SMPTE EG 377-3-2013 Material Exchange Format (MXF) - Engineering Guideline (Informative).pdf

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1、 Copyright 2013 by THE SOCIETY OF MOTION PICTURE AND TELEVISION ENGINEERS 3 Barker Avenue, White Plains, NY 10601 (914) 761-1100 Approved January 29, 2013 Warning: This Engineering Guideline is purely informative and meant to provide tutorial information to the industry about a Standard or Recommend

2、ed Practice. Do not rely on this for interoperability, but rather the Standards and Recommended Practices referenced herein. Table of Contents Page Foreword 2 Introduction 2 1 Scope 4 2 MXF Document Suite Structure 4 2.1 About this Document 5 3 MXF Concepts 5 3.1 MXF Background 6 3.2 MXF Design Crit

3、eria . 6 4 MXF File Structure 7 4.1 What are the File Header, the File Body and the File Footer? . 7 4.2 MXF Partitions 7 4.3 KLV Coding in MXF 9 4.4 MXF Metadata 11 4.5 MXF Essence 13 4.6 MXF File Tools 14 5 MXF Interoperability 16 5.1 Working with Stream Interfaces 16 5.2 MXF Interoperability with

4、 Other Files . 17 6 A Guide to the Wording of the MXF Dtandards 17 6.1 Conformance Text 17 6.2 Functional Descriptions Encoder Required, etc. 18 6.3 Encoding and Decoding Concepts . 18 6.4 Essential Terms 19 7 Metadata Classifications and Placement 21 7.1 Embedded Metadata Location 22 7.2 Linked Met

5、adata Location . 22 7.3 Attached Metadata Location . 23 7.4 Server Metadata Location . 23 SMPTE ENGINEERING GUIDELINE Material Exchange Format (MXF) Engineering Guideline (Informative) Page 1 of 47 pages SMPTE EG 377-3:2013 SMPTE EG 377-3:2013 Page 2 of 47 pages 8 MXF Header Metadata Concepts. 23 8.

6、1 What are Objects? . 23 8.2 What is a Class? 24 8.3 What is a Package? . 24 8.4 How are Packages Coded? . 26 8.5 Using ULs and UUIDs 29 8.6 Coding Objects as Sets 31 8.7 Using Text 32 8.8 Tracking Changes with Generation Numbers 32 9 MXF in Detail 33 9.1 General Overview 33 9.2 Content Package Mode

7、l . 34 9.3 MXF Essence Containers 35 9.4 Mapping Essence and Metadata into the MXF Generic Container 39 9.5 How MXF Header Metadata Relates to the Essence Container 40 9.6 Operational Patterns 42 9.7 MXF Decoder Design . 45 Annex A Bibliography Further Reading 47 SMPTE EG 377-3:2013 Page 3 of 47 pag

8、es Foreword SMPTE (the Society of Motion Picture and Television Engineers) is an internationally-recognized standards developing organization. Headquartered and incorporated in the United States of America, SMPTE has members in over 80 countries on six continents. SMPTEs Engineering Documents, inclu

9、ding Standards, Recommended Practices, and Engineering Guidelines, are prepared by SMPTEs Technology Committees. Participation in these Committees is open to all with a bona fide interest in their work. SMPTE cooperates closely with other standards-developing organizations, including ISO, IEC and IT

10、U. SMPTE Engineering Documents are drafted in accordance with the rules given in Part XIII of its Administrative Practices. SMPTE EG 377-3 was prepared by Technology Committee 31FS. Introduction The Material Exchange Format (MXF) was developed by the industry to provide a means of exchanging video,

11、audio, data essence and metadata content in a unified data format. The MXF file structure provides a means of exchanging metadata using a formal data structure that permits interoperability together with an essence container that can accommodate many different essence formats both compressed and unc

12、ompressed and including video streams, individual pictures, sound and essence data (such as sub-titles, VBI data etc.). The starting point of the work was the report from the Task Force for Harmonized Standards for the Exchange of Program Material as Bitstreams as identified in the Bibliography. The

13、 work of this report was used as the basis for an exchange file format by the Pro-MPEG Forum which acted as a catalyst to encourage industry-wide participation to create a unified file format that could be used for distribution, exchange and cut-editing. The results of this initial development were

14、then brought to SMPTE to create an internationally recognized sets of standards, recommended practices and engineering guidelines that form the MXF document suite. The other key aspect of the development of MXF was the adoption of the SMPTE Key-Length-Value approach to coding the whole of the MXF fi

15、le structure using both individual and group coding for a consistent approach within the whole file format. The evolution of XML coding can be seen as attractive, but in many cases, such coding is not suitable for the high-speed and wide-bandwidth requirements of high definition digital television a

16、nd digital cinema. Instead, there are methods that can be used to transform the metadata parts of MXF files to XML and vice-versa (though only practical for the metadata part of MXF files). SMPTE EG 377-3:2013 Page 4 of 47 pages 1 Scope This guideline gives an introduction to and the background for

17、the Material eXchange Format (MXF). This guideline describes the technology involved in the format, the names of the various elements within the format, and the way in which the format can be used within the real world applications. Some parts of the descriptions within this guideline are generic to

18、 file formats, while other parts are specific to the material exchange format. There are descriptions of the object-oriented technology used within the MXF format, as well as a discussion of the metadata that can be used within the file. There are worked examples within this guideline to guide users

19、 and help improve the interoperability of applications using different MXF files. 2 MXF Document Suite Structure The MXF specification is split into a number of categories in order to create a document structure that allows new applications to be covered in the future. These categories are: Category

20、 1 MXF File Format Specification Normative (SMPTE ST 377-1) Category 2 MXF File Format Extensions Normative (e.g. SMPTE ST 377-2 is the KLV Extension Syntax, KXS) Category 3 Engineering Guidelines Informative (including this document) Category 4 Operational Patterns Normative (e.g., OP1a is SMPTE ST

21、 378) Category 5 MXF Descriptive Metadata Schemes Normative (e.g., DMS-1 is SMPTE ST 380) Category 6 Essence Containers Normative (e.g., the MXF Generic Containers: SMPTE ST 379-1 and SMPTE ST 379-2) Category 6a Mapping Essence and Metadata into the Essence Container Normative (e.g., Mapping MPEG St

22、reams into the Generic Container is SMPTE ST 381 (all parts) When creating an MXF application or system, you need to ensure that you have the latest versions of all of these documents. Note that in some cases, the MXF specifications have been revised by splitting into multiple parts (e.g. SMPTE ST 3

23、81 parts 1n) or providing different variants (e.g. SMPTE ST 379-1 and SMPTE ST 379-2). The MXF categories are summarized below. Category 1 is a normative definition of the format of an MXF file. It defines the toolbox from which different file interchange tools can be chosen to fulfill the requireme

24、nts of different applications. The MXF file format defines the syntax and semantics of MXF files. Since MXF is an extensible format, new standards can be added that define extensions to the format defined by SMPTE ST 377-1. Category 1 also contains formal definitions of the many acronyms, terms and

25、data types used in the MXF specifications, including this engineering guideline. SMPTE EG 377-3:2013 Page 5 of 47 pages Category 2 provides for extensions to the file format to provide tools not present in the basic file format. These extensions provide new tools to extend the capabilities on MXF to

26、 provide extra functionality as needed for specialist applications, Category 3 contains informative documents that help users to understand various aspects of MXF. This document is MXF engineering guideline, which is an introduction to MXF. This document introduces many of the concepts and explains

27、what problems MXF is intended to solve. Part 3 also includes other engineering guidelines, including a descriptive metadata engineering guideline (SMPTE EG 42), which explains the concepts behind the use of descriptive metadata in MXF files. Other engineering guidelines can be added to the MXF docum

28、ent suite as and when there is a requirement. Category 4 documents describe the operational patterns of the MXF format. In order to create an application to solve a particular interchange problem, some constraints and structural metadata definitions are required before SMPTE ST 377-1 can be used. An

29、 operational pattern defines those restrictions of the format that allow interoperability between applications of defined levels of complexity. Applications that use the MXF format need to adhere to one of the operational patterns in order to achieve interchange. Category 5 documents define MXF desc

30、riptive metadata sets that can be plugged in to an MXF file. Different application environments will require different metadata sets to be carried by MXF. These collections of metadata sets are described in the part 5 document(s). Category 6 documents define the essence container of the MXF format f

31、or containing picture and sound essence. There can be limitations to the essence container that are needed for a particular operational pattern. The reader is advised to cross-reference at least categories 1 and 4 both before and during implementation. The MXF generic container is a standardized ess

32、ence container providing an encapsulation mechanism that allows many formats to be mapped into MXF. Category 6a comprises a number of documents for mapping many of the essence and metadata formats used in the content creation industry into the defined MXF essence container. The MXF document suite ma

33、kes reference to other documents that contain information required for an MXF system. One such document is SMPTE ST 336 that provides the basic coding rules used throughout MXF. Other documents include the SMPTE metadata dictionary, SMPTE RP 210, which contains definitions of metadata parameters and

34、 the SMPTE Labels Register, SMPTE RP 224, which contains a list of defined 16-byte labels for use in MXF sets. SMPTE ST 377-1 provides a full list of all MXF documents for user guidance. The Bibliography of this document provides a list of additional documents and publications for background reading

35、 to aid the understanding of MXF. 2.1 About this Document The information in this document is ordered to aid readability. Concepts are introduced gradually and repeated in more detail later in the document. This is done to make the document easier to read; however, it does make the document somewhat

36、 less useful as a guide. The table of contents see pages 1 and 2 is provided at the start of the document to allow easy access to each heading within the document. This document is a guideline and does not specify conformance points. Nor does this document contain conformance terms except where pres

37、ent in a quote from normative documents for the purpose of illustration. 3 MXF Concepts The concepts in MXF are introduced in a way that gives an overall view of the specification and the concepts embodied within it. Once the introduction is understood, the requirements of the file format are discus

38、sed. Some specific words and phrases used in the specification are then defined and finally SMPTE EG 377-3:2013 Page 6 of 47 pages the material exchange format is introduced in much more detail. Although this entire document is informative, its aim is to give sufficient information for technical and

39、 non-technical readers to have a basic understanding of MXF. 3.1 MXF Background The MXF specification is designed to interchange multimedia information as a file. The design allows users to take advantage of non-real time transfers and to package together essence and metadata for effective interchan

40、ge between servers and between businesses. MXF is not a panacea, but is an aid to automation and machine-to-machine communication. It allows essence and metadata transfer without the metadata elements having to be manually re-entered. The MXF specification is intended to allow the storage and interc

41、hange of video, audio, data essence and metadata as a file. MXF files can be efficiently stored on a variety of physical media as well as transported over communications links. Finally, the MXF specification is intended to be extensible. Considerable effort was put into ensuring that SMPTE ST 377-1

42、is compression codec independent, resolution independent and can be constrained where needed to suit a large number of application environments. The document structure has been created to allow new applications to extend MXF in a backwards-compatible way. 3.2 MXF Design Criteria The MXF file format

43、was designed for use in high throughput hardware or software devices. This translates into the need for well-defined design parameters for buffer size, latency, and the need for algorithmic simplicity. MXF is also intended to cover a very large application space, and not all the requirements apply t

44、o all the applications. 3.2.1 Representing multi-byte numbers There are two distinct ways in which multi-byte numbers are stored in computer systems - big-endian and little-endian. Big-endian systems place higher value bytes in the lower value addresses (i.e. MSB first), whereas little-endian system

45、s do the reverse. Because of the two storage formats, MXF defines the storage format as follows: MXF header metadata uses the big-endian data format only. The primary reason behind this decision was to address the handling of dark metadata where the endian-ism cannot be known (because the metadata i

46、s dark). Essence containers use the byte order defined by the individual specifications of each essence container where needed. 3.2.2 Requirements for application diversity Some applications can require metadata to be processed separately from the essence data. Other applications can require metadat

47、a to be stored with the essence data. This requires efficient insertion and extraction of the metadata from the essence data container(s) of the file. Indexing of the file content is desirable to provide for rapid access to the file contents and this desire is served by the provision of index tables

48、. Some applications prefer such index tables to be accessed separately from the essence; others can require the two to be accessed together. In some cases, the index tables are most naturally stored at the start of the file; however, while recording, the most natural location is at the end of the fi

49、le. This diversity requires efficient insertion, extraction and relocation of index tables within the file. SMPTE EG 377-3:2013 Page 7 of 47 pages 4 MXF File Structure The MXF format follows a common theme of many file formats with the following basic structure: A file header that provides information about the file as a whole, including labels for the early determination of decoder compliance. The header metadata in the file header is a complex data structure that provides a full description of the contents o