SIST EN 303 560 V1.1.1:2018

SLOVENSKI STANDARD
SIST EN 303 560 V1.1.1:2018
01-september-2018
Digitalna videoradiodifuzija (DVB) - Sistemi TTML za podnaslove
Digital Video Broadcasting (DVB) - TTML subtitling systems
Ta slovenski standard je istoveten z: ETSI EN 303 560 V1.1.1 (2018-05)
ICS:
33.170 Televizijska in radijska Television and radio
difuzija broadcasting
SIST EN 303 560 V1.1.1:2018 en

2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

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Intellectual Property Rights ................................................................................................................................ 5

Foreword ............................................................................................................................................................. 5

Modal verbs terminology .................................................................................................................................... 6

Introduction ........................................................................................................................................................ 6

1 Scope ........................................................................................................................................................ 7

2 References ................................................................................................................................................ 7

2.1 Normative references ......................................................................................................................................... 7

2.2 Informative references ........................................................................................................................................ 8

3 Definitions and abbreviations ................................................................................................................... 9

3.1 Definitions .......................................................................................................................................................... 9

3.2 Abbreviations ................................................................................................................................................... 10

4 Default DVB TTML subtitle conformance point ................................................................................... 11

4.1 Introduction ...................................................................................................................................................... 11

4.2 Document Constraints ...................................................................................................................................... 11

4.2.1 General ........................................................................................................................................................ 11

4.2.2 Regions ....................................................................................................................................................... 12

4.2.3 Document complexity ................................................................................................................................. 12

4.2.4 Document encoding .................................................................................................................................... 12

4.2.5 Namespaces ................................................................................................................................................ 12

4.2.6 Guidance for document authors and content providers (informative) ........................................................ 12

4.2.6.1 Overview ............................................................................................................................................... 12

4.2.6.2 Font mapping for generic font family names ........................................................................................ 12

4.2.6.3 Default text colour................................................................................................................................. 13

4.2.6.4 Requirement for support of optional features ........................................................................................ 13

4.2.6.5 Specifying active area ........................................................................................................................... 13

5 Delivery .................................................................................................................................................. 13

5.1 IP delivery ........................................................................................................................................................ 13

5.2 Broadcast TS delivery ...................................................................................................................................... 13

5.2.1 PSI/SI signalling ......................................................................................................................................... 13

5.2.1.1 TTML subtitling descriptor ................................................................................................................... 13

5.2.1.2 Example TTML profile signalling ........................................................................................................ 17

5.2.1.2.1 Signalling conformance only to the default conformance point ...................................................... 17

5.2.1.2.2 Signalling conformance to only EBU-TT-D ................................................................................... 17

5.2.1.2.3 Signalling conformance with EBU-TT-D and the default conformance point ................................ 17

5.2.1.2.4 Signalling conformance to only IMSC1 Text Profile ...................................................................... 18

5.2.1.3 Presentation properties in qualifier field ............................................................................................... 18

5.2.1.4 Component descriptors for TTML subtitles .......................................................................................... 19

5.2.2 TS packetization ......................................................................................................................................... 19

5.2.2.1 PES packet format and carriage in the TS ............................................................................................. 19

5.2.2.2 PES packet payload format for TTML subtitling .................................................................................. 20

5.2.2.2.1 General PES payload field syntax and segment types ..................................................................... 20

5.2.2.2.2 Occurrences of segments in one PES packet ................................................................................... 21

5.2.2.2.3 Uncompressed TTML document subtitle segment .......................................................................... 21

5.2.2.2.4 gzip compressed TTML document subtitle segment ....................................................................... 21

5.2.3 TTML segmentation ................................................................................................................................... 21

5.2.3.1 General .................................................................................................................................................. 21

5.2.3.2 Concept of ISDs .................................................................................................................................... 22

5.2.3.3 Active Period of a TTML segment ....................................................................................................... 22

5.2.3.4 TTML documents segmentation rules ................................................................................................... 22

5.2.3.5 Subtitle stream in the absence of subtit les ............................................................................................. 22

5.2.3.6 Continuation of a subtitle across adjacent segments ............................................................................. 22

5.2.3.7 Untimed elements in TTML segments .................................................................................................. 23

5.2.3.8 Examples of TTML segmentation ......................................................................................................... 23

5.2.4 Synchronization .......................................................................................................................................... 23

5.2.4.1 Relationship between MPEG system clock and TTML timeline .......................................................... 23

5.2.4.2 Failure of TTML segment reception ..................................................................................................... 24

5.2.4.3 Synchronization examples .................................................................................................................... 24

5.2.5 Acquisition time .......................................................................................................................................... 27

5.3 Font download .................................................................................................................................................. 27

5.3.1 Introduction................................................................................................................................................. 27

5.3.2 Font delivery signalling mechanism ........................................................................................................... 28

5.3.2.1 Overview ............................................................................................................................................... 28

5.3.2.2 Linkage descriptor with linkage type 0x20 ........................................................................................... 29

5.3.2.2.1 Introduction ..................................................................................................................................... 29

5.3.2.2.2 Linkage descriptor with linkage type 0x20 structure ....................................................................... 29

5.3.2.2.3 Linkage descriptor with linkage type 0x20 location, occurrence and prioritization ........................ 30

5.3.2.3 Downloadable Font Information Table (DFIT) ..................................................................................... 30

5.3.2.3.1 DFIT structure ................................................................................................................................. 30

5.3.2.3.2 font_info_type in the loop of the DFIS ............................................................................................ 32

5.3.3 IP download fonts ....................................................................................................................................... 33

5.3.4 Broadcast download fonts ........................................................................................................................... 33

5.3.5 Downloaded font file, font name and font-id association ........................................................................... 33

6 IRD requirements ............................................................................................................ ....................... 34

6.1 General support ................................................................................................................................................ 34

6.2 Forward compatibility ...................................................................................................................................... 34

6.3 Support of PSI/SI signalling and subtitle service selection .............................................................................. 34

6.3.1 PSI/SI signalling ......................................................................................................................................... 34

6.3.2 Determining which subtitle services can be rendered ................................................................................. 34

6.3.3 Subtitle service selection ............................................................................................................................ 34

6.4 Font support in IRDs ........................................................................................................................................ 35

6.4.1 Supported fonts and font family name mapping ......................................................................................... 35

6.4.2 Downloadable font retrieval ....................................................................................................................... 35

6.4.3 Font selection for subtitle rendering ........................................................................................................... 36

6.5 Rendering requirements ................................................................................................................................... 36

6.5.1 Playback free-running when A/V sync lost temporarily ............................................................................. 36

6.5.2 Behaviour during trick play ........................................................................................................................ 36

6.5.3 Subtitle composition with HDR video ........................................................................................................ 36

6.5.4 Cropping and scaling of video .................................................................................................................... 37

6.6 Additional TTML processor requirements ....................................................................................................... 37

Annex A (informative): Change History .............................................................................................. 38

History .............................................................................................................................................................. 39

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This European Standard (EN) has been produced by Joint Technical Committee (JTC) Broadcast of the European

Broadcasting Union (EBU), Comité Européen de Normalisation ELECtrotechnique (CENELEC) and the European

NOTE: The EBU/ETSI JTC Broadcast was established in 1990 to co-ordinate the drafting of standards in the

specific field of broadcasting and related fields. Since 1995 the JTC Broadcast became a tripartite body

by including in the Memorandum of Understanding also CENELEC, which is responsible for the

standardization of radio and television receivers. The EBU is a professional association of broadcasting

organizations whose work includes the co-ordination of its members' activities in the technical, legal,

programme-making and programme-exchange domains. The EBU has active members in about

The Digital Video Broadcasting Project (DVB) is an industry-led consortium of broadcasters, manufacturers, network

operators, software developers, regulatory bodies, content owners and others committed to designing global standards

for the delivery of digital television and data services. DVB fosters market driven solutions that meet the needs and

economic circumstances of broadcast industry stakeholders and consumers. DVB standards cover all aspects of digital

television from transmission through interfacing, conditional access and interactivity for digital video, audio and data.

The consortium came together in 1993 to provide global standardization, interoperability and future proof

In the present document "shall", "shall not", "should", "should not", "may", "need not", "will", "will not", "can" and

"cannot" are to be interpreted as described in clause 3.2 of the ETSI Drafting Rules (Verbal forms for the expression of

"must" and "must not" are NOT allowed in ETSI deliverables except when used in direct citation.

Today's broadcast content can be distributed in many forms and via many different paths. Whilst broadcast services

traditionally relied on bitmap-based subtitles because of processing simplicity, advanced processing and text rendering

have made text-based approaches feasible. These offer more flexibility and better options to improve the user

experience. TTML (Timed Text Markup Language) is established as a common solution for IP-based platforms, but

In Europe, the EBU Group 'Subtitles in XML' published the EBU-TT-D TTML profile [20] which was adopted by the

DVB DASH specification as defined in ETSI TS 103 285 [6] and by HbbTV as defined in ETSI TS 102 79 [5]. The

There are only minor differences between EBU-TT-D [3], [20] and IMSC1 Text Profile.

The present specification builds on the existing widespread device support for EBU-TT-D [20], in particular through

support for HbbTV , to enable the distribution of TTML subtitles together with audio/video content via broadcast.

Clause 4 specifies TTML subtitle constraints for a default conformance point, to be supported by both EBU-TT-D [3],

Clause 5 specifies subtitle delivery, including PSI/SI signalling, TS packetisation, TTML segmentation and

The present document specifies the transport of TTML [2] subtitle streams in DVB MPEG-2 transport streams,

based on the MPEG-2 system described in ISO/IEC 13818-1 [1]. TTML is an XML-based representation. The present

document provides syntax for delivery of TTML subtitle streams over MPEG-2 transport stream, and is based on

References are either specific (identified by date of publication and/or edition number or version number) or

non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the

Referenced documents which are not found to be publicly available in the expected location might be found at

NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee

The following referenced documents are necessary for the application of the present document.

[1] ISO/IEC 13818-1: "Information technology -- Generic coding of moving pictures and associated

[2] W3C Recommendation (TTML): "Timed Text Markup Language 1 (TTML1) (Second Edition)".

[4] W3C Recommendation (IMSC1): "TTML Profiles for Internet Media Subtitles and Captions 1.0.1

[6] ETSI TS 103 285: "Digital Video Broadcasting (DVB); MPEG-DASH Profile for Transport of

[7] DVB BlueBook A038: "Digital Video Broadcasting (DVB); Specification for Service Information

NOTE: Available at http://www.dvb.org/resources/public/standards/a038_dvb_spec_december_2017.pdf.

[8] ISO 639-2: "Codes for the representation of names of languages -- Part 2: Alpha-3 code".

[9] ISO/IEC 8859-1: "Information technology -- 8-bit single-byte coded graphic character sets --

[11] ETSI EN 301 192: "Digital Video Broadcasting (DVB); DVB specification for data broadcasting".

[12] ETSI TS 102 809: "Digital Video Broadcasting (DVB); Signalling and carriage of interactive

[13] ETSI TS 102 851: "Digital Video Broadcasting (DVB); Uniform Resource Identifiers (URI) for

[15] DVB BlueBook A126: "Digital Video Broadcasting (DVB); Allocation of identifiers and codes for

NOTE: Available at https://www.dvb.org/resources/public/standards/a126_allocation_identifiers.pdf.

[16] W3C Recommendation (XML): "Extensible Markup Language (XML) 1.0 (Fifth Edition)".

[18] W3C Recommendation 13 December 2012 (WOFF): "Web Open Font Format (WOFF) 1.0".

[19] ISO/IEC 14496-22:2015: "Information technology -- Coding of audio-visual objects --

References are either specific (identified by date of publication and/or edition number or version number) or

non-specific. For specific references, only the cited version applies. For non-specific references, the latest version of the

NOTE: While any hyperlinks included in this clause were valid at the time of publication, ETSI cannot guarantee

The following referenced documents are not necessary for the application of the present document but they assist the

[i.1] W3C Recommendation (WCAG): "Web Content Accessibility Guidelines (WCAG) 2.0".

[i.2] W3C Candidate Recommendation (CSS): "CSS Fonts Module Level 3: Font matching algorithm".

[i.3] IEC 61966-2-1:1999: "Multimedia systems and equipment - Colour measurement and

For the purposes of the present document, the following terms and definitions apply:

Intermediate Synchronic Document (ISD): temporally bounded (possibly empty) subset of TTML content during

NOTE: A TTML document can conceptually be considered as a contiguous sequence of ISDs.

maximum period of activation (MPA): maximum duration a single TTML segment can be active, referred to as T

reserved_zero_future_use: when used in the clause defining the coded bit stream, indicates that the value may be used

NOTE: The present document is structured to allow other types of subtitle segments to be defined in the future. In

subtitle service properties: properties defined by TTML subtitling descriptor which include but are not limited to

subtitle service: service that provides subtitling for an MPEG program (DVB service) with a set of subtitle service