Dynamic Resolution Change Hints for Adaptive Streaming

Abstract

An example device for retrieving media data includes a memory configured to store video data; a video decoder configured to decode the video data; and one or more processors implemented in circuitry configured to: determine that the media presentation includes first video data at a first spatial resolution and second video data at a second spatial resolution, where the second spatial resolution is different from the first spatial resolution; receive a first portion of the first video data at the first spatial resolution for a first playback time; transmit the first portion of the first video data at the first spatial resolution to the video decoder; receive a second portion of the second video data at the second spatial resolution for a second playback time that is later than the first playback time; and transmit the second portion of the second video data at the second spatial resolution to the video decoder.

Description

[Technical field]

[0001] This application claims priority to U.S. Patent Application No. 17 / 647,435, filed on January 7, 2022, the entire contents of which are incorporated herein by reference.

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

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

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

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

[0006] In general, this disclosure describes techniques for streaming video data having various spatial resolutions. In particular, two or more representations may be included in a switching set, and the representations may include segments having different encoded spatial resolutions. For example, one representation may include video data encoded at 4K resolution (3840×2160), and another representation may include video data encoded at 1080p resolution (1920×1080). The client device may determine quality values ​​of the time-aligned segments of the various representations and retrieve the segments having higher quality values.

[0007] In one example, a method of retrieving video data includes determining that a media presentation includes first video data at a first spatial resolution and second video data at a second spatial resolution, where the second spatial resolution is different from the first spatial resolution; receiving a first portion of the first video data at the first spatial resolution for a first playback time; transmitting the first portion of the first video data at the first spatial resolution to a video decoder; receiving a second portion of the second video data at a second spatial resolution for a second playback time that is later than the first playback time; and transmitting the second portion of the second video data at the second spatial resolution to the video decoder.

[0008] In another example, a device for retrieving video data includes a memory configured to store the video data; a video decoder configured to decode the video data; and one or more processors implemented in circuitry configured to determine that a media presentation includes first video data at a first spatial resolution and second video data at a second spatial resolution, where the second spatial resolution is different from the first spatial resolution; receive a first portion of the first video data at the first spatial resolution for a first playback time and transmit the first portion of the first video data at the first spatial resolution to the video decoder; receive a second portion of the second video data at the second spatial resolution for a second playback time that is later than the first playback time and transmit the second portion of the second video data at the second spatial resolution to the video decoder.

[0009] In another example, a computer-readable storage medium includes one or more processors having instructions stored therein that, when executed, are configured to cause the processor to determine that the media presentation includes first video data at a first spatial resolution and second video data at a second spatial resolution, the second spatial resolution being different from the first spatial resolution, receive a first portion of the first video data at the first spatial resolution for a first playback time and transmit the first portion of the first video data at the first spatial resolution to a video decoder, receive a second portion of the second video data at the second spatial resolution for a second playback time that is later than the first playback time, and transmit the second portion of the second video data at the second spatial resolution to the video decoder.

[0010] In another example, a device for retrieving video data includes means for determining that the media presentation includes first video data at a first spatial resolution and second video data at a second spatial resolution, where the second spatial resolution is different from the first spatial resolution; means for receiving a first portion of the first video data at the first spatial resolution for a first playback time; means for transmitting the first portion of the first video data at the first spatial resolution to a video decoder; means for receiving a second portion of the second video data at a second spatial resolution for a second playback time that is later than the first playback time; and means for transmitting the second portion of the second video data at the second spatial resolution to the video decoder.

[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 be apparent from the description and drawings, and from the claims. [Brief description of the drawings]

[0012] [Figure 1] 1 is a block diagram illustrating an example system that implements techniques for streaming media data over a network. [Diagram 2] 2 is a block diagram illustrating an exemplary set of components of the removal unit of FIG. 1 in greater detail. [Diagram 3] FIG. 2 is a conceptual diagram illustrating exemplary multimedia content elements. [Figure 4] FIG. 2 is a block diagram illustrating elements of an exemplary video file. [Diagram 5] 1 is a conceptual diagram illustrating an example of a retrieval technique according to the techniques of this disclosure. [Figure 6] 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] Generally, this disclosure describes techniques for dynamically switching between video resolutions when streaming video data. Streaming video data may be performed via a unicast protocol, a broadcast protocol, or a multicast protocol. For example, HyperText Transfer Protocol (HTTP) may be used to stream video data according to, for example, Dynamic Adaptive Streaming over HTTP (DASH), HTTP Live Streaming (HLS), or other such protocols. As another example, a broadcast or multicast protocol such as enhanced Multimedia Broadcast Multicast Service (eMBMS), File Delivery over Unidirectional Transport (FLUTE), Real-time Object-delivery over Unidirectional Transport (ROUTE), Real-time Transport Protocol (RTP), Real-time Streaming Protocol (RTSP), etc. may be used to deliver the video data. Broadcasting may also be performed over-the-air (OTA), for example, via radio waves. In some examples, the broadcast or multicast protocol may deliver DASH or HLS format video data such that a middleware unit of a client device may act as a client for the broadcast or multicast session and as a proxy client to the DASH or HLS client.

[0014] Digital Video Broadcasting (DVB) is a group of standards for digital television. DVB standards are currently being developed for the next generation of video codecs. Document CM-AVC0620 for DVB provides "Draft commercial requirements for next generation video codecs". The main objective of the work item addresses the addition of new codecs beyond the existing codecs in TS 101 154 (MPEG-2 Video, H.264 / AVC, VC-1, H.265 / HEVC), but the commercial requirements also address new formats and new ways of encoding and consuming these formats.

[0015] The draft TS 101 154 mentions the possibility of dynamic resolution change only in the case of reference picture resampling using the ITU-T H.266 / Versatile Video Coding (VVC) coding standard. The use of dynamic resolution for content coding has been used with existing codecs and deployed by some streaming services for video-on-demand (VOD) streaming services. This disclosure recognizes that dynamic resolution of video data may also be deployed for live streaming or broadcast services.

[0016] This disclosure describes techniques for dynamic resolution change that can be used for new encoding schemes. These techniques also enable seamless resolution upscaling of decoded pictures at the MPEG-2 system layer of an integrated receiver decoder (IRD) or in the rendering engine of a display (e.g., a television). Resolution may change dynamically at sequence parameter set (SPS) boundaries, even without reference picture resampling, or within a sequence when reference picture resampling is used in VVC. These techniques may be adopted in future codecs other than VVC as well. This disclosure further describes some constraints that may be applied to limit resolution changes in some contexts.

[0017] In video streaming applications, over-the-top (OTT) players can support dynamic and seamless resolution changes at segment boundaries; that is, in adaptive bitrate (ABR) encoding and streaming schemes, a switch in bitrate profile from one segment to the next may also be accompanied by a change in the encoded resolution. Even within a bitrate profile, evolved video-on-demand (VOD) streaming services can dynamically change the resolution on a scene-by-scene basis to improve compression efficiency and save bandwidth.

[0018] Dynamic resolution coding tests have been performed for a variety of standards and resolutions. For example, heuristic tests have been performed for the ITU-T H.264 / Advanced Video Coding (AVC) HD and ITU-T H.265 / High Efficiency Video Coding (HEVC) UHD use cases. For H.264 / AVC HD, the resolutions tested included 1920×1080p, 1280×720p, and 960×540p. For H.265 / HEVC UHD, the resolutions tested included 3840×2160, 250×1440, and 1920×1080. These tests showed bitrate savings of 20-25% by using lower resolutions for the most temporally complex scenes, but such bitrate reductions are imperceptible, allowing the benefits of the highest resolution to be maintained when needed.

[0019] For live broadcast applications to compete with streaming of pre-recorded content, it may be important to take advantage of dynamic resolution encoding adaptation for live broadcast video content. Although the video decoder itself supports decoding of dynamic resolution encoded video data, the picture in the video decoder buffer may remain at the encoded resolution, and automatic upscaling to the nominal resolution may be the responsibility of the IRD or the display at the MPEG-2 system layer.

[0020] 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.

[0021] In HTTP streaming, frequently used operations include HEAD, GET, and partial GET. The HEAD operation retrieves the header of a file associated with a given Uniform Resource Locator (URL) or Uniform Resource Name (URN) without retrieving the payload associated with the URL or URN. The GET operation retrieves the entire file associated with a given URL or URN. The partial GET operation receives a byte range as an input parameter and retrieves a consecutive number of bytes of a file, where the number of bytes corresponds to the byte range received. Thus, movie fragments may be provided for HTTP streaming, since the partial GET operation can retrieve one or more individual movie fragments. In a movie fragment, there may be several track fragments of different tracks. In HTTP streaming, a media presentation may be a structured collection of data accessible to a client. A client can request and download media data information to present a streaming service to a user.

[0022] In an example of streaming 3GPP data using HTTP streaming, multiple representations may exist for video and / or audio data of the multimedia content. As described below, the different representations may correspond to different coding characteristics (e.g., different profiles or levels of a video coding standard), different coding standards or extensions of a coding standard (such as multiview and / or scalable extensions), or different bitrates. A manifestation of such representations may be defined in a Media Presentation Description (MPD) data structure. A media presentation may correspond to a structured collection of data accessible to an HTTP streaming client device. An HTTP streaming client device can request and download media data information to present a streaming service to a user of the client device. A media presentation may be described in an MPD data structure, which may include updates to the MPD.

[0023] A media presentation may include a sequence of one or more periods. Each period may extend until the start of the next period or, in the case of the last period, until the end of the media presentation. Each period may include one or more representations for the same media content. A representation may be one of several alternatively encoded versions of audio, video, timed text, or other such data. The representations may differ by type of encoding, e.g., bit rate, resolution, and / or codec for video data and bit rate, language, and / or codec for audio data. The term representation may be used to refer to a section of encoded audio data or encoded video data that corresponds to a particular period of multimedia content and that has been encoded in a particular way.

[0024] Representations for a particular time period may be assigned to a group indicated by an attribute in the MPD indicating the adaptation set to which the representation belongs. Representations in the same adaptation set are generally considered as alternatives to each other in that a client device may dynamically and seamlessly switch between these representations, for example to perform bandwidth adaptation. For example, each representation of video data for a particular time period may be assigned to the same adaptation set, so that any of the representations may be selected for decoding to present media data, such as video data or audio data, of the multimedia content for the corresponding time period. In some examples, the media content in a time period may be represented by either one representation from group 0, if group 0 is present, or a combination of at most one representation from each non-zero group. Timing data for each representation for a time period may be represented relative to a start time of the time period.

[0025] A representation may contain one or more segments. Each representation may contain an initialization segment, or each segment of a representation may be self-initializing. The initialization segment, when present, may contain initialization information for accessing the representation. In general, the initialization segment does not contain media data. A segment may be uniquely referenced by an identifier, such as a Uniform Resource Locator (URL), Uniform Resource Name (URN), or Uniform Resource Identifier (URI). The MPD may provide 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.

[0026] Different representations may be selected for substantially simultaneous retrieval for different types of media data. For example, a client device may select an audio representation, a video representation, and a timed text representation from which to retrieve segments. In some examples, a client device may select specific adaptation sets to perform 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 a representation for another type of media (e.g., audio and / or timed text).

[0027] 1 is a block diagram illustrating an example system 10 that implements techniques for streaming media data over a network. In this example, system 10 includes a content preparation device 20, a server device 60, and a client device 40. Client device 40 and server device 60 are communicatively coupled by a network 74, which may include the Internet. In some examples, content preparation device 20 and server device 60 may also be coupled by network 74 or another network, or may be communicatively coupled directly. In some examples, content preparation device 20 and server device 60 may include the same device.

[0028] In the example of FIG. 1 , content preparation device 20 comprises audio source 22 and video source 24. Audio source 22 may include, for example, a microphone that generates electrical signals representative of captured audio data to be encoded by audio encoder 26. Alternatively, audio source 22 may comprise a storage medium that stores previously recorded audio data, an audio data generator such as a computerized synthesizer, or any other source of audio data. Video source 24 may comprise a video camera that generates video data to be encoded by video encoder 28, a storage medium encoded with previously recorded video data, a video data generation unit such as a computer graphics source, or any other source of video data. Content preparation device 20 is not necessarily communicatively coupled to server device 60 in all examples, although it may store multimedia content on a separate medium that is read by server device 60.

[0029] The raw audio and video data may include analog or digital data. Analog data may be digitized before being encoded by audio encoder 26 and / or video encoder 28. Audio source 22 may obtain audio data from a speaking participant while that participant is speaking, and video source 24 may simultaneously obtain video data of the speaking participant. In other examples, audio source 22 may comprise a computer-readable storage medium that includes stored audio data, and video source 24 may comprise a computer-readable storage medium that includes stored video data. Thus, the techniques described in this disclosure may be applied to live, streaming, real-time audio and real-time video data, or may be applied to archived, pre-recorded audio and video data.

[0030] An audio frame corresponding to a video frame is generally an audio frame that includes audio data captured (or generated) by audio source 22 contemporaneously with video data captured (or generated) by video source 24 that is included in the video frame. For example, audio source 22 captures audio data while a speaking participant is generally generating audio data by speaking, and video source 24 captures video data of the speaking participant contemporaneously, i.e., while audio source 22 is capturing audio data. Thus, an audio frame may correspond in time to one or more particular video frames. Thus, an audio frame corresponding to a video frame generally corresponds to a situation in which audio data and video data were captured contemporaneously, for which the audio frame and video frame, respectively, include contemporaneously captured audio data and video data.

[0031] In some examples, audio encoder 26 may encode a timestamp in each encoded audio frame representing 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 representing the time that the video data for the encoded video frame was recorded. In such examples, audio frames corresponding to a video frame may include an audio frame that includes a timestamp and a video frame that includes the same timestamp. Content preparation device 20 may include internal clocks from which audio encoder 26 and / or video encoder 28 may generate timestamps, or which audio source 22 and video source 24 may use to associate audio data and video data, respectively, with timestamps.

[0032] In some examples, audio source 22 may send data to audio encoder 26 corresponding to the time the audio data was recorded, and video source 24 may send data to video encoder 28 corresponding to the time the video data was recorded. In some examples, audio encoder 26 may encode a sequence identifier in the encoded audio data to indicate the relative time order of the encoded audio data, although not necessarily indicating the absolute time the audio data was recorded, and similarly, video encoder 28 may also use the sequence identifier to indicate the relative time order of the encoded video data. Similarly, in some examples, the sequence identifier may be mapped with or correlated to a timestamp.

[0033] The audio encoder 26 generally produces a stream of encoded audio data, while the video encoder 28 produces a stream of encoded video data. Each individual stream of data (whether audio or video) may be referred to as an elementary stream. An elementary stream is a single digitally encoded (possibly compressed) component of a representation. For example, the encoded video or audio portion of a representation may be an elementary stream. An elementary stream may be converted into a Packetized Elementary Stream (PES) before being encapsulated within a video file. Within the same representation, a stream ID may be used to distinguish PES packets belonging to one elementary stream from PES packets belonging to other elementary streams. The basic unit of data of an elementary stream is the Packetized Elementary Stream (PES) packet. Thus, encoded video data generally corresponds to an elementary video stream. Similarly, audio data corresponds to one or more respective elementary streams.

[0034] 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 certain profile or level. Video coding standards typically do not prescribe an encoder, but an encoder is tasked with ensuring that the generated bitstream conforms to the standard for a decoder. In the context of a video coding standard, a "profile" corresponds to a subset of algorithms, features, or tools, and the constraints that apply to them. As defined by the H.264 standard, for example, a "profile" is a subset of the entire bitstream syntax specified by the H.264 standard. A "level" corresponds to a constraint on the decoder's resource consumption, such as, for example, decoder memory and computation, which is related to picture resolution, bitrate, and block processing speed. A profile may be signaled by a profile_idc (profile indicator) value, while a level may be signaled by a level_idc (level indicator) value.

[0035] For example, the H.264 standard acknowledges that within the range imposed by the syntax of a given profile, it is still possible to expect large variations in the performance of encoders and decoders depending on the values ​​that syntax elements in the bitstream take, such as the specified size of the decoded picture. The H.264 standard further acknowledges that in many applications, it is neither practical nor economical to implement a decoder capable of handling all hypothetical uses of the syntax in a particular profile. Therefore, the H.264 standard defines a "level" as a specified set of constraints imposed on the values ​​of syntax elements in the bitstream. These constraints may be simple limits on the values. Alternatively, these constraints may take the form of constraints on arithmetic combinations of values ​​(e.g., the product of the number of pictures decoded per second, the picture height, and the picture width). The H.264 standard further specifies that individual implementations may support different levels for each supported profile.

[0036] A decoder conforming to a profile usually supports all features defined in the profile. For example, as a coding feature, B-picture coding is not supported in the baseline profile of H.264 / AVC, but is supported in other profiles of H.264 / AVC. A decoder conforming to a level should be able to decode any bitstream that does not require resources beyond the limit defined in the level. Profile and level definitions may be useful for explainability. For example, during video transmission, a pair of profile and level definitions may be negotiated and agreed upon for the entire transmission session. More specifically, in H.264 / AVC, a level may define the number of macroblocks that need to be processed, the size of the Decoded Picture Buffer (DPB), the size of the Coded Picture Buffer (CPB), the range of motion vectors in the vertical direction, the limit on the maximum number of motion vectors per two consecutive MBs, and whether B blocks may have sub-macroblock partitions smaller than 8×8 pixels. In this way, the decoder can determine whether it can properly decode a bitstream.

[0037] In the example of Figure 1, encapsulation unit 30 of content preparation device 20 receives an elementary stream including coded video data from video encoder 28 and an elementary stream including coded audio data from audio encoder 26. In some examples, video encoder 28 and audio encoder 26 may each include a packetizer for forming PES packets from the coded data. In other examples, video encoder 28 and audio encoder 26 may each interface with a respective packetizer for forming PES packets from the coded data. In yet other examples, encapsulation unit 30 may include packetizers for forming PES packets from the coded audio data and the coded video data.

[0038] The video encoder 28 may encode the video data of the multimedia content in various ways to generate various representations of the multimedia content at various bit rates with various characteristics, such as pixel resolution, frame rate, compliance with various encoding standards, compliance with various profiles and / or levels of profiles for various encoding standards, representations having one or more views (e.g., for two-dimensional or three-dimensional playback), or other such characteristics. A representation as used in this disclosure may include one of audio data, video data, text data (e.g., for closed captioning), or other such data. The representation may include an elementary stream, such as an audio elementary stream or a video elementary stream. Each PES packet may include a stream_id that identifies the elementary stream to which the PES packet belongs. The encapsulation unit 30 is responsible for assembling the elementary streams into video files (e.g., segments) of the various representations.

[0039] Encapsulation unit 30 receives PES packets for the elementary streams of the representation from audio encoder 26 and video encoder 28 and forms corresponding network abstraction layer (NAL) units from the PES packets. Coded video segments may be organized into NAL units, which enable addressing applications of the video representation such as video telephony, storage, broadcast, or streaming. NAL units can 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 at one time instance may be contained within an access unit, which is typically presented as a primary coded picture and may include one or more NAL units.

[0040] Non-VCL NAL units may include, among others, parameter set NAL units and SEI NAL units. Parameter sets may contain sequence level header information (in sequence parameter sets (SPS)) and picture level header information that does not change frequently (in picture parameter sets (PPS)). With parameter sets (e.g., PPS and SPS), 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, eliminating the need for redundant transmission for error recovery. In an example of out-of-band transmission, parameter set NAL units may be transmitted on a different channel than other NAL units, such as SEI NAL units.

[0041] Supplemental Enhancement Information (SEI) may include information that is not necessary for decoding coded picture samples from VCL NAL units, but may assist processes related to decoding, display, error recovery, and other purposes. SEI messages may be included in non-VCL NAL units. SEI messages are normative parts of some standard specifications and therefore are not always mandatory in the implementation of a decoder that conforms to the standard. The SEI messages may be sequence level SEI messages or picture level SEI messages. Some sequence level information may be included in SEI messages, such as the Scalability Information SEI message in the example of SVC and the View Scalability Information SEI message in MVC. These exemplary SEI messages may convey information, for example, regarding extraction of operation points and characteristics of the operation points. In addition, the encapsulation unit 30 may form a manifest file, such as a Media Presentation Description (MPD) that describes characteristics of the representation. The encapsulation unit 30 may format the MPD according to the Extensible Markup Language (XML).

[0042] 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 include an interface for writing to a storage medium, such as a network interface or a universal serial bus (USB) interface, a CD or DVD writer or burner, an interface to a magnetic storage medium or a 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 an individual manifest file 66 and one or more representations 68A-68N (representations 68). In some examples, the output interface 32 may also send the data directly to a network 74.

[0043] In some examples, representations 68 may be divided 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, for example, by speaker, language or other characteristics of the text to be decoded and presented along with the representation and / or audio data, camera angle information that may represent the camera angle or field of view of a real-world camera of the scene of the representation in the adaptation set, rating information that represents the suitability of the content for a particular viewer, etc.

[0044] The manifest file 66 may include data indicating a subset of representations 68 that correspond to a particular adaptation set, as well as common characteristics of the adaptation set. The manifest file 66 may also include data representing individual characteristics, such as bitrate, for each representation in the adaptation set. In this manner, the adaptation set may enable simplified network bandwidth adaptation. The representations in an adaptation set may be indicated using child elements of the adaptation set element in the manifest file 66.

[0045] 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.

[0046] The request processing unit 70 is configured to receive network requests for data on the storage medium 62 from a client device, such as the client device 40. For example, the request processing unit 70 may implement the Hypertext Transfer Protocol (HTTP) version 1.1, as described in RFC 2616, "Hypertext Transfer Protocol-HTTP / 1.1," by R. Fielding et al., Network Working Group, IETF, June 1999. That is, the request processing unit 70 may be configured to receive HTTP GET or partial GET requests and provide data for the multimedia content 64 in response to those requests. The request may specify a segment of one of the representations 68, for example, using the URL of the segment. In some examples, the request may also specify one or more byte ranges of the segment, thus comprising a partial GET request. The request processing unit 70 may further be configured to respond to an HTTP HEAD request to provide header data for a segment of one of the representations 68. In either case, the request processing unit 70 may be configured to process the request to provide the requested data to a requesting device, such as the client device 40.

[0047] Additionally or alternatively, the request processing unit 70 may be configured to deliver the media data via a broadcast or multicast protocol, such as eMBMS. Content preparation device 20 may create DASH segments and / or subsegments in substantially the same manner as described, but server device 60 may deliver these segments or subsegments using eMBMS or another broadcast or multicast network transport protocol. For example, the request processing unit 70 may be configured to receive a multicast group join request from client device 40. That is, server device 60 may advertise 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 client device 40. Client device 40 may then submit a request to join the multicast group. The request may be propagated throughout network 74, for example to routers constituting network 74, such that the routers direct traffic destined for the IP address associated with the multicast group to subscribing client devices, such as client device 40.

[0048] 1, multimedia content 64 includes a manifest file 66, which may correspond to a media presentation description (MPD). The manifest file 66 may contain descriptions of various alternative representations 68 (e.g., video services of different qualities), which may include, for example, codec information, profile values, level values, bit rates, and other descriptive characteristics of the representations 68. Client device 40 may retrieve the MPD of a media presentation to determine how to access segments of the representations 68.

[0049] In particular, the retrieval unit 52 can 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 can also include any or all of a language preference selected by the user of the client device 40, one or more camera fields of view 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 can comprise, for example, a web browser or a media client configured to submit HTTP GET and partial GET requests. The retrieval unit 52 can 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 can be implemented in hardware or a combination of hardware, software, and / or firmware, in which case the requisite hardware can be provided to execute instructions for the software or firmware.

[0050] The retrieval unit 52 may compare the decoding and rendering capabilities of the client device 40 to the characteristics of the representations 68 indicated by the information in the manifest file 66. The retrieval unit 52 may first retrieve at least a portion of the manifest file 66 to determine the characteristics of the representations 68. For example, the retrieval unit 52 may request a portion of the manifest file 66 that describes the characteristics of one or more adaptation sets. The retrieval unit 52 may select a subset of the representations 68 (e.g., an adaptation set) that has characteristics that can be satisfied by the coding and rendering capabilities of the client device 40. The retrieval unit 52 may then determine bitrates for the representations in the adaptation set, determine a currently available amount of network bandwidth, and retrieve a segment from one of the representations that has a bitrate that can be satisfied by the network bandwidth.

[0051] Generally, a higher bit rate representation provides higher quality video playback, while a lower bit rate representation may provide sufficient quality video playback when available network bandwidth is reduced. Thus, when available network bandwidth is relatively high, retrieval unit 52 may retrieve data from a representation with a relatively high bit rate, and when available network bandwidth is low, retrieval unit 52 may retrieve data from a representation with a relatively low bit rate. In this manner, client device 40 may stream multimedia data over network 74 while also adapting to changing network bandwidth availability of network 74.

[0052] Additionally or alternatively, retrieval unit 52 may be configured to receive data according to a broadcast or multicast network protocol, such as eMBMS or IP multicast. In such an example, retrieval unit 52 may submit a request to join a multicast network group associated with a particular media content. After joining the multicast group, retrieval unit 52 may receive the data of the multicast group without issuing a further request to server device 60 or content preparation device 20. Retrieval unit 52 may submit a request to exit the multicast group when the data of the multicast group is no longer needed, for example, to stop playback or to change the channel to a different multicast group.

[0053] The network interface 54 may receive and provide data for segments of the selected representation to a retrieval unit 52, which may then provide the segments to a de-encapsulation unit 50. The 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 pass the encoded data to either an audio decoder 46 or a video decoder 48, depending on whether the encoded data is part of an audio or video stream, e.g., as indicated by the PES packet headers of the streams. The audio decoder 46 decodes the encoded audio data and passes the decoded audio data to the audio output 42, while the video decoder 48 decodes the encoded video data and passes the decoded video data, which may include multiple views of the stream, to the video output 44.

[0054] Each of the video encoder 28, video decoder 48, audio encoder 26, audio decoder 46, encapsulation unit 30, extraction unit 52, and decapsulation unit 50, where applicable, may be implemented as any of a variety of suitable processing circuitry, such as one or more microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), discrete logic circuitry, software, hardware, firmware, or any combination thereof. Each of the video encoder 28 and 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 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 extraction unit 52, and / or the decapsulation unit 50 may include an integrated circuit, a microprocessor, and / or a wireless communication device such as a cellular telephone.

[0055] Client device 40, server device 60, and / or content preparation device 20 may be configured to operate in accordance with the techniques of this disclosure. By way of example, this disclosure describes these techniques with respect to client device 40 and server device 60. However, it should be understood that content preparation device 20 may be configured to implement these techniques in place of (or in addition to) server device 60.

[0056] Encapsulation unit 30 may form NAL units that include a header that identifies the program to which the NAL unit belongs and a payload, e.g., audio data, video data, or data that describes the transport or program stream to which the NAL unit corresponds. For example, in H.264 / AVC, a NAL unit includes a one-byte header and a variable-sized payload. A NAL unit that includes video data within its payload may include various levels of granularity of the video data. For example, a NAL unit may include a block of video data, multiple blocks, a slice of video data, or an entire picture of video data. Encapsulation unit 30 may receive encoded video data from video encoder 28 in the form of PES packets of elementary streams. Encapsulation unit 30 may associate each elementary stream with a corresponding program.

[0057] 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 for one output time instance, e.g., all audio data and video data for one time instance. For example, if each view has a frame rate of 20 frames per second (fps), each time instance may correspond to a time interval of 0.05 seconds. During this time interval, a particular frame for all views of the same access unit (same time instance) may be rendered simultaneously. In one example, an access unit may include a coded picture in one time instance, which may be presented as a coded primary picture.

[0058] Thus, an access unit may include all audio and video frames of a common time instance, e.g., all views corresponding to time X. This disclosure also refers to the coded pictures of a particular view as a "view component." That is, a view component may include coded pictures (or frames) for a particular view at a particular time. Thus, an access unit may be defined as including all view components of a common time instance. The decoding order of the access units is not necessarily the same as the output or display order.

[0059] 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), and the description may include, for example, codec information, profile values, and level values. An MPD is an example of a manifest file, such as manifest file 66. Client device 40 may retrieve the MPD of a media presentation to determine how to access movie fragments of the various presentations. The movie fragments may be placed in a movie fragment box (moof box) of a video file.

[0060] Manifest file 66 (which may include, for example, an MPD) may advertise the availability of segments of representations 68. That is, the MPD may include information indicating the wall-clock time at which a first segment of one of representations 68 becomes available, as well as information indicating the duration of the segment within representation 68. In this manner, retrieval unit 52 of client device 40 can determine when each segment is available based on the start time as well as the duration of the segment preceding a particular segment.

[0061] After the encapsulation unit 30 assembles the NAL units and / or access units into a video file based on the received data, the encapsulation unit 30 passes the video file to the output interface 32 for output. In some examples, instead of sending the video file directly to the client device 40, the encapsulation unit 30 can store the video file locally or send the video file to a remote server via the output interface 32. The output interface 32 may include, for example, a transmitter, a transceiver, a device for writing data to a computer-readable medium, such as an optical drive, a magnetic media drive (e.g., a floppy drive), a universal serial bus (USB) port, a network interface, or other output interface. The output interface 32 outputs the video file to a computer-readable medium, such as, for example, a transmission signal, a magnetic medium, an optical medium, a memory, a flash drive, or other computer-readable medium.

[0062] Network interface 54 may receive NAL units or access units over network 74 and provide the NAL units or access units to decapsulation unit 50 via retrieval unit 52. Decapsulation unit 50 may decapsulate elements of the video file into constituent PES streams, depacketize the PES streams to retrieve the encoded data, and send the encoded data to either audio decoder 46 or video decoder 48, depending on whether the encoded data is part of an audio stream or a video stream, as indicated, for example, by the stream's PES packet headers. Audio decoder 46 decodes the encoded audio data and sends the decoded audio data to audio output 42, while video decoder 48 decodes the encoded video data and sends the decoded video data, which may include multiple views of the stream, to video output 44.

[0063] According to the techniques of this disclosure, content preparation device 20 may prepare a media presentation including multiple representations in a switching set having different spatial resolutions. For example, representation 68A may have a resolution of 3840×2160, and representation 68N may have a resolution of 1920×1080. Content preparation device 20 may further construct an Addressable Resource Index (ARI) track for the switching set that advertises a quality value for a segment (or chunk of a segment) of representation 68 (e.g., using a quality_identifier value in the ARI track). ISO / IEC 23009-1:2021 / Amd.1 includes one example definition of an ARI track that includes a quality_identifier. Because the bitrates of the two resolutions may be substantially similar or identical (i.e., the same), the quality value may generally represent a metric of quality other than spatial resolution and bitrate.

[0064] Allowing a higher bit rate for lower resolution video data may, in some cases, result in higher quality for the lower resolution video data than for higher resolution video data. For example, for a highly dynamic scene with many changes in global camera field of view, video data encoded at a lower resolution at a given bit rate may have higher quality than video data encoded at a higher resolution at the same bit rate. That is, when many global camera field of view changes occur for a video sequence, more intra-predictively coded frames (I-frames) may be required, which may consume a relatively large amount of the bit budget allocated to the scene. A larger number of bits are required to code the higher resolution I-frames. Thus, for the same bit budget, more bits are available to code subsequent inter-predictively coded frames (e.g., P-frames and B-frames) for the lower resolution video than for the higher resolution video. Thus, assuming the same bit rate is used, a higher overall quality may be expected for such a scene in the lower resolution than in the higher resolution.

[0065] Thus, retrieval unit 52 of client device 40 may obtain quality values ​​for two segments or chunks corresponding to the same playback time from two different representations. Retrieval unit 52 may also determine whether the quality value for the segment or chunk of the lower resolution representation is higher than the quality value for the segment or chunk of the higher resolution representation. If the segment or chunk of the lower resolution representation has a higher quality value, retrieval unit 52 may retrieve the segment or chunk of the lower resolution representation and provide the segment or chunk to video decoder 48. On the other hand, if the segment or chunk of the higher resolution representation has a higher quality value, retrieval unit 52 may retrieve the segment or chunk of the lower resolution representation and provide the segment or chunk to video decoder 48. Retrieval unit 52 may similarly analyze the quality value of each segment or chunk throughout playback of the media presentation and thus may switch between the low and high resolution representations at various times.

[0066] In other words, in some scenarios, such as H.266 / VVC encoded video data, the advantages of dynamic resolution encoding have been demonstrated by video-on-demand (VOD) services. This disclosure recognizes that these advantages may be realized using broadcast distribution. That is, according to the techniques of this disclosure, a client device 40 may receive a media stream via broadcast and perform a resolution change between two different resolutions of the video data contained in the media stream, for example, between representations including different spatial resolutions for the encoded video data. For DVB DASH applications, such a resolution change may be supported within a profile at a segment boundary.

[0067] This disclosure further recognizes that dynamic resolution change need not be limited to the use of reference picture resampling in a VVC encoded stream. Likewise, the change need not be limited to between two encoded resolutions. In some examples, more than two resolutions may be supported. For example, a VVC HDR UHDTV-1 IRD may be configured to switch between any of the following resolutions: 3840×2160, 2560×1440, 1920×1080, 1280×720. As another example, a VVC HDR UHDTV-2 IRD may be configured to switch between any of the following resolutions: 7680×4320, 5120×2880, 3840×2160, 2560×1440, 1920×1080, 1280×720.

[0068] This disclosure also recognizes that resolution changes may occur relatively frequently. For example, if the picture resolution (e.g., as indicated by the values ​​of syntax elements sps_pic_width_in_luma_samples and sps_pic_height_in_luma_samples of a picture parameter set (PPS)) is changed at each DVB random access point (RAP), two consecutive changes of picture resolution may occur much more frequently than two seconds worth of play time. The techniques of this disclosure may also assume a video decoder that can correctly handle resolution changes for input encoded video data, but also upsample lower resolution video data to a predetermined maximum resolution for display (e.g., a resolution that matches the display to which the video data is output). In this way, the displayed video data will have the same resolution even if the resolution of the input encoded video data changes, thereby preventing a user from observing the resolution change.

[0069] In this manner, client device 40 represents one example of a device for retrieving media data, the device including a memory configured to store video data; a video decoder configured to decode the video data; and one or more processors implemented in circuitry configured to: determine that the media presentation includes first video data at a first spatial resolution and second video data at a second spatial resolution, where the second spatial resolution differs from the first spatial resolution; receive a first portion of the first video data at the first spatial resolution for a first playback time; transmit the first portion of the first video data at the first spatial resolution to the video decoder; receive a second portion of the second video data at the second spatial resolution for a second playback time that is later than the first playback time; and transmit the second portion of the second video data at the second spatial resolution to the video decoder.

[0070] Figure 2 is a block diagram illustrating in greater detail an exemplary set of components of retrieval unit 52 of Figure 1. In this example, retrieval unit 52 includes a digital video broadcast (DVB) middleware unit 100, a DASH client 110, and a media application 112.

[0071] In this example, the DVB middleware unit 100 further includes a DVB receiving unit 106, a cache 104, and a proxy server unit 102. In this example, the DVB receiving unit 106 is configured to receive data via DVB, for example, that is, the DVB receiving unit 106 may function as a DVB broadcast server, for example, may receive files via broadcast from the server device 60.

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

[0073] The proxy server unit 102 may act as a server for the DASH client 110. For example, the proxy server unit 102 may provide the DASH client 110 with an MPD file or other manifest file. The proxy server unit 102 may advertise availability times for 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.

[0074] According to the techniques of this disclosure, the DVB receiving unit 106 can receive a media presentation that includes two or more representations with different resolutions. The DVB receiving unit 106 can also receive an ARI track that includes quality values ​​of segments or chunks of the representations. The DVB receiving unit 106 can store the received segments or chunks in the cache 104. The DASH client 110 can retrieve the data of the ARI track via the proxy server unit 102, determine which segment or chunk has a higher quality value for a given play time, and then retrieve the segment or chunk with the higher quality value for that play time.

[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, a number of representations 124A-124N (representations 124), and an addressable resource information (ARI) track 134. Representation 124A includes optional header data 126 and segments 128A-128N (segments 128), while representation 124N includes optional header data 130 and segments 132A-132N (segments 132). The letter N is used for convenience to designate the last movie fragment in each of the representations 124. In some examples, there may be different numbers of movie fragments between the representations 124.

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

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

[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, such as height, width, and bandwidth requirements. Such characteristics may be described by data in MPD 122, although such data is not shown in the example of FIG. 3. MPD 122 may include characteristics as described by 3GPP specifications, plus any or all of the signaled information described in this disclosure.

[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 separately retrievable using a streaming network protocol such as DASH. In this manner, a destination device such as client device 40 may retrieve a segment 128 or 132 using an HTTP GET request. In some examples, client device 40 may retrieve a particular byte range of a segment 128 or 132 using an HTTP partial GET request.

[0080] ARI track 134 includes, among other things, quality values ​​136A-136N (quality values ​​136). In general, quality values ​​136 include values ​​that represent the quality of corresponding (i.e., play-time aligned) segments of representation 124. Thus, for example, quality value 136A includes quality values ​​for segments 128A and 132A, quality value 136B includes quality values ​​for segments 128B and 132B, quality value 136A includes quality values ​​for segments 128N and 132N, and so on.

[0081] In accordance with the techniques of this disclosure, representation 124A may include video data at a first resolution (e.g., 4K) and representation 124N may include video data at a second, different resolution (e.g., 1080p). Representations 124A and 124N may have similar or identical bitrates. Thus, matched segments 128 and 132 may have similar or identical bitrates. For example, segment 128A and segment 132A may have similar or identical bitrates but may include video data encoded at different resolutions.

[0082] Some of the segments 124 may have a higher quality than the corresponding segments 132 (at a lower spatial resolution), as indicated by the quality values ​​136. However, in some cases, one or more of the segments 132 may have a higher quality value than the corresponding segments 124, as indicated by the quality values ​​136. Thus, the client device 40 (FIG. 1) may use the quality values ​​136 to determine which segment of a given set of corresponding segments has a higher quality value and retrieve one of the segments 124, 132 having the higher quality value. For example, if the quality value 136A indicates that the segment 124A has a higher quality value than the segment 132A, the client device 40 (or its retrieval unit 52) ​​may retrieve the segment 124A. As another example, if the quality value 136B indicates that the segment 132B has a higher quality than the segment 124B, the client device 40 or the retrieval unit 52 may retrieve the segment 132B.

[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 conforms to the arrangement of data shown in the example of FIG. 4. The video file 150 may be said to encapsulate a segment. As explained above, video files according to the ISO Base Media File Format and its extensions store data in a series of objects called "boxes." In the example of FIG. 4, the video file 150 includes a file type (FTYP) box 152, a movie (MOOV) box 154, a segment index (sidx) box 162, a movie fragment (MOOF) box 164, and a movie fragment random access (MFRA) box 166. Although FIG. 4 represents an example video file, it should be understood that other media files may include other types of media data (e.g., audio data, timed text data, etc.) that are similarly arranged to the data of the video file 150 according to the ISO Base Media File Format and its extensions.

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

[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 that will be used to update the MPD. As another example, the MPD update box may include data for updating the MPD. In some examples, the MPD update box may immediately follow a segment type (STYP) box (not shown) of video file 150, where the STYP box may define a segment type for video file 150.

[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 representing when video file 150 was originally created, data representing when video file 150 was last modified, data representing a timescale of video file 150, data representing the duration of playback of video file 150, or other data generally describing video file 150.

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

[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 temporal and / or spatial information of the corresponding track. If 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 within a TRAK box representing a parameter set track that a sequence level SEI message is present for the parameter set track.

[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 in MOOV box 154. Thus, all coded video samples may be contained in movie fragment 164 rather than in MOOV box 154.

[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 (MEHD) box that describes the duration of the corresponding one of the movie fragments 164.

[0091] As mentioned above, encapsulation unit 30 may store the sequence data set in a video sample that does not include the 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 the 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.

[0092] The SIDX box 162 is an optional element of the video file 150; that is, a video file conforming to the 3GPP file format or other such file formats does not necessarily include the SIDX box 162. According to an example of the 3GPP file format, the SIDX box may be used to identify a subsegment of a segment (such as 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 corresponding to a Media Data box, where the Media Data box containing the data referenced by a Movie Fragment box follows that Movie Fragment box and precedes 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 a Segment Index box are always contiguous within the segment. The referenced size gives a count of the number of bytes in the referenced material."

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

[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 multiple 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 sequence number order.

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

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

[0097] FIG. 5 is a conceptual diagram illustrating an example of a retrieval technique according to the techniques of this disclosure. In particular, graph 170 illustrates the available bit rate over time at which segments of media data can be retrieved at times 172A-172D (times 172). In the first example shown in FIG. 5, a basic client 174 retrieves segments every time 172 at 4K resolution. The basic client 174 is considered "basic" in the sense that the basic client 174 does not implement the techniques of this disclosure. Thus, signaling of quality values ​​in an ARI track according to the techniques of this disclosure is backward compatible with client devices that are not configured to perform these techniques.

[0098] However, in another example, Advanced Client 176 is configured to perform the techniques of this disclosure. In this example, at times 172A, 172C, and 172D, Advanced Client 176 determines that the segment with 4K resolution has a higher quality value. However, during time 172B, Advanced Client 176 determines (e.g., using an ARI track signaling a quality value for the segment) that the segment with 1080p resolution is of higher quality. Thus, Advanced Client 176 retrieves the segment from the resolution with 1080p resolution instead.

[0099] 6 is a flow chart illustrating an example method for retrieving media data in accordance with techniques of this disclosure. For purposes of illustration and explanation, the method of FIG. 6 is described with reference to client device 40 and server device 60 of FIG.

[0100] Initially, client device 40 may request a manifest file for a media presentation (200). Client device 40 may, for example, send an HTTP GET request including a URL for the manifest file to server device 60. In response, server device 60 may send the requested manifest file to client device 40 (202).

[0101] The client device 40 may then receive the manifest file (204). Using the manifest file, the client device 40 may determine a switching set having a matching display resolution for the display (e.g., video output 44) of the client device 40 (206). The switching set may have a matching display resolution in the sense that the switching set includes representations having an encoding resolution that is less than or equal to the display resolution of the display for the client device 40.

[0102] The client device 40 may further receive and process an Addressable Resource Index (ARI) track for the switch set. Through streaming and playing back of the media data for the selected switch set, the client device 40 may use the data of the ARI track to determine quality values ​​of the temporally aligned segments for a particular presentation time. The client device 40 may then use the quality values ​​of the ARI track to determine the segment (or chunk) having the highest quality value for the particular presentation time (208). The client device 40 may request the determined segment (210). For example, the client device 40 may construct an HTTP GET request specifying the URL of the determined segment and send the HTTP GET request to the server device 60. The server device 60 may then receive the request (212) and send the requested segment to the client device 40 (214).

[0103] Alternatively, the client device 40 may receive a broadcast media stream including two or more representations or other sets of video data having different spatial resolutions. As described with respect to FIG. 2, the DVB middleware unit 100 may cache the received video data. The operations attributed to the server device 60 above may instead be performed by the proxy server unit 102. That is, the DASH client 110 may retrieve the determined segment (having the highest quality value indicated by the ARI track) from the proxy server unit 102.

[0104] Client device 40 may then receive the segments (216) and send video data for the segments to video decoder 48 (218).

[0105] In this manner, the method of FIG. 6 represents an example of a method for retrieving video data and includes determining that the media presentation includes first video data at a first spatial resolution and second video data at a second spatial resolution, where the second spatial resolution is different from the first spatial resolution; receiving a first portion of the first video data at the first spatial resolution for a first playback time; transmitting the first portion of the first video data at the first spatial resolution to a video decoder; receiving a second portion of the second video data at a second spatial resolution for a second playback time that is later than the first playback time; and transmitting the second portion of the second video data at the second spatial resolution to the video decoder.

[0106] Various examples of the techniques of this disclosure are summarized in the following paragraphs.

[0107] Clause 1: A method for receiving media data, the method comprising: determining that a media presentation includes first video data at a first spatial resolution and second video data at a second spatial resolution, the second spatial resolution being different from the first spatial resolution; receiving a first portion of the first video data at the first spatial resolution for a first playback time; transmitting the first portion of the first video data at the first spatial resolution to a video decoder; receiving a second portion of the second video data at a second spatial resolution for a second playback time that is later than the first playback time; and transmitting the second portion of the second video data at the second spatial resolution to the video decoder.

[0108] Clause 2: The method of clause 1, further comprising receiving an Addressable Resource Index (ARI) track for a media presentation, the ARI track including data representing a first quality for first video data at a first spatial resolution for a first playback time and a second quality of second video data at a second spatial resolution for the first playback time, and determining that the first quality is higher than the second quality, wherein receiving the first portion of the first video data at the first spatial resolution for the first playback time includes retrieving the first portion of the first video data at the first spatial resolution for the first playback time instead of the second video data at the second spatial resolution for the first playback time in response to determining that the first quality is higher than the second quality.

[0109] Clause 3: The method of clause 2, wherein the second spatial resolution is higher than the first spatial resolution.

[0110] Clause 4: The method of clause 2, wherein the first video data at a first spatial resolution for a first playback time has an equal bit rate to the second video data at a second spatial resolution for the first playback time.

[0111] Clause 5: The method of clause 2, wherein the first quality and the second quality represent one or more quality measures other than spatial resolution and bit rate.

[0112] Clause 6: The method of clause 2, wherein the ARI track further includes data representing a third quality for the first video data at the first spatial resolution at the second playback time and a fourth quality for the second video data at the second spatial resolution at the second playback time, the method further including determining that the fourth quality is higher than the third quality, and receiving the second portion of the second video data at the second spatial resolution for the second playback time includes retrieving the second portion of the second video data at the second spatial resolution for the second playback time instead of the first video data at the first spatial resolution for the second playback time in response to determining that the fourth quality is higher than the third quality.

[0113] Clause 7: The method of clause 6, wherein the first spatial resolution is greater than the second spatial resolution.

[0114] Clause 8: The method of clause 6, wherein the first video data at the first spatial resolution for the second playback time has an equal bit rate to the second video data at the second spatial resolution for the second playback time.

[0115] Clause 9: The method of clause 6, wherein the third quality and the fourth quality represent one or more quality measures other than spatial resolution and bit rate.

[0116] Clause 10: The method of clause 1, wherein the media presentation includes a first representation including first video data at a first spatial resolution and a second representation including second video data at a second spatial resolution, and the media presentation includes a switch set including both the first representation and the second representation.

[0117] Clause 11: The method of clause 1, wherein receiving the first portion of the first video data at the first spatial resolution for the first playback time includes receiving the first portion of the first video data at the first spatial resolution for the first playback time via broadcast by the middleware unit, the method further including caching the first portion of the first video data at the first spatial resolution for the first playback time by the middleware unit, and retrieving the first portion of the first video data at the first spatial resolution for the first playback time from the middleware unit by the Dynamic Adaptive Streaming over HTTP (DASH) client.

[0118] Clause 12: The method of clause 1, wherein receiving the second portion of the second video data at the second spatial resolution for the second playback time includes receiving the second portion of the second video data at the second spatial resolution for the second playback time via broadcast by the middleware unit, the method further including caching the second portion of the second video data at the second spatial resolution for the second playback time by the middleware unit, and retrieving the second portion of the second video data at the second spatial resolution for the second playback time from the middleware unit by the Dynamic Adaptive Streaming over HTTP (DASH) client.

[0119] Clause 13: A device for retrieving media data, the device comprising: a memory configured to store video data; a video decoder configured to decode the video data; and one or more processors implemented in circuitry configured to: determine that a media presentation includes first video data at a first spatial resolution and second video data at a second spatial resolution, the second spatial resolution being different from the first spatial resolution; receive a first portion of the first video data at the first spatial resolution for a first playback time and transmit the first portion of the first video data at the first spatial resolution to the video decoder; receive a second portion of the second video data at the second spatial resolution for a second playback time that is later than the first playback time and transmit the second portion of the second video data at the second spatial resolution to the video decoder.

[0120] Clause 14: The device of clause 13, wherein the one or more processors are further configured to receive an Addressable Resource Index (ARI) track for the media presentation, the ARI track including data representing a first quality for the first video data at a first spatial resolution for the first playback time and a second quality of the second video data at a second spatial resolution for the first playback time, and determine that the first quality is higher than the second quality, and in response to determining that the first quality is higher than the second quality, the one or more processors are configured to retrieve a first portion of the first video data at the first spatial resolution for the first playback time instead of the second video data at the second spatial resolution during the first playback time.

[0121] Clause 15: A device as described in clause 14, wherein the second spatial resolution is higher than the first spatial resolution.

[0122] Clause 16: The device of clause 14, wherein the first video data at a first spatial resolution for a first playback time has a bit rate equal to the second video data at a second spatial resolution for the first playback time.

[0123] Clause 17: The device of clause 14, wherein the first quality and the second quality represent one or more quality measurements other than spatial resolution and bit rate.

[0124] Clause 18: The device of clause 14, wherein the ARI track further includes data representing a third quality for the first video data at the first spatial resolution at the second playback time and a fourth quality for the second video data at the second spatial resolution at the second playback time, and the one or more processors are further configured to determine that the fourth quality is higher than the third quality, and in response to the one or more processors determining that the fourth quality is higher than the third quality, the one or more processors are configured to retrieve a second portion of the second video data at the second spatial resolution at the second playback time instead of retrieving the first video data at the first spatial resolution for the second playback time.

[0125] Clause 19: A device as described in clause 18, wherein the first spatial resolution is higher than the second spatial resolution.

[0126] Clause 20: The device of clause 18, wherein the first video data at the first spatial resolution for the second playback time has a bit rate equal to the second video data at the second spatial resolution for the second playback time.

[0127] Clause 21: The device of clause 18, wherein the third quality and the fourth quality represent one or more quality measurements other than spatial resolution and bit rate.

[0128] Clause 22: The device of clause 13, wherein the media presentation includes a first representation including first video data at a first spatial resolution and a second representation including second video data at a second spatial resolution, and the media presentation includes a switch set including both the first representation and the second representation.

[0129] Clause 23: The device of clause 13, further comprising a middleware unit configured to receive a first portion of the first video data at the first spatial resolution for the first playback time via broadcast and cache the first portion of the first video data at the first spatial resolution for the first playback time via broadcast, wherein the one or more processors are configured to execute a Dynamic Adaptive Streaming over HTTP (DASH) client to retrieve the first portion of the first video data at the first spatial resolution for the first playback time from the middleware unit.

[0130] Clause 24: The device of clause 13, further comprising a middleware unit configured to receive a second portion of the second video data at the second spatial resolution for the second playback time via broadcast and cache the second portion of the second video data at the second spatial resolution for the second playback time via broadcast, wherein the one or more processors are configured to execute a Dynamic Adaptive Streaming over HTTP (DASH) client to retrieve the second portion of the second video data at the second spatial resolution for the second playback time from the middleware unit.

[0131] Clause 25: The device of clause 13, wherein the apparatus comprises at least one of an integrated circuit, a microprocessor, and a wireless communication device.

[0132] Clause 26: The device of clause 13, comprising: one or more processors having instructions stored thereon that, when executed, cause the processor to determine that the media presentation includes first video data at a first spatial resolution and second video data at a second spatial resolution, the second spatial resolution being different from the first spatial resolution; receive a first portion of the first video data at the first spatial resolution for a first playback time and transmit the first portion of the first video data at the first spatial resolution to a video decoder; receive a second portion of the second video data at a second spatial resolution for a second playback time that is later than the first playback time and transmit the second portion of the second video data at the second spatial resolution to the video decoder.

[0133] Clause 27: The computer-readable storage medium of clause 26, further comprising instructions to cause a processor to receive an Addressable Resource Index (ARI) track for the media presentation, the ARI track including data representing a first quality for the first video data at a first spatial resolution for the first playback time and a second quality of the second video data at a second spatial resolution for the first playback time, and to determine that the first quality is higher than the second quality, and in response to determining that the first quality is higher than the second quality, the instructions to cause the processor to receive the first portion of the first video data at the first spatial resolution for the first playback time include instructions to cause the processor to retrieve the first portion of the first video data at the first spatial resolution for the first playback time instead of the second video data at the second spatial resolution for the first playback time.

[0134] Clause 28: The computer-readable storage medium of clause 27, wherein the second spatial resolution is higher than the first spatial resolution.

[0135] Clause 29: A computer-readable storage medium as described in clause 27, wherein the first video data at a first spatial resolution for a first playback time has a bit rate equal to the second video data at a second spatial resolution for the first playback time.

[0136] Clause 30: The computer-readable storage medium of clause 27, wherein the first quality and the second quality represent one or more quality measures other than spatial resolution and bit rate.

[0137] Clause 31: A computer-readable storage medium as described in clause 27, wherein the ARI track further includes data representing a third quality for the first video data at the first spatial resolution at the second playback time and a fourth quality for the second video data at the second spatial resolution at the second playback time, and further comprising instructions for causing the processor to determine that the fourth quality is higher than the third quality, and wherein the instructions for causing the processor to receive the second portion of the second video data at the second spatial resolution for the second playback time include instructions for causing the processor to retrieve the second portion of the second video data at the second spatial resolution for the second playback time in response to determining that the fourth quality is higher than the third quality, instead of retrieving the first video data at the first spatial resolution for the second playback time.

[0138] Clause 32: A computer-readable storage medium as described in Clause 31, wherein the first spatial resolution is higher than the second spatial resolution.

[0139] Clause 33: A computer-readable storage medium as described in Clause 31, wherein the first video data at the first spatial resolution for the second playback time has a bit rate equal to the second video data at the second spatial resolution for the second playback time.

[0140] Clause 34: The computer-readable storage medium of clause 31, wherein the third quality and the fourth quality represent one or more quality measurements other than spatial resolution and bit rate.

[0141] Clause 35: A computer-readable storage medium as described in clause 26, wherein the media presentation includes a first representation including first video data at a first spatial resolution and a second representation including second video data at a second spatial resolution, and the media presentation includes a switch set including both the first representation and the second representation.

[0142] Clause 36: A computer-readable storage medium as described in clause 26, wherein the instructions for causing the processor to receive a first portion of the first video data at a first spatial resolution for a first playback time include instructions for causing the processor to retrieve the first portion of the first video data at the first spatial resolution for the first playback time from a middleware unit.

[0143] Clause 37: A computer-readable storage medium as described in Clause 26, wherein the instructions for causing the processor to receive a second portion of the second video data at a second spatial resolution for a second playback time include instructions for causing the processor to retrieve the second portion of the second video data at the second spatial resolution for the second playback time from the middleware unit.

[0144] Clause 38: A device for retrieving media data, the device comprising: means for determining that a media presentation includes first video data at a first spatial resolution and second video data at a second spatial resolution, the second spatial resolution different from the first spatial resolution; means for receiving a first portion of the first video data at the first spatial resolution for a first playback time; means for transmitting the first portion of the first video data at the first spatial resolution to a video decoder; means for receiving a second portion of the second video data at a second spatial resolution for a second playback time later than the first playback time; and means for transmitting the second portion of the second video data at the second spatial resolution to the video decoder.

[0145] Clause 39: A method for receiving media data, the method comprising: determining that a media presentation includes first video data at a first spatial resolution and second video data at a second spatial resolution, the second spatial resolution being different from the first spatial resolution; receiving a first portion of the first video data at the first spatial resolution for a first playback time; transmitting the first portion of the first video data at the first spatial resolution to a video decoder; receiving a second portion of the second video data at a second spatial resolution for a second playback time that is later than the first playback time; and transmitting the second portion of the second video data at the second spatial resolution to the video decoder.

[0146] Clause 40: The method of clause 39, further comprising: receiving an Addressable Resource Index (ARI) track for a media presentation, the ARI track including data representing a first quality for the first video data at a first spatial resolution for the first playback time and a second quality of the second video data at a second spatial resolution for the first playback time; and determining that the first quality is higher than the second quality, wherein receiving a first portion of the first video data at the first spatial resolution during the first playback time includes retrieving the first portion of the first video data at the first spatial resolution for the first playback time instead of the second video data at the second spatial resolution for the first playback time in response to determining that the first quality is higher than the second quality.

[0147] Clause 41: The method of clause 40, wherein the second spatial resolution is higher than the first spatial resolution.

[0148] Clause 42: The method of clause 40 or 41, wherein the first video data at a first spatial resolution for a first playback time has an equal bit rate to the second video data at a second spatial resolution for the first playback time.

[0149] Clause 43: The method of any of clauses 40 to 42, wherein the first quality and the second quality represent one or more quality measures other than spatial resolution and bit rate.

[0150] Clause 44: The method of clause 40, wherein the ARI track further includes data representing a third quality for the first video data at the first spatial resolution at the second playback time and a fourth quality for the second video data at the second spatial resolution at the second playback time, the method further including determining that the fourth quality is higher than the third quality, and receiving the second portion of the second video data at the second spatial resolution for the second playback time includes retrieving the second portion of the second video data at the second spatial resolution for the second playback time instead of the first video data at the first spatial resolution for the second playback time in response to determining that the fourth quality is higher than the third quality.

[0151] Clause 45: The method of clause 44, wherein the first spatial resolution is higher than the second spatial resolution.

[0152] Clause 46: The method of clause 44 or 45, wherein the first video data at the first spatial resolution for the second playback time has an equal bit rate to the second video data at the second spatial resolution for the second playback time.

[0153] Clause 47: The method of any of clauses 44 to 46, wherein the third quality and the fourth quality represent one or more quality measures other than spatial resolution and bit rate.

[0154] Clause 48: A method according to any of clauses 39 to 47, wherein the media presentation comprises a first representation comprising first video data at a first spatial resolution and a second representation comprising second video data at a second spatial resolution, the media presentation comprising a switch set comprising both the first representation and the second representation.

[0155] Clause 49: The method of any of clauses 39 to 48, wherein receiving the first portion of the first video data at the first spatial resolution for the first playback time includes receiving, by a middleware unit, the first portion of the first video data at the first spatial resolution for the first playback time via broadcast, and the method further includes caching, by the middleware unit, the first portion of the first video data at the first spatial resolution for the first playback time, and retrieving, by a Dynamic Adaptive Streaming over HTTP (DASH) client, the first portion of the first video data at the first spatial resolution for the first playback time from the middleware unit.

[0156] Clause 50: The method of any of clauses 39 to 49, wherein receiving the second portion of the second video data at the second spatial resolution for the second playback time includes receiving, by a middleware unit, the second portion of the second video data at the second spatial resolution for the second playback time via broadcast, the method further including caching, by the middleware unit, the second portion of the second video data at the second spatial resolution for the second playback time, and retrieving, by a Dynamic Adaptive Streaming over HTTP (DASH) client, the second portion of the second video data at the second spatial resolution for the second playback time from the middleware unit.

[0157] Clause 51: A device for retrieving media data, the device comprising: a memory configured to store video data; a video decoder configured to decode the video data; and one or more processors implemented in circuitry configured to: determine that a media presentation includes first video data at a first spatial resolution and second video data at a second spatial resolution, the second spatial resolution being different from the first spatial resolution; receive a first portion of the first video data at the first spatial resolution for a first playback time and transmit the first portion of the first video data at the first spatial resolution to the video decoder; receive a second portion of the second video data at the second spatial resolution for a second playback time that is later than the first playback time and transmit the second portion of the second video data at the second spatial resolution to the video decoder.

[0158] Clause 52: The device of clause 51, wherein the one or more processors are further configured to receive an Addressable Resource Index (ARI) track for the media presentation, the ARI track including data representing a first quality for the first video data at a first spatial resolution for the first playback time and a second quality of the second video data at a second spatial resolution for the first playback time, and determine that the first quality is higher than the second quality, and in response to determining that the first quality is higher than the second quality, the one or more processors are configured to retrieve a first portion of the first video data at the first spatial resolution for the first playback time instead of the second video data at the second spatial resolution for the first playback time.

[0159] Clause 53: A device as described in clause 52, wherein the second spatial resolution is higher than the first spatial resolution.

[0160] Clause 54: A device as described in clause 52 or 53, wherein the first video data at a first spatial resolution for the first playback time has a bit rate equal to the second video data at a second spatial resolution for the first playback time.

[0161] Clause 55: A device according to any of clauses 52 to 54, wherein the first quality and the second quality represent one or more quality measurements other than spatial resolution and bit rate.

[0162] Clause 56: A device described in any of clauses 52 to 55, wherein the ARI track further includes data representing a third quality for the first video data at the first spatial resolution at the second playback time and a fourth quality for the second video data at the second spatial resolution at the second playback time, and the one or more processors are further configured to determine that the fourth quality is higher than the third quality, and in response to the one or more processors determining that the fourth quality is higher than the third quality, retrieve a second portion of the second video data at the second spatial resolution for the second playback time instead of retrieving the first video data at the first spatial resolution for the second playback time.

[0163] Clause 57: A device as described in clause 56, wherein the first spatial resolution is higher than the second spatial resolution.

[0164] Clause 58: A device as described in clause 56 or 57, wherein the first video data at the first spatial resolution for the second playback time has a bit rate equal to the second video data at the second spatial resolution for the second playback time.

[0165] Clause 59: A device described in any of clauses 56 to 58, wherein the third quality and the fourth quality represent one or more quality measurements other than spatial resolution and bit rate.

[0166] Clause 60: A device described in any of clauses 51 to 59, wherein the media presentation includes a first representation including first video data at a first spatial resolution and a second representation including second video data at a second spatial resolution, and the media presentation includes a switch set including both the first representation and the second representation.

[0167] Clause 61: The device of any of clauses 51 to 60, further comprising a middleware unit configured to receive a first portion of the first video data at the first spatial resolution for the first playback time via broadcast and cache the first portion of the first video data at the first spatial resolution for the first playback time via broadcast, wherein the one or more processors are configured to execute a Dynamic Adaptive Streaming over HTTP (DASH) client to retrieve the first portion of the first video data at the first spatial resolution for the first playback time from the middleware unit.

[0168] Clause 62: The device of any of clauses 51 to 61, further comprising a middleware unit configured to receive a second portion of the second video data at the second spatial resolution for the second playback time via the broadcast and cache the second portion of the second video data at the second spatial resolution for the second playback time via the broadcast, wherein the one or more processors are configured to execute a Dynamic Adaptive Streaming over HTTP (DASH) client to retrieve the second portion of the second video data at the second spatial resolution for the second playback time from the middleware unit.

[0169] Clause 63: A device described in any of clauses 51 to 62, wherein the device comprises at least one of an integrated circuit, a microprocessor, and a wireless communication device.

[0170] Clause 64: A computer-readable storage medium having stored thereon instructions which, when executed, are configured to: cause the processor to determine that the media presentation includes first video data at a first spatial resolution and second video data at a second spatial resolution, the second spatial resolution being different from the first spatial resolution; receive a first portion of the first video data at the first spatial resolution for a first playback time and transmit the first portion of the first video data at the first spatial resolution to a video decoder; receive a second portion of the second video data at a second spatial resolution for a second playback time that is later than the first playback time and transmit the second portion of the second video data at the second spatial resolution to the video decoder.

[0171] Clause 65: The computer-readable storage medium of clause 64, further comprising instructions to cause a processor to receive an Addressable Resource Index (ARI) track for the media presentation, the ARI track including data representing a first quality for the first video data at a first spatial resolution for the first playback time and a second quality of the second video data at a second spatial resolution for the first playback time, and to determine that the first quality is higher than the second quality, and in response to determining that the first quality is higher than the second quality, the instructions to cause the processor to receive the first portion of the first video data at the first spatial resolution for the first playback time include instructions to cause the processor to retrieve the first portion of the first video data at the first spatial resolution for the first playback time instead of the second video data at the second spatial resolution for the first playback time.

[0172] Clause 66: A computer-readable storage medium as described in Clause 65, wherein the second spatial resolution is higher than the first spatial resolution.

[0173] Clause 67: A computer-readable storage medium as described in clause 65 or 66, wherein the first video data at a first spatial resolution for a first playback time has a bit rate equal to the second video data at a second spatial resolution for the first playback time.

[0174] Clause 68: A computer-readable storage medium according to any of clauses 65 to 67, wherein the first quality and the second quality represent one or more quality measures other than spatial resolution and bit rate.

[0175] Clause 69: A computer-readable storage medium as described in any of clauses 65 to 68, wherein the ARI track further includes data representing a third quality for the first video data at the first spatial resolution at the second playback time and a fourth quality for the second video data at the second spatial resolution at the second playback time, and further comprising instructions for causing the processor to determine that the fourth quality is higher than the third quality, and wherein the instructions for causing the processor to receive the second portion of the second video data at the second spatial resolution for the second playback time include instructions for causing the processor to retrieve the second portion of the second video data at the second spatial resolution for the second playback time instead of the first video data at the first spatial resolution for the second playback time in response to determining that the fourth quality is higher than the third quality.

[0176] Clause 70: A computer-readable storage medium as described in Clause 69, wherein the first spatial resolution is higher than the second spatial resolution.

[0177] Clause 71: A computer-readable storage medium as described in clause 69 or 70, wherein the first video data at the first spatial resolution for the second playback time has a bit rate equal to the second video data at the second spatial resolution for the second playback time.

[0178] Clause 72: A computer-readable storage medium according to any of clauses 69 to 71, wherein the third quality and the fourth quality represent one or more quality measures other than spatial resolution and bit rate.

[0179] Clause 73: A computer-readable storage medium according to any of clauses 65 to 72, wherein the media presentation includes a first representation including first video data at a first spatial resolution and a second representation including second video data at a second spatial resolution, and the media presentation includes a switch set including both the first representation and the second representation.

[0180] Clause 74: A computer-readable storage medium according to any of clauses 65 to 73, wherein the instructions for causing a processor to receive a first portion of the first video data at a first spatial resolution for a first playback time include instructions for causing the processor to retrieve the first portion of the first video data at the first spatial resolution for the first playback time from a middleware unit.

[0181] Clause 75: A computer-readable storage medium according to any of clauses 65 to 74, wherein the instructions for causing the processor to receive a second portion of the second video data at a second spatial resolution for a second playback time include instructions for causing the processor to retrieve the second portion of the second video data at the second spatial resolution for the second playback time from the middleware unit.

[0182] Clause 76: A device for retrieving media data, the device comprising: means for determining that a media presentation includes first video data at a first spatial resolution and second video data at a second spatial resolution, the second spatial resolution different from the first spatial resolution; means for receiving a first portion of the first video data at the first spatial resolution for a first playback time; means for transmitting the first portion of the first video data at the first spatial resolution to a video decoder; means for receiving a second portion of the second video data at a second spatial resolution for a second playback time later than the first playback time; and means for transmitting the second portion of the second video data at the second spatial resolution to the video decoder.

[0183] In one or more examples, the functions described 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 a communication medium, which includes any medium that facilitates transfer of a computer program from one place to another, for example, according to a communication protocol. As such, a computer-readable medium may generally correspond to (1) a 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.

[0184] By way of example, and not limitation, such computer-readable storage media may include 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 can be used to store desired program code in the form of instructions or data structures and that can be accessed by a computer. Also, any connection is properly referred to as a computer-readable medium. For example, if instructions are transmitted from a website, server, or other remote source using coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL), or wireless technologies such as infrared, radio, and microwave, the coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave are included within 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 refer to 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 using lasers. Combinations of the above are also intended to be included within the scope of computer readable media.

[0185] The instructions may be executed by one or more processors, such as one or more digital signal processors (DSPs), general-purpose microprocessors, application specific integrated circuits (ASICs), field programmable logic arrays (FPGAs), or other equivalent integrated or discrete logic circuitry. Thus, the term "processor" as used herein may refer to any of the above structures, or any other structure suitable for implementing the techniques described herein. In addition, in some aspects, the functionality described herein may be provided within dedicated hardware and / or software modules configured for encoding and decoding, or may be incorporated into a combined codec. The techniques may also be fully implemented in one or more circuits or logic elements.

[0186] The techniques of this disclosure may be implemented in a wide variety of devices or apparatuses, including a wireless handset, an integrated circuit (IC), or a set of ICs (e.g., a chipset). Various components, modules, or units are described in this disclosure to highlight functional aspects of devices configured to implement the disclosed techniques, but do not necessarily require realization by different hardware units. Rather, as described above, the various units may be combined in a codec hardware unit or may be provided by a collection of interoperable hardware units including one or more processors as described above, in conjunction with suitable software and / or firmware.

[0187] Various examples have been described. These and other examples are within the scope of the following claims.

Claims

1. 1. A method for receiving media data, comprising: determining that the media presentation includes first video data at a first spatial resolution and second video data at a second spatial resolution, the second spatial resolution being different from the first spatial resolution; receiving a first portion of the first video data at the first spatial resolution for a first playback time; transmitting the first portion of the first video data at the first spatial resolution to a video decoder; receiving a second portion of the second video data at the second spatial resolution for a second playback time that is later than the first playback time; transmitting the second portion of the second video data at the second spatial resolution to the video decoder; A method comprising:

2. receiving an Addressable Resource Index (ARI) track for the media presentation, the ARI track including data representing a first quality for the first video data at the first spatial resolution for the first playback time and a second quality for the second video data at the second spatial resolution for the first playback time; determining that the first quality is greater than the second quality; 2. The method of claim 1, wherein receiving the first portion of the first video data at the first spatial resolution for the first playback time comprises retrieving the first portion of the first video data at the first spatial resolution for the first playback time instead of the second video data at the second spatial resolution for the first playback time in response to determining that the first quality is higher than the second quality.

3. The method of claim 2 , wherein the second spatial resolution is greater than the first spatial resolution.

4. 3. The method of claim 2, wherein the first video data at the first spatial resolution for the first playback time has an equal bit rate to the second video data at the second spatial resolution for the first playback time.

5. The method of claim 2 , wherein the first quality and the second quality represent one or more quality measures other than spatial resolution and bit rate.

6. the ARI track further includes data representing a third quality for the first video data at the first spatial resolution at the second playback time and a fourth quality for the second video data at the second spatial resolution at the second playback time, the method further including determining that the fourth quality is greater than the third quality; 3. The method of claim 2, wherein receiving the second portion of the second video data at the second spatial resolution for the second playback time includes retrieving the second portion of the second video data at the second spatial resolution for the second playback time instead of the first video data at the first spatial resolution for the second playback time in response to determining that the fourth quality is higher than the third quality.

7. The method of claim 6 , wherein the first spatial resolution is greater than the second spatial resolution.

8. 7. The method of claim 6, wherein the first video data at the first spatial resolution for the second playback time has a bit rate equal to the second video data at the second spatial resolution for the second playback time.

9. The method of claim 6 , wherein the third quality and the fourth quality represent one or more quality measures other than spatial resolution and bit rate.

10. 2. The method of claim 1 , wherein the media presentation includes a first representation including the first video data at the first spatial resolution and a second representation including the second video data at the second spatial resolution, and the media presentation includes a switch set including both the first representation and the second representation.

11. receiving the first portion of the first video data at the first spatial resolution for the first playback time includes receiving, by a middleware unit, the first portion of the first video data at the first spatial resolution for the first playback time via broadcast, the method comprising: caching, by the middleware unit, the first portion of the first video data at the first spatial resolution for the first playback time; Retrieving, by a Dynamic Adaptive Streaming over HTTP (DASH) client, from the middleware unit, the first portion of the first video data at the first spatial resolution for the first playback time; The method of claim 1 further comprising:

12. Receiving the second portion of the second video data at the second spatial resolution for the second playback time includes receiving, by a middleware unit, the second portion of the second video data at the second spatial resolution for the second playback time via broadcast, the method comprising: caching, by the middleware unit, the second portion of the second video data at the second spatial resolution for the second playback time; Retrieving, by a Dynamic Adaptive Streaming over HTTP (DASH) client, from the middleware unit, the second portion of the second video data at the second spatial resolution for the second playback time; The method of claim 1 further comprising:

13. 1. A device for retrieving media data, comprising: a memory configured to store video data; a video decoder configured to decode the video data; One or more processors implemented in circuitry, determining that the media presentation includes first video data at a first spatial resolution and second video data at a second spatial resolution, the second spatial resolution being different from the first spatial resolution; receiving a first portion of the first video data at the first spatial resolution for a first playback time; transmitting the first portion of the first video data at the first spatial resolution to the video decoder; receiving a second portion of the second video data at the second spatial resolution for a second playback time that is later than the first playback time; one or more processors configured to transmit the second portion of the second video data at the second spatial resolution to the video decoder; A device comprising:

14. the one or more processors: receiving an Addressable Resource Index (ARI) track for the media presentation, the ARI track including data representing a first quality for the first video data at the first spatial resolution for the first playback time and a second quality for the second video data at the second spatial resolution for the first playback time; further configured to determine that the first quality is greater than the second quality; the one or more processors are configured to, in response to determining that the first quality is greater than the second quality, retrieve the first portion of the first video data at the first spatial resolution for the first playback time instead of the second video data at the second spatial resolution for the first playback time. The device of claim 13.

15. The device of claim 14 , wherein the second spatial resolution is greater than the first spatial resolution.

16. 15. The device of claim 14, wherein the first video data at the first spatial resolution for the first playback time has an equal bit rate to the second video data at the second spatial resolution for the first playback time.

17. The device of claim 14 , wherein the first quality and the second quality represent one or more quality measures other than spatial resolution and bit rate.

18. the ARI track further includes data representing a third quality for the first video data at the first spatial resolution at the second playback time and a fourth quality for the second video data at the second spatial resolution at the second playback time, the one or more processors further configured to determine that the fourth quality is higher than the third quality; in response to determining that the fourth quality is greater than the third quality, the one or more processors are configured to retrieve the second portion of the second video data at the second spatial resolution for the second playback time instead of the first video data at the first spatial resolution for the second playback time. The device of claim 14.

19. The device of claim 18 , wherein the first spatial resolution is greater than the second spatial resolution.

20. 20. The device of claim 18, wherein the first video data at the first spatial resolution for the second playback time has a bit rate equal to the second video data at the second spatial resolution for the second playback time.

21. The device of claim 18 , wherein the third quality and the fourth quality represent one or more quality measures other than spatial resolution and bit rate.

22. 14. The device of claim 13, wherein the media presentation includes a first representation including the first video data at the first spatial resolution and a second representation including the second video data at the second spatial resolution, the media presentation including a switch set including both the first representation and the second representation.

23. 14. The device of claim 13, further comprising a middleware unit configured to receive the first portion of the first video data at the first spatial resolution for the first playback time via broadcast and cache the first portion of the first video data at the first spatial resolution for the first playback time via broadcast, wherein the one or more processors are configured to execute a Dynamic Adaptive Streaming over HTTP (DASH) client to retrieve the first portion of the first video data at the first spatial resolution for the first playback time from the middleware unit.

24. 14. The device of claim 13, further comprising a middleware unit configured to receive the second portion of the second video data at the second spatial resolution for the second playback time via broadcast and cache the second portion of the second video data at the second spatial resolution for the second playback time via broadcast, wherein the one or more processors are configured to execute a Dynamic Adaptive Streaming over HTTP (DASH) client to retrieve the second portion of the second video data at the second spatial resolution for the second playback time from the middleware unit.

25. The device, Integrated circuits, Microprocessor, Wireless Communication Devices The device of claim 13 , comprising at least one of:

26. A computer-readable storage medium having stored thereon instructions that, when executed, cause a processor to: determining that the media presentation comprises first video data at a first spatial resolution and second video data at a second spatial resolution, the second spatial resolution being different from the first spatial resolution; receiving a first portion of the first video data at the first spatial resolution for a first playback time; transmitting the first portion of the first video data at the first spatial resolution to a video decoder; receiving a second portion of the second video data at the second spatial resolution for a second presentation time that is later than the first presentation time; transmitting the second portion of the second video data at the second spatial resolution to the video decoder. A computer-readable storage medium.

27. The processor, receiving an Addressable Resource Index (ARI) track for the media presentation, the ARI track including data representing a first quality for the first video data at the first spatial resolution for the first playback time and a second quality for the second video data at the second spatial resolution for the first playback time; determining that the first quality is greater than the second quality; the instructions to cause the processor to receive the first portion of the first video data at the first spatial resolution for the first playback time include instructions to cause the processor to retrieve, in response to determining that the first quality is higher than the second quality, the first portion of the first video data at the first spatial resolution for the first playback time instead of the second video data at the second spatial resolution for the first playback time.

27. The computer-readable storage medium of claim 26.

28. 30. The computer-readable storage medium of claim 27, wherein the second spatial resolution is greater than the first spatial resolution.

29. 30. The computer-readable storage medium of claim 27, wherein the first video data at the first spatial resolution for the first playback time has an equal bit rate to the second video data at the second spatial resolution for the first playback time.

30. 30. The computer-readable storage medium of claim 27, wherein the first quality and the second quality represent one or more quality measures other than spatial resolution and bit rate.

31. the ARI track further includes data representing a third quality for the first video data at the first spatial resolution at the second playback time and a fourth quality for the second video data at the second spatial resolution at the second playback time, the fourth quality being greater than the third quality; the instructions to cause the processor to receive the second portion of the second video data at the second spatial resolution for the second playback time include instructions to cause the processor to retrieve, in response to determining that the fourth quality is higher than the third quality, the second portion of the second video data at the second spatial resolution for the second playback time instead of the first video data at the first spatial resolution for the second playback time.

28. The computer-readable storage medium of claim 27.

32. 32. The computer-readable storage medium of claim 31, wherein the first spatial resolution is greater than the second spatial resolution.

33. 32. The computer-readable storage medium of claim 31 , wherein the first video data at the first spatial resolution for the second playback time has a bit rate equal to the second video data at the second spatial resolution for the second playback time.

34. 32. The computer-readable storage medium of claim 31, wherein the third quality and the fourth quality represent one or more quality measures other than spatial resolution and bit rate.

35. 27. The computer-readable storage medium of claim 26, wherein the media presentation includes a first representation including the first video data at the first spatial resolution and a second representation including the second video data at the second spatial resolution, the media presentation including a switch set including both the first representation and the second representation.

36. 27. The computer-readable storage medium of claim 26, wherein the instructions to cause the processor to receive the first portion of the first video data at the first spatial resolution for the first playback time include instructions to cause the processor to retrieve the first portion of the first video data at the first spatial resolution for the first playback time from a middleware unit.

37. 27. The computer-readable storage medium of claim 26, wherein the instructions to cause the processor to receive the second portion of the second video data at the second spatial resolution for the second playback time include instructions to cause the processor to retrieve the second portion of the second video data at the second spatial resolution for the second playback time from a middleware unit.

38. 1. A device for retrieving media data, comprising: means for determining that a media presentation includes first video data at a first spatial resolution and second video data at a second spatial resolution, the second spatial resolution being different from the first spatial resolution; and means for receiving a first portion of the first video data at the first spatial resolution for a first playback time; means for transmitting the first portion of the first video data at the first spatial resolution to a video decoder; means for receiving a second portion of the second video data at the second spatial resolution for a second presentation time that is later than the first presentation time; means for transmitting the second portion of the second video data at the second spatial resolution to the video decoder; A device comprising:

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