REC-smil-19980615
REC-smil-19980615
W3C Recommendation 15-June-1998
Copyright
© 1998 W3C
(MIT,
INRIA,
Keio), All Rights Reserved. W3C
liability,
trademark,
document use and
software licensing
rules apply. Your interactions with this site are in accordance with
our public
and Member
privacy statements.
This document has been prepared by the Synchronized Multimedia Working Group
(WG) of the World Wide Web Consortium. The WG included the following individuals:
Acknowledgments: In addition to the working group members,
the following people contributed to the SMIL effort: Bert Bos (W3C), Dan
Connolly (W3C), Patrick Deunhouwer (Philips), Martin Dürst (W3C), Al
Gilman, Håkon Lie (W3C), Chris Lilley (W3C), Curtis Reynolds
(RealNetworks), Michael Riesman, Curtis Reynolds (RealNetworks), Henning
Schulzrinne (Columbia University) and Koga Youichirou (W3C).
Editor: Philipp Hoschka, W3C
(hoschka@w3.org)
This document specifies version 1 of the Synchronized Multimedia Integration
Language (SMIL 1.0, pronounced "smile"). SMIL allows integrating a set of
independent multimedia objects into a synchronized multimedia presentation.
Using SMIL, an author can
This specification is structured as follows: Section 1 presents the specification
approach. Section 2 defines the "smil" element. Section 3 defines the elements
that can be contained in the head part of a SMIL document. Section
4 defines the elements that can be contained in the body part of a SMIL document.
In particular, this Section defines the time model used in SMIL. Section
5 describes the SMIL DTD.
This document was edited in place on 15 sept 2015, to fix a broken link in the above "latest version".
This document has been reviewed by W3C Members and other interested parties
and has been endorsed by the Director as a W3C Recommendation. It is a stable
document and may be used as reference material or cited as a normative reference
from another document. W3C's role in making the Recommendation is to draw
attention to the specification and to promote its widespread deployment.
This enhances the functionality and interoperability of the Web.
Comments on this Recommendation may be sent to the public mailing list
www-smil@w3.org.
The English version of this specification is the only normative version.
However, for translations in other languages see
http://www.w3.org/AudioVideo/SMIL/translations.
The list of known errors in this specification is available at
http://www.w3.org/AudioVideo/SMIL/errata.
SMIL documents are XML 1.0 documents [XML10]. The
reader is expected to be familiar with the concepts and terms defined in
XML 1.0.
This specification does not rely on particular features defined in URLs that
cannot potentially be expressed using URNs. Therefore, the more generic term
URI [URI] is used throughout the specification.
The syntax of SMIL documents is defined by the DTD in Section
5.2. The syntax of an attribute value that cannot be defined using the
DTD notation is defined together with the first element using an attribute
that can contain the attribute value. The syntax of such attribute values
is defined using the Extended Backus-Naur Form (EBNF) defined in the XML
1.0 specification.
An element definition is structured as follows: First, all attributes of
the element are defined in alphabetical order. An attribute is defined in
the following way: If the attribute is used by an element for the first time
in the specification, the semantics of the attribute are defined. If the
attribute has already been used by another element, the specification refers
to the definition of the attribute in the first element that used it. The
definition of element attributes is followed by the definition of any attribute
values whose syntax cannot be defined using the DTD notation. The final
section in an element definition specifies the element content.
Element Attributes
The "smil" element can have the following attribute:
Element Content
The "smil" element can contain the following children:
The "head" element contains information that is not related to the temporal
behavior of the presentation.
Element Attributes
The "head" element can have the following attribute:
Element Content
The "head" element can contain the following children:
The "head" element may contain any number of "meta" elements and either a
"layout" element or a "switch" element.
The "layout" element determines how the elements in the document's body are
positioned on an abstract rendering surface (either visual or acoustic).
If a document contains no layout element, the positioning of the body elements
is implementation-dependent.
A SMIL document can contain multiple alternative layouts by enclosing several
layout elements within a "switch" element (defined in Section
4.3). This can be used for example to describe the document's layout
using different layout languages.
The following example shows how CSS2 can be used as alternative to the SMIL
basic layout language (defined in Section 3.3):
(note that in this example, both layout alternatives result in the same layout)
Element Attributes
Element Content
If the type attribute of the layout element has the value
"text/smil-basic-layout", it can contain the following elements:
If the type attribute of the "layout" element has another value, the element
contains character data.
This section defines a basic layout language for SMIL. SMIL basic layout
is consistent with the visual rendering model defined in CSS2, it reuses
the formatting properties defined by the CSS2 specification, and newly introduces
the "fit" attribute [CSS2]. The reader is expected
to be familiar with the concepts and terms defined in CSS2.
SMIL basic layout only controls the layout of media object elements (defined
in Section 4.2.3). It is illegal to use SMIL
basic layout for other SMIL elements.
The type identifier for SMIL basic layout is "text/smil-basic-layout".
Fixed Property Values
The following stylesheet defines the values of the CSS2 properties "display"
and "position" that are valid in SMIL basic layout. These property values
are fixed:
Note that as a result of these definitions, all absolutely positioned elements
(animation, img, ref, text, textstream and video) are contained within a
single containing block defined by the content content edge of the root element
(smil).
Default Values
SMIL basic layout defines default values for all layout-related attributes.
These are consistent with the initial values of the corresponding properties
in CSS2.
If the author wants to select the default layout values for all
media object elements in a document, the document must contain an empty layout
element of type "text/smil-basic-layout" such as:
The region element controls the position, size and scaling of media object
elements.
In the following example fragment, the position of a text element is set
to a 5 pixel distance from the top border of the rendering window:
Element Attributes
The "region" element can have the following attributes:
The default value of "fill" is "hidden".
If the value of the "skip-content" attribute is "true", and one of the cases
above apply, the content of the element is ignored. If the value is "false",
the content of the element is processed.
Element Content
"region" is an empty element.
The "root-layout" element determines the value of the layout properties of
the root element, which in turn determines the size of the viewport, e.g.
the window in which the SMIL presentation is rendered.
If a document contains more than one "root-layout" element, this is an error,
and the document should not be displayed.
Element Attributes
The "root-layout" element can have the following attributes:
Element Content
"root-layout" is an empty element.
The "meta" element can be used to define properties of a document (e.g.,
author, expiration date, a list of key words, etc.) and assign values to
those properties. Each "meta" element specifies a single property/value pair.
Element Attributes
The "meta" element can have the following attributes:
The list of properties is open-ended. This specification defines the following
properties:
Element Content
"meta" is an empty element.
The "body" element contains information that is related to the temporal and
linking behavior of the document. It implicitly defines a "seq" element (defined
in Section 4.2.2, see Section 4.2.4 for a definition of the temporal semantics
of the "body" element).
Element Attributes
The "body" element can have the following attribute:
Element Content
The "body" element can contain the following children:
The children of a par element can overlap in time. The textual order of
appearance of children in a par has no significance for the timing of their
presentation.
Element Attributes
The "par" element can have the following attributes:
The resulting set S is the set of "in scope" elements.
The default value of "endsync" is "last".
Note on Synchronization between Children
The accuracy of synchronization between the children in a parallel group
is implementation-dependent. Take the example of synchronization in case
of playback delays, i.e. the behavior when the
"par" element contains two or more continuous media types such as audio or
video, and one of them experiences a delay.
a) hard synchronization: Delay in video: Either the audio is stopped,
or some video frames are dropped. The exact behavior is
implementation-dependent
b) soft synchronization
Figure 4.4: Effect of a delay on playout schedule for players using different
synchronization policies
Attribute Values
The following are examples of legal clock values:
Example use:
Element Content
The par element can contain the following children:
All of these elements may appear multiple times as direct children of a par
element.
The children of a "seq" element form a temporal sequence.
Attributes
The seq element can have the following attributes:
Element Content
The seq element can contain the following children:
The media object elements allow the inclusion of media objects into a SMIL
presentation. Media objects are included by reference (using a URI).
There are two types of media objects: media objects with an intrinsic duration
(e.g. video, audio) (also called "continuous media"), and media objects without
intrinsic duration (e.g. text, image) (also called "discrete media").
Anchors and links can be attached to visual media objects, i.e. media objects
rendered on a visual abstract rendering surface.
When playing back a media object, the player must not derive the exact type
of the media object from the name of the media object element. Instead, it
must rely solely on other sources about the type, such as type information
contained in the "type" attribute, or the type information communicated by
a server or the operating system.
Authors, however, should make sure that the group into which of the media
object falls (animation, audio, img, video, text or textstream) is reflected
in the element name. This is in order to increase the readability of the
SMIL document. When in doubt about the group of a media object, authors should
use the generic "ref" element.
Element Attributes
Media object elements can have the following attributes:
The value of this attribute consists of a metric specifier, followed by a
time value whose syntax and semantics depend on the metric specifier. The
following formats are allowed:
The time value has the format hours:minutes:seconds:frames.subframes. If
the frame value is zero, it may be omitted. Subframes are measured in
one-hundredth of a frame.
Element Content
Media Object Elements can contain the following element:
In the following discussion, the term "element" refers to synchronization
elements only.
For each element we define the implicit, explicit, desired, and effective
begin, duration, and end.
The effective begin/duration/end specify what the reader of the document
will perceive.
The implicit, explicit, and desired values are auxiliary values used to define
the effective values.
The rules for calculating each of these values for the elements defined in
SMIL 1.0 are described in the next section.
It is an error if the explicit begin is earlier than the implicit begin of
the element.
This section defines how time model values are calculated for the synchronization
elements of SMIL 1.0 in cases that are not covered by the rules in
Section 4.2.4.1.
The first description that matches the element is the one that is to be used:
Determining the desired begin of an element
The desired begin of an element is determined by using rule 7 in
Section 4.2.4.1.
The effective begin of an element is equal to the desired begin
of the element, unless the effective end of the parent element is earlier
than this time, in which case the element is not shown at all.
The switch element allows an author to specify a set of alternative elements
from which only one acceptable element should be chosen. An element is acceptable
if the element is a SMIL 1.0 element, the media-type can be decoded, and
all of the test-attributes (see Section 4.4) of the element
evaluate to "true".
An element is selected as follows: the player evaluates the elements in the
order in which they occur in the switch element. The first acceptable element
is selected at the exclusion of all other elements within the switch.
Thus, authors should order the alternatives from the most desirable to the
least desirable. Furthermore, authors should place a relatively fail-safe
alternative as the last item in the <switch> so that at least one item
within the switch is chosen (unless this is explicitly not desired).
Implementations should NOT arbitrarily pick an object within a
<switch> when test-attributes for all fail.
Note that http URIs provide for content-negotiation, which may be an alternative
to using the "switch" element in some cases.
Attributes
The switch element can have the following attributes:
Element Content
If the "switch" element is used as a direct or indirect child of a "body"
element, it can contain the following children:
All of these elements may appear multiple times as children of a "switch"
element.
If the "switch" element is used within a "head" element, it can contain the
following child:
This specification defines a list of test attributes that can be added to
any synchronization element, and that test system capabilities and settings.
Conceptually, these attributes represent boolean tests. When one of the
test attributes specified for an element evaluates to "false", the element
carrying this attribute is ignored.
Within the list below, the concept of "user preference" may show up. User
preferences are usually set by the playback engine using a preferences dialog
box, but this specification does not place any restrictions on how such
preferences are communicated from the user to the SMIL player.
The following test attributes are defined in SMIL 1.0:
Evaluates to "true" if one of the languages indicated by user preferences
exactly equals one of the languages given in the value of this parameter,
or if one of the languages indicated by
user preferences exactly equals a prefix of one of the languages given in
the value of this parameter such that the first tag character following the
prefix is "-".
Evaluates to "false" otherwise.
Note: This use of a prefix matching rule does not imply that language tags
are assigned to languages in such a way that it is always true that if a
user understands a language with a certain tag, then this user will also
understand all languages with tags for which this tag is a prefix.
The prefix rule simply allows the use of prefix tags if this is the case.
Implementation note: When making the choice of linguistic preference available
to the user, implementors should take into account the fact that users are
not familiar with the details of language matching as described above, and
should provide appropriate guidance. As an example, users may assume that
on selecting "en-gb", they will be served any kind of English document if
British English is not available. The user interface for setting user preferences
should guide the user to add "en" to get the best matching behavior.
Multiple languages MAY be listed for content that is intended for multiple
audiences. For example, a rendition of the "Treaty of Waitangi", presented
simultaneously in the original Maori and English versions, would call for:
However, just because multiple languages are present within the object on
which the system-language test attribute is placed, this does not mean that
it is intended for multiple linguistic audiences. An example would be a
beginner's language primer, such as "A First Lesson in Latin," which is clearly
intended to be used by an English-literate audience. In this case, the
system-language test attribute should only include "en".
Authoring note: Authors should realize that if several alternative language
objects are enclosed in a "switch", and none of them matches, this may lead
to situations such as a video being shown without any audio track. It is
thus recommended to include a "catch-all" choice at the end of such a switch
which is acceptable in all cases.
Examples
1) Choosing between content with different bitrate
In a common scenario, implementations may wish to allow for selection via
a "system-bitrate" parameter on elements. The media player evaluates each
of the "choices" (elements within the switch) one at a time, looking for
an acceptable bitrate given the known characteristics of the link between
the media player and media server.
2) Choosing between audio resources with different bitrate
The elements within the switch may be any combination of elements. For instance,
one could merely be specifying an alternate audio track:
3) Choosing between audio resources in different languages
In the following example, an audio resource is available both in French and
in English. Based on the user's preferred language, the player can choose
one of these audio resources.
4) Choosing between content written for different screens
In the following example, the presentation contains alternative parts designed
for screens with different resolutions and bit-depths. Depending on the
particular characteristics of the screen, the player can choose one of the
alternatives.
5) Distinguishing caption tracks from stock tickers
In the following example, captions are shown only if the user wants captions
on.
6) Choosing the language of overdub and caption tracks
In the following example, a French-language movie is available with English,
German, and Dutch overdub and caption tracks. The following SMIL segment
expresses this, and switches on the alternatives that the user prefers.
The link elements allows the description of navigational links between objects.
SMIL provides only for in-line link elements. Links are limited to
uni-directional single-headed links (i.e. all links have exactly one source
and one destination resource). All links in SMIL are actuated by the user.
Handling of Links in Embedded Documents
Due to its integrating nature, the presentation of a SMIL document may involve
other (non-SMIL) applications or plug-ins. For example, a SMIL browser may
use an HTML plug-in to display an embedded HTML page. Vice versa, an HTML
browser may use a SMIL plug-in to display a SMIL document embedded in an
HTML page.
In such presentations, links may be defined by documents at different levels
and conflicts may arise. In this case, the link defined by the containing
document should take precedence over the link defined by the embedded object.
Note that since this might require communication between the browser and
the plug-in, SMIL implementations may choose not to comply with this
recommendation.
If a link is defined in an embedded SMIL document, traversal of the link
affects only the embedded SMIL document.
If a link is defined in a non-SMIL document which is embedded in a SMIL document,
link traversal can only affect the presentation of the embedded document
and not the presentation of the containing SMIL document. This restriction
may be released in future versions of SMIL.
Addressing
SMIL supports name fragment identifiers and the '#' connector. This means
that SMIL supports locators as currently used in HTML (e.g. it uses locators
of the form "http://foo.com/some/path#anchor1").
Linking to SMIL Fragments
A locator that points to a SMIL document may contain a fragment part (e.g.
http://www.w3.org/test.smi#par1). The fragment part is an id value that
identifies one of the elements within the referenced SMIL document. If a
link containing a fragment part is followed, the presentation should start
as if the user had fast-forwarded the presentation represented by the destination
document to the effective begin of the element designated by the fragment.
The following special cases can occur:
The functionality of the "a" element is very similar to the functionality
of the "a" element in HTML 4.0 [HTML40] . SMIL
adds an attribute "show" that controls the temporal behavior
of the source when the link is followed. For synchronization purposes, the
"a" element is transparent, i.e. it does not influence the synchronization
of its child elements. "a" elements may not be nested. An "a" element must
have an href attribute.
Attributes
The "a" element can have the following attributes:
The default value of "show" is "replace".
Element Content
The "a" element can contain the following children:
Examples
Example 1
The link starts up the new presentation replacing the presentation that was
playing.
In the example, the second line can be replaced by a reference to any valid
subtree of an SMIL presentation.
Example 2
The link starts up the new presentation in addition to the presentation that
was playing.
For example, this allows a SMIL player to spawn off an HTML browser.
Example 3
The link starts up the new presentation and pauses the presentation that
was playing.
Example 4
The following example contains a link from an element in one presentation
A to the middle of another presentation B. This would play presentation B
starting from the effective begin of the element with id "next".
The functionality of the "a" element is restricted in that it only allows
associating a link with a complete media object. HTML image maps have
demonstrated that it is useful to associate links with spatial subparts of
an object. The anchor element realizes similar functionality for SMIL:
Attributes
The anchor element can have the following attributes:
Figure 4.5: Semantics of "coords" attribute
Examples
1) Associating links with spatial subparts
In the following example, the screenspace taken up by a video clip is split
into two sections. A different link is associated with each of these sections.
2) Associating links with temporal subparts
In the following example, the duration of a video clip is split into two
subintervals. A different link is associated with each of these subintervals.
3) Jumping to a subpart of an object
The following example contains a link from an element in one presentation
A to the middle of a video object contained in another presentation B. This
would play presentation B starting from second 5 in the video (i.e. the
presentation would start as if the user had fast-forwarded the whole presentation
to the point at which the designated fragment in the "CoolStuff" video begins).
4) Combining different uses of links
The following example shows how the different uses of associated links can
be used in combination.
A SMIL 1.0 document may optionally contain a document type declaration,
which names the document type definition (DTD) in use for the document.
For SMIL, the document type declaration should look as follows (the double
quotes can be replaced by single quotes):
The XML 1.0 specification provides a way to extend the DTD using the
<!DOCTYPE> element, for instance to add a new set of entity definitions.
Authors must not use this feature with SMIL since many SMIL players will
not support it.
The following is illegal in SMIL:
(non-normative)
In the future, SMIL 1.0 may be extended by another W3C recommendation, or
by private extensions.
For these extensions, it is recommended that the following rules are obeyed:
It is recommended that SMIL 1.0 players are prepared to handle documents
that contain extension that obey these two rules.
Extensions should be handled using an XML namespace mechanism, once such
a mechanism becomes a W3C recommendation. In the rest of the section, the
syntax and semantics for XML namespaces defined in the W3C note [NAMESPACE]
will be used for demonstration purposes only.
The following cases can occur:
When the XML namespace mechanism is used to include SMIL elements and attributes
in other XML-based documents, it is recommended to use the following namespace
identifier:
About this Document
Abstract
Status of this Document
Available languages
Errata
Table of Contents
1 Specification Approach
2 The smil Element
3 The Document Head
3.1 The
head Element
3.2 The layout Element
<smil>
<head>
<switch>
<layout type="text/css">
[region="r"] { top: 20px; left: 20px }
</layout>
<layout>
<region id="r" top="20" left="20" />
</layout>
</switch>
</head>
<body>
<seq>
<img region="r" src="http://www.w3.org/test" dur="10s" />
</seq>
</body>
</smil>
3.3 SMIL Basic Layout Language
a {display:block}
anchor {display:block}
animation {display: block;
position: absolute}
body {display: block}
head {display: none}
img {display: block;
position: absolute}
layout {display: none}
meta {display: none}
par {display: block}
region {display: none}
ref {display: block;
position: absolute}
root-layout {display: none}
seq {display: block}
smil {display: block}
switch {display:block}
text {display: block;
position: absolute}
textstream {display: block;
position: absolute}
video {display: block;
position: absolute}
<layout type="text/smil-basic-layout"></layout>
3.3.1 The region Element
<smil>
<head>
<layout>
<region id="a" top="5" />
</layout>
</head>
<body>
<text region="a" src="text.html" dur="10s" />
</body>
</smil>
If the background-color attribute is absent, the background is transparent.
This attribute can have the following values:
A region element is applied to a positionable element by setting the
region attribute of the positionable element to the id
value of the region.
The "id" attribute is required for "region" elements.
The default value is zero.
The default value for "skip-content" is "true".
It is strongly recommended that all "region" elements have
a "title" attribute with a meaningful description. Authoring tools should
ensure that no element can be introduced into a SMIL document without this
attribute.
The default value is zero.
3.3.2 The
root-layout element
Sets the height of the root element. Only length values are allowed.
Sets the width of the root element. Only length values are allowed.
3.4 The meta Element
The "content" attribute is required for "meta" elements.
The "name" attribute is required for "meta" elements.
4 The Document Body
4.1 The
body Element
4.2 Synchronization Elements
4.2.1 The par Element
The attribute can contain the following two types of values:
The semantics of a delay value depend on the element's first ancestor that
is a synchronization element (i.e. ancestors that are "a" or "switch" elements
are ignored):
The element generating the event must be "in scope". The set of "in scope"
elements S is determined as follows:
<par>
<audio id="a" begin="6s" src="audio" />
</par>
Figure 4.1: Using a delay value within a "par" element
<seq>
<audio src="audio1" />
<audio begin="5s" src="audio2" />
</seq>
Figure 4.2: Using a delay value within a "seq" element
<par>
<audio id="a" begin="6s" ... />
<img begin="id(a)(4s)" ... />
</par>
Figure 4.3: Synchronization attribute with element event value
For a definition of the semantics of this value, see
Section 4.2.4.
This attribute value has the following syntax:
id-ref ::= "id(" id-value ")"
where "id-value" must be a legal XML identifier.
For a definition of the semantics of this value, see
Section 4.2.4.
For a definition of the semantics of this value, see
Section 4.2.4.
The "region" attribute on "par" elements cannot be used by the basic layout
language for SMIL defined in this specification. It is added for completeness,
since it may be required by other layout languages.
It is strongly recommended that all "par" elements have a "title" attribute
with a meaningful description. Authoring tools should ensure that no element
can be introduced into a SMIL document without this attribute.
A player can show the following synchronization behaviors:
Clock-val ::= Full-clock-val | Partial-clock-val | Timecount-val
Full-clock-val ::= Hours ":" Minutes ":" Seconds ("." Fraction)?
Partial-clock-val ::= Minutes ":" Seconds ("." Fraction)?
Timecount-val ::= Timecount ("." Fraction)?
("h" | "min" | "s" | "ms")? ; default is "s"
Hours ::= 2DIGIT; any positive number
Minutes ::= 2DIGIT; range from 00 to 59
Seconds ::= 2DIGIT; range from 00 to 59
Fraction ::= DIGIT+
Timecount ::= DIGIT+
2DIGIT ::= DIGIT DIGIT
DIGIT ::= [0-9]
3h = 3 hours
45min = 45 minutes
30s = 30 seconds
5ms = 5 milliseconds
A fraction x with n digits represents the following value:
x * 1/10**n
Examples:
00.5s = 5 * 1/10 seconds = 500 milliseconds
00:00.005 = 5 * 1/1000 seconds = 5 milliseconds
An element event has the following syntax:
Element-event ::= "id(" Event-source ")(" Event ")"
Event-source ::= Id-value
Event ::= "begin" | Clock-val | "end"
Example use: begin="id(x)(begin)"
It is an error to use a clock value that exceeds the value of the effective
duration of the element generating the event.
begin="id(x)(45s)"
Example use: begin="id(x)(end)"
4.2.2 The seq Element
The region attribute on "seq" elements cannot be used by the basic layout
language for SMIL defined in this specification. It is added for completeness,
since it may be required by other layout languages.
It is strongly recommended that all "seq" elements have a "title" attribute
with a meaningful description. Authoring tools should ensure that no element
can be introduced into a SMIL document without this attribute.
4.2.3 Media Object Elements: The ref,
animation, audio,img, video,text and
textstream elements
Values in the clip-begin attribute have the following syntax:
Clip-time-value ::= Metric "=" ( Clock-val | Smpte-val )
Metric ::= Smpte-type | "npt"
Smpte-type ::= "smpte" | "smpte-30-drop" | "smpte-25"
Smpte-val ::= Hours ":" Minutes ":" Seconds
[ ":" Frames [ "." Subframes ]]
Hours ::= 2DIGIT
Minutes ::= 2DIGIT
Seconds ::= 2DIGIT
Frames ::= 2DIGIT
Subframes ::= 2DIGIT
Examples:
clip-begin="smpte=10:12:33:20"
Examples:
clip-begin="npt=123.45s""
clip-begin="npt=12:05:35.3
If the value of the "clip-end" attribute exceeds the duration of the
media object, the value is ignored, and the clip end is set equal to the
effective end of the media object.
It is strongly recommended that all media object elements have a "title"
attribute with a meaningful description. Authoring tools should ensure that
no element can be introduced into a SMIL document without this attribute.
4.2.4 SMIL Time Model
4.2.4.1 Time Model Values
begin = "value of explicit-begin"
end = "value of explicit-end"
dur = "value of explicit-duration"
4.2.4.2 Determining Time Model Values for SMIL
1.0 Elements
Determining the implicit begin of an element
Determining the implicit end of an element
Determining the desired end of an element
Determining the effective begin of an element
Determining the effective end of an element
The last state of the element is retained on the screen until the
effective end of the element.
4.3 The switch Element
It is strongly recommended that all switch elements have a "title"
attribute with a meaningful description Authoring tools should ensure that
no element can be introduced into a SMIL document without this attribute.
Multiple layout elements may occur within the switch element.
4.4 Test Attributes
The attribute can assume any integer value greater than 0. If the value exceeds
an implementation-defined maximum bandwidth value, the attribute always evaluates
to "false".
<audio src="foo.rm" system-language="mi, en"/>
screen-size-val ::= screen-height"X"screen-width
Each of these is a pixel value, and must be an integer value greater than
0. Evaluates to "true" if the SMIL playback engine is capable of displaying
a presentation of the given size. Evaluates to "false" if the SMIL playback
engine is only capable of displaying a smaller presentation.
...
<par>
<text .../>
<switch>
<par system-bitrate="40000">
...
</par>
<par system-bitrate="24000">
...
</par>
<par system-bitrate="10000">
........
</par>
</switch>
</par>
...
...
<switch>
<audio src="joe-audio-better-quality" system-bitrate="16000" />
<audio src="joe-audio" system-bitrate="8000" />
</switch>
...
...
<switch>
<audio src="joe-audio-french" system-language="fr"/>
<audio src="joe-audio-english" system-language="en"/>
</switch>
...
...
<par>
<text .../>
<switch>
<par system-screen-size="1280X1024" system-screen-depth="16">
........
</par>
<par system-screen-size="640X480" system-screen-depth="32">
...
</par>
<par system-screen-size="640X480" system-screen-depth="16">
...
</par>
</switch>
</par>
...
...
<seq>
<par>
<audio src="audio.rm"/>
<video src="video.rm"/>
<textstream src="stockticker.rtx"/>
<textstream src="closed-caps.rtx" system-captions="on"/>
</par>
</seq>
...
...
<par>
<switch>
<audio src="movie-aud-en.rm" system-language="en"
system-overdub-or-caption="overdub"/>
<audio src="movie-aud-de.rm" system-language="de"
system-overdub-or-caption="overdub"/>
<audio src="movie-aud-nl.rm" system-language="nl"
system-overdub-or-caption="overdub"/>
<!-- French for everyone else -->
<audio src="movie-aud-fr.rm"/>
</switch>
<video src="movie-vid.rm"/>
<switch>
<textstream src="movie-caps-en.rtx" system-language="en"
system-overdub-or-caption="caption"/>
<textstream src="movie-caps-de.rtx" system-language="de"
system-overdub-or-caption="caption"/>
<textstream src="movie-caps-nl.rtx" system-language="nl"
system-overdub-or-caption="caption"/>
<!-- French captions for those that really want them -->
<textstream src="movie-caps-fr.rtx" system-captions="on"/>
</switch>
</par>
...
4.5 Hyperlinking Elements
4.5.1 The a Element
The "href" attribute is required for "a" elements.
It is strongly recommended that all "a" elements have a "title" attribute
with a meaningful description. Authoring tools should ensure that no element
can be introduced into a SMIL document without this attribute.
<a href="http://www.cwi.nl/somewhereelse.smi">
<video src="rtsp://foo.com/graph.imf" region="l_window"/>
</a>
<a href="http://www.cwi.nl/somewhereelse.smi" show="new">
<video src="rtsp://foo.com/graph.imf" region="l_window"/>
</a>
<a href="http://www.cwi.nl/somewhereelse.smi" show="pause">
<video src="rtsp://foo.com/graph.imf" region="l_window"/>
</a>
Presentation A:
<a href="http://www.cwi.nl/presentationB#next">
<video src="rtsp://foo.com/graph.imf"/>
</a>
Presentation B (http://www.cwi.nl/presentation):
...
<seq>
<video src="rtsp://foo.com/graph.imf"/>
<par>
<video src="rtsp://foo.com/timbl.rm" region="l_window"/>
<video id="next" src="rtsp://foo.com/v1.rm" region="r_window"/>
^^^^^^^^^
<text src="rtsp://foo.com/caption1.html" region="l_2_title"/>
<text src="rtsp://foo.com/caption2.rtx" region="r_2_title"/>
</par>
</seq>
...
4.5.2 The
anchor Element
An attribute with an erroneous coords value is ignored (right-x smaller or
equal to left-x, bottom-y smaller or equal to top-y). If the rectangle defined
by the coords attribute exceeds the area covered by the media object, exceeding
height and width are clipped at the borders of the media object.
Values of the coords attribute have the following syntax:
coords-value ::= left-x "," top-y "," right-x "," bottom-y
D
It is strongly recommended that all anchor elements have a "title"
attribute with a meaningful description. Authoring tools should ensure that
no element can be introduced into a SMIL document without this attribute.
<video src="http://www.w3.org/CoolStuff">
<anchor href="http://www.w3.org/AudioVideo" coords="0%,0%,50%,50%"/>
<anchor href="http://www.w3.org/Style" coords="50%,50%,100%,100%"/>
</video>
<video src="http://www.w3.org/CoolStuff">
<anchor href="http://www.w3.org/AudioVideo" begin="0s" end="5s"/>
<anchor href="http://www.w3.org/Style" begin="5s" end="10s"/>
</video>
Presentation A:
<a href="http://www.cwi.nl/mm/presentationB#tim">
<video id="graph" src="rtsp://foo.com/graph.imf" region="l_window"/>
</a>
Presentation B:
<video src="http://www.w3.org/CoolStuff">
<anchor id="joe" begin="0s" end="5s"/>
<anchor id="tim" begin="5s" end="10s"/>
</video>
Presentation A:
<a href="http://www.cwi.nl/mm/presentationB#tim">
<video id="graph" src="rtsp://foo.com/graph.imf" region="l_window"/>
</a>
Presentation B:
<video src="http://www.w3.org/CoolStuff">
<anchor id="joe" begin="0s" end="5s" coords="0%,0%,50%,50%"
href="http://www.w3.org/"/>
<anchor id="tim" begin="5s" end="10s" coords="0%,0%,50%,50%"
href="http://www.w3.org/Tim"/>
</video>
5 SMIL DTD
5.1 Relation to XML
<!DOCTYPE smil PUBLIC "-//W3C//DTD SMIL 1.0//EN"
"http://www.w3.org/TR/REC-smil/SMIL10.dtd"><!DOCTYPE smil PUBLIC "-//W3C//DTD SMIL 1.0//EN"
"http://www.w3.org/TR/REC-smil/SMIL10.dtd" [
<!ENTITY % AcmeCorpSymbols PUBLIC
"-//Acme Corp//ENTITIES Corporate Symbols//EN"
"http://www.acme.com/corp_symbols.xml"
>
%AcmeCorpSymbols;
]>
5.2 DTD
<!--
This is the XML document type definition (DTD) for SMIL 1.0.
Date: 1998/06/15 08:56:30
Authors:
Jacco van Ossenbruggen <jrvosse@cwi.nl>
Sjoerd Mullender <sjoerd@cwi.nl>
Further information about SMIL is available at:
http://www.w3.org/AudioVideo/
-->
<!-- Generally useful entities -->
<!ENTITY % id-attr "id ID #IMPLIED">
<!ENTITY % title-attr "title CDATA #IMPLIED">
<!ENTITY % skip-attr "skip-content (true|false) 'true'">
<!ENTITY % desc-attr "
%title-attr;
abstract CDATA #IMPLIED
author CDATA #IMPLIED
copyright CDATA #IMPLIED
">
<!--=================== SMIL Document =====================================-->
<!--
The root element SMIL contains all other elements.
-->
<!ELEMENT smil (head?,body?)>
<!ATTLIST smil
%id-attr;
>
<!--=================== The Document Head =================================-->
<!ENTITY % layout-section "layout|switch">
<!ENTITY % head-element "(meta*,((%layout-section;), meta*))?">
<!ELEMENT head %head-element;>
<!ATTLIST head %id-attr;>
<!--=================== Layout Element ====================================-->
<!--
Layout contains the region and root-layout elements defined by
smil-basic-layout or other elements defined an external layout
mechanism.
-->
<!ELEMENT layout ANY>
<!ATTLIST layout
%id-attr;
type CDATA "text/smil-basic-layout"
>
<!--=================== Region Element ===================================-->
<!ENTITY % viewport-attrs "
height CDATA #IMPLIED
width CDATA #IMPLIED
background-color CDATA #IMPLIED
">
<!ELEMENT region EMPTY>
<!ATTLIST region
%id-attr;
%title-attr;
%viewport-attrs;
left CDATA "0"
top CDATA "0"
z-index CDATA "0"
fit (hidden|fill|meet|scroll|slice) "hidden"
%skip-attr;
>
<!--=================== Root-layout Element ================================-->
<!ELEMENT root-layout EMPTY>
<!ATTLIST root-layout
%id-attr;
%title-attr;
%viewport-attrs;
%skip-attr;
>
<!--=================== Meta Element=======================================-->
<!ELEMENT meta EMPTY>
<!ATTLIST meta
name NMTOKEN #REQUIRED
content CDATA #REQUIRED
%skip-attr;
>
<!--=================== The Document Body =================================-->
<!ENTITY % media-object "audio|video|text|img|animation|textstream|ref">
<!ENTITY % schedule "par|seq|(%media-object;)">
<!ENTITY % inline-link "a">
<!ENTITY % assoc-link "anchor">
<!ENTITY % link "%inline-link;">
<!ENTITY % container-content "(%schedule;)|switch|(%link;)">
<!ENTITY % body-content "(%container-content;)">
<!ELEMENT body (%body-content;)*>
<!ATTLIST body %id-attr;>
<!--=================== Synchronization Attributes ========================-->
<!ENTITY % sync-attributes "
begin CDATA #IMPLIED
end CDATA #IMPLIED
">
<!--=================== Switch Parameter Attributes =======================-->
<!ENTITY % system-attribute "
system-bitrate CDATA #IMPLIED
system-language CDATA #IMPLIED
system-required NMTOKEN #IMPLIED
system-screen-size CDATA #IMPLIED
system-screen-depth CDATA #IMPLIED
system-captions (on|off) #IMPLIED
system-overdub-or-caption (caption|overdub) #IMPLIED
">
<!--=================== Fill Attribute ====================================-->
<!ENTITY % fill-attribute "
fill (remove|freeze) 'remove'
">
<!--=================== The Parallel Element ==============================-->
<!ENTITY % par-content "%container-content;">
<!ELEMENT par (%par-content;)*>
<!ATTLIST par
%id-attr;
%desc-attr;
endsync CDATA "last"
dur CDATA #IMPLIED
repeat CDATA "1"
region IDREF #IMPLIED
%sync-attributes;
%system-attribute;
>
<!--=================== The Sequential Element ============================-->
<!ENTITY % seq-content "%container-content;">
<!ELEMENT seq (%seq-content;)*>
<!ATTLIST seq
%id-attr;
%desc-attr;
dur CDATA #IMPLIED
repeat CDATA "1"
region IDREF #IMPLIED
%sync-attributes;
%system-attribute;
>
<!--=================== The Switch Element ================================-->
<!-- In the head, a switch may contain only layout elements,
in the body, only container elements. However, this
constraint cannot be expressed in the DTD (?), so
we allow both:
-->
<!ENTITY % switch-content "layout|(%container-content;)">
<!ELEMENT switch (%switch-content;)*>
<!ATTLIST switch
%id-attr;
%title-attr;
>
<!--=================== Media Object Elements =============================-->
<!-- SMIL only defines the structure. The real media data is
referenced by the src attribute of the media objects.
-->
<!-- Furthermore, they have the following attributes as defined
in the SMIL specification:
-->
<!ENTITY % mo-attributes "
%id-attr;
%desc-attr;
region IDREF #IMPLIED
alt CDATA #IMPLIED
longdesc CDATA #IMPLIED
src CDATA #IMPLIED
type CDATA #IMPLIED
dur CDATA #IMPLIED
repeat CDATA '1'
%fill-attribute;
%sync-attributes;
%system-attribute;
">
<!--
Most info is in the attributes, media objects are empty or
contain associated link elements:
-->
<!ENTITY % mo-content "(%assoc-link;)*">
<!ENTITY % clip-attrs "
clip-begin CDATA #IMPLIED
clip-end CDATA #IMPLIED
">
<!ELEMENT ref %mo-content;>
<!ELEMENT audio %mo-content;>
<!ELEMENT img %mo-content;>
<!ELEMENT video %mo-content;>
<!ELEMENT text %mo-content;>
<!ELEMENT textstream %mo-content;>
<!ELEMENT animation %mo-content;>
<!ATTLIST ref %mo-attributes; %clip-attrs;>
<!ATTLIST audio %mo-attributes; %clip-attrs;>
<!ATTLIST video %mo-attributes; %clip-attrs;>
<!ATTLIST animation %mo-attributes; %clip-attrs;>
<!ATTLIST textstream %mo-attributes; %clip-attrs;>
<!ATTLIST text %mo-attributes;>
<!ATTLIST img %mo-attributes;>
<!--=================== Link Elements =====================================-->
<!ENTITY % smil-link-attributes "
%id-attr;
%title-attr;
href CDATA #REQUIRED
show (replace|new|pause) 'replace'
">
<!--=================== Inline Link Element ===============================-->
<!ELEMENT a (%schedule;|switch)*>
<!ATTLIST a
%smil-link-attributes;
>
<!--=================== Associated Link Element ===========================-->
<!ELEMENT anchor EMPTY>
<!ATTLIST anchor
%skip-attr;
%smil-link-attributes;
%sync-attributes;
coords CDATA #IMPLIED
>
References
Available at
http://www.w3.org/TR/REC-html40/.
W3C working draft. Available at
http://www.w3.org/TR/WD-xml-names.
Available at
http://www.w3.org/TR/REC-PICS-labels-961031
Available at
ftp://ftp.isi.edu/in-notes/rfc1738.txt.
Available at
ftp://ftp.isi.edu/in-notes/rfc1766.txt.
Available at
ftp://ftp.isi.edu/in-notes/rfc1808.txt.
Available at
ftp://ftp.isi.edu/in-notes/rfc2045.txt. Note that this RFC obsoletes
RFC1521, RFC1522, and RFC1590.
Available at
http://www.ics.uci.edu/pub/ietf/uri/draft-fielding-uri-syntax-02.txt.
This is a work in progress that is expected to update
[RFC1738] and
[RFC1808].
Available at
http://www.w3.org/TR/REC-xml/
Appendix
Extending SMIL 1.0
In the following example, the element "new:a" is a legal extension. The elements
"mytags:a" and "b" are syntax errors, since they are not declared using an
XML namespace.
<?xml:namespace ns="http://www.acme.com/new-smil" prefix="new" ?>
<?xml:namespace ns="http://www.w3.org/TR/PR-smil" ?>
<smil>
<body>
<par>
<new:a>
...
</new:a>
<mytags:a ... />
...
</mytags:a>
<b>
...
</b>
</par>
</body>
</smil>
In this case, a SMIL 1.0 player should assume that it is processing a SMIL
document with a version number higher than 1.0.
The following cases can occur:
An unknown element may contain content that consists of SMIL 1.0 elements.
Whether such content is ignored or processed depends on the value of the
"skip-content" attribute. If the attribute is set to "true", or the attribute
is absent, the content is not processed. If it is set to "false", the content
is processed.
Using SMIL 1.0 as an Extension
http://www.w3.org/TR/REC-smil
