Repair mechanism for adaptive bitrate multicast

Abstract

An example device for retrieving media data includes a memory configured to store the media data; and one or more processors implemented in circuitry and configured to: receive data indicating a packet loss signaling mechanism, wherein the packet loss signaling mechanism includes at least one of: fragments are transmitted in chunks, transport object identifiers (TOIs) are contiguous, or the last packet of an object assigned to a TOI has a specific flag set in a header of the last packet, a base URL, a maximum delay, or a synchronization point in a file delivery header; detect packet loss using at least one packet loss signaling mechanism, the lost packet including missing media data; generate a byte range request for the missing media data using information from the file delivery header; and deliver an appropriate media object to a media application.

Description

[0001] This application claims the benefit of U.S. Application No. 17 / 039,442, filed September 30, 2020, and U.S. Provisional Application No. 62 / 908,949, filed October 1, 2019, the entire contents of each of which are incorporated herein by reference. Technical Field

[0002] The present disclosure relates to transmission of media data. Background Art

[0003] Digital video capabilities may be integrated into a variety 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 wireless telephones, video teleconferencing equipment, etc. Digital video devices implement video compression techniques, such as those described in 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 of such standards, for more efficiently transmitting and receiving digital video information.

[0004] After encoding the video data, the video data may be packaged for transmission or storage. The video data may be 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 and its extensions. Summary of the invention

[0005] In general, the present disclosure describes techniques for detecting packet loss and retrieving lost media data. In particular, according to the techniques of the present disclosure, a server device can signal a packet loss signaling mechanism for use by a client device to detect packet loss of a streaming media bitstream. The packet loss signaling mechanism can be one or more of the following: fragments are transmitted in blocks, the transport object identifier (TOI) is continuous, or the last packet of an object assigned to a TOI has a specific flag set in the header of the last packet, a base uniform resource locator (URL), a maximum delay, or a synchronization point in a file delivery header. The client device can use the packet loss signaling mechanism to detect lost packets in a streaming media bitstream. In response to detecting a lost packet, the client device can use a byte range request to retrieve some or all of the missing media data of the lost packet, the byte range request specifying a portion (e.g., a fragment) of a media file that includes the media data included in the lost packet. In this way, the client device can obtain an appropriate media object, wherein the appropriate media object may still be missing some missing media data, but is formatted so that the appropriate media object can be properly parsed, decoded, and presented.

[0006] In one example, a method of retrieving media data includes receiving data indicating a packet loss signaling mechanism, wherein the packet loss signaling mechanism includes at least one of the following: fragments are transmitted in blocks, transport object identifiers (TOIs) are consecutive, or the last packet of an object assigned to the TOI has a specific flag set in the header of the last packet, a base URL, a maximum delay, or a synchronization point in a file delivery header; detecting packet loss using at least one packet loss signaling mechanism, the lost packet including missing media data; generating a byte range request for the missing media data using information from the file delivery header; and delivering an appropriate media object to a media application.

[0007] In another example, an apparatus for retrieving media data includes a memory configured to store the media data; and one or more processors implemented in circuitry and configured to: receive data indicating a packet loss signaling mechanism, wherein the packet loss signaling mechanism includes at least one of: fragments are transmitted in chunks, transport object identifiers (TOIs) are consecutive, or the last packet of an object assigned to a TOI has a specific flag set in a header of the last packet, a base URL, a maximum delay, or a synchronization point in a file delivery header; detect packet loss using at least one packet loss signaling mechanism, the lost packet including missing media data; generate a byte range request for the missing media data using information of the file delivery header; and deliver an appropriate media object to a media application.

[0008] In another example, a computer-readable storage medium having instructions stored thereon, which, when executed, cause a processor to: receive data indicating a packet loss signaling mechanism, wherein the packet loss signaling mechanism includes at least one of: fragments are transmitted in blocks, transport object identifiers (TOIs) are consecutive, or the last packet of an object assigned to a TOI has a specific flag set in a header of the last packet, a base URL, a maximum delay, or a synchronization point in a file delivery header; detect packet loss using at least one packet loss signaling mechanism, the lost packet including missing media data; generate a byte range request for the missing media data using information of the file delivery header; and deliver an appropriate media object to a media application.

[0009] In another example, an apparatus for retrieving media data includes means for receiving data indicating a packet loss signaling mechanism, wherein the packet loss signaling mechanism includes at least one of: fragments are transmitted in blocks, transport object identifiers (TOIs) are consecutive, or the last packet of an object assigned to the TOI has a specific flag set in the header of the last packet, a base URL, a maximum delay, or a synchronization point in a file delivery header; means for detecting packet loss using the at least one packet loss signaling mechanism, the lost packet including missing media data; means for generating a byte range request for the missing media data using information of the file delivery header; and means for delivering an appropriate media object to a media application.

[0010] In another example, a method of transmitting media data includes transmitting data indicating a packet loss signaling mechanism, wherein the packet loss signaling mechanism includes at least one of the following: fragments are transmitted in blocks, transmission object identifiers (TOIs) are consecutive, or the last packet of an object assigned to the TOI has a specific flag set in the header of the last packet, a base URL, a maximum delay, or a synchronization point in a file delivery header; transmitting one or more packets including media data via a broadcast or multicast protocol; receiving a byte range request from a client device via a unicast protocol, the byte range request indicating media data of one of the lost packets; and in response to the byte range request, transmitting the media data of the byte range to the client device via the unicast protocol.

[0011] In another example, a device for transmitting media data includes a memory configured to store video data; and one or more processors implemented in circuits and configured to: transmit data indicating a packet loss signaling mechanism, wherein the packet loss signaling mechanism includes at least one of the following: fragments are transmitted in blocks, transmission object identifiers (TOIs) are consecutive, or the last packet of an object assigned to a TOI has a specific flag set in the header of the last packet, a base URL, a maximum delay, or a synchronization point in a file delivery header; transmit one or more packets including media data via a broadcast or multicast protocol; receive a byte range request from a client device via a unicast protocol, the byte range request indicating media data of one of the lost packets; and in response to the byte range request, transmit the media data of the byte range to the client device via the unicast protocol.

[0012] In another example, a computer-readable storage medium having instructions stored thereon, which, when executed, cause a processor to: transmit data indicating a packet loss signaling mechanism, wherein the packet loss signaling mechanism includes at least one of the following: fragments are transmitted in blocks, transmission object identifiers (TOIs) are consecutive, or the last packet of an object assigned to a TOI has a specific flag set in a header of the last packet, a base URL, a maximum delay, or a synchronization point in a file delivery header; transmit one or more packets including media data via a broadcast or multicast protocol; receive a byte range request from a client device via a unicast protocol, the byte range request indicating media data of one of the lost packets; and transmit the byte range of media data to the client device via the unicast protocol in response to the byte range request.

[0013] In another example, a device for transmitting media data includes a component for transmitting data indicating a packet loss signaling mechanism, wherein the packet loss signaling mechanism includes at least one of the following: fragments are transmitted in the form of blocks, transmission object identifiers (TOIs) are consecutive, or the last packet of an object assigned to the TOI has a specific flag set in the header of the last packet, a base URL, a maximum delay, or a synchronization point in the file delivery header; a component for transmitting one or more packets including media data via a broadcast or multicast protocol; a component for receiving a byte range request from a client device via a unicast protocol, the byte range request indicating media data of one of the lost packets; and a component for transmitting the media data of the byte range to the client device via the unicast protocol in response to the byte range request.

[0014] One or more examples will be described in detail in the accompanying drawings and the following description. Other features, objects, and advantages will be apparent from the description, drawings, and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a block diagram illustrating an example system that implements techniques for streaming media data over a network.

[0016] Figure 2 is a block diagram illustrating an example set of components of a retrieval unit of a client device.

[0017] Figure 3 is a conceptual diagram illustrating elements of example multimedia content.

[0018] Figure 4 is a block diagram illustrating elements of an example video file, which may correspond to segments.

[0019] Figure 5 is a conceptual diagram illustrating an example system including a transmitter and a receiver according to techniques of this disclosure.

[0020] Figure 6 is a flow chart illustrating an example method according to the techniques of this disclosure. DETAILED DESCRIPTION

[0021] Unidirectional content delivery protocols, such as File Delivery over Unidirectional Transport (FLUTE), described in T. Paila et al., "FLUTE—Unidirectional File Delivery over Unidirectional Transport," Network Working Group, RFC 6726, November 2012, available at tools.ietf.org / html / rfc6726, and ROUTE specify various mechanisms for detecting packet loss at various levels of the multicast protocol. This loss detection can trigger a repair procedure so that the entire transport object is not lost due to packet loss. Repair is usually initiated as a byte range request, so the receiver needs to have sufficient information to initiate such a request.

[0022] Procedures may be arranged as follows. The transmitter provides information (e.g., required information) in the content delivery protocol settings and in the single packets to identify lost packets and enable repair procedures. The receiver uses this information to repair the packets, typically via unicast byte range requests, or, if these requests are not available or successful, or arrive late, may signal the loss via the HTTP interface.

[0023] The loss detection signaling mechanism may include the following. At the lowest level, detection of lost packets can be achieved by signaling directly in the header of the transport packet. For example, in ROUTE, when using a mode that transmits the object and the packets within the object in sequence, the start_offset field and the B-flag, EXT_TOLLCT extension header and the transport object identifier (TOI) field can be used in the LCT packet header. The start_offset field indicates the starting byte position of the data in the current packet, relative to the first byte of the delivery object. Here, the packet consists of a continuous data portion of the delivery object. Therefore, the receiver can detect lost packets when receiving a packet with a start_offset, where the start_offset is inconsistent with the start_offset and the payload size of the last packet. The b-flag can be set in the last packet of the delivery object. This, together with the EXT_TOL LCT header extension (signaling the length of the transport object) and / or the TOI field, can be used to detect packet loss. For example, starting to receive packets with a new TOI without receiving packets with a set B flag may indicate lost packets.

[0024] The repair signaling mechanism may include the following. In ROUTE, as described above, start_offset and packet size can be used to determine the missing byte range in the delivery object. Therefore, for a missing packet j that comes after received packet i and before received packet k, the byte range of the missing data is "missing data byte range = start_offset(i)+size(i)to start_offset(k)1". If the missing packet is the last packet of the delivery object, the exact size cannot be determined in this way, and the receiver will have to request all bytes until the end of the delivery object.

[0025] Both FLUTE and ROUTE provide an expiration mechanism for File Delivery Table (FDT) and Enhanced FDT (EFDT) instances, respectively. This also implicitly signals that multicast packets signaled by the FDT or EFDT instance may not be expected after the above timeout. The signaling Alternate-Content-Location-1 and Alternate-Content-Location-2 elements in FDT / EFDT enable the gateway to find the location to access the same object via unicast. The object metadata expiration timeout in the FDT / EFDT instance can also be signaled in the control plane in the service / session metadata signaling in combination with or instead of the signaling discussed above. The control plane can carry the base URL to reconstruct the location of the same content via unicast.

[0026] The signaling between the multicast gateway and the DASH player may include the following: In the case where the multicast gateway cannot guarantee the delivery of error-free content to the DASH player, special signaling may be required between the multicast gateway and the DASH player to handle this situation.

[0027] According to TS26.346 section 7.9.2, streaming applications may accept partial files. Applications that use HTTP GET requests to retrieve files may include in the HTTP GET request an "Accept" request header as defined in RFC 7231, and the new 3GPP-defined media type "application / 3gpp-partial". Applications that use HTTP GET requests to retrieve files may include in the GET request an "Accept" request header as defined in RFC 7231, and the new 3GPP-defined media type "application / 3gpp-partial". By providing this header and issuing such a partial-file-accept request, the application signals that it is able to receive partial file responses.

[0028] An example of using such an Accept header is:

[0029] Accept: * / *, application / 3gpp-part

[0030] In this example, the application indicates that it will accept all media types in the response, as well as the specific "incomplete" types specified by the application / 3gpp-part.

[0031] If the MBMS client receives a regular HTTP GET request including the "Accept" request and the media type "application / 3gpp-partial", i.e., a Partial-File-Accept request, and the MBMS client has received a partial file having at least one byte, the MBMS client may respond with a Partial File Response as defined in TS 26.346 as follows:

[0032] Response code is set to 200OK

[0033] The Content-Type header shall be set to application / 3gpp-part.

[0034] The message body is a multipart message body and may be in the same format as the multipart / byte-range media type described in Annex A of RFC 7233. The multipart / byte-range media type consists of one or more body parts, each with its own Content-Type and Content-Range fields as a means of conveying the byte range of the partial file being returned. Each Content-Type header is set to the value of the Content-Type provided in the FDT instance for the file. Extension headers (e.g., 3gpp-Access-Position) may be added providing the byte position at which a handler assigned to the file's content-type may access the file. Values ​​may be created from mbms2015:IndependentUnitPositions if present.

[0035] In response to preventing any intermediate proxy from storing the incomplete file and serving it as another application, a cache directive should be included. Examples of such a cache directive are "Cache-Control: max-age=0" or "Cache-Control: no-cache".

[0036] If the MBMS Client receives a Partial-File-Accept Request and the MBMS Client has received a partial file without bytes (i.e. only an FDT instance describing the file metadata has been received), the MBMS Client may respond with a Partial-File-Response defined as follows:

[0037] Response code is set to 416 Request Range Not Satisfied

[0038] The Content-Type header is set to the value of the Content-Type provided in the FDT instance of the file.

[0039] Content-Range is set to bytes* / Content-Length, where Content-Length is the value of the attribute Content-Length provided for this file in the FDT instance.

[0040] TS 26.346 clause 7.9.2.3 provides an example for this.

[0041] The techniques of the present 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 third generation partnership project (3GPP) file format, and / or the multi-view video coding (MVC) file format, or other similar video file formats.

[0042] 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 the file, where the number of bytes corresponds to the received byte range. Therefore, movie fragments can be provided for HTTP streaming because the partial GET operation can obtain one or more separate movie fragments. In one movie fragment, there can be track fragments of several different tracks. In HTTP streaming, a media presentation may be a structured data collection accessible to a client. A client can request and download media data information to present a streaming service to a user.

[0043] In the example of using HTTP streaming to stream 3GPP data, there may be multiple representations of video and / or audio data of multimedia content. As explained below, different representations may correspond to different decoding characteristics (e.g., different profiles or levels of video decoding standards), different decoding standards or extensions of decoding standards (such as multi-view and / or scalable extensions), or different bit rates. A manifest of such representations may be defined in a media presentation description (MPD) data structure. Media presentation may correspond to a structured data set accessible to an HTTP streaming client device. An HTTP streaming client device may request and download media data information to present a streaming service to a user of the client device. Media presentation may be described in an MPD data structure, which may include updates to the MPD.

[0044] A media presentation may contain a sequence of one or more periods. Each period may extend to the beginning of the next period, or until the end of the media presentation if it is the last period. Each period may contain one or more representations of the same media content. A representation may be one of multiple alternatively encoded versions of audio, video, timed text, or other such data. Representations may differ by encoding type, for example, 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 piece of encoded audio or video data that corresponds to a particular period of multimedia content and is encoded in a particular way.

[0045] Representations of a particular period may be assigned to a group indicated by an attribute in the MPD, which indicates the adaptation set to which the representation belongs. Representations in the same adaptation set are generally considered to be alternatives to each other because client devices can dynamically and seamlessly switch between these representations, for example, to perform bandwidth adaptation. For example, each representation of video data for a particular period may be assigned to the same adaptation set so that any representation may be selected for decoding to present media data, such as video data or audio data, for multimedia content for the corresponding period. In some examples, the media content within a period may be represented by one representation from group 0 (if present), or by a combination of at most one representation from each non-zero group. Timing data for each representation of a period may be represented relative to the start time of the period.

[0046] A representation may include one or more fragments. Each representation may include an initialization fragment, or each fragment of a representation may be self-initializing. When presented, the initialization fragment may contain initialization information for accessing the representation. Typically, the initialization fragment does not contain media data. A fragment may be uniquely referenced by an identifier, such as a uniform resource locator (URL), a uniform resource name (URN), or a uniform resource identifier (URI). The MPD may provide an identifier for each fragment. In some examples, the MPD may also provide a byte range in the form of a range attribute, which may correspond to data of a fragment within a file accessible by a URL, URN, or URI.

[0047] For different types of media data, different representations may be selected to be retrieved substantially simultaneously. For example, a client device may select an audio representation, a video representation, and a timed text representation from which to retrieve segments. In some examples, a client device may select a particular adaptation set to perform bandwidth adaptation. That is, a 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 certain types of media (e.g., video) and directly select representations for other types of media (e.g., audio and / or timed text).

[0048] Figure 1 is a block diagram illustrating an example system 10 implementing techniques for streaming media data over a network. In an example, system 10 includes content preparation device 20, server device 60, and client device 40. Client device 40 and server device 60 are communicatively coupled via network 74, which may include the Internet. In some examples, content preparation device 20 and server device 60 may also be coupled via network 74 or another network, or may be directly communicatively coupled. In some examples, content preparation device 20 and server device 60 may include the same device.

[0049] exist Figure 1 In the example of , content preparation device 20 includes an audio source 22 and a video source 24. Audio source 22 may include, for example, a microphone that generates an electrical signal representing captured audio data to be encoded by audio encoder 26. Alternatively, audio source 22 may include a storage medium storing previously recorded audio data, an audio data generator such as a computerized synthesizer, or any other source of audio data. Video source 24 may include a 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. In all examples, content preparation device 20 need not be communicatively coupled to server device 60, but rather may store multimedia content in a separate medium that is read by server device 60.

[0050] The raw audio and video data may include analog or digital data. The analog data may be digitized before being encoded by the audio encoder 26 and / or the video encoder 28. The audio source 22 may acquire audio data from the speaking participant as the speaking participant speaks, and the video source 24 may simultaneously acquire video data of the speaking participant. In other examples, the audio source 22 may include a computer-readable storage medium including stored audio data, and the video source 24 may include a computer-readable storage medium including stored video data. In this way, the technology described in the present disclosure may be applied to live, streaming, real-time audio and video data or archived, pre-recorded audio and video data.

[0051] An audio frame corresponding to a video frame typically contains audio data captured (or generated) by audio source 22, while having video data captured (or generated) by video source 24 contained within the video frame. For example, a speaking participant typically generates audio data by speaking, audio source 22 captures the audio data, and video source 24 simultaneously captures video data of the speaking participant, i.e., at the same time as audio source 22 captures the audio data. Thus, an audio frame may correspond to one or more specific video frames in time. Accordingly, an audio frame corresponding to a video frame typically corresponds to a situation where audio data and video data are captured simultaneously, and the audio frame and video frame include audio data and video data captured simultaneously, respectively.

[0052] In some examples, audio encoder 26 may encode a timestamp in each encoded audio frame, the timestamp representing the time when the audio data of the encoded audio frame was recorded, and similarly, video encoder 28 may encode a timestamp in each encoded video frame, the timestamp representing the time when the video data of the encoded video frame was recorded. In such an example, an audio frame corresponding to a video frame may include an audio frame including a timestamp and a video frame including the same timestamp. Content preparation device 20 may include an internal clock, and audio encoder 26 and / or video encoder 28 may generate timestamps from the internal clock, or audio source 22 and video source 24 may use the internal clock to associate audio and video data with timestamps, respectively.

[0053] In some examples, audio source 22 may transmit data corresponding to the time at which audio data was recorded to audio encoder 26, and video source 24 may transmit data corresponding to the time at which video data was recorded to video encoder 28. In some examples, audio encoder 26 may encode a sequence identifier in the encoded audio data to indicate a relative temporal order of the encoded audio data, but not necessarily an absolute time at which the audio data was recorded, and similarly, video encoder 28 may also use a sequence identifier to indicate a relative temporal order of the encoded video data. Similarly, in some examples, the sequence identifier may be mapped or otherwise associated with a timestamp.

[0054] The audio encoder 26 typically produces an encoded audio data stream, while the video encoder 28 produces an encoded video data stream. Each individual data stream (whether audio or video) can be referred to as an elementary stream. An elementary stream is a single digitally decoded (possibly compressed) component of a representation. For example, the decoded video or audio portion of a representation can be an elementary stream. Before being encapsulated in a video file, the elementary stream can be converted into a packetized elementary stream (PES). In the same representation, a stream ID can be used to distinguish a PES packet belonging to one elementary stream from another. The basic data unit of an elementary stream is a packetized elementary stream (PES) packet. Therefore, the decoded video data typically corresponds to an elementary video stream. Similarly, audio data corresponds to one or more corresponding elementary streams.

[0055] Many video coding standards, such as ITU-T H.264 / AVC and the upcoming High Efficiency Video Coding (HEVC) standard, define the syntax, semantics, and decoding process for error-free bitstreams, any of which conforms to a certain profile or level. Video coding standards do not usually specify encoders, but it is the encoder's task to ensure that the generated bitstream conforms to the standard for the decoder. In the context of video coding standards, a "profile" corresponds to a subset of algorithms, features or tools and constraints that apply to them. For example, as defined in the H.264 standard, a "profile" is a subset of the entire bitstream syntax specified by the H.264 standard. A "level" corresponds to limitations on decoder resource consumption, such as decoder memory and computation, which are related to the resolution, bit rate, and block processing rate of the image. The profile can be signaled with a profile_idc (profile indicator) value, while the level can be signaled with a level_idc (level indicator) value.

[0056] For example, according to the H.264 standard, it is recognized that within the scope of the syntax specified in a given profile, it may still be necessary to have large variations in the performance of encoders and decoders, depending on the values ​​of syntax elements within the bitstream, such as the specified size of the decoded image. According to the H.264 standard, it is further recognized that in many applications, it is neither practical nor economical to implement a decoder that can handle all hypothetical uses of the syntax in a particular profile. Therefore, the H.264 standard defines a "level" as a set of specified constraints imposed on the values ​​of syntax elements in the bitstream. These constraints may be simple restrictions on values. Alternatively, these constraints may take the form of constraints on arithmetic combinations of values ​​(e.g., image width multiplied by image height multiplied by the number of images decoded per second). The H.264 standard further provides that separate implementations may support different levels for each supported profile.

[0057] A decoder that conforms to a profile generally supports all features defined in the profile. For example, as a decoding feature, the baseline profile of H.264 / AVC does not support B-picture decoding, but other profiles of H.264 / AVC support B-picture decoding. A decoder that conforms to a level should be able to decode any bitstream that does not require resources beyond the limits defined in the level. The definition of profiles and levels may help with interpretability. 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 restrictions on the number of macroblocks that need to be processed, the decoded picture buffer (DPB) size, the decoded picture buffer (CPB) size, the vertical motion vector range, the maximum number of motion vectors per two consecutive MBs, and whether a B block can have a sub-macroblock partition of less than 8x8 pixels. In this way, the decoder can determine whether the decoder can correctly decode the bitstream.

[0058] exist Figure 1 In the example of , encapsulation unit 30 of content preparation device 20 receives an elementary stream including decoded video data from video encoder 28 and an elementary stream including decoded 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 encoded data. In other examples, video encoder 28 and audio encoder 26 may each interface with a packetizer for forming PES packets from the encoded data. In other examples, encapsulation unit 30 may include a packetizer for forming PES packets from the encoded audio and video data.

[0059] The video encoder 28 may encode the video data of the multimedia content in various ways to produce different representations of the multimedia content at various bit rates and with various characteristics, such as pixel resolution, frame rate, compliance with various decoding standards, compliance with various profiles and / or profile levels of various decoding standards, representations with one or more views (e.g., for two-dimensional or three-dimensional playback), or other such characteristics. Representations as used in the present disclosure may include audio data, video data, text data (e.g., for closed captioning), or one of other such data. Representations may include elementary streams, such as audio elementary streams or video elementary streams. Each PES packet may include a stream_id that identifies the elementary stream to which the PES packet belongs. Encapsulation unit 30 is responsible for assembling elementary streams into video files (e.g., segments) of various representations.

[0060] The encapsulation unit 30 receives PES packets of the elementary streams represented from the audio encoder 26 and the video encoder 28, and forms corresponding network abstraction layer (NAL) units from the PES packets. The decoded video fragments can be organized into NAL units to provide a "network-friendly" video representation to address applications such as video telephony, storage, broadcasting, or streaming. NAL units can be divided into video coding layer (VCL) NAL units and non-VCL NAL units. The VCL unit may contain a 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 decoded image in a time instance that is typically presented as a main decoded image may be included in an access unit, which may include one or more NAL units.

[0061] Non-VCL NAL units may include parameter set NAL units and SEI NAL units, among others. Parameter sets may contain sequence-level header information (in a sequence parameter set (SPS)) and infrequently changing picture-level header information (in a picture parameter set (PPS)). Using parameter sets (e.g., PPS and SPS), infrequently changing information does not need to be repeated for each sequence or picture; therefore, decoding efficiency may be improved. In addition, the use of parameter sets may enable out-of-band transmission of important header information, avoiding the need for redundant transmission for error recovery. In the out-of-band transmission example, parameter set NAL units may be sent on a different channel than other NAL units (such as SEI NAL units).

[0062] Supplemental enhancement information (SEI) may contain information that is not necessary for decoding coded image samples from VCL NAL units, but may be helpful for 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 are therefore not always mandatory for standard-compliant decoder implementations. 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 scalability information SEI messages in the SVC example and view scalability information SEI messages in MVC. These example SEI messages may convey information about, for example, the extraction of operation points and the characteristics of the operation points. In addition, encapsulation unit 30 may form a manifest file, such as a media presentation descriptor (MPD) that describes the characteristics of the representation. Encapsulation unit 30 may format the MPD according to extensible markup language (XML).

[0063] The encapsulation unit 30 may provide data for one or more representations of the multimedia content together with a manifest file (e.g., an MPD) to an output interface 32. The output interface 32 may include a network interface or an interface for writing to a storage medium, such as a universal serial bus (USB) interface, a CD or DVD recorder or burner, an interface for magnetic or flash storage media, or other interfaces for storing or sending media data. The encapsulation unit 30 may provide data for each representation of the multimedia content to the output interface 32, which may transmit the data to the server device 60 via a network transmission or storage medium. Figure 1 In the example of , the server device 60 includes a storage medium 62 storing various multimedia contents 64, each of which includes a respective manifest file 66 and one or more representations 68A-68N (representations 68). In some examples, the output interface 32 may also transmit data directly to the network 74.

[0064] In some examples, representations 68 may be divided into adaptation sets. That is, various subsets of representations 68 may include corresponding sets of common characteristics, such as codecs, profiles and levels, resolutions, number of views, file formats of segments, text type information that may identify a language or other characteristics of text to be represented for display, and / or audio data to be decoded and presented, for example by speakers, camera angle information that may describe a camera angle or real-world camera perspective for a scene represented in the adaptation set, rating information that describes content suitable for a particular audience, and the like.

[0065] The manifest file 66 may include data indicating a subset of representations 68 corresponding to a particular adaptation set and the common characteristics of the adaptation set. The manifest file 66 may also include data representing individual characteristics, such as bit rate, for the individual representations of the adaptation set. In this way, the adaptation set may provide simplified network bandwidth adaptation. The representations in the adaptation set may be indicated using a sub-element of the adaptation set element of the manifest file 66.

[0066] The server device 60 includes a request processing unit 70 and a network interface 72. In some examples, the server device 60 may include multiple network interfaces. In addition, any or all features of the 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, an intermediate device of the content delivery network may cache data of the multimedia content 64 and include components that are substantially consistent with the components of the server device 60. Typically, the network interface 72 is configured to transmit and receive data via the network 74.

[0067] The request processing unit 70 is configured to receive a network request for data from 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 R. Fielding et al., Network Working Group, IETF, RFC 2616, "Hypertext Transfer Protocol - HTTP / 1.1", June 1999. That is, the request processing unit 70 may be configured to receive an HTTP GET or partial GET request, and provide data of the multimedia content 64 in response to the request. The request may specify a fragment of one of the representations 68, for example, using a URL of the fragment. In some examples, the request may also specify one or more byte ranges of the fragment, thus comprising a partial GET request. The request processing unit 70 may also be configured to service an HTTP HEAD request to provide header data of one of the fragments of the representations 68. In any case, the request processing unit 70 may be configured to process the request to provide the requested data to the requesting device, such as the client device 40.

[0068] Additionally or alternatively, the request processing unit 70 can be configured to deliver the media data via a broadcast or multicast protocol, such as eMBMS. The content preparation device 20 can create DASH segments and / or sub-segments in substantially the same manner as described, but the server device 60 can deliver the segments or sub-segments using eMBMS or another broadcast or multicast network transmission protocol. For example, the request processing unit 70 can be configured to receive a multicast group join request from the client device 40. That is, the server device 60 can notify the client devices associated with the particular media content (e.g., the broadcast of the live event) of the Internet Protocol (IP) address associated with the multicast group, including the client device 40. The client device 40 can then submit a request to join the multicast group. The request can be propagated throughout the network 74 (e.g., the routers constituting the network 74), so that the routers direct traffic to the IP address associated with the multicast group to the subscribing client devices, such as the client device 40.

[0069] like Figure 1 As shown in the example of , multimedia content 64 includes a manifest file 66, which may correspond to a media presentation description (MPD). Manifest file 66 may contain descriptions of different alternative representations 68 (e.g., video services with different qualities), and the descriptions may include, for example, codec information, profile values, level values, bit rates, and other descriptive characteristics of representation 68. Client device 40 may retrieve the MPD of the media presentation to determine how to access segments of representation 68.

[0070] In particular, the retrieval unit 52 may retrieve configuration data (not shown) of the client device 40 to determine the decoding capabilities of the video decoder 48 and the rendering capabilities of the video output 44. The configuration data may also include any or all of a language preference selected by a user of the client device 40, one or more camera viewing angles corresponding to a depth preference set by a user of the client device 40, and / or a rating preference selected by a user of the client device 40. The retrieval unit 52 may include, for example, a web browser or media client configured to submit HTTP GET and partial GET requests. The retrieval unit 52 may correspond to software instructions executed by one or more processors or processing units (not shown) of the client device 40. In some examples, all or part of the functionality described with respect to the retrieval unit 52 may be implemented in hardware, or a combination of hardware and software, and / or firmware, where the necessary hardware may be provided to execute the instructions of the software or firmware.

[0071] Retrieval unit 52 may compare the decoding and rendering capabilities of client device 40 with characteristics of representation 68 indicated by information of manifest file 66. Retrieval unit 52 may first retrieve at least a portion of manifest file 66 to determine characteristics of representation 68. For example, retrieval unit 52 may request a portion of manifest file 66 that describes characteristics of one or more adaptation sets. Retrieval unit 52 may select a subset of representation 68 (e.g., an adaptation set), wherein the subset has characteristics that can be satisfied by the decoding and rendering capabilities of client device 40. Retrieval unit 52 may then determine the bitrate of the representations in the adaptation set, determine the amount of network bandwidth currently available, and retrieve a segment from one of the representations having a bitrate that can be satisfied by the network bandwidth.

[0072] In general, a higher bit rate representation may produce a higher quality video playback, while a lower bit rate representation may provide adequate quality video playback when the available network bandwidth is reduced. Thus, when the available network bandwidth is relatively high, the retrieval unit 52 may retrieve data from a relatively high bit rate representation, and when the available network bandwidth is low, the retrieval unit 52 may retrieve data from a relatively low bit rate representation. In this way, the client device 40 may stream multimedia data over the network 74 while also adapting to the changing network bandwidth availability of the network 74.

[0073] Additionally or alternatively, the 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, the retrieval unit 52 may submit a request to join a multicast network group associated with a particular media content. After joining the multicast group, the retrieval unit 52 may receive data of the multicast group without issuing further requests to the server device 60 or the content preparation device 20. When the data of the multicast group is no longer needed, the retrieval unit 52 may submit a request to leave the multicast group, for example, to stop playing or change the channel to a different multicast group.

[0074] The network interface 54 may receive data for the segments of the selected representation and provide it to the retrieval unit 52, which in turn may provide the segments to the decapsulation unit 50. The decapsulation unit 50 may decapsulate the elements of the video file into elemental PES streams, depacketize the PES streams to retrieve the encoded data, and transmit the encoded data to the audio decoder 46 or the 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 header of the stream. The audio decoder 46 decodes the encoded audio data and transmits the decoded audio data to the audio output 42, while the video decoder 48 decodes the encoded video data and transmits the decoded video data, which may include multiple views of the stream, to the video output 44.

[0075] Each of the video encoder 28, video decoder 48, audio encoder 26, audio decoder 46, encapsulation unit 30, retrieval unit 52, and decapsulation unit 50 may be implemented as any of a variety of suitable processing circuits, such as one or more microprocessors, digital signal processors (DSPs), application specific integrated circuits (ASICs), field programmable gate arrays (FPGAs), discrete logic circuits, software, hardware, firmware, or any combination thereof, as applicable. Each of the video encoder 28 and video decoder 48 may be included in one or more encoders or decoders, either of which may be integrated as part of a combined video encoder / decoder (CODEC). Similarly, each of the audio encoder 26 and audio decoder 46 may be included in one or more encoders or decoders, either of which may be integrated as part of a combined CODEC. An apparatus including the video encoder 28, video decoder 48, audio encoder 26, audio decoder 46, encapsulation unit 30, retrieval unit 52, and / or decapsulation unit 50 may include an integrated circuit, a microprocessor, and / or a wireless communication device, such as a cellular phone.

[0076] Client device 40, server device 60, and / or content preparation device 20 may all be configured to operate according to the techniques of this disclosure. For purposes 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 perform these techniques instead of (or in addition to) server device 60.

[0077] Encapsulation unit 30 may form NAL units, which include a header identifying the program to which the NAL unit belongs and a payload, such as audio data, video data, or data describing a transport or program stream corresponding to the NAL unit. For example, in H.264 / AVC, a NAL unit includes a 1-byte header and payloads of varying sizes. NAL units including video data in their payloads may include video data at various levels of granularity. For example, a NAL unit may include a block of video data, multiple blocks, a strip of video data, or an entire image of video data. Encapsulation unit 30 may receive encoded video data in the form of PES packets of elementary streams from video encoder 28. Encapsulation unit 30 may associate each elementary stream with a corresponding program.

[0078] The encapsulation unit 30 may also assemble an access unit from a plurality of NAL units. Typically, an access unit may include one or more NAL units representing a frame of video data, and audio data of a corresponding frame when such audio data is available. An access unit typically includes all NAL units of an output time instance, such as all audio and video data of a 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, specific frames of all views of the same access unit (same time instance) may be rendered simultaneously. In one example, an access unit may include a decoded image in a time instance, which may be presented as a main decoded image.

[0079] Thus, an access unit may include all audio and video frames of a common time instance, for example, all views corresponding to time X. The present disclosure also refers to the coded images of a particular view as "view components". That is, a view component may include coded images (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 access units is not necessarily the same as the output or display order.

[0080] The media presentation may include a media presentation description (MPD), which may contain descriptions of different alternative representations (e.g., video services with different qualities), and the description may include, for example, codec information, profile values, and level values. The MPD is an example of a manifest file, such as manifest file 66. Client device 40 may retrieve the MPD of the media presentation to determine how to access the movie fragments of the various representations. The movie fragments may be located in a movie fragment box (moof box) of a video file.

[0081] Manifest file 66 (which may include, for example, an MPD) may notify the availability of segments of representation 68. That is, the MPD may include information indicating a wall clock time at which a first segment of one of representations 68 becomes available, and information indicating durations of segments within representation 68. In this way, retrieval unit 52 of client device 40 may determine when each segment is available based on the start time and durations of multiple segments preceding the particular segment.

[0082] After the encapsulation unit 30 has assembled the NAL units and / or access units into a video file based on the received data, the encapsulation unit 30 transmits the video file to the output interface 32 for output. In some examples, the encapsulation unit 30 may store the video file locally or transmit the video file to a remote server via the output interface 32, rather than directly transmitting the video file to the client device 40. The output interface 32 may include, for example, a transmitter, a transceiver, a device for writing data to a computer-readable medium, such as an optical drive, a magnetic media drive (e.g., a floppy disk 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 a transmission signal, a magnetic medium, an optical medium, a memory, a flash drive, or other computer-readable medium.

[0083] The network interface 54 may receive NAL units or access units via the network 74 and provide the NAL units or access units to the decapsulation unit 50 via the retrieval unit 52. The decapsulation unit 50 may decapsulate the elements of the video file into elemental PES streams, depacketize the PES streams to retrieve the encoded data, and transmit the encoded data to the audio decoder 46 or the 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 header of the stream. The audio decoder 46 decodes the encoded audio data and transmits the decoded audio data to the audio output 42, while the video decoder 48 decodes the encoded video data and transmits the decoded video data, which may include multiple views of the stream, to the video output 44.

[0084] According to the technology of the present disclosure, server device 60 (or content preparation device 20) can signal a packet loss detection mechanism to client device 40. For example, server device 60 can signal the packet loss detection mechanism via a control channel between server device 60 and client device 40. The packet loss detection mechanism may include one or more of the following situations: fragments are transmitted in chunks, transport object identifiers (TOIs) are continuous, or the last packet of an object assigned to a TOI has a specific flag set in the header of the last packet, a base URL, a maximum delay, or a synchronization point in a file delivery header.

[0085] Client device 40 may then execute a signaled packet loss detection mechanism to determine whether packets have been lost in a broadcast or multicast stream from server device 60. In response to determining that one or more packets have been lost, retrieval unit 52 may form one or more byte range requests (i.e., HTTP partial Get requests) specifying byte ranges of segments of media data that include the lost packets. Retrieval unit 52 may then submit these byte range requests to server device 60 to attempt to retrieve the lost media data via a unicast protocol (e.g., HTTP).

[0086] In some examples, the server device 60 may signal an inter-packet timeout value. The client device 40 (and specifically, the retrieval unit 52) ​​may use the inter-packet timeout value to determine whether a packet has been lost, for example, if a packet has not been received within the inter-packet timeout interval since a previous packet of the media stream was received. The inter-packet timeout value may correspond to a nominal Common Media Application Format (CMAF) block duration. The server device 60 may signal the inter-packet timeout value in, for example, a file delivery table (FDT), an enhanced FDT (eFDT), or in control plane service or session metadata. Thus, the client device 40 may extract the inter-packet timeout value from the data.

[0087] Regardless of whether the lost media data is received, retrieval unit 52 may form appropriate media objects to be delivered to decapsulation unit 50, and ultimately to audio decoder 46 and / or video decoder 48. Appropriate media objects may generally be parsed and decoded by decapsulation unit 50, audio decoder 46, and video decoder 48. Appropriate media objects may still be missing some media data of the lost packets, but may still be parsable and decodable.

[0088] Figure 2 is shown in more detail Figure 1 FIG. 5 is a block diagram of an example set of components of a retrieval unit 52 of FIG. 5 . In the example, the retrieval unit 52 includes an eMBMS middleware unit 100 , a DASH client 110 , and a media application 112 .

[0089] In the example, the eMBMS middleware unit 100 further includes an eMBMS receiving unit 106, a cache 104, and a proxy server unit 102. In the example, the eMBMS receiving unit 106 is configured to receive data via eMBMS, for example, according to FLUTE. That is, the eMBMS receiving unit 106 may receive files via broadcast from a server device 60, which may act as a broadcast / multicast service center (BM-SC), for example.

[0090] When the eMBMS middleware unit 100 receives file data, the eMBMS middleware unit may store the received data in the cache 104. The cache 104 may include a computer-readable storage medium, such as a flash memory, a hard disk, a RAM, or any other suitable storage medium.

[0091] 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 notify the number of times the segments in the MPD file are available, as well as hyperlinks from which the segments can be retrieved. These hyperlinks may include a local host address prefix corresponding to the client device 40 (e.g., 127.0.0.1 for IPv4). In this way, the DASH client 110 may request the segments from the proxy server unit 102 using an HTTP GET or partial GET request. For example, for a segment available from the link http: / / 127.0.0.1 / rep1 / seg3, the DASH client 110 may construct an HTTP GET request that includes a request for http: / / 127.0.0.1 / rep1 / seg3 and submit the request to the proxy server unit 102. The proxy server unit 102 may retrieve the requested data from the cache 104 and provide the data to the DASH client 110 in response to such a request.

[0092] Figure 3 1 is a conceptual diagram illustrating elements of example multimedia content 120. Multimedia content 120 may correspond to multimedia content 64 ( Figure 1 ), or another multimedia content stored in the storage medium 62. Figure 3In the example of , multimedia content 120 includes a media presentation description (MPD) 122 and multiple representations 124A-124N (representations 124). Representation 124A includes optional header data 126 and fragments 128A-128N (fragments 128), while representation 124N includes optional header data 130 and fragments 132A-132N (fragments 132). For convenience, the letter N is used to designate the last movie fragment in each of representations 124. In some examples, there may be different numbers of movie fragments between representations 124.

[0093] MPD 122 may include a data structure separate from representation 124. MPD 122 may correspond to Figure 1 Similarly, representation 124 may correspond to Figure 1 In general, the MPD 122 may include data generally describing characteristics of the representation 124, such as coding and rendering characteristics, adaptation sets, a profile to which the MPD 122 corresponds, text type information, camera angle information, rating information, trick mode information (e.g., information indicating that a representation includes a temporal subsequence), and / or information for retrieving remote periods (e.g., for inserting targeted advertisements into media content during playback).

[0094] The header data 126, when present, may describe characteristics of the segment 128, such as the temporal location of a random access point (RAP, also referred to as a stream access point (SAP)) that the segment 128 includes, a byte offset within the segment 128 to the random access point, a uniform resource locator (URL) of the segment 128, or other aspects of the segment 128. The header data 130, when present, may describe similar characteristics of the segment 132. Additionally or alternatively, these characteristics may be included entirely in the MPD 122.

[0095] The segments 128, 132 include one or more decoded video samples, each of which may include a frame or slice of video data. Each of the decoded video samples of the segments 128 may have similar characteristics, such as height, width, and bandwidth requirements. Such characteristics may be described by data from the MPD 122, although such data is not described in the MPD 122. Figure 3 The MPD 122 may include features as described in the 3GPP specification, with the addition of any or all of the signaling information described in this disclosure.

[0096] Each of the segments 128, 132 can be associated with a unique uniform resource locator (URL). Therefore, each of the segments 128, 132 can be independently retrieved using a streaming network protocol such as DASH. In this way, a destination device such as the client device 40 can use an HTTP GET request to retrieve a segment 128 or 132. In some examples, the client device 40 can use an HTTP partial GET request to retrieve a specific byte range of the segment 128 or 132.

[0097] Figure 4 is a block diagram illustrating elements of an example video file 150, which may correspond to a segment of a representation, such as Figure 3 Each of the segments 128, 132 may include a substantially Figure 4 The data is arranged as shown in the example of the video file 150. The video file 150 can be considered to encapsulate a segment. As described above, a video file according to the ISO base media file format and its extensions stores data in a series of objects, called "boxes". Figure 4 In the example of , the video file 150 includes a file type (FTYP) box 152, a movie (MOOV) box 154, a segment index (sidx) box 162, a movie segment (MOOF) box 164, and a movie segment random access (MFRA) box 166. Figure 4 The examples represent video files, but it should be understood that other media files may include other types of media data (e.g., audio data, timed text data, etc.), where the other types of media data have a similar structure to the data of video file 150 according to the ISO base media file format and its extensions.

[0098] The file type (FTYP) box 152 generally describes the file type of the video file 150. The file type box 152 may include data identifying specifications for optimal use that describe 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.

[0099] 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 an MPD is to be updated, and information for updating the MPD, where the MPD corresponds to a representation including video file 150. For example, the MPD update box may provide a URI or URL of a resource to be used to update the MPD. As another example, the MPD update box may include data for updating the MPD. In some examples, the MPD update box may be immediately followed by a segment type (STYP) box (not shown) for video file 150, where the STYP box may define the segment type of video file 150.

[0100] exist Figure 4 In the example of , the MOOV box 154 includes a movie header (MVHD) box 156, a track (TRAK) box 158, and one or more movie extension (MVEX) boxes 160. In general, the MVHD box 156 may describe general characteristics of the video file 150. For example, the MVHD box 156 may include data describing the initial creation time of the video file 150, the last modification time of the video file 150, the timeline of the video file 150, the playback duration of the video file 150, or other data generally describing the video file 150.

[0101] The TRAK box 158 may include data for a track of the video file 150. The TRAK box 158 may include a track header (TKHD) box that describes characteristics of the track corresponding to the TRAK box 158. In some examples, the TRAK box 158 may include a decoded video image, while in other examples, the decoded video image of the track may be included in a movie fragment 164, which may be referenced by the data of the TRAK box 158 and / or the sidx box 162.

[0102] In some examples, the video file 150 may include more than one track. Therefore, the MOOV box 154 may include a number of TRAK boxes, the number of which is equal to the number of tracks in the video file 150. The TRAK box 158 may describe the characteristics of the corresponding track of the video file 150. For example, the TRAK box 158 may describe the time and / or space information of the corresponding track. Figure 3 ) When a parameter set track is included in a video file such as video file 150, a TRAK box similar to TRAK box 158 of MOOV box 154 may describe characteristics of the parameter set track. Encapsulation unit 30 may signal the presence of a sequence level SEI message in the parameter set track within the TRAK box describing the parameter set track.

[0103] The MVEX box 160 may describe characteristics of the corresponding movie fragment 164, e.g., to signal that the video file 150 includes the movie fragment 164, if any, in addition to the video data included in the MOOV box 154. In the context of streaming video data, decoded video images may be included in the movie fragment 164 instead of the MOOV box 154. Thus, all decoded video samples may be included in the movie fragment 164 instead of the MOOV box 154.

[0104] The MOOV box 154 may include a number of MVEX boxes 160, the number of which is equal to the number of movie fragments 164 in the video file 150. Each of the MVEX boxes 160 may describe characteristics of a corresponding one of the movie fragments 164. For example, each MVEX box may include a Movie Extension Header Box (MEHD) box that describes the time duration of a corresponding one of the movie fragments 164.

[0105] As described above, the encapsulation unit 30 may store the sequence data set in a video sample that does not include the actual decoded video data. The video sample may generally correspond to an access unit, which is a representation of a decoded picture at a specific time instance. In the context of AVC, a decoded picture includes one or more VCL NAL units that contain information for all pixels that construct the access unit and other related non-VCL NAL units, such as SEI messages. Therefore, the encapsulation unit 30 may include the sequence data set in one of the movie fragments 164, and the sequence data set may include a sequence-level SEI message. The encapsulation unit 30 may further signal the presence of the sequence data set and / or sequence-level SEI message, such as being presented in one of the movie fragments 164 in one of the MVEX boxes 160 corresponding to one of the movie fragments 164.

[0106] SIDX box 162 is an optional element of video file 150. That is, a video file conforming to the 3GPP file format or other such file formats does not necessarily include SIDX box 162. According to an example of the 3GPP file format, a SIDX box may be used to identify a sub-segment of a fragment (e.g., a fragment contained in video file 150). The 3GPP file format defines a sub-segment as "a self-contained collection of one or more consecutive movie fragment boxes with corresponding media data boxes, and a media data box containing data referenced by a movie fragment box must follow the movie fragment box and precede the next movie fragment box containing information for the same track." The 3GPP file format also states that the SIDX box "contains a sequence of references to sub-segments of the (sub)fragment recorded by the box. The referenced sub-segments are consecutive in presentation time. Similarly, the bytes referenced by the fragment index box are always consecutive within a fragment. The reference size gives a count of the number of bytes in the referenced material."

[0107] The SIDX block 162 generally provides information representative of one or more sub-segments of a segment included in the video file 150. For example, such information may include the playback time at which the sub-segment begins and / or ends, the byte offset of the sub-segment, whether the sub-segment includes (e.g., starts at) a streaming 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 the sub-segment (in terms of playback time and / or byte offset), etc.

[0108] The movie fragments 164 may include one or more decoded video images. In some examples, the movie fragments 164 may include one or more groups of pictures (GOPs), each of which may include multiple decoded video images, such as frames or pictures. In addition, as described above, in some examples, the movie fragments 164 may include a sequence data set. Each of the movie fragments 164 may include a movie fragment header box (MFHD, Figure 4 MFHD box may describe characteristics of the corresponding movie fragment, such as a sequence number of the movie fragment. The movie fragments 164 may be included in the video file 150 in the order of the sequence number.

[0109] MFRA box 166 may describe random access points within movie fragments 164 of video file 150. This may help perform trick modes, such as performing seeks to specific time locations (i.e., play times) within the fragments encapsulated by video file 150. In some examples, MFRA box 166 is generally optional and need not be included in the video file. Likewise, client devices such as client device 40 do not necessarily need to reference MFRA box 166 to properly decode and display video data of video file 150. MFRA box 166 may include a plurality of track fragment random access (TFRA) boxes (not shown), the number of which is equal to the number of tracks of video file 150, or in some examples, the number of media tracks (e.g., non-hint tracks) of video file 150.

[0110] In some examples, the movie fragment 164 may include one or more streaming 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 SAP. Therefore, a temporal subsequence of the video file 150 may be formed by the SAPs of the video file 150. The temporal subsequence may also include other images, such as P frames and / or B frames that depend on the SAP. The frames and / or slices of the temporal subsequence may be arranged within the fragment so that the frames / slices of the temporal subsequence that depend on other frames / slices of the subsequence may be properly decoded. For example, in a hierarchical arrangement of data, data for predicting other data may also be included in the temporal subsequence.

[0111] Figure 5 is a conceptual diagram illustrating an example system including a transmitter and a receiver according to techniques of this disclosure. Figure 5 The transmitter generally includes a media encoder 200, a CMAF / file format (FF) packager 202, a DASH packager 204, a ROUTE transmitter 206, and a CDN source server 208. The media encoder 200 encodes media data, such as audio or video data. The media encoder 200 may correspond to Figure 1 The audio encoder 26 or the video encoder 28 of the CMAF / FF packager 202 and the DASH packager 204 may correspond to Figure 1 The ROUTE transmitter 206 and the CDN source server 208 may correspond to Figure 1 The request processing unit 70 and the server device 60.

[0112] Figure 5 The receiver of the ROUTE receiver generally includes a ROUTE receiver 210, a DASH client 212, a CMAF / FF parser 214, and a media decoder 216. The ROUTE receiver 210 and the DASH client 212 may correspond to Figure 1 The retrieval unit 52. The CMAF / FF parser 214 may correspond to Figure 1 The decapsulation unit 50. The media decoder 216 may correspond to one or both of the audio decoder 46 and the video decoder 48.

[0113] The media encoder 200 provides the encoded media data to a CMAF / FF packager 202, which formats the encoded media data into files according to CMAF and a specific file format, such as ISO BMFF or an extension thereof. The CMAF / FF packager 202 provides these files (e.g., chunks) to a DASH packager 204, which aggregates the files / chunks into DASH fragments. The DASH packager 204 can also form a manifest file, such as an MPD, including data describing the files / chunks / fragments. In addition, according to the technology of the present disclosure, the ROUTE transmitter 206 and / or the CDN origin server 208 can signal one or more packet loss detection mechanisms for use by, for example, the ROUTE receiver 210 and / or the DASH client 212 to detect packet loss.

[0114] The DASH packager 204 provides the segments along with the MPD to the ROUTE transmitter 206 and the CDN origin server 208. The ROUTE transmitter 206 and the CDN origin server 208 may correspond to Figure 1 Server device 60 or Figure 5CDN 220. Generally, in an example, ROUTE transmitter 206 can transmit the media data to ROUTE receiver 210 according to ROUTE. In other examples, other file-based delivery protocols can be used for broadcast or multicast, such as FLUTE. Additionally or alternatively, CDN origin server 208 can transmit the media data to ROUTE receiver 210 and / or directly to DASH client 212, for example, according to HTTP.

[0115] ROUTE receiver 210 may be implemented in middleware such as Figure 2 The ROUTE receiver 210 may buffer the received media data, for example, Figure 2 The DASH client 212 (which may correspond to Figure 2 The DASH client 110 of the ROUTE receiver 210 can use HTTP to retrieve the cached media data. Alternatively, the DASH client 212 can retrieve the media data directly from the CDN origin server 208 according to HTTP, as described above.

[0116] Furthermore, in accordance with the techniques of this disclosure, for example, the ROUTE receiver 210 may use one or more signaling packet loss detection mechanisms to determine that packet loss has occurred, for example, during a broadcast or multicast streaming session of media data. In response, the ROUTE receiver 210 may provide data to the DASH client 212 indicating that packet loss has occurred. Additionally or alternatively, the DASH client 212 may use one or more of the signaling packet loss detection mechanisms to determine that packet loss has occurred. In either case, the DASH client 212 may form a byte range request, for example, using an HTTP partial Get request, to retrieve media data corresponding to the media data included in the lost packets from the CDN origin server 208. In this way, Figure 5 A receiver may typically receive media data via broadcast or multicast, but when part of the media data is lost, the DASH client 212 may use unicast (eg, HTTP) to retrieve the lost media data.

[0117] This disclosure focuses primarily on the signaling properties of ROUTE transmissions regarding how data is distributed, and the interface from the ROUTE receiver 210 to the DASH client 212 in situations where media data may be partially lost.

[0118] The current Digital Video Broadcasting (DVB) Adaptive Bitrate (ABR) specification supports multicast delivery in low-latency mode, but the above-mentioned traditional mechanisms are not suitable for this low-latency mode, which leads to their limitations. These limitations may cause unwelcome playback stops, especially in the case of low-latency streams.

[0119]

[0120] The present disclosure recognizes certain problems that may arise with conventional techniques, as described below.

[0121] The mechanisms in sections 1.3 and 1.4 of the DVB ABR specification can only detect losses at the earliest after the nominal reception duration of the entire delivered object by the receiver. For example, for a multicast DASH representation with a nominal segment duration of 2 seconds, detection will occur at the earliest two seconds after the start of reception of the object. This may result in very long playback pauses due to packet loss.

[0122] The mechanism of clause 1.2 of the DVB ABR specification may only work after the subsequent packets (the packets received after the lost packet) have been received. Such reception is usually delayed for a long time, for example, in bad channel conditions where packet reception suddenly stops for a long time. In this case, the receiver defaults to the mechanisms of clauses 1.3 and 1.4.

[0123] The mechanism in clause 1.2 of the DVB ABR specification is also not robust to out-of-order packet delivery.

[0124] The mechanism in clause 1.5 of the DVB ABR specification is only defined for full object reception and not for low-delay cases.

[0125] Thus, in general, according to clause 1.3 of the DVB ABR specification, using conventional mechanisms, the earliest packet loss detection is typically done after a time on the order of the nominal DASH segment duration.

[0126] This disclosure describes techniques that can solve the above problems. Transmitters and receivers, such as source device 60 and client device 40, can signal data on a control channel as follows:

[0127] 1. Signaling in the control channel that the segments are transmitted in blocks. Once a block is completed at the transmitter, the transmission begins. This means that the transmission signaling can be abstracted to indicate that the interval between the transmission of two packets is at most a certain duration (this signal can be added to the setup when determining the block duration). The transmission interval can be at most the block duration.

[0128] 2. Signaling in the control channel that the TOI is continuous.

[0129] 3. Signaling on the control channel that the last packet of the object allocated to the TOI has a specific flag set in the packet header.

[0130] 4. Signaling a template base URL in the control channel, which generates a URL based on the TOI of the received FLUTE / ROUTE object, where the same object can be requested via HTTP unicast.

[0131] 5. Signaling the maximum delay of packets until they are provided to the application client, even if they are partial.

[0132] 6. ISO BMFF synchronization points, ie block boundaries, are signaled at byte range level on the ROUTE header.

[0133] Figure 1 The client device 40, ROUTE receiver 210, or other receiver may use the signaling information to:

[0134] 1. The loss of one or several packets is detected early in delivery by one or more of the signaling mechanisms.

[0135] 2. Use the information in the ROUTE / FLUTE header, i.e. TOI and start_offset, to generate appropriate byte range requests for the missing data.

[0136] 3. Provide timely notification to application clients (e.g. Figure 2 The DASH client 110 or media application 112) delivers the appropriate object.

[0137] a. The gateway interrupts the transmission with, for example, an HTTP 504 code, and the DASH player can handle such events. Or,

[0138] b. A response is delivered even if it is partial. A partial response includes the byte range of the correctly received object and the resynchronization points at the byte stream level.

[0139] Applications (e.g. Figure 2 The media application 112) can utilize the information to render the best quality by using all available information received in a timely manner. The application can accept partial data with resynchronization points.

[0140] The block duration signaling details may include the following. Early detection of transmission packet loss may be achieved by signaling an inter-packet timeout. Such a timeout may be set based on the nominal CMAF block duration of the stream being transmitted. Signaling may be done in the multicast transport packet header, or in the multicast object metadata (FDT / eFDT), or in the control plane (service / session metadata). Signaling may take into account the maximum expected packet arrival jitter. Where the signaling does not take this into account, a receiver implementation may use the packet reception jitter it experiences. The receiver (e.g., client device 40) may then request data via unicast when the inter-packet timeout described above expires to ensure that playback is minimally stalled. Since the receiver only determines the start of the byte range it needs to request, rather than how much data it needs, it may obtain data via HTTP chunking mode, in which it may request a sizeable amount of data (e.g., the nominal segment size) and may cancel reception after multicast reception is resumed.

[0141] The solution can typically detect packet loss within a duration on the order of a CMAF chunk duration, e.g., 100-200 milliseconds, whereas prior art may require approximately one to two seconds to make such a detection. Such early detection can trigger early repair attempts, thereby minimizing the duration of the outage in such cases.

[0142] In some examples, the DASH client 212 may make byte range requests to repair transport packet losses. After detecting packet loss as described above, the DASH client 212 may form a unicast byte range request. Byte range determination of missing data is discussed above. The mechanism for retrieving the address of the repair data is documented in DVB Working Draft No. 9, TM-IPI3626r4: ABR Multicast Task Force—Unicast Repair Draft Specification available at www.dvb.org / resources / restricted / members / documents / TM-IPI / ABR%20Multicast / TM-IPI3626r4_ABR-Multicast-taskforce---Unicast-repair-draft-specification.docx.

[0143] The DASH client 212 and / or ROUTE receiver 210 may also handle packet repair failures. Ultimately, packet repair attempts may fail or not complete in a timely manner. In this case, the multicast gateway may signal this problem to the DASH client 212. There are two possibilities for resolving this situation:

[0144] 1. The gateway interrupts the transmission with, for example, an HTTP 504 code, and the DASH player can handle such events.

[0145] 2. Additionally or alternatively, a response is transmitted even if a packet is partially received using the partial file signaling mechanism described above. According to this mechanism, the application indicates its ability to accept partial files in its HTTP GET request. The partial response includes the byte range of the correctly received object and the resynchronization point at the byte stream level.

[0146] The DASH client 212 and / or the ROUTE receiver 210 may also handle loss of transport objects. One mechanism for handling complete loss of one or more transport objects and their associated metadata (e.g., FDT) relies on the availability of a unicast connection. The multicast gateway may be configured as an HTTP reverse proxy and may use the unicast connection to obtain the lost objects, e.g., when a player makes a request for the object. The gateway may restore the same content via unicast using the URL of the requested object and signaling of the unicast content location as described above.

[0147] Figure 6 is a flowchart illustrating an example method according to the technology of the present disclosure. Figure 1 The server device 60 and the client device 40 are explained Figure 6 Other devices may be configured to perform methods or similar methods, such as Figure 5 transmitter and receiver equipment.

[0148] Initially, server device 60 signals one or more packet loss detection mechanisms (250). These mechanisms may include one or more of the following: fragments are transmitted in chunks, transport object identifiers (TOIs) are contiguous, or the last packet of an object assigned to a TOI has a specific flag set in the header of the last packet, a base URL, a maximum delay, or a synchronization point in a file delivery header. Client device 40 may also receive data representing the signaling of the packet loss detection mechanism (252).

[0149] Server device 60 may also transmit the media data via a streaming protocol (254). For example, server device 60 may transmit the media data via FLUTE, ROUTE, or other network or over-the-air (OTA) broadcast standards, such as DVB. Client device 40 may then receive at least some of the media data (256). Client device 40 may also determine whether one or more packets have been lost using a packet loss detection mechanism(s) (258). If no packets have been lost (the "no" branch of 258), client device 40 may continue to present the media object (272), e.g., audio and / or video data.

[0150] On the other hand, if at least one packet has been lost ("yes" branch of 258), the client device 40 may determine the media data included in the lost packets, and the corresponding position of the media data of the packets in a segment. For example, the client device 40 may use a transport object identifier (TOI) and a start_offset to determine the starting byte position of the media data in the segment. The client device 40 may further use, for example, a signaled block duration to determine the ending byte position of the media data of the lost packets. The client device 40 may then form a byte range request (260) for the lost media data of the lost packets, such as an HTTP partial Get request that specifies a byte range.

[0151] Client device 40 may then transmit the byte range request (262) to server device 60. In response to receiving the byte range request (264), server device 60 may transmit the requested byte range (266) to client device 40, for example, according to a unicast protocol such as HTTP. Client device 40 may then receive the requested byte range (268) and form an appropriate media object (270). Client device 40 may further render the media object (272).

[0152] In this way, Figure 6 The method represents an example of a method for retrieving media data, the method comprising receiving data indicating a packet loss signaling mechanism, wherein the packet loss signaling mechanism comprises at least one of the following: fragments are transmitted in blocks, transport object identifiers (TOIs) are consecutive, or the last packet of an object assigned to the TOI has a specific flag set in the header of the last packet, a base URL, a maximum delay, or a synchronization point in a file delivery header; detecting packet loss using at least one packet loss signaling mechanism, the lost packet including missing media data; generating a byte range request for the missing media data using information from the file delivery header; and delivering an appropriate media object to a media application.

[0153] Figure 6 The method also represents an example of a method for transmitting media data, the method comprising transmitting data indicating a packet loss signaling mechanism, wherein the packet loss signaling mechanism comprises at least one of the following: fragments are transmitted in blocks, transmission object identifiers (TOIs) are consecutive, or the last packet of an object assigned to the TOI has a specific flag set in the header of the last packet, a base URL, a maximum delay, or a synchronization point in a file delivery header; transmitting one or more packets including the media data via a broadcast or multicast protocol; receiving a byte range request from a client device via a unicast protocol, the byte range request indicating media data of one of the lost packets; and transmitting the byte range of media data to the client device via the unicast protocol in response to the byte range request.

[0154] Certain techniques of the present disclosure are summarized in the following examples:

[0155] Example 1: A method for retrieving media data, the method comprising: receiving data indicating a packet loss signaling mechanism, the data comprising at least one of the following: fragments are transmitted in chunks, TOIs are contiguous, or the last packet of an object assigned to a TOI has a specific flag set in a header of the last packet, a base URL, a maximum delay, or a synchronization point in a file delivery header; detecting packet loss using at least one packet loss signaling mechanism, the lost packet including missing media data; generating a byte range request for the missing media data using information from the file delivery header; and delivering an appropriate media object to a media application.

[0156] Example 2: The method according to Example 1, wherein the file delivery header includes a ROUTE header or a FLUTE header.

[0157] Example 3: A method according to any one of Examples 1 and 2, wherein the information of the file delivery header includes a TOI and a start_offset value.

[0158] Example 4: The method of any one of Examples 1-3, wherein the appropriate media object is a partial media object that omits at least some of the missing media data.

[0159] Example 5: The method of any one of Examples 1-4, wherein delivering the appropriate media object comprises delivering the appropriate media object before an expected delivery time of the media object.

[0160] Example 6: A method according to any one of Examples 1-5, wherein detecting the loss of the packet includes using a signaled inter-packet timeout value to detect the loss of the packet.

[0161] Example 7: The method of Example 6, wherein the inter-packet timeout value is signaled based on a nominal CMAF block duration.

[0162] Example 8: The method of any one of Examples 6 and 7 further includes determining the block duration from a multicast transport packet header, multicast object metadata in a file delivery table (FDT) or enhanced FDT (EFDT), or in control plane service or session metadata.

[0163] Example 9: The method of any one of Examples 6-8, further comprising determining whether block duration signaling takes into account maximum expected packet arrival jitter.

[0164] Example 10: The method of Example 9, wherein when the block duration signaling does not take into account a maximum expected packet arrival jitter, the block duration signaling is determined based on experienced packet reception jitter.

[0165] Example 11: A method according to any of Examples 6-10, wherein generating the byte range request includes generating the byte range request after the inter-packet timeout expires.

[0166] Example 12: The method of any one of Examples 1-11 further includes submitting the byte range request via a unicast protocol.

[0167] Example 13: The method of Example 12, wherein the unicast protocol comprises HTTP.

[0168] Example 14: A device for retrieving media data, the device comprising one or more components for performing the method described in any of Examples 1-13.

[0169] Example 15: The apparatus of Example 14, wherein the one or more components include one or more processors implemented in a circuit.

[0170] Example 16: A device according to Example 14, wherein the device includes at least one of the following: an integrated circuit; a microprocessor; or a wireless communication device.

[0171] Example 17: A computer-readable storage medium having instructions stored thereon, which instructions, when executed, cause a processor to perform the method of any one of Examples 1-13.

[0172] Example 18: An apparatus for retrieving media data, the apparatus comprising: means for receiving data indicating a packet loss signaling mechanism, the data comprising an indication of at least one of: fragments are delivered in chunks, TOIs are contiguous, or the last packet of an object assigned to a TOI has a particular flag set in a header of the last packet, a base URL, a maximum delay, or a synchronization point in a file delivery header; means for detecting packet loss using at least one packet loss signaling mechanism, the lost packet including missing media data; means for generating a byte range request for the missing media data using information from the file delivery header; and means for delivering an appropriate media object to a media application.

[0173] Example 19: A method of transmitting media data, the method comprising transmitting data indicating a packet loss signaling mechanism, the data comprising an indication of at least one of the following: fragments are transmitted in blocks, TOIs are consecutive, the last packet of an object assigned to the TOI has a specific flag set in the header of the last packet, a base URL, a maximum delay, or a synchronization point in a file delivery header; transmitting one or more packets including media data via a broadcast or multicast protocol; receiving a byte range request from a client device via a unicast protocol, the byte range request indicating media data of one of the lost packets; and in response to the byte range request, transmitting the media data of the byte range to the client device via the unicast protocol.

[0174] Example 20: An apparatus for transmitting media data, the apparatus comprising one or more components for performing the method of Example 19.

[0175] Example 21: A device according to Example 20, wherein the device includes at least one of the following: an integrated circuit; a microprocessor; or a wireless communication device.

[0176] Example 22: A computer-readable storage medium having instructions stored thereon, which when executed cause a processor to perform the method of Example 19.

[0177] Example 23: A device for transmitting media data, the device comprising a component for transmitting data indicating a packet loss signaling mechanism, the data comprising at least one of the following: fragments are transmitted in blocks, TOIs are consecutive, and the last packet of an object assigned to the TOI has a specific flag set in the header of the last packet, a base URL, a maximum delay, or a synchronization point in a file delivery header; a component for transmitting one or more packets including media data via a broadcast or multicast protocol; a component for receiving a byte range request from a client device via a unicast protocol, the byte range request indicating media data of one of the lost packets; and a component for transmitting the byte range of media data to the client device via the unicast protocol in response to the byte range request.

[0178] In one or more examples, the described functions may be implemented in hardware, software, firmware, or any combination thereof. If implemented in software, the functions may be stored on or transmitted through a computer-readable medium as one or more instructions or codes and executed by a hardware-based processing unit. Computer-readable media may include computer-readable storage media, which corresponds to tangible media such as data storage media, or communication media, which includes, for example, any medium that facilitates the transfer of a computer program from one place to another according to a communication protocol. In this manner, computer-readable media may generally correspond to (1) a non-temporary tangible computer-readable storage medium, or (2) a communication medium such as a signal or carrier wave. Data storage media may be any available medium that can be accessed by one or more computers or one or more processors to retrieve instructions, codes, and / or data structures to implement the techniques described in the present disclosure. A computer program product may include a computer-readable medium.

[0179] As an example and not limitation, such computer-readable storage media may include RAM, ROM, EEPROM, CD-ROM or other optical disk storage, disk storage or other magnetic storage devices, flash memory or any other can be used to store the required program code in the form of instructions or data structures, and can be accessed by the computer. Moreover, any connection is appropriately referred to as a computer-readable medium. For example, if a coaxial cable, fiber optic cable, twisted pair, digital subscriber line (DSL) or wireless technology (such as infrared, radio and microwave) is used to send instructions from a website, server or other remote source, the definition of the medium includes coaxial cable, fiber optic cable, twisted pair, digital subscriber line or wireless technology such as infrared, radio and microwave. However, it should be understood that computer-readable storage media and data storage media do not include connections, carriers, signals or other transient media, but are directed to non-transient tangible storage media. The disks and optical disks used herein include compact disks (CDs), laser optical disks, optical disks, digital versatile disks (DVDs), floppy disks and blue-ray disks, where disks usually copy data magnetically, while optical disks copy data optically by lasers. The above combination should also be included in the scope of computer-readable media.

[0180] 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 circuits. Therefore, the term "processor" as used herein may refer to any of the foregoing 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 incorporated in a combined codec. Similarly, the technology may be fully implemented in one or more circuits or logic elements.

[0181] The techniques of the present disclosure may be implemented in a variety of devices or apparatuses including a wireless handset, an integrated circuit (IC), or a set of integrated circuits (e.g., a chipset). Various components, modules, or units are described in this disclosure to emphasize functional aspects of a device configured to perform the disclosed techniques, but need not be implemented by different hardware units. Rather, as described above, the various units may be combined in a codec hardware unit in conjunction with appropriate software and / or firmware or provided by some interoperating hardware unit, which includes one or more processors as described above.

[0182] Various examples have been described. These and other examples are within the scope of the following claims.

Claims

1. A method for retrieving media data, the method comprising: receiving data indicating a packet loss signaling mechanism of a broadcast or multicast media streaming session, the packet loss signaling mechanism comprising at least one of the following: fragments are transmitted in chunks, a transport object identifier TOI is consecutive, or a last packet of an object assigned to a TOI has a specific flag set in a header of the last packet, a base URL, a maximum delay, or a synchronization point in a file delivery header; receiving media data of the media streaming session according to a broadcast or multicast network protocol; detecting packet loss of the media streaming session using at least one of the packet loss signaling mechanisms, the lost packets comprising missing media data; generating a byte range request for the missing media data using information from the file delivery header, the byte range request specifying a byte range corresponding to a segment of the missing media data; submitting the byte range request via a unicast protocol; In response to the byte range request, receiving replacement media data for the lost media data; as well as An appropriate media object is delivered to a media application, the appropriate media object comprising the received media data of the media streaming session and the replacement media data.

2. The method according to claim 1, wherein: Detecting the loss of the packet comprises detecting the loss of the packet using a signaled inter-packet timeout value, and preferably wherein the inter-packet timeout value is signaled according to a nominal Common Media Application Format (CMAF) block duration.

3. The method according to claim 2 also includes determining the block duration from the multicast transport packet header, the multicast object metadata in the file delivery table FDT or enhanced FDT, or in the control plane service or session metadata, or signaling data representing the block duration in the multicast transport packet header, the multicast object metadata in the file delivery table FDT or enhanced FDT, or in the control plane service or session metadata.

4. The method of claim 2, further comprising determining whether the inter-packet timeout value signaled according to the nominal CMAF block duration takes into account maximum expected packet arrival jitter.

5. The method according to claim 4, wherein: When the inter-packet timeout value signaled according to the nominal CMAF block duration does not take into account the maximum expected packet arrival jitter, the block duration signaling is determined according to the experienced packet reception jitter.

6. The method according to claim 5, wherein: Generating the byte-range request includes generating the byte-range request after expiration of the inter-packet timeout value.

7. The method according to claim 1, wherein: The file delivery header includes a ROUTE header or a FLUTE header.

8. The method according to claim 1, wherein: The information of the file delivery header includes TOI and start_offset value.

9. The method according to claim 1, wherein: The appropriate media object is a partial media object that omits at least some of the missing media data.

10. The method according to claim 1, wherein: Delivering the appropriate media object includes delivering the appropriate media object prior to an expected delivery time of the media object.

11. The method according to claim 1, wherein: The unicast protocol includes HTTP.

12. A device for retrieving media data, the device comprising: a memory configured to store media data; and One or more processors implemented in circuits and configured to: receiving data indicating a packet loss signaling mechanism of a broadcast or multicast media streaming session, the packet loss signaling mechanism comprising at least one of the following: fragments are transmitted in chunks, a transport object identifier TOI is consecutive, or a last packet of an object assigned to a TOI has a specific flag set in a header of the last packet, a base URL, a maximum delay, or a synchronization point in a file delivery header; receiving media data of the media streaming session according to a broadcast or multicast network protocol; detecting packet loss of the media streaming session using at least one of the packet loss signaling mechanisms, the lost packets comprising missing media data; generating a byte range request for the missing media data using information from the file delivery header, the byte range request specifying a byte range corresponding to a segment of the missing media data; submitting the byte range request via a unicast protocol; In response to the byte range request, receiving replacement media data for the lost media data; as well as An appropriate media object is delivered to a media application, the appropriate media object comprising the received media data of the media streaming session and the replacement media data.

13. The device according to claim 12, wherein: The one or more processors are configured to detect loss of the packets using a signaled inter-packet timeout value, and preferably wherein the inter-packet timeout value is signaled according to a nominal Common Media Application Format (CMAF) chunk duration.

14. The device according to claim 13, wherein: The one or more processors are also respectively configured to determine the block duration from the multicast transport packet header, the multicast object metadata in the file delivery table FDT or enhanced FDT, or in the control plane service or session metadata, or to signal data representing the block duration in the multicast transport packet header, the multicast object metadata in the file delivery table FDT or enhanced FDT, or in the control plane service or session metadata.

15. The apparatus according to claim 13, wherein: The one or more processors are further configured to determine whether the inter-packet timeout value signaled according to the nominal CMAF block duration accounts for a maximum expected packet arrival jitter.

16. The apparatus according to claim 12, wherein: The file delivery header includes a ROUTE header or a FLUTE header.

17. The apparatus according to claim 12, wherein: The information of the file delivery header includes TOI and start_offset value.

18. The apparatus according to claim 12, wherein: The device comprises at least one of the following: integrated circuit; microprocessor; or Wireless communication equipment.

19. A computer readable storage medium having stored thereon instructions which, when executed, cause a processor to: receiving data indicating a packet loss signaling mechanism of a broadcast or multicast media streaming session, the packet loss signaling mechanism comprising at least one of the following: fragments are transmitted in chunks, a transport object identifier TOI is consecutive, or a last packet of an object assigned to a TOI has a specific flag set in a header of the last packet, a base URL, a maximum delay, or a synchronization point in a file delivery header; receiving media data of the media streaming session according to a broadcast or multicast network protocol; detecting packet loss of the media streaming session using at least one of the packet loss signaling mechanisms, the lost packets comprising missing media data; generating a byte range request for the missing media data using information from the file delivery header, the byte range request specifying a byte range corresponding to a segment of the missing media data; submitting the byte range request via a unicast protocol; In response to the byte range request, receiving replacement media data for the lost media data; as well as An appropriate media object is delivered to a media application, the appropriate media object comprising the received media data of the media streaming session and the replacement media data.

20. A device for retrieving media data, the device comprising: means for receiving data indicating a packet loss signaling mechanism of a broadcast or multicast media streaming session, the packet loss signaling mechanism comprising at least one of the following: fragments are transmitted in chunks, transport object identifiers TOIs are consecutive, or the last packet of an object assigned to a TOI has a specific flag set in a header of the last packet, a base URL, a maximum delay, or a synchronization point in a file delivery header; means for receiving media data for said media streaming session according to a broadcast or multicast network protocol; means for detecting packet loss of said media streaming session using at least one of said packet loss signaling mechanisms, said lost packets comprising missing media data; means for generating a byte range request for the missing media data using information from the file delivery header, the byte range request specifying a byte range corresponding to a segment of the missing media data; means for submitting said byte range request via a unicast protocol; means for receiving, in response to the byte range request, replacement media data for the lost media data; as well as Means for delivering an appropriate media object to a media application, the appropriate media object comprising the received media data of the media streaming session and the replacement media data.

21. A method for transmitting media data, the method comprising: transmitting data indicating a packet loss signaling mechanism of a broadcast or multicast media streaming session, the packet loss signaling mechanism comprising at least one of the following: fragments are transmitted in chunks, transport object identifiers TOIs are consecutive, or the last packet of an object assigned to a TOI has a specific flag set in a header of the last packet, a base URL, a maximum delay, or a synchronization point in a file delivery header; transmitting one or more packets comprising media data of the media streaming session via a broadcast or multicast protocol; receiving a byte range request from a client device via a unicast protocol, the byte range request indicating media data of one of the packets that was lost, the byte range request specifying a byte range of a segment of the media data corresponding to the one of the packets that was lost; as well as In response to the byte range request, the media data of the byte range is transmitted to the client device via the unicast protocol.

22. The method according to claim 21, wherein: Transmitting data indicating the packet loss signaling method also includes transmitting data representing an inter-packet timeout value, and preferably, wherein transmitting data representing the inter-packet timeout value includes signaling the inter-packet timeout value according to a nominal common media application format CMAF block duration.

23. The method according to claim 22 also includes determining the block duration from the multicast transport packet header, the multicast object metadata in the file delivery table FDT or enhanced FDT, or in the control plane service or session metadata, or signaling data representing the block duration in the multicast transport packet header, the multicast object metadata in the file delivery table FDT or enhanced FDT, or in the control plane service or session metadata.

24. The method according to claim 21, wherein: The file delivery header includes a ROUTE header or a FLUTE header.

25. The method according to claim 21, wherein: The information of the file delivery header includes TOI and start_offset value.

26. The method according to claim 21, wherein: The unicast protocol includes HTTP.

27. A device for transmitting media data, the device comprising: a memory configured to store video data; and One or more processors implemented in circuits and configured to: transmitting data indicating a packet loss signaling mechanism of a broadcast or multicast media streaming session, the packet loss signaling mechanism comprising at least one of the following: fragments are transmitted in chunks, transport object identifiers TOIs are consecutive, or the last packet of an object assigned to a TOI has a specific flag set in a header of the last packet, a base URL, a maximum delay, or a synchronization point in a file delivery header; transmitting one or more packets comprising media data of the media streaming session via a broadcast or multicast protocol; receiving a byte range request from a client device via a unicast protocol, the byte range request indicating media data of one of the packets that was lost, the byte range request specifying a byte range of a segment of the media data corresponding to the one of the packets that was lost; as well as In response to the byte range request, the media data of the byte range is transmitted to the client device via the unicast protocol.

28. The apparatus of claim 27, wherein: The one or more processors are further configured to transmit data representing an inter-packet timeout value, and preferably, wherein the one or more processors are configured to signal the inter-packet timeout value according to a nominal Common Media Application Format (CMAF) chunk duration.

29. The apparatus of claim 27, wherein: The one or more processors are also respectively configured to determine the block duration from the multicast transport packet header, the multicast object metadata in the file delivery table FDT or enhanced FDT, or in the control plane service or session metadata, or to signal data representing the block duration in the multicast transport packet header, the multicast object metadata in the file delivery table FDT or enhanced FDT, or in the control plane service or session metadata.

30. The apparatus of claim 27, wherein: The file delivery header includes a ROUTE header or a FLUTE header.

31. The apparatus of claim 27, wherein: The information of the file delivery header includes TOI and start_offset value.

32. The apparatus of claim 27, wherein: The unicast protocol includes HTTP.

33. The apparatus of claim 27, wherein: The device comprises at least one of the following: integrated circuit; microprocessor; or Wireless communication equipment.

34. A computer readable storage medium having stored thereon instructions which, when executed, cause a processor to: transmitting data indicating a packet loss signaling mechanism of a broadcast or multicast media streaming session, the packet loss signaling mechanism comprising at least one of the following: fragments are transmitted in chunks, transport object identifiers TOIs are consecutive, or the last packet of an object assigned to a TOI has a specific flag set in a header of the last packet, a base URL, a maximum delay, or a synchronization point in a file delivery header; transmitting one or more packets comprising media data of the media streaming session via a broadcast or multicast protocol; receiving a byte range request from a client device via a unicast protocol, the byte range request indicating media data of one of the packets that was lost, the byte range request specifying a byte range of a segment of the media data corresponding to the one of the packets that was lost; as well as In response to the byte range request, the media data of the byte range is transmitted to the client device via the unicast protocol.

35. A device for transmitting media data, the device comprising: means for transmitting data indicating a packet loss signaling mechanism of a broadcast or multicast media streaming session, the packet loss signaling mechanism comprising at least one of the following: fragments are transmitted in chunks, transport object identifiers TOI are consecutive, or the last packet of an object assigned to a TOI has a specific flag set in the header of the last packet, a base URL, a maximum delay, or a synchronization point in a file delivery header; means for transmitting one or more packets comprising media data of said media streaming session via a broadcast or multicast protocol; means for receiving a byte range request from a client device via a unicast protocol, the byte range request indicating media data of one of the packets that was lost, the byte range request specifying a byte range of a segment of the media data corresponding to the one of the packets that was lost; as well as Means for transmitting the media data of the byte range to the client device via the unicast protocol in response to the byte range request.

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