This secion is informative.
A digital STB is the end-user device for Interactive Television (iTV). The
key design consideration for STBs is low-cost. Hence, these devices are quite
restricted in terms of their hardware configuration (similar to a PDA). The
current characteristics of a typical configuration are: (1) low-power CPU,
(2) small amount of flash memory, (3) dedicated hardware audio/video decoder
(MPEG-2 or MPEG-4 H.264), and (4) infra-red remote control interface.
The most imporant service provided by a STB is the audio-visual content,
which typically is encoded using MPEG-2 or MPEG-4 (H.264). Two other major
services are the Electronic Program Guide (EPG), that provides information
about the TV schedule, and the Super Teletext, an enhanced version of the
teletext service.
Because only the manufacturer has access to the STB native environment,
interactive STBs include an interoperable middleware for third-party
development: MHP in Europe, ACAP in USA, and ARIB in Japan. These standardized
solutions are composed of a procedural environment (based on Java in MHP and
ACAP, and on ECMAScript in ARIB) and a declarative environment (based on
XHTML, CSS, and TV specific extensions to DOM).
Relationship between iTV Standards.
The previous mentioned standards provide a text-centric solution to a
media-centric problem. Thus, because of the multimedia nature of television,
incorporating SMIL capabilities in a STB provides a number of interactive
services that can be synchronized with the broadcasted audio-visual
material.
The declarative solutions included in current iTV standards (e.g., XHTML +
CSS + scripts, HTML + Java, and XHTML + C) impose a number of technological
problems. The major technological problem is that they require the use of
scripting for synchronizing XML-based applications with the audio-visual
content (e.g., an script is activated, when a broadcast event is recognized).
Here, we argue that a standard such as SMIL simplifies the task of service
developers by providing a complete declarative solution for synchronization.
In addition, the combinations currently in use (e.g., XHTML + CSS) is
suitable for text-based information such as web pages. Unfortunately, the use
of text in the television environment, apart from subtitles and captions, is
not recommended (e.g., viewing distance requires of large fonts, so the
actual screen space does not allow to render much text). Hence, a
media-centric standard such as SMIL, in which media objects (audio, images,
and video) can be synchronized is highly desirable.
Other major advantage of incorporating SMIL into the interactive
television devices middleware is the simplicity for broadcasters to produce
playlists (schedule of programs). This simplicity might be desirable for the
users, as well, because they can create their own playlist with
user-generated material and, probably, share it with other users.
Other technologies that would fit the television model include Java, MPEG-4,
and Flash. Java is already supported in current STB, but developers should
have a deep knowledge about programming languages (e.g., synchronizing a
video using JMF and some text is a non-trivial task involving the knowledge
of threading) and the STB environemt, or have to adquire expensive authoring
tools. Once again, a declarative approach hides the problems of "how to solve
the problem" simplifying the development of services. Second, the primary
problems of MPEG-4 BIFS are that it is not a one-to-one sintax language and
that it is not possible for one scene to refer to other scene and being
exhibit in parallel. Finally, Flash is, nowadays, a very popular technology
used for multimedia content in the web. Still, being a proprietary
technology, it might not be suited for STB manufacturers and the broadcast
community. In addition, Flash is a non-structured technology, uses scripting,
and dynamic modifications to a presentation are difficult to manage.
There are basic requirements that the STB Profile should take into
account:
- Support for opacity and alpha channel at the region level.
- Support for transitions.
- Support for remote control-like functionality.
- Support for three different rendering layers: background, video, and
graphics.
iTV three different Planes.
STB environment differs from desktops and mobile terminals. Thus, the STB
Profile takes into account current hardware/software restrictions, which are
considered as minimal capabilities for a terminal implementing the STB Profile:
- Television display (layout): it is composed of
three different layers, ordered from back to front:
- The background layer is an image or a fill color.
- The video layer is hardware decoded (MPEG-2 or MPEG-4 Part 10 H.264/AVC) and can be resized and
relocated (e.g., 1/4 of the screen).
- The graphics layer renders applications using alpha channel.
- User Input (accesskey): remote control with a limited
number of keys.
- Video Stream Events (events): events related to the
video stream (e.g., staring of a commercial) should be supported.
- Hardware Configuration:
- Flash memory: around 8MB-32MB
- RAM: at least 64MB
- CPU: at least 250MIPs
- Return Channel: POTS modem, ethernet (depending on the configuration).
- Hard disk: for PVR devices (depending on the configuration).
- Video formats: SD MPEG-2, HD-MPEG-2, and SD/HD MPEG-4 Part 10 H.264/AVC (depending on the configuration)
- Audio-Visual Broadcasted Content Access (restrictions to the data
source): the video stream should be accesible from the SMIL presentation
(e.g., dvb:// URI).
The STB Profile is intended for the following scenarios:
- Stand-alone
- Partial-synchronized broadcast content
- Enhanced broadcast contet
The stand-alone scenario only needs a SMIL player installed in the STB. It
is the most simple scenario because it does not take into account the actual
synchronization of the presentation with the broadcasted audio-visual
content. The partial-synchronized broadcast content scenario is intended for
applications such as the Super Teletext and EPG. In this case, such
applications can include multimedia elements. The SMIL presentation does not
need to be synchronized with the audio-visual content, but only fetchs
textual information (e.g., latest news and TV shcedule). Finally, the
enhanced broadcast contet scenario the SMIL presentation is actually
synchonized with the audio-visual content. The following list discusses the
scenarios in more detail.
- Stand-alone: first, the user has access to multiple multimedia items
from different sources such as stored content in his STB and/or return
channel capabilities. SMIL language is used as a container for that
multimedia content, in which interactive elements can be included (e.g.,
links, buttons). The user starts the SMIL STB Profile compatible player.
The presentation is visualized in the TV screen and the user can interact
using the remote control. One example that fits this scenario is a photo
show created from the stored pictures in a digital camera. Other example
is a simple game.
- Partial-Synchronized (Multimedia Teletext and EPG): the player needs to
access text-based information (e.g., TV content schedule, latest news)
that is broadcasted or stored in an external web server. In this case, it
is not necessary that the presentation is synchronized with the
audio-visual content. In addition to the broadcasted text-based
information, the presentation can include multimedia information such as
the last speech of a famous polititian.
- Enhanced Broadcast Content: in this scenario, applications synchronized
with the broadcast audio-visual content are delivered using the STB
Profile. Thus, the SMIL player can run enhanced functionality over the
typical video. Some examples include subtitles/captions, animated statics
about a football player, or the comments of the coach before a football
match.
Two SMIL iTV Services: (left) Interactive Content and
(right) Multimedia Teletext.
This section is normative.
This version of SMIL provides a definition of strictly conforming STB
Profile documents, which are restricted to tags and attributes from the SMIL
namespace. In the future, the language described in this profile may be
extended by other W3C Recommendations, or by private extensions. For these
extensions, the following rules must be obeyed:
- All elements introduced in extensions must have a skip-content attribute if it
should be possible that their content is processed by STB
Profile user agents.
- Private extensions must be introduced by defining a new XML
namespace.
Conformant STB Profile user agents are expected to handle
documents containing extensions that obey these two rules.
The STB Profile is a conforming SMIL specification. The rules for defining
conformant documents are provided in the SMIL
Language Conformance in the SMIL
Language Profile document. Note that while the referenced section is
written for the SMIL Language Profile, all of the rules apply to the STB
Profile as well, with the exception that the STB Profile's namespace should be used instead of
the SMIL Language Profile's namespace.
Documents written for the STB Profile must declare a default namespace for
its elements with an
xmlns attribute on
the smil root element
with its identifier URI:
<smil xmlns="http://www.w3.org/2006/SMIL30/STB">
...
</smil>
The default namespace declaration must be
xmlns="http://www.w3.org/2006/SMIL30/STB"
Language designers and implementors wishing to extend the STB Profile must
consider the implications of the use of namespace extension syntax. Please
consult the section on Scalable
Profiles for restrictions and recommendations for best practice when
extending SMIL.
STB Profile DOCTYPE declaration
A SMIL 3.0 document can contain the following DOCTYPE declaration:
<!DOCTYPE smil PUBLIC "-//W3C//DTD SMIL 3.0//EN"
"http://www.w3.org/2006/SMIL30/SMIL30.dtd">
The SMIL STB Profile DOCTYPE is:
<!DOCTYPE smil PUBLIC "-//W3C//DTD SMIL STB//EN"
"http://www.w3.org/2006/SMIL30/SMILSTB.dtd">
If a document contains this declaration, it must be a valid XML
document.
Note that this implies that extensions to the syntax defined in the DTD are
not allowed. If the document is invalid, the user agent should issue an
error.
Since the STB Profile defines a conforming SMIL document, the rules for
defining conformant user agents are the same as provided in the
Conforming
SMIL Language User Agents in the
SMIL
Language Profile document, with the exception that the conforming user
agent must support the
STB Profile
namespace instead of the SMIL Language Profile namespace.
The STB Profile supports the multimedia document features appropriate for
STB platforms. It uses only modules from the SMIL
recommendation. As the language profile includes the mandatory modules, it is
a SMIL
Host Language conforming language profile.
The STB Profile includes the following SMIL modules:
The collection names contained in the following table define the STB
Profile vocabulary.
| STB Profile |
| Collection Name |
Elements in Collection |
| Animation |
animate,
set, animateMotion, animateColor |
| ContentControl |
switch, prefetch, customTest, customAttributes |
| Layout |
region, root-layout,
layout, regPoint, topLayout |
| LinkAnchor |
a,
area, [anchor] |
| MediaContent |
text,
img,
audio,
video,
ref,
animation,
textstream,
brush,
param,
paramGroup |
| Metainformation |
meta,
metadata |
| Structure |
smil,
head,
body |
| Schedule |
par,
seq,
excl |
| Transition |
transition |
| SMILText |
smilText,
br,
span,
textStyle,
textStyling |
| State |
|
In the following sections, we define the set of elements and attributes
used in each of the modules included in the STB Profile. The content model
for each element is described. The content model of an element is a
description of elements which can appear as its direct children. The special
content model "EMPTY" means that a given element may not have children.
The id, class and title attributes in the collection Core are
defined for all the elements of the STB Profile. The id attribute is used in the STB Profile to
assign a unique XML identifier to every element in a SMIL document. In this
document, equivalent but deprecated attributes and elements are shown in
square brackets.
The Animation
Module provides a framework for incorporating animation into a timing
framework, and a mechanism for composing the effects of multiple animations.
The Animation Module uses the timing modules included in this profile for the
underlying model of time. The STB Profile includes the Animation
functionality of the BasicAnimation
module. The BasicAnimation
Module defines the semantics for the animate, set, animateMotion and animateColor elements.
In the STB Profile, Animation elements can have the following attributes
and content model :
| Animation Module |
| Elements |
Attributes |
Content model |
| animate |
Core, I18n,
Timing, Test,
attributeName, attributeType, targetElement, from, to, by, values, calcMode, accumulate, additive, skip-content, fill (freeze | remove | hold | auto |
default) |
EMPTY |
| set |
Core, I18n,
Timing, Test,
attributeName, attributeType, targetElement, to, skip-content, fill (freeze | remove | hold | auto |
default) |
EMPTY |
| animateMotion |
Core, I18n,
Timing, Test,
targetElement, origin, from, to, by, values, calcMode, accumulate, additive, skip-content, fill (freeze | remove | hold | auto |
default) |
EMPTY |
| animateColor |
Core, I18n,
Timing, Test,
attributeName, attributeType, targetElement, from, to, by, values, calcMode, accumulate, additive, skip-content, fill (freeze | remove | hold | auto |
default) |
EMPTY |
This profile adds the animate,
set, animateMotion and animateColor elements to the content
model of the par, seq, and excl elements of the Timing
and Synchronization Modules. It also adds these elements to the content
model of the body element of the Structure
Module.
Specifying the target element of the animation
The animation target elements supported in the STB Profile are
the region element defined in the Layout
Modules, the area [anchor] element defined in the Linking
Modules and the text, img, audio, animation, video, ref, textstream and the brush elements defined in the Media
Objects modules.
The STB Profile uses the targetElement attribute to identify
the element to be affected by animation elements. As recommended in the BasicAnimation
Module when the targetElement attribute is
supported, this profile excludes the XLink attributes href, type, actuate and show from the animate, set, animateMotion and animateColor elements.
Specifying the target attribute of the animation
The target attributes of the animations are a subset of those of the region, area [anchor], and media elements. The animatable
attributes of the region, area [anchor], and media elements are listed in
the table below.
The area [anchor] element has the coords attribute which can be subject to
animation. The attribute coords is
considered of type string in this profile. This means that only discrete
non-additive animation is supported on this attribute.
Media elements have the following region attributes which can be subject
to animation: left, right, top, bottom, width, height, z-index and backgroundColor [background-color].
| Elements |
Target Element |
Target Attributes |
| animate |
region |
soundLevel, left, right, top, bottom, width, height, z-index, backgroundColor [background-color], regionName |
| area [anchor] |
coords(string) |
| text, img, audio, animation, video, ref, textstream |
left, right, top, bottom, width, height, z-index, backgroundColor [background-color] |
| brush |
left, right, top, bottom, width, height, z-index, backgroundColor [background-color], color |
| set |
region |
soundAlign, soundLevel, left, right, top, bottom, width, height, z-index, backgroundColor [background-color], regionName |
| area [anchor] |
coords(string) |
| text, img, audio, animation, video, ref, textstream |
left, right, top, bottom, width, height, z-index, backgroundColor [background-color] |
| brush |
left, right, top, bottom, width, height, z-index, color |
| animateMotion |
region |
Animates the top and left attributes of the region. |
| text, img, audio, animation, video, ref, textstream |
Animates the top and left attributes of the sub-region
associated with the media element. |
| animateColor |
region |
backgroundColor
[background-color] |
| text, img, audio, animation, video, ref, textstream |
backgroundColor
[background-color] |
| brush |
color |
Integration definitions
The STB Profile defines a set of integration definitions as
required by the Animation modules. These definitions are:
The Content
Control Modules provide a framework for selecting content based on a set
of test attributes. The Content
Control Modules define semantics for the switch and prefetch elements. The STB
Profile includes the Content Control functionality of the BasicContentControl,
PrefetchControl
and SkipContentControl
modules.
In the STB Profile, Content Control elements can have the
following attributes and content model :
| Content Control Module |
| Elements |
Attributes |
Content model |
| switch |
Core, I18n,
Test |
((Schedule | MediaContent | ContentControl | LinkAnchor |
Animation)* | (layout )*) |
| prefetch |
Core, I18n,
Test, Timing,
mediaSize, mediaTime, bandwidth, src, skip-content, clipBegin, clipEnd |
EMPTY |
| customTest |
|
EMPTY |
| customAttributes |
|
EMPTY |
This profile adds the switch
element to the content model of the par,
seq and excl elements of the Timing
and Synchronization Modules, of the body and the head elements of the Structure
Module, of the content model of the a
element of the Linking
Modules.
Content Control functionality is used to define the attribute set
"Test":
| Collection Name |
Attributes in Collection |
| Test |
systemBitrate
[system-bitrate], systemCaptions
[system-captions], systemLanguage
[system-language], system-overdub-or-caption,
systemRequired
[system-required], systemScreenSize
[system-screen-size],systemScreenDepth
[system-screen-depth], systemOverdubOrSubtitle,
systemAudioDesc,
systemOperatingSystem,
systemCPU, systemComponent |
The Test attributes collection is added to all the elements defined in the
STB Profile. A STB user agent must support all of
the values for the systemOperatingSystem and
systemCPU attributes listed in the
Content Control Modules. In addition, the user agent should accept namespaced
values as future extensions, and not declare a syntax error. The user agent
should return false for unrecognized values of the systemOperatingSystem and
systemCPU attributes.
The Layout
Modules provide a framework for spatial layout of visual components. The
Layout
Modules define semantics for the region, root-layout, layout and the regPoint elements. The STB
Profile includes the Layout functionality of the BasicLayout,
AudioLayout,
SubRegionLayout,
BackgroundTilingLayout,
AlignmentLayout,
OverrideLayout
modules.
In the STB Profile, Layout elements can have the following
attributes and content model :
| Layout Module |
| Elements |
Attributes |
Content model |
| region |
Core, I18n,
Test, backgroundColor [background-color], backgroundImage, backgroundRepeat, bottom, fit (fill |
hidden | meet | meetBest | scroll | slice), height, left, mediaAlign, regAlign, regionName, regPoint, right, showBackground (always | whenActive), skip-content, soundAlign, soundLevel, top, width, z-index |
region* |
| root-layout |
Core, I18n,
Test, backgroundColor [background-color], backgroundImage, backgroundRepeat, width, height, skip-content |
EMPTY |
| layout |
Core, I18n,
Test, type |
(root-layout | region | regPoint)* |
| regPoint |
Core, I18n,
Test, top, bottom, left, right, regAlign ( topLeft|topMid | topRight | midLeft | center |
midRight | bottomLeft | bottomMid | bottomRight ), skip-content |
EMPTY |
| topLayout |
|
EMPTY |
The attribute collection SubregionAttributes is defined as follows:
| Collection Name |
Attributes in Collection |
| SubregionAttributes |
top, left, bottom, right, width, height, z-index, fit, backgroundColor
[background-color],
mediaAlign, regPoint, regAlign, soundAlign, soundLevel |
This profile adds the layout
element to the content model of the head element of the Structure
Module. It also adds this element to the content model of the switch element of the Content
Control Modules, when the switch
element is a child of the head element.
The profile also adds the following a
The Linking
Modules provide a framework for relating documents to content, documents
and document fragments. The Linking
Modules define semantics for the a and
area [anchor] elements. They define also the
semantics of a set of attributes defined for these elements. The STB
Profile includes the Linking functionality of the BasicLinking
and LinkingAttributes
modules.
Both the a and area [anchor] elements have an href attribute, whose value must be a valid
URI.
Support for URIs with XPointer fragment identifier syntax is not
required.
In the STB Profile, Linking elements can have the following
attributes and content model :
| Linking Module |
| Elements |
Attributes |
Content model |
| a |
Core, I18n,
Timing, Test,
href, sourceLevel, destinationLevel, sourcePlaystate (play |
pause | stop) 'pause', destinationPlaystate
(play | pause) 'play', show
(new | replace | pause) 'replace', accesskey, tabindex, target, external, actuate |
(Schedule | MediaContent | ContentControl | Animation )* |
| area [anchor] |
Core, I18n,
Timing, Test,
shape, coords, href, nohref, sourceLevel, destinationLevel, sourcePlaystate, destinationPlaystate,
show, accesskey, tabindex, target, external, actuate, shape, fragment, skip-content |
(animate | set)* |
This profile adds the a element to the
content model of the par, seq, and excl elements of the Timing
and Synchronization Modules. It also adds these elements to the content
model of the body element of the Structure
Module.
In the STB Profile, a value of onLoad set on the attribute actuate indicates that the link is
automatically traversed when the linking element becomes active. For linking
elements containing SMIL timing, this is when the active duration of the
linking element begins.
Linking behavior in the STB Profile may be used to navigate
within a document or to link across documents. When linking to destinations
outside the current document, implementations may ignore the values "play" and "pause" of the
sourcePlaystate attribute,
and the values "new" and "pause" of the show attribute; in these cases, the semantics
of the "stop" attribute (for sourcePlaystate ) and the "replace" attribute (for show) should be used. If an implementation
ignores the values of the sourcePlaystate and show attributes, it may also ignore the sourceLevel attribute.
The attribute tabindex specifies
the position of the element in the tabbing order at a particular instant for
the current document. The tabbing order defines the order in which elements
will receive focus when navigated by the user via an input device such as a
keyboard. At any particular point in time, only active elements are taken
into account for the tabbing order; inactive elements are ignored.
When a media object element has a tabindex attribute and becomes active,
then its ordered tab index is inserted in the SMIL tab index at the location
specified by the media object's tabindex attribute value. This assumes
that the media object itself has tab indices, such as embedded HTML with
tabindex attributes. This enables
all link starting points in a SMIL presentation to have a place on the
ordered list to be tab-keyed through, including those in embedded
presentations.
The STB Profile does not define four-way navigation in the current release.
A definition for four-way navigation is expected in the
future version of SMIL.
The Media
Object Modules provide a framework for declaring media. The Media
Object Modules define semantics for the ref, animation, audio, img, video, text, textstream, param, paramGroup and brushbrush elements. The STB
Profile includes the Media Object functionality of the BasicMedia,
MediaClipping,
MediaParam,
BrushMedia
and MediaAccessibility
modules.
In the STB Profile, media elements can have the following
attributes and content model:
| Media Object Module |
| Elements |
Attributes |
Content model |
| text, img, audio, animation, video, ref, textstream |
Core, I18n,
Timing, Test,
SubregionAttributes, region, fill (freeze | remove | hold |
transition | auto | default), author, copyright, abstract, src, type, erase, mediaRepeat, paramGroup, sensitivity, tabindex, transIn, transOut, clipBegin [clip-begin], clipEnd [clip-end], readIndex, endsync. |
(param | area [anchor] | switch | Animation)* |
| brush |
Core, I18n,
Timing, Test,
SubregionAttributes, abstract, region, fill (freeze | remove | hold |
transition | auto | default), author, copyright, color, skip-content, erase, sensitivity, tabindex, transIn, transOut, readIndex, endsync. |
(param | area [anchor]| switch | Animation)* |
| param |
Core, I18n,
Test, name, value, valuetype (data | ref |
object), type, skip-content |
EMPTY |
| paramGroup |
Core, I18n,
Test, skip-content |
(param)* |
This profile adds the ref, animation, audio, img, video, text, textstream and brush elements to the content model of the
par, seq, and excl elements of the Timing
and Synchronization Modules and also adds these elements to the content
model of the body element of the Structure
Module. It also adds these elements to the content model of the a element of the Linking
Modules. Lastly, this profile adds the paramGroup element to the region element of the Layout
Modules.
The following elements are allowed as children of a media object
reference: anchor, area [anchor], param, animate, set, animateColor, animateMotion. The a element is not included in this list.
The switch element is allowed, with
the restriction that in this case the content of the switch may only be from
the same set of elements as is listed above.
This section is informative.
The members of the W3C SYMM Working Group recommend that at least the
following content types and file formats be supported by STB user agents:
- For plain text: plain text with US-ASCII ([ASCII]) or UTF-8
([UTF8]) encoding, MIME type is text/plain.
- for still image: ISO/IEC JPEG ([JPEG]) together with JFIF ([JFIF]),
baseline DCT, non-differential, Huffman coding, as defined in table B.1,
symbol 'SOF0' in [JPEG], MIME type is image/jpeg.
- For bitmap graphics: PNG, MIME type is image/png ([PNG-MIME],
[PNG-REC]).
- For 2D vector graphics: SVG 1.1 Tiny Profile ([SVG-Mobile]), MIME
type is image/svg+xml.
- For video: ITU-T Recommendation H.263 [H263] profile 0 level 10, part
of 3GP file format.
- For audio: MPEG-4 AAC Low Complexity object type [AAC], part of 3GP
file format.
- The file format for audio and for video: the 3GP file format as defined
in [3GPP26.234R5].
This section is normative.
The MediaParam module defines the erase
attribute, and defers definition of the "display area" to the language
profile. "Display area" for the purposes of the STB Profile
corresponds to a SMIL BasicLayout region. The effects of erase="never"
apply after the active duration of the media object and any fill period
(defined by SMIL Timing and Synchronization), and only until other media
plays to the region targeted by the media object, or until the same media
object restarts.
The Metainformation
Module provides a framework for describing a document, either to inform
the human user or to assist in automation. The Metainformation
Module defines semantics for the meta and metadata elements. The STB
Profile includes the Metainformation functionality of the Metainformation
module.
In the STB Profile, Metainformation elements can have the
following attributes and content model :
This profile adds the meta element
to the content model of the head
element of the Structure
Module.
The content model of metadata is empty. Profiles that extend the STB
Profile may define the RDF (Resource Description Framework) schema to
be used in extending the content model of the metadata element. The Resource
Description Framework is defined in the W3C RDF Recommendation
[RDFsyntax].
The Structure Module provides a framework for structuring a SMIL document.
The Structure Module defines semantics for the smil, head, and body elements. The STB Profile
includes the Structure functionality of the Structure
module.
In the STB Profile, the Structure elements can have the
following attributes and content model :
| Structure Module |
| Elements |
Attributes |
Content model |
| smil |
Core, I18n,
Test, xmlns |
(head?,body?) |
| head |
Core, I18n |
(meta*,(metadata,meta*)?,((layout|switch),meta*)?, (transition+,meta*)?, (paramGroup+,meta*)?) |
| body |
Core, I18n,
Timing, fill, abstract, author, copyright |
(Schedule | MediaContent | ContentControl | a )* |
The body element acts as the root
element to span the timing tree. The body element has the behavior of a seq element. Timing on the body element is supported. The syncbase of
the body element is the application
begin time, which is implementation dependent, as is the application end
time. Note that the effect of fill on
the body element is between the end of
the presentation and the application end time, and therefore the effect of
fill is implementation dependent.
The Timing
and Synchronization Modules provide a framework for describing timing
structure, timing control properties and temporal relationships between
elements. The Timing
and Synchronization Modules define semantics for par, seq
and excl elements. In addition, these
modules define semantics for attributes including begin, dur, end,
repeat (deprecated), repeatCount, repeatDur, min, max. The
STB Profile includes the Timing and Synchronization functionality
of the BasicInlineTiming,
EventTiming, MinMaxTiming, RepeatTiming, MultiArcTiming, AccessKeyTiming,
BasicTimeContainers, BasicExclTimeContainers modules.
In the STB Profile, Timing and Synchronization elements can
have the following attributes and content model :
| Timing and Synchronization Module |
| Elements |
Attributes |
Content model |
| par |
Core, I18n,
Timing, Test,
endsync, fill (freeze | remove | hold | auto |
default), abstract, author, copyright, region |
(Schedule | MediaContent | ContentControl | |