1、 INTERNATIONAL STANDARD ISO/IEC 14496-28:2012TECHNICAL CORRIGENDUM 2 Published 2014-07-01 INTERNATIONAL ORGANIZATION FOR STANDARDIZATION ORGANISATION INTERNATIONALE DE NORMALISATIONINTERNATIONAL ELECTROTECHNICAL COMMISSION COMMISSION LECTROTECHNIQUE INTERNATIONALE Information technology Coding of au
2、dio-visual objects Part 28:Composite font representation TECHNICAL CORRIGENDUM 2:Changes and clarifications of CFR element descriptions Technologies de linformation Codage des objets audiovisuels Partie 28:Reprsentation de la police de caractres composite RECTIFICATIF TECHNIQUE 2:Modifications et pr
3、cisions de descriptions dlments CFR Technical Corrigendum 2 to ISO/IEC 14496-28:2012 was prepared by Joint Technical Committee ISO/IEC JTC 1,Information technology,Subcommittee SC 29,Coding of audio,picture,multimedia and hypermedia information.This corrigendum aims to clarify the meaning and use of
4、 certain Composite Font elements and explain their relationships within the components of the document.In clause 2 Normative references add the new normative reference to the ISO/IEC 14496-22 Open Font Format In subclause 5.1 High-level overview replace the text description with the following:A CFR
5、resource consists of a single PosingFont element,and its Components element specifies an arbitrary number of ComponentDef or LanguagePreferredList elements.It may contain a number of optional elements(such as Name and FontMetrics elements)which provide additional information about the CFR resource a
6、nd its metrics.Whenever an optional element is missing from the CFR,or if there are optional ICS 35.040 Ref.No.ISO/IEC 14496-28:2012/Cor.2:2014(E)ISO/IEC 2014 All rights reserved Published in Switzerland ISO/IEC 14496-28:2012/Cor.2:2014(E)2 ISO/IEC 2014 All rights reserved attributes that are missin
7、g from any of the elements the corresponding information expected to be provided by the missing optional elements and attributes shall be inherited from the first component font specified by either ComponentDef or LanguagePreferredList element.Please note that the choice of the first component font
8、specified by a LanguagePreferredList element may be dependent on users language preferences and,therefore,font metrics and other values inherited from the first component font may also change depending on user language preferences.A CFR resource can be instantiated as a standalone file or resource,a
9、nd it can be referenced by another CFR resource.Examples of Composite Font Representation are presented in Annex B.In subclause 5.3 The Name element replace the first paragraph of the element description with the following:Optional.Each instance of the Name element specifies an attribute that is equ
10、ivalent to a specific name table string of an sfnt resource.The original set of name table entries shall be inherited from the first component font;however,whenever an attribute is present,it will effectively override a particular name table entry with the string defined by the particular instance o
11、f the element.In subclause 5.4 The FontMetrics element replace the first paragraph of the element description with the following:Optional.The FontMetrics element specifies various line-layout attributes that apply globally to the CFR resource.All attributes of the element are optional,if the element
12、 or any of its attributes are not present in the CFR resource definitions but the missing font metrics data is deemed essential for proper layout the corresponding font metrics entry from the first component font shall be used.Since the choice of the first component font may vary based on the user l
13、anguage preferences,it is important to make sure that either language-specific components have matching font metrics or that the attributes and their values provided by the FontMetrics element define a complete overriding set of parameters to avoid the unwanted layout effects.In subclause 5.4 The Fo
14、ntMetrics element replace the attribute definitions of the element with the following:unitsPerEm=string Optional.A virtual UPM(Units Per Em)of the CFR resource expressed as an integer.Its only purpose is to facilitate the correct interpretation of the additional attributes defined by this element,th
15、e actual UPM values of the component fonts defined by the CFR may differ both between the component fonts and from the CFR FontMetrics value.The values of the additional attributes are based on this UPM value.macStyle=string Optional.The head.macStyle value expressed as a 16-digit bit array,see ISO/
16、IEC 14496-22 for detailed descriptionof the attribute value.ascender=string Optional.When provided,this value of ascender will be used by the host rendering system implementations and will override the default value of each component font it is the CFR authors responsibility to make sure that the value is suitable for all component fonts on various host rendering systems.If the value of ascender is not defined,the host rendering system will use the first,highest priority component font to determ