阅读说明：本技术 用于流式传输媒体数据的服务描述 (Service description for streaming media data ) 是由 T.斯托克哈默 N.K.梁 于 2019-10-03 设计创作，主要内容包括：一种用于接收媒体数据的设备,该设备包括：配置为存储媒体呈现的媒体数据的存储器；以及一个或多个在电路中实现的处理器并且该处理器配置为：检索包括数据的服务描述,该数据包括用于媒体呈现的一个或多个回放偏好,该回放偏好包括期望的端到端时延；经由网络流式传输协议检索媒体呈现的媒体数据；以及根据一个或多个回放偏好呈现检索到的媒体数据,并实现期望的端到端时延。例如,回放偏好可以指定回放速率的加速或减速,以便实现期望的端到端时延。因此,如果缓冲器填充过快,则设备可以加速回放；或者如果缓冲器清空过快,则设备可以减速回放,以防止缓冲器溢出或下溢,从而避免回放中断而不改变时延。(An apparatus for receiving media data, the apparatus comprising: a memory configured to store media data of a media presentation; and one or more processors implemented in the circuitry and configured to: retrieving a service description comprising data comprising one or more playback preferences for the media presentation, the playback preferences comprising an expected end-to-end latency; retrieving media data of a media presentation via a network streaming protocol; and rendering the retrieved media data according to the one or more playback preferences and achieving the desired end-to-end latency. For example, the playback preferences may specify an acceleration or deceleration of the playback rate in order to achieve a desired end-to-end latency. Thus, if the buffer fills too fast, the device can speed up playback; or if the buffer is emptied too quickly, the device may slow down playback to prevent buffer overflow or underflow, thereby avoiding playback interruption without changing latency.)

1. A method of retrieving media data, the method comprising:

retrieving a service description comprising data comprising one or more playback preferences for a corresponding media presentation, the playback preferences comprising a desired end-to-end latency;

retrieving media data of the media presentation via a network streaming protocol; and

rendering the retrieved media data according to the one or more playback preferences and achieving the desired end-to-end latency.

2. The method of claim 1, wherein retrieving the service description comprises:

retrieving a manifest file for the media presentation;

determining a network location of the service description from the manifest file; and

retrieving the service description from the network location.

3. The method of claim 2, wherein the manifest file comprises a Media Presentation Description (MPD).

4. The method of claim 2, wherein determining the network location comprises: determining the network location from an xlink parameter of the manifest file, the xlink parameter representing the network location of the service description.

5. The method of claim 1, wherein the playback preferences include data representing at least one of a maximum latency or a minimum latency for presentation of the media presentation.

6. The method of claim 5, wherein the playback preference maps the media data to a wall clock time at which the media data is to be presented to achieve at least one of the desired end-to-end latency, the maximum latency, or the minimum latency.

7. The method of claim 1, wherein the playback preferences comprise data representing relative levels of quality for corresponding time delays.

8. The method of claim 1, wherein presenting the retrieved media data comprises: discarding the retrieved media data without rendering the discarded retrieved media data to achieve the desired end-to-end latency.

9. The method of claim 1, wherein presenting the retrieved media data comprises: synchronizing presentation of the media data with presentation of the media data by another device.

10. The method of claim 1, wherein the service description specifies a maximum accelerated playback rate and a minimum decelerated playback rate, and wherein presenting the retrieved media data comprises: speeding up or slowing down playback rate within the maximum and minimum slowed playback rates to achieve the desired end-to-end latency.

11. An apparatus for retrieving media data, the apparatus comprising:

a memory configured to store media data of a media presentation; and

one or more processors implemented in circuitry and configured to:

retrieving a service description comprising data comprising one or more playback preferences for the media presentation, the playback preferences comprising a desired end-to-end latency;

retrieving the media data of the media presentation via a network streaming protocol; and

rendering the retrieved media data according to the one or more playback preferences and achieving the desired end-to-end latency.

12. The device of claim 11, wherein to retrieve the service description, the one or more processors are configured to:

retrieving a manifest file for the media presentation;

determining a network location of the service description from the manifest file; and

retrieving the service description from the network location.

13. The device of claim 12, wherein the manifest file comprises a Media Presentation Description (MPD).

14. The device of claim 12, wherein the one or more processors are configured to determine the network location from an xlink parameter of the manifest file, the xlink parameter representing the network location of the service description.

15. The device of claim 11, wherein the playback preferences include data representing at least one of a maximum latency or a minimum latency for presentation of the media presentation.

16. The device of claim 15, wherein the playback preference maps the media data to a wall clock time at which the media data is to be presented to achieve at least one of the desired end-to-end latency, the maximum latency, or the minimum latency.

17. The device of claim 11, wherein the playback preferences include data representing relative levels of quality for corresponding time delays.

18. The device of claim 11, wherein the one or more processors are configured to discard the retrieved media data without rendering the discarded retrieved media data to achieve the desired end-to-end latency.

19. The device of claim 11, wherein the one or more processors are configured to synchronize the presentation of the media data with the presentation of the media data by another device.

20. The device of claim 11, wherein the service description specifies a maximum accelerated playback rate and a minimum decelerated playback rate, and wherein the one or more processors are configured to accelerate or decelerate playback rates within the maximum accelerated playback rate and the minimum decelerated playback rate to achieve the desired end-to-end latency.

21. A computer-readable storage medium having instructions stored thereon that, when executed, cause a processor to:

retrieving a service description comprising data comprising one or more playback preferences for a corresponding media presentation, the playback preferences comprising a desired end-to-end latency;

retrieving media data of the media presentation via a network streaming protocol; and

rendering the retrieved media data according to the one or more playback preferences and achieving the desired end-to-end latency.

22. The computer-readable storage medium of claim 21, wherein the service description specifies a maximum accelerated playback rate and a minimum decelerated playback rate, and wherein the instructions that cause the processor to present the retrieved media data comprise: instructions that cause the processor to speed up or slow down playback rate within the maximum accelerated playback rate and the minimum decelerated playback rate to achieve the desired end-to-end latency.

23. An apparatus for retrieving media data, the apparatus comprising:

means for retrieving a service description comprising data comprising one or more playback preferences for a corresponding media presentation, the playback preferences comprising a desired end-to-end latency;

means for retrieving media data for the media presentation via a network streaming protocol; and

means for rendering the retrieved media data according to the one or more playback preferences and implementing the desired end-to-end latency.

24. The device of claim 23, wherein the service description specifies a maximum accelerated playback rate and a minimum decelerated playback rate, and wherein the means for presenting the retrieved media data comprises: means for accelerating or decelerating playback rate within the maximum accelerated playback rate and the minimum decelerated playback rate to achieve the desired end-to-end latency.

25. A method of transmitting media data, the method comprising:

sending a service description to a client device that includes data that includes one or more playback preferences for a corresponding media presentation, the playback preferences including an expected end-to-end latency;

receiving a request from the client device for media data of the media presentation; and

in accordance with the one or more playback preferences, in response to a request for the media data from the client device, sending the media data of the media presentation to the client device and implementing the desired end-to-end latency.

26. The method of claim 25, wherein the playback preferences include data representing at least one of a maximum latency or a minimum latency for presentation of the media presentation.

27. The method of claim 26, wherein the playback preference maps the media data to a wall clock time at which the media data is to be presented to achieve at least one of the desired end-to-end latency, the maximum latency, or the minimum latency.

28. The method of claim 25, wherein the playback preferences include data representing relative levels of quality for corresponding time delays.

29. The method of claim 25, wherein the service description specifies a maximum accelerated playback rate and a minimum decelerated playback rate to achieve the desired end-to-end latency.

30. An apparatus for transmitting media data, the apparatus comprising:

a memory configured to store media data for a media presentation and a service description, the service description comprising one or more playback preferences for the media presentation, the playback preferences comprising a desired end-to-end latency; and

one or more processors implemented in circuitry and configured to:

sending the service description to a client device;

receiving a request from the client device for the media data of the media presentation; and

sending the media data of the media presentation to the client device in response to a request for the media data from the client device to achieve the desired end-to-end latency in accordance with the one or more playback preferences.

31. The device of claim 30, wherein the playback preferences include data representing at least one of a maximum latency or a minimum latency for presentation of the media presentation.

32. The device of claim 31, wherein the playback preference maps the media data to a wall clock time at which the media data is to be presented to achieve at least one of the desired end-to-end latency, the maximum latency, or the minimum latency.

33. The device of claim 30, wherein the playback preferences include data representing relative levels of quality for corresponding time delays.

34. The device of claim 30, wherein the service description specifies a maximum accelerated playback rate and a minimum decelerated playback rate to achieve the desired end-to-end latency.

35. A computer-readable storage medium having instructions stored thereon that, when executed, cause a processor to:

sending a service description to a client device that includes data that includes one or more playback preferences for a corresponding media presentation, the playback preferences including an expected end-to-end latency;

receiving a request from the client device for media data of the media presentation; and

in accordance with the one or more playback preferences, in response to a request for the media data from the client device, sending the media data of the media presentation to the client device and implementing the desired end-to-end latency.

36. The computer-readable storage medium of claim 35, wherein the service description specifies a maximum accelerated playback rate and a minimum decelerated playback rate to achieve the desired end-to-end latency.

37. An apparatus for transmitting media data, the apparatus comprising:

means for sending a service description including data to a client device, the data including one or more playback preferences for a corresponding media presentation, the playback preferences including an expected end-to-end latency;

means for receiving a request for media data of the media presentation from the client device; and

means for sending the media data of the media presentation to the client device in response to a request for the media data from the client device in accordance with the one or more playback preferences, and implementing the desired end-to-end latency.

38. The device of claim 37, wherein the service description specifies a maximum accelerated playback rate and a minimum decelerated playback rate to achieve the desired end-to-end latency.

Technical Field

The present disclosure relates to storage and transmission of encoded video data.

Background

Digital video functionality 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 gaming devices, video game consoles, cellular or satellite radio telephones, video teleconferencing equipment, and the like. Digital video devices implement video compression techniques such as those described in standards defined by MPEG-2, MPEG-4, ITU-T h.263, or ITU-T h.264/MPEG-4 part 10, Advanced Video Coding (AVC), ITU-T h.265 (also known as High Efficiency Video Coding (HEVC)), and extensions of such standards to more efficiently transmit and receive digital video information.

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

After the video data has been encoded, the video data may be packetized for transmission or storage. The video data may be combined 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 extensions thereof, such as AVC.

Disclosure of Invention

In general, this disclosure describes techniques for transmitting data describing a media presentation. The server device may indicate service description data for a media presentation representing presentation settings that should provide a priority user experience. The client device may use the service description data to modify playback of the media data. For example, for some presentations (e.g., real-time events such as sporting events), it may be better for the user to experience immediately when the presented event occurs, such that if re-buffering is experienced, some of the previously received media data may be discarded. For other presentations (e.g., movies or television programs), it may be better for the user to experience the entire presentation, such that if re-buffering is experienced, the previously received media data is presented. Likewise, the service description may specify one or more target latencies for the media presentation, corresponding qualities of the latencies, and playback rate adjustments (e.g., speed up or speed down rates) to achieve and maintain the latencies.

In one example, a method of retrieving media data includes: retrieving a service description comprising data comprising one or more playback preferences for a corresponding media presentation, the playback preferences comprising a desired end-to-end latency; retrieving media data of a media presentation via a network streaming protocol; and rendering the retrieved media data according to the one or more playback preferences and achieving the desired end-to-end latency.

In another example, an apparatus for retrieving media data, the apparatus comprising: a memory configured to store media data of a media presentation; and one or more processors implemented in the circuitry and configured to: retrieving a service description comprising data comprising one or more playback preferences for the media presentation, the playback preferences comprising an expected end-to-end latency; retrieving media data of a media presentation via a network streaming protocol; and rendering the retrieved media data according to the one or more playback preferences and achieving the desired end-to-end latency.

In another example, a computer readable storage medium has stored thereon instructions that, when executed, cause a processor to perform the steps of: retrieving a service description comprising data comprising one or more playback preferences for a corresponding media presentation, the playback preferences comprising a desired end-to-end latency; retrieving media data of a media presentation via a network streaming protocol; and rendering the retrieved media data according to the one or more playback preferences and achieving the desired end-to-end latency.

In another example, an apparatus to retrieve media data includes: means for retrieving a service description comprising data comprising one or more playback preferences for a corresponding media presentation, the playback preferences comprising a desired end-to-end latency; means for retrieving media data for a media presentation via a network streaming protocol; and means for rendering the retrieved media data according to one or more playback preferences and achieving a desired end-to-end latency.

In another example, a method of transmitting media data, the method comprising: sending, to the client device, a service description including data comprising one or more playback preferences for the corresponding media presentation, the playback preferences including an expected end-to-end latency; receiving a request for media data of a media presentation from a client device; and transmitting media data of the media presentation to the client device in response to a request for the media data from the client device according to the one or more playback preferences and achieving a desired end-to-end latency.

In another example, an apparatus for transmitting media data, the apparatus comprising: a memory configured to store media data for a media presentation and a service description including one or more playback preferences for the media presentation, the playback preferences including a desired end-to-end latency; and one or more processors implemented in the circuitry and configured to: sending the service description to the client device; receiving a request for media data of a media presentation from a client device; and transmitting media data for the media presentation to the client device in response to a request for the media data from the client device according to the one or more playback preferences and achieving a desired end-to-end latency.

In another example, a computer readable storage medium has stored thereon instructions that, when executed, cause a processor to perform the steps of: sending, to the client device, a service description including data comprising one or more playback preferences for the corresponding media presentation, the playback preferences including an expected end-to-end latency; receiving a request for media data of a media presentation from a client device; media data of the media presentation is sent to the client device in response to a request for the media data from the client device and a desired end-to-end latency is achieved, in accordance with the one or more playback preferences.

In another example, an apparatus for transmitting media data, the apparatus comprising: means for sending a service description including data to a client device, the data including one or more playback preferences for a corresponding media presentation, the playback preferences including an expected end-to-end latency; means for receiving a request for media data of a media presentation from a client device; and means for sending media data of the media presentation to the client device in response to a request for the media data from the client device according to the one or more playback preferences, and implementing a desired end-to-end latency.

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

Drawings

Fig. 1 is a block diagram illustrating an example system implementing techniques for streaming media data over a network in accordance with the techniques of this disclosure.

FIG. 2 is a block diagram illustrating an example set of components of a retrieval unit in more detail.

Fig. 3 is a conceptual diagram illustrating elements of example multimedia content.

FIG. 4 is a block diagram illustrating elements of an example video file, which may correspond to a segment of a presentation.

Fig. 5 is a conceptual diagram illustrating an example architecture including devices that may perform techniques of this disclosure.

Fig. 6 is a conceptual diagram illustrating example operation of a DASH packetizer in an example low latency mode in accordance with the techniques of this disclosure.

Fig. 7 is a conceptual diagram illustrating an example DASH client configuration in accordance with the techniques of this disclosure.

Fig. 8 is a flow diagram illustrating an example method of sending media data to a client device in accordance with the techniques of this disclosure.

Fig. 9 is a flow diagram illustrating an example method of retrieving media data in accordance with the techniques of this disclosure.

Detailed Description

In general, this disclosure describes techniques for transmitting data describing a media presentation. The server device may indicate service description data for rendering a media presentation that should provide presentation settings of a prioritized user experience. The client device may use the service description data to modify playback of the media data. For example, for some presentations (e.g., real-time events such as sporting events), it may be better for the user to experience immediately when the presented event occurs, such that if re-buffering is experienced, some of the previously received media data may be discarded. For other presentations (e.g., movies or television programs), it may be better for the user to experience the entire presentation, such that if re-buffering is experienced, the previously received media data is presented.

In general, the techniques of this disclosure may be used for network Streaming, such as HTTP Streaming (e.g., Dynamic Adaptive Streaming over HTTP (DASH)). In HTTP streaming, common operations include HEAD, GET, and partial GET. The HEAD operation retrieves the header of the 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. Thus, movie fragments (movie fragments) can be provided for HTTP streaming, since the partial GET operation can retrieve one or more individual movie fragments. In a movie fragment, there may be several track fragments (track fragments) of different tracks. In HTTP streaming, a media presentation may be a structured collection of data accessible to a client. The client may request and download media data information to present the streaming service to the user.

In the example of 3GPP data streaming using HTTP streaming, there may be multiple presentations of video and/or audio data of multimedia content. As described below, different presentations may correspond to different coding characteristics (e.g., different profiles or levels of a video coding standard), different coding standards or extensions of a coding standard (e.g., multi-view and/or scalable extensions), or different bitrates. The manifest of such a Presentation may be defined in a Media Presentation Description (MPD) data structure. The media presentation may correspond to a structured collection of data accessible to the HTTP streaming client device. An HTTP streaming client device may request and download media data information to present a streaming service to a user of the client device. A media presentation may be described in an MPD data structure, which may include an update of the MPD.

The media presentation may contain a sequence of one or more time periods. Each time period may extend to the beginning of the next time period or, for the last time period, until the end of the media presentation. Each time segment may contain one or more presentations of the same media content. The presentation may be one of many alternative encoded versions of audio, video, timed text, or other such data. These presentations may differ by coding type (e.g., bit rate, resolution, and/or codec for video data and bit rate, language, and/or codec for audio data). The term presentation may be used to refer to a portion of encoded audio or video data that corresponds to a particular time period of multimedia content and is encoded in a particular manner.

The presentation for a certain period of time may be assigned to the group indicated by an attribute in the MPD indicating the adaptation set (adaptation set) to which the presentation belongs. Presentations in the same adaptation set are generally considered alternatives to each other in that the client device can dynamically and seamlessly switch between these presentations, e.g., to perform bandwidth adaptation. For example, each presentation of video data for a particular time period may be assigned to the same adaptation set, such that any presentation may be selected for decoding to present media data, e.g., video data or audio data, of the multimedia content for the corresponding time period. In some examples, media content within a time period may be presented by a combination of one presentation from group 0 (if any) or at most one presentation from each non-zero group. The timing data for each presentation of a time period may be represented relative to a start time of the time period.

A presentation may comprise one or more segments. Each presentation may include an initialization segment, or each segment of a presentation may be self-initializing. When present, the initialization segment may contain initialization information for accessing the presentation. Typically, the initialization segment does not contain media data. A segment 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 segment. In some examples, the MPD may also provide byte ranges in the form of range attributes, which may correspond to segmented data within a file accessible by a URL, URN, or URI.

Different presentations may be selected for retrieving different types of media data substantially simultaneously. For example, the client device may select an audio presentation, a video presentation, and a timed text presentation to retrieve segments therefrom. In some examples, the client device may select a particular adaptation set to perform bandwidth adaptation. That is, the client device may select an adaptation set that includes a video presentation, an adaptation set that includes an audio presentation, and/or an adaptation set that includes timed text. Alternatively, the client device may select an adaptation set for certain types of media (e.g., video) and directly select for presentation of other types of media (e.g., audio and/or timed text).

DASH-IF (DASH industry forum) and Digital Video Broadcasting (DVB) are currently developing DASH-based solutions for low latency streaming. A key issue in this work is the ability to provide services that are end-to-end delay limited and comparable to other television distribution means. Different delays may be considered. For example, End-to-End Latency (EEL) describes the Latency of an action captured by a camera until the action is visible on a remote screen. As another example, Encoding + Distribution Latency (EDL) describes the Latency of a linear play output (typically used as input to the Distribution encoder (s)) to a screen.

In addition to end-to-end latency, startup delay (sometimes referred to as channel change time) may also be relevant. In this case, two different delays can be distinguished. The real-time Edge Start-up Delay (LSD) describes the time between user operation (service access or service join) and the time until the user perceives the first media sample of the service at the time of the real-time Edge join. The Seek Start-up Delay (SSD) describes the time between a user action (service access or service join) and the time until the first media sample of the service is perceived by the user when seeking the time shift buffer.

Further, another aspect is the ability to accurately synchronize presentations across different devices to achieve a consistent user experience.

For example, DVB is intended to be a technology that is capable of (but not required to) achieve the following goals:

the encoder-to-screen delay is 3.5 seconds.

Real-time edge start-up delay is about 1 second or less.

Presentation of the media time at a particular wall clock time, within a tolerance of 500 milliseconds.

Another object of DVB is to provide a service product that is backward compatible with existing clients so that longer delays can be observed.

Another requirement of DVB is to change the service to run with the lowest latency that is not necessarily required, so that if this is beneficial to network resources and coding efficiency, the service can be set to run with a longer latency. The decision may be decided by the device depending on its environment, or may be decided by the service provider, or both.

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

In the example of fig. 1, content preparation device 20 includes an audio source 22 and a video source 24. The audio source 22 may include, for example, a microphone that produces an electrical signal that represents captured audio data to be encoded by the audio encoder 26. Alternatively, audio source 22 may comprise a storage medium storing previously recorded audio data, an audio data generator such as a computerized synthesizer, or any other source of audio data. Video source 24 may include a video camera that produces 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 may store multimedia content in a separate medium that is read by server device 60.

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

The audio frames corresponding to the video frames are typically audio frames containing audio data captured (or generated) by audio source 22 while having video data captured (or generated) by video source 24 contained within the video frames. For example, audio source 22 captures audio data while a speaking participant typically produces audio data by speaking, and video source 24 simultaneously (i.e., while audio source 22 captures audio data) captures video data of the speaking participant. Thus, an audio frame may correspond in time to one or more particular video frames. Thus, an audio frame corresponding to a video frame generally corresponds to a case where audio data and video data are captured simultaneously, and for this case, the audio frame and the video frame include the audio data and the video data, respectively, that are captured simultaneously.

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

In some examples, audio source 22 may send data corresponding to the time audio data was recorded to audio encoder 26, while video source 24 may send data corresponding to the time 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 need not indicate an absolute time at which the audio data was recorded, and similarly, video encoder 28 may also use the 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.

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

Many video coding standards, such as the ITU-T h.264/AVC and the upcoming High Efficiency Video Coding (HEVC) standard, define syntax, semantics and decoding processes for error-free bitstreams, any of which conforms to a particular profile or level. Video coding standards do not typically specify an encoder, but the task of the encoder is to ensure that the generated bitstream conforms to the standards of the decoder. In the context of video coding standards, a "profile" corresponds to a subset of the algorithms, features or tools and constraints applied to them. For example, as defined by the h.264 standard, a "profile" is a subset of the entire bitstream syntax specified by the h.264 standard. The "level" corresponds to a limit of decoder resource consumption (e.g., decoder memory and computations), which is related to the resolution, bit rate, and block processing rate of the picture. A profile may be signaled with a profile idc (profile _ idc) value while a level may be signaled with a level idc (level indicator) value.

For example, the h.264 standard recognizes that, within the range imposed by the syntax of a given profile, large variations in the performance of the encoder and decoder may still be required depending on the values taken by the syntax element pictures in the bitstream (e.g., the specified size of the decoded image). The h.264 standard further recognizes that in many applications, it is neither practical nor economical to implement a decoder that is capable of handling all of the hypothetical uses of the syntax in a particular configuration file. The h.264 standard therefore defines "levels" as a specified set of constraints imposed on the values of syntax elements in the bitstream. These constraints may be simple limits on the values. Alternatively, these constraints may take the form of constraints on arithmetic combinations of values (e.g., picture width times picture height times number of pictures decoded per second). The h.264 standard further specifies that various implementations may support different levels for each supported profile.

A decoder conforming to a profile typically supports all of the features defined in the profile. For example, as a coding feature, B-picture coding is not supported in the baseline profile of H.264/AVC, while B-picture coding is supported in the other profiles of H.264/AVC. A decoder conforming to a certain level should be able to decode any bit stream that does not require resources beyond the limits defined in that level. The definition of configuration files and levels may be helpful for interpretation. For example, during video transmission, a pair of profile and level definitions may be negotiated and agreed for the entire transmission session. More specifically, in h.264/AVC, a level may define a limit on the number of macroblocks that need to be processed, a Decoded Picture Buffer (DPB) size, a Coded Picture Buffer (CPB) size, a vertical motion vector range, a maximum number of motion vectors per two consecutive MBs, and whether a B block may 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.

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

Video encoder 28 may encode video data of multimedia content in various ways to produce different presentations of multimedia content at various bitrates and with various characteristics (e.g., pixel resolution, frame rate, level of profiles that conform to various encoding standards, profiles that conform to various profiles and/or various encoding standards, presentation with one or more views (e.g., for two-dimensional or three-dimensional playback), or other such features). A presentation as used in this disclosure may include one of audio data, video data, text data (e.g., for closed captioning), or other such data. The presentation may include an elementary stream, such as an audio elementary stream or a video elementary stream. Each PES packet may include stream _ id identifying the elementary stream to which the PES packet belongs. Encapsulation unit 30 is responsible for assembling the elementary streams into various rendered video files (e.g., segments).

Encapsulation unit 30 receives PES packets of the elementary streams for presentation from audio encoder 26 and video encoder 28, and forms corresponding Network Abstraction Layer (NAL) units from the PES packets. Encoded video segments can be organized into NAL units that provide a "network-friendly" video presentation for handling applications such as video telephony, storage, broadcast, or streaming. NAL units can be classified into Video Coding Layer (VCL) NAL units and non-VCL NAL units. The VCL units may contain core compression engines and may include block, macroblock, and/or slice level data. Other NAL units may be non-VCL NAL units. In some examples, a coded picture in one time instance, which is typically presented as a primary coded picture, may be contained in an access unit, which may include one or more NAL units.

non-VCL NAL units may include parameter set NAL units and SEI NAL units, among others. The parameter set may contain sequence level header information (in a Sequence Parameter Set (SPS)) and picture level header information (in a Picture Parameter Set (PPS)) that does not change often. Using parameter sets (e.g., PPS and SPS), information that does not change often need to be repeated for each sequence or picture. Accordingly, coding efficiency can be improved. Furthermore, the use of a set of parameters may enable out-of-band transmission of important header information, thereby avoiding the need for redundant transmission for error recovery. In an out-of-band transmission example, a parameter set NAL unit may be transmitted on a different channel than other NAL units (e.g., SEI NAL units).

Supplemental Enhancement Information (SEI) may contain information that is not needed for decoding the encoded picture samples from VCL NAL units, but may assist processes related to decoding, display, error recovery, and other purposes. SEI messages may be contained in non-VCL NAL units. SEI messages are a specification part of some standard specifications and are therefore not always mandatory for standard compliant decoder implementations. The SEI message may be a sequence level SEI message or a picture level SEI message. Some sequence level information may be contained 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 the operation points and the characteristics of the operation points. In addition, the packaging unit 30 may form a manifest file (manifest file), such as a Media Presentation Descriptor (MPD) that describes characteristics of a presentation. Encapsulation unit 30 may format the MPD according to extensible markup language (XML).

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

In some examples, presentation 68 may be divided into adaptation sets. That is, the respective subsets of the presentation 68 may include respective sets of common features, such as codecs, profiles and levels, resolutions, view numbers, fragmented file formats, text type information that may identify a language or other characteristics of text to be displayed with the presentation and/or audio data to be decoded and presented (e.g., through speakers), camera angle information that may describe camera angles or real-world camera perspectives of scenes for presentation in an adaptation set, rating information describing content suitability for a particular audience, and so forth.

The manifest file 66 may include data indicating a subset of the presentations 68 corresponding to a particular adaptation set and common characteristics of the adaptation sets. The manifest file 66 may also include data representing various characteristics (e.g., bit rates) for various presentations of the adaptation set. In this way, the adaptation set may provide simplified network bandwidth adaptation. The presentation in the adaptation set may be indicated using sub-elements of the adaptation set elements of the manifest file 66.

The server device 60 includes a request processing unit 70 and a network interface 72. In some examples, server device 60 may include multiple network interfaces. Further, any or all of the features of server device 60 may be implemented on other devices of a content delivery network, such as routers, bridges, proxy devices, switches, or other devices. In some examples, an intermediary device of the content delivery network may cache data of multimedia content 64 and include components substantially consistent with those of server device 60. Generally, the network interface 72 is configured to send and receive data via a network 74.

Request processing unit 70 is configured to receive a network request for data of storage medium 62 from a client device, such as client device 40. For example, request processing unit 70 may implement hypertext transfer protocol (HTTP) version 1.1, as described in the following documents: RFC 2616, "hypertext transfer protocol-HTTP/1.1" by r.fielding et al, network working group, IETF, month 6 1999. That is, the request processing unit 70 may be configured to receive HTTP GET or partial GET requests and provide data of the multimedia content 64 in response to the requests. The request may specify the segment of one of the presentations 68, for example using the URL of the segment. In some examples, the request may also specify one or more byte ranges of the segment, thereby including the partial GET request. The request processing unit 70 may be further configured to service HTTP HEAD requests to provide header data of segments of one of the presentations 68. In any case, request processing element 70 may be configured to process the request to provide the requested data to a requesting device, such as client device 40.

Additionally or alternatively, the request processing element 70 may be configured to communicate media data via a broadcast or multicast protocol, such as eMBMS. Content preparation device 20 may create DASH segments and/or sub-segments in substantially the same manner as described, but server device 60 may transmit these segments or sub-segments using eMBMS or another broadcast or multicast network transport protocol. For example, request processing element 70 may be configured to receive a multicast group join request from client device 40. That is, server device 60 may advertise an Internet Protocol (IP) address associated with a multicast group to client devices (including client device 40) associated with particular media content (e.g., a broadcast of a real-time event). The client device 40 may in turn submit a request to join the multicast group. The request may propagate throughout network 74 (e.g., the routers comprising network 74) such that the routers direct traffic destined for the IP address associated with the multicast group to subscribing client devices (e.g., client devices 40).

As shown in the example of fig. 1, the multimedia content 64 includes a manifest file 66, which manifest file 66 may correspond to a Media Presentation Description (MPD). The manifest file 66 may contain descriptions of different alternative presentations 68 (e.g., video services having different qualities), and the descriptions may include, for example, codec information, profile values, level values, bit rates, and other descriptive characteristics of the presentations 68. Client device 40 may retrieve the MPD of the media presentation to determine how to access segments of presentation 68.

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

Retrieval unit 52 may compare the decoding and rendering capabilities of client device 40 to the characteristics of presentation 68 indicated by the information of manifest file 66. Retrieval unit 52 may initially retrieve at least a portion of manifest file 66 to determine characteristics of presentation 68. For example, retrieval unit 52 may request a portion of manifest file 66 describing characteristics of one or more adaptation sets. Retrieval unit 52 may select a subset (e.g., an adaptation set) of presentations 68 having characteristics that may be satisfied by the encoding and rendering capabilities of client device 40. The retrieval unit 52 may then determine the bit rates of the presentations in the adaptation set, determine the current available amount of network bandwidth, and retrieve the segments from one of the presentations having a bit rate that may be met by the network bandwidth.

In general, higher bit rate presentations may result in higher quality video playback, while lower bit rate presentations may provide sufficient quality video playback as the available network bandwidth decreases. Thus, when the available network bandwidth is relatively high, the retrieving unit 52 may retrieve data from a presentation at a relatively high bit rate, whereas when the available network bandwidth is low, the retrieving unit 52 may retrieve data from a presentation at a relatively low bit rate. In this manner, client device 40 may stream multimedia data over network 74 while also accommodating the varying network bandwidth availability of network 74.

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, retrieval unit 52 may submit a request to join a multicast network group associated with particular media content. After joining the multicast group, retrieval unit 52 may receive the data for the multicast group without making further requests to server device 60 or content preparation device 20. When the data of a multicast group is no longer needed, e.g., stopping playback or changing channels to a different multicast group, retrieval unit 52 may submit a request to leave the multicast group.

The network interface 54 may receive data of the segment of the selected presentation and provide it to the retrieving unit 52, which in turn may provide the segment to the decapsulating unit 50 by the retrieving unit 52. Decapsulation unit 50 may decapsulate elements of a video file into constituent PES streams (dependent PES streams), depacketize the PES streams to retrieve encoded data, and send the encoded data to audio decoder 46 or video decoder 48 depending on whether the encoded data is an audio stream or a portion of a video stream (e.g., as indicated by the PES packet header of the stream). Audio decoder 46 decodes encoded audio data and sends the decoded audio data to audio output 42, while video decoder 48 decodes encoded video data and sends the decoded video data (which may include multiple views of a stream) to video output 44.

Video encoder 28, video decoder 48, audio encoder 26, audio decoder 46, encapsulation unit 30, retrieval unit 52, and decapsulation unit 50 may each be implemented as any of a variety of suitable processing circuitry, as applicable, such as one or more microprocessors, Digital Signal Processors (DSPs), Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs), discrete logic circuitry, software, hardware, firmware, or any combinations thereof. Each of video encoder 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 encoder/decoder (CODEC). Likewise, each of 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. The apparatus including 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 (e.g., a cellular telephone).

Client device 40, server device 60, and/or content preparation device 20 may be configured to operate in accordance with the techniques of this disclosure. 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.

Encapsulation unit 30 may form a NAL unit that includes a header identifying the program to which the NAL unit belongs, as well as a payload, such as audio data, video data, or data describing the transmission or program stream to which the NAL unit corresponds. For example, in H.264/AVC, a NAL unit includes a 1-byte header and a variable-size payload. NAL units that include 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 slice of video data, or an entire picture of video data. Encapsulation unit 30 may receive encoded video data from video encoder 28 in the form of PES packets of an elementary stream. The encapsulation unit 30 may associate each elementary stream with a corresponding program.

Encapsulation unit 30 may also assemble access units from multiple NAL units. In general, an access unit may include one or more NAL units for presenting a frame of video data, as well as audio data corresponding to the frame (when such audio data is available). An access unit typically includes all NAL units for one output time instance, e.g., all audio and video data for one time instance. For example, if the frame rate of each view is 20 frames per second (fps), each time instance may correspond to a time interval of 0.05 seconds. During this time interval, a particular frame of all views of the same access unit (same time instance) may be rendered simultaneously. In one example, an access unit may include a coded picture, which may be presented as a primary coded picture, at one instance in time.

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

The media presentation may include a Media Presentation Description (MPD) that may contain descriptions of different alternative presentations (e.g., video services with different qualities), and the descriptions may include, for example, codec information, profile values, and level values. An MPD is an example of a manifest file (e.g., manifest file 66). Client device 40 may retrieve the MPD for the media presentation to determine how to access various presented movie fragments. The movie fragment may be located in a movie fragment box (moof box) of the video file.

Manifest file 66 (which may include, for example, an MPD) may advertise the availability of segments for presentation 68. That is, the MPD may include information indicative of the wall clock time at which the first segment of one of the presentations 68 becomes available, and information indicative of the duration of the segments within the presentation 68. In this way, retrieval unit 52 of client device 40 may determine when each segment is available based on the start time and the duration of the segment preceding the particular segment.

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

Network interface 54 may receive NAL units or access units via network 74 and provide the NAL units or access units to decapsulation unit 50 via retrieval unit 52. Decapsulation unit 50 may decapsulate elements of a video file into constituent PES streams, depacketize the PES streams to retrieve encoded data, and send the encoded data to audio decoder 46 or video decoder 48 depending on whether the encoded data is an audio stream or a portion of a video stream (e.g., as indicated by the PES packet header of the stream). Audio decoder 46 decodes encoded audio data and sends the decoded audio data to audio output 42, while video decoder 48 decodes encoded video data and sends the decoded video data (which may include multiple views of a stream) to video output 44.

In accordance with the techniques of this disclosure, the media presentation may have associated playback recommendations for a higher quality user experience, as discussed in more detail below. For example, for a real-time event, it may be desirable to view the event as quickly as possible, such as a sporting event or a news event. For real-time events, it is generally desirable to minimize the latency between the occurrence of the event and the transmission, reception, and playback of the media data presenting the event. Content preparation device 20 (e.g., encapsulation unit 30) may prepare a service description that specifies one or more target latencies (e.g., a desired end-to-end latency) and techniques for implementing the latency. For example, content preparation device 20 may indicate a playback acceleration or deceleration rate in the service description that client device 40 may use to adjust the playback rate to maintain a desired end-to-end latency without negatively impacting the playback of the user experience.

Accordingly, client device 40 (e.g., retrieval unit 52) may adjust playback according to the service description to achieve a desired end-to-end latency. For example, if the buffer of the memory of the retrieval unit 52 fills slowly with respect to playback, the retrieval unit 52 may slow down the playback rate according to the service description. Conversely, if the buffer fills too fast, the retrieval unit 52 may speed up the playback rate according to the service description.

The retrieval unit 52 may also use the service description to determine joining behavior for the media presentation. For example, if the media presentation is a real-time event, retrieval unit 52 may determine that the service description indicates a join behavior that is joined at the real-time edge of the media presentation (i.e., at the point in the media presentation where media data is most recently available) rather than at the beginning of the media presentation. The service description may also specify perceived quality of the media presentation associated with various latencies, as well as a target latency associated with the device type of client device 40 (e.g., whether client device 40 is a cellular phone, computer terminal, television, projector, etc.).

In this manner, client device 40 represents an example of a device for retrieving media data that includes a memory configured to store media data for a media presentation; and one or more processors implemented in the circuitry and configured to: retrieving a service description comprising data comprising one or more playback preferences for the media presentation, the playback preferences comprising an expected end-to-end latency; retrieving media data of a media presentation via a network streaming protocol; and rendering the retrieved media data according to the one or more playback preferences to achieve the desired end-to-end latency.

Likewise, content preparation device 20 and server device 60 represent examples of devices for transmitting media data, including a memory configured to store media data for a media presentation and a service description including one or more playback preferences for the media presentation, the playback preferences including an expected end-to-end latency; and one or more processors implemented in the circuitry and configured to: sending the service description to the client device; receiving a request for media data of a media presentation from a client device; and transmitting media data of the media presentation to the client device in response to a request for the media data from the client device to achieve a desired end-to-end latency according to the one or more playback preferences.

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

In this example, the eMBMS middleware unit 100 also includes an eMBMS reception unit 106, a cache 104, and a proxy server unit 102. In this example, the eMBMS reception unit 106 is configured to receive data via eMBMS, for example, according to file Delivery over Unidirectional Transport (FLUTE) described in the following document: paila et al, "FLUTE-file delivery over unidirectional transport," network working group, RFC6726, month 11 2012, available at tools. That is, the eMBMS reception unit 106 may receive the file via broadcast from, for example, the server device 60, which server device 60 may act as a broadcast/multicast service center (BM-SC).

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

Proxy server element 102 may act as a server for DASH client 110. For example, proxy server element 102 may provide an MPD file or other manifest file to DASH client 110. The proxy server element 102 may advertise the time of availability of segments in the MPD file and hyperlinks from which the segments may be retrieved. These hyperlinks may include a local host address prefix (e.g., 127.0.0.1 for IPv 4) corresponding to client device 40. In this manner, DASH client 110 may request segments from proxy server element 102 using HTTP GET or partial GET requests. For example, for segments available in the link HTTP://127.0.0.1/rep1/seg3, 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 proxy unit 102. Proxy server element 102 may, in response to such a request, retrieve the requested data from cache 104 and provide the data to DASH client 110. Alternatively, DASH client 110 may retrieve the media data from a server device (e.g., server device 60) via unicast. DASH client 110 may use cache 104 as a buffer for storing retrieved media data until the media data is ready to be played.

Fig. 3 is a conceptual diagram illustrating elements of an example multimedia content 120. The multimedia content 120 may correspond to the multimedia content 64 (fig. 1) or another multimedia content stored in the storage medium 62. In the example of FIG. 3, multimedia content 120 includes a Media Presentation Description (MPD)122 and a plurality of presentations 124A-124N (presentation 124). Presentation 124A includes optional header data 126 and segments 128A-128N (segment 128), while presentation 124N includes optional header data 130 and segments 132A-132N (segment 132). For convenience, the letter N is used to designate the last movie fragment in each presentation 124. In some examples, there may be different numbers of movie fragments between presentations 124.

MPD 122 may include a data structure separate from presentation 124. MPD 122 may correspond to manifest file 66 of fig. 1. Likewise, presentation 124 may correspond to presentation 68 of FIG. 1. In general, MPD 122 may include data that generally describes characteristics of presentation 124, such as encoding and rendering characteristics, adaptation sets, profiles to which MPD 122 corresponds, text type information, camera angle information, rating information, trick mode information (e.g., information indicating a presentation including a temporal subsequence), and/or information for retrieving remote time periods (e.g., for inserting targeted advertisements into media content during playback).

The header data 126 (if present) may describe characteristics of the segment 128, such as the temporal location of a Random Access Point (RAP), also known as a Stream Access Point (SAP), which of the segments 128 includes a random access point, a byte offset to a random access point within the segment 128, a Uniform Resource Locator (URL) of the segment 128, or other aspects of the segment 128. Header data 130 (if present) may describe similar characteristics of segment 132. Additionally or alternatively, such features may be included entirely within MPD 122.

The segments 128, 132 comprise one or more encoded video samples, each of which may comprise a frame or slice of video data. Each encoded video sample of segment 128 may have similar characteristics, e.g., height, width, and bandwidth requirements. Although such data is not shown in the example of fig. 3, such features may be described by data of MPD 122. MPD 122 may include features as described in the 3GPP specifications and add any or all of the signaling information described in this disclosure.

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

In accordance with the techniques of this disclosure, MPD 122 may include data such as xlink parameters that define the network location of the service description parameter data, as discussed in more detail below. Alternatively, MPD 122 may include the service description itself.

Fig. 4 is a block diagram illustrating elements of an example video file 150, which may correspond to a segment of a presentation, such as one of the segments 128, 132 of fig. 3. Each of the segments 128, 132 may include data that substantially conforms to the arrangement of data shown in the example of fig. 4. It can be said that the video file 150 encapsulates the segments. As described above, video files according to the ISO base media file format and its extensions store data in a series of objects called "boxes". In the example of fig. 4, the video file 150 includes a File Type (FTYP) box 152, a Movie (MOOV) box 154, a segment index (sidx) box 162, a movie fragment (MOOF) box 164, and a Movie Fragment Random Access (MFRA) box 166. Although fig. 4 represents an example of a video file, it should be understood that other media files may include other types of media data (e.g., audio data, timed text data, etc.) similar to the data constructs of video file 150, in accordance with the ISO base media file format and extensions thereof.

A File Type (FTYP) box 152 generally describes the file type of video file 150. File type box 152 may include data identifying specifications describing the best use of video file 150. File type box 152 may alternatively be placed before MOOV box 154, movie fragment box 164, and/or MFRA box 166.

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 corresponding to a presentation including video file 150 is to be updated, and information for updating the MPD. For example, the MPD update box may provide a URI or URL for updating the resources of the MPD. As another example, the MPD update box may include data for updating the MPD. In some examples, the MPD update box may immediately follow a Segment Type (STYP) box (not shown) of video file 150, where the STYP box may define the segment type of video file 150.

In the example of fig. 4, MOOV box 154 includes a movie header (MVHD) box 156, a Track (TRAK) box 158, and one or more movie extensions (MVEX) boxes 160. In general, MVHD box 156 may describe general characteristics of video file 150. For example, MVHD box 156 may include data describing the time at which video file 150 was originally created, the time at which video file 150 was last modified, a time scale for video file 150, the duration of playback of video file 150, or other data generally describing video file 150.

TRAK box 158 may include data for a track of video file 150. TRAK box 158 may include a track header (TKHD) box that describes characteristics of the track corresponding to TRAK box 158. In some examples, TRAK box 158 may include encoded video pictures, while in other examples, encoded video pictures of a track may be included in movie fragments 164, movie fragments 164 may be referenced by data of TRAK box 158 and/or sidx box 162.

In some examples, video file 150 may include more than one track. Thus, MOOV box 154 may include a number of TRAK boxes equal to the number of tracks in video file 150. TRAK box 158 may describe characteristics of a corresponding track of video file 150. For example, TRAK box 158 may describe temporal and/or spatial information for the corresponding track. When encapsulation unit 30 (fig. 3) includes a parameter set track in a video file (e.g., 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 sequence level SEI messages in parameter set tracks within the TRAK box describing the parameter set tracks.

MVEX box 160 may describe characteristics of a corresponding movie fragment 164, e.g., signaling that video file 150 includes movie fragment 164 in addition to video data (if any) included within MOOV box 154. In the context of streaming video data, the encoded video pictures may be included in movie fragment 164, rather than in MOOV box 154. Thus, all encoded video samples may be included in movie fragment 164, rather than MOOV box 154.

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

As described above, the encapsulation unit 30 may store the set of sequence data in video samples that do not include the actual encoded video data. A video sample may generally correspond to an access unit that is a presentation of an encoded picture at a particular time instance. In the context of AVC, a coded picture includes one or more VCL NAL units that contain information, such as SEI messages, used to construct all the pixels of the access unit and other associated non-VCL NAL units. Thus, encapsulation unit 30 may include a sequence data set, which may include sequence level SEI messages, in one of movie fragments 164. Encapsulation unit 30 may also signal the presence of sequence data sets and/or sequence level SEI messages that are present in one of movie fragments 164 within one of MVEX boxes 160 corresponding to one of movie fragments 164.

The SIDX box 162 is an optional element of the video file 150. That is, a video file that conforms to the 3GPP file format or other such file format does not necessarily include the SIDX box 162. According to an example of a 3GPP file format, a SIDX box may be used to identify sub-segments of a segment (e.g., a segment contained within video file 150). The 3GPP file format defines a sub-segment as a "self-contained set of one or more contiguous movie fragment boxes with corresponding media data box(s), and a media data box containing data referenced by a movie fragment box must be after that movie fragment box and before the next movie fragment box containing information about the same track. The "3 GPP file format also indicates that the SIDX box" contains a series of references to the sub-segments of the (sub-) segments recorded by the box. The referenced sub-segments are contiguous in presentation time. Also, the bytes referenced by the segment index box are always contiguous within a segment. The size of the reference gives a count of the number of bytes in the referenced material. "

The SIDX box 162 generally provides information representing one or more sub-segments of a segment included in the video file 150. For example, such information may include playback time at which the sub-segment begins and/or ends, byte offset of the sub-segment, whether the sub-segment includes (e.g., from a stream access point) a Stream Access Point (SAP), type of the SAP (e.g., whether the SAP is an Instantaneous Decoder Refresh (IDR) picture, a Clean Random Access (CRA) picture, a Broken Link Access (BLA) picture, etc.), location of the SAP in the sub-segment (according to playback time and/or byte offset), and so forth.

Movie fragment 164 may include one or more encoded video pictures. In some examples, a movie fragment 164 may include one or more groups of pictures (GOPs), each of which may include multiple encoded video pictures, e.g., frames or pictures. Additionally, as described above, in some examples, movie fragments 164 may include a set of sequence data. Each of the movie fragments 164 may include a movie fragment header box (mfhd) (not shown in fig. 4). The MFHD box may describe characteristics of the corresponding movie fragment, such as a sequence number of the movie fragment. Movie fragments 164 may be included in video file 150 in order of sequence number.

MFRA box 166 may describe random access points within movie fragment 164 of video file 150. This can be useful in performing trick modes such as performing a search for a particular temporal location (i.e., playback time) within a segment encapsulated by video file 150. In some examples, MFRA box 166 is generally optional and need not be included in a video file. Likewise, a client device (e.g., client device 40) does 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 number of Track Fragment Random Access (TFRA) boxes (not shown) 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.

In some examples, movie fragment 164 may include one or more Stream Access Points (SAPs), such as IDR pictures. Likewise, MFRA box 166 may provide an indication of a location within video file 150 of the SAP. Thus, a temporal subsequence of video file 150 may be formed from the SAP of video file 150. The temporal sub-sequence may also include other pictures, such as SAP-dependent P-frames and/or B-frames. The frames and/or slices of the temporal sub-sequence may be arranged within the segment such that frames/slices of the temporal sub-sequence that depend on other frames/slices of the sub-sequence may be decoded appropriately. For example, in a hierarchical arrangement of data, data for prediction of other data may also be included in the temporal sub-sequence.

Fig. 5 is a conceptual diagram illustrating an example architecture 200 that includes various devices and units that may perform the techniques of this disclosure. Specifically, architecture 200 includes server-side devices and elements, including an Adaptive Bit Rate (ABR) encoder, an encryption and CMAF wrapper device 206, an MPD generation and DASH wrapper device 208, an origin server device 210, a session-based MPD modification device 204, and a cdn (https) device 212. Architecture 200 also includes two example sets of client-side devices and units. As one example, the first client device includes a low-latency DASH client unit 214, a file format parsing (CMAF) unit 216, a decryption unit 218, and a decoding unit 220. As another example, the second client device includes a conventional DASH client unit 222, a file format parsing unit 224, a decryption unit 226, and a decoding unit 228.

The devices and units of fig. 5 may correspond to the devices and units of fig. 1. For example, the ABR encoder, encryption and CMAF packetization device 206, and MPD generation and DASH packetization device 208 (and in some cases, source server device 210) of fig. 5 may collectively correspond to the content preparation device 20 of fig. 1. The cdn (https) device 212 of fig. 5 may correspond to the server device 60 of fig. 1. The various DASH clients 214, 222, file format parsing units 216, 224, decryption units 218, 226 and decoding units 220, 228 of fig. 5 may correspond to various components of client device 40 of fig. 1, such as retrieval unit 52, decapsulation unit 50, audio decoder 46 and video decoder 48.

In the example of fig. 5, the ABR encoder, encryption, and CMAF packetization apparatus 206 may, for example, generate Common Media Application Format (CMAF)/DASH segments. MPD generation and DASH encapsulation device 208 generates the MPD and publishes the data as DASH segments on source server device 210. Based on information in the MPD, DASH client units 214, 222 may initiate their streaming logic and playback. The conventional DASH client unit 222 may play the media presentation with a delay of, for example, 10 seconds based on its buffering logic. However, low-latency DASH client unit 214 may identify that it can reduce end-to-end latency to provide a better streaming experience. Conventional DASH clients may also be used for a catch-up service.

Fig. 6 is a conceptual diagram illustrating example operation of the DASH encapsulation device 252 in an example low latency mode in accordance with the techniques of this disclosure. In this example, DASH wrapper device 252 wraps the CMAF header (CMAF header, CH), CMAF non-initial chunk (CNC) and CMAF Initial Chunk (CIC) into a DASH segment that includes the corresponding HTTP chunk. That is, ISO BMFF movie fragments or CMAF chunks are generated and then mapped to HTTP chunks by the DASH wrapper 252. DASH clients (e.g., conventional DASH client unit 254 and low-latency DASH client unit 256) request full segments, but DASH encapsulation device 252 may begin delivering segments earlier than its full availability. In particular, DASH encapsulation device 252 may provide the segments to CDN device 262, and CDN device 262 may store the segments and provide the DASH segments to DASH clients 254, 256 in response to HTTP requests for the segments from DASH clients 254, 256.

A DASH low-latency technical overview beyond conventional operation includes:

there are multiple movie fragments per segment to be able to generate and provide earlier portions of the segment onto the CDN.

Chunk duration is one deployment option, but examples include: 1 frame, 320ms, "mini GOP".

Signaling early availability in MPD

Support in DASH MPD for using the @ availabilityTimeOffset and @ availablityComplete attributes, which signal the early availability of a segment compared to the nominal availability time.

Use @ duration and $ Number $ for signaling URL and availability time

The present disclosure recognizes the problem of segmenting a timeline, which requires that the duration of the segment be known and published.

Acquisition time of Signaling Notification frame and prtf

This is discussed in amd.5 of DASH.

HTTP chunked transport encoding of partially available files

Support Emsg resolution

Omicron can be used for MPD update.

Omicron may be used to signal sparse metadata.

Real-time and low-latency DRM and encryption

Omicron can be used to ensure that license acquisition can be done under latency constraints and not overloaded in the network infrastructure.

Consider the signalling of missing or inappropriate content

This is discussed in amd.5 of DASH.

Accelerated playback in a device to solve both low latency and fast startup problems

This can be used to ensure that latency can be maintained without sacrificing channel access.

HTTP variants, e.g., supporting queued requests.

Explicit signaling (format signaling and/or protocol) of low latency mode.

In DASH deployments, DASH clients have important control over algorithms and user perception of DASH services. The DASH client may, for example, determine to use a rate adaptation algorithm, a buffer policy, a buffer duration, and the resulting latency and channel change time. However, by leaving all decisions to DASH clients, this may lead to inconsistent behavior, as different client implementations may, for example, select different policies. Thus, as an example, significantly different latencies may be observed for the same service on different DASH clients.

Fig. 7 is a conceptual diagram illustrating an example DASH client configuration in accordance with the techniques of this disclosure. Fig. 7 depicts an encoder and DASH encapsulation device 280 (which may correspond to content preparation device 20 of fig. 1), a CDN device 282 (which may correspond to server device 60 of fig. 1), and a low-latency DASH client unit 286 (which may correspond to retrieval unit 52 of client device 40 of fig. 1). In this example, encoder and DASH encapsulation device 280 prepares CNC and CIC including segments of HTTP chunks and provides these segments to CDN device 282. CDN device 282 provides the segments (or HTTP chunks thereof) to low-latency DASH client unit 286 in response to HTTP requests for the segments or HTTP chunks.

Where the application controls playback of the media presentation service, the application may also control the low-latency DASH client unit 286. As an example, fig. 7 illustrates integrating a low-latency DASH client unit 286 (e.g., a DASH. Js in the current implementation 2.9.0 supports a set of APIs that applications can use to set clients to low latency mode and determine latency. In the example of fig. 7, the delay is set to 1, indicating a target of 1 second. This setting resulted in a delay of 2.2 seconds in the test run.

This scenario may result in the service being provided to a deployment of different DASH client implementations:

application-based solutions are not always reliable because some environments, for example, work without an application, or an application cannot access a DASH client. Furthermore, the DASH client API may be different and have no general solution and no way to set parameters.

DASH clients need to make complex decisions based on information from service offerings, device functions, user interactions, and network states. Such information may not always be consistently expressed.

The service provider wants to express the desired service awareness that supports/forces DASH clients to properly perform rate adaptation.

It would therefore be beneficial to define service parameters more consistently and enable the transmission of these service parameters as part of a manifest file (e.g., MPD). The use of clients for service parameters may depend on the implementation of the client, but it is also possible to place higher requirements on the client to meet such service parameters in certain application criteria. In accordance with techniques of this disclosure, the encoder and DASH encapsulation device 280 may prepare a service description that includes playback preferences, such as an expected end-to-end latency between CDN device 282 and low-latency DASH client unit 286 (or between the encoder and DASH encapsulation device 280 and low-latency DASH client unit 286).

The following use case may be considered a service configuration, which may be expressed in the playback preferences of the service description:

1. the service has an expected end-to-end latency, whereby the content contains anchors that map media time to wall clock time (or any other time reference that a DASH client can access), so the DASH client plays back the service at this latency.

2. From a minimum, the service may gradually degrade with delay. For example, at a latency of 3.5 seconds, the quality may be considered high, at a latency of 10 seconds, the quality may be considered medium, and at a latency of 30 seconds, the quality in real-time consumption may be considered low.

3. In a real-time scenario, the service may request that in the event of re-buffering, the service return to the real-time delay as soon as possible, rather than delaying the service. In another case, the service may preferably not jump back to the real-time edge.

4. There is another service that may attempt to synchronize with another device and that is only valuable if it maintains a certain latency. The quality of service may be useless if the latency is greater than the latency of the request.

5. The service product may provide a desired access time or may provide a degradation in quality during the service access time.

6. The service is a UHD service and the quality of service is judged from the selected presentation and adaptation set, possibly over time.

7. The service has a variety of products, for example, offered in Standard Definition (SD), High Definition (HD), and Ultra High Definition (UHD). Depending on the device functionality (e.g., device display resolution), the client wishes to select a matching adaptation set.

8. Similar aspects may be considered for audio. Depending on the loudspeaker layout, a dedicated adaptation set should be selected.

9. The quality of service may be described in terms of the maximum re-buffering percentage that the client should observe, or a quality degradation may be provided over the re-buffering rate.

10. The service may allow accelerated or decelerated playback of media to compensate for buffer problems. The maximum acceleration/deceleration allowed may be specified.

Thus, the encoder and DASH encapsulation device 280 may prepare a service description that includes playback preferences, e.g., expected end-to-end latency, that represent any or all of the configuration data discussed above. The low-latency DASH client unit 286 may use the service description and its playback preferences to control playback, e.g., to achieve a desired end-to-end latency. For example, the low-latency DASH client unit 286 may retrieve segments or HTTP chunks and store the segments or chunks to a buffer in memory, such as the cache 104 shown in fig. 2. Low-latency DASH client unit 286 may also determine whether the buffer is emptied faster or slower than the buffer is filled. If the buffer is emptied faster than the buffer is filled, the low-latency DASH client unit 286 may reduce the playback rate of the media data to avoid buffer underflow. If the buffer is emptied slower than the buffer is filled, the low-latency DASH client unit 286 may increase the playback rate of the media data to avoid buffer overflow. The low-latency DASH client unit 286 may use data signaled in a service description that specifies maximum and minimum accelerations/decelerations of media playback to ensure that such playback rate adjustments are within specified maximum and minimum ranges.

As another example, the expected end-to-end latency may be one of various specified target time delays. The encoder and DASH encapsulation device 280 may specify various qualities associated with each possible target delay. In this manner, low-latency DASH client unit 286 may select one of the target latencies associated with the desired playback quality and retrieve and play back media data associated with the selected target latency.

Low latency DASH client unit 286 may further determine whether to continue playback from where playback was interrupted or to jump forward to a real-time edge in response to a re-buffering event (i.e., an interruption in playback). The real-time edges represent the most recently available portions of media data that can be retrieved and presented. The encoder and DASH-encapsulation device 280 may specify which of these actions is recommended in the service description.

In some examples, encoder and DASH wrapper device 280 may specify whether one or more client devices should playback synchronously (e.g., if multiple displays are displaying the same real-time content, such as a sporting event or a newsworthy event that is occurring in real-time). Such synchronization is only possible if all synchronized devices use the same delay. The encoder and DASH packetizing device 280 may specify such delays for synchronization. Thus, low-latency DASH client unit 286 may determine whether to synchronize playback with one or more other client devices and, if so, use one of the latencies specified for synchronization as the expected end-to-end latency.

Other aspects may be considered and some scalability or proprietary signaling may be considered.

The degradation in quality may be represented, for example, by a Mean Opinion Score (MOS) score, or may be represented as an abstract point scale, for example, from 0 (unusable quality) to 100 (perfect quality).

In accordance with the techniques of this disclosure, low-latency DASH client unit 286 may use one or more of these parameters for static selection of content and dynamic operation for playback to create utility functions that account for different dimensions of different service products (service provisioning).

DASH clients (e.g., retrieval unit 52 of fig. 1, DASH client 110 of fig. 2, or the various DASH clients of fig. 5-7) and source devices (e.g., content preparation device 20 and server device 60, or the various servers and source devices of fig. 5-7) may be configured to use the techniques of this disclosure. In general, the techniques of this disclosure:

define a well-defined set of service description parameters that reflect the actual use cases, and which DASH clients can use to follow these techniques.

Define the mapping of service description to MPD signaling in DASH. The service description may be provided as a URL, for example as an xlink. This avoids the need for MPD updates to repeatedly retrieve data. The information should be static during the real time of the media presentation.

Define an extension mechanism so that service signaling can be added according to server and client protocols.

Define a simple DASH reference client description to show how to use such information in DASH operations.

In accordance with the techniques of this disclosure, any or all of the following parameters may be included in the service description parameters:

service type: providing description of service types

Omicron, real-time: the client only desires to track the real-time edges.

Omicron real-time and supplementary watch (cathtup): the service expects that real-time edges will be tracked, but can also be used as a lookaside.

Omicron is given in benefit: the service is converted from a real-time service, but all media is available

On-demand: the service is an on-demand service.

Unknown: the type of service is unknown.

Omicron base (Cardinality): 0 … 1

Add action type

Omicron real-time edge: clients expect to join at the real-time edge.

-a first time period: the client desires to join during a first time period.

Unknown: the client makes the selection according to the client or other information.

Omicron base: 0 … 1

Real-time latency property:

minimum time delay of omicron

Omicron maximum time delay

-desired time delay

Set of omicron pairs (pair) (delay and quality)

Omicron base: 0 … 1

Rebuffering Properties

Maximum percent rebuffering

Desired percent rebuffering

Omicron as set of pairs (rebuffering percentage and latency)

Omicron base: 0 … 1

Random access time

Desired random access time

Omicron maximum random access time

Set of omicron pairs (random access time and quality)

Omicron base: 0 … 1

Quality of service for device type (can be updated for each time period)

Device properties

Display resolution

Omicron other device type elements

Omicron pair (selected presentation id and quality)

Omicron base: 0 … N

Accelerated playback

Omicron max

Omicron minimum

Maximum percentage of o

Omicron base: 0 … 1

Service parameters

Omicron chemeldURI and value

O follows DASH descriptor logic

Fig. 8 is a flow diagram illustrating an example method of sending media data to a client device in accordance with the techniques of this disclosure. The method of fig. 8 is explained with respect to content preparation device 20 of fig. 1. However, it should be understood that other devices, such as server device 60 of FIG. 1, may be configured to perform these or other similar techniques, either alone or in conjunction with content preparation device 20. For example, the MPD generation and DASH encapsulation device 208, the source service device 210, and the cdn (https) device 212 of fig. 5 may collectively perform corresponding portions of the method of fig. 8. As another example, DASH encapsulation device 252 and CDN device 262 of fig. 6 may jointly perform corresponding portions of the method of fig. 8. As another example, encoder and DASH encapsulation device 280 and CDN device 282 may jointly perform corresponding portions of the method of fig. 8.

In this example, content preparation device 20 initially receives data defining playback preferences for a media presentation, for example, from an administrator or other user (300). Such playback preferences may include one or more latencies for media presentation, as well as other attributes that enable those latencies. Content preparation device 20 may then prepare a service description specifying playback preferences (302). For example, as described above, content preparation device 20 may build a service description to specify a service type, such as real-time, real-time and review, or on-demand. As another example, content preparation device 20 may build a service description to specify join behavior, such as joining at a real-time edge or at a first available time period. As another example, content preparation device 20 may construct a service description to specify latency attributes, such as a minimum latency and/or a maximum latency, one or more target latencies, and in some cases, a corresponding quality for specifying the target latency.

As another example, content preparation device 20 may construct a service description to specify rebuffering attributes, such as a maximum rebuffering percentage and a desired rebuffering percentage, and in some examples, a corresponding latency for the rebuffering percentage. As another example, content preparation device 20 may construct a service description to specify a random access time, such as a desired random access time and/or a maximum random access time, and, in some examples, an associated quality. As another example, content preparation device 20 may construct a service description to specify a quality of service based on the device type, such as a characteristic of the device (e.g., display resolution) and a corresponding desired quality for each type of device.

In some examples, content preparation device 20 may construct the service description to specify acceleration or deceleration of the playback rate information, such as maximum acceleration, minimum acceleration (i.e., maximum deceleration), and/or a playback rate adjustment percentage. Such playback rate adjustments may be set to prevent client device buffer overflows and underflows without unduly affecting the perceived quality of media playback. The content preparation device 20 may construct a service description to specify various parameters as schemelduri and values according to DASH descriptor logic.

Content preparation device 20 may then send the service description to a client device, such as client device 40 (fig. 1) (304). Content preparation device 20 may send the service description via server device 60. In some examples, content preparation device 20 may send the service description to a different network location and specify a URL or other identifier for the network location of the service description in a manifest file (e.g., MPD). Content preparation device 20 may then receive a request for media data from the client device (306), and send the requested media data to the client device according to the service parameters specified in the service description (308) to achieve the desired end-to-end latency.

In this manner, the method of fig. 8 represents an example of a method of sending media that includes sending, to a client device, a service description that includes data that includes one or more playback preferences for a corresponding media presentation, the playback preferences including an expected end-to-end latency; receiving a request for media data of a media presentation from a client device; media data of the media presentation is sent to the client device in response to a request for the media data from the client device to achieve a desired end-to-end latency in accordance with the one or more playback preferences.

Fig. 9 is a flow diagram illustrating an example method of retrieving media data in accordance with the techniques of this disclosure. The method of fig. 9 is explained with respect to the client device 40 of fig. 1. However, it should be understood that other devices may be configured to perform this or similar methods. For example, low-latency DASH client unit 214 of fig. 5, conventional DASH client unit 222 of fig. 5, conventional DASH client unit 254 of fig. 6, low-latency DASH client unit 256 of fig. 6, or low-latency DASH client unit 286 of fig. 7 may be configured to perform this or similar methods in accordance with the techniques of this disclosure.

In this example, retrieval unit 52 of client device 40 receives a service description specifying playback preferences for the media presentation (320). For example, retrieval unit 52 may initially retrieve a manifest file (e.g., an MPD), such as manifest file 66 of fig. 1 or MPD 122 of fig. 3. The manifest file may include a service description. Alternatively, the manifest file may specify a network location from which the service description may be retrieved, and the client device 40 may retrieve the service description, for example, by dereferencing the xlink parameter of the manifest file.

Retrieval unit 52 may then determine a desired end-to-end delay for the media presentation from the service description (322). For example, the service description may specify one or more target latencies, which may include maximum and/or minimum latencies. The service description may (additionally or alternatively) specify corresponding quality levels for various latencies. In some examples, the service description may specify various latencies associated with various types of client devices (e.g., cell phones, computer terminals, televisions, projectors, etc.). Additionally, the service description may specify techniques for performing playback to achieve and maintain a target latency, such as maximum and minimum playback acceleration (or deceleration) values. The service description may also specify other playback preferences as described above, such as join behavior, rebuffering behavior, and the like.

Accordingly, retrieval unit 52 may request the media data according to the playback preferences (324) and may play back the media data according to the playback preferences (326). For example, assuming that the service description specifies a desired end-to-end latency and a playback acceleration/deceleration rate to achieve the desired end-to-end latency, retrieval unit 52 may retrieve and buffer the media data in memory (e.g., cache 104 of fig. 2). During playback, the retrieval unit 52 may speed up or slow down playback depending on whether the buffer is being filled or emptied too quickly. As described above, if the buffer is filled too fast, the retrieval unit 52 may speed up the playback rate, whereas if the buffer is emptied too fast, the retrieval unit 52 may slow down the playback rate within the signaled playback speed up/down rate of the service description.

As another example, if a re-buffering event occurs, retrieval unit 52 may determine from the service description whether to resume playback from where playback was interrupted or at a real-time edge of the media presentation. Similarly, the retrieval unit 52 may determine, upon initial access to the media presentation, whether to access the earliest time period of availability of the media presentation or the real-time edge of the media presentation.

In this manner, the method of fig. 9 represents an example of a method of retrieving media data, the method comprising: retrieving a service description comprising data comprising one or more playback preferences for a corresponding media presentation, the playback preferences comprising a desired end-to-end latency; retrieving media data of a media presentation via a network streaming protocol; and rendering the retrieved media data according to the one or more playback preferences to achieve the desired end-to-end latency.

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

By way of example, and not limitation, such computer-readable storage media can comprise RAM, ROM, EEPROM, CD-ROM or other optical disk storage, magnetic disk storage or other magnetic storage devices, flash memory, or any other medium that can be used to store desired program code in the form of instructions or data structures and that can be accessed by a computer. Also, any connection is properly termed a computer-readable medium. For example, if the instructions are transmitted from a website, server, or other remote source using a coaxial cable, fiber optic cable, twisted pair, Digital Subscriber Line (DSL), or wireless technologies such as infrared, radio, and microwave, then the definition of medium includes coaxial cable, fiber optic cable, twisted pair, DSL, or wireless technologies such as infrared, radio, and microwave. It should be understood, however, that computer-readable storage media and data storage media do not include connections, carrier waves, signals, or other transitory media, but are instead directed to non-transitory, tangible storage media. Disk and disc, as used herein, includes Compact Disc (CD), laser disc, optical disc, Digital Versatile Disc (DVD), floppy disk and blu-ray disc where disks usually reproduce data magnetically, while discs reproduce data optically with lasers. Combinations of the above should also be included within the scope of computer-readable media.

The instructions may be executed by one or more processors, such as one or more Digital Signal Processors (DSPs), general purpose microprocessors, an Application Specific Integrated Circuits (ASICs), field programmable logic arrays (FPGAs), or other equivalent integrated or discrete logic circuitry. Thus, as used herein, the term "processor" may refer to any of the foregoing structure 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. Also, the techniques may be fully implemented in one or more circuits or logic elements.

The techniques of this disclosure may be implemented in a variety of devices or apparatuses including a wireless handset, an Integrated Circuit (IC), or a set of ICs (e.g., a chipset). Various components, modules, or units are described in this disclosure to emphasize functional aspects of devices configured to perform the disclosed techniques, but do not necessarily require implementation by different hardware units. Rather, as noted above, the various units may be combined in a codec hardware unit, or provided by a collection of interoperative hardware units, including one or more processors as described above in combination with suitable software and/or firmware.

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