Overview
ISO/IEC 14496-20:2008/Amd 3:2010, titled Information technology - Coding of audio-visual objects - Part 20: Lightweight Application Scene Representation (LASeR) and Simple Aggregation Format (SAF) - Amendment 3: Presentation and Modification of Structured Information (PMSI), is an international standard developed by ISO and IEC. This amendment enhances the LASeR and SAF framework by introducing mechanisms for the presentation and dynamic modification of structured information within audio-visual objects. The PMSI extension enables precise updates and modifications of scene representations, promoting efficient and flexible multimedia content delivery.
Key Topics
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Presentation and Modification of Structured Information (PMSI):
PMSI defines protocols to access and manipulate structured information fragments within LASeR scenes, facilitating spatio-temporal control of multimedia elements.
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mpeg-pmsi() URI Scheme:
This pointer scheme integrates with the W3C XPointer framework and XPath syntax to enable granular referencing and filtering of structured data embedded in LASeR scenes. It supports querying of specific elements and attributes to target modifications dynamically.
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ExternalResourceEvent and Scene Updates:
Introduction of events such as ExternalResourceEvent informs the presentation engine of updates to external structured information resources via URLs. This supports periodic or on-demand refresh of scene components.
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LASeR externalReference Element:
Allows declaration of scene segments that are updated at defined intervals (updateInterval), ranging from a single evaluation ("none") to continuous or scheduled updates. Attributes control security, scope (entry point), and update behavior.
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LASeR externalUpdate Element:
Enables three types of structured information modifications within scenes:
- Replace: Substitutes existing elements or attribute values.
- Insert: Adds new elements or attribute values.
- Delete: Removes specified elements or attribute values.
Modifications are specified with precision through attributes such as
xlink:href, type, attributeName, index, and update scheduling.
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Support for SVG1.1 tref Element:
Extends conventional SVG references by allowing editable textual content within LaSer scenes, enabling live updates to referenced data.
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Structured Data Syntax and Extensions:
Defined via Extended Backus-Naur Form (EBNF) and enriched with supplemental classes (SVGAmd3Extension, LASeRAmd3Extension) for structured data handling, ensuring compatibility and extensibility of LASeR scene graphs.
Applications
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Dynamic Multimedia Presentations:
Enables real-time updates to audio-visual scene components without complete resynchronization, improving responsiveness in interactive TV, digital signage, and augmented reality applications.
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Efficient Content Aggregation:
The Simple Aggregation Format (SAF) combined with PMSI facilitates streamlined packaging and transmission of multimedia data with structured metadata referencing.
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Targeted Scene Updates in Bandwidth Sensitive Environments:
By updating only the changed segments of structured information through externalReference and externalUpdate, streaming services can optimize bandwidth usage while maintaining scene coherence.
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Interoperability with Web Standards:
Alignment with W3C XPointer and XPath standards allows seamless integration with XML technologies and existing web environments, promoting cross-platform multimedia interoperability.
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Secure Scene Modification:
Security attributes in update mechanisms allow control over allowed modifications, maintaining integrity and trust in multimedia presentations.
Related Standards
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ISO/IEC 14496 (MPEG-4 Part 20):
The parent standard covering LASeR and SAF foundational technologies for lightweight scene representation and aggregation.
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W3C XPointer Framework:
A recommendation that defines standardized pointer syntax for addressing parts of XML documents, used in PMSI for referencing structured information fragments.
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W3C XML Path Language (XPath) Version 1.0:
Provides query language capabilities utilized within the mpeg-pmsi() scheme to locate and manipulate XML nodes precisely.
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SVG 1.1 Specification:
Scalable Vector Graphics standard referenced for utilizing editable text elements (tref) within multimedia scenes.
This amendment of ISO/IEC 14496-20 integrates advanced presentation and modification features, promoting efficient, interoperable, and secure handling of structured information within audio-visual objects. Its implementation empowers multimedia developers and providers to create rich, adaptable content experiences suitable for evolving digital ecosystems.
Open preview (PDF)Information technology — Coding of audio-visual objects — Part 20: Lightweight Application Scene Representation (LASeR) and Simple Aggregation Format (SAF) — Amendment 3: Presentation and Modification of Structured Information (PMSI)