ISO/IEC 14496-20:2006
(Main)Information technology — Coding of audio-visual objects — Part 20: Lightweight Application Scene Representation (LASeR) and Simple Aggregation Format (SAF)
Information technology — Coding of audio-visual objects — Part 20: Lightweight Application Scene Representation (LASeR) and Simple Aggregation Format (SAF)
ISO/IEC 14496-20:2006 defines a scene description format (LASeR) and an aggregation format (SAF) suitable for representing and delivering rich-media services to resource-constrained devices such as mobile phones. A rich media service is a dynamic, interactive collection of multimedia data such as audio, video, graphics, and text. Services range from movies enriched with vector graphic overlays and interactivity (possibly enhanced with closed captions) to complex multi-step services with fluid interaction and different media types at each step. LASeR aims at fulfilling all the requirements of rich-media services at the scene description level. LASeR supports: an optimized set of objects inherited from SVG to describe rich-media scenes; a small set of key compatible extensions over SVG; the ability to encode and transmit a LASeR stream and then reconstruct SVG content; dynamic updating of the scene to achieve a reactive, smooth and continuous service; simple yet efficient compression to improve delivery and parsing times, as well as storage size, one of the design goals being to allow both for a direct implementation of the SDL as documented, as well as for a decoder compliant with ISO/IEC 23001-1 to decode the LASeR bitstream; an efficient interface with audio and visual streams with frame-accurate synchronization; use of any font format, including the OpenType industry standard; and easy conversion from other popular rich-media formats in order to leverage existing content and developer communities.
Technologies de l'information — Codage des objets audiovisuels — Partie 20: Représentation de scène d'application allégée (LASeR) et format d'agrégation simple (SAF)
General Information
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Standards Content (Sample)
INTERNATIONAL ISO/IEC
STANDARD 14496-20
First edition
2006-06-15
Information technology — Coding
of audio-visual objects —
Part 20:
Lightweight Application Scene
Representation (LASeR) and Simple
Aggregation Format (SAF)
Technologies de l'information — Codage des objets audiovisuels —
Partie 20: Représentation de scène d'application allégée (LASeR) et
format d'agrégation simple (SAF)
Reference number
ISO/IEC 14496-20:2006(E)
©
ISO/IEC 2006
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ISO/IEC 14496-20:2005(E)
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ISO/IEC 14496-20:2006(E)
Contents Page
Foreword. v
Introduction . vii
1 Scope. 1
2 Normative References. 2
3 Terms, definitions and abbreviations. 3
3.1 Terms and definitions. 3
3.2 Abbreviations . 3
4 Document Conventions. 3
5 Architecture. 4
6 Scene Representation. 4
6.1 Overview. 4
6.2 Relationship with SVG. 5
6.3 Timing Model. 7
6.4 Execution Model . 8
6.5 Supported Events . 9
6.6 Encoder Configuration. 10
6.7 LASeR Scene Commands. 13
6.8 Scene Description Elements. 22
7 Simple Aggregation Format (SAF). 34
7.1 Overview. 34
7.2 Time and terminal model specification . 35
7.3 SAF Packet. 35
7.4 SAF Packet Header. 37
7.5 SAF Access Unit. 37
7.6 SimpleDecoderConfigDescriptor . 38
7.7 SimpleDecoderSpecificInfo. 39
7.8 RemoteStreamHeader. 39
7.9 Cache Unit. 40
7.10 EndOfStream. 41
7.11 EndOfSAFSession. 41
8 Profiles. 41
8.1 Overview. 41
8.2 LASeR mini. 41
8.3 LASeR full. 43
9 Compatibility of SAF Packet. 44
10 Carriage of LASeR and SAF . 45
10.1 Storage of LASeR in MP4 files . 45
10.2 Carriage of SAF Streams over HTTP . 47
10.3 Carriage of SAF Streams over RTP. 47
10.4 Carriage of SAF Streams over MPEG-2 Systems. 47
11 Electronic Attachments. 47
12 Binary Syntax for the LASeR Encoding . 48
12.1 Decoding Process. 48
12.2 Binary Syntax. 63
13 Usage of ISO/IEC 23001-1 . 132
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ISO/IEC 14496-20:2006(E)
13.1 Introduction . 132
13.2 Electronic Attachments. 132
13.3 Type Codecs. 132
13.4 Type codecs for use with ISO/IEC 23001-1 decoders . 134
13.5 DecoderInit. 137
13.6 Decoding Process. 137
Annex A (informative) Patent statements . 141
Bibliography . 142
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ISO/IEC 14496-20:2006(E)
Foreword
ISO (the International Organization for Standardization) and IEC (the International Electrotechnical
Commission) form the specialized system for worldwide standardization. National bodies that are members of
ISO or IEC participate in the development of International Standards through technical committees
established by the respective organization to deal with particular fields of technical activity. ISO and IEC
technical committees collaborate in fields of mutual interest. Other international organizations, governmental
and non-governmental, in liaison with ISO and IEC, also take part in the work. In the field of information
technology, ISO and IEC have established a joint technical committee, ISO/IEC JTC 1.
International Standards are drafted in accordance with the rules given in the ISO/IEC Directives, Part 2.
The main task of the joint technical committee is to prepare International Standards. Draft International
Standards adopted by the joint technical committee are circulated to national bodies for voting. Publication as
an International Standard requires approval by at least 75 % of the national bodies casting a vote.
ISO/IEC 14496-20 was prepared by Joint Technical Committee ISO/IEC JTC 1, Information technology,
Subcommittee SC 29, Coding of audio, picture, multimedia and hypermedia information.
ISO/IEC 14496 consists of the following parts, under the general title Information technology — Coding of
audio-visual objects:
⎯ Part 1: Systems
⎯ Part 2: Visual
⎯ Part 3: Audio
⎯ Part 4: Conformance testing
⎯ Part 5: Reference software
⎯ Part 6: Delivery Multimedia Integration Framework (DMIF)
⎯ Part 7: Optimized reference software for coding of audio-visual objects [Technical Report]
⎯ Part 8: Carriage of ISO/IEC 14496 contents over IP networks
⎯ Part 9: Reference hardware description [Technical Report]
⎯ Part 10: Advanced Video Coding
⎯ Part 11: Scene description and application engine
⎯ Part 12: ISO base media file format
⎯ Part 13: Intellectual Property Management and Protection (IPMP) extensions
⎯ Part 14: MP4 file format
⎯ Part 15: Advanced Video Coding (AVC) file format
⎯ Part 16: Animation Framework eXtension (AFX)
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ISO/IEC 14496-20:2006(E)
⎯ Part 17: Streaming text format
⎯ Part 18: Font compression and streaming
⎯ Part 19: Synthesized texture stream
⎯ Part 20: Lightweight Application Scene Representation (LASeR) and Simple Aggregation Format (SAF)
⎯ Part 21: MPEG-J GFX
⎯ Part 22: Open Font Format
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ISO/IEC 14496-20:2006(E)
Introduction
ISO/IEC 14496-20 specifies syntax and semantics for:
— The Lightweight Application Scene Representation (LASeR), specified in Clause 6, which is a binary
format for encoding 2D scenes and updates of scenes. The binary format and the scene representation
(based on SVG Tiny), are both designed to be suitable for lightweight embedded devices such as mobile
phones.
— A Simple Aggregation Format (SAF), specified in Clause 7, to efficiently and easily transport LASeR data
together with audio and/or video content over various delivery channels. This multiplexing scheme is
designed to be simple to implement and to allow efficient demultiplexing on low-end devices.
The International Organization for Standardization (ISO) and International Electrotechnical Commission (IEC)
draw attention to the fact that it is claimed that compliance with this document may involve the use of a patent.
The ISO and IEC take no position concerning the evidence, validity and scope of this patent right.
The holder of this patent right has assured the ISO and IEC that he is willing to negotiate licences under
reasonable and non-discriminatory terms and conditions with applicants throughout the world. In this respect,
the statement of the holder of this patent right is registered with the ISO and IEC. Information may be obtained
from the companies listed in Annex A.
Attention is drawn to the possibility that some of the elements of this document may be the subject of patent
rights other than those identified in Annex A. ISO and IEC shall not be held responsible for identifying any or
all such patent rights.
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INTERNATIONAL STANDARD ISO/IEC 14496-20:2006(E)
Information technology — Coding of audio-visual objects —
Part 20:
Lightweight Application Scene Representation (LASeR)
and Simple Aggregation Format (SAF)
1 Scope
This International Standard defines a scene description format (LASeR) and an aggregation format (SAF)
respectively suitable for representing and delivering rich-media services to resource-constrained devices such
as mobile phones.
LASeR aims at fulfilling all the requirements of rich-media services at the scene description level. LASeR
supports:
⎯ an optimized set of objects inherited from SVG to describe rich-media scenes;
⎯ a small set of key compatible extensions over SVG;
⎯ the ability to encode and transmit a LASeR stream and then reconstruct SVG content;
⎯ dynamic updating of the scene to achieve a reactive, smooth and continuous service;
⎯ simple yet efficient compression to improve delivery and parsing times, as well as storage size, one of the
design goals being to allow both for a direct implementation of the SDL as documented, as well as for a
decoder compliant with ISO/IEC 23001-1 to decode the LASeR bitstream;
⎯ an efficient interface with audio and visual streams with frame-accurate synchronization;
⎯ use of any font format, including the OpenType industry standard; and
⎯ easy conversion from other popular rich-media formats in order to leverage existing content and
developer communities.
Technology selection criteria for LASeR included compression efficiency, but also code and memory footprint
and performance. Other aims included: scalability, adaptability to the user context, extensibility of the format,
ability to define small profiles, feasibility of a J2ME implementation, error resilience and safety of
implementations.
SAF aims at fulfilling all the requirements of rich-media services at the interface between media/scene
description and existing transport protocols:
⎯ simple aggregation of any type of stream;
⎯ signaling of MPEG and non-MPEG streams;
⎯ optimized packet headers for bandwidth-limited networks;
⎯ easy mapping to popular streaming formats;
⎯ cache management capability; and
⎯ extensibility.
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SAF has been designed to complement LASeR for simple, interactive services, bringing:
⎯ efficient and dynamic packaging to cope with high latency networks;
⎯ media interleaving; and
⎯ synchronization support with a very low overhead.
This International Standard defines the usage of SAF for LASeR content. However, LASeR can be used
independently from SAF.
2 Normative References
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
ISO/IEC 13818-1, Information technology — Generic coding of moving pictures and associated audio
information — Part 1:Systems
ISO/IEC 14496-1, Information technology — Coding of audio-visual objects — Part 1: Systems
ISO/IEC 14496-12, Information technology — Coding of audio-visual objects — Part 12: ISO base media file
format
ISO/IEC 14496-18, Information technology — Coding of audio-visual objects — Part 18: Font compression
and streaming
RFC 2045, Multipurpose Internet Mail Extensions (MIME) Part one: Format of Internet message bodies,
http://www.ietf.org/rfc/rfc2045.txt
RFC 2326, Real Time Streaming Protocol, http://www.ietf.org/rfc/rfc2326.txt
RFC 2965, HTTP State Management Mechanism, http://www.ietf.org/rfc/rfc2965.txt
W3C SVG11, Scalable Vector Graphics (SVG) 1.1 Specification [Recommendation],
http://www.w3.org/TR/2003/REC-SVG11-20030114/
W3C SMIL2, Synchronized Multimedia Integration Language (SMIL 2.0) — [Second Edition], 07 January 2005.
http://www.w3.org/TR/2005/REC-SMIL2-20050107/
W3C CSS, Cascading Style Sheets, level 2 [Recommendation],
http://www.w3.org/TR/1998/REC-CSS2-19980512/
W3C DOM, Document Object Model Level 2 Events Specification, Version 1.0, W3C Recommendation
13 November, 2000. http://www.w3.org/TR/2000/REC-DOM-Level-2-Events-20001113
W3C, XML, Events, an Events Syntax for XML, W3C Recommandation 14 October 2003.
http://www.w3.org/TR/2003/REC-xml-events-20031014
W3C xml:id Version 1.0, W3C Recommendation 12 July 2005,
http://www.w3.org/TR/2005/PR-xml-id-20050712/
W3C Xlink, XML Linking Language, W3C Recommendation, 27 June 2001.
http://www.w3.org/TR/2001/REC-xlink-20010627/
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ISO/IEC 14496-20:2006(E)
3 Terms, definitions and abbreviations
3.1 Terms and definitions
For the purposes of this document, the following terms and definitions apply.
3.1.1
access unit
individually accessible portion of data within a media stream
NOTE An access unit is the smallest data entity to which timing information can be attributed.
3.1.2
media time line
axis on which times are expressed within the transport or system carrying a LASeR or other stream
3.1.3
normal play time
indicates the stream absolute position relative to the beginning of the presentation
[RFC 2326]
3.1.4
packet
smallest data entity managed by SAF consisting of a header and a payload
3.1.5
scene segment
a set of access units of a LASeR stream, where only the first access unit contains a LASeRHeader
3.1.6
scene time line
axis on which times are expressed within the SVG/LASeR scene, e.g. begin and end
3.2 Abbreviations
CSS Cascading Style Sheets, a W3C standard
SMIL Synchronized Multimedia Integration Language, a W3C standard
SVG Scalable Vector Graphics, a W3C standard
4 Document Conventions
This document uses the following styling conventions for various types of information.
Any name of element, attribute, descriptor or command defined in this specification is styled in bold italic, such
as Add. Any name of element, attribute, descriptor or command defined in another specification is prefixed
with the name of that specification, such as SVG animate or SMIL video.
XML examples use the following style:
version="1.1" baseProfile="tiny">
…
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ISO/IEC 14496-20:2006(E)
SDL descriptions of binary syntax use the following style:
Insert extends LASeRUpdate {
const bit(UpdateBits) InsertCode;
uint(idBits) ref;
The following is the style used for ECMA Script:
function Insert(parentId, field, value) {…
5 Architecture
LaSER is defined in terms of abstract access units, which may be adapted for transmission over a variety of
protocols. LaSER streams may be packaged with some or all of their related media into files of the ISO base
media file format family (e.g. MP4) and delivered over reliable protocols. There is also a simple aggregation
format (SAF), which aggregates a LaSER stream with some or all of its associated media into stream
order. SAF may be delivered over reliable or unreliable protocols. Finally, LASeR streams could be adapted
to other delivery protocols such as RTP [RFC 2326] or MPEG-2 transport [ISO/IEC 13818-1]; however, the
definitions of these mappings is outside the scope of this specification.
Figure 1 presents the LASeR and SAF architecture.
Application
LASeR
SVG Scene Tree
Extensions
Audio Video Image Font …
LASeR
Commands
Binary Encoding
SAF
Transport
Network
Figure 1 — Architecture of LASeR and SAF
6 Scene Representation
6.1 Overview
In this document, a multimedia presentation is a collection of a scene description and media (zero, one or
more). A media is an individual audiovisual content of the following type: image (still picture), video (moving
pictures), audio and by extension, font data. A scene description is constituted of text, graphics, animation,
interactivity and spatial, audio and temporal layout.
A scene description specifies four aspects of a presentation:
⎯ how the scene elements (media or graphics) are organised spatially, e.g. the spatial layout of the
visual elements;
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ISO/IEC 14496-20:2006(E)
⎯ how the scene elements (media or graphics) are organised temporally, i.e. if and how they are
synchronised, when they start or end;
⎯ how to interact with the elements in the scene (media or graphics), e.g. when a user clicks on an
image;
⎯ and if the scene is changing, how the scene changes happen.
A scene description may change by means of animations. The different states of the scene during the whole
animation may be deterministic (i.e. known when the animation starts) or not. The former case is illustrated by
parametric animations. The latter case is illustrated by, for instance, a server sending modification to the
scene on the fly. The sequence of a scene description and its timed modifications is called a scene description
stream.
The scene description format specified herein is called LASeR. A scene description stream is called a LASeR
Stream. Modifications to the scenes are called LASeR Commands. A command is used to act on elements
or attributes of the scene at a given instant in time. LASeR Commands that need to be executed at the same
time are grouped into one LASeR Access Unit (AU).
This specification defines an XML language to describe scenes which can be encoded with the LASeR format
defined throughout subclauses 6.5 to 6.8.37. The exact XML syntax for these elements and attributes is
described in the schemas provided as electronic attachments to this specification.
This specification also defines a binary format to efficiently represent 2D scene descriptions.
6.2 Relationship with SVG
6.2.1 Scene tree
The scene constructs on which the binary format defined in this specification is based are the elements
defined by the W3C in the SVG specification [W3C SVG11] [2]. Subclause 6.8 explicitly refers to the SVG or
SMIL elements and attributes which can be encoded using the binary format defined in this specification. A
LASeR scene is an SVG scene possibly with LASeR extensions. These extensions are also defined in this
subclause. This specification defines in subclause 6.6.2.3 a set of commands, called LASeR Commands,
which can be applied to a LASeR scene.
6.2.2 Fonts
LASeR supports the encoding of fonts. Fonts shall be encoded separately from the scene, e.g. using
ISO/IEC 14496-18, and sent as a media stream together with the scene stream. SVG elements related to font
description are not supported by LASeR.
NOTE 1 to encode SVG scenes with SVG fonts in LASeR, font information shall be extracted from the SVG scene,
encoded separately and sent as a media stream. ISO/IEC 14496-18 is one option to encode and transmit the font, and
more options may be specified in the future.
NOTE 2 when using LASeR to encode an SVG scene which includes SVG Fonts derived from OpenType fonts, a
better quality can be achieved by transmitting the original OpenType fonts.
NOTE 3 care should be taken when extracting font information from an SVG scene that the effective target of
references into the SVG scene, e.g. from scripts, is not changed. One possible way is to replace the extracted font
element with a suitable supported (possibly empty) element.
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ISO/IEC 14496-20:2006(E)
baseProfile="tiny">
d="M1306 412Q1200 412 1123 443T999 ."/>
d="M1250 -30Q1158 -30 1090 206Q1064 ."/>
d="M1011 892L665 144Q537 -129 469 ."/>
d="M802 -61Q520 -61 324 108Q116 ."/>
d="M770 -196Q770 -320 710 -382T528 ."/>
font-size="60" fill="black" stroke="none">
stroke="#888888"/>
AyÖ@ç
Example 1 — SVG scene with embedded font information
baseProfile="tiny">
this was a font
font-size="60" fill="black" stroke="none">
stroke="#888888"/>
AyÖ@ç
Example 2 — LASeR/SAF equivalent of Example 1
(the remainder of this subclause is informative)
Differences between example 1 and 2 are:
⎯ the SVG scene has been wrapped in a NewScene update, then in a SAF layer.
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ISO/IEC 14496-20:2006(E)
⎯ the font description is removed from the SVG scene, encoded with ISO/IEC 14496-18 and placed in
a SAF mediaUnit. The attributes streamType=”12” and objectTypeIndication=”6” in the SAF
mediaHeader with streamID “font” identify the content of the SAF stream.
⎯ the SAF mediaHeader and SAF mediaUnit are connected through the streamID “font”, which is
encoded as a number, and is strictly local to SAF.
⎯ connection between font-family=”TestComic” and the font encoded in the SAF mediaUnit happens
through the font name which is part of the OpenType encoding.
6.3 Timing Model
There are Scene Times, Wallclock Times, SMPTE timecodes, Media Times, and Encoded Scene Times.
Wallclock times and SMPTE timecodes are not affected by the following discussion.
L
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