Patent Description:
This disclosure relates to storage and transport of encoded media data.

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 as High Efficiency Video Coding (HEVC)), and extensions of such standards, to transmit and receive digital video information more efficiently.

Video compression techniques perform spatial prediction 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 can be further partitioned. Macroblocks in an intra-coded (I) frame or slice are encoded 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.

After video data has been encoded, the video data may be packetized for transmission or storage. The video 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.

<CIT> discloses an information processing device and an information processing method. An http client: requests a delivery server to transmit an MPD file for managing moving-image content that has a plurality of attributes, and an initialization segment file for moving-image content having a prescribed attribute among the plurality of attributes; and transmits an MPD request including a push-init-segment command.

In general, this disclosure describes techniques for signaling parameters of a media presentation. The parameters may be included in an initialization set, which may identify an initialization segment. The initialization set may define parameters that will not be exceeded for the entire duration of the media presentation. In this manner, a client device may retrieve the data of the initialization set once, and initialize various processes or environments (such as decryption, decoding, and rendering) using the data of the initialization set, without repeatedly retrieving the initialization set and/or reinitializing these processes or environments during playback of media data for the media presentation. In this manner, these techniques may improve the field of media streaming, in that these techniques may reduce processing cycles associated with initialization and thereby reduce latency associated with presenting media data of the media presentation.

In general, this disclosure describes techniques for transmitting initialization parameters using, e.g., an initialization set. The initialization set may specify a suitable initialization for one or more media types for a media presentation. Periods of the media presentation should therefore include at least one adaptation set that can be played when initialized using the initialization set.

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 according to the techniques of this disclosure. 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 an 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 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 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>.

Content preparation device <NUM> may determine various maximum or unchanging parameters of a media presentation (e.g., multimedia content <NUM>) among representations <NUM> and/or adaptation sets of the media presentation. For example, content preparation device <NUM> may determine a maximum width and a maximum height of pictures for the media presentation across representations <NUM> and/or adaptation sets. As another example, content preparation device <NUM> may determine a maximum frame rate for video across representations <NUM> and/or adaptation sets. Content preparation device <NUM> may construct initialization segments for each type of media data (e.g., video, audio, timed text, or the like), such that data of the initializations segments can be used to initialize all of representations <NUM> of the media presentation according to the determined maximum values (width, height, frame rate, etc.).

In this manner, client device <NUM> may initialize playback of the media presentation using an initialization segment once, and then be able to perform playback of media data of any representation from any adaptation set thereafter, without reinitializing.

Content preparation device <NUM> may further signal data identifying the initialization segments in manifest file <NUM>. For example, content preparation device <NUM> may construct manifest file <NUM> to include an initialization set that signals the various initialization parameters (e.g., maximum width, maximum height, maximum frame rate, etc.) as well as uniform resource locators (URLs) of the initialization segments.

Thus, client device <NUM> may retrieve manifest file <NUM>, determine locations of the initialization segments, retrieve the initialization segments, and then initialize playback of media data of the media presentation (e.g., multimedia content <NUM>). Client device <NUM> may then retrieve media data of any of representations <NUM> and perform playback of the media data without reinitialization. For example, representation 68A may have pictures having the specified maximum width and maximum height, and/or may have the maximum frame rate. Representation 68N may have pictures that are less than the specified maximum width and maximum height, and/or may have less than the maximum frame rate. Client device <NUM> may retrieve (and server device <NUM> and/or content preparation device <NUM> may send) media data of representation 68A for a first playback time and media data of representation 68N for a second, different playback time. Nevertheless, client device <NUM> may perform playback of both sets of media data (i.e., from both representation 68A and representation 68N) without performing reinitialization.

In this manner, client device <NUM> represents an example of a device for retrieving media data including a memory configured to store media data of a media presentation; and one or more processors implemented in circuitry and configured to: retrieve a manifest file for the media presentation, the manifest file including data for an initialization set, the initialization set including initialization parameters for the full duration of the media presentation; initialize playback of the media data of the media presentation using the initialization set; retrieve the media data of the media presentation; and present the media data according to the initialized playback.

Likewise, content preparation device <NUM> and server device <NUM> represent examples of a device for sending media data including a memory for storing media data of a media presentation; and one or more processors implemented in circuitry and configured to: send a manifest file for the media presentation to a client device, the manifest file including data for an initialization set, the initialization set including initialization parameters for the full duration of the media presentation; receive a request for media data of the media presentation from the client device; and send the requested media data to the client device.

<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 this example, eMBMS middleware unit <NUM> further includes eMBMS reception unit <NUM>, cache <NUM>, and proxy 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 broadcast/multicast service center (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.

Proxy server unit <NUM> may act as a server for DASH client <NUM>. For example, proxy server unit <NUM> may provide a MPD file or other manifest file to DASH client <NUM>. Proxy 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 proxy 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 proxy server unit <NUM>. Proxy 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>.

In accordance with the techniques of this disclosure, MPD <NUM> may include an initialization set, as discussed in greater detail below. The initialization set may specify initialization parameters that can be used to initialize playback of any of representations <NUM>, that is, media data of any of segments <NUM>, <NUM>. For example, the initialization set may specify a maximum width and maximum height of pictures of representations <NUM> (that is, segments <NUM>, <NUM>). As another example, additionally or alternatively, the initialization set may specify a maximum frame rate for representations <NUM>. Thus, each of representations <NUM> may have frame rates equal to or lower than the maximum frame rate. Likewise, each of representations <NUM> may include pictures having less than or equal to the maximum width and/or maximum height.

<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>.

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 contain 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>.

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 example DASH client <NUM> in accordance with the techniques of this disclosure. DASH client <NUM> of <FIG> may correspond to or be included within retrieval unit <NUM> of <FIG> or DASH client <NUM> of <FIG>. In this example, DASH client <NUM> includes selection logic <NUM>, DASH access engine <NUM>, and media engines 206A, 206B.

Among other organizations, DASH Industry Forum (DASH-IF) and Consumer Technology Association (CTA) Web Application Video Ecosystem (CTA WAVE) have discussed the topic of consistent playback of media based on a model as shown in <FIG>, for which DASH access engine <NUM> establishes a media track buffer for each media type and segments are consumed in this environment. For example, the media types may include audio and video data, and thus, media engine 206A may process audio data, while media engine 206B may process video data.

An important topic is the ability to playback the presentation across program boundaries and for advertisement (ad) insertion without disrupting the playback experience. Two key issues have been observed. One issue corresponds to capability discovery if the media can be played back over the entire presentation, including across program boundaries. Another issue corresponds to the initialization and establishment of a track buffer/media pipeline for each media type that can be used for continuous playback of the media of one type for the entire presentation.

<NUM> and TuC of DASH discuss several options to address the first issue regarding capability discovery noted above. In particular, the options include use of early available periods and/or use of a dedicated capability signaling that combines different features.

<FIG> is a conceptual diagram illustrating an example of track buffer-based playback.

While a solution following the options discussed above may be sufficient to address the capability discovery aspect for playback of the entire presentation, it is still unclear if a DASH client can establish the playback of the media in a sufficiently good manner.

Typically, a device needs to establish at least a track buffer/media pipeline for a video media type and another track buffer/media pipeline for an audio media type. Track buffers/media pipelines for other media types, such as subtitles (timed text), may need to be established as well. A device may support the establishment of multiple source buffers for each media type.

A typical operation to establish such a source buffer is as follows:.

As an example, the HTML-<NUM> Media Element and the Media Source extension allows to add a source buffer using the MediaSource. addSourceBuffer(type) method. For details, see www. org/TR/media-source/#dom-mediasource-addsourcebuffer. For the case of the ISO BMFF byte stream format, the source buffer is further initialized by appending an Initialization Segment (IS) to the SourceBuffer by using the MediaSource. appendBuffer(IS). It is relevant that the initialization is done such that the playback of the remainder of the presentation can be done appropriately. Note that the source buffer may be updated/re-initialized by appending an IS to the SourceBuffer by using the MediaSource. appendBuffer(CH).

The techniques of this disclosure may be used to address the ability to specify initialization of media pipelines based on a global master initialization segment for each media type.

<FIG> is a conceptual diagram illustrating an example content model for DASH multitrack media data according to the techniques of this disclosure. In this example, content <NUM> includes media type video content <NUM>, media type audio content <NUM>, media type subtitle content <NUM>, and media type application content <NUM>. These media types may be arranged into a variety of content types, such as media type content main <NUM>, media type content alternative 232A, and media type content alternative 232B. Each of the main and alternative contents may include content selected from one or more corresponding target version adaptation sets 234A-234C, including respective encoded representations such as representations 236A-236C.

In order to support the content author in providing content in a consistent manner, <FIG> provides a conceptual content model for DASH content <NUM> in one Period of an MPD according to DASH-IF IOPs v4. In an extension to the model of <FIG>, for an entire MPD, an Initialization Set may be selected that provides a superset of multiple Adaptation Sets (adaptation sets <NUM>) within a Period as well as across Periods. This Initialization Set, if selected, enables continuous playback across Period boundaries.

A source device (such as content preparation device <NUM> and/or server device <NUM> of <FIG>) and a client device (such as client device <NUM> of <FIG> and/or DASH client <NUM> of <FIG>) may be configured to use the techniques of this disclosure to use an initialization set that allows for continuous playback across period boundaries. In particular, these techniques include the following:.

The Initialization Set may be defined in two example ways:.

The semantics of the MPD element of the DASH specification may be updated to include an InitializationSet element, as shown in Table <NUM> below:.

Semantics for the Initialization Set element of the MPD (or other manifest file) may be defined as follows (where identified sections correspond to sections of the DASH standard):.

An Initialization Set provides a common set of media properties across the Media Presentation. If an Initialization Set is provided in an MPD with certain properties, there shall be at least one Adaptation Set in each Period with the same properties in each Period. An Initialization Set may be selected at the start of a Media Presentation in order to establish the relevant decryption, decoding and rendering environment. Hence, Initialization Sets share all parameters of Adaptation Sets, but only in a Media Presentation an Adaptation Set may have additional information, for example:.

If an MPD has multiple Periods, there should be at least one Initialization Set be present for each media type. The semantics of the attributes and elements within an InitializationSet element are provided in Table <NUM> of <NUM>. The XML syntax of the InitializationSet element is provided in <NUM>.

The following attribute may be added to the Adaptation Set element of the MPD:.

By providing the Initialization Set, the DASH client can select an Initialization that matches capabilities of a device including the DASH client and also can ensure continuous playback by initializing with the provided Initialization Segment. The techniques of this disclosure may also address the discussion on Early Available Period and provide a new capability mechanism as the relevant information is provided upfront.

<FIG> is a flowchart illustrating an example method of sending media data according to the techniques of this disclosure. For purposes of example, the method of <FIG> is explained with respect to content preparation device <NUM> of <FIG>. However, it should be understood that other devices, such as server device <NUM> of <FIG>, may be configured to perform this or a similar method, alone or in conjunction with other devices.

Initially, content preparation device <NUM> determines initialization parameters (<NUM>) for a media presentation, such as multimedia content <NUM>. The initialization parameters may be used to initialize media data of any adaptation set and/or representation of the media presentation. For example, the initialization parameters may specify a maximum width and maximum height of pictures and/or a maximum framerate for the media presentation. The initialization parameters may also specify a picture aspect ratio for pictures of the media presentation.

Content preparation device <NUM> may then construct initialization segments (<NUM>) for the media presentation. Content preparation device <NUM> may construct the initialization segments for a variety of types of media, such as audio, video, timed text (closed captions), or the like. Content preparation device <NUM> may construct the initialization segments according to the initialization parameters determined above.

Content preparation device <NUM> may further construct a manifest file (such as a DASH MPD) including one or more initialization sets (<NUM>). Each of the initialization sets may conform to the initialization sets of Tables <NUM> and <NUM> above. As shown above, each initialization set may include an @maxWidth element specifying a maximum picture width, a @maxHeight element specifying a maximum picture height, and a @maxFrameRate element specifying a maximum frame rate. Content preparation device <NUM> may further specify URLs of the initialization segments in the initialization sets, e.g., in respective @initialization elements. Content preparation device <NUM> may construct one initialization set per adaptation set, and thereby construct one or more initialization sets per media type (e.g., audio, video, timed text, or the like). The initialization set may include an @contentType element specifying a media type for the initialization set (e.g., audio, video, timed text, or the like), as shown in Table <NUM>.

Content preparation device <NUM> may then send the initialization sets to a client device (<NUM>). In particular, content preparation device <NUM> may send the manifest file to the client device, the manifest file including the initialization sets. As shown in <FIG>, content preparation device <NUM> may send the manifest file to server device <NUM>, which may send the manifest file to client device <NUM> in response to a request from client device <NUM> for the manifest file of a particular media presentation.

Content preparation device <NUM> may also receive requests for media data from the client device (<NUM>). Alternatively, server device <NUM> may receive the requests. In response to the requests, content preparation device <NUM> (or server device <NUM>) may send the requested media data to the client device (<NUM>). In some examples, the client device (e.g., client device <NUM>) may request media data from various representations for the same type of media content. However, client device <NUM> may only request the initializations segment for that type of media content once, since the initialization segment can be used to initialize playback of all media content of that type of the media presentation. In this manner, the techniques of this disclosure may be used to reduce a number of initialization segments sent to client device <NUM> by content preparation device <NUM> and/or server device <NUM>. In this manner, these devices may avoid processing of requests for the initialization segments, and also reduce network bandwidth utilized in receiving requests for the initialization segments and sending the initialization segments to client device <NUM>.

In this manner, the method of <FIG> represents an example of a method of sending media data including sending a manifest file for a media presentation to a client device, the manifest file including data for an initialization set, the initialization set including initialization parameters for the full duration of the media presentation; receiving a request for media data of the media presentation from the client device; and sending the requested media data to the client device.

<FIG> is a flowchart illustrating an example method of retrieving media data according to the techniques of this disclosure. For purposes of example and explanation, the method of <FIG> is explained with respect to client device <NUM> of <FIG>. However, other devices may be configured to perform this or a similar method. For example, DASH client <NUM> of <FIG> may be configured to perform this method.

Initially, client device <NUM> may retrieve a manifest file including one or more initialization sets (<NUM>). An initialization set of the manifest file may specify initialization parameters such as, for example, a maximum width and maximum height of pictures, a picture aspect ration of the pictures, a maximum frame rate, or the like. The initialization set may also indicate a URL of a corresponding initialization segment. Thus, client device <NUM> may retrieve the initializations segments (<NUM>) for each of the initialization sets (and likewise, for each of the types of media content, e.g., audio, video, timed text, and the like).

Client device <NUM> may then use the initialization sets and initialization segments to initialize playback of the media data (<NUM>). Such initialization may be for decryption, decoding, and or rendering. For example, client device <NUM> may initialize a video decoder and a renderer according to the maximum height, maximum width, and maximum frame rate. Such initialization may include, for example, allocating buffer space in a buffer of a memory (e.g., cache <NUM>) for storing retrieved media data and/or for storing intermediate media data, e.g., partially or fully decoded media data.

Client device <NUM> may then request media data (<NUM>), e.g., by issuing HTTP GET or partial GET requests for the media data. Client device <NUM> may then receive the media data (<NUM>) and playback the media data (<NUM>). In some examples, client device <NUM> may retrieve media data having the maximum specified parameters, e.g., maximum height, maximum width, maximum frame rate, etc. In some examples, client device <NUM> may retrieve media data having less than the maximum specified parameters. Client device <NUM> may retrieve media data having the maximum specified parameters for a first playback time and media data having less than the maximum specified parameters for a second, different playback time. However, client device <NUM> need not reinitialize playback of the media data having less than the maximum specified parameters, because the original initialization can be used for playback of any of the media data of the media presentation, since the initialization parameters either specify maximum or unchanging parameters.

In this manner, the method of <FIG> represents an example of a method of retrieving media data including retrieving a manifest file for a media presentation, the manifest file including data for an initialization set, the initialization set including initialization parameters for the full duration of the media presentation; initializing playback of media data of the media presentation using the initialization set; retrieving the media data of the media presentation; and presenting the media data according to the initialized playback.

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 retrieving media data, the method comprising:
retrieving a manifest file (<NUM>) for a media presentation (<NUM>), the manifest file (<NUM>) including a manifest file element having an initialization set element, the initialization set element including initialization parameters for a full duration of the media presentation (<NUM>);
initializing playback of media data of the media presentation (<NUM>) using the initialization set element;
retrieving the media data of the media presentation (<NUM>); and
presenting the media data according to the initialized playback,
wherein:
the media presentation (<NUM>) includes a plurality of periods, each of the periods including an adaptation set having a representation (<NUM>) including media data that can be presented using the initialization parameters of the initialization set element and the initialized playback, the method further comprising determining the representations (<NUM>) of the periods including the media data that can be presented using the initialization parameters and the initialized playback using data of the manifest file (<NUM>);
the initialization parameters specify common attribute elements across the media presentation including one or more of a maximum width of pictures of the media presentation (<NUM>) in all representations in all adaptation sets associated with the initialization set element or a maximum height of the pictures of the media presentation (<NUM>) in all representations in all adaptation sets associated with the initialization set element.