SMPTE EG 432-1-2010 Digital Source Processing Color Processing for D-Cinema《数字资源处理 数字电影的彩色处理》.pdf

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1、 Table of Contents Page Foreword . 3 Intellectual Property 3 Introduction 3 1 Scope 5 2 Conformance Notation 5 3 Order in which the Color Processing Steps are Described . 6 4 Flow of Color through the Digital Cinema System 64.1 Digital Source Master . 6 4.2 D-Cinema Image Color Flow Diagram . 6 4.3

2、Reference Projector Input Color Data Flow . 7 4.4 Exhibition Projector Input Color Data Flow 7 5 D-Cinema Colorimetry Encoding 85.1 Equations for DCDM Color Encoding 9 5.2 Equations for DCDM Color Decoding 10 5.3 Comments on the DCDM Encoding and Decoding Equations 10 6 Measurings of Projected Image

3、s 11 6.1 Measuring Equipment 12 6.2 Measuring Locations within the Review Room or Exhibition Theater 13 6.3 Projector and Theater Environment . 13 6.4 Measurement and Ambient Light . 13 6.5 Measurement of the Luminance of White 13 6.6 Measurement of the Luminance of Theater Black . 15 6.7 Measuremen

4、t of the Sequential Contrast 15 6.8 Measurement of Intra-Frame (Checkerboard) Contrast 16 6.9 Visual Verification of Gray Scale Tracking . 16 6.10 Visual Assessment of Contouring 18 6.11 Measurement of the Transfer Function Exponent . 18 6.12 Measurement of the Color Gamut (Color Primaries) . 18 6.1

5、3 Specification of the Color Accuracy of any Displayed Colors 19 7 Conversion of Reference Projector RGB Code Values to DCDM Code Values and then to Linear Projector Code Values . 207.1 Background and Theory . 20 7.2 Derivation of the RGB-to-XYZ and XYZ-to-RGB Matrices, General Equations 21 Page 1 o

6、f 81 pages SMPTE EG 432-1:2010 Revision of EG 432-1-2007 SMPTE ENGINEERING GUIDELINE Digital Source Processing Color Processing for D-Cinema Copyright 2010 by THE SOCIETY OF MOTION PICTURE AND TELEVISION ENGINEERS 3 Barker Avenue, White Plains, NY 10601 (914) 761-1100 Approved November 10, 2010 SMPT

7、E EG 432-1:2010 Page 2 of 81 pages 7.3 Derivation of the RGB-to-XYZ and XYZ-to-RGB Matrices, Reference Projector . 22 7.4 Explanation of Annex C in SMPTE RP 431-2, Reference Projector (conversion example for RGB to XYZ to XYZ) . 24 8 Gamut Mapping and the Value of the Mastering Projector Metadata 28

8、 9 An Example of Color Processing through the Entire System . 32 9.1 Specification of Color in the DSM 32 9.2 Conversion froom the DSM Film Printing Density Color Encoding to XYZ . 39 Annex A Bibliography (Informative) 41Annex B Encoding Schemes Considered (Informative) 43 Annex C Location of the En

9、coding Primaries (Informative) 45 Annex D Reason for the Constant 2.6 (Informative) 47 Annex E Reason for the Constant 4095 (Informative) 50 Annex F Minimum Linear RGB Bit Depth Needed in the Reference Projector (Informative) . 53 Annex G Reason for the Constant 52.37 (Informative) 55 Annex H Encodi

10、ng White Points Considered (Informative) 60 Annex I Encoding of Colorimetry above Theater Black (Informative) . 61 Annex J Conversions among xyY, XYZ and XYZ (Informative) . 64 Annex K Calculation of the NPM using the Method in RP 177 (Informative) . 66 Annex L Description of CIELab Space and Delta

11、E*ab (Informative) 71 Annex M Explanation of Annex B in SMPTE 428-1 (Informative) . 76 Annex N Glossary and Acronyms (Informative) . 77 SMPTE EG 432-1:2010 Page 3 of 81 pages Foreword SMPTE (the Society of Motion Picture and Television Engineers) is an internationally-recognized standards developing

12、 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, Recommended Practices and Engineering Guidelines, are prepared by SMPTEs Technology Committees. Participation in

13、 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 Documents are drafted in accordance with the rules given in Part XIII of its Administrative Practices. SMPTE

14、 EG 432-1 was prepared by SMPTE Technology Committee 21DC. Intellectual Property At the time of publication no notice had been received by SMPTE claiming patent rights essential to the implementation of this Standard. However, attention is drawn to the possibility that some of the elements of this d

15、ocument may be the subject of patent rights. SMPTE shall not be held responsible for identifying any or all such patent rights. Introduction The work that led to the writing of the SMPTE standards on the color encoding for Digital Cinema has been guided by a few underlying principles. They are: 1. T

16、he most important desire was to define a color encoding that allows for excellent image quality in all exhibition theatres. The color quality of the image ought not be limited by the encoding. The image produced in one theatre should, within tight tolerances, match the image produced in any other th

17、eatre. This led to some decisions that create technical challenges for the production workflows today and that may lead to (slightly) increased cost of a complete system, but it was felt that the ability to produce excellent quality in a theatre is sufficiently important that these challenges were a

18、ccepted. 2. It was desired that the encoding be designed so that it would encompass a color gamut at least as large as existing digital projectors and preferably include all possible film colors. In addition, there was a desire to write a standard that would allow future improvements in display tech

19、nology to be carried in the digital cinema encoding that is now being defined. 3. It was desired that the encoding should not be tied to any particular device or technology. This has become known as device-independent encoding. Device-independent encoding does not, in itself, lead to a robust encodi

20、ng, but when coupled with other parameters, it can lead to a robust encoding. 4. It was desired that the digital cinema color encoding be designed to be relatively simple to implement so that images can be processed and projected in real time. 5. The color encoding standardized by SMPTE is only for

21、the Digital Cinema Distribution Master. There has been considerable discussion of the encoding for the Digital Source Master, the digital master that precedes the Distribution Master. However, that master is produced in a post-house and it was felt that the post-house could create that Source Master

22、 in any file format and color space it wanted. Likewise, the production of the Distribution Master from the Source Master is dependent on the form of the Source Master, so that transform cannot be standardized. However, because it is an important topic for many people, comments on the transform from

23、 the Source Master to the Distribution Master will be given in this guideline. SMPTE EG 432-1:2010 Page 4 of 81 pages This Engineering Guideline only deals with the color processing of digital images that a digital projector will display in a theatre. Therefore, the container for the digital images,

24、 the file format of the code values, and the transport of that container are not a part of this guideline. Digital Cinema, or D-Cinema as it is also known, is based on the technology of defining an image by a set of code values (numbers). The definition of any single color requires three, and only t

25、hree, code values. In addition, a set of three code values defines one, and only one, color. There has to be a color system defined in which the code values are directly related to the colors. The SMPTE documents ST 428-1, ST 431-1, ST 431-2, and ST 431-3, listed in the Annex A (Bibliography), defin

26、e this color system. This guideline explains how to use those documents to implement that color system. The overarching objective is to define a system in which an image will be displayed in any theatre by any projector and the result will be the same within a reasonable set of tolerances. In order

27、to achieve this objective, there are three elements of the system that have to be defined: (1) The relationship between the code values and the encoded color. (2) The measurement of the light reflected off the screen. (3) The aims and tolerances around each measurement. The cited SMPTE documents and

28、 this guideline explain each of these elements of the system and how to put all the elements together to make a working system. The color encoding for the D-Cinema system is based on the definition of the image that is to be displayed on the screen. Therefore, the SMPTE documents standardize how to

29、define the relationship between the code values and the desired colors, but do not deal with how one is to define the desired colors. It is realized that in the normal production of moving images, the image has to somehow be created before the colors in the D-Cinema image can be defined. The term, D

30、igital Source Master, has been used to define this original image because it may be the source of many different digital images, the D-Cinema images, the HDTV images, the DVD images, etc. There are three reasons why the Digital Source Master has not yet been defined by any of the SMPTE documents: (1

31、) The Digital Source Master comes before the D-Cinema images. (2) The method by which the images in the Digital Source Master are created is up to the creator. (3) The Digital Source Master can be defined in a large number of different, useful ways. To a large extent the encoding and decoding of the

32、 D-Cinema images revolves around the Reference Projector. The Reference Projector is a working, practical projector that is defined by its capabilities, not by its technology. It is recognized that there may be many technical solutions to the problem of constructing a projector that has the capabili

33、ties that the Reference Projector must have. The Reference Projector capabilities are the minimum capabilities any physical projector must have, but these capabilities are not meant to be limiting capabilities. A physical projector may have capabilities beyond the capabilities of the Reference Proje

34、ctor. Therefore, the technologies used to build a physical projector are not discussed in any of the SMPTE documents; only the capabilities are described. There have to be uniform methods by which the light reflected by a screen can be measured in order to know if the capabilities of any physical pr

35、ojector meet the capabilities of the Reference Projector. In addition, it is recognized that because physical devices will always have variation in performance across different devices and across time for any single device, there have to be reasonable tolerances within which all devices can work and

36、 which will ensure that the images are visually the same in all theatres. The RGB or XYZ or similar triplets of numbers in this Engineering Guideline are always in the order in which they are listed. For example, if a variable is called RGB and the numbers 100 200 300 are an example of the RGB value

37、s, the 100 represents the R value, the 200 represents the G value and 300 represents the B value. The matrices that operate on the RGB or XYZ values are defined for the same order of individual variables. The reason for stating what seems so obvious is that some devices do not follow the order RGB.

38、Where this can cause problems is in the definition of the matrices that go from RGB to XYZ and XYZ to RGB. Therefore, when a matrix is put into a projector (or other device), the user must be certain the matrix and the device are using the individual variables in the same order. The CIE XYZ tristimu

39、lus values, described in the CIE references in the Bibliography, are linearly related to light. But because the human visual system does not respond to light in a linear fashion, the encoding of the CIE XYZ values is more efficient if a function of the XYZ values is encoded instead of the XYZ values

40、 SMPTE EG 432-1:2010 Page 5 of 81 pages themselves. These encoded XYZ values are given the symbols XYZ in the SMPTE documents relating to Digital Cinema. This encoding is the main subject of this Engineering Guideline. This EG is entirely Informative. Stated values are not to be used for equipment d

41、esign. The user should refer to the appropriate Standard or RP for target values and tolerances. 1 Scope This document provides guidelines on the encoding of the color information for the Digital Cinema Distribution Master (DCDM) and for the decoding of the color signal in the projector. A series of

42、 standards and recommended practices define exactly what to do to encode and decode the color for digital cinema. This document leads the user through all of those documents so that an image, once created, will both match the creators intent and will be displayed as the same image in every theatre w

43、ithin the recommendations of these documents. In addition to the guidelines on how to do the color encoding and color processing, this document will give some historical background on the development of the color encoding. In order to make this document more readable, the historical information will

44、 be put in a series of annexes after the guidelines. Therefore, this document describes the color transformations required for encoding an image into the DCDM XYZ code values in mastering and the reciprocal process of decoding these code values in the exhibition projector. Because the appearance of

45、any color patch is dependent on the viewing conditions under which the color patch is seen, this document will also describe how the contents of the standards and recommended practices relating to the display of images using digital projection relate to the color encoding and decoding. The purpose o

46、f this guideline is to show how to use all of the Digital Cinema color-related documents in order to achieve the objectives of interoperability and color consistency. 2 Conformance Notation Normative text is text that describes elements of the design that are indispensable or contains the conformanc

47、e language keywords: “shall“, “should“, or “may“. Informative text is text that 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 thi

48、s document is, by default, normative, except: the Introduction, any section explicitly 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 de

49、viation is permitted. The keywords, “should“ and “should not“ indicate that, among 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 keywords “may“ and “need not“ indicate courses of action permissible within the limits of the document. The keyword “reserved” indicates a provision th