SMPTE RP 2077-2013 Full-Range Image Mapping.pdf
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1、Page 1 of 18 Approved November 7, 2013 Copyright 2013 by THE SOCIETY OF MOTION PICTURE AND TELEVISION ENGINEERS 3 Barker Avenue, White Plains, NY 10601 (914) 761-1100 SMPTE RP 2077:2013 SMPTE RECOMMENDED PRACTICE Full-Range Image Mapping Page 1 of 18 pages Table of Contents Foreword 2 Intellectual P
2、roperty . 2 Introduction 2 1 Scope 5 2 Conformance Notation 5 3 Normative References 5 4 Terms and Definitions . 6 5 Mapping to Interfaces and Formats that Rely upon Protected Code Values . 6 6 Mapping to Interfaces and Formats with Narrow-Range Image . 7 Annex A Bibliography (Informative) 8 Annex B
3、 Mapping to and from a 10-Bit Interface that Relies upon Protected Code Values (Informative) . 9 Annex C Example Mappings to and from a Format with Narrow-Range Image (Informative) 10 SMPTE RP 2077:2013 Page 2 of 18 pages Foreword SMPTE (the Society of Motion Picture and Television Engineers) is an
4、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, Recommended Practices, and Engineering Guidelines, are prepared b
5、y 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 Documents are drafted in accordance with the rules given in
6、Part XIII of its Operations Manual. SMPTE RP 2077 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 Document. However, attention is drawn to the po
7、ssibility 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. Introduction This section is entirely informative and does not form an integral part of this Engineering Document. Each pixel i
8、n a digital image is commonly encoded as a triplet of n-bit binary words see, for instance, SMPTE ST 125, SMPTE ST 274 and ST SMPTE 296 for the process by which such encoding is generated. In a full-range digital image, the code values of the reference black and white triplets are the minimum and ma
9、ximum values that can be encoded by an n-bit unsigned binary integer, (0, 0, 0) and (2n 1, 2n 1, 2n 1) respectively, i.e. the “full range“ of code values. This specification defines mappings allowing source full-range images to be carried by (i) digital interfaces that rely upon protected values, e.
10、g. for synchronization, and (ii) narrow-range digital image formats where the full-range of code values is not utilized for the range between reference black and white11The terms “reference black“ and “reference white“ have the same meanings herein as in SMPTE ST 125, SMPTE ST 274 and SMPTE ST 296,
11、which state “picture information shall be linearly represented by red, green and blue tristimulus values (RGB), lying in the range 0 (reference black) to 1 (reference white)“. . These mappings can be used to devise methods to interoperate with analog workflows, but those methods are outside the scop
12、e of this document. On digital interfaces that rely upon protected values, a small number of code values are prohibited from appearing in triplets. For instance, the 10-bit interface defined in SMPTE ST 292-1 protects code values outside the range 4,1019. SMPTE RP 2077:2013 Page 3 of 18 pages 410194
13、10191023010230Full-Range ImageInterfacewith Protected Code ValuesFull-Range ImageFigure 1 Full-Range Image Mapping over an Interface that Rely upon Protected Code Values In this first scenario, Section 4.1 specifies that, given a full-range image as input, code values falling within the protected ra
14、nge are clipped to the closest permitted value without any scaling. As illustrated in Figure 1, no additional processing is required if the resulting narrow-range image is mapped back to full-range at a later time, but the resulting full-range image will be missing any code value clipped by the init
15、ial mapping to the digital interface. In narrow-range digital image formats, the reference black and white triplets, (RBLACK, RBLACK, RBLACK) and (RWHITE, RWHITE, RWHITE) respectively, are specified with RBLACK0 and RWHITEb The function Mpermittedfull(“map from permitted range to full-range“) shall
16、map a code value CVPon the interface or format to a code value CVFULLfor the full-range image according to Mpermittedfull: CVP CVFULL= CVP (2) Note: Any information in a full-range image encoded using code values outside the range CVLOW, CVHIGH is lost in this mapping. Equivalently, full-range image
17、s sourced from an interface or format with protected code values will not contain code values outside the range CVLOW, CVHIGH. Annex B contains an illustrative mapping to and from a 10-bit interface with CVLOW = 4and CVHIGH= 1019. SMPTE RP 2077:2013 Page 7 of 18 pages 6 Mapping to Interfaces and For
18、mats with Narrow-Range Image The following applies when mapping a full-range image to a format or interface that uses narrow-range images of the same bit length n. The function Mfull narrow(“map from full-range to narrow-range“) shall map a code value CVFULLfrom a full-range image to a narrow-range
19、code value CVNon the interface or format according to: Mfull narrow: CVFULL CVN= floor ( 0.5 + CVFULL/ (2n-1) (RWHITE RBLACK) + RBLACK), (3) where floor(x) is equal to the largest integer not greater than x. The function Mnarrowfull(“map from narrow-range to full-range“) shall map a code value CVNfr
20、om the interface or format to a full-range code value CVFULLaccording to Mnarrowfull: CVN CVFULL= floor ( 0.5 + clamp ( 0.0, 1.0, (CVN- RBLACK) / (RWHITE RBLACK) ) (2n-1) ) , (4) where floor(x) and clamp(a, b, x) use the same definitions as in the previous section. Notes: 1 floor(0.5 + x) expresses
21、rounding of positive x to the nearest integer. 2 No slopes, curves, knee or shoulder are specified at the top and bottom of the mapping interval. 3 The pair of equations above are constructed such that Mfull narrow(Mnarrow full( Mfull narrow( x ) ) ) = Mfullnarrow( x ), i.e. once a full-range value
22、has been mapped to a narrow-range value (and quantization information necessarily lost), no further information is lost if the mapping is repeated. 4 CVNin Equation (4) can be smaller than RBLACKor larger than RWHITE, but any information outside the range RBLACK, RWHITE is lost when mapping from nar
23、row-range to full-range using Mnarrowfull, i.e. Mnarrowfullclips code-values outside the range RBLACK, RWHITE. If such clipping is not desired, code values outside the range RBLACK, RWHITE can be mapped to the range RBLACK, RWHITE prior to applying CNF, using a mapping outside the scope of this spec
24、ification. 5 The Mfullnarrowand Mfullpermittedmappings are not commutative. If an interface or format uses both protected values and narrow-range image, then the Mfullnarrowmapping is applied first since the Mfullpermittedmapping applies only to interfaces and formats with white and black reference
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