Random access at the resynchronization point of DASH segments

Abstract

A device for retrieving media includes a memory configured to store media data of a media presentation; and one or more processors implemented in a circuit configured to: retrieve a manifest file of the media presentation that indicates that container parsing of the bitstream media data may begin at a resynchronization point of a segment of a representation of the media presentation; use the manifest file to form a request to retrieve media data of the representation starting at the resynchronization point, the resynchronization point being at a position other than the start of a segment and representing a point at which container parsing of the bitstream media data may begin; send the request to initiate retrieval of the media data of the media presentation starting at the resynchronization point; and present the retrieved media data.

Description

[Technical field]

[0001]

[0001] This application claims the benefit of U.S. Application No. 17 / 061,152, filed October 1, 2020, and U.S. Provisional Application No. 62 / 909,642, filed October 2, 2019, the entire contents of which are incorporated by reference into this specification.

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

[0003]

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

[0004]

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

[0005] After the video data is encoded, it may be packetized for transmission or storage and assembled into a video file that conforms to any of a variety of standards, such as an International Organization for Standardization (ISO) based media file format, such as AVC, and its extensions. Summary of the Invention

[0006]

[0006] Generally, this disclosure describes techniques for accessing data in a segment not only at the beginning of the segment but also elsewhere within the segment (e.g., for random access) in Dynamic Adaptive Streaming over HTTP (DASH) and / or Common Media Access Format (CMAF). This disclosure also describes techniques related to signaling the ability to perform random access within a segment. This disclosure describes various use cases for these techniques. For example, this disclosure defines resync points and signaling of resync points in DASH and ISO Base Media File Format (BMFF).

[0007]

[0007] In one example, a method for retrieving media data includes retrieving a manifest file of a media presentation indicating that container parsing of a bitstream media data may begin at a resynchronization point of a segment of a representation of the media presentation, forming a request to retrieve media data of the representation starting at the resynchronization point using the manifest file, the resynchronization point being at a position other than the start of the segment and representing a point at which container parsing of the bitstream media data may begin, sending a request to initiate retrieval of the media data of the media presentation starting at the resynchronization point, and presenting the retrieved media data.

[0008]

[0008] In another example, a device for retrieving media data includes a memory configured to store media data of a media presentation; and one or more processors implemented in a circuit configured to: retrieve a manifest file of the media presentation indicating that container parsing of the bitstream media data may begin at a resynchronization point of a segment of a representation of the media presentation; use the manifest file to form a request to retrieve media data of the representation starting at a resynchronization point, the resynchronization point being at a position other than the start of a segment and representing a point at which container parsing of the bitstream media data may begin; send a request to initiate retrieval of the media data of the media presentation starting at the resynchronization point; and present the retrieved media data.

[0009]

[0009] In another example, a computer-readable storage medium has stored thereon instructions that, when executed, cause a processor to retrieve a manifest file of a media presentation indicating that container parsing of the bitstream media data may begin at a resynchronization point of a segment of a representation of the media presentation, use the manifest file to form a request to retrieve media data of the representation starting at a resynchronization point, the resynchronization point being at a position other than the start of a segment and representing a point at which container parsing of the bitstream media data may begin, send a request to initiate retrieval of the media data of the media presentation starting at the resynchronization point, and present the retrieved media data.

[0010]

[0010] In another example, a device for retrieving media data includes means for retrieving a manifest file of a media presentation indicating that container parsing of the bitstream media data may begin at a resynchronization point of a segment of a representation of the media presentation, means for forming a request to retrieve media data of the representation starting at the resynchronization point using the manifest file, the resynchronization point being at a position other than the start of a segment and representing a point at which container parsing of the bitstream media data may begin, means for sending a request to initiate retrieval of the media data of the media presentation starting at the resynchronization point, and means for presenting the retrieved media data.

[0011]

[0011] The details of one or more examples are set forth in the accompanying drawings and the description below. Other features, objects, and advantages will become apparent from the description and drawings, and from the claims. [Brief description of the drawings]

[0012] [Figure 1]

[0012] A block diagram illustrating an example system that implements techniques for streaming media data over a network. [Diagram 2]

[0013] FIG. 2 is a block diagram illustrating an exemplary set of components of a removal unit. [Diagram 3]

[0014] FIG. 1 is a conceptual diagram illustrating elements of exemplary multimedia content. [Figure 4]

[0015] 1 is a block diagram showing elements of an exemplary video file that may correspond to segments of a presentation. [Diagram 5]

[0016] FIG. 1 is a conceptual diagram illustrating an example low latency architecture that may be used in a first use case in accordance with the present disclosure. [Figure 6]

[0017] FIG. 6 is a conceptual diagram illustrating in further detail one example of the use case described with respect to FIG. 5. [Figure 7]

[0018] A conceptual diagram illustrating an exemplary second specification case using DASH and CMAF random access in the context of a broadcast protocol. [Figure 8]

[0019] 1 is a conceptual diagram illustrating an example signaling of Stream Access Points (SAPs) in a manifest file. [Figure 9]

[0020] 1 is a flowchart illustrating an example method for retrieving media data in accordance with techniques of this disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013]

[0021] The techniques of this disclosure may be applied to video files that conform to video data encapsulated according to any of the ISO Base Media File Format, the Scalable Video Coding (SVC) file format, the Advanced Video Coding (AVC) file format, the 3rd Generation Partnership Project (3GPP®) file format, and / or the Multiview Video Coding (MVC) file format, or other similar video file formats.

[0014]

[0022] In HTTP streaming, frequently used operations include HEAD, GET, and partial GET. The HEAD operation retrieves the header of a file associated with a given Uniform Resource Locator (URL) or Uniform Resource Name (URN) without retrieving the payload associated with the URL or URN. The GET operation retrieves the entire file associated with a given URL or URN. The partial GET operation receives a byte range as an input parameter and retrieves several consecutive bytes of a file, where the number of bytes corresponds to the received byte range. Thus, a movie fragment for HTTP streaming may be provided, since the partial GET operation can obtain one or more individual movie fragments. In a movie fragment, there may be several track fragments of different tracks. In HTTP streaming, a media presentation may be a structured collection of data that is accessible to a client. A client may request and download media data information to present a streaming service to a user.

[0015]

[0023] In an example of streaming 3GPP data using HTTP streaming, there may be multiple representations for video and / or audio data of the multimedia content. As described below, the different representations may correspond to different coding characteristics (e.g., different profiles or levels of a video coding standard), different coding standards or extensions of a coding standard (such as multiview and / or scalable extensions), or different bit rates. A manifestation of such representations may be defined in a Media Presentation Description (MPD) data structure. A media presentation may correspond to a structured collection of data that is accessible to an HTTP streaming client device. An 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 an MPD data structure, which may include updates to the MPD.

[0016]

[0024] A media presentation may include a sequence of one or more periods. Each period may last until the start of the next period or, in the case of the last period, until the end of the media presentation. Each period may include one or more representations in the same media content. A representation may be one of several alternative encoded versions of audio, video, timed text, or other such data. Representations may vary by encoding type, e.g., in the case of video data, by bit rate, resolution, and / or codec, and in the case of audio data, by bit rate, language, and / or codec. The term representation may be used to refer to a section of encoded audio or video data that corresponds to a particular period of the multimedia content and that has been encoded in a particular way.

[0017]

[0025] Representations for a particular period may be assigned to a group indicated by an attribute in the MPD indicating the adaptation set to which the representation belongs. Representations in the same adaptation set are generally considered alternatives to one another in that a client device may 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 to decode for presenting media data, such as video data or audio data, of the multimedia content for the corresponding period. Media content within a period may, in some examples, be represented by either one representation from group 0, if present, or a combination of at most one representation from each non-zero group. Timing data for each representation of a period may be expressed relative to a start time of the period.

[0018]

[0026] 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 include initialization information for accessing the representation. Generally, the initialization segment does not include media data. A segment may be uniquely referenced by an identifier, such as a Uniform Resource Locator (URL), Uniform Resource Name (URN), or Uniform Resource Identifier (URI). The MPD may provide an identifier for each segment. In some examples, the MPD may also provide a byte range in the form of a range attribute that may correspond to data for a segment within a file accessible by a URL, URN, or URI.

[0019]

[0027] Different representations may be selected for substantially simultaneous retrieval of different types of media data. For example, a client device may select an audio representation, a video representation, and a timed text representation from which to retrieve segments. In some examples, a client device may select a particular adaptation set for performing bandwidth adaptation. That is, the client device may select an adaptation set that includes a video representation, an adaptation set that includes an audio representation, and / or an adaptation set that includes timed text. Alternatively, a client device may select an adaptation set for one type of media (e.g., video) and directly select representations for other types of media (e.g., audio and / or timed text).

[0020]

[0028] Low Latency Dynamic Adaptive Streaming over HTTP (LL-DASH) is a profile for DASH that attempts to provide media data to DASH clients with low latency. Some of the techniques for LL-DASH are briefly summarized below. · The encoding is based on fragmented ISO BMFF files, typically CMAF fragments and CMAF chunks are assumed. Each chunk is individually accessible by the DASH packager and is mapped to an HTTP chunk that is uploaded to the origin server. This one-to-one mapping is a recommendation for low-latency operation, but is not a requirement. Clients should never assume that this one-to-one mapping is stored on the client. A low latency protocol for partially available segments, such as HTTP chunked transfer encoding, is used so that clients can access the segment before it is completed. The availability start time is adjusted for clients that can take advantage of this feature. Two operating modes are permitted:

[0021] ○ Simple live offerings are used by applying @duration signaling and $Number$-based templating.

[0022] ○ Main live offerings that have SegmentTimeline as either $Number$ or $Time$ will be supported by the updates proposed in DASH 4th edition. · MPD expiration events may be used but are not required to be understood by clients. In general, in-band event messages may be present, but clients are only expected to recover them at the start of a segment, not in any chunk. DASH packagers may receive notifications from the encoder at chunk boundaries, or completely asynchronously using timed metadata tracks. · In a single media presentation, it is permitted to have an adaptation set using chunked low latency mode and an adaptation set using short segments for different media types within one period of the media presentation. A certain amount of playback control of the DASH client on the media pipeline may be available and should be used for robustness of the DASH client. For example, playback may be accelerated or decelerated for a period of time, or the DASH client may perform seeks to segments. The system will be designed to be run on standard HTTP / 1.1, but should also be applicable to HTTP extensions and other protocols for improved low-latency operation. · The MPD includes explicit signaling in service configuration and service properties (including, for example, the target latency of the service). The MPD and possibly also the segments contain an anchor time that allows DASH clients to measure the current latency compared to live and adjust to meet service expectations. · Operational robustness is targeted in case of e.g. encoder failures. · Existing DRM and encryption modes are compatible with the proposed low latency operation.

[0023]

[0029] Based on the high-level overview above, the following is defined: Segments may be used to randomly access representations not only at segment boundaries but also within segments. If such random access is given, this should be signaled in the MPD.

[0024]

[0030] 1 is a block diagram illustrating an example system 10 that implements techniques for streaming media data over a network. In this example, the system 10 includes a content creation device 20, a server device 60, and a client device 40. The client device 40 and the server device 60 are communicatively coupled by a network 74, which may comprise the Internet. In some examples, the content creation device 20 and the server device 60 may also be coupled by the network 74 or another network, or may be communicatively coupled directly. In some examples, the content creation device 20 and the server device 60 may comprise the same device.

[0025]

[0031] 1 example, content creation device 20 comprises audio source 22 and video source 24. Audio source 22 may comprise, for example, a microphone generating electrical signals representative of captured audio data to be encoded by audio encoder 26. Alternatively, audio source 22 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 24 may comprise a video camera generating video data to be encoded by video encoder 28, a storage medium encoded with previously recorded video data, a video data generation unit such as a computer graphics source, or any other source of video data. Content creation device 20 is not necessarily communicatively coupled to server device 60 in all examples, but may store multimedia content on separate media that is read by server device 60.

[0026]

[0032] The raw audio and video data may comprise analog or digital data. Analog data may be digitized before being encoded by audio encoder 26 and / or video encoder 28. Audio source 22 may obtain audio data from call participants while they are speaking, and video source 24 may simultaneously obtain video data of the call participants. In other examples, audio source 22 may comprise a computer-readable storage medium comprising stored audio data, and video source 24 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 archived, pre-recorded audio and video data.

[0027]

[0033] An audio frame corresponding to a video frame is generally an audio frame that includes audio data captured (or generated) by audio source 22 contemporaneously with video data captured (or generated) by video source 24 that is included within the video frame. For example, audio source 22 captures audio data while call participants generate audio data, typically by speaking, and contemporaneously, i.e., while audio source 22 is capturing audio data, video source 24 captures video data of the call participants. Thus, an audio frame may correspond in time to one or more particular video frames. Thus, an audio frame corresponding to a video frame generally corresponds to situations where audio data and video data are captured contemporaneously and where audio and video frames comprise contemporaneously captured audio and video data, respectively.

[0028]

[0034] In some examples, audio encoder 26 may encode a timestamp in each encoded audio frame that represents the time that the audio data for the encoded audio frame was recorded, and similarly, video encoder 28 may encode a timestamp in each encoded video frame that represents the time that the video data for the encoded video frame was recorded. In such examples, audio frames corresponding to a video frame may comprise an audio frame with a timestamp and a video frame with the same timestamp. Content creation device 20 may include internal clocks from which audio encoder 26 and / or video encoder 28 may generate timestamps or which audio source 22 and video source 24 may use to associate audio data and video data, respectively, with timestamps.

[0029]

[0035] In some examples, audio source 22 may send data to audio encoder 26 corresponding to the time the audio data was recorded, and video source 24 may send data to video encoder 28 corresponding to the time the video data was recorded. In some examples, audio encoder 26 may encode sequence identifiers in the encoded audio data to indicate the relative time ordering of the encoded audio data without necessarily indicating the absolute time the audio data was recorded, and similarly, video encoder 28 may use sequence identifiers to indicate the relative time ordering of the encoded video data. Similarly, in some examples, the sequence identifiers may be mapped to or possibly correlated with timestamps.

[0030]

[0036] The audio encoder 26 generally produces a stream of coded audio data, while the video encoder 28 produces a stream of coded 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, a coded video or audio portion of a representation may be an elementary stream. An elementary stream may be converted into a Packetized Elementary Stream (PES) before being encapsulated within a video file. Within the same representation, a stream ID may be used to distinguish PES packets belonging to one elementary stream from others. The basic data unit of an elementary stream is the Packetized Elementary Stream (PES) packet. Thus, coded video data generally corresponds to an elementary video stream. Similarly, audio data corresponds to one or more respective elementary streams.

[0031]

[0037] Many video coding standards, such as ITU-T H.264 / AVC and the upcoming High Efficiency Video Coding (HEVC) standard, define syntax, semantics, and decoding processes for error-free bitstreams, all of which conform to a particular profile or level. Video coding standards do not usually specify the encoder, but the encoder is tasked with ensuring that the generated bitstream conforms to the standard for the decoder. In the context of video coding standards, a "profile" corresponds to a subset of algorithms, features, or tools and the constraints applied to them. For example, the "profile" defined by the H.264 standard is a subset of the entire bitstream syntax specified by the H.264 standard. A "level" corresponds to a limit on decoder resource consumption, such as decoder memory and computation related to picture resolution, bitrate, 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.

[0032]

[0038] The H.264 standard acknowledges that within the boundaries imposed by the syntax of a given profile, it may still require large variations in encoder and decoder performance depending on the values ​​taken by syntax elements in the bitstream, such as the specified size of a decoded picture. The H.264 standard further acknowledges that in many applications, it is neither practical nor economical to implement a decoder capable of handling all hypothetical uses of the syntax in a particular profile. Thus, the H.264 standard defines a "level" as a prescribed set of constraints imposed on the values ​​of syntax elements in the bitstream. These constraints may be simple restrictions on values. Alternatively, these constraints may take the form of constraints on arithmetic combinations of values ​​(e.g., picture width x picture height x number of pictures decoded per second). The H.264 standard further specifies that individual implementations may support different levels for each supported profile.

[0033]

[0039] A decoder conforming to a profile typically supports all features defined in the profile. For example, as a coding feature, B-picture coding is not supported in the baseline profile of H.264 / AVC, but is supported in other profiles of H.264 / AVC. A decoder conforming to a level should be able to decode any bitstream that does not require resources beyond the limits defined in the level. The definition of the profile and the level may be useful for explainability. For example, during video transmission, a pair of profile definition and level definition may be negotiated and agreed upon for the entire transmission session. More specifically, in H.264 / AVC, a level may define the limits on the number of macroblocks that need to be processed, the decoded picture buffer (DPB) size, the coded picture buffer (CPB) size, the vertical motion vector range, the maximum number of motion vectors per two consecutive MBs, and whether a B block can have a sub-macroblock partition of less than 8×8 pixels. In this way, the decoder may determine whether it is able to properly decode the bitstream.

[0034]

[0040] In the example of Figure 1, encapsulation unit 30 of content creation device 20 receives an elementary stream comprising coded video data from video encoder 28 and an elementary stream comprising coded audio data from audio encoder 26. In some examples, video encoder 28 and audio encoder 26 may each include a packetizer for forming PES packets from the coded data. In other examples, video encoder 28 and audio encoder 26 may each interface with a respective packetizer for forming PES packets from the coded data. In yet other examples, encapsulation unit 30 may include packetizers for forming PES packets from the coded audio data and the coded video data.

[0035]

[0041] Video encoder 28 may encode the video data of the multimedia content in various ways to generate different representations of the multimedia content with various characteristics, such as at various bit rates, pixel resolutions, frame rates, compliance with various coding standards, compliance with various profiles and / or levels of profiles for various coding standards, representations with one or more views (e.g., for two-dimensional or three-dimensional playback), or other such characteristics. A representation as used in this disclosure may comprise one of audio data, video data, text data (e.g., for closed captioning), or other such data. A 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 30 is responsible for assembling the elementary streams into video files (e.g., segments) of the various representations.

[0036]

[0042] Encapsulation unit 30 receives PES packets of the representation elementary stream from audio encoder 26 and video encoder 28 and forms corresponding network abstraction layer (NAL) units from the PES packets. Coded video segments may be organized into NAL units that provide a "network friendly" video representation that addresses applications such as video telephony, storage, broadcast, or streaming. NAL units may be classified into video coding layer (VCL) NAL units and non-VCL NAL units. VCL units may include 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, typically presented as a primary coded picture, may be included in an access unit that may include one or more NAL units.

[0037]

[0043] Non-VCL NAL units may include, among others, parameter set NAL units and SEI NAL units. Parameter sets may include sequence level header information (in sequence parameter sets (SPS)) and infrequently changing picture level header information (in picture parameter sets (PPS)). With parameter sets (e.g., PPS and SPS), infrequently changing information does not need to be repeated for each sequence or picture, and thus coding efficiency may be improved. Furthermore, the use of parameter sets may enable out-of-band transmission of important header information, avoiding the need for redundant transmission for error resilience. In an example of out-of-band transmission, parameter set NAL units may be transmitted on a different channel than other NAL units, such as SEI NAL units.

[0038]

[0044] Supplemental enhancement information (SEI) may include information that is not necessary for decoding coded picture samples from a VCL NAL unit, but may assist processes related to decoding, display, error resilience, and other purposes. SEI messages may be included in non-VCL NAL units. SEI messages are normative parts of some standard specifications and therefore are not always required for a decoder implementation that conforms to the standard. The SEI messages may be sequence-level SEI messages or picture-level SEI messages. Some sequence-level information may be included within SEI messages, such as the scalability information SEI message in the SVC example, the view scalability information SEI message in MVC, and so on. These exemplary SEI messages may carry, for example, information regarding the extraction of operation points and characteristics of those operation points. In addition, the encapsulation unit 30 may form a manifest file, such as a media presentation descriptor (MPD) that describes characteristics of the representation. The encapsulation unit 30 may format the MPD according to the extensible markup language (XML).

[0039]

[0045] The encapsulation unit 30 may provide data for one or more representations of the multimedia content along with a manifest file (e.g., MPD) to the output interface 32. The output interface 32 may comprise a network interface or 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 a magnetic or flash storage medium, or other interface for storing or transmitting media data. The encapsulation unit 30 may provide data for each of the representations of the multimedia content to the output interface 32, which may send the data to the server device 60 via a network transmission or a storage medium. In the example of FIG. 1, the server device 60 includes a storage medium 62 that stores various multimedia content 64, each of which includes a respective manifest file 66 and one or more representations 68A-68N (representations 68). In some examples, the output interface 32 may also send the data directly to the network 74.

[0040]

[0046] In some examples, representations 68 may be separated into adaptation sets, i.e., various subsets of representations 68 may include respective common sets of characteristics, such as codec, profile and level, resolution, number of views, file format of the segments, text type information that may identify the language or other characteristics of the text to be displayed with the representation and / or audio data to be decoded and presented, e.g., by a speaker, camera angle information that may describe the camera angle or real-world camera perspective of the scene for the representations in the adaptation set, rating information that describes the suitability of the content for a particular viewer, etc.

[0041]

[0047] The manifest file 66 may include data indicating a subset of representations 68 that corresponds to a particular adaptation set, as well as common characteristics for the adaptation set. The manifest file 66 may also include data representing individual characteristics for each representation in the adaptation set, such as bit rate. In this manner, the adaptation set may enable simplified network bandwidth adaptation. The representations in an adaptation set may be indicated using child elements of the adaptation set element in the manifest file 66.

[0042]

[0048] Server device 60 includes a request processing unit 70 and a network interface 72. In some examples, server device 60 may include multiple network interfaces. Additionally, any or all of the functionality of server device 60 may be implemented on other devices of the content delivery network, such as routers, bridges, proxy devices, switches, or other devices. In some examples, intermediate devices of the content delivery network may cache data of multimedia content 64 and include components substantially conforming to those of server device 60. In general, network interface 72 is configured to transmit and receive data over network 74.

[0043]

[0049] The request processing unit 70 is configured to receive network requests for data of the storage medium 62 from a client device, such as the client device 40. For example, the request processing unit 70 may implement the Hypertext Transfer Protocol (HTTP) version 1.1, as described in RFC 2616, "Hypertext Transfer Protocol - HTTP / 1.1," by R. Fielding et al., Network Working Group, IETF, June 1999. That is, the request processing unit 70 may be configured to receive HTTP GET requests or partial GET requests and provide data of the multimedia content 64 in response to these requests. The request may specify a segment of one of the representations 68, for example, using the URL of the segment. In some examples, the request may also specify one or more byte ranges of the segment and thus comprise a partial GET request. The request processing unit 70 may further be configured to service an HTTP HEAD request to provide header data of a segment of one of the representations 68. In either case, the request processing unit 70 may be configured to process a request to provide the requested data to a requesting device, such as the client device 40.

[0044]

[0050] Additionally or alternatively, the request processing unit 70 may be configured to deliver the media data via a broadcast or multicast protocol, such as eMBMS. Although the content creation device 20 may create DASH segments and / or subsegments in substantially the same manner as described, the server device 60 may deliver these segments or subsegments using eMBMS or another broadcast or multicast network transport protocol. For example, the request processing unit 70 may be configured to receive a multicast group join request from the client device 40. That is, the server device 60 may advertise an Internet Protocol (IP) address associated with the multicast group to client devices associated with the particular media content (e.g., a broadcast of a live event), including the client device 40. The client device 40 may in turn submit a request to join the multicast group. This request may be propagated throughout the network 74, for example, to routers constituting the network 74, such that the routers are caused to direct traffic destined for the IP address associated with the multicast group to the subscribing client device, such as the client device 40.

[0045]

[0051] 1, multimedia content 64 includes a manifest file 66, which may correspond to a media presentation description (MPD). Manifest file 66 may include descriptions of different alternative representations 68 (e.g., video services having different qualities), which may include, for example, codec information, profile values, level values, bit rates, and other descriptive characteristics of representations 68. Client device 40 may retrieve the MPD of the media presentation to determine how to access segments of representation 68.

[0046]

[0052] In particular, the retrieval unit 52 may retrieve configuration data (not shown) of the client device 40 to determine the decoding capabilities of the video decoder 48 and the rendering capabilities of the video output 44. The configuration data may also include any or all of a language preference selected by a user of the client device 40, one or more camera perspectives corresponding to a depth preference set by the user of the client device 40, and / or a rating preference selected by the user of the client device 40. The retrieval unit 52 may comprise, for example, a web browser or a media client configured to submit HTTP GET requests and partial GET requests. The retrieval unit 52 may correspond to software instructions executed by one or more processors or processing units (not shown) of the client device 40. In some examples, all or part of the functionality described with respect to the retrieval unit 52 may be implemented in hardware or a combination of hardware, software, and / or firmware, and requisite hardware may be provided to execute software or firmware instructions.

[0047]

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

[0048]

[0054] Generally, a higher bit rate representation may result in higher quality video playback, but when available network bandwidth decreases, a lower bit rate representation may provide sufficient quality video playback. Thus, when available network bandwidth is relatively high, retrieval unit 52 may retrieve data from a relatively high bit rate representation, but when available network bandwidth is low, retrieval unit 52 may retrieve data from a relatively low bit rate representation. In this manner, client device 40 may adapt to changing network bandwidth availability of network 74 while streaming multimedia data over network 74.

[0049]

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

[0050]

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

[0051]

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

[0052]

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

[0053]

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

[0054]

[0060] Encapsulation unit 30 may also assemble an access unit from multiple NAL units. In general, an access unit may comprise one or more NAL units for representing a frame of video data and audio data corresponding to the frame, when such audio data is available. An access unit generally includes all NAL units over one output time instance, e.g., all audio data and video data over one time instance. For example, if each view has a frame rate of 20 frames per second (fps), each time instance may correspond to a time interval of 0.05 seconds. During this time interval, unique frames of all views of the same access unit (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.

[0055]

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

[0056]

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

[0057]

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

[0058]

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

[0059]

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

[0060]

[0066] According to the techniques of this disclosure, content creation device 20 and / or server device 60 may add additional random access points in DASH / CMAF segments. Random access includes clean random access and open or gradual decoder refresh, all the way up to providing resynchronization only at file format parsing. This may be addressed by providing chunk boundaries that provide information that resynchronization and decoding may begin at this point, and signaling regarding the type of random access point below. The availability of tfdt, along with the use of moof header information and possibly initialization segments, allows time resynchronization at the presentation time level. This disclosure refers to this new point as a "resynchronization point." That is, a resynchronization point represents a point where a file level container (e.g., a box in ISO BMFF) may be parsed properly, followed by a random access point in the media data (e.g., an I-frame). Thus, client device 40 may randomly access multimedia content 64, for example, at one of these random access points.

[0061]

[0067] Content creation device 20 and / or server device 60 may also add appropriate signaling in manifest file 66 (e.g., MPD) indicating the availability of random access points and resynchronization in each DASH segment, as well as providing information regarding the location, type, and timing of the random access points. Content creation device 20 and / or server device 60 may provide signaling in manifest file 66 (MPD) indicating that additional resynchronization points are available in the segment, possibly adding characteristics regarding the random access position, timing, type, and whether the information is accurate or estimated. Client device 40 may thus use this signaled data to determine whether such random access points are available and resynchronize retrieval and playback accordingly.

[0062]

[0068] Client device 40 may be configured with the ability to resynchronize to decapsulate, decrypt, and decode for any starting point by finding a resynchronization point. Content creation device 20 and / or server device 60 may provide appropriate chunks that meet the above requirements addressed in the CMAF TUC. Different types may be defined later.

[0063]

[0069] The client device 40 may be configured to initiate processing in a limited receiver environment, for example, as is available in HTML-5 / MSE-based playback. This issue may be addressed through the receiver implementation. However, it may be appropriate to provide resynchronization triggers and information to a receiver pipeline that has the ability to obtain a map of resynchronization points in data structure, timing, and type, which allows the user of the decoding pipeline to initialize playback at a random access point.

[0064]

[0070] Additionally, signaling in the manifest file 66 may be provided that is backward compatible. Client devices that are not configured with the ability to parse the signaling may ignore the signaling and perform the methods described above. Additionally, the manifest file 66 may include signaling that associates a location with a value of @bandwidth to enable signaling at the adaptation set level.

[0065]

[0071] Figure 2 is a block diagram illustrating in more detail an exemplary set of components of retrieval unit 52 of Figure 1. In this example, retrieval unit 52 includes an eMBMS middleware unit 100, a DASH client 110, and a media application 112.

[0066]

[0072] In this example, the eMBMS middleware unit 100 further includes an eMBMS receiving unit 106, a cache 104, and a proxy server unit 102. In this example, the eMBMS receiving unit 106 is configured to receive data via eMBMS in accordance with File Delivery over Unidirectional Transport (FLUTE), e.g., as described in T. Paira et al., “FLUTE - File Delivery over Unidirectional Transport”, Network Working Group, RFC6726, November 2012, available at tools.ietf.org / html / rfc6726. That is, the eMBMS receiving unit 106 may receive files via broadcast from a server device 60, which may act as, e.g., a Broadcast / Multicast Service Center (BM-SC).

[0067]

[0073] When the eMBMS middleware unit 100 receives data for a file, the eMBMS middleware unit may store the received data in cache 104. Cache 104 may comprise a computer-readable storage medium, such as flash memory, a hard disk, RAM, or any other suitable storage medium.

[0068]

[0074] The proxy server unit 102 may act as a server for the DASH client 110. For example, the proxy server unit 102 may provide the DASH client 110 with an MPD file or other manifest file. The proxy server unit 102 may advertise availability times for segments in the MPD file and hyperlinks from which the segments may be retrieved. These hyperlinks may include a local host address prefix (e.g., 127.0.0.1 for IPv4) corresponding to the client device 40. In this manner, the DASH client 110 may request segments from the proxy server unit 102 using an HTTP GET or partial GET request. For example, for a segment available from the link http: / / 127.0.0.1 / rep1 / seg3, the DASH client 110 may construct an HTTP GET request that includes a request for http: / / 127.0.0.1 / rep1 / seg3 and submit the request to the proxy server unit 102. The proxy server unit 102 may retrieve requested data from the cache 104 and provide the data to the DASH client 110 in response to such a request.

[0069]

[0075] FIG. 3 is a conceptual diagram illustrating elements of an exemplary multimedia content 120. The multimedia content 120 may correspond to the multimedia content 64 (FIG. 1) or another multimedia content stored in the storage medium 62. In the example of FIG. 3, the multimedia content 120 includes a media presentation description (MPD) 122 and a number of representations 124A-124N (representations 124). Representation 124A includes optional header data 126 and segments 128A-128N (segments 128), and representation 124N includes optional header data 130 and segments 132A-132N (segments 132). The letter N is used for convenience to designate the last movie fragment in each of the representations 124. In some examples, there may be different numbers of movie fragments among the representations 124.

[0070]

[0076] MPD 122 may comprise a data structure separate from representation 124. MPD 122 may correspond to manifest file 66 of Figure 1. Similarly, representation 124 may correspond to representation 68 of Figure 1. In general, MPD 122 may include data that generally describes characteristics of representation 124, such as coding and rendering characteristics, adaptation sets, profiles to which MPD 122 supports, text type information, camera angle information, rating information, trick mode information (e.g., information indicative of a representation that includes a time subsequence), and / or information for retrieving a remote period (e.g., for targeted advertisement insertion into the media content being played).

[0071]

[0077] Header data 126, when present, may describe characteristics of segment 128, such as the time location of a random access point (RAP, also called a stream access point (SAP)) of segment 128, including the random access point, a byte offset to the random access point within segment 128, a uniform resource locator (URL) for segment 128, or other aspects of segment 128. Header data 130, when present, may describe similar characteristics for segment 132. Additionally or alternatively, such characteristics may be contained entirely within MPD 122.

[0072]

[0078] Segments 128, 132 include one or more coded video samples, each of which may include a frame or slice of video data. Each of the coded video samples of segment 128 may have similar characteristics, e.g., height, width, and bandwidth requirements. Such characteristics may be described by data in MPD 122, although such data is not shown in the example of FIG. 3. MPD 122 may include characteristics described by 3GPP specifications in addition to any or all of the signaled information described in this disclosure.

[0073]

[0079] Each of the segments 128, 132 may be associated with a unique Uniform Resource Locator (URL). Thus, each of the segments 128, 132 may be independently retrievable using a streaming network protocol such as DASH. In this manner, a destination device, such as the client device 40, may use an HTTP GET request to retrieve a segment 128 or 132. In some examples, the client device 40 may use an HTTP partial GET request to retrieve a particular byte range of the segment 128 or 132.

[0074]

[0080] In accordance with the techniques of this disclosure, the MPD 122 (which may also correspond to the manifest file 66 of FIG. 1) may include signaling to address the issues discussed above. For example, for each of the representations 124 (and possibly defaulted at the adaptation set level), the MPD 122 may include one or more resynchronization elements (which may enable backward compatibility). Each resynchronization element may indicate that for each of the segments 128, 132 in the corresponding one of the representations 124, the following holds: · A resynchronization point of Stream Access Point (SAP) type of @type or smaller (but greater than 0) exists within each segment with maximum delta T signaled by @dT, maximum byte offset difference signaled by @dImax, and minimum byte offset difference signaled by @dImin, where both the values ​​of @dImax and @dImin must be multiplied by the value of the @bandwidth attribute assigned to this representation to obtain a value. "Delta T" refers to the difference in the earliest presentation time of any data following a resynchronization point in units of the representation's @timescale. If @type is set to 0, only resynchronization with respect to the container and decoding level is guaranteed. · The resync marker flag @marker may be set to indicate that a resync point is included for every resync point, using the resync pattern defined by the segment format in use. · Multiple resynchronization elements can exist for different SAP types. · The resynchronization point requires that media processing can occur on the ISO BMFF and decryption information in combination with the CMAF header / initialization segment.

[0075]

[0081] An example use of a resynchronization point is described with respect to FIG. 8 below.

[0076]

[0082] For resynchronization elements provided in the MPD 122 and segments 128, 132 based on either ISO BMFF or CMAF, the following may hold: A segment can be a sequence of one or more chunks, as defined below. Furthermore, for any two consecutive resynchronization points in a segment of the @type specified in the element, the following may hold: The difference between the two earliest presentation times can be at most the value of @dT.

[0077] ○ The difference in byte offset from the start can be at most @dImax normalized by the @bandwidth value.

[0078] o The difference in byte offset from the start will be at least @dImin normalized by the @bandwidth value. If the resync marker flag is set, each resync point may contain a resync box / styp.

[0079]

[0083] FIG. 4 is a block diagram illustrating elements of an exemplary video file 150 that may correspond to a segment of a representation, such as one of the segments 128, 132 of FIG. 3. Each of the segments 128, 132 may include data that substantially corresponds to an arrangement of data shown in the example of FIG. 4. The video file 150 may be said to encapsulate a segment. As explained above, video files according to the ISO Base Media File Format and its extensions store data in a series of objects called "boxes." In the example of FIG. 4, the video file 150 includes a file type (FTYP) box 152, a movie (MOOV) box 154, a segment index (sidx) box 162, a movie fragment (MOOF) box 164, and a movie fragment random access (MFRA) box 166. Although FIG. 4 represents an example 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, etc.) structured similarly to the data of the video file 150 according to the ISO Base Media File Format and its extensions.

[0080]

[0084] The file type (FTYP) box 152 generally describes the file type of the video file 150. The file type box 152 may contain data identifying specifications that describe the best use of the video file 150. The file type box 152 may alternatively be placed before the MOOV box 154, the Movie Fragment box 164, and / or the MFRA box 166.

[0081]

[0085] In some examples, a segment such as video file 150 may include an MPD update box (not shown) before FTYP box 152. The MPD update box may include information indicating that the MPD corresponding to a representation that includes video file 150 should be updated, along with information for updating the MPD. For example, the MPD update box may provide a URI or URL for a resource used to update the MPD. As another example, the MPD update box may include data for updating the MPD. In some examples, the MPD update box may immediately follow a segment type (STYP) box (not shown) of video file 150, where the STYP box may define the segment type of video file 150.

[0082]

[0086] 4, MOOV box 154 includes a Movie Header (MVHD) box 156, a Track (TRAK) box 158, and one or more Movie Extension (MVEX) boxes 160. Generally, MVHD box 156 may describe general characteristics of video file 150. For example, MVHD box 156 may include data describing when video file 150 was originally created, when video file 150 was last modified, a timeline of video file 150, the duration of playback of video file 150, or other data generally describing video file 150.

[0083]

[0087] TRAK box 158 may contain data about a track of video file 150. TRAK box 158 may contain a Track Header (TKHD) box that describes characteristics of the track that corresponds to TRAK box 158. In some examples, TRAK box 158 may contain coded video pictures, while in other examples, the coded video pictures for the track may be contained in a movie fragment 164 that may be referenced by data in TRAK box 158 and / or sidx box 162.

[0084]

[0088] In some examples, video file 150 may include more than one track. Thus, MOOV box 154 may include a number of TRAK boxes equal to the number of tracks in video file 150. TRAK box 158 may describe characteristics of the corresponding track of video file 150. For example, TRAK box 158 may describe time and / or spatial information for the corresponding track. When encapsulation unit 30 (FIG. 3) includes a parameter set track in a video file, such as video file 150, a TRAK box similar to TRAK box 158 of MOOV box 154 may describe characteristics of the parameter set track. Encapsulation unit 30 may signal the presence of a sequence level SEI message in the parameter set track in a TRAK box that describes the parameter set track.

[0085]

[0089] MVEX box 160 may, for example, describe characteristics of the corresponding movie fragment 164, to signal that video file 150 includes movie fragment 164 in addition to the video data contained in MOOV box 154, if any. In the context of streaming video data, coded video pictures may be contained in movie fragment 164 rather than MOOV box 154. Thus, all coded video samples may be contained in movie fragment 164 rather than MOOV box 154.

[0086]

[0090] The MOOV box 154 may contain a number of MVEX boxes 160 equal to the number of movie fragments 164 in the video file 150. Each of the MVEX boxes 160 may describe the characteristics of a corresponding one of the movie fragments 164. For example, each MVEX box may include a Movie Extension Header Box (MEHD) box that describes the duration of the corresponding one of the movie fragments 164.

[0087]

[0091] As mentioned above, encapsulation unit 30 may store the sequence data set in a video sample that does not contain actual coded video data. A video sample may generally correspond to an access unit, which is a representation of a coded picture at a particular time instance. In the context of AVC, a coded picture includes one or more VCL NAL units that contain information for configuring all pixels of an access unit, and other associated non-VCL NAL units, such as SEI messages. Thus, encapsulation unit 30 may include a sequence data set, which may include a sequence level SEI message, in one of the movie fragments 164. Encapsulation unit 30 may further signal the presence of the sequence data set and / or the sequence level SEI message as present in one of the movie fragments 164 in one of the MVEX boxes 160 that corresponds to one of the movie fragments 164.

[0088]

[0092] The SIDX box 162 is an optional element of the video file 150; that is, a video file that conforms to the 3GPP file format, or other such file formats, does not necessarily include the SIDX box 162. According to an example 3GPP file format, the SIDX box may be used to identify a subsegment of a segment (e.g., a segment contained within the video file 150). The 3GPP file format defines a subsegment as "a self-contained set of one or more consecutive Movie Fragment boxes with a corresponding Media Data box and a Media Data box containing data referenced by the Movie Fragment box, which must follow the Movie Fragment box and precede the next Movie Fragment box containing information about the same track." The 3GPP file format also indicates that the SIDX box "contains a sequence of references to subsegments of the (sub)segment documented by the box. The referenced subsegments are contiguous in presentation time. Similarly, the bytes referenced by the Segment Index box are always contiguous within the segment. The referenced size gives a count of the number of bytes in the referenced material."

[0089]

[0093] The SIDX box 162 generally provides information describing one or more subsegments of a segment contained in the video file 150. For example, such information may include the playback time at which the subsegment starts and / or ends, the byte offset of the subsegment, whether the subsegment contains (e.g., starts at) a Stream Access Point (SAP), the type of SAP (e.g., whether the SAP is an Instantaneous Decoder Refresh (IDR) picture, a Clean Random Access (CRA) picture, a Cut Link Access (BLA) picture, etc.), the location of the SAP (with respect to playback time and / or byte offset) within the subsegment, etc.

[0090]

[0094] A movie fragment 164 may include one or more coded video pictures. In some examples, a movie fragment 164 may include one or more groups of pictures (GOPs), each of which may include several coded video pictures, e.g., frames or pictures. Additionally, as described above, a movie fragment 164 may include a sequence data set in some examples. Each of the movie fragments 164 may include a Movie Fragment Header Box (MFHD, not shown in FIG. 4). The MFHD box may describe characteristics of the corresponding movie fragment, such as the sequence number of the movie fragment. The movie fragments 164 may be included in the video file 150 in order of sequence number.

[0091]

[0095] The MFRA box 166 may describe random access points within the movie fragments 164 of the video file 150. This may assist in implementing trick modes, such as implementing a seek to a particular time location (i.e., play time) within a segment encapsulated by the video file 150. The MFRA box 166 is generally optional and, in some examples, need not be included in the video file. Similarly, a client device, such as the client device 40, does not necessarily need to reference the MFRA box 166 to correctly decode and display the video data of the video file 150. The MFRA box 166 may include a number of track fragment random access (TFRA) boxes (not shown) equal to the number of tracks of the video file 150, or, in some examples, equal to the number of media tracks (e.g., non-hint tracks) of the video file 150.

[0092]

[0096] In some examples, the movie fragment 164 may include one or more stream access points (SAPs), such as an IDR picture. Similarly, the MFRA box 166 may provide an indication of the location of the SAPs within the video file 150. Thus, a temporal subsequence of the video file 150 may be formed from the SAPs of the video file 150. The temporal subsequence may also include other pictures, such as P-frames and / or B-frames, that are dependent on the SAPs. The frames and / or slices of the temporal subsequence may be organized into segments such that frames / slices of the temporal subsequence that depend on other frames / slices of the subsequence may be properly decoded. For example, in a hierarchical organization of data, data used for prediction of other data may also be included in the temporal subsequence.

[0093]

[0097] In one example, this disclosure defines a "chunk" as follows in the table below: This table provides an example definition of both the cardinality and ordinality of a chunk:

[0094] [Table 1]

[0095]

[0098] In one example, this disclosure defines a resynchronization point as the start of a chunk. Additionally, a resynchronization point may be assigned the following properties: It contains a byte offset from the start of the segment, pointing to the first byte of the chunk. · It has the earliest presentation time derived from the information in the moof and possibly the movie header assigned to it. · It has a SAP type assigned to it as defined in ISO / IEC 14496-12. An indication of whether the chunk contains a resync box (styp above). Starting from the resynchronization point, along with the information in the movie header, file format analysis and decoding can be performed.

[0096]

[0099] In some examples, a resync marker box may be defined that allows synchronization to the start of a segment (e.g., video file 150) by scanning the byte stream for markers. This resync box may have the following properties: It defines a unique pattern for resynchronization with extremely high likelihood. · It defines the SAP type.

[0097]

[0100] The resynchronization marker box may be a new box or may reuse an existing box such as a styp box. In this disclosure, it is assumed that a styp with certain restrictions can be used as a resynchronization marker box. Research on the robustness of this approach is ongoing.

[0098]

[0101] 5-7 below are used to illustrate some use cases where random access to a DASH segment at points other than the start of the segment may be useful.

[0099]

[0102] FIG. 5 is a conceptual diagram illustrating an example low-latency architecture 200 that may be used in a first use case according to the present disclosure. That is, FIG. 5 illustrates a basic flow of information for operating a low-latency DASH service by a DASH-IF IOP. The low-latency architecture 200 includes a DASH packager 202, an encoder 216, a content delivery network (CDN) 220, a normal DASH client 230, and a low-latency DASH client 232. The encoder 216 may generally correspond to either or both of the audio encoder 26 and the video encoder 28 of FIG. 1, while the DASH packager 202 may correspond to the encapsulation unit 30 of FIG. 1.

[0100]

[0103] In this example, the encoder 216 encodes the received media data to form CMAF headers (CHs), such as the CH 208, CMAF initial chunks 206A, 206B (CIC 206), and CMAF non-initial chunks 204A-204D (CNC 204). The encoder 216 provides the CH 208, the CIC 206, and the CNC 204 to the DASH packager 202. The DASH packager 202 also receives a service description that includes information about a general description of the service and an encoder configuration of the encoder 216.

[0101]

[0104] The DASH packager 202 uses the service description, the CH 208, the CIC 206, and the CNC 204 to form a media presentation description (MPD) 210 and an initialization segment 212. The DASH packager 202 also generates maps CH 208, CIC 206, and CNC 204 into segments 214A, 214B (segments 214) and provides the segments 214 in an incremental manner to the CDN 220. The DASH packager 202 may deliver the segments 214 in the form of chunks as they are generated. The CDN 220 includes segment storage 222 for storing the MPD 210, the IS 212, and the segments 214. For example, in response to HTTP Get or partial Get requests from regular DASH clients 230 and low latency DASH clients 232, CDN 220 delivers complete segments to regular DASH clients 230 but delivers individual chunks (e.g., CH 208, CIC 206, and CNC 204) to low latency DASH clients 232.

[0102]

[0105] Figure 6 is a conceptual diagram illustrating in further detail an example of the use case described with respect to Figure 5. The example of Figure 6 shows segments 250A-250E (segments 250) that include respective sets of chunks 252A-252E (chunks 252). A client device, such as client device 40 of Figure 1, may retrieve either the complete segment 250 or individual chunks 252. For example, as shown in Figure 5, a regular DASH client 230 may retrieve the segment 250, while a low latency DASH client 232 may retrieve (at least initially) individual chunks 252.

[0103]

[0106] 6 further illustrates how latency may be reduced by retrieving individual chunks 252 rather than complete segments 250. For example, retrieving a complete segment at the current time may result in higher latency. Simply retrieving the most recent complete available segment reduces latency, but may still result in relatively high latency.

[0104]

[0107] By retrieving chunks instead, these latencies can be significantly reduced. For example, at the current time, indicated by "now" in FIG. 6, segment 250E is not fully formed. Nevertheless, a client device can retrieve formed chunks, such as chunks 252E-1 and 252E-2 of segment 250E, even before segment 250E is fully formed, assuming chunks 252E-1 and 252E-2 are formed and available for retrieval.

[0105]

[0108] When joining a live stream, typically both low latency and fast start-up should be achieved. However, this is not trivial, and several strategies are described below based on FIG. In the first case, at the live edge, segments whose time history is three segments behind (i.e., segments 250B, 250C, and 250D) are loaded into the buffer. Once one segment is available, playback begins. This introduces significant latency, but playback can begin relatively quickly since random access at the start of the segment is loaded. In the second case, segment 250D is selected, the newest available segment, instead of a segment that is 3 segments older. The playback latency in this case is at least the segment duration, but may be longer. Start-up may be similar to the above case. In the other three cases, a segment containing multiple chunks (e.g., segment 250E) is played while it is still being generated. This reduces latency, but the problem exists that the start of playback may be affected, especially if the difference between the segment available start time and the wallclock time of the latest published segment is larger than the target latency. In this case, the client device may have to wait until the next second is emitted. In the case of a 6 second segment, this may result in a start latency of 4-5 seconds. Other techniques and use cases exist. For example, a client could access old segments at the start, download everything, accelerate playback, and do fast-forward decoding. However, such an approach has the drawback that significant data needs to be downloaded before accelerated decoding can occur. Furthermore, it is not widely supported in decoder interfaces.

[0106]

[0109] A suitable solution may be the following: At least one representation of the adaptation set includes more frequent random access points and non-initial chunks in the segment / fragment. · A DASH client may use information from the MPD to determine that such a random access method exists, but the location / byte offset of the random access point may not be precisely signaled. A DASH client can access this representation at startup, but it will only download starting from the byte range of the latest available non-initial chunk, or at least close to it. Once downloaded, the DASH client can determine the random access point and start processing the data along with the initialization segment / CMAF header of the same representation that was also downloaded. Locating the random access point is described below.

[0107]

[0110] However, the latter approach can encounter various problems, as summarized below.

[0108]

[0111] Thus, as shown in the example of FIG. 6 and described below, the use of chunks as described in this disclosure may substantially reduce latency. Signaling the start of a chunk in advance may allow a manifest file to be generated in advance that does not require frequent updates but can still indicate the general location of stream access points (SAPs) within the chunk. In this way, a client device may use the manifest file to determine the location of chunk boundaries without requiring continuous manifest file updates, but still allow the client device to start media streaming at the beginning of a chunk boundary, e.g., at a resynchronization point. That is, a client device may determine from the manifest file the byte range of a segment that includes a resynchronization point even before the segment is fully formed, because the manifest file may signal a byte range or other data that represents the general location of the resynchronization point in the segment.

[0109]

[0112] FIG. 7 is a conceptual diagram illustrating an exemplary second specification case using DASH and CMAF random access in the context of a broadcast protocol. FIG. 7 illustrates an example including a media encoder 280, a CMAF / file format (FF) packager 282, a DASH packager 284, a ROUTE sender 286, a CDN origin server 288, a ROUTE receiver 290, a DASH client 292, a CMAF / FF parser 294, and a media decoder 296. The media encoder 280 encodes media data, such as audio data or video data. The media encoder 280 may correspond to the audio encoder 26 or the video encoder 28 of FIG. 1, or the encoder 216 of FIG. 5. The media encoder 280 provides the encoded media data to the CMAF / FF packager 282, which formats the encoded media data into a file according to CMAF and a particular file format, such as ISO BMFF or an extension thereof.

[0110]

[0113] CMAF / FF packager 282 provides these files (e.g., chunks) to DASH packager 284, which aggregates the files / chunks into DASH segments. DASH packager 284 may also form a manifest file, such as an MPD, that includes data describing the files / chunks / segments. Additionally, in accordance with techniques of this disclosure, DASH packager 284 may determine approximate locations of future stream access points (SAPs) or random access points (RAPs) and signal the approximate locations in the MPD. CMAF / FF packager 282 and DASH packager 284 may correspond to encapsulation unit 30 of FIG. 1 or DASH packager 202 of FIG. 5.

[0111]

[0114] The DASH packager 284 provides the segments, along with the MPD, to a ROUTE sender 286 and a CDN origin server 288. The ROUTE sender 286 and the CDN origin server 288 may correspond to the server device 60 of FIG. 1 or the CDN 220 of FIG. 5. Generally, the ROUTE sender 286 may send media data to a ROUTE receiver 290 according to a ROUTE in this example. In other examples, other file-based delivery protocols, such as FLUTE, may be used for broadcast or multicast. Additionally or alternatively, the CDN origin server 288 may send media data to the ROUTE receiver 290 and / or directly to the DASH client 292, for example, according to HTTP.

[0112]

[0115] The ROUTE receiver 290 may be implemented in a middleware, such as the eMBMS middleware unit 100 of Figure 2. The ROUTE receiver 290 may buffer the received media data, for example, in the cache 104 shown in Figure 2. A DASH client 292 (which may correspond to the DASH client 110 of Figure 2) may retrieve the cached media data from the ROUTE receiver 290 using HTTP. Alternatively, the DASH client 292 may retrieve the media data directly from the CDN origin server 288 according to HTTP, as described above.

[0113]

[0116] Further, according to the techniques of this disclosure, the DASH client 292 may use a manifest file, such as an MPD, to determine the location of SAPs or RAPs, for example, following a resynchronization point signaled in the manifest file. The DASH client 292 may begin retrieving the media presentation starting from the next earliest resynchronization point. The resynchronization point may generally indicate a location in the bitstream where the file container level data can be correctly parsed. Thus, the DASH client 292 may begin streaming starting at the resynchronization point and deliver the received media data starting from the resynchronization point to the CMAF / FF parser 294.

[0114]

[0117] CMAF / FF parser 294 may begin parsing the media data starting from the resynchronization point. CMAF / FF parser 294 may correspond to decapsulation unit 50 of Figure 1. Further, CMAF / FF parser 294 may extract decodable media data from the parsed data and deliver the decodable media data to media decoder 296, which may correspond to audio decoder 46 or video decoder 48 of Figure 1. Media decoder 296 may decode the media data and deliver the decoded media data to a corresponding output device, such as audio output 42 or video output 44 of Figure 1.

[0115]

[0118] In the broadcast case, an example of a combination of DASH / CMAF and ROUTE is shown in Figure 7. In the combination of low-latency DASH mode and ROUTE (e.g., as considered for the DVB TM-IPI Task Force on ABR Multicast and ATSC profiles), the following problems may arise: If the ROUTE receiver 290 joins in the middle of a DASH / CMAF low-latency segment, it cannot start processing data, since no synchronization is available and there is no random access for other purposes. Thus, the start-up is delayed, even if more frequent random access is provided in the middle of the segment.

[0116]

[0119] A suitable solution may be the following: · Broadcast / multicast representations include more frequent random access points and non-initial chunks in segments / fragments. The DASH client 292 determines that such a random access method exists using information in the MPD and / or possibly by information from the ROUTE receiver 290. The DASH client 292 may use such information exactly to locate the random access point, but may not do so. The DASH client 292 has access to this representation at startup, but may not have access to all the information right from the start. Upon starting to access a received portion of a segment, the DASH client 292 may locate a random access point and begin processing the data with the same downloaded initialization segment / CMAF header of the same representation. Locating random access points is described below.

[0117]

[0120] However, the latter approach can encounter various problems, as summarized below.

[0118]

[0121] In a similar case to that described in the second use case above, packet loss may be an issue, as well as during random access resynchronization. In this exemplary third use case, a similar procedure may be applied as described above. There may be other cases where clean random access is attempted, as well as events in non-random access chunks (e.g., without IDR frames), decryption, and presentation may be attempted after sufficient box analysis is possible. Therefore, resynchronization to clean random access is important, as well as random access to file format analysis.

[0119]

[0122] Yet another fourth use case may arise when live media content is typically delivered with low latency, but then the same media content is used with a time shift for delayed playback: A client may want to access a media presentation at a particular time, but this time may not (and typically does not) coincide with a segment / CMAF fragment start.

[0120]

[0123] A suitable solution may be the following: At least one representation of the adaptation set may include more frequent random access points and non-initial chunks in a segment / fragment. · The DASH client 292 may use information from the MPD to determine that such a random access method exists, but the location / byte offset of the random access point may not be known exactly. · A DASH client 292 may access this representation when seeking, but may only be allowed to download starting from, or at least close to, the byte range of the latest available non-initial chunk. Once downloaded, the DASH client 292 can locate the random access point and begin processing the data along with the initialization segment / CMAF header of the same representation that was also downloaded. Locating the random access point is described below.

[0121]

[0124] However, the latter approach can encounter various problems, as summarized below.

[0122]

[0125] Resynchronization in the case of ISO BMFF / DASH / CMAF segments generally involves several processes, which are summarized below. 1) Finding the box structure. 2) Finding the CMAF chunk / fragment that has all the relevant information. 3)Finding timing via mdat and tfdt. 4) Obtain all decryption-related information, if applicable. 5) Possibly process event messages. 6) Initiate decoding at the elementary stream level.

[0123]

[0126] An exemplary method for finding a resynchronization point in a box structure at a particular time is summarized below. If there is a segment index (SIDX box), such a resynchronization point is provided as a presentation time and a byte offset. However, the segment index is typically not available for low latency live, since the segments are not fully formed in advance. If the start of a segment is available, the client may download a minimum set of byte ranges so that the box structure can be processed. Resynchronization is provided by the underlying protocol, providing that for example chunk boundaries are signaled and the client can begin parsing. If the start of a segment cannot be easily determined through the signaled data, the client can find a synchronization pattern that allows the client to randomly access the data. The client can then begin parsing and find the appropriate box structure that allows processing of, for example, emsg, prft, mdat, moof, and / or mdat.

[0124]

[0127] This disclosure describes techniques that may be applied to the fourth example above. The first three represent exemplary simplifications when the corresponding information is available.

[0125]

[0128] The present disclosure recognizes the following problems based on the above discussion and that these problems require solutions. 1) Adding additional random access points during DASH / CMAF segments. Random access can include clean random access and open or gradual decoder refresh, all the way up to providing only resynchronization upon file format parsing. 2) Adding appropriate signaling in the MPD (or other manifest file) that indicates the availability of random access points and resynchronization in each DASH segment and provides information about the location, type, and timing of the random access points. The information can be exact or within a certain range. 3) The ability to resynchronize decapsulation, decryption, and decoding for any starting point by finding a resynchronization point. 4) Ability to initiate processing in constrained receiver environments, for example as available in HTML-5 / MSE based playback.

[0126]

[0129] FIG. 8 is a conceptual diagram illustrating an example signaling of stream access points (SAPs) in a manifest file. In particular, FIG. 8 illustrates bitstream 300 including SAPs 302A-302D (SAP302) and segments 304A-304D (segment 304), and bitstream 310 including SAPs 312A-312D (SAP312), SAPs 316A-316D (SAP316), and segments 314A-314D (segment 314). That is, in this example, segment 314 of bitstream 310 includes SAPs 312, 316 that are more frequent than segment 304 of bitstream 300. Each of SAPs 302, 312 may correspond to both the start of a corresponding one of segments 304, 314 and the first chunk of these segments. SAP 316 may correspond to the start of a chunk within the corresponding segment 316, but not to the beginning of the corresponding segment 316.

[0127]

[0130] To provide a simple technique to achieve a constant bitrate representation using equidistant chunks of 1000 samples (and @timescale=1000 in sample duration) and SAP type 1 (which could be, for example, an audio representation), a resynchronization element can be added:

[0128]

number

[0129]

[0131] A client receiving such information, e.g., client device 40 of FIG. 1, may not be able to identify that for a segment with @duration=10000, a random access point can be accessed every second in the exact byte range. If the bit rate is variable, the receiver (e.g., client device 40) may use @dIMin and @dIMax to identify the range in which to find the random access point. As an alternative to @dT, which signals a maximum value, it may also signal a nominal chunk duration.

[0130]

[0132] The resync element of the manifest file may also contain a URL @index that points to a binary resync index of the resync points in each segment, using the same template function as a normal segment. This resync can provide the exact location of all resync points in a segment, as well as the segment index, if present. If present, the resync index may be available for all segments of the period that is available at the time of issue of the manifest file / MPD.

[0131]

[0133] In one approach, the resync index may be the same as the segment index, but may be altered.

[0132]

[0134] Client device 40 of FIG. 1 may use the ISO BMFF 4-character box type as a basis for resynchronizing to a media file (e.g., video file 150 of FIG. 4, which may be a segment). In one example, the box type selected is a "styp" box, but may also be a "moof" box itself. Random emulation of box string types is extremely rare. A test report of styp emulation is described below. This emulation is then avoided by checking against known expected box types. Client device 40 may perform a resynchronization mechanism outlined as follows: 1) Find an occurrence of the "styp" byte sequence in the segment, say at byte offset B1. 2) Verify against random emulation as follows: The next box type is compared to the list of expected box types: "styp", "sidx", "ssix", "prft", "moof", "mdat", "free", "mfra", "skip", "meta", "meco".

[0133] If one of the known box types is found, then byte offset B1-4 bytes is the byte offset of the resynchronization point.

[0134] b. If this is not one of the known box types mentioned above, then this occurrence of the styp box is considered an invalid sync point and is ignored. Resume at step 1 above.

[0135]

[0135] The techniques of this disclosure were tested on 30,282 segments from the scanned DASH-IF test assets. The scan revealed 28,408 occurrences of the "styp" column in the file, and only 10 of these 28,408 occurrences (approximately 1 in 2840 occurrences) were emulations that were discarded when it was determined that the next box was not one of the expected box types, i.e., "styp", "sidx", "ssix", "prft", "moof", "mdat", "free", "mfra", "skip", "meta", or "meco".

[0136] Based on these results, it seems that using styp resynchronization point detection together with the chunk structure is sufficient. It is appropriate to restrict it to only a subset of the boxes that can follow a styp, such as prft, emsg, free, skip, and moof.

[0137]

[0137] The remaining problem is the determination of the SAP type and the earliest presentation time. The latter is easily accomplished by use of the tfdt and other information in the movie fragment header. It is appropriate to document the algorithm.

[0138]

[0138] There are several options for determining the SAP type: Information-based detection in the moof. Simple techniques can be documented and implemented. · Use of compatible brands in SAP types. By already using CMAF, the following can be inferred:

[0139] ○cmff: Indicates that SAP is 1 or 2 cmfl: indicates SAP is 0 (is this correct for decryption?) cmfr: Indicates that SAP is 1, 2, or 3 This signaling may be sufficient if used consistently. Compatibility brands for other SAP types may be defined. Other techniques may be used to indicate the SAP type.

[0140]

[0139] To determine the SAP type, existing options can be used.

[0141]

[0140] Thus, the techniques of the present disclosure can be summarized as follows and can be performed by devices such as the content creation device 20, server device 60, and / or client device 40 of FIG. 1, as described above.

[0142]

[0141] In the DASH context, in some cases, a segment is treated as a single unit for downloading, accessing the media presentation, and also addressed by a URL. However, segments can be structured to allow resynchronization at the container level and random access to each representation even within a segment. The resynchronization mechanism is supported and signaled by the resynchronization element.

[0143]

[0142] The resynchronization element signals a resynchronization point in a segment. A resynchronization point is the start of a chunk (in a byte position), where a chunk is defined as a structured contiguous byte range within a segment that contains media data of a particular presentation duration and can be independently accessed on a container format including decryption possibilities. A resynchronization point in a segment can be defined as follows: A resynchronization point is the start of a chunk. Additionally, a resynchronization point is assigned the following properties:

[0144] o It has a byte offset or index value from the start of the segment that points to the first byte of the chunk.

[0145] o It has the earliest presentation time assigned in the representation.

[0146] o It has an assigned SAP type, for example defined by SAP types in ISO / IEC 14496-12.

[0147] o It has assigned a marker property that indicates whether a resynchronization point can be detected while parsing the segment through a particular marker, or whether a resynchronization point needs to be signaled by external means. Starting processing from a resynchronization point allows container parsing and decoding, if present, along with the information in the initialization segment. The capabilities of whether and how to access the contained elementary video streams are defined by the SAP type.

[0148]

[0143] Signaling each resynchronization point in the MPD can be difficult for causality reasons because resynchronization points can be added by the segment packager independent of the MPD update. For example, resynchronization points can be generated by the encoder and packager independent of the MPD. Also, at low latency, MPD signaling may not be available to a DASH client, for example, the DASH client 110 of FIG. 2 or the DASH client 292 of FIG. 7. Therefore, there are two ways to signal resynchronization points provided in segments in the MPD. Resync Index for each segment By providing a binary map of resync points in the segment. This is most easily used for segments that are fully available on the network. By signaling the presence of a resynchronization point in a segment and also some additional information that allows it to be easily found in terms of byte position and presentation time.

[0149]

[0144] To signal the above properties, the resync element has different attributes that are described in more detail in section 5.3.12.2 of the DASH specification.

[0150]

[0145] Random access refers to starting processing, decoding, and presenting a representation from a random access point onwards at time t by initialising the representation with an initialization segment, if present, and decoding and presenting the representation from the signalled segment onwards. A random access point may be signalled using a RandomAccess element as defined in Table 10 below.

[0151] [Table 2]

[0152]

[0146] Table 11 provides the various random access point types.

[0153] [Table 3]

[0154]

[0147] The resync index segment contains information related to a media segment. Similar to the segment index, the resync index segment provides the exact location of all resync points in the segment. Resync points are defined in section 5.3.12.1 of the DASH specification.

[0155]

[0148] An ISO BMFF resynchronization point may be defined as the start of an ISO BMFF segment with the following restrictions on both cardinality and ordering:

[0156] [Table 4]

[0157]

[0149] For an ISO BMFF-based resynchronization point, the properties may be defined as follows: The index is defined as the offset of the first byte of the above constrained ISO BMFF segment. The earliest presentation time Time is defined as the minimum of the combination of the decoding time of any sample in the chunk, the composition offset, and the edit list. · SAP types are defined according to section 4.5.2 of the DASH specification. If the styp is present with "cmfl" as the primary compatible brand then the marker is present.

[0158]

[0150] A resynchronization index segment may index one media segment of one representation and may be defined as follows: Each expression index segment shall begin with a "styp" box and the brand "risg" shall be present in the "styp" box. Conformance requirements for the brand "risg" are defined by this subclause. Each media segment is indexed by one or more segment index boxes, and the boxes for a given media segment are contiguous.

[0159]

[0151] Figure 9 is a flow chart illustrating an example method for retrieving media data in accordance with techniques of this disclosure. The method of Figure 9 is described with respect to client device 40 of Figure 1. However, a client device including low latency DASH client 232 of Figure 5 or media decoder 296, CMAF / FF parser 294, DASH client 292, and ROUTE receiver 290 of Figure 7 may also be configured to perform this method or a similar method.

[0160]

[0152] Initially, client device 40 may retrieve a manifest file, such as an MPD, for the media presentation (350). Client device 40 may retrieve the manifest file, for example, from server device 60. The manifest file may include data indicating that the media presentation includes resynchronization points at chunk boundaries within segments of a representation of the media presentation. Accordingly, client device 40 may determine resynchronization points for the media presentation, for example the closest available resynchronization point (352). Generally, a resynchronization point may indicate the start of a chunk boundary and is a randomly accessible point of the representation from which a file-level container (e.g., a data structure such as a box, as described above) can be parsed appropriately.

[0161]

[0153] In particular, the manifest file may indicate the location of the resynchronization point, such as a byte offset from the start of a segment. This information may not precisely identify the location of the resynchronization point in the segment, but may ensure that the resynchronization point is available within a byte range from the byte offset. Thus, client device 40 may form a request, such as an HTTP partial Get request, specifying the indicated byte offset to begin retrieval at the resynchronization point (354). Client device 40 may then send the request to server device 60 (356).

[0162]

[0154] In response to the request, the client device 40 may receive the requested media data including the resynchronization point (358). As described above, the byte offset may not precisely identify the location of the resynchronization point, and therefore the client device 40 may parse the data until it detects the actual location of the resynchronization point. The client device 40 may parse file level data structures, such as file format boxes, starting with the resynchronization point to determine the location of the media data of the corresponding chunk of the retrieved media data. In particular, the client device 40 may identify the resynchronization point as the start of a chunk, for example, by detecting a segment type value, a generator reference time value, an event message, a movie fragment, and a media data container box. The movie fragment may include encoded media data.

[0163]

[0155] De-encapsulation unit 50 may extract (360) the encoded media data of the corresponding chunks, for example, from the movie fragments, and provide the encoded media data, for example, to video decoder 48. The chunks may start at random access points (RAPs), such as intra-predicted frames (I-frames) of the video data. The manifest file may further indicate whether the RAP is the start of a closed group of pictures (GOP) or an open GOP, thereby indicating the type of random access that may be performed starting at the RAP (e.g., whether the leading picture of the I-frame is decodable or non-decodable). Video decoder 48 may then decode (362) the encoded media data and send the media data, for example, to video output 44, for presenting (364) the decoded media data.

[0164]

[0156] Thus, the method of Figure 9 represents one example of a method for retrieving media data, comprising retrieving a manifest file of a media presentation indicating that container parsing of the bitstream media data may begin at a resynchronization point of a segment of a representation of the media presentation, forming a request to retrieve media data of the representation starting at the resynchronization point using the manifest file, the resynchronization point being at a position other than the start of a segment and representing a point at which container parsing of the bitstream media data may begin, sending a request to initiate retrieval of the media data of the media presentation starting at the resynchronization point, and presenting the retrieved media data.

[0165]

[0157] Some techniques of this disclosure are summarized in the following examples.

[0166]

[0158] Example 1: A method for retrieving media data, the method comprising: retrieving a manifest file of a media presentation that indicates that resynchronization and decryption may begin at a resynchronization point of a representation of the media presentation; retrieving media data of the representation starting at the resynchronization point; and presenting the retrieved media data.

[0167]

[0159] Example 2: The method of example 1, wherein the resynchronization point comprises the start of a chunk boundary.

[0168]

[0160] Example 3: The method of Example 2, wherein the chunk boundary comprises the start of a chunk comprising zero or one segment type value, zero or one generator reference time value, zero or more event messages, at least one movie fragment box, and at least one media data container box.

[0169]

[0161] Example 4: The method of any of Examples 1 to 3, wherein the manifest file indicates the availability of resynchronization points in segments of the representation.

[0170]

[0162] Example 5: The method of example 4, wherein the resynchronization point is at a location other than the start of a segment.

[0171]

[0163] Example 6: The method of any of Examples 4 and 5, wherein the manifest file indicates the type of random access that may be performed at the resynchronization point.

[0172]

[0164] Example 7: The method of any of Examples 4-6, wherein the manifest file indicates locations and timing of resynchronization points and whether the location and timing information is accurate or estimated.

[0173]

[0165] Example 8: The method of any of Examples 1 to 7, wherein the manifest file comprises a media presentation description (MPD).

[0174]

[0166] Example 9: A device for retrieving media data, the device comprising one or more means for performing the method of any of Examples 1 to 8.

[0175]

[0167] Example 10: The device of Example 9, wherein the one or more means comprises one or more processors implemented in the circuit and a memory configured to store the media data.

[0176]

[0168] Example 11: The device of Example 9, comprising at least one of an integrated circuit, a microprocessor, or a wireless communication device.

[0177]

[0169] Example 12: A computer-readable storage medium storing instructions that, when executed, cause a processor to perform any of the methods of Examples 1 to 8.

[0178]

[0170] Example 13: A device for retrieving media data, comprising: means for retrieving a manifest file of a media presentation indicating that resynchronization and decryption may begin at a resynchronization point of a representation of the media presentation; means for retrieving media data of the representation starting at the resynchronization point; and means for presenting the retrieved media data.

[0179]

[0171] Example 14: A method for sending media data, comprising: sending a manifest file of a media presentation to a client device indicating that resynchronization and decryption may begin at a resynchronization point of a representation of the media presentation; receiving a request for media data starting at the resynchronization point from the client device; and in response to the request, sending the requested media data of the representation starting at the resynchronization point to the client device.

[0180]

[0172] Example 15: The method of Example 14, further comprising generating a manifest file.

[0181]

[0173] Example 16: The method of any of Examples 14 and 15, wherein the resynchronization point comprises the start of a chunk boundary.

[0182]

[0174] Example 17: The method of Example 16, wherein the chunk boundary comprises the start of a chunk comprising zero or one segment type value, zero or one generator reference time value, zero or more event messages, at least one movie fragment box, and at least one media data container box.

[0183]

[0175] Example 18: The method of any of Examples 14 to 17, wherein the manifest file indicates the availability of resynchronization points in segments of the representation.

[0184]

[0176] Example 19: The method of example 18, wherein the resynchronization point is at a location other than the start of the segment.

[0185]

[0177] Example 20: The method of any of Examples 18 and 19, wherein the manifest file indicates the type of random access that may be performed at the resynchronization point.

[0186]

[0178] Example 21: The method of any of Examples 18-20, wherein the manifest file indicates locations and timing of resynchronization points and whether the location and timing information is accurate or estimated.

[0187]

[0179] Example 22: Any of the methods of Examples 14 to 21, wherein the manifest file comprises a media presentation description (MPD).

[0188]

[0180] Example 23: A device for sending media data, the device comprising one or more means for performing the method of any of Examples 14 to 22.

[0189]

[0181] Example 24: The device of Example 23, wherein the one or more means comprises one or more processors implemented in the circuit and a memory configured to store the media data.

[0190]

[0182] Example 25: The device of Example 23 comprising at least one of an integrated circuit, a microprocessor, or a wireless communication device.

[0191]

[0183] Example 26: A computer-readable storage medium storing instructions that, when executed, cause a processor to perform any of the methods of Examples 1 to 8.

[0192]

[0184] Example 27: A device for sending media data, comprising: means for sending a manifest file of a media presentation to a client device indicating that resynchronization and decryption may begin at a resynchronization point of a representation of the media presentation; means for receiving a request for media data starting at the resynchronization point from the client device; and means for sending the requested media data of the representation starting at the resynchronization point to the client device in response to the request.

[0193]

[0185] In one or more examples, the described functions may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on or transmitted via a computer-readable medium as one or more instructions or code and executed by a hardware-based processing unit. A computer-readable medium may include a computer-readable storage medium, which corresponds to a tangible medium, such as a data storage medium, or may include a communication medium, which includes any medium that facilitates the transfer of a computer program from one place to another, for example, according to a communication protocol. In this manner, a computer-readable medium may generally correspond to (1) a tangible computer-readable storage medium that is non-transitory, or (2) a communication medium, such as a signal or carrier wave. A data storage medium may be any available medium that can be accessed by one or more computers or one or more processors to retrieve instructions, code and / or data structures for implementation of the techniques described in this disclosure. A computer program product may include a computer-readable medium.

[0194]

[0186] By way of example and not limitation, such computer-readable storage media may comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, flash memory, or any other medium that may be used to store desired program code in the form of instructions or data structures and that may be accessed by a computer. Furthermore, any connection is properly referred to as a computer-readable medium. For example, if instructions are transmitted from a website, server, or other remote source using coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included in the definition of the medium. However, it should be understood that computer-readable storage media and data storage media do not include connections, carrier waves, signals, or other transitory media, but instead cover non-transitory tangible storage media. As used herein, disk and disc include compact disc (CD), laser disc, optical disc, digital versatile disc (DVD), floppy disk, and Blu-ray disc, where disks typically reproduce data magnetically and discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer readable media.

[0195]

[0187] The instructions may be executed by one or more processors, such as one or more digital signal processors (DSPs), general-purpose microprocessors, application specific integrated circuits (ASICs), field programmable logic arrays (FPGAs), or other equivalent integrated circuits or discrete logic circuitry. Thus, the term "processor" as used herein may refer to any of the above structures, or any other structure suitable for implementing the techniques described herein. Furthermore, in some aspects, the functionality described herein may be provided in dedicated hardware and / or software modules configured for encoding and decoding, or incorporated into a composite codec. Also, the techniques may be fully implemented in one or more circuits or logic elements.

[0196]

[0188] The techniques of this disclosure may be implemented in a wide variety of devices or apparatuses, including wireless handsets, integrated circuits (ICs) or sets of ICs (e.g., chipsets). Although this disclosure has described various components, modules, or units to highlight functional aspects of devices configured to perform the disclosed techniques, the components, modules, or units do not necessarily need to be realized by different hardware units. Rather, as described above, the various units may be combined in a codec hardware unit or provided by a collection of interoperable hardware units, including one or more processors described above, along with suitable software and / or firmware.

[0197]

[0189] Various examples have been described. These and other examples are within the scope of the following claims. The invention as described in the claims of the original application is set forth below. [C1] A method for retrieving media data, comprising: retrieving a manifest file of a media presentation indicating that container parsing of media data of a bitstream may begin at a resynchronization point of a segment of a representation of a media presentation, the resynchronization point being at a position other than the start of the segment and representing a point at which the container parsing of the media data of the bitstream may begin; forming a request using the manifest file to retrieve the media data of the representation beginning at the resynchronization point; sending the request to initiate retrieval of the media data for the media presentation starting at the resynchronization point; presenting the retrieved media data; and A method comprising: [C2] The method of C1, wherein presenting the retrieved media data comprises parsing a file-level media data container of the retrieved media data at the resynchronization point. [C3] To analyze is to parsing the file level media data container until detecting a random access point (RAP) of the media presentation; sending said RAP to a media decoder; The method of C2, comprising: [C4] The method of C1, wherein the resynchronization point comprises the start of a chunk boundary. [C5] The method of C2, wherein the chunk boundary comprises a start of a chunk comprising zero or one segment type value, zero or one generator reference time value, zero or more event messages, at least one movie fragment box, and at least one media data container box. [C6] The method of C1, wherein the manifest file indicates the availability of the resynchronization points in the segments of the representation. [C7] The method of C6, wherein the resynchronization point is at a position other than the start of the segment. [C8] The method of C6, wherein the manifest file indicates a type of random access that may be performed at the resynchronization point. [C9] The method of C6, wherein the manifest file indicates locations and timings of the resynchronization points and whether the location and timing information is accurate or estimated. [C10] The method of C1, wherein the manifest file comprises a media presentation description (MPD). [C11] A device for retrieving media data, comprising: a memory configured to store media data of a media presentation; and retrieving a manifest file of the media presentation indicating that container parsing of a bitstream of media data may begin at a resynchronization point of a segment of a representation of the media presentation, the resynchronization point being at a position other than the start of the segment and representing a point at which the container parsing of the media data of the bitstream may begin. using the manifest file to form a request to retrieve the media data of the representation starting at the resynchronization point; sending the request to initiate retrieval of the media data for the media presentation starting at the resynchronization point; presenting the retrieved media data; and and one or more processors implemented in the circuit and configured to: A device comprising: [C12] The device of C11, wherein to present the retrieved media data, the one or more processors are configured to parse a file-level media data container of the retrieved media data at the resynchronization point. [C13] To parse the file level media data container, the one or more processors parsing the file level media data container until detecting a random access point (RAP) of the media presentation; sending said RAP to a media decoder; 20. The device of claim 12, configured to: [C14] The device of C11, wherein the resynchronization point comprises a start of a chunk boundary. [C15] The device of C14, wherein the chunk boundary comprises a start of a chunk comprising zero or one segment type values, zero or one generator reference time values, zero or more event messages, at least one movie fragment box, and at least one media data container box. [C16] The device of C11, wherein the manifest file indicates the availability of the resynchronization points in the segments of the representation. [C17] The device of C16, wherein the resynchronization point is at a position other than the start of the segment. [C18] The device of C16, wherein the manifest file indicates a type of random access that may be performed at the resynchronization point. [C19] The device of C16, wherein the manifest file indicates locations and timings of the resynchronization points and whether the location and timing information is accurate or estimated. [C20] The device described in C11, wherein the manifest file comprises a media presentation description (MPD). [C21] A computer-readable storage medium having stored thereon instructions that, when executed, cause a processor to: retrieving a manifest file of a media presentation indicating that container parsing of media data of a bitstream may begin at a resynchronization point of a segment of a representation of a media presentation, the resynchronization point being at a position other than the start of the segment and representing a point at which the container parsing of the media data of the bitstream may begin; using the manifest file to form a request to retrieve the media data of the representation starting at the resynchronization point; sending the request to initiate retrieval of the media data for the media presentation starting at the resynchronization point; presenting the retrieved media data; and A computer-readable storage medium for causing a computer to perform the above steps. [C22] The computer-readable storage medium of C21, wherein the resynchronization point comprises a start of a chunk boundary. [C23] The computer-readable storage medium of C22, wherein the chunk boundary comprises a start of a chunk comprising zero or one segment type value, zero or one generator reference time value, zero or more event messages, at least one movie fragment box, and at least one media data container box. [C24] The computer-readable storage medium of C21, wherein the manifest file indicates the availability of the resynchronization points in the segments of the representation. [C25] The computer-readable storage medium of C24, wherein the resynchronization point is at a location other than the start of the segment. [C26] The computer-readable storage medium of C24, wherein the manifest file indicates a type of random access that may be performed at the resynchronization point. [C27] The computer-readable storage medium of C24, wherein the manifest file indicates locations and timings of the resynchronization points and whether the location and timing information is accurate or estimated. [C28] The computer-readable storage medium of C21, wherein the manifest file comprises a media presentation description (MPD). [C29] A device for retrieving media data, comprising: means for retrieving a manifest file of a media presentation indicating that container parsing of media data of a bitstream may begin at a resynchronization point of a segment of a representation of a media presentation, the resynchronization point being at a position other than the start of the segment and representing a point at which the container parsing of the media data of the bitstream may begin; means for forming a request to retrieve the media data of the representation starting at the resynchronization point using the manifest file; means for sending the request to initiate retrieval of the media data of the media presentation starting at the resynchronization point; means for presenting the retrieved media data; A device comprising:

Claims

1. 1. A method for retrieving media data, comprising: retrieving a manifest file of the media presentation indicating a location of a resynchronization point within a segment of a representation of the media presentation, the manifest file further indicating that container parsing of media data of a bitstream may begin at the resynchronization point, the resynchronization point being at a location other than the start of the segment and representing a point at which the container parsing of the media data of the bitstream may begin, and a Random Access Point (RAP) following the resynchronization point. forming a request using the manifest file to retrieve the media data of the representation beginning at the resynchronization point; sending the request to initiate retrieval of the media data for the media presentation starting at the resynchronization point; parsing the retrieved media data beginning at the resynchronization point; Equipped with The method of claim 1, wherein the manifest file indicates the availability of the resynchronization points in the segments of the representation.

2. The method of claim 1 , wherein parsing the retrieved media data comprises parsing a file-level media data container of the retrieved media data at the resynchronization point.

3. To analyze, parsing the file level media data container until detecting the RAP of the media presentation; sending said RAP to a media decoder; The method of claim 2 comprising:

4. The method of claim 1 , wherein the resynchronization point comprises a start of a chunk boundary.

5. 5. The method of claim 4, wherein the chunk boundary comprises a start of a chunk comprising zero or one segment type value, zero or one generator reference time value, zero or more event messages, at least one movie fragment box, and at least one media data container box.

6. 1. A device for retrieving media data, comprising: a memory configured to store media data of a media presentation; retrieving a manifest file of the media presentation indicating a location of a resynchronization point within a segment of a representation of the media presentation, the manifest file further indicating that container parsing of media data of a bitstream may begin at the resynchronization point, the resynchronization point being at a location other than the start of the segment and representing a point at which the container parsing of the media data of the bitstream may begin, and a Random Access Point (RAP) following the resynchronization point. using the manifest file to form a request to retrieve the media data of the representation starting at the resynchronization point; sending the request to initiate retrieval of the media data for the media presentation starting at the resynchronization point; parsing the retrieved media data beginning at the resynchronization point; one or more processors implemented in the circuit and configured to Equipped with The manifest file indicates the availability of the resynchronization points in the segments of the representation.

7. to parse the retrieved media data, the one or more processors are configured to parse a file-level media data container of the retrieved media data at the resynchronization point; To parse the file level media data container, the one or more processors: parsing the file level media data container until detecting the RAP of the media presentation; sending said RAP to a media decoder; The device of claim 6 , configured to:

8. The device of claim 6 , wherein the resynchronization point comprises a start of a chunk boundary.

9. 10. The device of claim 8, wherein the chunk boundary comprises a start of a chunk comprising zero or one segment type value, zero or one generator reference time value, zero or more event messages, at least one movie fragment box, and at least one media data container box.

10. The method of claim 1 , wherein the resynchronization point is at a location other than the start of the segment.

11. The device of claim 6 , wherein the resynchronization point is at a location other than the start of the segment.

12. The method of claim 1 , wherein the manifest file indicates a type of random access that may be performed at the resynchronization point.

13. The device of claim 6 , wherein the manifest file indicates a type of random access that may be performed at the resynchronization point.

14. The method of claim 1 , wherein the manifest file indicates locations and timings of the resynchronization points and whether the location and timing information is accurate or estimated.

15. The device of claim 6 , wherein the manifest file indicates locations and timings of the resynchronization points and whether the location and timing information is precise or estimated.

16. The method of claim 1 , wherein the manifest file comprises a Media Presentation Description (MPD).

17. The device of claim 6 , wherein the manifest file comprises a Media Presentation Description (MPD).

18. A computer readable storage medium having instructions stored thereon which, when executed, cause a processor to perform a method according to any one of claims 1 to 5 and 10, 12, 14 and 16.

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