Patent Description:
Digital video capabilities can 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 gaming devices, video game consoles, cellular or satellite radio telephones, video teleconferencing devices, and the like. Digital video devices implement video compression techniques, such as those described in the standards defined by MPEG-<NUM>, MPEG-<NUM>, ITU-T H. <NUM> or ITU-T H. <NUM> (also referred to High Efficiency Video Coding (HEVC)), and extensions of such standards, to transmit and receive digital video information more efficiently.

After media data has been encoded, the media data may be packetized for transmission or storage. The media data may be assembled into a video file conforming to any of a variety of standards, such as the International Organization for Standardization (ISO) base media file format and extensions thereof, such as AVC.

"<NPL>, <NPL>, "<NPL>, M39926 of <NUM> January <NUM> and <CIT> give examples of the use of ftyp and styp values as brands for files and segments in ISOBMFF or DASH.

In general, this disclosure describes techniques for using data types (e.g., segment types and file types) as delimiters, type indicators, and delivery indicators. These techniques may allow use of these data types in a flexible, simple fashion to provide any or all of these indications. In this manner, generated content may be used in different delivery and/or consumption environments, but also allow for packaging as discussed in greater detail below.

The scope of the present invention is defined by the scope of the appended claims.

In general, this disclosure describes techniques for using data types (e.g., segment types and/or file types) as delimiters, type indicators, and delivery indicators.

Dynamic Adaptive Streaming over HTTP (DASH) describes the use of segments as deliverable containers of media data (e.g., files with unique uniform resource locators (URLs)). Segments have a type, described by a "segment type" or "styp" syntax element. Files also have a file type, described by a "file type" or "ftyp" syntax element. Such syntax elements may form part of file format information according to, e.g., the ISO base media file format (ISO BMFF) or an extension of ISO BMFF.

A file conforming to ISO BMFF or an extension of ISO BMFF may further include media data formatted according to Common Media Application Format (CMAF). CMAF content is used in different stages: at the content preparation stage, at the delivery level, and at the content consumption stage (e.g., for an interface to a receiving device, such as a media source extension (MSE) interface).

In general, CMAF data structures are identified without a manifest file, such as a DASH media presentation description (MPD). After content preparation, delimiters are typically included in byte streams/files to identify the CMAF data structures. At the delivery level, types for delivered objects should be identifiable. As interfaces to playback engines, such as MSEs, data structures may be identified for extraction, e.g., to permit playback and switching across different CMAF tracks. In general, identification of CMAF data structures should be simple, and follow the CMAF structure.

The techniques of this disclosure may be applied to video files conforming to video data encapsulated according to any of ISO base media file format, Scalable Video Coding (SVC) file format, Advanced Video Coding (AVC) file format, Third Generation Partnership Project (3GPP) file format, and/or Multiview Video Coding (MVC) file format, or other similar video file formats.

In HTTP streaming, frequently used operations include HEAD, GET, and partial GET. The HEAD operation retrieves a header of a file associated with a given uniform resource locator (URL) or uniform resource name (URN), without retrieving a payload associated with the URL or URN. The GET operation retrieves a whole file associated with a given URL or URN. The partial GET operation receives a byte range as an input parameter and retrieves a continuous number of bytes of a file, where the number of bytes correspond to the received byte range. Thus, movie fragments may be provided for HTTP streaming, because a partial GET operation can get one or more individual movie fragments. In a movie fragment, there can be several track fragments of different tracks. In HTTP streaming, a media presentation may be a structured collection of data that is accessible to the client. The client may request and download media data information to present a streaming service to a user.

In the example of streaming 3GPP data using HTTP streaming, there may be multiple representations for video and/or audio data of multimedia content. As explained below, 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 coding standards (such as multiview and/or scalable extensions), or different bitrates. The manifest 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 that is accessible to an HTTP streaming client device. The HTTP streaming client device may 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 the MPD data structure, which may include updates of the MPD.

A media presentation may contain a sequence of one or more Periods. Each period may extend until the start of the next Period, or until the end of the media presentation, in the case of the last period. Each period may contain one or more representations for the same media content. A representation may be one of a number of alternative encoded versions of audio, video, timed text, or other such data. The representations may differ by encoding types, e.g., by bitrate, resolution, and/or codec for video data and bitrate, language, and/or codec for audio data. The term representation may be used to refer to a section of encoded audio or video data corresponding to a particular period of the multimedia content and encoded in a particular way.

Representations of a particular period may be assigned to a group indicated by an attribute in the MPD indicative of an adaptation set to which the representations belong. Representations in the same adaptation set are generally considered alternatives to each other, in that a client device can dynamically and seamlessly switch between these representations, e.g., to perform bandwidth adaptation. For example, each representation of video data for a particular period may be assigned to the same adaptation set, such 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 period. The media content within one period may be represented by either one representation from group <NUM>, if present, or the combination of at most one representation from each non-zero group, in some examples. Timing data for each representation of a period may be expressed relative to the start time of the period.

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. When present, the initialization segment may contain initialization information for accessing the representation. In general, the initialization segment does not contain 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 the identifiers for each segment. In some examples, the MPD may also provide byte ranges in the form of a range attribute, which may correspond to the data for a segment within a file accessible by the URL, URN, or URI.

Different representations may be selected for substantially simultaneous retrieval 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, the client device may select particular adaptation sets for performing bandwidth adaptation. That is, the client device may select an adaptation set including video representations, an adaptation set including audio representations, and/or an adaptation set including timed text. Alternatively, the client device may select adaptation sets for certain types of media (e.g., video), and directly select representations for other types of media (e.g., audio and/or timed text).

<FIG> is a block diagram illustrating an example system <NUM> that implements techniques for streaming media data over a network. In this example, system <NUM> includes content preparation device <NUM>, server device <NUM>, and client device <NUM>. Client device <NUM> and server device <NUM> are communicatively coupled by network <NUM>, which may comprise the Internet. In some examples, content preparation device <NUM> and server device <NUM> may also be coupled by network <NUM> or another network, or may be directly communicatively coupled. In some examples, content preparation device <NUM> and server device <NUM> may comprise the same device.

Content preparation device <NUM>, in the example of <FIG>, comprises audio source <NUM> and video source <NUM>. Audio source <NUM> may comprise, for example, a microphone that produces electrical signals representative of captured audio data to be encoded by audio encoder <NUM>. Alternatively, audio source <NUM> may comprise a storage medium storing previously recorded audio data, an audio data generator such as a computerized synthesizer, or any other source of audio data. Video source <NUM> may comprise a video camera that produces video data to be encoded by video encoder <NUM>, 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 <NUM> is not necessarily communicatively coupled to server device <NUM> in all examples, but may store multimedia content to a separate medium that is read by server device <NUM>.

Raw audio and video data may comprise analog or digital data. Analog data may be digitized before being encoded by audio encoder <NUM> and/or video encoder <NUM>. Audio source <NUM> may obtain audio data from a speaking participant while the speaking participant is speaking, and video source <NUM> may simultaneously obtain video data of the speaking participant. In other examples, audio source <NUM> may comprise a computer-readable storage medium comprising stored audio data, and video source <NUM> may comprise a computer-readable storage medium comprising stored video data. In this manner, 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.

Audio frames that correspond to video frames are generally audio frames containing audio data that was captured (or generated) by audio source <NUM> contemporaneously with video data captured (or generated) by video source <NUM> that is contained within the video frames. For example, while a speaking participant generally produces audio data by speaking, audio source <NUM> captures the audio data, and video source <NUM> captures video data of the speaking participant at the same time, that is, while audio source <NUM> is capturing the audio data. Hence, an audio frame may temporally correspond to one or more particular video frames. Accordingly, an audio frame corresponding to a video frame generally corresponds to a situation in which audio data and video data were captured at the same time and for which an audio frame and a video frame comprise, respectively, the audio data and the video data that was captured at the same time.

In some examples, audio encoder <NUM> may encode a timestamp in each encoded audio frame that represents a time at which the audio data for the encoded audio frame was recorded, and similarly, video encoder <NUM> may encode a timestamp in each encoded video frame that represents a time at which the video data for encoded video frame was recorded. In such examples, an audio frame corresponding to a video frame may comprise an audio frame comprising a timestamp and a video frame comprising the same timestamp. Content preparation device <NUM> may include an internal clock from which audio encoder <NUM> and/or video encoder <NUM> may generate the timestamps, or that audio source <NUM> and video source <NUM> may use to associate audio and video data, respectively, with a timestamp.

In some examples, audio source <NUM> may send data to audio encoder <NUM> corresponding to a time at which audio data was recorded, and video source <NUM> may send data to video encoder <NUM> corresponding to a time at which video data was recorded. In some examples, audio encoder <NUM> may encode a sequence identifier in encoded audio data to indicate a relative temporal ordering of encoded audio data but without necessarily indicating an absolute time at which the audio data was recorded, and similarly, video encoder <NUM> may also use sequence identifiers to indicate a relative temporal ordering of encoded video data. Similarly, in some examples, a sequence identifier may be mapped or otherwise correlated with a timestamp.

Audio encoder <NUM> generally produces a stream of encoded audio data, while video encoder <NUM> produces 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 part of the representation can 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 the PES-packets belonging to one elementary stream from the other. The basic unit of data of an elementary stream is a packetized elementary stream (PES) packet. Thus, coded video data generally corresponds to elementary video streams. Similarly, audio data corresponds to one or more respective elementary streams.

Many video coding standards, such as ITU-T H. <NUM>/AVC and the upcoming High Efficiency Video Coding (HEVC) standard, define the syntax, semantics, and decoding process for error-free bitstreams, any of which conform to a certain profile or level. Video coding standards typically do not specify the encoder, but the encoder is tasked with guaranteeing that the generated bitstreams are standard-compliant for a decoder. In the context of video coding standards, a "profile" corresponds to a subset of algorithms, features, or tools and constraints that apply to them. As defined by the H. <NUM> standard, for example, a "profile" is a subset of the entire bitstream syntax that is specified by the H. <NUM> standard. A "level" corresponds to the limitations of the decoder resource consumption, such as, for example, decoder memory and computation, which are related to the resolution of the pictures, bit rate, and block processing rate. A profile may be signaled with a profile_idc (profile indicator) value, while a level may be signaled with a level_idc (level indicator) value.

<NUM> standard, for example, recognizes that, within the bounds imposed by the syntax of a given profile, it is still possible to require a large variation in the performance of encoders and decoders depending upon the values taken by syntax elements in the bitstream such as the specified size of the decoded pictures. <NUM> standard further recognizes that, in many applications, it is neither practical nor economical to implement a decoder capable of dealing with all hypothetical uses of the syntax within a particular profile. Accordingly, the H. <NUM> standard defines a "level" as a specified set of constraints imposed on values of the syntax elements in the bitstream. These constraints may be simple limits on values. Alternatively, these constraints may take the form of constraints on arithmetic combinations of values (e.g., picture width multiplied by picture height multiplied by number of pictures decoded per second). <NUM> standard further provides that individual implementations may support a different level for each supported profile.

A decoder conforming to a profile ordinarily supports all the features defined in the profile. For example, as a coding feature, B-picture coding is not supported in the baseline profile of H. <NUM>/AVC but is supported in other profiles of H. A decoder conforming to a level should be capable of decoding any bitstream that does not require resources beyond the limitations defined in the level. Definitions of profiles and levels may be helpful for interpretability. For example, during video transmission, a pair of profile and level definitions may be negotiated and agreed for a whole transmission session. More specifically, in H. <NUM>/AVC, a level may define limitations on the number of macroblocks that need to be processed, decoded picture buffer (DPB) size, coded picture buffer (CPB) size, vertical motion vector range, maximum number of motion vectors per two consecutive MBs, and whether a B-block can have sub-macroblock partitions less than 8x8 pixels. In this manner, a decoder may determine whether the decoder is capable of properly decoding the bitstream.

In the example of <FIG>, encapsulation unit <NUM> of content preparation device <NUM> receives elementary streams comprising coded video data from video encoder <NUM> and elementary streams comprising coded audio data from audio encoder <NUM>. In some examples, video encoder <NUM> and audio encoder <NUM> may each include packetizers for forming PES packets from encoded data. In other examples, video encoder <NUM> and audio encoder <NUM> may each interface with respective packetizers for forming PES packets from encoded data. In still other examples, encapsulation unit <NUM> may include packetizers for forming PES packets from encoded audio and video data.

Video encoder <NUM> may encode video data of multimedia content in a variety of ways, to produce different representations of the multimedia content at various bitrates and with various characteristics, such as pixel resolutions, frame rates, conformance to various coding standards, conformance to various profiles and/or levels of profiles for various coding standards, representations having one or multiple views (e.g., for two-dimensional or three-dimensional playback), or other such characteristics. A representation, as used in this disclosure, may comprise one of audio data, video data, text data (e.g., for closed captions), 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. Encapsulation unit <NUM> is responsible for assembling elementary streams into video files (e.g., segments) of various representations.

Encapsulation unit <NUM> receives PES packets for elementary streams of a representation from audio encoder <NUM> and video encoder <NUM> and forms corresponding network abstraction layer (NAL) units from the PES packets. Coded video segments may be organized into NAL units, which provide a "network-friendly" video representation addressing applications such as video telephony, storage, broadcast, or streaming. NAL units can be categorized to Video Coding Layer (VCL) NAL units and non-VCL NAL units. VCL units may contain the core compression engine and may include block, macroblock, and/or slice level data. Other NAL units may be non-VCL NAL units. In some examples, a coded picture in one time instance, normally presented as a primary coded picture, may be contained in an access unit, which may include one or more NAL units.

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 the infrequently changing picture-level header information (in picture parameter sets (PPS)). With parameter sets (e.g., PPS and SPS), infrequently changing information need not to be repeated for each sequence or picture, hence coding efficiency may be improved. Furthermore, the use of parameter sets may enable out-of-band transmission of the important header information, avoiding the need for redundant transmissions for error resilience. In out-of-band transmission examples, parameter set NAL units may be transmitted on a different channel than other NAL units, such as SEI NAL units.

Supplemental Enhancement Information (SEI) may contain information that is not necessary for decoding the coded pictures samples from VCL NAL units, but may assist in processes related to decoding, display, error resilience, and other purposes. SEI messages may be contained in non-VCL NAL units. SEI messages are the normative part of some standard specifications, and thus are not always mandatory for standard compliant decoder implementation. SEI messages may be sequence level SEI messages or picture level SEI messages. Some sequence level information may be contained in SEI messages, such as scalability information SEI messages in the example of SVC and view scalability information SEI messages in MVC. These example SEI messages may convey information on, e.g., extraction of operation points and characteristics of the operation points. In addition, encapsulation unit <NUM> may form a manifest file, such as a media presentation descriptor (MPD) that describes characteristics of the representations. Encapsulation unit <NUM> may format the MPD according to extensible markup language (XML).

Encapsulation unit <NUM> may provide data for one or more representations of multimedia content, along with the manifest file (e.g., the MPD) to output interface <NUM>. Output interface <NUM> may comprise a network interface or an interface for writing to a storage medium, such as a universal serial bus (USB) interface, a CD or DVD writer or burner, an interface to magnetic or flash storage media, or other interfaces for storing or transmitting media data. Encapsulation unit <NUM> may provide data of each of the representations of multimedia content to output interface <NUM>, which may send the data to server device <NUM> via network transmission or storage media. In the example of <FIG>, server device <NUM> includes storage medium <NUM> that stores various multimedia contents <NUM>, each including a respective manifest file <NUM> and one or more representations 68A-68N (representations <NUM>). In some examples, output interface <NUM> may also send data directly to network <NUM>.

In some examples, representations <NUM> may be separated into adaptation sets. That is, various subsets of representations <NUM> may include respective common sets of characteristics, such as codec, profile and level, resolution, number of views, file format for segments, text type information that may identify a language or other characteristics of text to be displayed with the representation and/or audio data to be decoded and presented, e.g., by speakers, camera angle information that may describe a camera angle or real-world camera perspective of a scene for representations in the adaptation set, rating information that describes content suitability for particular audiences, or the like.

Manifest file <NUM> may include data indicative of the subsets of representations <NUM> corresponding to particular adaptation sets, as well as common characteristics for the adaptation sets. Manifest file <NUM> may also include data representative of individual characteristics, such as bitrates, for individual representations of adaptation sets. In this manner, an adaptation set may provide for simplified network bandwidth adaptation. Representations in an adaptation set may be indicated using child elements of an adaptation set element of manifest file <NUM>.

Server device <NUM> includes request processing unit <NUM> and network interface <NUM>. In some examples, server device <NUM> may include a plurality of network interfaces. Furthermore, any or all of the features of server device <NUM> may be implemented on other devices of a content delivery network, such as routers, bridges, proxy devices, switches, or other devices. In some examples, intermediate devices of a content delivery network may cache data of multimedia content <NUM>, and include components that conform substantially to those of server device <NUM>. In general, network interface <NUM> is configured to send and receive data via network <NUM>.

Request processing unit <NUM> is configured to receive network requests from client devices, such as client device <NUM>, for data of storage medium <NUM>. For example, request processing unit <NUM> may implement hypertext transfer protocol (HTTP) version <NUM>, as described in RFC <NUM>, "<NPL>. That is, request processing unit <NUM> may be configured to receive HTTP GET or partial GET requests and provide data of multimedia content <NUM> in response to the requests. The requests may specify a segment of one of representations <NUM>, e.g., using a URL of the segment. In some examples, the requests may also specify one or more byte ranges of the segment, thus comprising partial GET requests. Request processing unit <NUM> may further be configured to service HTTP HEAD requests to provide header data of a segment of one of representations <NUM>. In any case, request processing unit <NUM> may be configured to process the requests to provide requested data to a requesting device, such as client device <NUM>.

Additionally or alternatively, request processing unit <NUM> may be configured to deliver media data via a broadcast or multicast protocol, such as eMBMS. Content preparation device <NUM> may create DASH segments and/or sub-segments in substantially the same way as described, but server device <NUM> may deliver these segments or sub-segments using eMBMS or another broadcast or multicast network transport protocol. For example, request processing unit <NUM> may be configured to receive a multicast group join request from client device <NUM>. That is, server device <NUM> may advertise an Internet protocol (IP) address associated with a multicast group to client devices, including client device <NUM>, associated with particular media content (e.g., a broadcast of a live event). Client device <NUM>, in turn, may submit a request to join the multicast group. This request may be propagated throughout network <NUM>, e.g., routers making up network <NUM>, such that the routers are caused to direct traffic destined for the IP address associated with the multicast group to subscribing client devices, such as client device <NUM>.

As illustrated in the example of <FIG>, multimedia content <NUM> includes manifest file <NUM>, which may correspond to a media presentation description (MPD). Manifest file <NUM> may contain descriptions of different alternative representations <NUM> (e.g., video services with different qualities) and the description may include, e.g., codec information, a profile value, a level value, a bitrate, and other descriptive characteristics of representations <NUM>. Client device <NUM> may retrieve the MPD of a media presentation to determine how to access segments of representations <NUM>.

In particular, retrieval unit <NUM> may retrieve configuration data (not shown) of client device <NUM> to determine decoding capabilities of video decoder <NUM> and rendering capabilities of video output <NUM>. The configuration data may also include any or all of a language preference selected by a user of client device <NUM>, one or more camera perspectives corresponding to depth preferences set by the user of client device <NUM>, and/or a rating preference selected by the user of client device <NUM>. Retrieval unit <NUM> may comprise, for example, a web browser or a media client configured to submit HTTP GET and partial GET requests. Retrieval unit <NUM> may correspond to software instructions executed by one or more processors or processing units (not shown) of client device <NUM>. In some examples, all or portions of the functionality described with respect to retrieval unit <NUM> may be implemented in hardware, or a combination of hardware, software, and/or firmware, where requisite hardware may be provided to execute instructions for software or firmware.

Retrieval unit <NUM> may compare the decoding and rendering capabilities of client device <NUM> to characteristics of representations <NUM> indicated by information of manifest file <NUM>. Retrieval unit <NUM> may initially retrieve at least a portion of manifest file <NUM> to determine characteristics of representations <NUM>. For example, retrieval unit <NUM> may request a portion of manifest file <NUM> that describes characteristics of one or more adaptation sets. Retrieval unit <NUM> may select a subset of representations <NUM> (e.g., an adaptation set) having characteristics that can be satisfied by the coding and rendering capabilities of client device <NUM>. Retrieval unit <NUM> may then determine bitrates for representations in the adaptation set, determine a currently available amount of network bandwidth, and retrieve segments from one of the representations having a bitrate that can be satisfied by the network bandwidth.

In general, higher bitrate representations may yield higher quality video playback, while lower bitrate representations may provide sufficient quality video playback when available network bandwidth decreases. Accordingly, when available network bandwidth is relatively high, retrieval unit <NUM> may retrieve data from relatively high bitrate representations, whereas when available network bandwidth is low, retrieval unit <NUM> may retrieve data from relatively low bitrate representations. In this manner, client device <NUM> may stream multimedia data over network <NUM> while also adapting to changing network bandwidth availability of network <NUM>.

Additionally or alternatively, retrieval unit <NUM> may be configured to receive data in accordance with a broadcast or multicast network protocol, such as eMBMS or IP multicast. In such examples, retrieval unit <NUM> may submit a request to join a multicast network group associated with particular media content. After joining the multicast group, retrieval unit <NUM> may receive data of the multicast group without further requests issued to server device <NUM> or content preparation device <NUM>. Retrieval unit <NUM> may submit a request to leave the multicast group when data of the multicast group is no longer needed, e.g., to stop playback or to change channels to a different multicast group.

Network interface <NUM> may receive and provide data of segments of a selected representation to retrieval unit <NUM>, which may in turn provide the segments to decapsulation unit <NUM>. Decapsulation unit <NUM> may decapsulate elements of a video file into constituent PES streams, depacketize the PES streams to retrieve encoded data, and send the encoded data to either audio decoder <NUM> or video decoder <NUM>, depending on whether the encoded data is part of an audio or video stream, e.g., as indicated by PES packet headers of the stream. Audio decoder <NUM> decodes encoded audio data and sends the decoded audio data to audio output <NUM>, while video decoder <NUM> decodes encoded video data and sends the decoded video data, which may include a plurality of views of a stream, to video output <NUM>.

Video encoder <NUM>, video decoder <NUM>, audio encoder <NUM>, audio decoder <NUM>, encapsulation unit <NUM>, retrieval unit <NUM>, and decapsulation unit <NUM> each may be implemented as any of a variety of suitable processing circuitry, as applicable, such as 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 combinations thereof. Each of video encoder <NUM> and video decoder <NUM> may be included in one or more encoders or decoders, either of which may be integrated as part of a combined video encoder/decoder (CODEC). Likewise, each of audio encoder <NUM> and audio decoder <NUM> may be included in one or more encoders or decoders, either of which may be integrated as part of a combined CODEC. An apparatus including video encoder <NUM>, video decoder <NUM>, audio encoder <NUM>, audio decoder <NUM>, encapsulation unit <NUM>, retrieval unit <NUM>, and/or decapsulation unit <NUM> may comprise an integrated circuit, a microprocessor, and/or a wireless communication device, such as a cellular telephone.

Client device <NUM>, server device <NUM>, and/or content preparation device <NUM> may be configured to operate in accordance with the techniques of this disclosure. For purposes of example, this disclosure describes these techniques with respect to client device <NUM> and server device <NUM>. However, it should be understood that content preparation device <NUM> may be configured to perform these techniques, instead of (or in addition to) server device <NUM>.

Encapsulation unit <NUM> may form NAL units comprising a header that identifies a 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. <NUM>/AVC, a NAL unit includes a <NUM>-byte header and a payload of varying size. A NAL unit including video data in its payload may comprise various granularity levels of video data. For example, a NAL unit may comprise a block of video data, a plurality of blocks, a slice of video data, or an entire picture of video data. Encapsulation unit <NUM> may receive encoded video data from video encoder <NUM> in the form of PES packets of elementary streams. Encapsulation unit <NUM> may associate each elementary stream with a corresponding program.

Encapsulation unit <NUM> may also assemble access units from a plurality of NAL units. In general, an access unit may comprise one or more NAL units for representing a frame of video data, as well 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 and video data for one time instance. For example, if each view has a frame rate of <NUM> frames per second (fps), then each time instance may correspond to a time interval of <NUM> seconds. During this time interval, the specific frames for all views of the same access unit (the same time instance) may be rendered simultaneously. In one example, an access unit may comprise a coded picture in one time instance, which may be presented as a primary coded picture.

Accordingly, an access unit may comprise all audio and video frames of a common temporal instance, e.g., all views corresponding to time X. This disclosure also refers to an encoded picture of a particular view as a "view component. " That is, a view component may comprise an encoded picture (or frame) for a particular view at a particular time. Accordingly, an access unit may be defined as comprising all view components of a common temporal instance. The decoding order of access units need not necessarily be the same as the output or display order.

A media presentation may include a media presentation description (MPD), which may contain descriptions of different alternative representations (e.g., video services with different qualities) and the description may include, e.g., codec information, a profile value, and a level value. An MPD is one example of a manifest file, such as manifest file <NUM>. Client device <NUM> may retrieve the MPD of a media presentation to determine how to access movie fragments of various presentations. Movie fragments may be located in movie fragment boxes (moof boxes) of video files.

Manifest file <NUM> (which may comprise, for example, an MPD) may advertise availability of segments of representations <NUM>. That is, the MPD may include information indicating the wall-clock time at which a first segment of one of representations <NUM> becomes available, as well as information indicating the durations of segments within representations <NUM>. In this manner, retrieval unit <NUM> of client device <NUM> may determine when each segment is available, based on the starting time as well as the durations of the segments preceding a particular segment.

After encapsulation unit <NUM> has assembled NAL units and/or access units into a video file based on received data, encapsulation unit <NUM> passes the video file to output interface <NUM> for output. In some examples, encapsulation unit <NUM> may store the video file locally or send the video file to a remote server via output interface <NUM>, rather than sending the video file directly to client device <NUM>. Output interface <NUM> may comprise, 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., floppy drive), a universal serial bus (USB) port, a network interface, or other output interface. Output interface <NUM> 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.

Network interface <NUM> may receive a NAL unit or access unit via network <NUM> and provide the NAL unit or access unit to decapsulation unit <NUM>, via retrieval unit <NUM>. Decapsulation unit <NUM> may decapsulate a elements of a video file into constituent PES streams, depacketize the PES streams to retrieve encoded data, and send the encoded data to either audio decoder <NUM> or video decoder <NUM>, depending on whether the encoded data is part of an audio or video stream, e.g., as indicated by PES packet headers of the stream. Audio decoder <NUM> decodes encoded audio data and sends the decoded audio data to audio output <NUM>, while video decoder <NUM> decodes encoded video data and sends the decoded video data, which may include a plurality of views of a stream, to video output <NUM>.

In accordance with the techniques of this disclosure, encapsulation unit <NUM> may use a single type of signaling for a variety of purposes, e.g., any or all of a content preparation stage, delivery level, and/or a content consumption stage. Likewise, retrieval unit <NUM> may use this single type of signaling for any or all of these purposes.

In one example, the single type of signaling is a file type (ftyp) box that includes a value acting as an identifier for one or more CMAF tracks. Thus, encapsulation unit <NUM> may set a value for the ftyp box, and retrieval unit <NUM> may read a value for the ftyp box. Additionally, request processing unit <NUM> may also read the value for the ftyp box. These components may use the value of the ftyp box during any or all of content preparation, delivery, and/or content consumption.

Additionally, the single type of signaling may be a segment type (styp) box that includes a value acting as an identifier for one or more CMAF tracks. The styp box may act as a delimiter to identify boundaries of CMAF fragments and/or chunks, identifiers for CMAF data structures, identifiers for DASH segments (or segments for other network streaming technologies), and/or as identifiers for processing requirements. Thus, encapsulation unit <NUM> may specify values for one or more styp boxes of a segment to represent any or all of boundaries of CMAF fragments and/or chunks of the segment, identifiers for CMAF data structures of the segment, an identifier for the DASH segment, and/or as identifiers for processing requirements for media data of the segment.

Table <NUM> below represents example "brands" of type values in accordance with the techniques of this disclosure, including locations of each brand type and example conformance requirements:.

Tables <NUM>-<NUM> below represent additional example data structures that may be used in accordance with the techniques of this disclosure:.

With respect to delivery and consumption, in some examples, ftyp and styp provide indications of the compatibility of the type and how the type can be used. The box may be at the start of the object, and therefore, easy to find and parse (e.g., by retrieval unit <NUM> and/or decapsulation unit <NUM>). Multiple compatibility types may be used to signal different types. The type of the box may also be exposed as an Internet Media type using the profiles parameter and, for example, be used in the HTTP case (e.g., for DASH streaming or other HTTP streaming technologies). This may enable different distribution modes.

With respect to use of types as delimiters, the type values may delimit chunks in fragments, delimit fragments in segments and track files, and/or delimit ranges to provide proper interpretation. The delimiter (e.g., type value) may also represent types, in order for a receiving element (e.g., retrieval unit <NUM> and/or decapsulation unit <NUM>) to determine the type of data (e.g., media data) included in the chunk, fragment, segment, track file, or the like. No indices of subsequent fields are necessary, and hence, these techniques may support real-time processing.

<FIG> is a block diagram illustrating an example set of components of retrieval unit <NUM> of <FIG> in greater detail. In this example, retrieval unit <NUM> includes eMBMS middleware unit <NUM>, DASH client <NUM>, and media application <NUM>.

In the example of <FIG>, eMBMS middleware unit <NUM> further includes eMBMS reception unit <NUM>, cache <NUM>, and server unit <NUM>. In this example, eMBMS reception unit <NUM> is configured to receive data via eMBMS, e.g., according to File Delivery over Unidirectional Transport (FLUTE), described in <NPL>. That is, eMBMS reception unit <NUM> may receive files via broadcast from, e.g., server device <NUM>, which may act as a BM-SC.

As eMBMS middleware unit <NUM> receives data for files, eMBMS middleware unit may store the received data in cache <NUM>. Cache <NUM> may comprise a computer-readable storage medium, such as flash memory, a hard disk, RAM, or any other suitable storage medium.

Local server unit <NUM> may act as a server for DASH client <NUM>. For example, local server unit <NUM> may provide a MPD file or other manifest file to DASH client <NUM>. Local server unit <NUM> may advertise availability times for segments in the MPD file, as well as hyperlinks from which the segments can be retrieved. These hyperlinks may include a localhost address prefix corresponding to client device <NUM> (e.g., <NUM>. <NUM> for IPv4). In this manner, DASH client <NUM> may request segments from local server unit <NUM> using HTTP GET or partial GET requests. For example, for a segment available from link http://<NUM>. <NUM>/rep1/seg3, DASH client <NUM> may construct an HTTP GET request that includes a request for http://<NUM>. <NUM>/rep1/seg3, and submit the request to local server unit <NUM>. Local server unit <NUM> may retrieve requested data from cache <NUM> and provide the data to DASH client <NUM> in response to such requests.

<FIG> is a conceptual diagram illustrating elements of example multimedia content <NUM>. Multimedia content <NUM> may correspond to multimedia content <NUM> (<FIG>), or another multimedia content stored in storage medium <NUM>. In the example of <FIG>, multimedia content <NUM> includes media presentation description (MPD) <NUM> and a plurality of representations 124A-124N (representations <NUM>). Representation 124A includes optional header data <NUM> and segments 128A-128N (segments <NUM>), while representation 124N includes optional header data <NUM> and segments 132A-132N (segments <NUM>). The letter N is used to designate the last movie fragment in each of representations <NUM> as a matter of convenience. In some examples, there may be different numbers of movie fragments between representations <NUM>.

MPD <NUM> may comprise a data structure separate from representations <NUM>. MPD <NUM> may correspond to manifest file <NUM> of <FIG>. Likewise, representations <NUM> may correspond to representations <NUM> of <FIG>. In general, MPD <NUM> may include data that generally describes characteristics of representations <NUM>, such as coding and rendering characteristics, adaptation sets, a profile to which MPD <NUM> corresponds, text type information, camera angle information, rating information, trick mode information (e.g., information indicative of representations that include temporal sub-sequences), and/or information for retrieving remote periods (e.g., for targeted advertisement insertion into media content during playback).

Header data <NUM>, when present, may describe characteristics of segments <NUM>, e.g., temporal locations of random access points (RAPs, also referred to as stream access points (SAPs)), which of segments <NUM> includes random access points, byte offsets to random access points within segments <NUM>, uniform resource locators (URLs) of segments <NUM>, or other aspects of segments <NUM>. Header data <NUM>, when present, may describe similar characteristics for segments <NUM>. Additionally or alternatively, such characteristics may be fully included within MPD <NUM>.

Segments <NUM>, <NUM> include one or more coded video samples, each of which may include frames or slices of video data. Each of the coded video samples of segments <NUM> may have similar characteristics, e.g., height, width, and bandwidth requirements. Such characteristics may be described by data of MPD <NUM>, though such data is not illustrated in the example of <FIG>. MPD <NUM> may include characteristics as described by the 3GPP Specification, with the addition of any or all of the signaled information described in this disclosure.

Each of segments <NUM>, <NUM> may be associated with a unique uniform resource locator (URL). Thus, each of segments <NUM>, <NUM> may be independently retrievable using a streaming network protocol, such as DASH. In this manner, a destination device, such as client device <NUM>, may use an HTTP GET request to retrieve segments <NUM> or <NUM>. In some examples, client device <NUM> may use HTTP partial GET requests to retrieve specific byte ranges of segments <NUM> or <NUM>.

<FIG> is a block diagram illustrating elements of an example video file <NUM>, which may correspond to a segment of a representation, such as one of segments <NUM>, <NUM> of <FIG>. Each of segments <NUM>, <NUM> may include data that conforms substantially to the arrangement of data illustrated in the example of <FIG>. Video file <NUM> may be said to encapsulate a segment. As described above, video files in accordance with the ISO base media file format and extensions thereof store data in a series of objects, referred to as "boxes. " In the example of <FIG>, video file <NUM> includes file type (FTYP) box <NUM>, movie (MOOV) box <NUM>, segment index (sidx) boxes <NUM>, movie fragment (MOOF) boxes <NUM>, and movie fragment random access (MFRA) box <NUM>. Although <FIG> represents an example of a video file, it should be understood that other media files may include other types of media data (e.g., audio data, timed text data, or the like) that is structured similarly to the data of video file <NUM>, in accordance with the ISO base media file format and its extensions.

File type (FTYP) box <NUM> generally describes a file type for video file <NUM>. File type box <NUM> may include data that identifies a specification that describes a best use for video file <NUM>. File type box <NUM> may alternatively be placed before MOOV box <NUM>, movie fragment boxes <NUM>, and/or MFRA box <NUM>.

In some examples, a Segment, such as video file <NUM>, may include an MPD update box (not shown) before FTYP box <NUM>. The MPD update box may include information indicating that an MPD corresponding to a representation including video file <NUM> is to be updated, along with information for updating the MPD. For example, the MPD update box may provide a URI or URL for a resource to be 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 <NUM>, where the STYP box may define a segment type for video file <NUM>. <FIG>, discussed in greater detail below, provides additional information with respect to the MPD update box.

MOOV box <NUM>, in the example of <FIG>, includes movie header (MVHD) box <NUM>, track (TRAK) box <NUM>, and one or more movie extends (MVEX) boxes <NUM>. In general, MVHD box <NUM> may describe general characteristics of video file <NUM>. For example, MVHD box <NUM> may include data that describes when video file <NUM> was originally created, when video file <NUM> was last modified, a timescale for video file <NUM>, a duration of playback for video file <NUM>, or other data that generally describes video file <NUM>.

TRAK box <NUM> may include data for a track of video file <NUM>. TRAK box <NUM> may include a track header (TKHD) box that describes characteristics of the track corresponding to TRAK box <NUM>. In some examples, TRAK box <NUM> may include coded video pictures, while in other examples, the coded video pictures of the track may be included in movie fragments <NUM>, which may be referenced by data of TRAK box <NUM> and/or sidx boxes <NUM>.

In some examples, video file <NUM> may include more than one track. Accordingly, MOOV box <NUM> may include a number of TRAK boxes equal to the number of tracks in video file <NUM>. TRAK box <NUM> may describe characteristics of a corresponding track of video file <NUM>. For example, TRAK box <NUM> may describe temporal and/or spatial information for the corresponding track. A TRAK box similar to TRAK box <NUM> of MOOV box <NUM> may describe characteristics of a parameter set track, when encapsulation unit <NUM> (<FIG>) includes a parameter set track in a video file, such as video file <NUM>. Encapsulation unit <NUM> may signal the presence of sequence level SEI messages in the parameter set track within the TRAK box describing the parameter set track.

MVEX boxes <NUM> may describe characteristics of corresponding movie fragments <NUM>, e.g., to signal that video file <NUM> includes movie fragments <NUM>, in addition to video data included within MOOV box <NUM>, if any. In the context of streaming video data, coded video pictures may be included in movie fragments <NUM> rather than in MOOV box <NUM>. Accordingly, all coded video samples may be included in movie fragments <NUM>, rather than in MOOV box <NUM>.

MOOV box <NUM> may include a number of MVEX boxes <NUM> equal to the number of movie fragments <NUM> in video file <NUM>. Each of MVEX boxes <NUM> may describe characteristics of a corresponding one of movie fragments <NUM>. For example, each MVEX box may include a movie extends header box (MEHD) box that describes a temporal duration for the corresponding one of movie fragments <NUM>.

As noted above, encapsulation unit <NUM> 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 specific time instance. In the context of AVC, the coded picture include one or more VCL NAL units which contains the information to construct all the pixels of the access unit and other associated non-VCL NAL units, such as SEI messages. Accordingly, encapsulation unit <NUM> may include a sequence data set, which may include sequence level SEI messages, in one of movie fragments <NUM>. Encapsulation unit <NUM> may further signal the presence of a sequence data set and/or sequence level SEI messages as being present in one of movie fragments <NUM> within the one of MVEX boxes <NUM> corresponding to the one of movie fragments <NUM>.

SIDX boxes <NUM> are optional elements of video file <NUM>. That is, video files conforming to the 3GPP file format, or other such file formats, do not necessarily include SIDX boxes <NUM>. In accordance with the example of the 3GPP file format, a SIDX box may be used to identify a sub-segment of a segment (e.g., a segment contained within video file <NUM>). The 3GPP file format defines a sub-segment as "a self-contained set of one or more consecutive movie fragment boxes with corresponding Media Data box(es) and a Media Data Box containing 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 a SIDX box "contains a sequence of references to subsegments of the (sub)segment documented by the box. The referenced subsegments are contiguous in presentation time. Similarly, the bytes referred to by a Segment Index box are always contiguous within the segment. The referenced size gives the count of the number of bytes in the material referenced.

SIDX boxes <NUM> generally provide information representative of one or more sub-segments of a segment included in video file <NUM>. For instance, such information may include playback times at which sub-segments begin and/or end, byte offsets for the sub-segments, whether the sub-segments include (e.g., start with) a stream access point (SAP), a type for the 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, or the like), a position of the SAP (in terms of playback time and/or byte offset) in the sub-segment, and the like.

Movie fragments <NUM> may include one or more coded video pictures. In some examples, movie fragments <NUM> may include one or more groups of pictures (GOPs), each of which may include a number of coded video pictures, e.g., frames or pictures. In addition, as described above, movie fragments <NUM> may include sequence data sets in some examples. Each of movie fragments <NUM> may include a movie fragment header box (MFHD, not shown in <FIG>). The MFHD box may describe characteristics of the corresponding movie fragment, such as a sequence number for the movie fragment. Movie fragments <NUM> may be included in order of sequence number in video file <NUM>. In some examples, one or more of movie fragments <NUM> may be preceded by a CMAF header, e.g., in accordance with Table <NUM> as discussed above. Moreover, a CMAF segment may include one or more CMAF fragments, each of which may include one or more optional boxes, a movie fragment box, and a media data box.

MFRA box <NUM> may describe random access points within movie fragments <NUM> of video file <NUM>. This may assist with performing trick modes, such as performing seeks to particular temporal locations (i.e., playback times) within a segment encapsulated by video file <NUM>. MFRA box <NUM> is generally optional and need not be included in video files, in some examples. Likewise, a client device, such as client device <NUM>, does not necessarily need to reference MFRA box <NUM> to correctly decode and display video data of video file <NUM>. MFRA box <NUM> may include a number of track fragment random access (TFRA) boxes (not shown) equal to the number of tracks of video file <NUM>, or in some examples, equal to the number of media tracks (e.g., non-hint tracks) of video file <NUM>.

In some examples, movie fragments <NUM> may include one or more stream access points (SAPs), such as IDR pictures. Likewise, MFRA box <NUM> may provide indications of locations within video file <NUM> of the SAPs. Accordingly, a temporal sub-sequence of video file <NUM> may be formed from SAPs of video file <NUM>. The temporal sub-sequence may also include other pictures, such as P-frames and/or B-frames that depend from SAPs. Frames and/or slices of the temporal sub-sequence may be arranged within the segments such that frames/slices of the temporal sub-sequence that depend on other frames/slices of the sub-sequence can be properly decoded. For example, in the hierarchical arrangement of data, data used for prediction for other data may also be included in the temporal sub-sequence.

<FIG> is a conceptual diagram illustrating an example CMAF fragment <NUM>. CMAF fragment <NUM> of <FIG> may correspond to one of movie fragments <NUM> of <FIG>. CMAF fragment <NUM> may conform to Table <NUM> above. CMAF fragments, such as CMAF fragment <NUM>, may be the smallest switching units that are handled by CMAF encoding, CMAF delivery, and CMAF players.

In the example of <FIG>, CMAF fragment <NUM> includes zero or more optional boxes <NUM>, a movie fragment (moof) box <NUM>, and a media data (mdat) box <NUM>. Optional boxes <NUM> are outlined with a dashed line to indicate that optional boxes <NUM> are optional. Optional boxes <NUM> of <FIG> may include none, any, or all of a segment type box, a producer reference time box, and/or DASH event message box(es).

MDAT box <NUM> includes random access media samples 208A-208C (random access media samples <NUM>), which may correspond to one or more coded video streams (CVSs). A decode time <NUM> of a first sample, e.g., an ordinal first sample, of MDAT box <NUM> (e.g., random access media sample 208A) may be indicated by a track fragment decode time (tfdt) box, which may be included in moof box <NUM>. In particular, the tfdt box may be includd in a track fragment (traf) box of moof box <NUM>, and may indicate a track fragment base media decode time.

In some examples, CMAF fragments, such as CMAF fragment <NUM>, conform to the following constraints:.

<FIG> is a conceptual diagram illustrating an example CMAF track <NUM>. In this example, CMAF track <NUM> includes CMAF header <NUM> and CMAF fragments 230A, 230B (CMAF fragments <NUM>). Each of CMAF fragments <NUM> includes a respective set of zero or more optional boxes, a moof box, and an mdat box. For example, CMAF fragment 230A includes optional boxes 224A, moof box 226A, and mdat box 228A, while CMAF fragment 230B includes optional boxes 224B, moof box 226B, and mdat box 228B. In this manner, each of CMAF fragments <NUM> may generally include elements similar to the elements of CMAF fragment <NUM> of <FIG>. CMAF track <NUM> of <FIG> may be included within a video file, such as video file <NUM> of <FIG>, where CMAF header <NUM> may correspond to ftyp box <NUM> and moov box <NUM> of <FIG>, and CMAF fragments <NUM> may begin at the beginning of movie fragments <NUM> of <FIG>. CMAF track <NUM> may generally conform to Table <NUM> above.

According to the techniques of this disclosure, CMAF header <NUM> may include an ftyp value at NL <NUM>, as discussed above, and as shown in the example of Table <NUM>. That is, content preparation device <NUM> of <FIG> may set the ftyp value, at least in part, to indicate the start of CMAF header <NUM>. Likewise, client device <NUM> of <FIG> (e.g., retrieval unit <NUM> of <FIG>) may determine the location of CMAF header <NUM> by parsing a bitstream including CMAF track <NUM> and detecting the ftyp value. In response, retrieval unit <NUM> may determine that CMAF fragments <NUM> follow CMAF header <NUM> (e.g., ftyp box <NUM> and moov box <NUM> of <FIG>), potentially also after one or more intervening sidx boxes, such as sidx boxes <NUM> (<FIG>).

Moreover, each of CMAF fragments <NUM> may include styp values representative of whether the CMAF fragments <NUM> correspond to CMAF fragments only, CMAF segments, or CMAF chunks, e.g., in corresponding moof boxes 226A, 226B (moof boxes <NUM>). Thus, retrieval unit <NUM> may determine whether one of CMAF fragments <NUM> is a CMAF fragment only, a CMAF chunk, or a CMAF segment, according to the values for the styp of the respective CMAF fragments in the respective moof boxes <NUM>.

For example, content preparation device <NUM> (<FIG>) may assign a value of "cmfl" to the styp element of one of moof boxes <NUM> of a corresponding one of CMAF fragments <NUM> to indicate that the one of CMAF fragments <NUM> includes a CMAF chunk, a value of "cmff" to indicate that the one of CMAF fragments <NUM> is a CMAF fragment only, or a value of "cmfs" to indicate that the one of CMAF fragments <NUM> is included in a CMAF segment. Likewise, retrieval unit <NUM> may determine that one of CMAF fragments <NUM> includes a CMAF chunk when an styp element of the one of moof boxes <NUM> has a value of "cmfl," that the CMAF fragment is only a CMAF fragment when the styp element of the one of moof boxes <NUM> has a value of "cmff," or that the CMAF fragment is included in a CMAF segment when the styp element of the one of moof boxes <NUM> has a value of "cmfs.

<FIG> is a conceptual diagram illustrating an example CMAF segment <NUM>. CMAF segment <NUM> of <FIG> may be included within a CMAF track file, following a CMAF header, e.g., as shown in <FIG>. CMAF segment <NUM> may conform to Table <NUM> above.

In the example of <FIG>, CMAF segment <NUM> includes two example CMAF fragments 250A, 250B (CMAF fragments <NUM>). Each of CMAF fragments <NUM> includes a respective set of zero or more optional boxes, a moof box, and an mdat box. For example, CMAF fragment 250A includes optional boxes 244A, moof box 246A, and mdat box 248A, while CMAF fragment 250B includes optional boxes 244B, moof box 246B, and mdat box 248B. In this manner, each of CMAF fragments <NUM> may generally include elements similar to the elements of CMAF fragment <NUM> of <FIG>. CMAF segment <NUM> of <FIG> may be included within a video file, such as video file <NUM> of <FIG>, where CMAF fragments <NUM> may begin at the beginning of movie fragments <NUM> of <FIG>.

In accordance with the techniques of this disclosure, content preparation device <NUM> (<FIG>) may assign a value of "cmfs" to an styp value of moof box 246A of CMAF fragment 250A to indicate that CMAF fragment 250A is included within and represents the start of CMAF segment <NUM>. Likewise, retrieval unit <NUM> of <FIG> may determine that CMAF fragment 250A represents the start of CMAF segment <NUM> in response to determining that an styp value of moof box 246A of CMAF fragment 250A has a value of "cmfs.

<FIG> are conceptual diagrams illustrating example CMAF fragments and CMAF chunks. In particular, <FIG> illustrates an example of a CMAF fragment <NUM> only. That is, CMAF fragment <NUM> includes moof box <NUM>, mdat box <NUM>, and coded video sequence samples 266A-<NUM> (coded video sequence samples <NUM>). <FIG> illustrates an example of a CMAF fragment <NUM> including CMAF chunks 272A-272D (CMAF chunks <NUM>). Each of CMAF chunks <NUM> may conform to Table <NUM> above. That is, in this example, each of CMAF chunks <NUM> includes a respective moof box 274A-274D (moof boxes <NUM>), mdat boxes 276A-276D (mdat boxes <NUM>), and respective coded video sequence samples 278A-<NUM> (coded video sequence samples <NUM>).

CMAF chunks <NUM>, as shown, may be included within CMAF fragment <NUM>, which may be included within CMAF tracks and/or CMAF segments, as discussed above. In one example, CMAF chunks are the smallest atomic units that are handled by CMAF encoding, CMAF delivery, and CMAF Players. By dividing CMAF fragment <NUM> into CMAF chunks <NUM>, e.g., as shown in <FIG>, media data of coded video sequence samples <NUM> can be output more frequently than media data of coded video sequence samples <NUM> of <FIG>. That is, content preparation device <NUM> of <FIG>, for example, may output each of CMAF chunks <NUM> at respective encoder output times 280A-280D (encoder output times <NUM>). By contrast, content preparation device <NUM> may output the entire CMAF fragment <NUM> at encoder output time <NUM>. In this manner, using CMAF chunks, such as CMAF chunks <NUM>, may reduce latency of transporting media data for a streaming service.

CMAF chunks <NUM> may be labeled as having styp values of "cmfl" in respective moof boxes <NUM>, per the techniques of this disclosure. That is, content preparation device <NUM> may specify the value of "cmfl" in the respective moof boxes <NUM>. Likewise, retrieval unit <NUM> may determine that CMAF fragment <NUM> includes CMAF chunks <NUM> based on the value of "cmfl" in the respective moof boxes <NUM>. Retrieval unit <NUM> may also determine the start of each of CMAF chunks <NUM> by parsing CMAF fragment <NUM> and detecting the value of "cmfl" for styp values of the respective moof boxes <NUM>.

In some examples, CMAF chunks may conform to the following constraints:.

<FIG> is a conceptual diagram illustrating an example system <NUM> in accordance with the techniques of this disclosure. In this example, system <NUM> is divided into four logical portions: a manifest portion, a content offering portion, a delivery portion, and a platforms and players portion. The manifest portion and the content offering portion may generally correspond to content preparation device <NUM> of <FIG>, the delivery portion may correspond to server device <NUM> of <FIG>, and the platforms and players portion may correspond to client device <NUM> of <FIG>.

In the example of <FIG>, the manifest portion of system <NUM> includes DASH MPD <NUM>, HTTP live streaming (HLS) M3U8 playlist <NUM>, and an application <NUM>. DASH MPD <NUM> references CMAF content <NUM>, which is included in the content offering portion of system <NUM>. CMAF content <NUM> is provided to a content delivery network (CDN) <NUM>, which provides broadcast and/or multicast services as part of the delivery portion of system <NUM>. Various platforms and players of the platforms and players portion of system <NUM> may receive media data from CDN <NUM>, such as a stand-alone HTTP live streaming (HLS) player <NUM>, a device <NUM> for receiving HLS as an HTML-<NUM> video tag, a stand-alone DASH player <NUM>, a device <NUM> for receiving DASH as an HTML-<NUM> video tag, and/or an HTML-<NUM> MSE-based Type-<NUM> player <NUM>. The techniques of this disclosure may generally support one type of signaling for devices configured according to any or all of these example use cases.

<FIG> is a conceptual diagram illustrating an example decomposition <NUM> within a WAVE application <NUM> using HTML-<NUM> application programming interfaces (APIs) <NUM> between platform <NUM>, content <NUM>, and application <NUM>, each of which may use data according to the techniques of this disclosure. WAVE device platform <NUM> may have a set of capabilities that are accessible for application <NUM> through HTML-<NUM> APIs <NUM> and detailed codec capabilities. WAVE content <NUM> may be played on WAVE device platform <NUM> within WAVE application <NUM>. WAVE application <NUM> may use the capabilities of WAVE platform device <NUM> for media services.

<FIG> is a conceptual diagram illustrating an example box sequence and containment of a CMAF chunk <NUM>. In this example, lower boxes indicate containment in the box above. That is, CMAF chunk includes segment type ('styp') box <NUM>, producer reference time ('prft') event ('emsg') <NUM>, movie fragment ('moof') box <NUM>, and media data ('mdat') box. Moof box <NUM>, in turn, includes movie fragment header ('mfhd') box <NUM>, protection specific header ('pssh') box <NUM>, and track fragment ('traf') box <NUM>. The sequence of boxes contained in the traf box <NUM> as shown in <FIG> is one example. In this example, traf box <NUM> includes track fragment header ('tfhd') box <NUM>, track fragment run ('trun') box <NUM>, sample encryption ('senc') box <NUM>, sample auxiliary information sizes ('saiz') box <NUM>, sample auxiliary information offsets ('saio') box <NUM>, sample to group ('sbgp') box <NUM>, and sample group descriptions ('sgpd') box <NUM>. Boxes shown with dashed outlines, such as styp box <NUM>, prtf emsg <NUM>, and pssh box <NUM>, may be optional. Certain boxes of traf box <NUM> as shown in the bottom row are conditionally required when encryption is used, in some examples.

Any CMAF Chunk or CMAF Fragment that contains the initial samples of a CMAF Fragment are to conform to the CMAF Segment brand 'cmff' and the brand should be signaled in the 'styp.

CMAF Headers, CMAF Fragments, and CMAF Chunks may be packaged and referenced as CMAF Addressable Media Objects for storage and delivery, as described in Section <NUM> of the CMAF Media Object Model. Each CMAF Addressable Media Object may be referenced as a Resource by an external specification, e.g. MPEG DASH.

The CMAF Header, CMAF Chunks and CMAF Fragments may be made available as CMAF Addressable Resources by simple transformation means, for example:.

In CMAF fragment mode, a CMAF header may be available as an addressable object. In this mode, the CMAF Fragment may be directly made available as a CMAF Addressable Media Object.

In CMAF segment mode, CMAF segments may be used as discussed above, e.g., with respect to Table <NUM> and <FIG>. A CMAF segment may be defined as a CMAF Addressable Media Object that contains one or more complete CMAF Fragments in presentation order. In some examples:.

In CMAF chunk mode, the CMAF Header may be available an addressable object. Each CMAF Fragment, in this mode, may be included in one or more CMAF Chunks. The CMAF Chunk may be directly made available as a CMAF Addressable Media Object. The initial CMAF may include two CMAF Segment brands, 'cmff' and cmfl', to signal the compatibility to the initial part of the CMAF Fragment as well as to the CMAF chunk. Non-initial CMAF Chunks may include the CMAF Segment brand 'cmfl' to signal the compatibility to this segment format.

A CMAF track file may be a CMAF Addressable Media Object defined to be a CMAF Track stored as a single track in an ISO BMFF file, with the first CMAF Fragment baseMediaDecodeTime equal to zero. The CMAF Header and all CMAF Fragments may be included in a single CMAF Track File. In some examples, a CMAF track file conforms to the following constraints:.

<FIG> is a flowchart illustrating an example method of generating a bitstream in accordance with the techniques of this disclosure. The method of <FIG> is explained with respect to content preparation device <NUM> (<FIG>). However, it should be understood that other devices may be configured to perform this or a similar method. For example, server device <NUM> may perform some or all steps of the method of <FIG>.

Initially, audio encoder <NUM> and video encoder <NUM> (<FIG>) encode media data, such as audio or video data respectively, to form encoded samples of media data. Encapsulation unit <NUM> (<FIG>) then receives the encoded samples of media data and generates a bitstream including the encoded samples formatted according to CMAF in accordance with the techniques of this disclosure. In particular, encapsulation unit <NUM> generates a CMAF header of a CMAF track file (<NUM>). Encapsulation unit <NUM> may generate the CMAF header according to Table <NUM> above. For example, encapsulation unit <NUM> may set a file type (ftyp) value of the CMAF header at the start of the CMAF header (<NUM>). Encapsulation unit <NUM> may also generate a movie (moov) box of the CMAF header, e.g., including the elements of moov box <NUM> of <FIG>.

Encapsulation unit <NUM> may then encapsulate the encoded media samples in respective CMAF fragments (<NUM>). In various examples, the CMAF fragments may correspond to CMAF fragments only, CMAF fragments included in CMAF segments, or CMAF fragments including CMAF chunks. Accordingly, encapsulation unit <NUM> may set segment type (styp) values at the start of the CMAF fragments, to indicate starts of the CMAF fragments and types for the CMAF fragments (e.g., CMAF fragments only, CMAF segments, or CMAF chunks). As noted above, the value "cmfs" may represent a CMAF segment, the value "cmff" may represent a CMAF fragment only, and the value "cmfl" may represent a CMAF chunk. Encapsulation unit <NUM> may set the styp values in respective moof boxes of the CMAF fragments.

Encapsulation unit <NUM> may then generate a bitstream (<NUM>) including the CMAF header and CMAF fragments, and send the bitstream to a client device (<NUM>), such as client device <NUM> (<FIG>). In some examples, content preparation device <NUM> may send the bitstream to server device <NUM>, which may then send the bitstream to client device <NUM>.

In this manner, the method of <FIG> represents an example of a method of generating a bitstream, the method including generating, by a processor implemented in circuitry, a Common Media Application Format (CMAF) header of a CMAF track file; setting, by the processor, a value for a file type (FTYP) value of the CMAF header indicating the start of the CMAF header; encapsulating, by the processor, one or more samples of media data in one or more CMAF fragments following the CMAF header of the CMAF track file; and generating, by the processor, a bitstream including the CMAF header and the CMAF track file, the one or more CMAF fragments following the CMAF header in the CMAF track file.

<FIG> is a flowchart illustrating an example of a method of processing media data in accordance with the techniques of this disclosure. The method of <FIG> is explained with respect to client device <NUM> of <FIG>. However, it should be understood that other devices may be configured to perform this or a similar method in accordance with the techniques of this disclosure.

Initially, retrieval unit <NUM> (<FIG>) of client device <NUM> parses a bitstream including a CMAF track file (<NUM>). It should be understood that retrieval unit <NUM> may initially request the bitstream from, e.g., server device <NUM> or content preparation device <NUM> (<FIG>). While parsing the bitstream, retrieval unit <NUM> may detect a file type (ftyp) value of the CMAF track file (<NUM>). As shown in Table <NUM> above, the ftyp value may be at the start of a CMAF header of the CMAF track file. Accordingly, retrieval unit <NUM> may determine that the CMAF header starts with the ftyp value (<NUM>). Retrieval unit <NUM> may further determine that the rest of the CMAF header (e.g., a moov box) follows the ftyp value.

Retrieval unit <NUM> may, therefore, determine that one or more CMAF fragments of the CMAF track file follow the CMAF header (and any sidx boxes, if present, e.g., as shown in Table <NUM> above and in <FIG>). In particular, retrieval unit <NUM> may continue parsing the bitstream following the CMAF header and detect one or more segment type (styp) values following the CMAF header (<NUM>). Retrieval unit <NUM> may detect the styp values in respective moof boxes of the CMAF fragments. In accordance with the techniques of this disclosure, retrieval unit <NUM> may determine that each of the styp values represents the start of a corresponding CMAF fragment. Moreover, retrieval unit <NUM> may determine types for the CMAF fragments from the respective styp values. As discussed above, in some examples, the value "cmfs" for styp may represent a CMAF segment, the value "cmff" for styp may represent a CMAF fragment only, and the value "cmfl" for styp may represent a CMAF chunk.

Therefore, retrieval unit <NUM> may process the corresponding CMAF fragments starting at the respective styp values according to the styp values (<NUM>). For example, retrieval unit <NUM> may determine whether a CMAF fragment only follows the styp value, whether one or more CMAF fragments are to be expected as part of a CMAF segment (e.g., as shown in <FIG>), or whether the CMAF fragment includes one or more CMAF chunks (e.g., as shown in <FIG>).

In this manner, the method of <FIG> represents an example of a method of processing media data, the method including parsing, by a processor implemented in circuitry, a bitstream including data formatted according to Common Media Application Format (CMAF), detecting, by the processor and during the parsing, a file type (FTYP) value for a CMAF track file of the bitstream, determining, by the processor, that a CMAF header of the CMAF track file starts with the FTYP value, and processing, by the processor, one or more CMAF fragments following the CMAF header of the CMAF track file.

Data storage media may be any available media 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.

Disk and disc, as used herein, includes compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk and Blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers.

Claim 1:
A method of processing media data, the method comprising:
parsing, by a processor implemented in circuitry, a bitstream including data formatted according to Common Media Application Format, CMAF, the bitstream including a CMAF track file comprising a CMAF header (<NUM>) including a file type, FTYP, box at the start of the CMAF header (<NUM>), and one or more CMAF fragments (230A, 230B) located in the bitstream after the CMAF header (<NUM>);
detecting, by the processor and during the parsing, the FTYP value for the CMAF track file of the bitstream;
determining, by the processor, the location of the CMAF header (<NUM>) of the CMAF track file using the FTYP value;
determining, by the processor, that one or more CMAF fragments (230A, 230B) follow the CMAF header (<NUM>); and
processing, by the processor, one or more CMAF fragments (230A, 230B) of the CMAF track file,
wherein processing the one or more CMAF fragments (230A, 230B) comprises:
detecting one or more segment type, STYP, values in the bitstream, wherein the STYP value has a value "cmff" representative of the CMAF fragments (230A, 230B) containing the initial samples of the CMAF fragment;
determining that each of the one or more STYP values corresponds to a start of a respective one of the CMAF fragments (230A, 230B); and
processing each of the CMAF fragments (230A, 230B) starting from the corresponding STYP value.