data contained in MOOV box 154, if any. In the context of streaming video data, coded video pictures may be contained in movie fragment 164 rather than in MOOV box 154. Thus, all coded video samples may be contained in movie fragment 164 rather than in MOOV box 154.

[0089] The MOOV box 154 may contain a number of MVEX boxes 160 equal to the number of movie fragments 164 in the video file 150. Each of the MVEX boxes 160 may describe the characteristics of a corresponding one of the movie fragments 164. For example, each MVEX box may include a Movie Extension Header Box (MEHD) box that describes the duration of the corresponding one of the movie fragments 164.

[0090] As mentioned above, encapsulation unit 30 may store a sequence data set in a video sample that does not include actual coded video data. A video sample may generally correspond to an access unit, which is a representation of a coded picture at a particular time instance. In the context of AVC, a coded picture includes one or more VCL NAL units that contain information for constructing all pixels of the access unit and other associated non-VCL NAL units, such as SEI messages. Thus, encapsulation unit 30 may include a sequence data set, which may include a sequence level SEI message, in one of the movie fragments 164. Encapsulation unit 30 may further signal the presence of the sequence data set and / or the sequence level SEI message as present in one of the movie fragments 164 in one of the MVEX boxes 160 corresponding to one of the movie fragments 164.

[0091] The SIDX box 162 is an optional element of the video file 150; that is, a video file conforming to the 3GPP file format or other such file formats does not necessarily include the SIDX box 162. According to an example of a 3GPP file format, the SIDX box may be used to identify a subsegment of a segment (e.g., a segment contained within the video file 150). The 3GPP file format defines a subsegment as "a self-contained set of one or more consecutive Movie Fragment boxes with corresponding Media Data boxes, where the Media Data box containing the data referenced by a Movie Fragment box must follow that Movie Fragment box and precede the next Movie Fragment box containing information about the same track." The 3GPP file format also indicates that the SIDX box "contains a series of references to subsegments of the (sub)segment documented by the box. The referenced subsegments are contiguous in presentation time. Similarly, the bytes referenced by a Segment Index box are always contiguous within the segment. The referenced size gives a count of the number of bytes in the referenced material."

[0092] SIDX box 162 generally provides information describing one or more subsegments of a segment contained within video file 150. For example, such information may include a playback time at which the subsegment begins and / or ends, a byte offset for the subsegment, whether the subsegment contains (e.g., begins with) a Stream Access Point (SAP), the type of SAP (e.g., whether the SAP is an Instantaneous Decoder Refresh (IDR) picture, a Clean Random Access (CRA) picture, a Broken Link Access (BLA) picture, etc.), the location of the SAP (in terms of playback time and / or byte offset) within the subsegment, etc.

[0093] A movie fragment 164 may include one or more coded video pictures. In some examples, a movie fragment 164 may include one or more groups of pictures (GOPs), each of which may include multiple coded video pictures, e.g., frames or pictures. In addition, as described above, a movie fragment 164 may include a sequence data set in some examples. Each of the movie fragments 164 may include a Movie Fragment Header Box (MFHD, not shown in FIG. 4). The MFHD box may describe characteristics of the corresponding movie fragment, such as the sequence number of the movie fragment. The movie fragments 164 may be included in the video file 150 in sequence number order.

[0094] The MFRA box 166 may describe random access points within the movie fragments 164 of the video file 150. This may assist in implementing trick modes, such as implementing a search for a particular temporal location (i.e., play time) within a segment encapsulated by the video file 150. The MFRA box 166 is generally optional and need not be included in the video file, in some examples. Similarly, a client device, such as the client device 40, does not necessarily need to reference the MFRA box 166 to correctly decode and display the video data of the video file 150. The MFRA box 166 may include a number of track fragment random access (TFRA) boxes (not shown) equal to the number of tracks of the video file 150, or in some examples may include a number of TFRA boxes equal to the number of media tracks (e.g., non-hint tracks) of the video file 150.

[0095] In some examples, the movie fragment 164 may include one or more stream access points (SAPs), such as an IDR picture. Similarly, the MFRA box 166 may provide an indication of the location of the SAPs within the video file 150. Thus, a temporal subsequence of the video file 150 may be formed from the SAPs of the video file 150. The temporal subsequence may also include other pictures, such as P-frames and / or B-frames, that are dependent on the SAPs. The frames and / or slices of the temporal subsequence may be ordered within segments such that frames / slices of the temporal subsequence that depend on other frames / slices of the subsequence may be properly decoded. For example, in a hierarchical organization of data, data used for prediction for other data may also be included within the temporal subsequence.

[0096] 5 is a conceptual diagram illustrating an example camera path segment 212 with a bounding volume, in accordance with the techniques of this disclosure. In particular, in a 3D scene 200, a camera 202 represents a viewpoint from which a user can view a portion of the 3D scene 200. In this example, a path segment 212 is defined between points 204 and 206. Moreover, a bounding volume is defined by the extrusion of points from bounding box 208 to bounding box 210 along the path segment 212. Thus, in this example, the camera 202 is permitted to move within the bounding volume along the path segment 212, but is restricted from moving beyond the bounding volume.

[0097] The scene description may describe a set of paths along which a camera, such as camera 202, is permitted to move. The paths may be described as a set of anchor points, such as points 204, 206, connected by path segments, such as path segment 212. In some examples, such as the example of FIG. 5, each path segment may be augmented with a bounding volume that allows some freedom of movement along the path.

[0098] The scene camera, and therefore the viewer, is then free to move within the bounding volume along path segments, which may be described using more complex geometric forms to allow finer control of the path.

[0099] Additionally, camera parameters can be constrained at each point along the path. Parameters can be provided for every anchor point and then used with an interpolation function to calculate corresponding parameters for every point along the path segment. The interpolation function can be applied to all parameters, including the bounding volume.

[0100] The camera control extension mechanism of this disclosure may be implemented as a glTF 2.0 extension that defines camera controls for a scene. The camera control extension may be identified by an "MPEG_camera_control" tag, which may be included in the extensionsUsed element and the extensionsRequired element for the 3D scene.

[0101] An exemplary "MPEG_camera_control" extension is shown below in Table 1 and may be defined in the "camera" element of a scene description. [Table 1] The camera control information may be structured as follows: For each anchor point, the (x,y,z) coordinates of the anchor point can be expressed using floating-point values. For each path segment, the (i,j) indices of the first and second anchor points of the path segment may be expressed as integer values. About the bounding volume: If the boundingVolume is BV_CONE, then the (r1, r2) radii of the circles of the first and second anchor points may be given. If the boundingVolume is BV_FRUSTUM, then ((x,y,z)_topleft,w,h) may be given for each anchor point of the path segment. If the boundingVolume is a BV_SPHERE, then for each anchor point of the path segment, r may be given as the radius of a sphere. If intrinsicParameters is true, the intrinsic parameters object may be modified.

[0102] A presentation engine (e.g., presentation engine 114 of FIG. 2 or another element of client device 40 that may differ from the components shown in FIGS. 1 and 2) may support the MPEG_camera_control extension or other such data structures. If the scene provides camera control information, the presentation engine may constrain the camera movement to the path shown such that the (x,y,z) coordinates of the camera are always on the path segment or within the bounding volume of the path segment. The presentation engine may provide visual, audio, and / or haptic feedback to the viewer as the viewer approaches the boundary of the bounding volume.

[0103] 6 is a conceptual diagram illustrating an exemplary virtual object 220, which in this example is a chair. To provide an immersive experience to the viewer, it is important that the viewer properly interacts with objects in the scene. The viewer should not be able to walk through solid objects in the scene, such as walls, chairs, and tables, or other such solid objects.

[0104] FIG. 6 shows a 3D mesh representation of a chair, defined as a set of cuboids, along with collision boundaries. To provide a description of the collision boundaries of such a 3D mesh, an MPEG_mesh_collision extension data structure may be defined. The extension data structure may be defined on a mesh object as a set of cuboids around the mesh geometry. Table 2 below represents an exemplary set of properties that may be included in such an extension data structure. [Table 2]

[0105] Mesh collision information may include box vertex coordinates (x,y,z) for box boundaries or sphere center and radius for spherical boundaries. Values ​​may be given as floating point numbers.

[0106] The Presentation Engine may support the MPEG_mesh_collision extension or other such data structures. The Presentation Engine may ensure that the camera position (x,y,z) does not fall within one of the defined mesh cuboids at any time. Collisions may be signaled to the viewer through visual, audio, and / or haptic feedback. The Presentation Engine may use information about the bounds for the nodes to initialize and configure a 3D physics engine that detects collisions.

[0107] Figure 7 is a flow chart illustrating an example method for retrieving media data in accordance with techniques of this disclosure. The method of Figure 7 is described with respect to client device 40 of Figure 1 and retrieval unit 52 of Figure 2. Other such devices may be configured to perform this method or a similar method.

[0108] First, client device 40 may retrieve media data (250). For example, retrieval unit 52 may retrieve media data that is, for example, compliant with glTF2.0. In some examples, retrieval unit 52 may retrieve the media data directly, for example, by unicast, such as using DASH. In some examples, a middleware unit of retrieval unit 52, such as eMBMS middleware 100 of FIG. 2, may receive the media data by broadcast or multicast, and then a DASH client, for example, DASH client 110 of FIG. 2, may retrieve the media data from the middleware unit.

[0109] The media data may include a scene description. Thus, retrieval unit 52 or another component of client device 40 may extract the scene description from the media data (252). The scene description may be an MPEG scene description including camera control data in accordance with the techniques of this disclosure. retrieval unit 52 may provide the scene description to presentation engine 114. Presentation engine 114 may thus receive the scene description and determine (254) camera control data for the three-dimensional scene from the scene description. The camera control data may conform to Table 1 above. That is, for example, the camera control data may include one or more anchor points for a camera path, one or more segments between anchor points for the camera path, a bounding volume such as a cone, pyramid, or sphere, internal parameters that may be modified at each anchor point, and / or an accessor that provides the camera control information.

[0110] The presentation engine 114 may further determine movement constraints from the camera control data (256). For example, the presentation engine 114 may determine two or more anchor points and an acceptable path between the anchor points from the movement constraints of the camera control data. Additionally or alternatively, the presentation engine 114 may determine a bounding volume, such as a cube, sphere, pyramid, cone, etc., from the movement constraints of the camera control data. The presentation engine 114 may use the acceptable path to determine a path along which the virtual camera is permitted to move and / or a path along which the virtual camera is permitted to move within the bounding volume but not outside of the bounding volume. The acceptable path and / or bounding volume may be defined to ensure that the virtual camera does not exceed a 3D solid virtual object, such as a wall. That is, the bounding volume or acceptable path may be defined to be within one or more 3D solid virtual objects, such as a wall, floor, ceiling, or other object in the 3D virtual scene.

[0111] The Presentation Engine 114 may then receive the camera movement data (258). For example, the Presentation Engine 114 may receive data from one or more controllers, such as a handheld controller and / or a headset including a display, representing the orientation of the headset and movement of the headset and / or the virtual camera, such as directional and / or rotational movement. The Presentation Engine 114 may determine that the camera movement data requires camera movement through a 3D solid virtual object, such as beyond the limits of a bounding volume or along a path that is not one of the defined allowed paths (260). In response, the Presentation Engine 114 may prevent the virtual camera from passing through the 3D solid virtual object (262).

[0112] Thus, the method of FIG. 7 represents an example of a method for retrieving media data that includes the steps of receiving, by a Presentation Engine, streamed media data representing a virtual three-dimensional scene including at least one virtual solid object; receiving, by the Presentation Engine, camera control data for the three-dimensional scene, the camera control data including data defining constraints for preventing the virtual camera from passing through the at least one virtual solid object; receiving, by the Presentation Engine, camera movement data from a user requesting that the virtual camera move through the at least one virtual solid object; and, in response to the camera movement data, using the camera control data to prevent, by the Presentation Engine, the virtual camera from passing through the at least one virtual solid object.

[0113] Figure 8 is a flow chart illustrating an example method for retrieving media data in accordance with techniques of this disclosure. The method of Figure 8 is described with respect to client device 40 of Figure 1 and retrieval unit 52 of Figure 2. Other such devices may be configured to perform this or a similar method.

[0114] First, client device 40 may retrieve media data (280). For example, retrieval unit 52 may retrieve media data that is, for example, compliant with glTF2.0. In some examples, retrieval unit 52 may retrieve the media data directly, for example, by unicast, such as using DASH. In some examples, a middleware unit of retrieval unit 52, such as eMBMS middleware 100 of FIG. 2, may receive the media data by broadcast or multicast, and then a DASH client, for example, DASH client 110 of FIG. 2, may retrieve the media data from the middleware unit.

[0115] The media data may include a scene description. Thus, retrieval unit 52 or another component of client device 40 may extract the scene description from the media data (282). The scene description may be an MPEG scene description including object collision data in accordance with the techniques of this disclosure. Retrieval unit 52 may provide the scene description to presentation engine 114. Presentation engine 114 may thus receive the scene description and determine object collision data for one or more 3D solid virtual objects from the scene description (284). The object collision data may conform to Table 2 above. That is, the object collision data may include, for example, data representing a boundary representing an array of boundary shapes defining a collision boundary of a mesh (3D virtual solid) object, data indicating whether the object is static (i.e., movable), a material representing a collision material for the object, and / or an animation to be presented for the object if a collision occurs.

[0116] The presentation engine 114 may further determine object collision data from the camera control data (286). For example, the presentation engine 114 may determine a boundary representing an array of boundary shapes that define a collision boundary of a mesh (3D virtual solid) object, data indicating whether the object is static (i.e., movable), a material representing a collision material for the object, and / or an animation to be presented for the object when a collision occurs. The presentation engine 114 may use the object collision data to determine how to react when a collision occurs with a 3D solid virtual object.

[0117] The presentation engine 114 may then receive the camera movement data (288). For example, the presentation engine 114 may receive data from one or more controllers, such as a handheld controller and / or a headset including a display, representing an orientation of the headset and movement of the headset and / or the virtual camera, such as directional and / or rotational movement. The presentation engine 114 may determine that the camera movement data requests camera movement, such as into or through a 3D solid virtual object defined by the object collision data (290). In response, the presentation engine 114 may prevent the virtual camera from passing through the 3D solid virtual object (292). For example, if the object is static as indicated by the object collision data, the presentation engine 114 may prevent the virtual camera from moving into and through the object. As another example, if the object is not static (e.g., movable), the presentation engine 114 may determine a reaction from the object collision data, such as, for example, an animation to play for the object if the object is to tip over or move in response to a collision with the object.

[0118] Thus, the method of FIG. 8 represents an example of a method for retrieving media data that includes the steps of receiving, by a Presentation Engine, streamed media data representing a virtual three-dimensional scene including at least one virtual solid object; receiving, by the Presentation Engine, object collision data representing a boundary of the at least one virtual solid object; receiving, by the Presentation Engine, camera movement data from a user requesting that a virtual camera move through the at least one virtual solid object; and, in response to the camera movement data, using the object collision data, preventing, by the Presentation Engine, the virtual camera from passing through the at least one virtual solid object.

[0119] Some examples of the techniques of this disclosure are summarized in the following paragraphs.

[0120] Clause 1: A method of retrieving media data, the method comprising the steps of: receiving, by a presentation engine, streamed media data representing a virtual three-dimensional scene including at least one virtual solid object; receiving, by the presentation engine, camera control data for the three-dimensional scene, the camera control data including data defining allowed locations for the virtual camera; receiving, by the presentation engine, camera movement data from a user requesting that the virtual camera move through the at least one virtual solid object; and updating, by the presentation engine, a location of the virtual camera using the camera control data to ensure that the virtual camera remains within the allowed locations.

[0121] Clause 2: The method of clause 1, wherein updating the location of the virtual camera includes preventing the virtual camera from passing through at least one virtual solid object.

[0122] Clause 3: The method of clause 1, wherein the streamed media data includes glTF 2.0 media data.

[0123] Clause 4: The method of clause 1, wherein receiving the streamed media data includes requesting the streamed media data from a retrieval unit via an application programming interface (API).

[0124] Clause 5: The method of clause 1, wherein the camera control data is included in an MPEG scene description.

[0125] Clause 6: The method of clause 1, wherein the camera control data includes data defining two or more anchor points and one or more segments between the anchor points, the segments representing permissible camera movement vectors for the virtual camera, and the step of updating the location of the virtual camera includes a step of allowing the virtual camera to traverse only the segments between the anchor points.

[0126] Clause 7: The method of clause 1, wherein the camera control data includes data defining a bounding volume representing an allowable camera movement volume for the virtual camera, and wherein updating the location of the virtual camera includes allowing the virtual camera to traverse only the allowable camera movement volume.

[0127] Clause 8: The method of clause 7, wherein the data defining the bounding volume includes data defining at least one of a cone, a pyramid, or a sphere.

[0128] Clause 9: The method of clause 1, wherein the camera control data is contained in the MPEG_camera_control extension.

[0129] Clause 10: The method of clause 9, wherein the MPEG_camera_control extension includes one or more of anchor data representing a number of anchor points for an allowable path for the virtual camera, segment data representing a number of path segments for an allowable path between the anchor points, bounding volume data representing a bounding volume for the virtual camera, internal parameters indicating whether camera parameters are modified at each of the anchor points, and accessor data representing an index of an accessor that provides the camera control data.

[0130] Clause 11: The method of clause 1, wherein the at least one virtual solid object includes one of a virtual wall, a virtual chair, or a virtual table.

[0131] Clause 12: The method of clause 1, further comprising the step of determining an allowable path for the virtual camera from the camera control data, and wherein updating the location of the virtual camera includes ensuring that the virtual camera moves only along virtual paths that are within the allowable path defined in the camera control data.

[0132] Clause 13: The method of clause 1, wherein the camera control data is included in the MPEG_mesh_collision extension.

[0133] Clause 14: A device for retrieving media data, comprising: a memory configured to store the media data; and one or more processors implemented in circuitry and configured to run a presentation engine, the presentation engine configured to: receive streamed media data representing a virtual three-dimensional scene including at least one virtual solid object; receive camera control data for the three-dimensional scene, the camera control data including data defining allowed locations for a virtual camera; receive camera movement data from a user requesting that the virtual camera move through the at least one virtual solid object; and use the camera control data to update the location of the virtual camera to ensure that the virtual camera remains within the allowed location.

[0134] Clause 15: The device of clause 14, wherein the presentation engine is configured to prevent the virtual camera from passing through at least one virtual solid object.

[0135] Clause 16: The device of clause 14, wherein the streamed media data includes glTF 2.0 media data.

[0136] Clause 17: The device of clause 14, wherein the presentation engine is configured to request the streamed media data from the retrieval unit via an application programming interface (API).

[0137] Clause 18: The device of clause 14, wherein the camera control data is contained within an MPEG scene description.

[0138] Clause 19: The device of clause 14, wherein the camera control data includes data defining two or more anchor points and one or more segments between the anchor points, the segments representing permissible camera movement vectors for the virtual camera, and wherein, to update a location of the virtual camera, the presentation engine is configured to allow the virtual camera to traverse only the segments between the anchor points.

[0139] Clause 20: The device of clause 14, wherein the camera control data includes data defining a bounding volume representing an allowable camera movement volume for the virtual camera, and wherein, to update the location of the virtual camera, the presentation engine is configured to allow the virtual camera to traverse only the allowable camera movement volume.

[0140] Clause 21: The device of clause 20, wherein the data defining the bounding volume includes data defining at least one of a cone, a pyramid, or a sphere.

[0141] Clause 22: For devices according to clause 14, the camera control data is contained in the MPEG_camera_control extension.

[0142] Clause 23: The device of clause 22, wherein the MPEG_camera_control extension includes one or more of anchor data representing a number of anchor points for an allowable path for the virtual camera, segment data representing a number of path segments for an allowable path between the anchor points, bounding volume data representing a bounding volume for the virtual camera, internal parameters indicating whether camera parameters are modified at each of the anchor points, and accessor data representing an index of an accessor providing the camera control data.

[0143] Clause 24: The device of clause 14, wherein the at least one virtual solid object includes one of a virtual wall, a virtual chair, or a virtual table.

[0144] Clause 25: The device of clause 14, wherein the presentation engine is further configured to determine from the camera control data an allowable path for the virtual camera, and wherein, to update a location of the virtual camera, the presentation engine is configured to ensure that the virtual camera moves only along virtual paths that are within the allowable paths defined in the camera control data.

[0145] Clause 26: A device according to Clause 14 where the camera control data is contained in the MPEG_mesh_collision extension.

[0146] Clause 27: A computer-readable storage medium having instructions stored thereon that, when executed, cause a processor executing a presentation engine to receive streamed media data representing a virtual three-dimensional scene including at least one virtual solid object; receive camera control data for the three-dimensional scene, the camera control data including data defining allowed locations for the virtual camera; receive camera movement data from a user requesting that the virtual camera move through the at least one virtual solid object; and update the location of the virtual camera using the camera control data to ensure that the virtual camera remains within the allowed location.

[0147] Clause 28: The computer-readable storage medium of clause 27, wherein the instructions for causing the processor to update a location of the virtual camera include instructions for causing the processor to prevent the virtual camera from passing through at least one virtual solid object.

[0148] Clause 29: The computer-readable medium of clause 27, wherein the streamed media data includes glTF 2.0 media data.

[0149] Clause 30: The computer-readable medium of clause 27, wherein the instructions for causing the processor to receive the streamed media data include instructions for causing the processor to request the streamed media data from the retrieval unit via an application programming interface (API).

[0150] Clause 31: The computer-readable medium of clause 27, wherein the camera control data is contained within an MPEG scene description.

[0151] Clause 32: The computer-readable medium of clause 27, wherein the camera control data includes data defining two or more anchor points and one or more segments between the anchor points, the segments representing permissible camera movement vectors for the virtual camera, and the instructions for causing the processor to update a location of the virtual camera include instructions for causing the processor to allow the virtual camera to traverse only the segments between the anchor points.

[0152] Clause 33: The computer-readable medium of clause 27, wherein the camera control data includes data defining a bounding volume representing an allowable camera movement volume for the virtual camera, and the instructions for causing the processor to update the location of the virtual camera include instructions for causing the processor to allow the virtual camera to traverse only the allowable camera movement volume.

[0153] Clause 34: The computer-readable medium of clause 20, wherein the data defining the bounding volume includes data defining at least one of a cone, a pyramid, or a sphere.

[0154] Clause 35: The computer-readable medium of clause 27, wherein the camera control data is contained within an MPEG_camera_control extension.

[0155] Clause 36: The computer-readable medium of clause 22, wherein the MPEG_camera_control extension includes one or more of anchor data representing a number of anchor points for an allowable path for the virtual camera, segment data representing a number of path segments for an allowable path between the anchor points, bounding volume data representing a bounding volume for the virtual camera, internal parameters indicating whether camera parameters are modified at each of the anchor points, and accessor data representing an index of an accessor that provides the camera control data.

[0156] Clause 37: The computer-readable medium of clause 27, wherein the at least one virtual solid object includes one of a virtual wall, a virtual chair, or a virtual table.

[0157] Clause 38: The computer-readable medium of clause 27, further comprising instructions for causing the processor to determine an allowable path for the virtual camera from the camera control data, and the instructions for causing the processor to update a location of the virtual camera include instructions for causing the processor to ensure that the virtual camera moves only along virtual paths that are within the allowable paths defined in the camera control data.

[0158] Clause 39: The computer-readable medium of clause 27, wherein the camera control data is included in an MPEG_mesh_collision extension.

[0159] Clause 40: A device for retrieving media data, the device comprising: means for receiving streamed media data representing a virtual three-dimensional scene including at least one virtual solid object; means for receiving camera control data for the three-dimensional scene, the camera control data including data defining allowed locations for the virtual camera; means for receiving camera movement data from a user requesting that the virtual camera move through the at least one virtual solid object; and means for using the camera control data to update a location of the virtual camera to ensure that the virtual camera remains within the allowed locations.

[0160] Clause 41: A method of retrieving media data, the method comprising the steps of: receiving, by a presentation engine, streamed media data representing a virtual three dimensional scene including at least one virtual solid object; receiving, by the presentation engine, object collision data representing a boundary of the at least one virtual solid object; receiving, by the presentation engine, camera movement data from a user requesting that a virtual camera move through the at least one virtual solid object; and in response to the camera movement data, using the object collision data, by the presentation engine to update a location of the virtual camera to ensure that the virtual camera remains outside the at least one virtual solid object.

[0161] Clause 42: The method of clause 41, wherein updating the location of the virtual camera includes preventing the virtual camera from passing through at least one virtual solid object.

[0162] Clause 43: The method of clause 41, wherein receiving the object collision data includes receiving an MPEG_mesh_collision extension.

[0163] Clause 44: The method of clause 43, wherein the MPEG_mesh_collision extension includes data defining at least one 3D mesh for at least one virtual solid object.

[0164] Clause 45: The method of clause 44, wherein the MPEG_mesh_collision extension includes data defining at least one of a boundary of a 3D mesh for at least one virtual solid object, a material for the 3D mesh, or an animation to be presented in response to the virtual camera contacting the 3D mesh.

[0165] Clause 46: The method of clause 41, wherein receiving the object collision data includes receiving data including one or more of boundary data representing one or more collision boundaries of the at least one virtual solid object, static data representing whether the at least one virtual solid object is affected by the collision, material data representing how the colliding object interacts with the at least one virtual solid object, or animation data representing an animation triggered by a collision with the at least one virtual solid object.

[0166] Clause 47: The method of clause 41, wherein the at least one virtual solid object includes one of a virtual wall, a virtual chair, or a virtual table.

[0167] Clause 48: The method of clause 41, wherein the streamed media data includes glTF 2.0 media data.

[0168] Clause 49: The method of clause 41, wherein receiving the streamed media data comprises requesting the streamed media data from the retrieval unit via an application programming interface (API).

[0169] Clause 50: The method of clause 41, wherein the object collision data is included in an MPEG scene description.

[0170] Clause 51: A device for retrieving media data, comprising: a memory configured to store the media data; and one or more processors implemented in circuitry and configured to execute a presentation engine, the one or more processors configured to: receive streamed media data representing a virtual three-dimensional scene including at least one virtual solid object; receive object collision data representing a boundary of the at least one virtual solid object; receive camera movement data from a user requesting that a virtual camera move through the at least one virtual solid object; and, in response to the camera movement data, use the object collision data to update a location of the virtual camera to ensure that the virtual camera remains outside the at least one virtual solid object.

[0171] Clause 52: The device of clause 51, wherein, to update a location of the virtual camera, the presentation engine is configured to prevent the virtual camera from passing through at least one virtual solid object.

[0172] Clause 53: The device of clause 51, wherein to receive the object collision data, the presentation engine is configured to receive an MPEG_mesh_collision extension.

[0173] Clause 54: The device of clause 53, wherein the MPEG_mesh_collision extension includes data defining at least one 3D mesh for at least one virtual solid object.

[0174] Clause 55: The device of clause 54, wherein the MPEG_mesh_collision extension includes data defining at least one of a boundary of a 3D mesh for at least one virtual solid object, a material for the 3D mesh, or an animation to be presented in response to the virtual camera contacting the 3D mesh.

[0175] Clause 56: The device of clause 51, wherein to receive the object collision data, the presentation engine is configured to receive data including one or more of boundary data representing one or more collision boundaries of the at least one virtual solid object, static data representing whether the at least one virtual solid object is affected by the collision, material data representing how the colliding object interacts with the at least one virtual solid object, or animation data representing an animation triggered by a collision with the at least one virtual solid object.

[0176] Clause 57: The device of clause 51, wherein the at least one virtual solid object includes one of a virtual wall, a virtual chair, or a virtual table.

[0177] Clause 58: The device of clause 51, wherein the streamed media data includes glTF 2.0 media data.

[0178] Clause 59: The device of clause 51, wherein to receive the streamed media data, the presentation engine is configured to request the streamed media data from the retrieval unit via an application programming interface (API).

[0179] Clause 60: A device according to clause 51, wherein the object collision data is included in an MPEG scene description.

[0180] Clause 61: A computer-readable storage medium having instructions stored thereon that, when executed, cause a processor to receive streamed media data representing a virtual three-dimensional scene including at least one virtual solid object; receive object collision data representing a boundary of the at least one virtual solid object; receive camera movement data from a user requesting that a virtual camera move through the at least one virtual solid object; and, in response to the camera movement data, use the object collision data to update a location of the virtual camera to ensure that the virtual camera remains outside the at least one virtual solid object.

[0181] Clause 62: The computer-readable medium of clause 61, wherein the instructions for causing the processor to update a location of the virtual camera include instructions for causing the processor to prevent the virtual camera from passing through at least one virtual solid object.

[0182] Clause 63: The computer-readable medium of clause 61, wherein the instructions for causing the processor to receive object collision data include instructions for causing the processor to receive an MPEG_mesh_collision extension.

[0183] Clause 64: The computer-readable medium of clause 62, wherein the MPEG_mesh_collision extension includes data defining at least one 3D mesh for at least one virtual solid object.

[0184] Clause 65: The computer-readable medium of clause 63, wherein the MPEG_mesh_collision extension includes data defining at least one of a boundary of a 3D mesh for at least one virtual solid object, a material for the 3D mesh, or an animation to be presented in response to the virtual camera contacting the 3D mesh.

[0185] Clause 66: The computer-readable medium of clause 61, wherein the instructions to cause the processor to receive object collision data include instructions to cause the processor to receive data including one or more of boundary data representing one or more collision boundaries of the at least one virtual solid object, static data representing whether the at least one virtual solid object is affected by a collision, material data representing how a colliding object interacts with the at least one virtual solid object, or animation data representing an animation triggered by a collision with the at least one virtual solid object.

[0186] Clause 67: The computer-readable medium of clause 61, wherein the at least one virtual solid object includes one of a virtual wall, a virtual chair, or a virtual table.

[0187] Clause 68: The computer-readable medium of clause 61, wherein the streamed media data includes glTF 2.0 media data.

[0188] Clause 69: The computer-readable medium of clause 61, wherein the instructions for causing the processor to receive the streamed media data include instructions for causing the processor to request the streamed media data from the retrieval unit via an application programming interface (API).

[0189] Clause 70: The computer-readable medium of clause 61, wherein the object collision data is contained within an MPEG scene description.

[0190] Clause 71: A device for retrieving media data, the device comprising: means for receiving streamed media data representing a virtual three-dimensional scene including at least one virtual solid object; means for receiving object collision data representing a boundary of the at least one virtual solid object; means for receiving camera movement data from a user requesting that a virtual camera move through the at least one virtual solid object; and means for updating a location of the virtual camera in response to the camera movement data to ensure that the virtual camera remains outside the at least one virtual solid object.

[0191] Clause 72: A method of retrieving media data, the method comprising the steps of: receiving, by a presentation engine, streamed media data representing a virtual three dimensional scene including at least one virtual solid object; receiving, by the presentation engine, camera control data for the three dimensional scene, the camera control data including data defining allowed locations for the virtual camera; receiving, by the presentation engine, camera movement data from a user requesting that the virtual camera move through the at least one virtual solid object; and updating, by the presentation engine, a location of the virtual camera using the camera control data to ensure that the virtual camera remains within the allowed locations.

[0192] Clause 73: The method of clause 72, wherein updating the location of the virtual camera includes preventing the virtual camera from passing through at least one virtual solid object.

[0193] Clause 74: The method of any of clauses 72 and 73, wherein the streamed media data includes glTF 2.0 media data.

[0194] Clause 75: The method of any of clauses 72 to 74, wherein receiving the streamed media data comprises requesting the streamed media data from the retrieval unit via an application programming interface (API).

[0195] Clause 76: The method of any of clauses 72 to 75, wherein the camera control data is included in an MPEG scene description.

[0196] Clause 77: Any of the methods of clauses 72 to 76, wherein the camera control data includes data defining two or more anchor points and one or more segments between the anchor points, the segments representing permissible camera movement vectors for the virtual camera, and wherein updating the location of the virtual camera includes allowing the virtual camera to traverse only the segments between the anchor points.

[0197] Clause 78: Any of clauses 72 to 77, wherein the camera control data includes data defining a bounding volume representing an allowable camera movement volume for the virtual camera, and the step of updating the location of the virtual camera includes a step of allowing the virtual camera to traverse only the allowable camera movement volume.

[0198] Clause 79: The method of clause 78, wherein the data defining the bounding volume includes data defining at least one of a cone, a pyramid, or a sphere.

[0199] Clause 80: The camera control data is included in the MPEG_camera_control extension, according to any of the methods of clauses 72 to 79.

[0200] Clause 81: The method of clause 80, wherein the MPEG_camera_control extension includes one or more of anchor data representing a number of anchor points for an allowable path for the virtual camera, segment data representing a number of path segments for an allowable path between the anchor points, bounding volume data representing a bounding volume for the virtual camera, internal parameters indicating whether camera parameters are modified at each of the anchor points, and accessor data representing an index of an accessor that provides the camera control data.

[0201] Clause 82: Any of the methods of clauses 72 to 81, wherein the at least one virtual solid object includes one of a virtual wall, a virtual chair, or a virtual table.

[0202] Clause 83: The method of clause 72, further comprising the step of determining an allowable path for the virtual camera from the camera control data, and wherein updating the location of the virtual camera includes ensuring that the virtual camera moves only along virtual paths that are within the allowable path defined in the camera control data.

[0203] Clause 84: The method of any of clauses 72 to 83, wherein the camera control data is included in the MPEG_mesh_collision extension.

[0204] Clause 85: A device for retrieving media data, comprising: a memory configured to store the media data; and one or more processors implemented in circuitry and configured to run a presentation engine, the presentation engine configured to: receive streamed media data representing a virtual three-dimensional scene including at least one virtual solid object; receive camera control data for the three-dimensional scene, the camera control data including data defining allowed locations for a virtual camera; receive camera movement data from a user requesting that the virtual camera move through the at least one virtual solid object; and use the camera control data to update a location of the virtual camera to ensure that the virtual camera remains within the allowed location.

[0205] Clause 86: The device of clause 85, wherein the presentation engine is configured to prevent the virtual camera from passing through at least one virtual solid object.

[0206] Clause 87: A device according to any of clauses 85 and 86, wherein the streamed media data includes glTF 2.0 media data.

[0207] Clause 88: The device of any of clauses 85 to 87, wherein the presentation engine is configured to request the streamed media data from the retrieval unit via an application programming interface (API).

[0208] Clause 89: The device of any of clauses 85 to 88, wherein the camera control data is included in an MPEG scene description.

[0209] Clause 90: A device of any of clauses 85 to 89, wherein the camera control data includes data defining two or more anchor points and one or more segments between the anchor points, the segments representing permissible camera movement vectors for the virtual camera, and wherein, to update a location of the virtual camera, the presentation engine is configured to allow the virtual camera to traverse only the segments between the anchor points.

[0210] Clause 91: A device of any of clauses 85 to 90, wherein the camera control data includes data defining a bounding volume representing an allowable camera movement volume for the virtual camera, and wherein, to update the location of the virtual camera, the presentation engine is configured to allow the virtual camera to traverse only the allowable camera movement volume.

[0211] Clause 92: The device of clause 91, wherein the data defining the bounding volume includes data defining at least one of a cone, a pyramid, or a sphere.

[0212] Clause 93: A device according to any of clauses 85 to 92, wherein the camera control data is contained in the MPEG_camera_control extension.

[0213] Clause 94: The device of clause 93, wherein the MPEG_camera_control extension includes one or more of anchor data representing a number of anchor points for an allowable path for the virtual camera, segment data representing a number of path segments for an allowable path between the anchor points, bounding volume data representing a bounding volume for the virtual camera, internal parameters indicating whether camera parameters are modified at each of the anchor points, and accessor data representing an index of an accessor providing the camera control data.

[0214] Clause 95: The device of any of clauses 85 to 94, wherein the at least one virtual solid object includes one of a virtual wall, a virtual chair, or a virtual table.

[0215] Clause 96: The device of any of clauses 85 to 95, wherein the presentation engine is further configured to determine from the camera control data an allowable path for the virtual camera, and wherein, to update a location of the virtual camera, the presentation engine is configured to ensure that the virtual camera moves only along virtual paths that are within the allowable paths defined in the camera control data.

[0216] Clause 97: A device according to any of clauses 85 to 96, wherein the camera control data is included in the MPEG_mesh_collision extension.

[0217] Clause 98: A computer-readable storage medium having instructions stored thereon that, when executed, cause a processor executing a presentation engine to receive streamed media data representing a virtual three-dimensional scene including at least one virtual solid object; receive camera control data for the three-dimensional scene, the camera control data including data defining allowed locations for the virtual camera; receive camera movement data from a user requesting that the virtual camera move through the at least one virtual solid object; and update the location of the virtual camera using the camera control data to ensure that the virtual camera remains within the allowed location.

[0218] Clause 99: The computer-readable storage medium of clause 98, wherein the instructions for causing the processor to update a location of the virtual camera include instructions for causing the processor to prevent the virtual camera from passing through at least one virtual solid object.

[0219] Clause 100: The computer-readable medium of any of clauses 98 and 99, wherein the streamed media data includes glTF2.0 media data.

[0220] Clause 101: The computer-readable medium of any of clauses 98 to 100, wherein the instructions for causing the processor to receive the streamed media data include instructions for causing the processor to request the streamed media data from a retrieval unit via an application programming interface (API).

[0221] Clause 102: The computer-readable medium of any of clauses 98 to 101, wherein the camera control data is contained within an MPEG scene description.

[0222] Clause 103: The computer-readable medium of any of clauses 98 to 102, wherein the camera control data includes data defining two or more anchor points and one or more segments between the anchor points, the segments representing permissible camera movement vectors for the virtual camera, and the instructions for causing the processor to update the location of the virtual camera include instructions for causing the processor to allow the virtual camera to traverse only the segments between the anchor points.

[0223] Clause 104: The computer-readable medium of clause 103, wherein the camera control data includes data defining a bounding volume representing an allowable camera movement volume for the virtual camera, and the instructions for causing the processor to update the location of the virtual camera include instructions for causing the processor to allow the virtual camera to traverse only the allowable camera movement volume.

[0224] Clause 105: The computer-readable medium of any of clauses 98 to 104, wherein the data defining the bounding volume includes data defining at least one of a cone, a pyramid, or a sphere.

[0225] Clause 106: The computer-readable medium of clause 105, wherein the camera control data is contained within an MPEG_camera_control extension.

[0226] Clause 107: The computer-readable medium of any of clauses 98 to 106, wherein the MPEG_camera_control extension includes one or more of anchor data representing a number of anchor points for an allowable path for the virtual camera, segment data representing a number of path segments for an allowable path between the anchor points, bounding volume data representing a bounding volume for the virtual camera, internal parameters indicating whether camera parameters are modified at each of the anchor points, and accessor data representing an index of an accessor that provides the camera control data.

[0227] Clause 108: The computer-readable medium of any of clauses 98 to 107, wherein the at least one virtual solid object includes one of a virtual wall, a virtual chair, or a virtual table.

[0228] Clause 109: The computer-readable medium of any of clauses 98 to 108, further comprising instructions for causing the processor to determine, from the camera control data, an allowable path for the virtual camera, and wherein the instructions for causing the processor to update the location of the virtual camera include instructions for causing the processor to ensure that the virtual camera moves only along virtual paths that are within the allowable paths defined in the camera control data.

[0229] Clause 110: The computer-readable medium of any of clauses 98 to 109, wherein the camera control data is included in an MPEG_mesh_collision extension.

[0230] Clause 111: A device for retrieving media data, the device comprising: means for receiving streamed media data representing a virtual three-dimensional scene including at least one virtual solid object; means for receiving camera control data for the three-dimensional scene, the camera control data including data defining allowed locations for the virtual camera; means for receiving camera movement data from a user requesting that the virtual camera move through the at least one virtual solid object; and means for using the camera control data to update a location of the virtual camera to ensure that the virtual camera remains within the allowed locations.

[0231] Clause 112: A method of retrieving media data, the method comprising the steps of: receiving, by a presentation engine, streamed media data representing a virtual three dimensional scene including at least one virtual solid object; receiving, by the presentation engine, object collision data representing a boundary of the at least one virtual solid object; receiving, by the presentation engine, camera movement data from a user requesting that a virtual camera move through the at least one virtual solid object; and in response to the camera movement data, using the object collision data, by the presentation engine to update a location of the virtual camera to ensure that the virtual camera remains outside the at least one virtual solid object.

[0232] Clause 113: A method comprising a combination of any of the methods of clauses 72 to 84 and the method of clause 112.

[0233] Clause 114: The method of any of clauses 112 and 113, wherein updating the location of the virtual camera includes preventing the virtual camera from passing through at least one virtual solid object.

[0234] Clause 115: The method of any of clauses 112 to 114, wherein receiving the object collision data includes receiving an MPEG_mesh_collision extension.

[0235] Clause 116: The method of clause 115, wherein the MPEG_mesh_collision extension includes data defining at least one 3D mesh for at least one virtual solid object.

[0236] Clause 117: The method of clause 116, wherein the MPEG_mesh_collision extension includes data defining at least one of a boundary of a 3D mesh for at least one virtual solid object, a material for the 3D mesh, or an animation to be presented in response to the virtual camera contacting the 3D mesh.

[0237] Clause 118: The method of any of clauses 112 to 117, wherein receiving the object collision data includes receiving data including one or more of boundary data representing one or more collision boundaries of the at least one virtual solid object, static data representing whether the at least one virtual solid object is affected by the collision, material data representing how the colliding object interacts with the at least one virtual solid object, or animation data representing an animation triggered by a collision with the at least one virtual solid object.

[0238] Clause 119: Any of the methods of clauses 112 to 118, wherein the at least one virtual solid object includes one of a virtual wall, a virtual chair, or a virtual table.

[0239] Clause 120: Any of the methods of clauses 112 to 119, wherein the streamed media data includes glTF 2.0 media data.

[0240] Clause 121: The method of any of clauses 112 to 120, wherein receiving the streamed media data includes requesting the streamed media data from the retrieval unit via an application programming interface (API).

[0241] Clause 122: Any of the methods of clauses 112 to 121, wherein the object collision data is included in the MPEG scene description.

[0242] Clause 123: A device for retrieving media data, comprising: a memory configured to store the media data; and one or more processors implemented in circuitry and configured to execute a presentation engine, the one or more processors configured to: receive streamed media data representing a virtual three-dimensional scene including at least one virtual solid object; receive object collision data representing a boundary of the at least one virtual solid object; receive camera movement data from a user requesting that a virtual camera move through the at least one virtual solid object; and, in response to the camera movement data, use the object collision data to update a location of the virtual camera to ensure that the virtual camera remains outside the at least one virtual solid object.

[0243] Clause 124: A device comprising a combination of any of the devices of clauses 85 to 97 and a device of clause 123.

[0244] Clause 125: The device of any of clauses 123 and 124, wherein, to update a location of the virtual camera, the presentation engine is configured to prevent the virtual camera from passing through at least one virtual solid object.

[0245] Clause 126: The device of any of clauses 123 to 125, wherein to receive the object collision data, the presentation engine is configured to receive an MPEG_mesh_collision extension.

[0246] Clause 127: The device of clause 126, wherein the MPEG_mesh_collision extension includes data defining at least one 3D mesh for at least one virtual solid object.

[0247] Clause 128: The device of clause 127, wherein the MPEG_mesh_collision extension includes data defining at least one of a boundary of a 3D mesh for at least one virtual solid object, a material for the 3D mesh, or an animation to be presented in response to the virtual camera contacting the 3D mesh.

[0248] Clause 129: The device of any of clauses 123 to 128, wherein to receive the object collision data, the presentation engine is configured to receive data including one or more of boundary data representing one or more collision boundaries of the at least one virtual solid object, static data representing whether the at least one virtual solid object is affected by the collision, material data representing how the colliding object interacts with the at least one virtual solid object, or animation data representing an animation triggered by a collision with the at least one virtual solid object.

[0249] Clause 130: The device of any of clauses 123 to 129, wherein the at least one virtual solid object includes one of a virtual wall, a virtual chair, or a virtual table.

[0250] Clause 131: A device according to any of clauses 123 to 130, wherein the streamed media data includes glTF 2.0 media data.

[0251] Clause 132: The device of any of clauses 123 to 131, wherein to receive the streamed media data, the presentation engine is configured to request the streamed media data from the retrieval unit via an application programming interface (API).

[0252] Clause 133: The device of any of clauses 123 to 132, wherein the object collision data is included in an MPEG scene description.

[0253] Clause 134: A computer-readable storage medium having instructions stored thereon that, when executed, cause a processor to receive streamed media data representing a virtual three-dimensional scene including at least one virtual solid object; receive object collision data representing a boundary of the at least one virtual solid object; receive camera movement data from a user requesting that a virtual camera move through the at least one virtual solid object; and, in response to the camera movement data, use the object collision data to update a location of the virtual camera to ensure that the virtual camera remains outside the at least one virtual solid object.

[0254] Clause 135: A computer-readable storage medium including a combination of any of the computer-readable storage media of clauses 98 to 110 and the computer-readable storage medium of clause 134.

[0255] Clause 136: The computer-readable medium of any of clauses 134 and 135, wherein the instructions for causing the processor to update the location of the virtual camera include instructions for causing the processor to prevent the virtual camera from passing through at least one virtual solid object.

[0256] Clause 137: The computer-readable medium of any of clauses 134 to 136, wherein the instructions for causing the processor to receive object collision data include instructions for causing the processor to receive an MPEG_mesh_collision extension.

[0257] Clause 138: The computer-readable medium of any of clauses 134 to 137, wherein the MPEG_mesh_collision extension includes data defining at least one 3D mesh for at least one virtual solid object.

[0258] Clause 139: The computer-readable medium of any of clauses 134 to 138, wherein the MPEG_mesh_collision extension includes data defining at least one of a boundary of a 3D mesh for at least one virtual solid object, a material for the 3D mesh, or an animation to be presented in response to the virtual camera contacting the 3D mesh.

[0259] Clause 140: The computer-readable medium of any of clauses 134 to 139, wherein the instructions to cause a processor to receive object collision data include instructions to cause the processor to receive data including one or more of boundary data representing one or more collision boundaries of the at least one virtual solid object, static data representing whether the at least one virtual solid object is affected by the collision, material data representing how the colliding object interacts with the at least one virtual solid object, or animation data representing an animation triggered by a collision with the at least one virtual solid object.

[0260] Clause 141: The computer-readable medium of any of clauses 134 to 140, wherein the at least one virtual solid object includes one of a virtual wall, a virtual chair, or a virtual table.

[0261] Clause 142: The computer-readable medium of any of clauses 134 to 141, wherein the streamed media data includes glTF2.0 media data.

[0262] Clause 143: The computer-readable medium of any of clauses 134 to 142, wherein the instructions for causing the processor to receive the streamed media data include instructions for causing the processor to request the streamed media data from the retrieval unit via an application programming interface (API).

[0263] Clause 144: The computer-readable medium of any of clauses 134 to 143, wherein the object collision data is contained within an MPEG scene description.

[0264] Clause 145: A method of retrieving media data comprising the steps of: receiving, by a presentation engine, streamed media data representing a virtual three dimensional scene including at least one virtual solid object; receiving, by the presentation engine, camera control data for the three dimensional scene, the camera control data including data defining constraints for preventing a virtual camera from passing through the at least one virtual solid object; receiving, by the presentation engine, camera movement data from a user requesting that the virtual camera move through the at least one virtual solid object; and in response to the camera movement data, using the camera control data to prevent the virtual camera from passing through the at least one virtual solid object.

[0265] Clause 146: The method of clause 145, wherein the streamed media data includes glTF 2.0 media data.

[0266] Clause 147: The method of any of clauses 145 and 146, wherein receiving the streamed media data includes requesting the streamed media data from the retrieval unit via an application programming interface (API).

[0267] Clause 148: The method of any of clauses 145 to 147, wherein the camera control data is included in an MPEG scene description.

[0268] Clause 149: The camera control data is included in the MPEG_camera_control extension, according to any of the methods of clauses 145 to 148.

[0269] Clause 150: The method of clause 149, wherein the MPEG_camera_control extension includes data defining two or more anchor points and one or more segments between the anchor points, the segments representing allowed camera movement vectors.

[0270] Clause 151: The method of any of clauses 149 and 150, wherein the MPEG_camera_control extension includes data defining a bounding volume representing the allowed camera movement volume.

[0271] Clause 152: The method of clause 151, wherein the data defining the bounding volume includes data defining at least one of a cone, a pyramid, or a sphere.

[0272] Clause 153: The MPEG_camera_control extension is any of the methods of clauses 149 to 152 that conform to the data in Table 1 above.

[0273] Clause 154: Any of clauses 149 to 153, wherein at least one virtual solid object includes a virtual wall.

[0274] Clause 155: Any of the methods of clauses 149 to 154, wherein preventing the virtual camera from passing through at least one virtual solid object includes preventing the virtual camera from moving along a virtual path that exceeds an allowed path defined in the MPEG_camera_control extension.

[0275] Clause 156: The method of any of clauses 145 to 155, wherein the camera control data is included in the MPEG_mesh_collision extension.

[0276] Clause 157: The method of clause 156, wherein the MPEG_mesh_collision extension includes data defining at least one 3D mesh for at least one virtual solid object.

[0277] Clause 158: The method of clause 157, wherein the MPEG_mesh_collision extension includes data defining at least one of a boundary of the 3D mesh, a material for the 3D mesh, or an animation to be presented in response to the virtual camera contacting the 3D mesh.

[0278] Clause 159: The MPEG_mesh_collision extension is in accordance with Table 2 above in any of the ways of clauses 156 to 158.

[0279] Clause 160: Any of the methods of clauses 156 to 159, wherein preventing the virtual camera from passing through at least one virtual solid object includes using an MPEG_mesh_collision extension to prevent the virtual camera from entering the at least one virtual solid object.

[0280] Clause 161: A device for retrieving media data, the device comprising one or more means for implementing the methods of any of clauses 145 to 160.

[0281] Clause 162: The device of clause 161, wherein the one or more means comprise one or more processors implemented in circuitry.

[0282] Clause 163: The device of clause 161, wherein the apparatus includes at least one of an integrated circuit, a microprocessor, and a wireless communication device.

[0283] Clause 164: A device for retrieving media data, the device comprising: means for receiving streamed media data representing a virtual three dimensional scene including at least one virtual solid object; means for receiving camera control data for the three dimensional scene, the camera control data including data defining constraints for preventing a virtual camera from passing through the at least one virtual solid object; means for receiving camera movement data from a user requesting that the virtual camera move through the at least one virtual solid object; and means for using the camera control data to prevent the virtual camera from passing through the at least one virtual solid object, in response to the camera movement data.

[0284] In one or more examples, the described functions may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on or transmitted via a computer-readable medium as one or more instructions or code and executed by a hardware-based processing unit. A computer-readable medium may include a computer-readable storage medium, which corresponds to a tangible medium, such as a data storage medium, or may include a communication medium, which includes any medium that facilitates the transfer of a computer program from one place to another, for example according to a communication protocol. As such, a computer-readable medium may generally correspond to (1) a non-transitory tangible computer-readable storage medium, or (2) a communication medium, such as a signal or carrier wave. A data storage medium may be any available medium that can be accessed by one or more computers or one or more processors to retrieve instructions, code, and / or data structures for implementation of the techniques described in this disclosure. A computer program product may include a computer-readable medium.

[0285] By way of example and not limitation, such computer-readable storage media may comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, flash memory, or any other medium that may be used to store desired program code in the form of instructions or data structures and that may be accessed by a computer. Also, any connection is properly referred to as a computer-readable medium. For example, if instructions are transmitted from a website, server, or other remote source using coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of the medium. However, it should be understood that computer-readable storage media and data storage media do not include connections, carrier waves, signals, or other transitory media, but instead cover non-transitory tangible storage media. Disk and disc, as used herein, include compact discs (CDs), laser discs, optical discs, digital versatile discs (DVDs), floppy disks, and Blu-ray discs, where disks typically reproduce data magnetically and discs reproduce data optically using lasers. Combinations of the above should also be included within the scope of computer readable media.

[0286] The instructions may be executed by one or more processors, such as one or more digital signal processors (DSPs), general-purpose microprocessors, application specific integrated circuits (ASICs), field programmable logic arrays (FPGAs), or other equivalent integrated or discrete logic circuitry. Thus, the term "processor" as used herein may refer to any of the above structures, or any other structure suitable for implementing the techniques described herein. In addition, in some aspects, the functionality described herein may be provided within dedicated hardware and / or software modules configured for encoding and decoding, or may be incorporated into a composite codec. Also, the techniques may be fully implemented in one or more circuits or logic elements.

[0287] The techniques of the present disclosure may be implemented in a wide variety of devices or apparatuses, including wireless handsets, integrated circuits (ICs) or sets of ICs (e.g., chipsets). Various components, modules, or units are described in the present disclosure to highlight functional aspects of devices configured to implement the disclosed techniques, but they do not necessarily require realization by different hardware units. Rather, as described above, the various units may be combined in a codec hardware unit or provided by a collection of interoperable hardware units, including one or more processors as described above, along with suitable software and / or firmware.

[0288] Various examples have been described. These and other examples are within the scope of the following claims. [Explanation of symbols]

[0289] 10. System 20 Content Preparation Devices 22 Audio Sources 24 Video Sources 26 Audio Encoder 28 Video Encoder 30 Encapsulation Units 32 Output Interface 40 client devices 42 Audio Output 44 Video Output 46 Audio Decoder 48 Video Decoder 50 Decapsulation Units 52 Removal unit 54 Network Interface 60 Server Devices 62 Storage medium 64 Multimedia Content 66 Manifest File 68 expression 68A~68N expression 70 Request Processing Unit 72 Network Interface 74 Network 100 eMBMS middleware units 102 Proxy Server Unit 104 Cache 106 eMBMS receiving unit 110 DASH Client 112 Media Applications 114 Presentation Engine 120 Multimedia Content 122 Media Presentation Description (MPD) 124 Expression 124A Expression 124N expression 126 Header Data 128 segments 128A~128N Segments 130 Header Data 132 segments 132A~132N Segment 150 Video files 152 File Type (FTYP) Box 154 Movie (MOOV) Box 156 Movie Header (MVHD) Box 158 TRAK BOX 160 Movie Extension (MVEX) Box 162 Segment Index (sidx) Box 164 Movie Fragment (MOOF) Box 166 Movie Fragment Random Access (MFRA) Box 202 Camera

Claims

1. 1. A method for retrieving media data, comprising: receiving, by a presentation engine, streamed media data representing a virtual three-dimensional scene including at least one virtual solid object; receiving, by the presentation engine, camera control data for the three-dimensional scene, the camera control data including data defining allowable locations for a virtual camera; receiving, by the presentation engine, camera movement data from a user requesting that the virtual camera move through the at least one virtual solid object; using the camera control data to update, by the presentation engine, the location of the virtual camera to ensure that the virtual camera remains within the permitted locations; The method includes:

2. The method of claim 1 , wherein updating the location of the virtual camera comprises preventing the virtual camera from passing through the at least one virtual solid object.

3. The method of claim 1 , wherein the streamed media data comprises glTF2.0 media data.

4. The method of claim 1 , wherein receiving the streamed media data comprises requesting the streamed media data from a retrieval unit via an application programming interface (API).

5. The method of claim 1 , wherein the camera control data is contained in an MPEG scene description.

6. 2. The method of claim 1 , wherein the camera control data includes data defining two or more anchor points and one or more segments between the anchor points, the segments representing permissible camera movement vectors for the virtual camera, and wherein updating the location of the virtual camera includes allowing the virtual camera to traverse only the segments between the anchor points.

7. 2. The method of claim 1 , wherein the camera control data includes data defining a bounding volume representing an allowable camera movement volume for the virtual camera, and updating the location of the virtual camera includes allowing the virtual camera to traverse only the allowable camera movement volume.

8. 1. A device for retrieving media data, comprising: a memory configured to store the media data; and one or more processors implemented in the circuitry and configured to execute a presentation engine, the presentation engine comprising: receiving streamed media data representing a virtual three-dimensional scene including at least one virtual solid object; receiving camera control data for the three-dimensional scene, the camera control data including data defining allowable locations for a virtual camera; receiving camera movement data from a user requesting that the virtual camera move through the at least one virtual solid object; using the camera control data to update the location of the virtual camera to ensure that the virtual camera remains within the permitted locations; A device configured to:

9. 10. The device of claim 8, wherein the presentation engine is configured to prevent the virtual camera from passing through the at least one virtual solid object.

10. The device of claim 8 , wherein the streamed media data comprises glTF2.0 media data.

11. 10. The device of claim 8, wherein the presentation engine is configured to request the streamed media data from a retrieval unit via an application programming interface (API).

12. The device of claim 8 , wherein the camera control data is contained in an MPEG scene description.

13. 9. The device of claim 8, wherein the camera control data includes data defining two or more anchor points and one or more segments between the anchor points, the segments representing permissible camera movement vectors for the virtual camera, and wherein, to update the location of the virtual camera, the presentation engine is configured to allow the virtual camera to traverse only the segments between the anchor points.

14. 9. The device of claim 8, wherein the camera control data includes data defining a bounding volume representing a permissible camera movement volume for the virtual camera, and wherein, to update the location of the virtual camera, the presentation engine is configured to allow the virtual camera to traverse only the permissible camera movement volume.

15. 8. A computer readable storage medium having stored thereon instructions which, when executed, cause a processor executing a presentation engine to perform the method of any one of claims 1 to 7.

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