CodingStandard

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Code,

Code,

Code, Standard, Specification, Norm Criterion的区别五个词皆有"规范"之意,作此意时其区别在于:1.Code多指设计技术规范、民事法典、道德或⾏为准则。

For example例如:code of conduct⾏为准则;规范civil code民事法典design code设计规范;设计准则(同design criterion)code of ethics道德规范(尤指职业的);道德准则penal code刑法法典dress code着装要求military code军事法Article 159 of the state's penal code该国刑法第159条。

2.Standard指公认的、尤指可被接受的社会各个⽅⾯⼀般的标准、⽔准、度量衡标准、衡量品质、才度、价值、道德、规则、原则等的标准。

For example例如:discharge standard排放标准double standard双重标准standard solution标准溶液accounting standard会计准则gold standard⾦本位,⾦本位制standard parts标准零件technical standard技术标准standard method标准⽅法;标准措施relative standard相对标准;相关标准quality standard质量标准national standard国家标准living standard⽣活⽔平,⽣活标准international standard国际标准standard of living⽣活⽔平;⽣活标准standard deviation标准偏差up to standard达到标准;合乎标准industry standard产业标准internal standard[物化]内标准;内部标准standard sample标准样品3.Specification专指技术⽅⾯的规范、规格、说明书、质量标准,不⽤于⼈⽂⽅⾯。

第三课PSR-4加载规范

第三课PSR-4加载规范

第三课PSR-4加载规范3.1 什么是PSR PSR 是 PHP Standard Recommendations 的简写,由 PHP FIG (框架可互⽤性⼩组)组织制定的 PHP 规范,是 PHP 开发的实践标准。

3.2 为什么需要 项⽬的⽬的在于:通过框架作者或者框架的代表之间讨论,以最低程度的限制,制定⼀个协作标准,各个框架遵循统⼀的编码规范,避免各家⾃⾏发展的风格阻碍了 PHP 的发展,解决这个程序设计师由来已久的困扰。

3.3 PSR包含哪些规范 PSR-0 (Autoloading Standard) ⾃动加载标准 PSR-1 (Basic Coding Standard) 基础编码标准 PSR-2 (Coding Style Guide) 编码风格向导 PSR-3 (Logger Interface) ⽇志接⼝ PSR-4 (Improved Autoloading) ⾃动加载的增强版,可以替换掉PSR-0了。

https:///thinkphp/php-fig-psr/3144 代码规范 这⾥我们着重介绍psr4的⾃动加载规范3.4 psr4加载规范 PSR-4 是关于由⽂件路径⾃动载⼊对应类的相关规范,在不要求改变代码的实现⽅式,只建议如何使⽤⽂件系统⽬录结构和 PHP 命名组织代码。

框架当中的加载的,⼤部分都是遵循此规范 实现psr4规范加载的例⼦:3.5 psr4加载规范详细说明 此处的“类”泛指所有的class类、接⼝、traits可复⽤代码块以及其它类似结构。

⼀个完整的类名需具有以下结构: \<命名空间>(\<⼦命名空间>)*\<类名> 完整的类名必须要有⼀个顶级命名空间,被称为 "vendor namespace"; 完整的类名可以有⼀个或多个⼦命名空间; 完整的类名必须有⼀个最终的类名; 完整的类名中任意⼀部分中的下滑线都是没有特殊含义的; 完整的类名可以由任意⼤⼩写字母组成; 所有类名都必须是⼤⼩写敏感的。

JSF++_AV_Coding_Standard_NL

JSF++_AV_Coding_Standard_NL

C++ in safety-critical applications: The JSF++ coding standardBjarne Stroustrup, Texas A&M University Kevin Carroll, Lockheed-Martin AeroCopyright 2006 by Lockheed Martin Corporation.Overview•Why C++?•Design philosophy of JSF++•Examples of rules•SummaryLanguage Selection on JSF•Primary language selection criteria:–Object-oriented design methodology employed.–Did not want to translate OO design into language that does not support OO capabilities.–Tool availability and support on latest hardwareplatforms.–Attract bright, young, ambitious engineers.•Constraint–Usable for avionics software•Safety•Hard real time•Performance (time and space)Language Selection: C++ or Ada95?•Historical perspective:–Language choice made during the late 1990’s in the midst of the “dot com”boom.–Prospective engineers expressed very little interest in Ada.•Ada tool chains were in decline–C++ was attractive to prospective engineers.•C++ tools were improving•C++ satisfied language selection criteria as well as staffing concernsUse of C++ on JSF Program•LM decided to use C++•UK skeptical of LM’s choice to use C++–Commissioned QinetiQ to perform a comprehensivesafety review of C++.•325 “issues”raised•QinetiQ unaware of the JSF C++ Philosophy addressing“C++ issues”–Formed technical committee (LM, JPO, UK)•325 issues => 8 new rules and 9 rule modifications •Achieved full US JPO and UK JCA agreement that C++ can be used in safety-critical software.Coding Standard Philosophy•Problem–General purpose languages are “General Purpose”•Conventional solution–Subset language•Eliminate “unnecessary”features•Eliminate “dangerous”features•Example–MISRA C–Well-known subset of C developed for safety-related software in the motor industryProblems with Language Subsets C Language Application C Subset Application C omp l e xi t yLanguage ToolsArea =Domain ComplexityProblems with Language Subsets•Subsetting alone fails to resolve some classes of problems –Complexity is pushed out of the language and into the application code•The semantics of language features are far betterspecified than the typical application code–Errors are simply disguised•(i.e. the problem is moved, not solved)–Productivity is lowered•Programmers must write significantly more lines of code –Maintenance is made more difficult•More code•Worse localization of design decisions•Intent of code less obviousJSF Philosophy (JSF++)•Provide “safer”alternatives to known “unsafe”facilities –Cannot be accomplished in C–Cannot be accomplished via subsetting alone•Craft rule-set to specifically address undefined behavior –Restrict programmers to a better specified, more analyzable, and easier to read (and write) subset of C++–Eliminates large groups of problems by attacking their rootcauses (e.g. passing arrays between functions as pointers)•Ban features with behaviors that are not 100% predictable (from a performance perspective)–Free store allocation (operators new and delete)–Exception handling (operator throw)“Safer”Alternatives to “Unsafe”Facilities•Extension of C++’s philosophy with respect to C•Examples–passing arrays as pointers–use of macros–Use of (C-style) casts•Many well-known dangerous aspects of C were simply “designed out”of C++.–Many MISRA rules are simply unneeded in C++:•20, 25, 26, 71, 72, 75, 77, 78, 80, 84, 105, and 108•C++ provides safer alternatives to many dangerous C constructs –E.g. polymorphism rather than switch statements •Conclusion: C++ can provide a “safer”subset of a superset.JSF++•MISRA is a subset of C• C Allows “unsafe”code that C++rejects•JSF++ is a subset of MISRA (withrespect to C)•JSF++ is a subset of ISO C++•C++ provides facilities that allowthe banning of, or isolation of,dangerous C/C++ features–Libraries, primarily relying onsimple templates, are used toprovide cleaner, “safer”alternatives to known problemareas of C and C++JSF++C++C Simple Libraries “Safer”AlternativesExamples:“Safer”Subset of a Superset•Note: C++ facilities such as templates and virtualfunctions can be used to eliminate most casts (explicit type conversions)–JSF++ strongly encourages elimination of casts•Constants•Inline functions•C++-style casts•Array class•Allocators (static)•Variable macros •Function macros •C-Style casts •Arrays •Dynamic memoryFeedback•We expect to refine JSF++ based on feedback –Lockheed_martin developers–The embedded systems community–The C++ community–Tool builders•Please comment!JSF++ overview•231 rules•11 pages of “front matter”–table of contents, terminology, references, etc.•58 pages of rules•76 page “Appendix A”–with more extensive rationale and examplesRules•Each rule contains either a “should”, “will”or a “shall”in bold letters indicating its type.–Should rules are advisory rules. They strongly suggest therecommended way of doing things.–Will rules are intended to be mandatory requirements. It isexpected that they will be followed, but they do not requireverification. They are limited to non-safety-critical requirements that cannot be easily verified (e.g., naming conventions).–Shall rules are mandatory requirements. They must be followedand they require verification (either automatic or manual).•Breaking a Should rule requires one level of management approval •Breaking a Will or Shall rule requires two levels of management approval (and documentation in code for Shall rules)Example (“no macros”)AV Rule 29The #define pre-processor directive shall not be used to create inline macros. Inline functions shall be used instead.Rationale: Inline functions do not require text substitutions and behave well when called with arguments (e.g. typechecking is performed). See AV Rule 29 in Appendix A foran example.See section 4.13.6 for rules pertaining to inline functions.Further rationale for AV 29Inline functions do not require text substitutions and are well-behaved when called with arguments (e.g. type-checking is performed).Example: Compute the maximum of two integers.#define max (a,b) ((a > b) ? a : b)// Wrong: macroinline int32 maxf(int32 a, int32 b)// Correct: inline function{return (a > b) ? a : b;}y = max (++p,q);// Wrong: ++p evaluated twicey=maxf(++p,q)// Correct: ++p evaluated once and type// checking performed. (q is const)Example (“avoid stupid names”)AV Rule 48Identifiers will not differ by:•Only a mixture of case•The presence/absence of the underscore character•The interchange of the letter ‘O’, with the number ‘0’or the letter ‘D’•The interchange of the letter ‘I’, with the number ‘1’or the letter ‘l’•The interchange of the letter ‘S’with the number ‘5’•The interchange of the letter ‘Z’with the number 2•The interchange of the letter ‘n’with the letter ‘h’.•Rationale: Readability.Example (“use classes well”)AV Rule 65A structure should be used to model an entity that does not requirean invariant.AV Rule 66A class should be used to model an entity that maintains aninvariant.AV Rule 67Public and protected data should only be used in struct s—not classes.Rationale: A class is able to maintain its invariant by controlling access to its data. However, a class cannot control access to itsmembers if those members are non-private. Hence all data in aclass should be private.Exception: Protected members may be used in a class as long as that class does not participate in a client interface. See AV Rule88.ExampleAV Rule 84Operator overloading will be used sparingly and in aconventional manner.Rationale: Since unconventional or inconsistent uses ofoperator overloading can easily lead to confusion, operatoroverloads should only be used to enhance clarity and should follow the natural meanings and conventions of thelanguage. For instance, a C++ operator "+=" shall have thesame meaning as "+" and "=".ExampleArray<int,4> a(0);// array of 4 ints initializer to 0a[2] = 7;// conventional use of subscripting: [ ]Array<int,4> b(0);b = a;// conventional use of assignment: =*b = 1;// unconventional use of *: bannedExample (“avoid arrays”)AV Rule 97Arrays shall not be used in interfaces. Instead, the Array class should be used.Rationale: Arrays degenerate to pointers when passed as parameters. This “array decay”problem has long beenknown to be a source of errors.Note: See Array.doc for guidance concerning the proper use of the Array class, including its interaction with memorymanagement and error handling facilities.void f(Point_3d* p, uint32 n){for (uint32 i=0 ; i<n ; ++i){// process elements}}Example (“avoid arrays”)•Array code vs{{// process elements }}•Declaration and InvocationPoint_3d a1[size];…f(a1,size);Fixed_array<Point_3d,size> a1(Point_3d());…f(a1);Example (“avoid arrays”)•Declaration and Invocation–(size unknown until run-time)Point_3d* a2 = new Point_3d[size];…f(a2,size);Dynamic_array<Point_3d> a2(alloc,size);…f(a2);Example (“templates should be simple”)AV Rule 101Templates shall be reviewed as follows:1.with respect to the template in isolation consideringassumptions or requirements placed on its arguments.2.with respect to all functions instantiated by actualarguments.Note: The compiler should be configured to generate the list of actual template instantiations. See AV Rule 101 inAppendix A for an example.Rationale: Since many instantiations of a template can be generated, any review should consider all actualinstantiations as well as any assumptions or requirementsplaced on arguments of instantiations.Example (“templates should be simple”)//definition:Template<typename T, int dims> class Matrix { /* …*/ };// dims must be a positive integer < 7// T must have ordinary copy semantics// T must provide the usual arithmetic operations (+ -* %)// T most provide the usual comparisons (< <= > >=)//uses:Matrix<int,2> a(100,200);Matrix<complex,3> b(100,200,300);// error: complex has no <Matrix<double,-2> b(100);// error: negative #dimensions •C++98 catches most violations at compile time•C++0x can express and enforce such requirements (“concepts”)Example (“always initialize”)AV Rule 142 (MISRA Rule 30, Revised)All variables shall be initialized before use. (See also AV Rule 136, AV Rule 71, and AV Rule 73, and AV Rule 143concerning declaration scope, object construction, defaultconstructors, and the point of variable introductionrespectively.)Rationale: Prevent the use of variables before they have been properly initialized. See AV Rule 142 in Appendix A foradditional information.Exception: Exceptions are allowed where a name must be introduced before it can be initialized (e.g. value receivedvia an input stream).Example (“always initialize”)int a;// uninitialized: banned// …int b = a;// this is why: likely use before set bug//…a = 7;// “initialize”aconst int max_buf= 256;//…Buffer<char,max_buf> buf;//uninitializedbuf.fill(in2);//fill buf from input source in2Coding Standard Enforcement•Automated–Where possible tools will be used to automate codingstandard enforcement.–Quick, objective, and accurate.–Presently working with tool vendors to automate enforcement of rules.•Manual–For those rules that cannot be automated, checklists areprovided for code inspections.Enforcement and understanding•Developers don’t like to follow rules they don’t understand •Developers find it hard to follow rules the don’t understand –developers should obey the spirit of the rules, not just the words–They can do that only if they understand the generalphilosophy and the rationale for individual rules•Where possible rules are prescriptive (“do this”) rather than prohibitive (“don’t do that”)•Every rule has a rationale–Some rationales are extensive•Many rules have examplesSummary•Provide “safer”alternatives to known “unsafe”facilities –Note: cannot be accomplished via subsetting alone–Simple template-based libraries created to provide cleaner,“safer”alternatives to known problem areas of C and C++•Rule-set crafted to specifically address undefined behavior –Restricts programmers to a better specified, more analyzable, and easier to read (and write) subset of C++–Eliminates large groups of problems by attacking their rootcausesSummary•Banned features with behaviors that are not 100% predictable –Free store allocation–Exception handling•Automated enforcement mechanisms used whenever possible•Achieved full US JPO and UK JCA agreementBest Practices•Coding Standard includes guidance on topics including –Arrays and pointers–Constructors/destructors–Object initialization–Inheritance hierarchies–Templates–C++-style casts–Namespaces–Statement complexityImplementation-Defined Aspects of C++•Strategic approach for managing implementation-defined, undefined, and unspecified aspects of C++. (attack the root causes, not the symptoms)•Rules that–prohibit dependence on evaluation order and side-effects.–manage memory layout issues (unions, bit-fields, casts, etc.)–address overflow issues–minimize the use of casts–limit the use of pointers and arrays–prohibit mixed-mode arithmetic and comparisonsContributors•The design of JSF++ involved many people –Internal and external reviews•Key contributors–Bjarne Stroustrup–Kevin Carroll–Mike Bossert (JPO)–John Colotta–Paul Caseley and Mike Hill (UK)–Randy Ethridge–Greg Hickman–Michael Gibbs–Mike Cottrill–Tommy Gitchell–John Robb–Ian HennellAdditional Information1.JOINT STRIKE FIGHTER AIR VEHICLE C++ CODING STANDARDS FORTHE SYSTEM DEVELOPMENT AND DEMONSTRATION PROGRAM.Document Number 2RDU00001 Rev C. December 2005. “JSF++”/~bs/JSF-AV-rules.pdf2.ISO/IEC 14882:2003(E), Programming Languages –C++.American NationalStandards Institute, New York, New York 10036, 2003.3.Bjarne Stroustrup: Abstraction and the C++ machine model. Proc. ICESS'04.December 2004. Also in Springer LNCS 3605. Enbedded software andsystems. 2005. Bjarne Stroustrup. The C++ Programming Language, 3rdEdition. Addison-Wesley, 2000.4.Lois Goldthwaite (editor): Technical Report on C++ Performance. WG21N1487=03-0070. 2003-08-11.5.Motor Industry Software Reliability Association.Guidelines for the Use of theC Language in Vehicle Based Software, April 1998. MISRA C (“old think”) .6.Scott Meyers. Effective C++: 50 Specific Ways to Improve Your Programsand Design, 2nd Edition.Addison-Wesley, 1998.•More references in [1]。

Java General Coding Standard

Java General Coding Standard

Java Coding StandardVanceInfo Creative Software Technology LTDTABLE OF CONTENTS1.INTRODUCTION _________________________________________________________ 21.1Purpose (2)1.2Scope (2)1.3A pplication (2)2.FILE NAMES ____________________________________________________________ 22.1File Suffixes (2)2.2Common File Names (3)3.FILE ORGANIZA TION _____________________________________________________ 33.1Java Source Files (3)4.INDENTA TION ___________________________________________________________ 34.1Line Length (3)4.2Wrapping Lines (4)MENTS ____________________________________________________________ 46.DECLARA TIONS _________________________________________________________ 56.1Number Per Line (5)6.2Initialization (5)6.3Placement (6)7.STA TEMENTS ___________________________________________________________ 67.1Simple Statements (6)7.2Compound Statements (7)7.3Return Statements (7)8.WHITE SPACE ___________________________________________________________ 78.1Blank Lines (7)8.2Blank Spaces (8)9.NAMING CONVENTIONS __________________________________________________ 810.PROGRAMMING PRACTICES_______________________________________________ 810.1Programming Practices (8)1.INTRODUCTION1.1PurposeThis document describes the standards to follow while coding in V anceInfo1.2ScopeThis document is intended to be used by all V anceInfo Software Engineers developing or maintaining code. On projects where coding standards are specified by customer, follow other standards based on the agreement between customer and V anceInfo.1.3 ApplicationTo ensure readability, maintainability and portability, it is necessary to maintain a consistent style throughout all the software produced by V anceInfo. The internal documentation of the code consists of four parts: file-level documentation,function-level documentation, comments contained within the body of the code and naming conventions.Where changes/enhancements are being made to existing files,then the following should be observed:∙If an existing file does not contain a header, a header must be added. History lines for all new changes must be added.∙When an existing function is being modified, the coding style of the existing function should be maintained. Nevertheless, the following requirements are mandatory:1)If a modified function does not have a header, a standard function header must be added.2)If there is a header without history, a history section must be added.3)All new history lines must conform to the standard in this document.2.FILE NAMESThis section lists the common file name and suffix.2.1File SuffixesJava programs use the following file suffixes:2.2Common File NamesCommonly used file names include:3.FILE ORGANIZATIONA file separate from the line formed by the air passages, and identify each paragraph of an optional comment. More than 2,000 lines of program difficult to read, and should be avoided. "Java Source File Example" provides an example of a rational layout of the Java program.3.1Java Source FilesEach Java source file contains a single public class or interface. If the private classes and interfaces associated with a public class, they can be placed in the same category and source of public documents.Public class must be in this file the first class or interface.Java source files also follow the following rules:- Beginning of Notes (see "Note beginning")- package and the introduction of statements (see "packet and the introduction of statements")-class and interface declarations (see "Class and interface declarations")4. INDENTATION4 spaces are often indented as a unit. Details of the precise interpretation of indentation does not specify (space vs. Tab). A tab is equal to 8 spaces (not 4).4.1Line LengthTo avoid a line is longer than 80 characters, because many terminals and tools are not well processing. Note: for example the document should use a shorter line length-generally no more than 70 characters.4.2Wrapping LinesWhen an expression can not fit on one line, you can disconnect the basis of the following general rules: - A comma disconnect - disconnect in front of an operator - would prefer a higher level (higher-level) of the disconnect, rather than lower level (lower-level) of the disconnect - and the new line should be line level of expression at the beginning of the same alignment - if the above rules lead to confusion in your code or make your code piled crowded on the right, then replaced by indented 8 spaces. The following are some examples of disconnect method call:someMethod(longExpression1, longExpression2, longExpression3,longExpression4, longExpression5);var = someMethod1(longExpression1,someMethod2(longExpression2,longExpression3));Here are two examples of breaking an arithmetic expression. Former is better, because the office is located off the outside bracket expressions, this is a higher level of disconnect.longName1 = longName2 * (longName3 + longName4 - longName5)+ 4 * longname6; //PREFFERlongName1 = longName2 * (longName3 + longName4- longName5) + 4 * longname6; //A VOIDThe following are two examples of indenting method declarations. The former is the conventional case. The use of conventional indentation which way will make the second line and third line of a very right-hand shift, so replace 8 spaces indent.//CONVENTIONAL INDENTA TIONsomeMethod(int anArg, Object anotherArg, String yetAnotherArg,Object andStillAnother) {...}//INDENT 8 SPACES TO A VOID VERY DEEP INDENTSprivate static synchronized horkingLongMethodName(int anArg,Object anotherArg, String yetAnotherArg,Object andStillAnother) {...}MENTSThere are two Java programs Note: Implementation Notes (implementation comments) and document annotation (document comments). Implementation comments are those seen in C + +, using /*...*/ and / / defined in the Notes. Documentation comments (known as "doc comments") is a unique Java by /**...*/ defined. Javadoc tool documentation comments can be converted into HTML files.Implementation Notes for the Notes code or implementation details. Comments from the document of freedom (implementation-free) description of the code of the standard point of view. It can be that source developers do not read.Notes should be used to give overviews of code and provides the code itself does not provide additionalinformation. Notes should only contain procedures for reading and understanding information. For example, the corresponding packet to be created or in which directory information and the like should not be included in a comment.In the note, the important design decisions are not obvious places or explanation is possible, but it should avoid providing the code has been clearly expressed in the repetition of information. Extra notes easily outdated. Should normally be possible to avoid that the code update obsolete comment.Note: The frequency of comments sometimes reflects poor quality of code. When you feel compelled to add a comment, consider rewriting the code to make it more clear.Comments should be written with an asterisk or other character drawn big box. Notes should not be included, such as tabs, and back to back special characters like Fu.6.DECLARATIONS6.1Number Per LineSpacing Recommended line of a statement, because it encourages commenting. That is,int level; / / indentation levelint size; / / size of tableBetter than,int level, size;Do not declare variables of different types on the same line, for example:int foo, fooarray[]; //WRONG!Note: the above example, the type and put a space between the identifier, another alternative is to be allowed to use the tabs:int level; / / indentation levelint size; / / size of tableObject currentEntry; / / currently selected table entry6.2InitializationIn a statement, as far as possible, while local variables initialized. The only reason not to do so is the initial value of the variable depends on the occurrence of some previous calculation.6.3PlacementOnly the beginning of a statement block variable. (A block is any to be included in braces "(" and ")" middle of the code.) Do not use the variable when the first declaration. This will focus attention not confuse programmers, and it will prevent code portability within the role.void myMethod() {int int1 = 0; / / beginning of method blockif (condition) {int int2 = 0; / / beginning of "if" block...}}The one exception to this rule is for loop index variablefor (int i = 0; i <maxLoops; i + +) {...}Local variable declarations to avoid coverage on a declaration of variables. For example, do not block statement within the same variable name:int count;...myMethod () {if (condition) {int count = 0; / / A VOID!...}...}7.STATEMENTS7.1Simple StatementsEach line up to include a statement, for example:argv + +; / / Correctargc -; / / Correctargv + +; argc -; / / A VOID!7.2Compound StatementsCompound statement is included in the sequence of statements in braces, of the form "(statement)." For example, the following paragraphs.- Was one of the statements include statements should be indented one level than the compound - left brace "(" in the compound statement should be the starting end of the line; right brace ")" should be a separate line and the first trip with the compound statement Qi. - Brace can be used for all statements, including the single statement, as long as such if-else statement is for control structure or part. This makes it easy to add statements without having to worry about forgetting brackets as introduced by bug.7.3Return StatementsA return statement with a return value "()", not use parentheses unless they in some way so that the return value is more apparent. For example:return;return myDisk.size ();return (size? size: defaultSize);8.WHITE SPACE8.1Blank LinesAir logic related code soon separated to improve readability.The following conditions should always use two blank lines:- A source file, the two fragments (section) between the- between class declarations and interface declarationsThe following conditions should always use a blank line:- Two methods- methods and approaches within the local variables between the first statement- an approach both within the between the logical segment to improve the readability8.2Blank SpacesShould use the following spaces:- A keyword followed by parentheses should be separated by a space, for example:while (true) {...}Note: The space should not be placed between the method name and its left parenthesis. This will help to distinguish between keywords and the method call. - Blank comma should be located in the back of the parameter list - all the binary operators, except ".", Should be used with the operation of the number of spaces to separate. Unary operators and operands are not due to the spaces between, for example: No. ("-"), negative increment and decrement ("--")。

The H.264 AVC Advanced Video Coding Standard-Overview and Introduction to the Fidelity Range Extensi

The H.264 AVC Advanced Video Coding Standard-Overview and Introduction to the Fidelity Range Extensi

Presented at the SPIE Conference on Applications of Digital Image Processing XXVII Special Session on Advances in the New Emerging Standard: H.264/AVC, August, 2004The H.264/AVC Advanced Video Coding Standard: Overview and Introduction to the Fidelity Range ExtensionsGary J. Sullivan*, Pankaj Topiwala†, and Ajay Luthra‡*Microsoft Corporation, One Microsoft Way, Redmond, WA 98052 † FastVDO LLC, 7150 Riverwood Dr., Columbia, MD 21046 ‡ Motorola Inc., BCS, 6420 Sequence Dr., San Diego, CA 92121ABSTRACTH.264/MPEG-4 AVC is the latest international video coding standard. It was jointly developed by the Video Coding Experts Group (VCEG) of the ITU-T and the Moving Picture Experts Group (MPEG) of ISO/IEC. It uses state-of-the-art coding tools and provides enhanced coding efficiency for a wide range of applications, including video telephony, video conferencing, TV, storage (DVD and/or hard disk based, especially high-definition DVD), streaming video, digital video authoring, digital cinema, and many others. The work on a new set of extensions to this standard has recently been completed. These extensions, known as the Fidelity Range Extensions (FRExt), provide a number of enhanced capabilities relative to the base specification as approved in the Spring of 2003. In this paper, an overview of this standard is provided, including the highlights of the capabilities of the new FRExt features. Some comparisons with the existing MPEG-2 and MPEG-4 Part 2 standards are also provided. Keywords: Advanced Video Coding (AVC), Digital Video Compression, H.263, H.264, JVT, MPEG, MPEG-2, MPEG-4, MPEG-4 part 10, VCEG.1. INTRODUCTIONSince the early 1990s, when the technology was in its infancy, international video coding standards – chronologically, H.261 [1], MPEG-1 [2], MPEG-2 / H.262 [3], H.263 [4], and MPEG-4 (Part 2) [5] – have been the engines behind the commercial success of digital video compression. They have played pivotal roles in spreading the technology by providing the power of interoperability among products developed by different manufacturers, while at the same time allowing enough flexibility for ingenuity in optimizing and molding the technology to fit a given application and making the cost-performance trade-offs best suited to particular requirements. They have provided much-needed assurance to the content creators that their content will run everywhere and they do not have to create and manage multiple copies of the same content to match the products of different manufacturers. They have allowed the economy of scale to allow steep reduction in cost for the masses to be able to afford the technology. They have nurtured open interactions among experts from different companies to promote innovation and to keep pace with the implementation technology and the needs of the applications. ITU-T H.264 / MPEG-4 (Part 10) Advanced Video Coding (commonly referred as H.264/AVC) [6] is the newest entry in the series of international video coding standards. It is currently the most powerful and state-of-the-art standard, and was developed by a Joint Video Team (JVT) consisting of experts from ITU-T’s Video Coding Experts Group (VCEG) and ISO/IEC’s Moving Picture Experts Group (MPEG). As has been the case with past standards, its design provides the most current balance between the coding efficiency, implementation complexity, and cost – based on state of VLSI design technology (CPU's, DSP's, ASIC's, FPGA's, etc.). In the process, a standard was created that improved coding efficiency by a factor of at least about two (on average) over MPEG-2 – the most widely used video coding standard today – while keeping the cost within an acceptable range. In July, 2004, a new amendment was added to this standard, called the Fidelity Range Extensions (FRExt, Amendment 1), which demonstrates even further coding efficiency against MPEG-2, potentially by as much as 3:1 for some key applications. In this paper, we develop an outline of the first version of the H.264/AVC standard, and provide an introduction to the newly-minted extension, which, for reasons we explain, is already receiving wide attention in the industry.1.1. H.264/AVC History H.264/AVC was developed over a period of about four years. The roots of this standard lie in the ITU-T’s H.26L project initiated by the Video Coding Experts Group (VCEG), which issued a Call for Proposals (CfP) in early 1998 and created a first draft design for its new standard in August of 1999. In 2001, when ISO/IEC’s Moving Pictures Experts Group (MPEG) had finished development of its most recent video coding standard, known as MPEG-4 Part 2, it issued a similar CfP to invite new contributions to further improve the coding efficiency beyond what was achieved on that project. VCEG chose to provide its draft design in response to MPEG's CfP and proposed joining forces to complete the work. Several other proposals were also submitted and were tested by MPEG as well. As a result of those tests, MPEG made the following conclusions that affirmed the design choices made by VCEG for H.26L: ♦ The motion compensated Discrete Cosine Transform (DCT) structure was superior to others, implying there was no need, at least at that stage, to make fundamental structural changes for the next generation of coding standard. ♦ Some video coding tools that had been excluded in the past (for MPEG-2, H.263, or MPEG-4 Part 2) due to their complexity (hence implementation cost) could be re-examined for inclusion in the next standard. The VLSI technology had advanced significantly since the development of those standards and this had significantly reduced the implementation cost of those coding tools. (This was not a "blank check" for compression at all costs, as a number of compromises were still necessary for complexity reasons, but it was a recognition that some of the complexity constraints that governed past work could be re-examined.) ♦ To allow maximum freedom of improving the coding efficiency, the syntax of the new coding standard could not be backward compatible with prior standards. ♦ ITU-T’s H.26L was a top-performing proposal, and most others that showed good performance in MPEG had also been based on H.26L (as it had become well-known as an advance in technology by that time). Therefore, to allow speedy progress, ITU-T and ISO/IEC agreed to join forces together to jointly develop the next generation of video coding standard and use H.26L as the starting point. A Joint Video Team (JVT), consisting of experts from VCEG and MPEG, was formed in December, 2001, with the goal of completing the technical development of the standard by 2003. ITU-T planned to adopt the standard under the name of ITU-T H.264, and ISO/IEC planned to adopt the standard as MPEG-4 Part 10 Advanced Video Coding (AVC), in the MPEG-4 suite of standards formally designated as ISO/IEC 14496. As an unwanted byproduct, this standard gets referred to by at least six different names – H.264, H.26L, ISO/IEC 14496-10, JVT, MPEG-4 AVC and MPEG-4 Part 10. In this paper we refer it as H.264/AVC as a balance between the names used in the two organizations. With the wide breadth of applications considered by the two organizations, the application focus for the work was correspondingly broad – from video conferencing to entertainment (broadcasting over cable, satellite, terrestrial, cable modem, DSL etc.; storage on DVDs and hard disks; video on demand etc.) to streaming video, surveillance and military applications, and digital cinema. Three basic feature sets called profiles were established to address these application domains: the Baseline, Main, and Extended profiles. The Baseline profile was designed to minimize complexity and provide high robustness and flexibility for use over a broad range of network environments and conditions; the Main profile was designed with an emphasis on compression coding efficiency capability; and the Extended profile was designed to combine the robustness of the Baseline profile with a higher degree of coding efficiency and greater network robustness and to add enhanced modes useful for special "trick uses" for such applications as flexible video streaming. 1.2. The FRExt Amendment While having a broad range of applications, the initial H.264/AVC standard (as it was completed in May of 2003), was primarily focused on "entertainment-quality" video, based on 8-bits/sample, and 4:2:0 chroma sampling. Given its time constraints, it did not include support for use in the most demanding professional environments, and the design had not been focused on the highest video resolutions. For applications such as content-contribution, content-distribution, and studio editing and post-processing, it may be necessary to ♦ Use more than 8 bits per sample of source video accuracy ♦ Use higher resolution for color representation than what is typical in consumer applications (i.e., to use 4:2:2 or 4:4:4 sampling as opposed to 4:2:0 chroma sampling format)-2-♦ ♦ ♦ ♦ ♦ ♦Perform source editing functions such as alpha blending (a process for blending of multiple video scenes, best known for use in weather reporting where it is used to super-impose video of a newscaster over video of a map or weather-radar scene) Use very high bit rates Use very high resolution Achieve very high fidelity – even representing some parts of the video losslessly Avoid color-space transformation rounding error Use RGB color representationTo address the needs of these most-demanding applications, a continuation of the joint project was launched to add new extensions to the capabilities of the original standard. This effort took about one year to complete – starting with a first draft in May of 2003, the final design decisions were completed in July of 2004, and the editing period will be completed in August or September of 2004. These extensions, originally known as the "professional" extensions, were eventually renamed as the "fidelity range extensions" (FRExt) to better indicate the spirit of the extensions. In the process of designing the FRExt amendment, the JVT was able to go back and re-examine several prior technical proposals that had not been included in the initial standard due to scheduling constraints, uncertainty about benefits, or the original scope of intended applications. With the additional time afforded by the extension project, it was possible to include some of those features in the new extensions. Specifically, these included: ♦ Supporting an adaptive block-size for the residual spatial frequency transform, ♦ Supporting encoder-specified perceptual-based quantization scaling matrices, and ♦ Supporting efficient lossless representation of specific regions in video content. The FRExt project produced a suite of four new profiles collectively called the High profiles: ♦ The High profile (HP), supporting 8-bit video with 4:2:0 sampling, addressing high-end consumer use and other applications using high-resolution video without a need for extended chroma formats or extended sample accuracy ♦ The High 10 profile (Hi10P), supporting 4:2:0 video with up to 10 bits of representation accuracy per sample ♦ The High 4:2:2 profile (H422P), supporting up to 4:2:2 chroma sampling and up to 10 bits per sample, and ♦ The High 4:4:4 profile (H444P), supporting up to 4:4:4 chroma sampling, up to 12 bits per sample, and additionally supporting efficient lossless region coding and an integer residual color transform for coding RGB video while avoiding color-space transformation error All of these profiles support all features of the prior Main profile, and additionally support an adaptive transform blocksize and perceptual quantization scaling matrices. Initial industry feedback has been dramatic in its rapid embrace of FRExt. The High profile appears certain to be incorporated into several important near-term application specifications, particularly including ♦ The HD-DVD specification of the DVD Forum ♦ The BD-ROM Video specification of the Blu-ray Disc Association, and ♦ The DVB (digital video broadcast) standards for European broadcast television Several other environments may soon embrace it as well (e.g., the Advanced Television Systems Committee (ATSC) in the U.S., and various designs for satellite and cable television). Indeed, it appears that the High profile may rapidly overtake the Main profile in terms of dominant near-term industry implementation interest. This is because the High profile adds more coding efficiency to what was previously defined in the Main profile, without adding a significant amount of implementation complexity.-3-2. CODING TOOLSAt a basic overview level, the coding structure of this standard is similar to that of all prior major digital video standards (H.261, MPEG-1, MPEG-2 / H.262, H.263 or MPEG-4 part 2). The architecture and the core building blocks of the encoder are shown in Fig. 1 and Fig. 2, indicating that it is also based on motion-compensated DCT-like transform coding. Each picture is compressed by partitioning it as one or more slices; each slice consists of macroblocks, which are blocks of 16x16 luma samples with corresponding chroma samples. However, each macroblock is also divided into sub-macroblock partitions for motion-compensated prediction. The prediction partitions can have seven different sizes – 16x16, 16x8, 8x16, 8x8, 8x4, 4x8 and 4x4. In past standards, motion compensation used entire macroblocks or, in the case of newer designs, 16x16 or 8x8 partitions, so the larger variety of partition shapes provides enhanced prediction accuracy. The spatial transform for the residual data is then either 8x8 (a size supported only in FRExt) or 4x4. In past major standards, the transform block size has always been 8x8, so the 4x4 block size provides an enhanced specificity in locating residual difference signals. The block size used for the spatial transform is always either the same or smaller than the block size used for prediction. The hierarchy of a video sequence, from sequence to samples1 is given by: sequence (pictures (slices (macroblocks (macroblock partitions (sub-macroblock partitions (blocks (samples)))))). In addition, there may be additional structures such as packetization schemes, channel codes, etc., which relate to the delivery of the video data, not to mention other data streams such as audio. As the video compression tools primarily work at or below the slice layer, bits associated with the slice layer and below are identified as Video Coding Layer (VCL) and bits associated with higher layers are identified as Network Abstraction Layer (NAL) data. VCL data and the highest levels of NAL data can be sent together as part of one single bitstream or can be sent separately. The NAL is designed to fit a variety of delivery frameworks (e.g., broadcast, wireless, storage media). Herein, we only discuss the VCL, which is the heart of the compression capability. While an encoder block diagram is shown in Fig. 1, the decoder conceptually works in reverse, comprising primarily an entropy decoder and the processing elements of the region shaded in Fig. 1.Input Video+Transform/ Scaling/ Quant.Scaling/ Inv .Quant./ Inv. TransformEntropy Coder+Intra (Spatial) Prediction DeblockingC o m p r e s s e d V i d e o b i t sMotion Comp. Decoded Video Motion Vector Info Motion EstimationFig. 1: High-level encoder architecture1We use the terms sample and pixel interchangeably, although sample may sometimes be more rigorously correct.-4-Prediction Spatial/Temporal2-D TransformQuantizationScanningVLC / Arithmetic Entropy CodeFig. 2: Higher-level encoder block diagramIn the first version of the standard, only the 4:2:0 chroma format (typically derived by performing an RGB-to-YCbCr color-space transformation and subsampling the chroma components by a factor of 2:1 both horizontally and vertically) and only 8 bit sample precision for luma and chroma values was supported. The FRExt amendment extended the standard to 4:2:2 and 4:4:4 chroma formats and higher than 8 bits precision, with optional support of auxiliary pictures for such purposes as alpha blending composition. The basic unit of the encoding or decoding process is the macroblock. In 4:2:0 chroma format, each macroblock consists of a 16x16 region of luma samples and two corresponding 8x8 chroma sample arrays. In a macroblock of 4:2:2 chroma format video, the chroma sample arrays are 8x16 in size; and in a macroblock of 4:4:4 chroma format video, they are 16x16 in size. Slices in a picture are compressed by using the following coding tools: ♦ "Intra" spatial (block based) prediction o Full-macroblock luma or chroma prediction – 4 modes (directions) for prediction o 8x8 (FRExt-only) or 4x4 luma prediction – 9 modes (directions) for prediction ♦ "Inter" temporal prediction – block based motion estimation and compensation o Multiple reference pictures o Reference B pictures o Arbitrary referencing order o Variable block sizes for motion compensation Seven block sizes: 16x16, 16x8, 8x16, 8x8, 8x4, 4x8 and 4x4 o 1/4-sample luma interpolation (1/4 or 1/8th-sample chroma interpolation) o Weighted prediction o Frame or Field based motion estimation for interlaced scanned video ♦ Interlaced coding features o Frame-field adaptation Picture Adaptive Frame Field (PicAFF) MacroBlock Adaptive Frame Field (MBAFF) o Field scan ♦ Lossless representation capability o Intra PCM raw sample-value macroblocks o Entropy-coded transform-bypass lossless macroblocks (FRExt-only) ♦ 8x8 (FRExt-only) or 4x4 integer inverse transform (conceptually similar to the well-known DCT) ♦ Residual color transform for efficient RGB coding without conversion loss or bit expansion (FRExt-only) ♦ Scalar quantization ♦ Encoder-specified perceptually weighted quantization scaling matrices (FRExt-only)-5-♦ ♦ ♦ ♦♦♦ ♦ ♦ ♦Logarithmic control of quantization step size as a function of quantization control parameter Deblocking filter (within the motion compensation loop) Coefficient scanning o Zig-Zag (Frame) o Field Lossless Entropy coding o Universal Variable Length Coding (UVLC) using Exp-Golomb codes o Context Adaptive VLC (CAVLC) o Context-based Adaptive Binary Arithmetic Coding (CABAC) Error Resilience Tools o Flexible Macroblock Ordering (FMO) o Arbitrary Slice Order (ASO) o Redundant Slices SP and SI synchronization pictures for streaming and other uses Various color spaces supported (YCbCr of various types, YCgCo, RGB, etc. – especially in FRExt) 4:2:0, 4:2:2 (FRExt-only), and 4:4:4 (FRExt-only) color formats Auxiliary pictures for alpha blending (FRExt-only)Of course, each slice need not use all of the above coding tools. Depending upon on the subset of coding tools used, a slice can be of I (Intra), P (Predicted), B (Bi-predicted), SP (Switching P) or SI (Switching I) type. A picture may contain different slice types, and pictures come in two basic types – reference and non-reference pictures. Reference pictures can be used as references for interframe prediction during the decoding of later pictures (in bitstream order) and non-reference pictures cannot. (It is noteworthy that, unlike in prior standards, pictures that use bi-prediction can be used as references just like pictures coded using I or P slices.) In the next section we describe the coding tools used for these different slice types. This standard is designed to perform well for both progressive-scan and interlaced-scan video. In interlaced-scan video, a frame consists of two fields – each captured at ½ the frame duration apart in time. Because the fields are captured with significant time gap, the spatial correlation among adjacent lines of a frame is reduced in the parts of picture containing moving objects. Therefore, from coding efficiency point of view, a decision needs to be made whether to compress video as one single frame or as two separate fields. H.264/AVC allows that decision to be made either independently for each pair of vertically-adjacent macroblocks or independently for each entire frame. When the decisions are made at the macroblock-pair level, this is called MacroBlock Adaptive Frame-Field (MBAFF) coding and when the decisions are made at the frame level then this is called Picture-Adaptive Frame-Field (PicAFF) coding. Notice that in MBAFF, unlike in the MPEG-2 standard, the frame or field decision is made for the vertical macroblock-pair and not for each individual macroblock. This allows retaining a 16x16 size for each macroblock and the same size for all submacroblock partitions – regardless of whether the macroblock is processed in frame or field mode and regardless of whether the mode switching is at the picture level or the macroblock-pair level. 2.1. I-slice In I-slices (and in intra macroblocks of non-I slices) pixel values are first spatially predicted from their neighboring pixel values. After spatial prediction, the residual information is transformed using a 4x4 transform or an 8x8 transform (FRExt-only) and then quantized. In FRExt, the quantization process supports encoder-specified perceptual-based quantization scaling matrices to optimize the quantization process according to the visibility of the specific frequency associated with each transform coefficient. Quantized coefficients of the transform are scanned in one of the two different ways (zig-zag or field scan) and are compressed by entropy coding using one of two methods – CAVLC or CABAC. In PicAFF operation, each field is compressed in a manner analogous to the processing of an entire frame. In MBAFF operation, if a macroblock pair is in field mode then the field neighbors are used for spatial prediction and if a macroblock pair is in frame mode, frame neighbors are used for prediction. The frame or field decision is made before applying the rest of the coding tools described below. Temporal prediction is not used in intra macroblocks, but it is for P and B macroblock types, which is the main difference between these fundamental macroblock types. We therefore review the structure of the codec for the I-slice first, and then review the key differences for P and B-slices later.-6-2.1.1. Intra Spatial Prediction To exploit spatial correlation among pixels, three basic types of intra spatial prediction are defined: ♦ Full-macroblock prediction for 16x16 luma or the corresponding chroma block size, or ♦ 8x8 luma prediction (FRExt-only), or ♦ 4x4 luma prediction. For full-macroblock prediction, the pixel values of an entire macroblock of luma or chroma data are predicted from the edge pixels of neighboring previously-decoded macroblocks (similar to what is shown in Fig. 3, but for a larger region than the 4x4 region shown in the figure). Full-macroblock prediction can be performed in one of four different ways that can be selected by the encoder for the prediction of each particular macroblock: (i) vertical, (ii) horizontal, (iii) DC and (iv) planar. For the vertical and horizontal prediction types, the pixel values of a macroblock are predicted from the pixels just above or to the left of the macroblock, respectively (like directions 0 and 1 in Fig. 3). In DC prediction (prediction type number 2, not shown in Fig. 3), the luma values of the neighboring pixels are averaged and that average value is used as predictor. In planar prediction (not shown in Fig. 3), a three-parameter curve-fitting equation is used to form a prediction block having a brightness, slope in the horizontal direction, and slope in the vertical direction that approximately matches the neighboring pixels. Full-macroblock intra prediction is used for luma in a macroblock type called the intra 16x16 macroblock type. Chroma intra prediction always operates using full-macroblock prediction. Because of differences in the size of the chroma arrays for the macroblock in different chroma formats (i.e., 8x8 chroma in 4:2:0 macroblocks, 8x16 chroma in 4:2:2 macroblocks, and 16x16 chroma in 4:4:4 macroblocks), chroma prediction is defined for three possible block sizes. The prediction type for the chroma is selected independently of the prediction type for the luma. 4x4 intra prediction for luma can be alternatively selected (on a macroblock-by-macroblock basis) by the encoder. In 4x4 spatial prediction mode, the values of each 4x4 block of luma samples are predicted from the neighboring pixels above or left of a 4x4 block, and nine different directional ways of performing the prediction can be selected by the encoder (on a 4x4 block basis) as illustrated in Fig. 3 (and including a DC prediction type numbered as mode 2, which is not shown in the figure). Each prediction direction corresponds to a particular set of spatially-dependent linear combinations of previously decoded samples for use as the prediction of each input sample. In FRExt profiles, 8x8 luma intra prediction can also be selected. 8x8 intra prediction uses basically the same concepts as 4x4 prediction, but with a prediction block size that is 8x8 rather than 4x4 and with low-pass filtering of the predictor to improve prediction performance.M A B C D E F G H8 1 6 3 7 0 5 4I J K La e i mb f j nc g k od h l pFig. 3: Spatial prediction of a 4x4 block.-7-2.1.2. Transform and Quantization After spatial prediction, a transform is applied to decorrelate the data spatially. There are several unique features about the transform selected for this coding standard. Some of these features are listed below. ♦ It is the first video standard fundamentally based on an integer inverse transform design for its main spatial transforms, rather than using idealized trigonometric functions to define the inverse transform equations and allowing implementation-specific approximations within some specified tolerances.2 The forward transform that will typically be used for encoding is also an integer transform. A significant advantage of the use of an integer is that, with an exact integer inverse transform, there is now no possibility of a mismatch between then encoder and decoder, unlike for MPEG-2 and ordinary MPEG-4 part 2. ♦ In fact, the transform is specified so that for 8-bit input video data, it can be easily implemented using only 16-bit arithmetic, rather than the 32-bit or greater precision needed for the transform specified in prior standards. ♦ The transform (at least for the 4x4 block size supported without FRExt) is designed to be so simple that it can be implemented using just a few additions, subtractions, and bit shifts. ♦ A 4x4 transform size is supported, rather than just 8x8. Inconsistencies between neighboring blocks will thus occur at a smaller granularity, and thus tend to be less noticeable. Isolated features can be represented with greater accuracy in spatial location (reducing a phenomenon known as "ringing"). For certain hardware implementations, the small block size may also be particularly convenient. Thus, while the macroblock size remains at 16x16, these are divided up into 4x4 or 8x8 blocks, and a 4x4 or 8x8 block transformation matrix T4x4 or T8x8 is applied to every block of pixels, as given by:T4 x 41 ⎡ 1 ⎢ 2 1 =⎢ ⎢ 1 −1 ⎢ ⎣ 1 −21⎤ − 1 − 2⎥ ⎥, T 8 x8 1⎥ −1 ⎥ 2 − 1⎦ 18 8 8 ⎡ 8 ⎢ 12 10 6 3 ⎢ ⎢ 8 4 − 4 −8 ⎢ 10 − 3 − 12 − 6 =⎢ ⎢ 8 −8 −8 8 ⎢ 3 10 ⎢ 6 − 12 ⎢ 4 −8 8 −4 ⎢ ⎢ 3 −6 10 − 12 ⎣8 −3 −8 6 8 10 −48 −4 12 −8 −3 88 4 3 −8 12 −8 6− 6 − 1012 − 108⎤ − 12⎥ ⎥ 8⎥ ⎥ − 10⎥ 8⎥ ⎥ − 6⎥ 4⎥ ⎥ − 3⎥ ⎦The 4x4 transform is remarkably simple, and while the 8x8 transform (used in FRExt profiles only) is somewhat more complex, it is still remarkably simple when compared to an ordinary 8x8 IDCT. The transform T is applied to each block within the luma (16x16) and chroma (8x8, or in FRExt, 8x16 or 16x16) samples for a macroblock by segmenting the full sample block size into smaller blocks for transformation as necessary. In addition, when the 16x16 Intra prediction mode is used with the 4x4 transform, the DC coefficients of the sixteen 4x4 luma blocks in the macroblock are further selected and transformed by a secondary Hadamard transform using the H4x4 matrix shown below (note the basic similarity of T4x4 and H4x4). The DC coefficients of the 4x4 blocks of chroma samples in all macroblock types are transformed using a secondary Hadamard transform as well. For 4:2:0 video, this requires a 2x2 chroma DC transformation specified by the Hadamard matrix H2x2 (below); for 4:4:4, the chroma DC uses the same 4x4 Hadamard transformation as used for luma in 16x16 intra mode; and for 4:2:2 video, the chroma DC transformation uses the matrices H2x2 and H4x4 to perform a 2x4 chroma DC secondary transformation.2MPEG-4 part 2 and JPEG2000 had previously included integer wavelet transforms. But JPEG2000 is an image coding standard without support for interframe prediction, and in MPEG-4, the integer transforms are used only rarely for what is called texture coding (somewhat equivalent to the usual I-frame coding, but not found in most implementations of MPEG-4), and the main transform used for nearly all video data was still specified as an ideal 8x8 IDCT with rounding tolerances. The integer transform concept had also been previously applied in H.263 Annex W, but only as an after-thefact patch to a prior specification in terms of the 8x8 floating point IDCT.-8-。

视频监控系统设计方案 外文翻译

视频监控系统设计方案 外文翻译

A TRANSLATINGboth systems to advanced, practical, mature, reliable, but also to open systems, scalability, and take into account reasonable investment, the purpose of the best efficiency. CCTV surveillance equipment on the spot on surveillance, control and management of these facilities in a safe, reliable and efficient operation, and make full use of intelligent management role, to create a safe, healthy, comfortable and to be able to improve the efficiency of the fine work environment , energy conservation, and reduce maintenance personnel. According to the project's environmental needs, and demand for the establishment of joint function of the item CCTV monitoring,1, the system has the following features:CCTV main task is an important part of the building within the developments, such as dynamic flow conditions macroeconomic surveillance, control, the various anomalies in order to conduct real-time evidence, review, to the timely processing of purpose.1) video signal timing, location switch programming.2) view and record images, and a distinction should be characters time (year, month, day) display.3) receive signal superimposed elevator floor.4) synchronized switching: Power, synchronous or synchronous.5) to receive security subsystems signal system, in accordance with the need to achieve joint control or system integration.6) internal and external communications links.7) security surveillance television system and security alarm system linked, should be able to automatically switch, display, record of the image signal alarm location and alarm time.8) Power ControlCamera security control room should be unified with green power by the security control room operators-to cut off. On the security control room far away from the camera is powered reunification can be difficult to resolve the nearest, if the system is a synchronous mode of power, and security must be the same for the control room of a reliable power supply.2, the system has the following features:H.264 compression technologyH.264 video coding standard is designed for the high-quality image compression campaign designed by the low bit-rate image compression standard. H.264 video coding used in the movement of the common coding method, coding and decoding process is divided into two parts interframe coding. Egypt Intra Improved DCT transformation and quantified in the inter-frame of a 1 / 2 pixel motion vector forecast compensation technology, motion compensation more precise, quantifiable improvements apply variable length coding table (VLC) and quantitative data for entropy coding, coding final coefficient.H.264 standard higher compression ratio, the entire CIF format-mode single occupied bandwidth in the hundreds around the general, occupied bandwidth depending on the specific exercise how many different picture. Deficiency is relatively poor quality of some, occupied bandwidth screen with movement and the complexity of substantial change.In short, this is a closed-circuit television monitor so that the item highly automated, highly efficient elegant comfortable, convenient and speedy, high-security environment of space. System mainly consists of three parts: front-end monitoring; Monitoring Centre (control center); workstation (client).The installation of video surveillance point: Color night vision cameras and color of high illumination cameras and other equipment installed in the designated location, providing 12 VDC power supply and video interface.Monitoring CentreAccording to specific requirements of schools, teaching areas (of nine school buildings), by Information Centre and the Centre set up a control extensions, the clinic, teachers dormitory (a total of two dormitory) and garage, the living quarters of students (total 12 dormitory) to install a control extensions, canteens, supermarkets, sports centre, student activity centre, Training Center, the south gate, Simon and the North have set up a control extensions, in the host control centre set up to monitor the entire campus that in turn control the first time police information and criminals every move in the room were Baoweichu president and the establishment of a control center.DVR control center through the control system can be arbitrary view the full image (to authority), and a monitoring point for the implementation of cloth Chefang, video playback operations (to access).Control centers are located in the President's Office, the leading sub-control center can ca arbitrary control of pan, tilt and zoom images and action. As a management and understanding of the situation both inside and outside the hospital auxiliary means. House leadership not to the office in order to understand the key parts of the hospital situation.Through transmission from the remote video signals through digital hard disk video recorders to provide resource sharing connections. All the video and alarm records can be shared through the network (to access).Set up seven distribution of authority, the operators were in a different authority to operate. System of great security, all users must provide to the user name and password to detect competence, not manipulation system.Alarm system with tips and video motion detection capabilities greatly save disk space, a police video documentary video to be stored, the system does not reach to facilitate enquiries for information after the incident, the police want to delete documents must be carried out by the system administrator .Alarm systems also have automated records and functional linkage, the system interface unit with the police, and other police equipment can be connected. Any time a system of regional security alarms were triggered, the system will automatically switch to alarm the camera screen monitor regional, state and automatically transferred to video. If two or more simultaneous alarm information, the system can simultaneously record or order of the corresponding alarm and regional image. Monitoring Centre Digital HD recorders, DVR installation of server-side software, including database system. All front-end server management and monitoring equipment, and maintenance of the client network connections at the same time, monitoring of all network workstations authorized users to manage all office LAN users can log on to a computer server system, depending on image rights surveillance enquiries, such as video playback. To configure and monitor server drives to the video information will be kept a month's time.Server software installation is complete, the system automatically configures the video data storage path, users may need to use the server-side management software to change configuration, the system supports distributed video storage for large-capacity storage may be provided.Monitoring center can be set up in a monitoring station, monitoring workstation as a system administrator user of the system in equipment and user management, including video data maintenance and management. Workstations can be connected with theprojector system can be used to monitor or demonstration.monitoring workstation (client)Network computer users to install DVR client software, landing by the system administrator to provide legal status and server access rights, can become a monitoring station.Client software, including: system configuration tools, control software, and audio and video playback software enquiries.System configuration tool: video can be set to undertake the lens division, video server settings, among others.Monitoring Software: 1-9 frame to provide the real-time monitoring, Haeundae or ball machine control.Enquiries playback software: According to the lens name, date / time, video and other types of enquiries, and intervals for the results. Monitoring centre is just a computer as a server (under video server configuration corresponding amount of demand for hard disk), can be configured as a workstation monitoring systems management and settings to use, when necessary can be configured a projector and workstations connected to peacetime surveillance or system demonstration.Implementation of the systemThe system of cameras and lenses, Haeundae, protective enclosures, monitors, and other traditional products can basically part of the optional, but it should be used cost-effective products.The system used in high-definition color Huamianbangeqi 16 Huamianbangeqi, automatic image switch selectable switching time, a functional image freeze. Video switch matrix by the Chengdu Branch of the MJ516 video switch matrix, and the ways for its 16-way input, the output of five trade unions Road. It is Chinese characters superimposed clock system uptime enquiries, a powerful built-in functions such as Chinese Character Library. It is critical to provide the relevant agreements for secondary development.The software is to use some of the major video capture card provided by the API function and video switching matrix provided by the communication protocol software and services produced receive software, which is one-way video signals and control signals are two-way. Through LAN control commands can be issued.ConclusionThis paper illustrates how the present technological conditions, assembled into one economical and reliable, and compatible with the advanced monitoring system. This system suited to the local area network (10/100 M) on the real-time transmission of digital video images. Multimedia is a simple monitoring system (including video only). Believe that with computer technology, video technology, control technology, communications technology development, network monitoring will also enjoy broad prospects.An analog-to-digital converterAn analog-to-digital converter(ADC) is used to convert a continuously variable signal to a corresponding digital form which can take any one of a fixed number of possible binary values. If the output of the transducer does not vary continuously, no ADC is necessary. In this case the signal conditioning section must convert the incoming signal to a form which can be connected directly to the next part of the interface, the input/output section of the microcomputer itself.The I/O section converts digital “on/off” voltage signals to a formwhich can be presented to the processor via the system buses. Here the state of each input line, whether it is “on” or “off”, is indicated by a corresponding “1” or “0”. In th e analog inputs which have been converted to digital form, the patterns of ones and zeros in the internal representation will form binary numbers corresponding to the quantity being converted.Feedback ControlThe class of control problems to be examined here is one of considerable engineering interest. We shall consider systems with several inputs, some known as controls because they may be manipulated and others called external disturbances, which are quite unpredictable. For example, in an industrial furnace we may consider the fuel flow, the ambient temperature, and the loading of material into the furnace to be inputs. Of these, the fuel flow is accessible and can readily be controlled, while the latter two are usually unpredictable disturbances.In such situations, one aspect of the control problems is to determine how the controls should be manipulated so as to counteract the effects of the external disturbances on the state of the system. One possible approach to the solution of this problem is to use a continuous measurement of the disturbances, and from this and the known system equations to determine what the control inputs should be as functions of time to give appropriate control of the system state.Digital Interface CircuitsThe signals used within microcomputer circuits are almost always too small to be connected directly to the “outside world” and some kind of interface must be used to translate them to a more appropriate form. The design of section of interface circuits is one of the most important tasks facing the engineer wishing to apply microcomputers. We have seen that in microcomputers information is represented as discrete patterns of bits; this digital form is most useful when the microcomputer is to be connected to equipment which can only be switched on or off, where each bit might represent the state of a switch or actuator.Care must be taken when connecting logic circuits to ensure that their logic levels and current ratings are compatible. The output voltages produced by a logic circuit are normally specified in terms of worst case values when sourcing or sinking the maximum rated currents. Thus Voh is the guaranteed minimum “high” voltage when sourcing the maximum rated “high” output current Ioh, while Vol is the guaranteed minimum “low” output voltage when sinking the maximum rated “low” output current Iol. There are corresponding specification for logic inputs which specify the minimum input voltage which will be recognized as a logic “high” state Vih, and the maximum input voltage which will be regarded as a logic “low” state Vil.For input interface, perhaps the main problem facing the designer isthat of electrical noise. Small noises signals may cause the system to malfunction, while larger amounts of noise can permanently damage it. The designer must be aware of these dangers from the outset. There are many methods to protect interface circuits and microcomputer from various kinds of noise. Following are some example:1. Input and output electrical isolation between the microcomputer system and external devices using an opto-isolator or a transformer.2. Removing high frequency noise pulses by a low-pass filter and Schmitt-trigger.3. Protecting against excessive input voltages using a pair of diodes to power supply reversibly biased in normal direction.For output interface, parameters Voh,Vol,Ioh and Iol of a logic device are usually much to low to allow loads to be connected directly, and in practice an external circuit must be connected to amplify the current and voltage to drive a load. Although several types of semiconductor devices are now available for controlling DC and AC powers up to many kilowatts, there are two basic ways in which a switch can be connected to a load to control it.With series connection, the switch allows current to flow through the load when closed, while with shunt connection closing the switch allows current to bypass the load. Both connections are useful in low-power circuits, but only the series connection can be used in high-power circuits because of the power wasted in the series resistor R..AT89C52Compatible with MCS-51™ Products,8K Bytes of In-System Reprogrammable Flash Memory,Endurance: 1,000 Write/Erase Cycles, Fully Static Operation: 0 Hz to 24 MHz,Three-level Program Memory Lock,256 x 8-bit Internal RAM,32 Programmable I/O Lines,Three 16-bitTimer/Counters, Eight Interrupt Sources, Programmable Serial Channel Low-power Idle and Power-down Modes.DescriptionThe AT89C52 provides the following standard features: 8K bytes of Flash, 256 bytes of RAM, 32 I/O lines, three 16-bit timer/counters, a six-vector two-level interrupt architecture, a full-duplex serial port, on-chip oscillator, and clock circuitry. In addition, the AT89C52 is designed with static logic for operation down to zero frequency and supports two software selectable power saving modes. The Idle Mode stops the CPU while allowing the RAM, timer/counters, serial port, and interrupt system to continue functioning. The Power-down mode saves the RAM contents but freezes the oscillator, disabling all other chip functions until the next hardware reset.AT89C52 Timer 2Timer 2 is a 16-bit Timer/Counter that can operate as either a timer or an event counter. The type of operation is selected by bit C/T2 in theSFR T2CON (shown in Table 2). Timer 2 has three operating modes: capture, auto-reload (up or down counting), and baud rate generator. The modes are selected by bits in T2CON, as shown in Table 3. Timer 2 consists of two 8-bit registers, TH2 and TL2. In the Timer function, the TL2 register is incremented every machine cycle. Since a machine cycle consists of 12 oscillator periods, the count rate is 1/12 of the oscillator frequency. In the Counter function, the register is incremented in response to a 1-to-0 transition at its corresponding external input pin, T2. In this function, the external input is sampled during S5P2 of every machine cycle. When the samples show a high in one cycle and a low in the next cycle, the count is incremented. The new count value appears in the register during S3P1 of the cycle following the one in which the transition was detected. Since two machine cycles (24 oscillator periods) are required to recognize a 1-to-0 transition, the maximum count rate is 1/24 of the oscillator frequency. To ensure that a given level is sampled at least once before it changes, the level should be held for at least one full machine cycle.Capture ModeIn the capture mode, two options are selected by bit EXEN2 in T2CON. If EXEN2 = 0, Timer 2 is a 16-bit timer or counter which upon overflow sets bit TF2 in T2CON. This bit can then be used to generate an interrupt. If EXEN2 = 1, Timer 2 performs the same operation, but a 1- to-0 transition at external input T2EX also causes the current value in TH2 and TL2 to be captured into RCAP2H and RCAP2L, respectively. In addition, the transition at T2EX causes bit EXF2 in T2CON to be set. The EXF2 bit, like TF2, can generate an interrupt. The capture mode is illustrated in Figure Auto-reload (Up or Down Counter)Timer 2 can be programmed to count up or down when configured in its 16-bit auto-reload mode. This feature is invoked by the DCEN (Down Counter Enable) bit located in the SFR T2MOD. Upon reset, the DCEN bit is set to 0 so that timer 2 will default to count up. When DCEN is set, Timer 2 can count up or down, depending on the value of the T2EX pin.Baud Rate GeneratorTimer 2 is selected as the baud rate generator by setting TCLK and/or RCLK in T2CON. Note that the baud rates for transmit and receive can be different if Timer 2 is used for the receiver or transmitter and Timer 1 is used for the other function. Setting RCLK and/or TCLK puts Timer 2 into its baud rate generator mode. The baud rate generator mode is similar to the auto-reload mode, in that a rollover in TH2 causes the Timer 2 registers to be reloaded with the 16-bit value in registers RCAP2H and RCAP2L, which are preset by software. The baud rates in Modes 1 and 3 are determined by Timer 2’s overflow rate according to the following equation.The Timer can be configured for either timer or counter operation. In most applications, it is configured for timer operation (CP/T2 = 0). The timer operation is different for Timer 2 when it is used as a baud rate generator. Normally, as a timer, it increments every machine cycle (at 1/12 the oscillator frequency). As a baud rate generator, however, it increments every state time (at 1/2 the oscillator frequency). The baud rate formula is given below.where (RCAP2H, RCAP2L) is the content of RCAP2H and RCAP2L taken as a 16-bit unsigned integer. Timer 2 as a baud rate generator is shown in Figure 4. This figure is valid only if RCLK or TCLK = 1 in T2CON. Note that a rollover in TH2 does not set TF2 and will not generate an interrupt. Note too, that if EXEN2 is set, a 1-to-0 transition in T2EX will set EXF2 but will not cause a reload from (RCAP2H, RCAP2L) to (TH2, TL2). Thus when Timer 2 is in use as a baud rate generator, T2EX can be used as an extra external interrupt. Note that when Timer 2 is running (TR2 = 1) as a timer in the baud rate generator mode, TH2 or TL2 should not be read from or written to. Under these conditions, the Timer is incremented every state time, and the results of a read or write may not be accurate. The RCAP2 registers may be read but should not be written to, because a write might overlap a reload and cause write and/or reload errors. The timer should be turned off (clear TR2) before accessing the Timer 2 or RCAP2 registers.中文随着电视技术的发展和闭路电视监控系统要求的提高,闭路电视监控系统迅速成长起来。

联合国制定的计算机内部使用的标准代码

联合国制定的计算机内部使用的标准代码

联合国制定的计算机内部使用的标准代码联合国制定了许多计算机内部使用的标准代码,其中包括以下一些常见的标准代码:1. UN M.49:用于表示国家和地区的标准编码。

该编码由三位数字组成,用于唯一标识世界上每个国家和地区。

例如,中国的UN M.49代码是156,美国的代码是840。

2. ISO 3166:用于表示国家和地区的标准编码。

它由两个字母的ISO 3166-1 alpha-2代码和三个字母的ISO 3166-1 alpha-3代码组成。

这些代码广泛应用于国际标准化领域和计算机系统中,例如在电子邮件地址和网站域名中使用。

3. ISO 4217:用于表示货币的标准编码。

每个国家或地区的货币都被分配了一个唯一的三个字母代码,用于在金融交易和计算机系统中标识和区分不同的货币。

例如,美元的ISO 4217代码是USD,人民币的代码是CNY。

4. UN/LOCODE:用于表示港口和地理位置的标准编码。

该编码由五个字母组成,用于唯一标识世界上的港口、货运码头和其他重要地理位置。

这个编码系统被广泛用于贸易和物流领域。

5. UN/CEFACT推荐标准代码:联合国电子商务和贸易便利化委员会(United Nations Centre for Trade Facilitation and Electronic Business,简称UN/CEFACT)制定了一些推荐的标准代码,用于在电子商务和贸易领域中标识和描述不同的实体、过程和属性。

这些标准代码包括UN/CEFACT推荐的产品分类(UNSPSC)、物料流分类(UN/LOCODE)等。

这些标准代码的统一使用有助于促进国际合作、交流和数据交换,提高计算机系统的互操作性和数据质量。

复杂度可分级的视频编码技术研究的开题报告

复杂度可分级的视频编码技术研究的开题报告

复杂度可分级的视频编码技术研究的开题报告1. 研究背景随着视频数据的广泛应用,视频编码技术的研究也越来越受到关注。

视频编码的目的是将视频信号转化为数字信号,并压缩存储,以便于传输、处理和播放。

目前,视频编码技术已经发展到了第三代标准,即H.264/AVC和HEVC。

然而,现有的视频编码技术仍然存在一些问题。

例如,视频信号的复杂度不同,但现有的编码技术往往采用相同的编码方式,导致编码效率不高。

因此,需要一种能够根据视频信号的复杂度进行分级编码的技术,以提高编码效率。

2. 研究内容和目标本文旨在研究一种基于复杂度可分级的视频编码技术。

具体内容包括以下几个方面:(1) 研究现有的视频编码技术,分析其存在的问题和不足。

(2) 研究视频信号的复杂度度量方法,以便于对视频信号进行分级。

(3) 设计一种基于视频信号复杂度分级的视频编码算法,以提高编码效率。

(4) 实现所设计的视频编码算法,并进行实验评估。

本文的目标是设计一种能够根据视频信号的复杂度进行分级编码的技术,以提高编码效率。

3. 研究方法和步骤(1) 文献调研:对现有的视频编码技术、视频信号复杂度度量方法和分级编码算法进行综述和分析。

(2) 视频信号复杂度度量方法研究:研究视频信号的复杂度度量方法,如空间域、频域、时域等方法,并分析其适用性和优缺点。

(3) 分级编码算法设计:设计一种基于视频信号复杂度分级的视频编码算法,包括分级策略、编码方式等。

(4) 算法实现:利用编程语言实现所设计的视频编码算法。

(5) 实验评估:对所实现的编码算法进行实验评估,并与现有的编码技术进行比较。

4. 预期成果(1) 综述和分析现有的视频编码技术、视频信号复杂度度量方法和分级编码算法,深入了解视频编码技术的最新研究进展。

(2) 设计一种基于视频信号复杂度分级的视频编码算法,提高编码效率。

(3) 实现所设计的视频编码算法,并进行实验评估,验证其有效性和可行性。

(4) 发表相关论文,提高研究水平和学术影响力。

cert-c标准

cert-c标准

CERT C标准,全称为"CERT C Secure Coding Standard",是由美国卡内基梅隆大学软件工程研究所(Software Engineering Institute, SEI)的CERT 协调中心制定的一套C语言编程安全规范。

这套标准旨在帮助开发者识别和避免在C语言编程中常见的安全漏洞和错误。

CERT C标准涵盖了许多方面,包括但不限于:
1. 内存管理:如何正确地使用malloc、calloc、realloc和free等内存管理函数,以避免内存泄漏、悬挂指针和缓冲区溢出等问题。

2. 整数处理:如何正确地进行整数运算和转换,以防止整数溢出和其他与整数相关的安全问题。

3. 指针和数组:如何正确地使用指针和数组,包括边界检查、空指针解引用和野指针的避免。

4. 格式化字符串:如何正确地使用printf、scanf等格式化字符串函数,以防止格式化字符串攻击。

5. 输入/输出操作:如何安全地进行文件、网络和其它I/O操作,包括错误处理和资源管理。

6. 并发和同步:如何正确地处理多线程和多进程环境中的并发和同步问题,如死锁、竞态条件和数据竞争。

7. 其他编程实践:还包括了一些其他的编程最佳实践,如错误处理、类型安全、函数参数和返回值的处理等。

CERT C标准提供了一套详细的规则和指南,可以帮助开发者编写更安全、更可靠的C代码。

遵循这些标准可以显著降低软件中的安全风险,并提高软件的整体质量。

许多组织和项目都推荐或要求开发人员遵循CERT C标准进行编程。

avs编码标准

avs编码标准

AVS(Audio Video coding Standard)即数字音视频编解码技术标准,是中国第二代信源编码标准,主要解决数字音视频海量数据(即初始数据、信源)的编码压缩问题,故也称数字音视频编解码技术。

AVS工作组即数字音视频编解码技术标准工作组(Audio Video coding Standard Workgroup of China),由国家原信息产业部科学技术司于2002年6月批准成立。

自AVS工作组2002年成立以来,至今已制定了两代AVS标准。

其编码效率相比于MPEG-2标准提高2到3倍,相比于H.264标准相当,但是其算法复杂度低于H.264。

AVS视频编码标准采用传统的基于预测变换的编码框架,可以分为预测、变换、熵编码和环路滤波4个主要模块。

在所有宏块都进行帧内预测或帧间预测后,预测残差要进行8*8整数变换(ICT)和量化(Q),然后对量化系数进行zig-zag扫描,得到一维排列的量化系数,最后对量化系数进行熵编码。

预测又分为帧内预测和帧间预测,分别用于消除空域冗余和时域冗余。

总的来说,AVS编码标准是一种高效、安全的音视频编码技术,具有广泛的应用前景。

射频cse标准 -回复

射频cse标准 -回复

射频cse标准-回复什么是射频CSE标准?射频CSE标准(射频Coding and Test Standard)是电子设备制造和射频通信领域中的一个重要标准。

它规定了射频设备的编码和测试要求,旨在确保射频设备在设计、制造和使用过程中的性能和可靠性。

射频设备是指能够发射、接收或处理射频(无线电频率)信号的设备,包括无线通信设备、雷达设备、射频感知设备等。

射频CSE标准的制定有助于确保射频设备在各种环境下的正常工作,提高射频通信的质量和稳定性。

射频CSE标准的制定过程可以分为以下几个步骤:步骤一:需求收集和分析在制定射频CSE标准之前,需要对射频设备的需求进行收集和分析。

这包括与用户、制造商、设计师等相关方沟通,了解射频设备的使用环境、要求和需求,以及可能存在的问题和挑战。

通过对需求的分析,可以明确射频CSE标准的制定目标和范围。

步骤二:制定标准框架在明确了射频CSE标准的目标和范围之后,需要制定其标准框架。

标准框架是标准的基本结构和组织,包括标准的章节、内容和要求等。

在制定标准框架时,需要参考相关的国际和行业标准,确保射频CSE标准与其他标准的一致性和兼容性。

步骤三:编写标准文本在制定标准框架之后,需要编写标准文本。

标准文本是射频CSE标准的主体部分,包括对射频设备的编码和测试要求的详细描述和规定。

编写标准文本时,需要确保语言准确、明确,规范射频设备的设计、制造和测试过程,确保射频设备的性能和可靠性。

步骤四:评审和修订在编写标准文本之后,需要进行评审和修订。

评审过程中,需要邀请相关的专家和机构对标准文本进行审查和评估,发现文本中可能存在的问题或不足,并提出修改建议。

修订过程中,需要根据评审结果对标准文本进行修改和完善,确保标准的准确性和适用性。

步骤五:标准发布和推广在标准文本修订完成后,需要将标准发布和推广。

标准发布的方式可以是通过行业组织、标准化机构、媒体等进行公告和发布。

标准推广的方式可以是通过培训、宣传、技术交流会议等进行,提高射频设备制造和使用者对射频CSE标准的认识和理解,促进标准的应用和推广。

sip 语音编码标准 -回复

sip 语音编码标准 -回复

sip 语音编码标准-回复SIP语音编码标准(SIP Voice Coding Standard)是一种用于实现音频通信的标准,它定义了在SIP媒体传输中使用的音频编码格式和相关参数。

本文将一步一步地解释SIP语音编码标准的相关概念、原理、常用编码格式以及一些应用示例。

第一步是了解SIP(Session Initiation Protocol)。

SIP是一种用于建立、修改和终止通信会话的网络协议,它主要用于呼叫控制和信令传递。

SIP 将媒体传输和信令传输分离,因此它需要一种标准来定义音频的编码和传输方式,这就是SIP语音编码标准。

接下来是理解音频编码的原理。

音频编码是将原始音频信号转换为数字数据的过程。

在SIP语音编码标准中,音频信号通过采样、量化、编码和传输等步骤进行数字化处理。

采样是将连续的模拟信号转换为离散的数字信号,量化是将采样后的信号映射为离散的数值,编码是使用特定的算法将量化后的信号压缩为较小的数据量,传输则是将压缩后的数据通过网络传送给接收方。

在SIP语音编码标准中,常用的音频编码格式有多种选择,如G.711、G.722、G.729等。

G.711是一种无损的音频编码格式,它主要用于模拟电话网络中的音频传输。

G.722是一种宽带音频编码格式,它可以提供更高的音频质量和更宽的频带宽度。

G.729是一种窄带音频编码格式,它可以将音频数据压缩到更小的带宽,并在低带宽网络环境下实现音频通信。

每种音频编码格式都有其特定的参数设置,如采样率、比特率、帧长度等。

这些参数可以根据具体的应用和网络环境进行调整。

例如,对于要求高音质的应用,可以选择较高的采样率和比特率;对于带宽受限的网络环境,可以选择较低的比特率和帧长度。

最后是一些SIP语音编码标准的应用示例。

SIP语音编码标准可以应用于各种语音通信场景,如网络电话、语音会议、实时语音广播等。

它可以在不同的网络环境和终端设备上实现高质量的语音通信。

例如,在企业中,可以使用SIP语音编码标准实现内部员工之间的实时语音通话,减少通信成本和提高工作效率。

智能电网设备统一编码标识标准体系研究及建议

智能电网设备统一编码标识标准体系研究及建议

智能电网设备统一编码标识标准体系研究及建议杨德胜;孙飞;汤晓君;吴红侠【摘要】This paper analyzes China's smart grid equipment unified coding identification standard,and puts forward China's global energy Internet architecture of smart grid equipment unified coding standard and construction ideas.According to the goods coding SNC and identification system for power station code identification system reference model,from the aspect of coding,labeling,transmission,analysis and application,this paper presents global energy Internet smart grid equipment unified coding standard system framework.Some suggestions on the development of the unified coding standard system for smart grid equipment in China are put forward.%分析我国智能电网设备统一编码标识标准现状,提出了我国在全球能源互联网架构下的智能电网设备统一编码标识标准体系目标及建设思路,并根据物品编码Ecode和电厂标识系统KKS的编码标识体系参考模型,从编码、标识、传输、解析和应用等方面,给出面向全球能源互联网的智能电网设备统一编码标识标准体系框架,并提出了我国智能电网设备统一编码标识标准体系发展的若干建议.【期刊名称】《微型电脑应用》【年(卷),期】2017(033)007【总页数】4页(P40-42,47)【关键词】智能电网;统一标识;全球能源互联网;标准体系框架【作者】杨德胜;孙飞;汤晓君;吴红侠【作者单位】国网信通产业集团公司安徽继远软件有限公司,合肥230088;国网信通产业集团公司安徽继远软件有限公司,合肥230088;国网信通产业集团公司安徽继远软件有限公司,合肥230088;国网信通产业集团公司安徽继远软件有限公司,合肥230088【正文语种】中文【中图分类】TP3911987年11月,水利部颁布的《电力系统部分设备统一编号准则》是我国最早的设备编码规范。

科尼变频器中英文手册

科尼变频器中英文手册
1.9.1 Fulfilled EMC-standards 现行的 EMC 标准 .................................................... 17
2 START-UP PROCEDURE 启动步骤 .................................................................................... 209
3 PARAMETER ADJUSTMENTS 参数调整 ............................................................................... 23
3.1 Control keypad operation 控制显示屏操作 .................................................................. 23 3.1.1 Navigation on the control keypad 控制显示屏演示 ......................................... 25 3.1.2 Value line editing 数值的编辑........................................................................ 25 3.1.3 Passwords 密码 ........................................................................................... 26 3.1.4 Monitoring 监控 .......................................................................................... 287

avs3 8k 超高清编码器技术要求和测量方法

avs3 8k 超高清编码器技术要求和测量方法

AVS3 8K 超高清编码器技术要求和测量方法引言AVS3(Audio Video Coding Standard 3)是中国自主研发的一种音视频编码标准,旨在提供高效的压缩性能和更好的视觉和听觉质量。

AVS3 8K 超高清编码器技术是在该标准基础上针对8K超高清视频内容进行编码的技术要求和测量方法。

本文将详细介绍 AVS3 8K 超高清编码器的技术要求和测量方法,包括编码器的功能要求、性能要求以及测试方法。

技术要求1. 编码器功能要求AVS3 8K 超高清编码器应具备以下功能要求:•支持8K分辨率:编码器能够处理8K分辨率的视频内容,保证高清画质的同时实现高效的压缩。

•多种编码模式:支持多种编码模式,包括帧内编码、帧间编码和混合编码,以满足不同场景下的编码需求。

•高效率压缩:编码器应采用高效的压缩算法,实现更高的压缩比,减少存储空间和传输带宽的需求。

•低延迟编码:编码器应具备低延迟编码能力,以满足实时传输和交互式应用的需求。

•高质量编码:编码器应保证编码后的视频质量尽可能接近于原始视频,减少失真和伪影。

•跨平台兼容:编码器应支持多种操作系统和硬件平台,以方便用户在不同设备上使用。

2. 编码器性能要求AVS3 8K 超高清编码器应具备以下性能要求:•高编码效率:编码器应能够在保证视频质量的前提下实现更高的压缩比,提高编码效率。

•低码率波动:编码器应尽量减少码率的波动,保持稳定的传输质量。

•低功耗:编码器在实现高编码效率的同时,应尽量降低功耗,提高能效。

•快速编码速度:编码器应具备快速的编码速度,以提高用户的使用体验。

•低延迟:编码器应具备低延迟的特性,减少视频传输过程中的延迟。

测量方法为了评估 AVS3 8K 超高清编码器的技术要求和性能要求,可以采用以下测量方法:1. 视频质量评估•主观评估:通过人眼观看编码后的视频,并与原始视频进行对比,评估视频质量的主观感受。

•客观评估:使用客观评估算法,如PSNR(Peak Signal-to-Noise Ratio)和SSIM(Structural Similarity Index),对编码后的视频进行质量评估。

avs2编码标准

avs2编码标准

avs2编码标准AVS2(Audio Video coding Standard 2),是中国自主研发的一种先进的音视频编码标准。

AVS2编码标准能够提供更高的压缩率和更好的视听品质,为音视频传输和存储领域的应用提供了更多可能性。

它是在AVS(Audio Video coding Standard)标准的基础上进行了改进和优化。

AVS2编码标准相比于AVS标准,在压缩率和性能方面有了显著的提升。

它采用了更严格的压缩算法和更先进的编码技术,能够在保证视听品质的同时,显著减少数据量。

这使得AVS2成为了处理高分辨率和高帧率视频的理想选择,为4K、8K甚至更高分辨率的视频提供了有力的支持。

AVS2编码标准的关键技术包括:1.预测技术:AVS2采用了更精确的运动估计和补偿技术,能够更好地捕捉视频中的运动信息。

通过对运动进行预测,可以减少视频数据中的冗余信息,进而提高压缩率。

2.变换和量化技术:AVS2采用了多种变换和量化方法,以更好地适应不同类型的视频内容。

通过将空域的视频信号转换为频域表示,可以进一步减少数据量。

同时,AVS2还引入了自适应量化技术,根据视频内容的特点动态调整量化参数,以提高编码效果。

3.熵编码技术:AVS2使用了一种高效的熵编码算法,能够将压缩后的视频数据进一步减少。

这种算法能够根据数据的统计特性,为不同的数据段分配不同长度的编码,以达到更好的压缩效果。

AVS2编码标准在实际应用中已经取得了广泛的成功。

它被应用于数字电视、视频监控、移动通信等领域,得到了业界的认可和推广。

AVS2编码标准还为中国在国际音视频编码领域的发展做出了重要贡献,提高了中国在标准化工作中的话语权和影响力。

另外,AVS2编码标准的开放性也为各类厂商和研究机构提供了良好的合作平台。

通过参与和贡献,各方可以共同推动AVS2标准的发展,并在实践中不断优化和改进。

这种开放的合作模式有助于加快技术创新和产业发展,为用户提供更高质量的音视频体验。

腾讯编码规范

腾讯编码规范
本标准适用于腾讯集团(含分公司等各级分支机构)所有使用Java作为开发语言的软件产品。
本标准中“腾讯集团”是指腾讯控股有限公司、其附属公司、及为会计而综合入账的公司,包括但不限于腾讯控股有限公司、深圳市腾讯计算机系统有限公司、腾讯科技(深圳)有限公司、腾讯科技(北京)有限公司、深圳市世纪凯旋科技有限公司、时代朝阳科技(深圳)有限公司、腾讯数码(深圳)有限公司、深圳市财付通科技有限公司。
12附录
附录A《编码安全规范》
附录A
(规范性附录)
编码安全规范
———————————
7.4.3尽量避免单个字符的变量名,除非是一次性的临时变量。临时变量通常被取名为i,j,k,m和n,它们一般用于整型;c,d,e,它们一般用于字符型;
7.4.4不采用匈牙利命名法则,对不易清楚识别出该变量类型的变量应使用类型名或类型名缩写作其后缀,例如:
7.4.5组件或部件变量使用其类型名或类型名缩写作其后缀,例如:
8.3.4避免声明的局部变量覆盖上一级声明的变量,即不要在内部代码块中声明相同的变量名;
8.3.5公共和保护的可见性应当尽量避免,所有的字段都建议置为私有,由获取和设置成员函数(Getter、Setter)访问;
8.3.6定义一个变量或者常量的时候,不要包含包名(类似java.security.MessageDigest digest = null),而要定义成下面的格式,除非是两个包有相同的类名:
常量
类变量
实例变量:
公有字段
受保护字段
友元字段
私有字段
9异常
9.1捕捉异常的目的是为了处理它。
9.2多个异常应分别捕捉并处理,避免使用一个单一的catch来处理。
10习惯
10.1if、for、do、while等语句的执行语句部分无论多少都要加括号"{}";

x86的编码格式

x86的编码格式

x86 是一种常见的处理器架构,其指令集体系结构采用变长指令编码格式。

x86 指令编
码格式包括不同长度的指令前缀、操作码(Opcode)、操作数和寻址模式。

在 x86 架构中,指令长度可以是 1 到 15 个字节不等。

常见的指令长度为 1 到 6 个字节。

以下是 x86 指令编码的常见格式:
1. 前缀字节(Prefix Byte):前缀字节用于修改指令的某些属性,如操作数大小、地址
大小等。

2. 操作码(Opcode):操作码指定了要执行的具体操作,如加法、乘法、跳转等。

3. ModR/M 字节(ModR/M Byte):ModR/M 字节用于指定操作数的寻址模式和寄存
器信息。

4. SIB 字节(SIB Byte):SIB 字节(Scale-Index-Base Byte)用于复杂的内存寻址模式,包括乘法因子、索引寄存器和基址寄存器。

5. Displacement 字节(Displacement Byte):偏移字节用于指定操作数的相对地址或立
即数值。

6. 立即数(Immediate):立即数是指指令中直接给出的操作数值。

需要注意的是,x86 指令编码格式非常复杂,因为它需要支持多种不同的操作数类型和寻址模式。

这样的设计使得 x86 架构非常灵活和功能强大,但也增加了指令解码和执
行的复杂性。

AVS与MPEG-2视频转码技术的研究与实现的开题报告

AVS与MPEG-2视频转码技术的研究与实现的开题报告

AVS与MPEG-2视频转码技术的研究与实现的开题报告一、选题背景在当前数字化的信息时代,视频成为了人们生活和工作中不可或缺的一部分,视频领域的技术也在快速发展和变化着。

MPEG(Moving Picture Experts Group)和AVS (Audio Video Coding Standard)是比较常见的两种视频编码标准,分别在不同的应用场景中广泛应用。

在多媒体传输和存储应用领域中,需要将MPEG-2格式的视频编码转换成AVS格式,因此开展AVS与MPEG-2视频转码技术的研究具有重要的意义。

二、研究内容与目标本课题旨在研究AVS与MPEG-2视频转码技术的相关理论和算法,并实现一套综合的转码软件工具。

具体研究内容包括:1.分析AVS和MPEG-2视频编码标准的特点和差异,比较两者优缺点以及适用场景。

2.研究视频转码的相关理论和算法,探讨不同转码方法的优劣和适用性,并选择合适的转码算法。

3.设计并实现一套AVS与MPEG-2视频转码软件,支持多种视频输入输出格式,提高转码效率和质量。

三、研究意义与应用价值本课题的研究意义主要在于:1.深入理解AVS和MPEG-2视频编码标准的特点和应用场景,为在实际应用中选择适合的编码标准提供理论支持。

2.探索视频转码的相关算法和方法,提高视频的适应性和传输效率,为视频广泛应用提供技术支持。

3.设计实现一套综合的AVS与MPEG-2视频转码软件,提高视频转码的质量和效率,为视频存储和传输提供便利和支持。

四、研究方法和技术路线本课题的研究方法和技术路线如下:1.文献调研:查阅相关的论文、技术资料和标准文献,调研AVS和MPEG-2视频编码标准的特点和不同之处,以及视频转码的相关理论和方法。

2.算法研究:研究不同的视频转码算法和方法,比较其优缺点和适用性,选择最适合的转码算法。

3.软件设计:设计具有扩展性和可定制性的AVS与MPEG-2视频转码软件,考虑多种输入输出格式及转码参数设置。

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编码规范Coding Standard1. 命名和书写规范1) 方法和类型的命名按照Pascal命名规范,即名称中每个字符子串第一个字母大写。

public class S ome C lass{public S ome M ethod(){}}2) 局部变量和方法的参数的命名规范,一般本地变量用m开头;方法参数用a开头;方法体里定义的变量以l开头;int mN umber;void MyMethod(int aS ome N umber){int l Count;}3) 方法的命名采用verb-object(行为-目标)结构(动宾短语),例如:ShowDialog()4) 有返回值的方法的名字应该采用可以描述其意义的名字,例如:GetObjectState()5) 使用描述性的变量名a) 避免使用单字母的变量名,如i,t等,应该采用index 和temp 代替。

(只在循环内使用的局部变量可以使用单字母变量)b) 避免使用匈牙利命名法命名public 和protected 的成员。

c) 尽量避免使用单词的缩写(如用num 代替number)6) 尽量使用c#定义的类型原形而不是用在System 命名空间中重定义的变量名。

用object 而不用Object用string 而不用String用int 而不用Int327) 添加引用应该使用using 替代。

8) 避免在命名空间内部使用using 语句。

9) 把所有使用的命名空间放在一起,并先排framework的命名空间再排自己获第三方的命名空间。

using System;using System.Collections;using ponentModel;using System.Data;using MyCompany;using MyControls;10) 保持精确的缩进a) 使用Tab或其他非标准缩进。

11) 注释的缩进和同级的代码的缩进保持一致。

12) 所有文档的注释都要进行拼写检查,错误的注释拼写会严重影响代码的可读性。

13) 所有的成员变量应该放在顶部,并用一个空行把它与方法和属性分开。

public class MyClass{int m_Number;string m_Name;public void SomeMethod1(){}public void SomeMethod2(){}}14) 局部变量的申明应尽可能与第一次使用它的地方接近。

15) ( { )应该占一个新行并处于开头。

2.注释1) 源程序有效注释量需占源程序20%以上。

注释格式要统一。

2) 避免使用一组图形或者特殊符号做成一个块或者长方形等的注释形式。

这样可能开起来很生动,但是却很难维护。

3) 删除所有暂时的或者无用的注释,从而避免未来维护工作的混淆。

4) 在修改代码的同时,一定要始终保持注释的同步更新。

5) 在每一个程序的最初阶段,有必要提供标准的注释样本,来解释该程序的目的、运行前提条件和相应的限制点。

一个注释样本应该是对于该程序为什么编写,程序主要要完成什么样的功能等,做一个简单的描述。

6)对于行注释,要加在该行的上一行。

用c++风格的双斜线“//”来标识。

对于块注释,加载块的顶部,用c风格的“/* */”来标识。

7)当书写注释的时候,必须使用完整的句子注释应该是使代码含义清晰的,而不是去增加不明确性。

避免那些冗余的或者不合适的注释,比如一些幽默的旁记等等。

使用注释来解释代码的目的,而不是代码的单纯的翻译。

8) 在你编码的时候就书写注释。

因为可能到后来你就没有时间去书写它们了。

而且,如果给你一个机会让你去重新访问你已经写完的代码,可能你对今天刚刚写完的代码非常清楚,但是对于六周之前写的代码可能都已经模糊不清了。

9) 在代码中任何不能明显读懂的地方都要书写注释。

10)说明性文件头部应进行注释,注释必须列出:版本、类名、文件名、作者、完成日期、功能描述、修改历史(修改日期、修改者、修改内容)等,头文件的注释中还应有函数功能简要说明。

11)函数头部应进行注释,列出:函数的目的/功能、输入参数、输出参数、返回值、调用关系(函数、表)等。

示例:/*************************************************Function: // 函数名称Description: // 函数功能、性能等的描述Calls: // 被本函数调用的函数清单Called By: // 调用本函数的函数清单Table Accessed: // 被访问的表(此项仅对于牵扯到数据库操作的程序)Table Updated: // 被修改的表(此项仅对于牵扯到数据库操作的程序)Input: // 输入参数说明,包括每个参数的作// 用、取值说明及参数间关系。

Output: // 对输出参数的说明。

Return: // 函数返回值的说明Others: // 其它说明*************************************************/注释应与其描述的代码相近,对代码的注释应放在其上方或右方(对单条语句的注释)相邻位置,不可放在下面,如放于上方则需与其上面的代码用空行隔开。

注释与所描述内容进行同样的缩排。

3. 编码实践1) 避免把多个类放在同一个文件中。

2) 一个文件应该只有一个命名空间,避免在同一个文件中有多个命名空间。

3) 为便于查看代码,代码行长度不要超过80个字符。

可以采用分行显示!4) 禁止手工更改编译器产生的代码。

5) 可能的情况下,尽量不要使用原义数字或原义字符串,如For i = 1 To 7。

而是使用命名常数,如For i = 1 To NUM_DAYS_IN_WEEK 以便于维护和理解。

6) 对于只读型的变量,不要采用const 定义为常量而应直接定义为readonly 型。

例如:public class MyClass{public readonly int Number;public MyClass(int someValue){Number = someValue;}public const int DaysInWeek = 7;}7) 在同一个编译单元中避免有多个Main() 。

8) 只有非常有必要的情况下采用public ,否则应采用受保护的关键字。

9) 避免使用friend 关键字,它会增加编译单元之间的耦合程度。

10) 沿逻辑结构行缩进代码。

即便是代码块只有一行代码。

11) 避免使用三操作数的条件表达式12) 避免在条件表达式中直接调用有布尔型返回值的函数,而应该先将其返回值赋给一个本地变量。

例如:bool IsEverythingOK(){…}//Avoid:if(IsEverythingOK()){…}//Instead:bool ok = IsEverythingOK();if(ok){…}13) 尽量使用用零初始化的数组。

14) 在类和接口中,方法和属性的比率应至少为2:1。

15) 避免只有一个成员接口,每个接口尽量保持12个左右的成员,最多不超过20个。

16) 避免将事件作为接口的成员。

17) 避免使用abstract (抽象)方法,应用接口替代。

18) 要直接呈现到用户终端的字符串不要直接编码而应采用资源文件。

(主要是考虑多语言支持,我们目前可不考虑)19) 要因不同环境发生改变的字符串不要直接编码,如数据库的连接字符串。

20) 当使用较长字符串时,用StringBuilder 代替string。

21) 当提供一个静态的成员变量时要提供一个静态的构造函数。

22) 尽量避免使用goto 。

23) 在switch 选择中应定义一个default 选择。

int number = SomeMethod();switch(number){case 1:Trace.WriteLine("Case 1:");break;case 2:Trace.WriteLine("Case 2:");break;default:Debug.Assert(false);break;}24) 除了在一个构造器内调用另一个构造器,否则不要使用this 引用。

//Example of proper use of ’this’public class MyClass{public MyClass(string message){}public MyClass() : this("hello"){}}25) 除了在解决子类与基类成员冲突和调用基类构造函数外避免使用base 关键字。

//Example of proper use of ’base’public class Dog{public Dog(string name){}virtual public void Bark(int howLong){}}public class GermanShepherd : Dog{public GermanShepherd(string name): base(name){}override public void Bark(int howLong){base.Bark(howLong);}}。

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