SMPTE EG 2046-3-2010 Safe Areas for Television《电视安全区域》.pdf

1、 Copyright 2010 by THE SOCIETY OF MOTION PICTURE AND TELEVISION ENGINEERS 3 Barker Avenue., White Plains, NY 10601 (914) 761-1100 Approved February 23, 2010 Table of Contents Page Foreword . 2 Intellectual Property 2 1 Scope . 3 2 Conformance Notation . 3 3 Normatice References . 3 4 History of Tele

2、vision Safe Areas 3 5 The New Specifications 5 6 A Use Case 5 Annex A Bibliography (Informative) 6 Annex B Television Receiver Picture Area Losses . 7 Page 1 of 8 pages SMPTE EG 2046-3:2010 SMPTE ENGINEERING GUIDELINE Safe Areas for Television SMPTE EG 2046-3:2010 Page 2 of 8 pages Foreword SMPTE (t

3、he Society of Motion Picture and Television Engineers) is an internationally-recognized standards developing organization. Headquartered and incorporated in the United States of America, SMPTE has members in over 80 countries on six continents. SMPTEs Engineering Documents, including Standards, Reco

4、mmended Practices, and Engineering Guidelines, are prepared by SMPTEs Technology Committees. Participation in these 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

5、 Documents are drafted in accordance with the rules given in Part XIII of its Administrative Practices. SMPTE EG 2046-3 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 implementat

6、ion of this Engineering Guideline. However, attention is drawn to the possibility that some of the 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. SMPTE EG 2046-3:2010 Page 3 of 8 pages 1 Scope SMPTE ha

7、s several Standards and Recommended Practices on safe areas for television. Among these are SMPTE ST 2046-1, SMPTE RP 2046-2, SMPTE RP 218, and SMPTE RP 27.3. It is the purpose of this Engineering Guideline to explain the use of these documents and the relationships among them and others, principall

8、y SMPTE ST 2016-1. A brief history of TV safe areas and their evolution is also given. 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

9、is potentially helpful to the user, but not indispensable, 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 expl

10、icitly labeled as “Informative“ or individual paragraphs 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, amon

11、g several possibilities, one is recommended as particularly 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 k

12、eywords “may“ and “need not“ indicate courses of action 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

13、that the provision will never be defined in the future. 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 figu

14、res; and then any other language forms. 3 Normative References The following standards contain provisions which, through reference in this text, constitute provisions of this recommended practice. At the time of publication, the editions indicated were valid. All standards are subject to revision, a

15、nd parties to agreements based on this recommended practice are encouraged to investigate the possibility of applying the most recent edition of the standards indicated below. None. 4 History of Television Safe Areas From the early days of film and television, it has been recognized that not all of

16、the information contained in the original image frame will necessarily be presented to the viewer. In television, the principal limitation has been the use of overscan in the viewers receiver. In 1957, the SMPTE Journal included a paper entitled Television Receiver Picture Area Losses, in which the

17、author, Charles Townsend, describes research conducted at NBCs WRCA-TV in an effort to determine the extent of the broadcast image that was actually seen in viewers homes. The paper is reproduced in Annex B. Note that the safe area the author suggests is based on the assumption that all elements wit

18、hin the safe area will be viewable on at least 85% of receivers; no attempt is made to ensure viewability on 100% of receivers. SMPTE EG 2046-3:2010 Page 4 of 8 pages The safe area pattern recommended is 80% of image height and approximately 80% of image width, adjusted for the shape of the mask, wh

19、ich reflects the circular shape of the CRTs then in use. Two letters to the editor of the Journal, published in May 1958, noted prior tests conducted in 1947 by Otis Freeman, then at DuMont, which had been published in the March 1948 issue of Television magazine. Mr. Freeman obtained very similar re

20、sults. As a consequence, the following standard practice was included in the DuMont Television Networks Engineering Standards Handbook: All studio monitors shall be marked with lines to indicate full raster size and 10% margins on either side and at top and bottom. Engineering personnel will advise

21、program personnel to keep important program material within these limits. The 10% margins cited yield a safe area of 80% of picture width and 80% of picture height. In 1961, SMPTE issued SMPTE RP 8, Safe Title Area for TV Transmission, which specified this 80% width, 80% height rectangle with rounde

22、d corners as the Safe Title Area. This was followed in 1963 by SMPTE RP 13, Safe Action Area for TV Transmission, which specified a 90% width, 90% height rectangle with rounded corners as the Safe Action Area. In 1968, the two RPs were combined into a revised SMPTE RP 8. 1972 saw the publication of

23、SMPTE RP 27.3, Specifications for Safe Action and Safe Title Area Test Pattern for Television Systems, which specified a test pattern for 2 x 2 slides and 16mm and 35mm motion-picture film for television. This replaced SMPTE RP 8, maintaining the same dimensions and shapes of the safe areas. In 2002

24、, SMPTE issued SMPTE RP 218, which brought the specification forward into the digital era by specifying safe areas in terms of pixel and line counts rather than linear dimensions. The rounded corners were also eliminated, as by that time consumer CRTs had square corners. Although superseded, SMPTE R

25、P 27.3 was kept on the books for archival purposes. All of these specifications and test patterns were based on the characteristics of CRT-based displays, including rounded corners (except in SMPTE RP 218) and safe-area margins large enough to compensate for centering and geometry errors and the ove

26、rscan necessary to ensure that the CRT was completely filled with an image even when the receivers components had aged or the line voltage sagged. These specifications a safe action area 90% of the width and 90% of the height of the full image area and a safe title area 80% of the width and 80% of t

27、he height of the full image area persisted until near the end of the first decade of the 21st century, despite significant improvements in CRT-based receiver technology. By 2007-2008 it had become obvious that the CRT was rapidly being replaced by fixed-pixel-matrix (FPM) displays (plasma, LCD, DLP,

28、 etc.) While these technologies have significant differences among them, one characteristic they share is fixed image geometry. No longer is the consumer display subject to changing picture size due to conditions beyond the manufacturers control. Moreover, since the early 2000s many broadcasters had

29、 been utilizing the space between the safe action area and the safe title area for news crawls and other title information, knowing that on modern CRT displays as well as FPM displays this information was virtually certain to be legible. Another complicating factor was the wide adoption of the 16:9

30、aspect ratio, making it necessary to create images that would be acceptable on both 4:3 and 16:9 displays. Based on these facts, several broadcast organizations around the world determined it was time to widen the safe areas and asked SMPTE to investigate. SMPTE responded by establishing a Working G

31、roup on Safe Areas and under it an Ad Hoc Group on Television Safe Areas, reporting to Technology Committee 10E. The result was the development of a new Standard, SMPTE ST 2046-1, a new Recommended Practice, SMPTE RP 2046-2, and an amendment to SMPTE RP 218. Many broadcasters had hoped that it would

32、 be possible to utilize the entire active picture area as the safe action area. However, for a variety of reasons, FPM-based consumer receivers, even if they are adjustable to show the entire image area, commonly default to a small amount of overscan to conceal image processing and compression edge

33、artifacts. Moreover, although CRT-based receivers are no longer sold, large numbers of them remain in use. Based on research in the U. S., Europe and Japan, the specifications in SMPTE ST 2046-1 and SMPTE RP 2046-2 were adopted. SMPTE EG 2046-3:2010 Page 5 of 8 pages One aspect of the safe area spec

34、ifications that has not changed, however, is that there is no ironclad guarantee that the entire safe action area or safe title area will be displayed on all television receivers. Given the advances in display technology since 1957, far more than 85% of consumer displays in the field are capable of

35、doing so, but it is not possible to assert that all are. 5 The New Specifications SMPTE ST 2046-1 defines the Safe Action Area as a rectangle that is 93% of the width and 93% of the height of the Production Aperture (or 720 x 480 in the case of 480-line formats) and concentric with it. The Safe Titl

36、e Area is defined as a rectangle that is 90% of the width and 90% of the height of the Production Aperture (or 720 x 480 in the case of 480-line formats) and concentric with it. Annex C of the Standard provides informative tables giving the dimensions of these safe areas in terms of lines and pixels

37、 for the most commonly used image formats. Annex D provides example safe area graticules for both 4:3 and 16:9 aspect ratios, as well as a graticule for 4:3 images using the legacy safe area percentages. SMPTE RP 2046-2 defines safe areas that should be used when composing 16:9 images that will be p

38、resented on both 4:3 and 16:9 displays. Two example graticules are defined, one for use when the 4:3 image is to be created by cropping the sides of the 16:9 image and the other for use when the full 16:9 image is to be presented in a letterbox on the 4:3 display. These are described in the context

39、of the Active Format Description (AFD) specifications defined in SMPTE ST 2016-1. SMPTE RP 2046-2 defines only 90%, 90% safe areas. Amendment 1 to SMPTE RP 218 deprecates its use except for formatting of closed captions as defined in CEA-708. The exception exists because all receivers deployed in co

40、untries that require the use of CEA-708 display captions in a window whose extents are defined by the old 80% width, 80% height safe title area defined in SMPTE RP 218. CEA-708 normatively references SMPTE RP 218. For all other applications, the amended RP directs users to SMPTE ST 2046-1 and SMPTE

41、RP 2046-2. 6 A Use Case As an example of how to use the new documents, let us suppose that we wish to create images for a broadcast. We will produce in 1920 x 1080 for broadcast in 1920 x 1080, but recognize that the broadcast will be viewed both on 16:9 HD displays and on legacy 4:3 displays via do

42、wn-conversion. ST 2046-1 gives us the safe action and safe title area percentages, as well as the line and pixel counts for 1920 x 1080 formats and an example graticule. However, we need to take account of the down-conversion for 4:3 displays, so we need to look at SMPTE RP 2046-2. SMPTE RP 2046-2 t

43、ells us that we first need to determine whether the 4:3 images will be center-cut from the 16:9 images or whether they will be letterboxed. As the RP notes, this is dictated by both creative and business factors. Let us assume that these impel us to determine that the images will be center-cut, so w

44、e need to shoot to protect the 4:3 central area. These safe areas are defined in Section 4.1 of the RP; its Figure 1 gives us the graticule and its Table 1 gives us the dimensions in terms of lines and pixels. We find that the Safe Area is 972 lines high by 1296 pixels wide. This is the Safe Area fo

45、r both titles and action, but not for captions. On a 4:3 display, captions will be limited to 80% of the width and 80% of the height of the center-cut area. SMPTE RP 218 tells us the height directly; it is 864 lines. We need to calculate the width, which is 80% of the center cut width, given in SMPT

46、E RP 2046-1 as 1440 pixels. 80% of this is 1152, so the area of the source image to which captions will be limited in 4:3 is 1152 x 864. The other thing SMPTE RP 2046-2 tells us is that images shot in 16:9 to protect a 4:3 central area should have an AFD of 1111. For a detailed explanation of what t

47、his means and how AFD works, see SMPTE ST 2016-1. SMPTE EG 2046-3:2010 Page 6 of 8 pages Annex A (Informative) Bibliography SMPTE 2016-1:2008, Format for Active Format Description and Bar Data SMPTE ST 2046-1:2009, Specifications for Safe Action and Safe Title Areas for Television SMPTE RP 8-1968, S

48、afe Title Area for TV Transmission (Withdrawn) SMPTE RP 13-1963, Safe Action Area for TV Transmission (Withdrawn) SMPTE RP 27.3-1989, Specifications for Safe Action and Safe Title Area Test Pattern for Television Systems SMPTE RP 218:2009, Specifications for Safe Action and Safe Title Areas for Tele

49、vision Systems SMPTE RP 2046-2:2009, Television Safe Areas for Protection of Alternate Aspect Ratios CEA-708-D (August 2008), Digital Television (DTV) Closed Captioning Chipp, Rodney D., Letter to the Editor, JSMPTE, Volume 67, Page 343, May 1958 Freeman, Otis, Letter to the Editor, JSMPTE, Volume 67, Page 343, May 1958 Townsend, Charles L., Television Receiver Picture Area Losses, JSMPTE, Volume 66, Pages 758-759, December 1957 (reprinted as Annex B below) SMPTE EG 2046-3:2010 Page 7 of 8 pages Annex B Television Receiver Pi