SMPTE EG42
4 Introduction
This engineering guideline is intended to provide guidance for implementing descriptive metadata within the
header metadata of an MXF file (SMPTE 377M). This document supplements the MXF Engineering Guideline
(SMPTE EG41).
This document is divided into a number of core sections, each section describing a particular aspect of
descriptive metadata. The sections (together with their section number) are as follows:
1. Section 4 : This introduction, including the usage of descriptive metadata and a catalogue of user
requirements for descriptive metadata.
2. Section 5 : The mechanisms by which descriptive metadata in the MXF header metadata may be
linked to the essence in the MXF essence container.
3. Section 6 : A description of the issues related to implementing a descriptive metadata model from the
perspective of both MXF and AAF.
4. Section 7 : How to implement descriptive metadata as a sequence of KLV packets in the MXF header
metadata and as XML for text-based interfacing.
5. Section 8 : Guidance for implementing both MXF descriptive metadata and non-MXF descriptive
metadata.
6. Annex A: Provides a discussion of metadata characteristics.
7. Annex B: Provides an introduction to data modelling techniques.
8. Annex C: Provides an example of the options for XML coding
9. Annex D: Bibliography of useful reading.
4.1 Dimensions of Descriptive Metadata Use
In general terms, the use of descriptive metadata has many dimensions as follows:
1. It is in widespread use within different content-based industries, including broadcast, film, music and web
authoring.
2. It is in widespread use in different content-based applications, including capture/creation, production, post-
production and archive/libraries.
3. It can be divided into several different broad categories including business transactions, publication
information, content identification and labeling, compositional information and formatting, etc.
4. It may have different states such as being static for a defined duration, being dynamic (with several kinds
of dynamic including transitory, metronomic, incrementing and so on).
5. It may have different levels of stability with elements having durable values that remain stable or transient
values that may frequently change.
In the header metadata of an MXF file, the metadata is persisted and may be distributed over many copies.
Thus descriptive metadata in an MXF file should include only that metadata which can be considered copy
persistent. This does not mean that a value can never change between copies, but that, once written, individual
copies must be edited where changes are required. For some types of metadata, this is not only acceptable, but
encouraged, e.g. a property that defines the number of copies made.
One of the primary aims of this document is to identify that metadata which can be used to enhance the
description of the content in a file. Metadata that is appropriate for use in databases is not part of this document.
Annex A describes metadata characteristics that may aid the reader to understand the attributes of different
kinds of metadata items.
Page 3 of 27 pages
