阅读说明：本技术 媒体数据的网络流式传输的初始化集合 (Initialization set for network streaming of 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：一种用于检索媒体数据的设备包括：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被配置为：检索用于媒体呈现的清单文件,该清单文件包括用于初始化集合的数据,该初始化集合包括用于媒体呈现的整个持续时间的初始化参数；使用初始化集合初始化媒体呈现的媒体数据的回放；检索媒体呈现的媒体数据；并且根据初始化的回放呈现媒体数据。例如,初始化参数可以指定媒体呈现的图片的最大宽度或最大高度或媒体呈现的最大帧速率。因此,处理器可以处理小于或等于最大宽度/高度的任何尺寸的图片,或者等于或小于最大帧速率的媒体数据。(An apparatus for retrieving media data 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 manifest file for the media presentation, the manifest file comprising data for an initialization set, the initialization set comprising initialization parameters for an entire duration of the media presentation; initializing playback of media data of the media presentation using the initialization set; retrieving media data of a media presentation; and rendering the media data according to the initialized playback. For example, the initialization parameter may specify a maximum width or a maximum height of a picture of the media presentation or a maximum frame rate of the media presentation. Thus, the processor may process any size of picture that is less than or equal to the maximum width/height, or media data that is equal to or less than the maximum frame rate.)

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

retrieving a manifest file for a media presentation, the manifest file comprising data for an initialization set, the initialization set comprising initialization parameters for an entire duration of the media presentation;

initializing playback of media data of the media presentation using the initialization set;

retrieving the media data of the media presentation; and

rendering the media data according to the initialized playback.

2. The method of claim 1, wherein the media presentation comprises a plurality of time periods, each of the time periods comprising an adaptation set having a presentation comprising media data that can be presented using the initialization parameters of the initialization set and the initialized playback, the method further comprising determining the presentation of the time periods comprising the media data that can be presented using the initialization parameters and the playback initialized using data of the manifest file.

3. The method of claim 2, wherein the manifest file includes an initialization set reference attribute in at least one of an adaptation set element or a presentation element, the initialization set reference attribute indicating the initialization set of the media data that may be used to present the presentation of the adaptation set.

4. The method of claim 1, wherein the initialization set comprises data identifying initialization segments for one or more media types of the media presentation.

5. The method of claim 4, wherein the data identifying the initialization segment comprises a Uniform Resource Locator (URL) of the initialization segment.

6. The method of claim 4, wherein the one or more media types comprise one or more of audio, video, or timed text.

7. The method of claim 1, wherein the initialization parameters specify one or more of a maximum width of a picture of the media presentation or a maximum height of the picture of the media presentation, and wherein retrieving the media data comprises:

retrieving first media data of the media presentation for a first playback time, the first media data comprising a picture having at least one of the maximum width or the maximum height; and

retrieving second media data for the media presentation for a second playback time, the second playback time being different from the first playback time, and the second media data being different from the first media data, and the second media data comprising a picture having less than the maximum width and the maximum height.

8. The method of claim 1, wherein the initialization parameter specifies a maximum frame rate of the media presentation, and wherein retrieving the media data comprises:

retrieving first media data of the media presentation for a first playback time, the first media data having the maximum frame rate; and

retrieving second media data of the media presentation for a second playback time, the second playback time being different from the first playback time, and the second media data being different from the first media data, and second media data having a frame rate that is less than the maximum frame rate.

9. The method of claim 1, wherein initializing the playback comprises: at least one of decryption, decoding, or rendering is initialized.

10. The method of claim 1, wherein the manifest file comprises a Media Presentation Description (MPD) for dynamic adaptive streaming over HTTP (DASH).

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 manifest file for the media presentation, the manifest file comprising data for an initialization set comprising initialization parameters for an entire duration of the media presentation;

initializing playback of the media data of the media presentation using the initialization set;

retrieving the media data of the media presentation; and

rendering the media data according to the initialized playback.

12. The device of claim 11, wherein the media presentation comprises a plurality of time periods, each of the time periods comprising an adaptation set having a presentation comprising media data that can be presented using the initialization parameters of the initialization set and the initialized playback, the method further comprising determining the presentation of the time periods comprising the media data that can be presented using the initialization parameters and the playback initialized using data of the manifest file.

13. The device of claim 11, wherein the initialization set comprises Uniform Resource Locators (URLs) of initialization segments of one or more media types of the media presentation.

14. The device of claim 11, wherein the initialization parameters specify one or more of a maximum width of a picture of the media presentation or a maximum height of the picture of the media presentation, and wherein to retrieve the media data, the one or more processors are configured to:

retrieving first media data of the media presentation for a first playback time, the first media data comprising a picture having at least one of the maximum width or the maximum height; and

retrieving second media data for the media presentation for a second playback time, the second playback time being different from the first playback time, and the second media data being different from the first media data, and the second media data comprising a picture having less than the maximum width and the maximum height.

15. The device of claim 11, wherein the initialization parameter specifies a maximum frame rate of the media presentation, and wherein to retrieve the media data, the one or more processors are configured to:

retrieving first media data of the media presentation for a first playback time, the first media data having the maximum frame rate; and

retrieving second media data of the media presentation for a second playback time, the second playback time being different from the first playback time, and the second media data being different from the first media data, and the second media data having a frame rate that is less than the maximum frame rate.

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

retrieving a manifest file for a media presentation, the manifest file comprising data for an initialization set, the initialization set comprising initialization parameters for an entire duration of the media presentation;

initializing playback of media data of the media presentation using the initialization set;

retrieving the media data of the media presentation; and

rendering the media data according to the initialized playback.

17. The computer-readable storage medium of claim 16, wherein the media presentation comprises a plurality of time periods, each of the time periods comprising an adaptation set having a presentation comprising media data that can be presented using the initialization parameters and the initialized playback of the initialization set, the method further comprising determining the presentation of the time period comprising the media data that can be presented using the initialization parameters and the playback initialized using data of the manifest file.

18. The computer-readable storage medium of claim 16, wherein the initialization parameters specify one or more of a maximum width of a picture of the media presentation or a maximum height of the picture of the media presentation, and wherein the instructions that cause the processor to retrieve the media data comprise instructions that cause the processor to:

retrieving first media data of the media presentation for a first playback time, the first media data comprising a picture having at least one of the maximum width or the maximum height; and

retrieving second media data for the media presentation for a second playback time, the second playback time being different from the first playback time, and the second media data being different from the first media data, and the second media data comprising a picture having less than the maximum width and the maximum height.

19. The computer-readable storage medium of claim 16, wherein the initialization parameter specifies a maximum frame rate of the media presentation, and wherein the instructions that cause the processor to retrieve the media data comprise instructions that cause the processor to:

retrieving first media data of the media presentation for a first playback time, the first media data having the maximum frame rate; and

retrieving second media data of the media presentation for a second playback time, the second playback time being different from the first playback time, and the second media data being different from the first media data, and second media data having a frame rate that is less than the maximum frame rate.

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

means for retrieving a manifest file for a media presentation, the manifest file comprising data for an initialization set, the initialization set comprising initialization parameters for an entire duration of the media presentation;

means for initializing playback of media data of the media presentation using the initialization set;

means for retrieving the media data of the media presentation; and

means for presenting the media data according to the initialized playback.

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

sending a manifest file for a media presentation to a client device, the manifest file comprising data for an initialization set comprising initialization parameters for an entire duration of the media presentation;

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

transmitting the requested media data to the client device.

22. The method of claim 21, wherein the media presentation comprises a plurality of time periods, each of the time periods comprising an adaptation set having a presentation comprising media data that may be initialized and presented using the initialization parameters of the initialization set.

23. The method of claim 22, wherein the manifest file includes an initialization set reference attribute in at least one of an adaptation set element or a presentation element, the initialization set reference attribute indicating the initialization set of the media data that may be used to present the presentation of the adaptation set.

24. The method of claim 21, wherein the initialization set comprises data identifying initialization segments for one or more media types of the media presentation.

25. The method of claim 24, wherein the data identifying the initialization segment comprises a Uniform Resource Locator (URL) of the initialization segment.

26. The method of claim 24, wherein the one or more media types include one or more of audio, video, or timed text.

27. The method of claim 21, wherein the initialization parameters specify one or more of a maximum width of a picture of the media presentation or a maximum height of the picture of the media presentation, and wherein sending the requested media data comprises:

sending first media data for the media presentation for a first playback time, the first media data comprising a picture having at least one of the maximum width or the maximum height; and

sending second media data for the media presentation for a second playback time, the second playback time being different from the first playback time, and the second media data being different from the first media data, and the second media data comprising a picture having less than the maximum width and the maximum height.

28. The method of claim 21, wherein the initialization parameter specifies a maximum frame rate of the media presentation, and wherein transmitting the media data comprises:

sending first media data of the media presentation for a first playback time, the first media data having the maximum frame rate; and

sending second media data for the media presentation for a second playback time, the second playback time being different from the first playback time, and the second media data being different from the first media data, and second media data having a frame rate that is less than the maximum frame rate.

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

a memory for storing media data for a media presentation; and

one or more processors implemented in circuitry and configured to:

sending a manifest file for the media presentation to a client device, the manifest file comprising data for an initialization set comprising initialization parameters for an entire duration of the media presentation;

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

transmitting the requested media data to the client device.

30. The device of claim 29, wherein the media presentation comprises a plurality of time periods, each of the time periods comprising an adaptation set having a presentation comprising media data that may be initialized and presented using the initialization parameters of the initialization set.

31. The device of claim 29, wherein the initialization set comprises Uniform Resource Locators (URLs) of initialization segments of one or more media types of the media presentation.

32. The device of claim 29, wherein the initialization parameters specify one or more of a maximum width of a picture of the media presentation or a maximum height of the picture of the media presentation, and wherein to transmit the requested media data, the one or more processors are configured to:

sending first media data for the media presentation for a first playback time, the first media data comprising a picture having at least one of the maximum width or the maximum height; and

sending second media data for the media presentation for a second playback time, the second playback time being different from the first playback time, and the second media data being different from the first media data, and the second media data comprising a picture having less than the maximum width and the maximum height.

33. The device of claim 29, wherein the initialization parameter specifies a maximum frame rate of the media presentation, and wherein to transmit the media data, the one or more processors are configured to:

sending first media data of the media presentation for a first playback time, the first media data having the maximum frame rate; and

sending second media data for the media presentation for a second playback time, the second playback time being different from the first playback time, and the second media data being different from the first media data, and second media data having a frame rate that is less than the maximum frame rate.

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

sending a manifest file for a media presentation to a client device, the manifest file comprising data for an initialization set comprising initialization parameters for an entire duration of the media presentation;

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

transmitting the requested media data to the client device.

35. The computer-readable storage medium of claim 34, wherein the media presentation comprises a plurality of time periods, each of the time periods comprising an adaptation set having a presentation comprising media data that may be initialized and presented using the initialization parameters of the initialization set.

36. The computer-readable storage medium of claim 34, wherein the initialization set comprises Uniform Resource Locators (URLs) of initialization segments of one or more media types of the media presentation.

37. The computer-readable storage medium of claim 34, wherein the initialization parameters specify one or more of a maximum width of a picture of the media presentation or a maximum height of the picture of the media presentation, and wherein the instructions that cause the processor to send the requested media data comprise instructions that cause the processor to:

sending first media data for the media presentation for a first playback time, the first media data comprising a picture having at least one of the maximum width or the maximum height; and

sending second media data for the media presentation for a second playback time, the second playback time being different from the first playback time, and the second media data being different from the first media data, and the second media data comprising a picture having less than the maximum width and the maximum height.

38. The computer-readable storage medium of claim 34, wherein the initialization parameter specifies a maximum frame rate of the media presentation, and wherein the instructions that cause the processor to transmit the media data comprise instructions that cause the processor to:

sending first media data of the media presentation for a first playback time, the first media data having the maximum frame rate; and

sending second media data for the media presentation for a second playback time, the second playback time being different from the first playback time, and the second media data being different from the first media data, and second media data having a frame rate that is less than the maximum frame rate.

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

means for sending a manifest file for a media presentation to a client device, the manifest file comprising data for an initialization set comprising initialization parameters for an entire duration of the media presentation;

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

means for sending the requested media data to the client device.

Technical Field

The present disclosure relates to storage and transmission of encoded media 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 signaling parameters for a media presentation. The parameters may be included in an initialization set, which may identify an initialization segment. The initialization set may define parameters that are not exceeded for the entire duration of the media presentation. In this manner, the client device may retrieve the initialization set of data once and use the initialization set of data to initialize various processes or environments (e.g., decryption, decoding, and rendering) without having to repeatedly retrieve the initialization set and/or reinitialize these processes or environments during playback of the media data for the media presentation. In this manner, the techniques may improve the field of media streaming because the techniques may reduce the processing time period associated with initialization, thereby reducing latency associated with rendering media data of a media presentation.

In one example, a method of retrieving media data includes: retrieving a manifest file for the media presentation, the manifest file comprising data for an initialization set, the initialization set comprising initialization parameters for an entire duration of the media presentation; initializing playback of media data of the media presentation using the initialization set; retrieving media data of a media presentation; the media data is presented according to the initialized playback.

In another example, an apparatus for retrieving media data comprises: 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 manifest file for the media presentation, the manifest file comprising data for an initialization set, the initialization set comprising initialization parameters for an entire duration of the media presentation; initializing playback of media data of the media presentation using the initialization set; retrieving media data of a media presentation; and rendering the media data according to the initialized playback.

In another example, a computer-readable storage medium has instructions stored thereon that, when executed, cause a processor to: retrieving a manifest file for the media presentation, the manifest file comprising data for an initialization set, the initialization set comprising initialization parameters for an entire duration of the media presentation; initializing playback of media data of the media presentation using the initialization set; retrieving media data of a media presentation; the media data is presented according to the initialized playback.

In another example, an apparatus for retrieving media data comprises: means for retrieving a manifest file for the media presentation, the manifest file comprising data for an initialization set, the initialization set comprising initialization parameters for an entire duration of the media presentation; means for initializing playback of media data of the media presentation using the initialization set; means for retrieving media data for a media presentation; means for presenting the media data according to the initialized playback.

In another example, a method of transmitting media data includes: sending a manifest file for the media presentation to the client device, the manifest file comprising data for an initialization set, the initialization set comprising initialization parameters for an entire duration of the media presentation; receiving a request for media data of a media presentation from a client device; and transmitting the requested media data to the client device.

In another example, an apparatus for transmitting media data includes: a memory for storing media data for a media presentation; and one or more processors implemented in the circuitry and configured to: sending a manifest file for the media presentation to the client device, the manifest file comprising data for an initialization set, the initialization set comprising initialization parameters for an entire duration of the media presentation; receiving a request for media data of a media presentation from a client device; and transmitting the requested media data to the client device.

In another example, a computer-readable storage medium has instructions stored thereon that, when executed, cause a processor to: sending a manifest file for the media presentation to the client device, the manifest file comprising data for an initialization set, the initialization set comprising initialization parameters for an entire duration of the media presentation; receiving a request for media data of a media presentation from a client device; and transmitting the requested media data to the client device.

In another example, an apparatus for transmitting media data includes: means for sending a manifest file for the media presentation to the client device, the manifest file comprising data for an initialization set, the initialization set comprising initialization parameters for an entire duration of the media presentation; means for receiving a request for media data of a media presentation from a client device; and means for sending the requested media data to the client device.

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.

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 DASH (Dynamic Adaptive Streaming over HTTP) client in accordance with the present technology.

Fig. 6 is a conceptual diagram illustrating an example of track buffer based playback.

Fig. 7 is a conceptual diagram illustrating an example content model for DASH multi-track media data in accordance with the present technology.

Fig. 8 is a flow diagram illustrating an example method of transmitting media data 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 sending initialization parameters using, for example, an initialization set. The initialization set may specify appropriate initializations for one or more media types of the media presentation. Thus, the time period of the media presentation should include at least one adaptation set, which can be played when initialized with the initialization set.

The techniques of this disclosure may be applied to video files that conform to video data encapsulated according to any of the ISO base media file format, Scalable Video Coding (SVC) file format, Advanced Video Coding (AVC) file format, third generation partnership project (3GPP) file format, and/or multi-view video coding (MVC) file format, or other similar video file formats.

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 can be provided for HTTP streaming, since a partial GET operation can retrieve one or more individual movie fragments. In a movie fragment, there may be track fragments of several 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).

Fig. 1 is a block diagram illustrating an example system 10 implementing techniques for streaming media data over a network in accordance with the techniques of this disclosure. 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 assumed by the syntax elements in the bitstream (e.g., the specified size of the decoded pictures). 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, such as a Media Presentation Descriptor (MPD) that describes characteristics of the 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 of the presentations 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 for adapting the scenes of the presentations in the sets, 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 representations 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 the retrieving unit 52 may provide the segment to the decapsulating unit 50. 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.

Content preparation device 20 may determine various maximum or invariant parameters for a media presentation (e.g., multimedia content 64) in a presentation 68 and/or adaptation set for the media presentation. For example, content preparation device 20 may determine a maximum width and a maximum height of pictures for a media presentation across presentation 68 and/or adaptation sets. As another example, content preparation device 20 may determine a maximum frame rate of video across presentation 68 and/or adaptation sets. The content preparation device 20 may construct an initialization segment for each type of media data (e.g., video, audio, timed text, etc.) such that the data of the initialization segment may be used to initialize all of the presentations 68 of the media presentation according to the determined maximum (width, height, frame rate, etc.).

In this manner, client device 40 may initialize playback of a media presentation at a time using the initialization segment, and then be able to perform playback of any presented media data from any adaptation set thereafter without re-initialization.

Content preparation device 20 may also signal data identifying the initialization segment in manifest file 66. For example, content preparation device 20 may build manifest file 66 to include an initialization set that signals various initialization parameters (e.g., maximum width, maximum height, maximum frame rate, etc.) and a Uniform Resource Locator (URL) that initializes the segment.

Accordingly, client device 40 may retrieve manifest file 66, determine the location of the initialization segment, retrieve the initialization segment, and then initialize playback of the media data of the media presentation (e.g., multimedia content 64). Client device 40 may then retrieve any rendered 68 media data and perform playback of the media data without reinitialization. For example, presentation 68A may have a picture with a specified maximum width and maximum height, and/or may have a maximum frame rate. The presentation 68N may have pictures that are less than a specified maximum width and maximum height, and/or may have pictures that are less than a maximum frame rate. Client device 40 may retrieve (and server device 60 and/or content preparation device 20 may send) media data for presentation 68A at a first playback time and retrieve media data for presentation 68N at a second, different playback time. However, client device 40 may perform playback of both sets of media data (i.e., from both presentation 68A and presentation 68N) without performing re-initialization.

In this manner, client device 40 represents an example of a device for retrieving media data, the device 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 manifest file for the media presentation, the manifest file comprising data for an initialization set, the initialization set comprising initialization parameters for an entire duration of the media presentation; initializing playback of media data of the media presentation using the initialization set; retrieving media data of a media presentation; and rendering the media data according to the initialized playback.

Likewise, the content preparation device 20 and the server device 60 represent examples of a device for transmitting media data, the device including: a memory for storing media data for a media presentation; and one or more processors implemented in the circuitry and configured to: sending a manifest file for the media presentation to the client device, the manifest file comprising data for an initialization set, the initialization set comprising initialization parameters for an entire duration of the media presentation; receiving a request for media data of a media presentation from a client device; and transmitting the requested media data to the client device.

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.

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 of the presentations 124. In some examples, there may be different numbers of movie fragments between presentations 124.

MPD122 may include a data structure separate from presentation 124. MPD122 may correspond to manifest file 66 of fig. 1. Likewise, presentation 124 may correspond to presentation 68 of FIG. 1. In general, MPD122 may include data that generally describes characteristics of presentation 124, such as encoding and rendering characteristics, adaptation sets, profiles to which MPD122 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. MPD122 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, MPD122 may include an initialization set, as discussed in more detail below. The initialization set may specify initialization parameters that may be used to initialize playback of any presentation 124 (i.e., media data of any of the segments 128, 132). For example, the initialization set may specify a maximum width and a maximum height of the picture of presentation 124 (i.e., segments 128, 132). As another example, the initialization set may additionally or alternatively specify a maximum frame rate of presentation 124. Thus, each of the presentations 124 may have a frame rate that is equal to or less than the maximum frame rate. Likewise, each of the presentations 124 may include a picture having less than or equal to a maximum width and/or a maximum height.

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 presents 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.) that construct data similar to 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 track data for 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 facilitate performing trick (puck) 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 DASH client 200 in accordance with the techniques of this disclosure. DASH client 200 of fig. 5 may correspond to or be included within retrieval unit 52 of fig. 1 or DASH client 110 of fig. 2. In this example, the DASH client 200 includes selection logic 202, a DASH access engine 204, and media engines 206A, 206B.

In other organizations, the DASH Industry Forum (DASH-IF) and the Consumer Technology Association (CTA) Web Application Video Ecosystem (CTA WAVE) have discussed the subject of media consistency playback based on the model shown in fig. 5, for which the DASH access engine 204 establishes media track buffers for each media type and uses segmentation in the environment. For example, the media types may include audio and video data, and thus, the media engine 206A may process audio data while the media engine 206B may process video data.

One important topic is the ability to playback a presentation and insert an advertisement (ad) across a program boundary without interrupting the playback experience. Two key problems have been observed. One problem corresponds to capability discovery if the media can be played back over the entire presentation, including across program boundaries. Another problem corresponds to the initialization and establishment of a track buffer/media pipe for each media type that can be used to continuously playback one type of media throughout the presentation.

Amd.5 and TuC of DASH discusses several methods to solve the first problem described above related to capability discovery. In particular, the method comprises using early available time periods and/or using dedicated capability signaling in combination with different features.

Fig. 6 is a conceptual diagram illustrating an example of track buffer based playback.

While a solution following the approach discussed above may be sufficient to address the capability discovery aspects for playback of an entire presentation, it is still unclear whether a DASH client can establish playback of media in a good enough manner.

Typically, a device needs to establish at least one track buffer/media pipe for video media types and another track buffer/media pipe for audio media types. It may also be necessary to establish track buffers/media pipes for other media types, such as subtitles (timed text). The device may support the establishment of multiple source buffers for each media type.

A typical operation of establishing such a source buffer is as follows:

the ability to recognize that a device supports handling specific media types as well as MIME subparameters.

If successful, then the source buffer is initialized appropriately using the correlation function

Creating an appropriate output environment for each established source buffer

o for video, a predetermined display window matching the aspect ratio and

■ default, the size (height and width) of the content,

■ or as a full screen mode (possibly using a mailbox),

■ or an HDMI output.

o for audio, using output configuration of loudspeakers

For example, HTML-5 media elements and media source extensions allow the addition of source buffers using the mediasource. For detailed information, please see: www.w.3. org/TR/media-source/# dom-media-resource-addsourceebuffer. For the case of the ISO BMFF byte stream format, the source buffer IS further initialized by appending an Initialization slice segment (IS) to the source buffer using mediasource. It is important that the initialization is done so that the playback of the rest of the presentation can be done properly. Note that the source buffer can be updated/re-initialized by appending IS to the source buffer using mediasource.

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

Fig. 7 is a conceptual diagram illustrating an example content model for DASH multi-track media data in accordance with the present technology. In this example, the content 220 includes media-type video content 222, media-type audio content 224, media-type subtitle content 226, and media-type application content 228. These media types may be arranged into various content types, such as media type content primary 230, media type content alternate 232A, and media type content alternate 232B. Each of the primary content and the alternate content may include content selected from one or more corresponding target version adaptation sets 234A-234C, including respective encoded presentations, such as presentations 236A-236C.

To support content authors in providing content in a consistent manner, fig. 7 provides a conceptual content model of DASH content 220 over a period of MPD according to DASH-IF IOP v 4.2. In an extension of the model of fig. 7, for the entire MPD, an initialization set may be selected that provides a superset of multiple adaptation sets (adaptation sets 234) over one time period and across multiple time periods. If this initialization set is selected, playback can continue across the time period boundary.

The source device (e.g., content preparation device 20 and/or server device 60 of fig. 1) and the client device (e.g., client device 40 of fig. 1 and/or DASH client 200 of fig. 5) may be configured to use the techniques of this disclosure to use an initialization set that allows continuous playback across time period boundaries. Specifically, these techniques include the following:

1. manifest file (e.g., MPD) level signaling that may select an appropriate initialization set including initialization segments for the entire media presentation

2. An initialization segment is provided within the selected initialization set that allows initialization of the media pipe for a particular media type (including encoder, decryption, and rendering environment).

3. MPD signaling is provided that allows for identification of adaptation sets and presentations that may be based on the selected initialization set.

4. This signaling is provided in a backward compatible manner.

The initialization set may be defined in two example ways:

1. as a superset of all reference adaptation sets.

2. As a pure initialization construct focusing on the media pipeline.

The semantics of the MPD element of the DASH specification may be updated to include an InitializationSet element, as shown in table 1 below:

TABLE 1

The semantics of the initialization set element of the MPD (or other manifest file) may be defined as follows (where the identified portions correspond to portions of the DASH standard):

x initialization set

Summary of X.1

The initialization set provides a common set of media attributes across the media presentation. If an initialization set with certain attributes is provided in the MPD, at least one adaptation set with the same attributes in each time period should be used in each time period. The initialization set may be selected at the beginning of the media presentation in order to establish the relevant decryption, decoding and rendering environment. Thus, the initialization set shares all the parameters of the adaptation set, but only in a media presentation, the adaptation set may have additional information, such as:

there may be an initialization set with media type audio and @ codecs parameters but no @ lang attribute. There may then be adaptation sets with the same media type, the same @ codecs parameter, but each of the adaptation sets defines a language. This ensures that playback of the audio is possible, but may vary.

There may be an initialization set with the media type video and the @ maxWidth and @ maxHeight parameters and the @ codecs parameter. There may then be an adaptation set that has the same media type, but different actual encoder parameters, width and height, but can be decoded and displayed within the initialized set constraints.

If the MPD has multiple periods, there should be at least one initialization set for each media type.

The semantics of the attributes and elements within the InitializationSet element are provided in table 5 of x.3. The XML syntax of the InitializationSet element is provided in x.3.

X.2 semantics

TABLE 5-semantics of Adaptation Collection elements

X.3XML syntax

The following attributes may be added to the adaptation set element of the MPD:

by providing an initialization set, the DASH client may select an initialization that matches the capabilities of the device that includes the DASH client, and may also ensure continuous playback by initializing using the provided initialization segment. The techniques of this disclosure may also address discussions regarding early availability periods and provide new capability mechanisms because relevant information is provided in advance.

Fig. 8 is a flow diagram illustrating an example method of transmitting media data in accordance with the techniques of this disclosure. For purposes of example, 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 this or similar methods, alone or in combination with other devices.

Initially, content preparation device 20 determines initialization parameters for a media presentation, such as multimedia content 64 (300). The initialization parameters may be used to initialize the media data for any adaptation set and/or presentation of the media presentation. For example, the initialization parameters may specify a maximum width and a maximum height of a picture for a media presentation and/or a maximum frame rate. The initialization parameters may also specify a picture aspect ratio for pictures of the media presentation.

Content preparation device 20 may then construct an initialization segment for the media presentation (302). The content preparation device 20 may construct initialization segments for various types of media such as audio, video, timed text (closed captioning), etc. Content preparation device 20 may construct an initialization segment in accordance with the initialization parameters determined above.

Content preparation device 20 may further construct a manifest file (such as a DASH MPD) that includes one or more initialization sets (304). Each initialization set may conform to the initialization sets of tables 1 and 5 above. As described above, each initialization set may include an @ maxfidth element specifying the maximum picture width, an @ maxhight element specifying the maximum picture height, and an @ maxFrameRate element specifying the maximum frame rate. Content preparation device 20 may further specify the URLs of the initialization segments in the initialization set (e.g., in the respective @ initialization element). Content preparation device 20 may construct an initialization set for each adaptation set, thereby constructing one or more initialization sets for each media type (e.g., audio, video, timed text, etc.). The initialization set may include an @ contentType element that specifies the media type (e.g., audio, video, timed text, etc.) of the initialization set, as shown in table 5.

Content preparation device 20 may then send the initialization set to the client device (306). In particular, content preparation device 20 may send a manifest file to the client device, the manifest file including the initialization set. As shown in fig. 1, content preparation device 20 may transmit the manifest file to server device 60, and server device 60 may transmit the manifest file to client device 40 in response to a request from client device 40 for the manifest file for a particular media presentation.

Content preparation device 20 may also receive a request for media data from a client device (308). Alternatively, server device 60 may receive the request. In response to the request, content preparation device 20 (or server device 60) may transmit the requested media data to the client device (310). In some examples, a client device (e.g., client device 40) may request media data from various presentations for the same type of media content. However, the client device 40 may only request an initialization segment for that type of media content once, as the initialization segment may be used to initialize playback of all of the media content for that type of media presentation. In this manner, the techniques of this disclosure may be used to reduce the number of initialization segments sent by content preparation device 20 and/or server device 60 to client device 40. In this manner, these devices may avoid processing requests for initialization segments and also reduce the network bandwidth utilized when receiving requests for initialization segments and sending the initialization segments to client device 40.

In this manner, the method of fig. 8 represents an example of a method of transmitting media data, the method including: sending a manifest file for the media presentation to the client device, the manifest file comprising data for an initialization set, the initialization set comprising initialization parameters for an entire duration of the media presentation; receiving a request for media data of a media presentation from a client device; and transmitting the requested media data to the client device.

Fig. 9 is a flow diagram illustrating an example method of retrieving media data in accordance with the techniques of this disclosure. For purposes of example and explanation, the method of fig. 9 is described with respect to client device 40 of fig. 1. However, other devices may be configured to perform this or similar methods. For example, the DASH client 200 of fig. 5 may be configured to perform this method.

Initially, client device 40 may retrieve a manifest file that includes one or more initialization sets (330). The initialization set of manifest files may specify initialization parameters such as maximum width and maximum height of a picture, picture aspect ratio of a picture, maximum frame rate, etc. The initialization set may also indicate the URL of the corresponding initialization segment. Accordingly, client device 40 may retrieve the initialization segment for each of the initialization sets (and likewise for each type of media content, e.g., audio, video, timed text, etc.) (332).

Client device 40 may then initialize playback of the media data using the initialization set and the initialization segment (334). Such initialization may be used for decryption, decoding and/or rendering. For example, client device 40 may initialize video decoders and renderers according to a maximum height, a maximum width, and a maximum frame rate. Such initialization may include, for example, allocating buffer space in a buffer of a memory (e.g., cache 104) for storing the retrieved media data and/or for storing intermediate media data (e.g., partially or fully decoded media data).

Client device 40 may then request the media data (336), for example, by issuing an HTTP GET or partial GET request for the media data. Client device 40 may then receive the media data (338) and play back the media data (340). In some examples, client device 40 may retrieve media data having maximum specified parameters, e.g., maximum height, maximum width, maximum frame rate, etc. In some examples, client device 40 may retrieve media data having less than a maximum specified parameter. Client device 40 may retrieve media data having the largest specified parameter for a first playback time and retrieve media data having less than the largest specified parameter for a second, different playback time. However, client device 40 does not need to reinitialize playback of media data having less than the maximum specified parameter because the original initialization may be used to playback of any media data of the media presentation because the initialization parameter specifies the maximum parameter or a constant parameter.

In this manner, the method of fig. 9 represents an example of a method of retrieving media data, the method comprising: retrieving a manifest file for the media presentation, the manifest file comprising data for an initialization set, the initialization set comprising initialization parameters for an entire duration of the media presentation; initializing playback of media data of the media presentation using the initialization set; retrieving media data of a media presentation; the media data is presented according to the initialized playback.

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 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.