1、 CC Page 1 of 32 pages SMPTE EG 43:2009SMPTE ENGINEERING GUIDELINE System Implementation of CEA-708 and CEA-608 Closed Captioning and Program-Related Data Revision of EG 43-2004 Table of Contents Page Foreword . 3 Intellectual Property 3 Introduction . 3 1 Scope . 4 2 Conformance Notation . 4 3 Term
2、s and Acronyms. 5 3.1 Acronyms and Abbreviations . 5 3.2 Terms . 5 4 Closed Captioning Standards 6 4.1 Relevant CEA Standards . 6 4.2 Relevant SMPTE Standards 7 4.3 Relevant ATSC Standards. 7 4.4 Relevant SCTE Standards. 8 4.5 Relevant DVB/ETSI Standards 9 5 System Configurations. 9 6 Caption Creati
3、on and Encoding . 9 6.1 Captioning Process 9 6.2 CEA-608 Caption Encoding . 10 6.3 CEA-708 Caption Encoding . 11 6.4 CEA-708 Caption Encoding Feeding Direct to the MPEG Encoder 14 6.5 CEA-708 Caption Translation within the MPEG Encoder Using CEA-608 Captions from Line 21 . 14 6.6 Required Level of I
4、mplementation . 15 6.7 Adding Additional DTV Captions after Initial Caption Authoring 15 7 Recording, Processing and Routing 15 7.1 Recording. 16 7.2 VANC Data Bridge . 16 7.3 Video Processing . 17 7.4 Switching Considerations. 17 8 Contribution and Distribution. 17 8.1 Tape Interchange 18 8.2 File-
5、Based Delivery. 18 8.3 Contribution/Distribution Compression Systems 18 Copyright 2009 by THE SOCIETY OF MOTION PICTURE AND TELEVISION ENGINEERS 3 Barker Avenue., White Plains, NY 10601 (914) 761-1100 Approved October 23, 2009 SMPTE EG 43:2009 9 Emission .19 9.1 NTSC Output 20 9.2 ATSC Station Outpu
6、t 20 9.3 Captioning Inputs to an MPEG Emission Encoder.21 9.4 Captioning in AVC Bitstreams 22 9.5 Captioning for ATSC Mobile DTV.22 9.6 Local Live DTV Captions22 9.7 NTSC DTV (Up-Conversion) 23 9.8 DTV NTSC (Down-Conversion)23 9.9 Completeness of CEA-608 Captions, Text, and Program data23 9.10 Consi
7、stency of CEA-708 and CEA-608 Caption Services .24 9.11 Consistency of XDS Data and PSIP Data24 9.12 ANSI/SCTE 127 Data.24 9.13 Server-Based Captioning .24 9.14 Caption Service Descriptor.25 10 Monitoring26 10.1 608 Caption Monitoring 26 10.2 708 Caption Monitoring 26 Annex A Bibliography (Informati
8、ve)28 Annex B Descriptor Enquiry Message Format (Informative)30 Annex C Field-Marked Message Format for CEA-608 Data (Informative).32 Page 2 of 32 pages SMPTE EG 43:2009 Foreword SMPTE (the Society of Motion Picture and Television Engineers) is an internationally-recognized standards developing orga
9、nization. Headquartered and incorporated in the United States of America, SMPTE has members in over 80 countries on six continents. SMPTEs Engineering Documents, including Standards, Recommended Practices, and Engineering Guidelines, are prepared by SMPTEs Technology Committees. Participation in the
10、se Committees is open to all with a bona fide interest in their work. SMPTE cooperates closely with other standards-developing organizations, including ISO, IEC and ITU. SMPTE Engineering Documents are drafted in accordance with the rules given in Part XIII of its Administrative Practices. This SMPT
11、E Engineering Document was prepared by Technology Committee 10E. Intellectual Property At the time of publication no notice had been received by SMPTE claiming patent rights essential to the implementation of this Engineering Guideline. However, attention is drawn to the possibility that some of the
12、 elements of this document may be the subject of patent rights. SMPTE shall not be held responsible for identifying any or all such patent rights. Introduction This section is entirely informative and does not form an integral part of this Engineering Document. Specifications for closed captioning f
13、or NTSC analog television broadcasting1are set out in the CEA-608 standard. Production, distribution and insertion of captioning information to meet these requirements have been implemented for many years using a combination of standards-based and accepted-practice techniques. Specifications for clo
14、sed captioning for ATSC digital television (DTV) in the USA are set out in the CEA-708 standard. The term DTV in CEA-708 includes and applies to HDTV (high definition digital television) and SDTV (standard definition digital television) that use the digital data stream specified in ATSC A/53. CEA-70
15、8 captions are also specified for use in ATSC standard A/72 for AVC (Advanced Video Coding), in SCTE cable systems for both AVC (ANSI/SCTE 128) and SMPTE VC-1 (SCTE 157), as well as in ATSC A/153 for Mobile/ DTV. During the transition from analog to digital broadcasting, analog NTSC and DTV transmis
16、sions will coexist, as will analog and digital cable distribution systems. After the closure of NTSC transmissions, analog and digital television production and distribution systems will possibly coexist in many facilities and networks, frequently with both standard definition (SD) and high definiti
17、on (HD) video formats. This situation creates added complexity for closed captioning as well as other aspects of system implementation. In addition, some multichannel video program distribution systems will continue to distribute NTSC analog signals and in some cases such signals are derived by conv
18、ersion from ATSC DTV signals (see ATSC A/79 for more information). In other cases, NTSC signals will be derived from ATSC DTV signals by a consumer digital converter box. CEA-708 specifies standards for encoding and decoding DTV closed captions (DTVCC) but provides little guidance on system design a
19、nd interfacing for DTVCC in broadcast systems. 1NTSC broadcasting from full-power NTSC stations in the USA ended in June 2009 but NTSC transmissions from low-power stations and translators will continue for some time after that date. NTSC broadcasts also continue in other countries. Page 3 of 32 pag
20、es SMPTE EG 43:2009 1 Scope The primary purpose of this guideline is to provide guidance for system implementation of closed captioning for DTV as defined in CEA-708, concentrating on different techniques that are required for DTVCC implementation when compared to CEA-608 captioning systems for NTSC
21、. It also provides guidance on distribution of certain program-related data carried in the CEA-608 data construct. It identifies the relevant standards that exist for different parts of the system and, where possible, indicates guidelines for areas that are not standardized. This guideline describes
22、 methods that can be used to support the various links in the chain from caption creation through to emission. Consideration is given to systems that support captioning for SD and HD program material, which can originate and/or be distributed in standard formats as used in broadcasting and related f
23、acilities. While CEA-708 refers specifically to DTV implemented for mainstream ATSC broadcast systems, techniques described herein are applicable for programming for other DTV environments such as ATSC Mobile DTV and cable or satellite distribution. In this guideline, transport for distribution of D
24、TVCC within the broadcast plant is based primarily on the use of SMPTE 334-1, which define a method of embedding DTVCC and other data services in the vertical ancillary (VANC) data space of video signals conforming with SMPTE 292 high-definition serial digital interface (HD-SDI) or SMPTE 259M serial
25、 digital interface (SDI). HD-SDI in this guideline refers to bit-serial component 1080 or 720 line television signals. SDI in this guideline refers to bit-serial component 525-line television signals. The carriage of DTVCC over serial data links in accordance with SMPTE 333 or RP 2007 is also includ
26、ed, together with arrangements for distributing caption service information. Reference is made to alternative server-based methods of distributing and managing closed captioning. A method for carriage of DTVCC caption data in an AES3 data stream is specified in SMPTE 337M. Further details of that ar
27、rangement are not described here. 2 Conformance Notation Normative text is text that describes elements of the design that are indispensable or contains the conformance language keywords: “shall“, “should“, or “may“. Informative text is text that is potentially helpful to the user, but not indispens
28、able, and can be removed, changed, or added editorially without affecting interoperability. Informative text does not contain any conformance keywords. All text in this document is, by default, normative, except: the Introduction, any section explicitly labeled as “Informative“ or individual paragra
29、phs that start with “Note:” The keywords “shall“ and “shall not“ indicate requirements strictly to be followed in order to conform to the document and from which no deviation is permitted. The keywords, “should“ and “should not“ indicate that, among several possibilities, one is recommended as parti
30、cularly suitable, without mentioning or excluding others; or that a certain course of action is preferred but not necessarily required; or that (in the negative form) a certain possibility or course of action is deprecated but not prohibited. The keywords “may“ and “need not“ indicate courses of act
31、ion permissible within the limits of the document. The keyword “reserved” indicates a provision that is not defined at this time, shall not be used, and may be defined in the future. The keyword “forbidden” indicates “reserved” and in addition indicates that the provision will never be defined in th
32、e future. A conformant implementation according to this document is one that includes all mandatory provisions (“shall“) and, if implemented, all recommended provisions (“should“) as described. A conformant implementation need not implement optional provisions (“may“) and need not implement them as
33、described. Page 4 of 32 pages SMPTE EG 43:2009 Unless otherwise specified, the order of precedence of the types of normative information in this document shall be as follows. Normative prose shall be the authoritative definition. Tables shall be next, followed by formal languages, then figures, and
34、then any other language forms. 3 Terms and Acronyms 3.1 Acronyms and Abbreviations AES3: AES standard for serial digital audio ATSC: Advanced Television Systems Committee CDP: Caption Distribution Packet CEA: Consumer Electronics Association CSD: Caption Service Descriptor DTVCC: DTV Closed Captions
35、 DTV: Digital Television EIT: Event Information Table NTSC: National Television System Committee PSIP: Program and System Information Protocol HD-SDI: High Definition Serial Digital Interface (compliant with SMPTE 292) SCTE: Society of Cable Telecommunications Engineers SDI: Serial Digital Interface
36、 (compliant with SMPTE 259M) VANC: Vertical ANCillary (data space) 3.2 Terms Caption Encoder: A device that encodes closed caption data and inserts it into a video signal. The term is used both for equipment inserting CEA-608 captions (as line 21 data) and for equipment inserting CEA-708 captions (u
37、sually in the form of CDPs carried in VANC). This term must not be confused with an emission or MPEG encoder. Caption Server: (1) a computer that sends data from a caption intentions file (produced by a caption author) to a caption encoder. (2) In SMPTE 333 the term is used to refer to a device that
38、 delivers DTV closed caption formatted data to an MPEG Encoder for insertion in a video elementary stream. Emission encoder: A compression encoder processing video, audio, and associated data services. As used in this document the video is compressed as MPEG-2 and the audio as AC-3. The emission enc
39、oder outputs an MPEG-2 Transport Stream per ATSC A/53. MPEG Encoder: Device which compresses video, audio, and associated data using (historically) MPEG-2. In this document, this term is understood to be generalized to include additional compression standards, including AVC and SMPTE VC-1. Page 5 of
40、 32 pages SMPTE EG 43:2009 Uplink encoder: A compression encoder processing video, audio, and associated data services for a Contribution/Distribution system. Video compression might be MPEG-2, AVC, VC-1 or any other suitable video compression codec. Audio compression might be AC-3, MPEG-1 Layer II
41、or any other suitable audio compression codec. Care must be taken in discussing closed captioning with program and captioning providers to avoid using the ambiguous term “subtitles”. Use of this term can lead to misunderstanding, particularly with international communications, as the term “subtitles
42、” is well defined in other contexts which do not match the use of CEA-708 (or CEA-608) captions. In these circumstances, the term “open captions” might be used in preference to “subtitles” to make clear the distinction from closed captions. 4 Closed Captioning Standards The role of the primary stand
43、ards relating to captioning can be summarized as follows: 4.1 Relevant CEA Standards 4.1.1 CEA-608 CEA-608 defines the coding of data, including captioning, which is carried in line 21 (and line 284) of an analog NTSC video signal or (as a digitized analog waveform) in line 21 of an SDI digital vide
44、o signal. It includes the specifications and techniques for encoding, insertion, extraction, re-encoding, transmission, reception, and display of caption data and defines non-caption data that can be carried, including Text Mode data service and Extended Data Service (XDS), which can include informa
45、tion about the program, content advisory, and various other data. CEA-608 refers only to encoding data on line 21, but the data structures defined can be used to carry information on other lines in the video signal, usually in the vertical blanking interval. Such alternative uses are not covered in
46、this guideline. In this guideline, captions generated in accordance with the CEA-608 standard are referred to as CEA-608 captions; they are sometimes referred to simply as “608” captions. 4.1.2 CEA-708 CEA-708 defines the coding of DTVCC as they are delivered in an ATSC A/53 emission bitstream, and
47、is applicable equally to HD and SD video formats, and to terrestrial broadcasting and cable and satellite distribution. It includes a description of the specific data packets and structures of DTVCC. The standard provides a specification of how caption information is to be coded and processed, minim
48、um implementation recommendations for DTV closed caption decoders, and recommended practices for DTV closed caption encoder and decoder manufacturers. Caption data delivered in an ATSC bitstream includes the data required for use by a DTV integrated receiver or set-top box to display DTV captions, o
49、ften referred to as “708” data. It also includes CEA-608 data required for use by DTV set-top boxes so that line 21 data can be inserted in an NTSC output (if provided) to feed an analog TV set. The CEA-608 data also enables line 21 captioning and data insertion for any other equipment that needs to produce an NTSC output from a down-converted HD stream. CEA-708 indicates that DTV receivers are allowed to use CEA-608 caption data when CEA-708 data is not available for providing closed captioningnote this is not mandatory a
