INTERNATIONAL ORGANISATION FOR STANDARDISATION
ORGANISATION INTERNATIONALE DE NORMALISATION
ISO/IEC JTC1/SC29/WG11
CODING OF MOVING PICTURES AND AUDIO

ISO/IEC JTC1/SC29/WG11 N11959
March 2011, Geneva, Switzerland

Source	Systems
Status	Approved
Title	MPEG-4 LASeR Presentation and Modification of Structured Information: 1-pager
Author	Jihun Cha, Electronics and Telecommunications Research Institute (ETRI), Korea

MPEG-4 LASeR Presentation and Modification of Structured Information (PMSI)
Providing Tools for Presenting and Modifying Structured Information

1         Motivation

MPEG-4 LASeR Presentation and Modification of Structured Information (ISO/IEC 14496-20:2008 AMD3) introduces a specific mechanism to present any Structured Information (any document conforming a given schema such as MPEG-21 DI or TVAnytime) in a consistent manner using Presentation Information (MPEG-4 LASeR). It also provides a means to reflect the result of the presentation back into the Structured Information.

The PMSI functions provide a rich presentation tool with the structured information as well as a flexible scene representation method with the presentation information. Therefore, the scene representation author can take advantage in composing the scene by separating into two parts as the presentation and structured information. It is efficient scene composition method because the modification from the one part does not affect the other one such as HTML and CSS. For instance, a feature-rich (such as graphical layout of channel information and predefined user interactions) channel guide can be provided using this specification by accessing incoming EPG structured information and presenting declaratively. Furthermore, the PMSI can be applied to a daily or hourly changed scene with a static layout, multilingual subtitles in a single video clip and so on.

The two main functions of the MPEG-4 LASeR PMSI standard are External Reference and External Update. Moreover, there is a unique referencing method of the fragments of structured information. These functions and method are described in the following clauses.

2         Referencing the fragments of structured information

The file type of the structured information is an XML-based document. To access a specific fragment of structured information, a pointer scheme for structured information is defined. This scheme is a specific URI form and composed by using the W3C XPointer framework and XPath function.

3         External Reference

The External Reference is a function of referencing a specific fragment of Structured Information from Presentation Information. The purpose of the External Reference function is to identify the scope of the scene to be updated regularly with the latest version of Structured Information at the specified interval of time.

4         External Update

The External Update function supports a modification of Structured Information. It supports three types of modification: "replace", "insert", and "delete". A part of Structured Information can be replaced with a new element or an attribute value, a new element or an attribute value is inserted into Structured Information, or a part of Structured Information can be deleted according to the provided ‘type’ attribute.