Extensible Binary Meta Language
RFC 8794

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Internet Engineering Task Force (IETF)                         S. Lhomme
Request for Comments: 8794                                              
Category: Standards Track                                        D. Rice
ISSN: 2070-1721                                                         
                                                               M. Bunkus
                                                               July 2020

                    Extensible Binary Meta Language

Abstract

   This document defines the Extensible Binary Meta Language (EBML)
   format as a binary container format designed for audio/video storage.
   EBML is designed as a binary equivalent to XML and uses a storage-
   efficient approach to build nested Elements with identifiers,
   lengths, and values.  Similar to how an XML Schema defines the
   structure and semantics of an XML Document, this document defines how
   EBML Schemas are created to convey the semantics of an EBML Document.

Status of This Memo

   This is an Internet Standards Track document.

   This document is a product of the Internet Engineering Task Force
   (IETF).  It represents the consensus of the IETF community.  It has
   received public review and has been approved for publication by the
   Internet Engineering Steering Group (IESG).  Further information on
   Internet Standards is available in Section 2 of RFC 7841.

   Information about the current status of this document, any errata,
   and how to provide feedback on it may be obtained at
   https://www.rfc-editor.org/info/rfc8794.

Copyright Notice

   Copyright (c) 2020 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (https://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction
   2.  Notation and Conventions
   3.  Structure
   4.  Variable-Size Integer
     4.1.  VINT_WIDTH
     4.2.  VINT_MARKER
     4.3.  VINT_DATA
     4.4.  VINT Examples
   5.  Element ID
   6.  Element Data Size
     6.1.  Data Size Format
     6.2.  Unknown Data Size
     6.3.  Data Size Values
   7.  EBML Element Types
     7.1.  Signed Integer Element
     7.2.  Unsigned Integer Element
     7.3.  Float Element
     7.4.  String Element
     7.5.  UTF-8 Element
     7.6.  Date Element
     7.7.  Master Element
     7.8.  Binary Element
   8.  EBML Document
     8.1.  EBML Header
     8.2.  EBML Body
   9.  EBML Stream
   10. EBML Versioning
     10.1.  EBML Header Version
     10.2.  EBML Document Version
   11. Elements semantics
     11.1.  EBML Schema
       11.1.1.  EBML Schema Example
       11.1.2.  "<EBMLSchema>" Element
       11.1.3.  "<EBMLSchema>" Namespace
       11.1.4.  "<EBMLSchema>" Attributes
       11.1.5.  "<element>" Element
       11.1.6.  "<element>" Attributes
       11.1.7.  "<documentation>" Element
       11.1.8.  "<documentation>" Attributes
       11.1.9.  "<implementation_note>" Element
       11.1.10. "<implementation_note>" Attributes
       11.1.11. "<restriction>" Element
       11.1.12. "<enum>" Element
       11.1.13. "<enum>" Attributes
       11.1.14. "<extension>" Element
       11.1.15. "<extension>" Attributes
       11.1.16. XML Schema for EBML Schema
       11.1.17. Identically Recurring Elements
       11.1.18. Textual expression of floats
       11.1.19. Note on the use of default attributes to define
               Mandatory EBML Elements
     11.2.  EBML Header Elements
       11.2.1.  EBML Element
       11.2.2.  EBMLVersion Element
       11.2.3.  EBMLReadVersion Element
       11.2.4.  EBMLMaxIDLength Element
       11.2.5.  EBMLMaxSizeLength Element
       11.2.6.  DocType Element
       11.2.7.  DocTypeVersion Element
       11.2.8.  DocTypeReadVersion Element
       11.2.9.  DocTypeExtension Element
       11.2.10. DocTypeExtensionName Element
       11.2.11. DocTypeExtensionVersion Element
     11.3.  Global Elements
       11.3.1.  CRC-32 Element
       11.3.2.  Void Element
   12. Considerations for Reading EBML Data
   13. Terminating Elements
   14. Guidelines for Updating Elements
     14.1.  Reducing Element Data in Size
       14.1.1.  Adding a Void Element
       14.1.2.  Extending the Element Data Size
       14.1.3.  Terminating Element Data
     14.2.  Considerations when Updating Elements with Cyclic
            Redundancy Check (CRC)
   15. Backward and Forward Compatibility
     15.1.  Backward Compatibility
     15.2.  Forward Compatibility
   16. Security Considerations