23. SMIL 3.0 Set-Top Box Profile

This section is normative.

23.6.1 Document Conformance

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.

23.6.2 STB Profile Conformance

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.

STB Profile 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.

Conforming SMIL STB Profile User Agents

23.6.3 The SMIL STB Profile

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:

• Structure functionality
  • Structure Module
• Metainformation functionality
  • Metainformation Module
• Timing functionality
  • BasicInlineTiming Module
  • EventTiming Module
  • MinMaxTiming Module
  • RepeatTiming Module
  • MultiArcTiming Module
  • AccessKeyTiming Module
  • BasicTimeContainers Module
  • BasicExclTimeContainers Module
• Animation functionality
  • BasicAnimation Module
• Content Control functionality
  • BasicContentControl Module
  • PrefetchControl Module
  • SkipContentControl Module
  • CustomTestAttributes Module
• Layout functionality
  • BasicLayout Module
  • AudioLayout Module
  • SubRegionLayout Module
  • BackgroundTilingLayout Module
  • AlignmentLayout Module
  • OverrideLayout Module
  • MultiWindowLayout Module
• Linking functionality
  • BasicLinking Module
  • LinkingAttributes Module
• Transition Effects functionality
  • BasicTransitions Module
  • FullScreenTransitions Module
• Media functionality
  • BasicMedia Module
  • MediaClipping Module
  • MediaDescription Module
  • MediaParam Module
  • BrushMedia Module
  • MediaAccessibility Module
  • MediaPanZoom Module
• SMILtext functionality
  • BasicText Module
  • TextStyling Module
  • TextFlow Module
• State functionality

The collection names contained in the following table define the STB Profile vocabulary.

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.

23.6.4 Animation Module

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 :

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].

Integration definitions

The STB Profile defines a set of integration definitions as required by the Animation modules. These definitions are:

• Animation values in the STB Profile are subject to the same syntax requirements as the attribute values on the animated elements.
• Percentage values on the attributes have the same semantics as they do on the attribute. If percentage values are not supported on an attribute then percentage values are not supported for animation in the STB Profile.
• The STB Profile supports CSS2 [CSS2] color names. The lower clamping bound color value is the black color or rgb(0%, 0%, 0%) and the higher clamping color value is the white color or rgb(100%, 100%, 100%). Values on an animated color lower than the lower clamping bound are clamped to the black color; values greater than the higher clamping color are clamped to the white color.
• The semantics of clamping values for attributes should be performed in floating point with a precision of at least that given by a 4-byte IEEE-format real number [IEEE-Arithmetic]. Cumulative and additive presentation values should be computed without regard to the range of the target attribute. Prior to display, the presentation value should be reduced or increased to the nearest value which is within the range of the target attribute. For integer attributes the computed value should then be rounded to the nearest integer (coerced-integer-value). The mathematical definition of rounding is:

  coerced-integer-value = Math.floor( interpolated-value + 0.5 )

• The position of the region element to which the animateMotion element applies is the top left corner, in the coordinate system within which the 'top' and 'left' attributes are defined in the Layout modules.
• The origin for the animateMotion when applied to the sub-region on media elements is the top left of the containing region as defined in the Layout modules.

23.6.5 Content Control Modules

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 :

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":

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.

23.6.6 Layout Modules

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 :

The attribute collection SubregionAttributes is defined as follows:

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

23.6.7 Linking Modules

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 :

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.

23.6.8 Media Object Modules

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:

Widely Supported Content Types

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].

Media Object Integration Requirements

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.

23.6.9 Metainformation Module

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].

23.6.10 Structure Module

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 :

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.

23.6.11 Timing and Synchronization Modules

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 :

The Attribute collection Timing is defined as follows:

This profile adds the par, seq, and excl elements to the content model of the body element of the Structure Module and adds these elements to the content model of the a element of the Linking Modules.

Elements of the Media Object Modules have the attributes describing timing and properties of contents.

Supported Event Symbols

The STB Profile specifies which types of events can be used as part of the begin and end attribute values. The supported events are described as Event-symbols according to the syntax introduced in the SMIL Timing and Synchronization module.

The supported event symbols in the DTB Profile are:

As defined by the SMIL syncbase timing semantics, any event timing attributes that reference an invalid time-value description will be treated as if "indefinite" were specified.

Event semantics

focusInEvent:

Raised when a media element gets the keyboard focus in its rendering space, i.e., when it becomes the media element to which all subsequent keystroke-event information is passed. Once an element has the keyboard focus, it continues to have it until a user action or DOM method call either removes the focus from it or gives the focus to another media element, or until its rendering space is removed. Only one media element can have the focus at any particular time. The focusInEvent is delivered to media elements only, and does not bubble.

focusOutEvent:

Raised when a media element loses the keyboard focus from its rendering space, i.e., when it stops being the media element to which all subsequent keystroke-event information is passed. The focusOutEvent is delivered to media elements only, and does not bubble.

activateEvent:

Raised when a media element is activated by user input such as by a mouse click within its visible rendering space or by specific keystrokes when the element has the keyboard focus. The activateEvent is delivered to media elements only, and does not bubble.

beginEvent:

Raised when the element actually begins playback of its active duration. If an element does not ever begin playing, this event is never raised. If an element has a repeat count, beginEvent is only raised at the beginning of the first iteration. The beginEvent is delivered to elements that support timing, such as media elements and time containers, and does not bubble.

endEvent:

Raised when an element actually ends playback; this is when its active duration is reached or whenever a playing element is stopped. In the following example,

<ref id="x" end="30s" src="15s.mpg" />
<ref id="y" end="10s" src="20s.mpg" />
<ref id="z" repeatCount="4" src="5s.mpg" />

x.endEvent occurs at roughly 30s when the active duration is reached, y.endEvent occurs at roughly 10s when the playback of the continuous media is ended early by the active duration being reached, and z.endEvent occurs at roughly 20s when the fourth and final repeat has completed, thus reaching the end of its active duration. The endEvent is delivered to elements which support timing, such as media elements and time containers, and does not bubble.

repeatEvent:

Raised when the second and subsequent iterations of a repeated element begin playback. An element that has no repeatDur, repeatCount, or repeat attribute but that plays two or more times due to multiple begin times will not raise a repeatEvent when it restarts. Also, children of a time container that repeats will not raise their own repeatEvents when their parent repeats and they begin playing again. The repeatEvent is delivered to elements which support timing, such as media elements and time containers, and does not bubble.

inBoundsEvent:

Raised when one of the following happens:

• by any input from the mouse or other input device that brings the mouse cursor from outside to within the bounds of a media element's rendering space, regardless of what part, if any, of that rendering space is visible at the time, i.e., z-order is not a factor.
• by any other action that moves the "cursor" or "pointer", as defined by the implementation, from outside to within the bounds of a media element's rendering space, regardless of what part, if any, of that rendering space is visible at the time, i.e., z-order is not a factor. An implementation may decide, for instance, to raise an inBoundsEvent on an element whenever it gets the focus, including when keystrokes give it the focus.

A media element's bounds are restrained by the bounds of the region in which it is contained., i.e., a media element's bounds do not extend beyond its region's bounds. The inBoundsEvent is delivered to media elements only, and does not bubble.

Note that, unlike with keyboard focus which can only be active on one object at a time, the state of being within an object's bounds can be true for multiple objects simultaneously. For instance, if one object is on top of another and the cursor is placed on top of both objects, both would have raised an inBoundsEvent more recently than the raising of any respective outOfBoundsEvent. If a player does not support a pointer cursor, then these players will typically not generate the inBoundsEvent and outOfBoundEvent events.

outOfBoundsEvent:

Raised when one of the following happens:

• by any input from the mouse or other input device that brings the mouse cursor from within to outside the bounds of a media element's rendering space, regardless of what part, if any, of that rendering space is visible at the time,
• by any other action that moves the "cursor" or "pointer", as defined by the implementation, from within to outside the bounds of a media element's rendering space, regardless of what part, if any, of that rendering space is visible at the time.

A media element's bounds are restrained by its region's bounds, i.e., a media element's bounds do not extend beyond its region's bounds. The outOfBoundsEvent is delivered to media elements only, and does not bubble.

Order of raising of simultaneous events:

There will be cases where events occur simultaneously. To ensure that each STB implementation handles them in the same order, the following order must be used to resolve ties:

1. InBoundsEvent
2. focusInEvent (should follow 1)
3. activateEvent (should follow 2)
4. OutOfBoundsEvent
5. focusOutEvent (should follow 4)
6. endEvent
7. beginEvent (must follow 6)
8. repeatEvent

Events are listed in order of precedence, e.g., if event #6 in this list occurs at the same time as event #7, then #6 must be raised prior to #7.

The InBoundsEvent, focusInEvent, OutOfBoundsEvent, activateEvent, and focusOutEvent events do not bubble and are delivered to the target media element.

The beginEvent, endEvent and repeatEvent events do not bubble and are delivered to the timed element on which the event occurs.

Extending the set of supported events

The STB Profile supports an extensible set of events. In order to resolve possible name conflicts with the events that are supported in this profile qualified event names are supported. Namespace prefixes are used to qualify the event names. As a result, the colon is reserved in begin and end attributes for qualifying event names.

For example:

<smil ... xmlns:example="http://www.example.com">
   <img id="foo" .../> 
   <audio begin="foo.example:focusInEvent".../>
    ... 
</smil>

Integration definitions

A SMIL document's begin time is defined as the moment a user agent begins the timeline for the overall document. A SMIL document's end time is defined as equal to the end time of the body element.

23.6.12 Transition Effects Modules

The Transition Effects Modules provide a framework for describing transitions such as fades and wipes. The Transition Modules define semantics for the transition element. The STB Profile includes the functionality of the BasicTransitions and FullScreenTransitions modules.

In the STB Profile, Transition Effects elements have the following attributes and content model :

This profile adds the transition element to the content model of the head element of the Structure Module.

The Transition Effects Modules add transIn and transOut attributes to ref, animation, audio, img, video, text, textstream and brush elements of the Media Object Modules.

The Transition Effects Modules add the transition value to the fill attribute for all elements on which this value of the fill attribute is supported.

23.6.13 SMILText Module

To be updated

In the STB Profile, SMILText elements have the following attributes and content model :

23.6.14 State Module

To be updated

This section is normative.

The STB Profile Document Type Definition is defined as a set of SMIL 3.0 modules. All SMIL 3.0 modules are integrated according to the guidelines in the W3C Note "Synchronized Multimedia Modules based upon SMIL 1.0" [SMIL-MOD], and defined within their respective module sections.