1、 ETSI TR 102 989 V1.1.1 (2011-05)Technical Report Media Content Distribution (MCD);Subtitles distribution, situation and perspectivesETSI ETSI TR 102 989 V1.1.1 (2011-05) 2Reference DTR/MCD-00012 Keywords access, distribution, teletext, transmission ETSI 650 Route des Lucioles F-06921 Sophia Antipol
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8、.1 (2011-05) 3Contents Intellectual Property Rights 4g3Foreword . 4g31 Scope 5g32 References 5g32.1 Normative references . 5g32.2 Informative references 5g33 Definitions and abbreviations . 6g33.1 Definitions 6g33.2 Abbreviations . 7g34 Subtitling in the media content distribution context . 8g34.1 S
9、ubtitling vs. captioning . 8g34.2 Bitmap and textual subtitles . 8g34.3 Presentation techniques 9g34.3.1 On-screen techniques 9g34.3.2 Techniques complementary to subtitling facilitating other functionalities . 10g34.4 3D-specific challenges . 11g34.5 Necessity of subtitles distribution 11g35 Subtit
10、les flow 12g35.1 In an SD-only content distribution . 14g35.2 In an HD content distribution with HD-SDI transmission . 15g35.3 In an HD content distribution with encoded transmission 16g35.4 In a content distribution with late component binding . 17g36 Production 17g36.1 Off-line vs. live subtitling
11、 17g36.2 Production formats for off-line contents 18g36.2.1 Historical formats . 18g36.2.2 WebVTT . 18g36.2.3 TTML . 18g36.2.4 European Broadcasting Union 19g36.3 Production formats for live subtitling . 19g37 Broadcasting . 19g37.1 SD signal 19g37.2 HD signal 19g37.3 SMPTE-TT . 20g38 Transmission 2
12、0g38.1 (HD-)SDI transmission . 20g38.2 Encoded transmission . 20g39 Distribution . 21g39.1 Bitmap and textual distribution formats . 21g39.2 Available formats . 22g310 Synthesis and conclusions 23g310.1 For a better balance between text and bitmap formats . 23g310.2 For a modern timed text format 23
13、g310.3 Lack of a production standard 23g310.4 Lack of a broadcasting standard . 23g310.5 Lack of a distribution standard . 23g310.6 Wide application for a standardized timed text 24g3Annex A: Bibliography 25g3History 26g3ETSI ETSI TR 102 989 V1.1.1 (2011-05) 4Intellectual Property Rights IPRs essent
14、ial or potentially essential to the present document may have been declared to ETSI. The information pertaining to these essential IPRs, if any, is publicly available for ETSI members and non-members, and can be found in ETSI SR 000 314: “Intellectual Property Rights (IPRs); Essential, or potentiall
15、y Essential, IPRs notified to ETSI in respect of ETSI standards“, which is available from the ETSI Secretariat. Latest updates are available on the ETSI Web server (http:/webapp.etsi.org/IPR/home.asp). Pursuant to the ETSI IPR Policy, no investigation, including IPR searches, has been carried out by
16、 ETSI. No guarantee can be given as to the existence of other IPRs not referenced in ETSI SR 000 314 (or the updates on the ETSI Web server) which are, or may be, or may become, essential to the present document. Foreword This Technical Report (TR) has been produced by ETSI Technical Committee Media
17、 Content Distribution (MCD). ETSI ETSI TR 102 989 V1.1.1 (2011-05) 51 Scope The present document is an analysis of the situation in the distribution of subtitling information of associated television services. 2 References References are either specific (identified by date of publication and/or edit
18、ion number or version number) or non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the reference document (including any amendments) applies. Referenced documents which are not found to be publicly available in the expected loca
19、tion might be found at http:/docbox.etsi.org/Reference. NOTE: While any hyperlinks included in this clause were valid at the time of publication ETSI cannot guarantee their long term validity. 2.1 Normative references The following referenced documents are necessary for the application of the presen
20、t document. Not applicable. 2.2 Informative references The following referenced documents are not necessary for the application of the present document but they assist the user with regard to a particular subject area. i.1 SMPTE 0259M: “Television - SDTI Digital Signal/Data - Serial Digital Interfac
21、e“. i.2 SMPTE 292: “1.5 Gb/s Signal/Data Serial Interface“. i.3 ETSI EN 300 743: “Digital Video Broadcasting (DVB); Subtitling systems“. i.4 ETSI EN 300 706: “Enhanced Teletext specification“. i.5 CEA-608: “Line 21 Data Services“. i.6 EBU Tech. 3264-E, Specification of the EBU Subtitling Data Exchan
22、ge Format, European Broadcasting Union, February 1991. NOTE: Available at: http:/tech.ebu.ch/docs/tech/tech3264.pdf. i.7 Association media for all. NOTE: Available at: http:/www.mediaforall.eu/. i.8 ETSI TS 102 796: “Hybrid Broadcast Broadband TV“. i.9 Directive 2007/65/EC of the European Parliament
23、 and of the Council of 11 December 2007 amending Council Directive 89/552/EEC on the coordination of certain provisions laid down by law, regulation or administrative action in Member States concerning the pursuit of television broadcasting activities. i.10 Directive 2002/19/EC of the European Parli
24、ament and of the Council of 7 March 2002 on access to, and interconnection of, electronic communications networks and associated facilities (Access Directive). ETSI ETSI TR 102 989 V1.1.1 (2011-05) 6i.11 Directive 2002/21/EC of the European Parliament and of the Council of 7 March 2002 on a common r
25、egulatory framework for electronic communications networks and services (Framework Directive, (FwD). i.12 Directive 2002/22/EC of the European Parliament and of the Council of 7 march 2002 on universal service and users rights relating to electronic communications networks and services (Universal Se
26、rvice Directive, (USD). i.13 Directive 1999/5/EC of the European Parliament and of the Council of 9 March 1999 on radio equipment and telecommunications terminal equipment and the mutual recognition of their conformity (R MCD framework; Part 3: Regulatory issues, social needs and policy matters“. i.
27、15 WHATWG WebVTT, extracted from the WHATWG HTML specification. NOTE: Available at http:/www.whatwg.org/specs/web-apps/current-work/webvtt.html. i.16 W3C Recommendation: “Timed Text Markup Language (TTML)“. NOTE: Available at: http:/www.w3.org/TR/ttaf1-dfxp/. i.17 Free TV Australia Operational Pract
28、ice OP- 47: “ Storage and distribution of teletext subtitles and VBI data for high definition television“. i.18 SMPTE 2031: “Carriage of DVB/SCTE VBI Data in VANC“. i.19 IETF RFC 3629: “UTF-8, a transformation format of ISO 10646“. i.20 EBU R 110: “Subtitling on digital TV services“. i.21 ETSI TS 10
29、1 547: “Digital Video Broadcasting (DVB); Frame Compatible Plano-Stereoscopic 3DTV“. i.22 ETSI ES 202 432: “Human Factors (HF); Access symbols for use with video content and ICT devices“. i.23 ITU-T Recommendation Y.1901: “Requirements for the support of IPTV services“. i.24 Directive 2002/21/EC of
30、the European Parliament and of the Council of 7 March 2002 on a common regulatory framework for electronic communications networks and services (Framework Directive, (FwD). i.25 Directive 98/34/EC: “Procedure for the provision of information in the field of technical regulations and rules on informa
31、tion society services“. 3 Definitions and abbreviations 3.1 Definitions For the purposes of the present document, the following terms and definitions apply: anti-aliasing: technique of minimizing the distortion artefacts appearing when representing high-resolution objects such as fonts to a low-reso
32、lution display such as a TV screen ETSI ETSI TR 102 989 V1.1.1 (2011-05) 7captions: real-time on-screen transcript of the dialogue as well as any sound effects NOTE 1: This service can be provided by means of either textual or graphical supplementary content. The captions and the dialogue are usuall
33、y in the same language. The service is primarily to assist users having difficulty hearing the sound. Ideally, users may have some control over the position and size of the presentation. Different speakers are distinguished, usually by different colours. NOTE 2: This is based on ITU-T Recommendation
34、 Y.1901 i.23, clause 3.2.4. content provider (CP): actor making available any kind of content where it has editorial responsibility or represent those with editorial responsibility electronic communications service (ECS): service normally provided for remuneration which consists wholly or mainly in
35、the conveyance of signals on electronic communications networks, including telecommunications services and transmission services in networks used for broadcasting, but excluding services providing, or exercising editorial control over, content transmitted using electronic communications networks and
36、 services; it does not include information society services, as defined in Article 1 of Directive 98/34/EC i.25, which do not consist wholly or mainly in the conveyance of signals on electronic communications networks NOTE: This is based on the FwD i.24, Article 2, Definitions, (c). electronic commu
37、nications service provider (ECSP): actor offering ECS; in the context of Media Content Distribution (MCD) means those that offer the contents available from Content Providers but do not have editorial interference on it encode: convert content from one format (typically raw) to another (typically lo
38、wer bit rate) sign language: language that uses a system of manual, facial, and other body movements as the means of communication subtitler: person in charge of creating subtitles for a content teletext: data delivery system within television transmission 3.2 Abbreviations For the purposes of the p
39、resent document, the following abbreviations apply: 3D Three Dimensional ANSI American National Standards Institute ASCII American Standard Code for Information Interchange ATSC Advanced Television Systems Committee CBR Constant Bit Rate CC Closed CaptionCP Content Provider DFXP Distribution Format
40、Exchange Profile DVB Digital Video Broadcasting DVDTMDigital Versatile Disc ECI Experts Community Integrated production ECSP Electronic Communications Service Provider HD High Definition HDTV High Definition Television HTML Hyper Text Markup Language IP Internet Protocol IPTV Internet Protocol TeleV
41、ision MXF Metadata eXchange Format OCR Optical Character Recognition PID Packet Identifier SD Standard DefinitionSDI Serial Digital Interface SDTV Standard Definition Television SMIL Synchronised Multimedia Integration Language VANC Vertical ANCillary data space ETSI ETSI TR 102 989 V1.1.1 (2011-05)
42、 8VBI Vertical Blanking Interval VBR Variable Bit Rate VOD Video On Demand W3C World Wide Web Consortium XML Extensible Markup Language 4 Subtitling in the media content distribution context 4.1 Subtitling vs. captioning In general the term caption is more related to original capture of all informat
43、ion (noise, sound, surrounding conditions) associated to an event and the term subtitling rather used in relation to the textual (in a picture or as a sequence of words and letters) expression describing or reproducing the same event. Using this textual expression, different types of presentation te
44、chniques (text overlapped on the image in one or several languages, the language of signs or even audio description) may be used. However “captioning“ is more common in the U.S.A. and is typically used for same language transcription, for instance for the hearing impaired; “subtitling“ often refers
45、to language translation of foreign programmes. The terms “open captions“ and “closed captions“ are also very common: Open captions (also called “burnt-in“ “in-vision“, or “hardsubs“) are encoded as a permanent part of the video image, irreversibly merged into the frames. They cannot be disabled, and
46、 no specific “track“ is needed to convey them. Also, no special equipment or software is required for playback, and any character set (including pure graphics) can be used. Consequently this technique allows for very complex transition effects and animation (for instance karaoke song lyrics). Howeve
47、r it does not allow for multiple user-selectable variants of subtitling (such as English, English Hard of Hearing, and French). Closed captions are viewer-selectable and carried over a separate “track“ or “component“ (which may be collocated inside the video track, but not in the video data itself).
48、 Examples of closed captions include the Line 21 Closed Captioning system in the USA (carried as text), Teletext subtitles in Europe (text as well) or DVB subtitles (graphics). The carriage of this separate, discrete data stream may be problematic in some contexts. Nowadays both the subtitling and t
49、he captioning terms are disappearing in favour of the “timed text“ expression. In the other clauses of the present document, “subtitling“ refers to both “subtitles“ and “closed captions“; open captions are carried inside the video data and do not require a specific handling. In other categorization, digital video subtitles are sometimes called internal, if theyre embedded in a single video file container along with video and audio streams, and external if they are distributed as separate file (that is less con
