ITU-R BT 1888-1-2011 Basic elements of file-based broadcasting systems《基于文件的广播系统的基本要素》.pdf

1、 Recommendation ITU-R BT.1888-1(09/2011)Basic elements of file-based broadcasting systemsBT SeriesBroadcasting service(television)ii Rec. ITU-R BT. 1888-1 Foreword The role of the Radiocommunication Sector is to ensure the rational, equitable, efficient and economical use of the radio-frequency spec

2、trum by all radiocommunication services, including satellite services, and carry out studies without limit of frequency range on the basis of which Recommendations are adopted. The regulatory and policy functions of the Radiocommunication Sector are performed by World and Regional Radiocommunication

3、 Conferences and Radiocommunication Assemblies supported by Study Groups. Policy on Intellectual Property Right (IPR) ITU-R policy on IPR is described in the Common Patent Policy for ITU-T/ITU-R/ISO/IEC referenced in Annex 1 of Resolution ITU-R 1. Forms to be used for the submission of patent statem

4、ents and licensing declarations by patent holders are available from http:/www.itu.int/ITU-R/go/patents/en where the Guidelines for Implementation of the Common Patent Policy for ITU-T/ITU-R/ISO/IEC and the ITU-R patent information database can also be found. Series of ITU-R Recommendations (Also av

5、ailable online at http:/www.itu.int/publ/R-REC/en) Series Title BO Satellite delivery BR Recording for production, archival and play-out; film for television BS Broadcasting service (sound) BT Broadcasting service (television) F Fixed service M Mobile, radiodetermination, amateur and related satelli

6、te services P Radiowave propagation RA Radio astronomy RS Remote sensing systems S Fixed-satellite service SA Space applications and meteorology SF Frequency sharing and coordination between fixed-satellite and fixed service systems SM Spectrum management SNG Satellite news gathering TF Time signals

7、 and frequency standards emissions V Vocabulary and related subjects Note: This ITU-R Recommendation was approved in English under the procedure detailed in Resolution ITU-R 1. Electronic Publication Geneva, 2011 ITU 2011 All rights reserved. No part of this publication may be reproduced, by any mea

8、ns whatsoever, without written permission of ITU. Rec. ITU-R BT. 1888-1 1 RECOMMENDATION ITU-R BT. 1888-1 Basic elements of file-based broadcasting systems (3/2011-9/2011) Scope This Recommendation describes basic elements of file-based broadcasting systems to facilitate the transfer of files from a

9、 content provider to an end user. The files transferred in both real-time and non real-time are stored in a receiver to be played at a time convenient to the end user. The Recommendation provides some basic implementation characteristics of a receiver. The ITU Radiocommunication Assembly, considerin

10、g a) that there is a growing consumer demand for the capability to view TV programmes at their convenience; b) that there is growing consumer interest in viewing all types of content including audio/video and multi-media content; c) that large-capacity storage devices have become available for a rec

11、eiver; d) that file-based systems are capable of delivering any kind of content including audio/video as well as multimedia data in non-real-time transfer; e) that high-quality content encoded at higher bit rate than that in real-time broadcasting can be delivered using non real-time transfers; f) t

12、hat services using file-based content delivery have already been introduced using telecommunication networks; g) that it is desirable to provide interoperability between different systems, recommends 1 that the basic elements described in Annex 1 should be used for development of file-based broadcas

13、ting systems; 2 that NOTE 1 is considered to be part of the Recommendation. NOTE 1 Compliance with this Recommendation is voluntary. However, the Recommendation may contain certain mandatory provisions (to ensure e.g. interoperability or applicability) and compliance with the Recommendation is achie

14、ved when all of these mandatory provisions are met. The words “shall” or some other obligatory language such as “must” and the negative equivalents are used to express requirements. The use of such words shall in no way be construed to imply partial or total compliance with this Recommendation. NOTE

15、 2 Example of practical implementation of a file-based broadcasting system is given in Appendix 1 and Appendix 2 for information. 2 Rec. ITU-R BT. 1888-1 Annex 1 Basic elements for file-based broadcasting systems 1 Introduction File-based broadcasting systems have the capability to be independent of

16、 the content to be delivered, end user storage devices are also independent of the content being stored. This results in huge flexibility in what a content provider may deliver to the end user. Content can be delivered in shorter or longer periods than the real-time duration. High-quality content ca

17、n be delivered by encoding the content at higher bit rates than the maximum bit rate of the delivery channel. In the case of mobile reception, while reception errors often occur, errors may be corrected through various techniques in the case of non real-time transmission. The basic elements describe

18、d in this annex apply to requirements for file-based broadcasting systems, receiver configuration for the systems, metadata, and a file transport method over a broadcast channel. 2 Abbreviations BML Broadcast markup language CID Context identification DLC Download control DRM Digital rights manageme

19、nt ECG Electronic content guide FEC Forward error correction FLUTE File delivery over unidirectional transport HCfB Header compression for broadcasting IANA Internet assigned numbers authority IP Internet protocol LLI Licence link information RMT Reliable multicast transport ROHC Robust header compr

20、ession TLV Type length value ULE Unidirectional lightweight encapsulation URI Uniform resource identifier URL Uniform resource locator Rec. ITU-R BT. 1888-1 3 3 Requirements for file-based broadcasting systems 3.1 System requirements To develop a file-based broadcasting system, the following require

21、ments should be met: 1. A receiver for the system shall be equipped with a storage device to store content and play the content. Play of content may be output from the storage device through a copy protected interface. 2. Information necessary for setting up a scheduled download should be delivered

22、over the broadcast channel. 3. It should be possible to set up a scheduled download of additional content related to real-time broadcasting programme. 4. Receiver tuning shall be controlled by the specific information. 5. Any rescheduling of content shall be possible through the scheduling informati

23、on. 6. Lost or corrupted file should be detected by a receiver prior to its use. 7. Large files should be delivered with a small overhead. 8. Delivered content can be protected to restrict the use by the end user. 9. An expiration date for the use of the content may be sent. 10. Stored content in a

24、receiver may be deleted by the end user. 3.2 Required files In the system, the following files should be delivered: 1. Media file. Coded audio/video signals or other multimedia data. 2. License link information (LLI). Information on license and rights management for the content. It describes constra

25、ints on the use of content. It also provides information to obtain a license if required. 3. Metadata: Metadata for establishing the download schedule. Information necessary for a receiver to obtain all files including a media file, LLI, and ECG metadata. It describes URLs of servers or URI and star

26、t/end times of the delivery session that carries these files. Details are described in 5. ECG metadata. Information on content such as title and genre. It is used by an end user to select content to store. It may also be used to select stored content to use. Details are described in 6. Figure 1 show

27、s a protocol stack of general file-based broadcasting systems to transfer these files. 4 Rec. ITU-R BT. 1888-1 FIGURE 1 Protocol stack of general file-based broadcasting systems BT.1888-01Audio/video or other multimedia dataLLIECG metadataMetadata for setup a scheduled downloadMedia fileDRMFileFile

28、transport methodChannel coding and modulationPhysical layer (terrestrial/satellite)4 Receiver configuration for a file-based broadcasting system 4.1 Main components in a receiver for the system A receiver for the system shall have storage to store the delivered content. The main components in a rece

29、iver are shown in Fig. 2. FIGURE 2 Main components in receiver for the system BT.1888-02DownloaderContent guideMedia playerStorageSetup navigation of a scheduled downloadBroadcasting signalsMedia fileLLI, ECG MetadataMetadatafor setupECG metadataReceiverControlOutputsignalsBroadcastingdemodulation a

30、nddemultiplexedECG metadataControlDemultiplexed signalsMedia fileThe functions of each module in a receiver are listed below. Module FunctionBroadcast demodulation and demultiplex Demodulates received broadcasting signals and outputs demultiplexed signals that carry files Downloader Manages schedule

31、s for downloading content. Reconstructs a file from the demultiplexed signals when recording Setup navigation of a scheduled download Lets users set a scheduled download based on metadata for setup a scheduled download and ECG metadata Storage Stores reconstructed files by downloader Content guide P

32、resents a list of stored content and provides a user interface to select and delete content based on ECG metadata Media player Plays stored content and outputs audio/video signals Rec. ITU-R BT. 1888-1 5 4.2 Reference receiving procedures to obtain content In a file-based broadcasting system, the fo

33、llowing receiving procedures should be taken. A receiver for the system needs metadata for setting up a scheduled download of the required content in advance. The metadata needs to be transferred by a service provider. Multiple files may make up one content. Therefore, metadata is important for the

34、receiver to identify files of content and servers or sessions that provide those files. Based on this information, the receiver sets up a scheduled download. At the scheduled time, the receiver tunes into the broadcast signal delivering the desired files, and stores the delivered files. These proced

35、ures are shown in Fig. 3. FIGURE 3 Receiving procedures to obtain content BT.1888-03Service provider ReceiverMetadata for setupMedia, LLI and ECG metadata filesMedia, LLI and ECG metadata filesMedia, LLI and ECG metadata filesMedia, LLI and ECG metadata filesMetadata for setupLicence informationPars

36、eSetupStoreUseAfter the receiver stores the files, the content may be used at any time. As required the receiver shall obtain a valid license according to the LLI of the content. 5 Metadata 5.1 Metadata for setting up a scheduled download Metadata describing all the information necessary for setting

37、 up a scheduled download should be transferred to the receiver prior to the content delivery. Metadata for setting up a scheduled download should include the following information: 1. Information on delivery schedules, namely start/end times. 2. Information on delivery session to identify the broadc

38、ast signal. 3. Information required to reconstruct files from transmitted data. 4. Information on file, namely the file name, file size, and file type. 5. Content identification. 6. Information on DRM server if required. 6 Rec. ITU-R BT. 1888-1 Prior to obtaining content, a receiver has to identify

39、what content will be delivered and its delivery information on broadcast signal. All files comprising the content should also be identified. Based on the metadata, a receiver stores the necessary files for the selected content at a specified time. The metadata may describe auxiliary information for

40、a receiver to select the content. 5.2 ECG metadata ECG metadata including the following information should be transferred to receivers: 1. Description of content title, abstraction, and genre. It may include thumbnail-size images of the content. 2. Properties of video/audio or other multimedia data.

41、 3. Description of price and other information for billing. 4. Description of rights to use the content and other information to obtain the license. ECG metadata is used for navigation to select. It is also used for navigation to select content to use from the stored content list. 6 File transport m

42、ethod over broadcast channel All content and content related metadata, should be transferred by a reliable and efficient file transport method. Several files may be packaged into one file for a single transfer. As in real-time broadcasting systems, it is important to minimize transfer delay in file-

43、based broadcasting systems. However, delay variation has less impact in file-based broadcasting systems compared to real-time broadcasting systems. It is important to transfer and store a file without loss or corruption. A detection mechanism to detect lost or corrupted file fragments should be inco

44、rporated in file-based broadcasting systems. A system should be equipped with some mechanisms to repair lost or corrupted file fragments. Appendix 1 (informative) File-based broadcasting system for advanced-satellite broadcasting in Japan11 Overview Digital broadcasting provides content to many view

45、ers at once via terrestrial or satellite broadcasting channels in a stable manner. All viewers can enjoy broadcast programmes at the same time. However, it is difficult to respond to individual requests from all viewers. In contrast with broadcasting, telecommunication provides requested content via

46、 bi-directional channels. However, it is subject to certain problems, e.g. limitations in the network bandwidth and the equipment throughput may result in deteriorated service quality when a large number of viewers make requests. 1This system is specified in Part 1 of ARIB STD-B45 v2.0 (2011): Conte

47、nt download system for broadcasting. Rec. ITU-R BT. 1888-1 7 When these different delivery channels are combined to deliver content, they complement each other and lead to enriched multimedia services. The file-based broadcasting system developed in Japan delivers popular content over broadcasting c

48、hannels in a short time and also delivers requested content on telecommunication networks. Figure 4 shows an overview of the system. FIGURE 4 Overview of a file-based broadcasting system using broadcasting channels and telecommunication networks BT.1888-04HomeTelecommunicationnetworksRequestedconten

49、tLicenceinformation, etc.ServiceproviderBroadcastingchannelsPopularcontentIn this system, frequently requested content is provided to many users via broadcasting channels. Less frequently requested content is provided via telecommunication networks. Files storing audio/video code and associated metadata are delivered over broadcasting channels to every receiver. In addition to these files, the receiver individually obtains the license information from the server using telecommunication networks when needed. The size of license information is small compared to the content itself