QuickTime SMIL Importer

QuickTime 4.1 and later include a SMIL importer that allows many SMIL presentations to be played in the QuickTime Player application and the QuickTime browser plug-in or ActiveX control.

The QuickTime SMIL importer creates a memory-resident QuickTime movie based on the SMIL file. Each media element listed in the SMIL file becomes a QuickTime movie track; the timing, positioning, and layering specified for each element are imported as track characteristics.

The import process is generally very fast—QuickTime does not need to actually download all the media files to begin the presentation. If the presentation contains a large number of elements, however, it can take some time simply to locate all the source files and set up the appropriate movie importer for each file format. A SMIL presentation with half a dozen elements typically opens without a perceptible pause, for example, but a presentation with 30 or 50 elements is likely to open after a noticeable lag.

The QuickTime SMIL importer does not support the full feature set of the SMIL 1.0 or SMIL 2.0 standards, but it does provide a useful way to script a QuickTime presentation using a text file and any media files that QuickTime can display, such as text, still images, audio, digital video, VR panoramas, Flash, and so on.

SMIL Media and SMIL Players

Media elements in a SMIL document are specified by URLs. Media elements can be files—such as text files, JPEG images, and QuickTime movies—or streams. The URLs that specify the media elements can use any of the common protocols—HTTP, FTP, RTSP, file access, and so on. This allows a SMIL file to specify a presentation that mixes streaming and non-streaming media, as well as local and web-based media.

The SMIL specification defines basic media types but it does not define specific media formats. A SMIL file may identify a media element as text, an image, video, or sound, for example, but SMIL itself does not differentiate between AIFF, WAVE, or MP3 audio files, or between DV, AVI, or MPG video formats.

Consequently, the exact set of media elements that can be played by a given SMIL player varies. Any SMIL player is likely to handle a presentation containing only JPEG images and AIFF audio, for example, but for other media and compression formats you may need to target a specific SMIL interpreter for reliable results.

QuickTime supports over 200 different media formats. Any media file or stream that QuickTime can play can be used as a SMIL media element in QuickTime.

However, QuickTime cannot play a SMIL file that specifies media QuickTime cannot play, such as a Real Media stream or a WMV video file compressed with a codec not available in QuickTime. Similarly, a Real or Windows Media SMIL interpreter would probably be unable to play a SMIL file whose media elements include QuickTime-specific media elements, such as a VR panorama, a QuickTime movie compressed using Sorenson video, or a QuickTime movie containing interactive sprites or Flash tracks.

Using SMIL in QuickTime

By stitching together media elements using a text editor and SMIL syntax, you can build customized presentations from existing media—movies, slides, text, and audio recordings—and play them using QuickTime.

You can also use SMIL to combine media stored on a web server or a local disk with stored content on a streaming server (video on demand) or with live streams, both unicast and multicast.

Because SMIL documents are text files, you can generate customized QuickTime movies using another script, such as an AppleScript, Perl, or CGI script—anything that can generate text output.

For example, a common use of SMIL in QuickTime is to have a CGI or PHP script generate a SMIL file that tells QuickTime to display a programatically chosen advertisement before connecting the user to a live stream such as a radio broadcast.

Like other non-QuickTime file formats, SMIL files may or may not be associated with QuickTime in the user’s browser or operating system. Consequently, clicking a hypertext link to a .smil file, or double-clicking a SMIL file on the desktop, may launch QuickTime or some other SMIL player. To prevent this, you may want to save your SMIL presentations as QuickTime movies, or use HTML scripting, to ensure that your SMIL presentations play in QuickTime on the user’s system. This is described in detail in the section Playing SMIL Presentations in QuickTime.

SMIL Structure

SMIL is based on XML, which is more rigidly structured than HTML but uses the same familiar <tag> and </tag> syntax.

Because it is XML-based, SMIL tags are case-sensitive (always lowercase) and all tags have to be explicitly ended—either a tag is self-contained and ends with /> (<tagparameters=”values”/>), or there are a pair of open and close tags that may enclose other elements (<tagparameters=”values”>elements</tag>).

Unlike HTML, SMIL does not routinely mix structure and content together in the same document; a SMIL file contains only structure and the URLs of content. Where an HTML document typically contains body text, for example, a SMIL document would contain the URL of a text file instead.

Like HTML, a SMIL document has a head and a body. The structure of a SMIL file is shown in listing 1-1.

Listing 2-1  SMIL structure

<smil>

    <head>

        <layout>

            <!-- layout tags -->

        </layout>

    </head>

    <body>

        <!-- body tags -->

    </body>

</smil>

All the layout information is specified in the head. This determines where things can be displayed on the screen. Some or all of the screen is divided into any number of rectangular regions, which may partly or completely overlap. The media elements are listed in the body, which is also where the temporal sequencing is specified. Visual elements in the body are assigned to a region (defined in the head) where they are to be displayed.

<layout>

    <root-layout id="main" width="320" height="240"

    background-color="red" />

</layout>

<smil>

    <head>

        <layout>

            <root-layout id="main" width="320" height="240"

            background-color="red" />

        </layout>

    </head>

    <body> </body>

</smil>

Regions

The layout also defines regions within the display area. Regions themselves are invisible, but they define areas where visual media elements can be displayed. Regions can be positioned anywhere in the display area and can overlap, as shown in Listing 1-3.

Listing 2-3  Layout with root layout and two regions

<head>

<layout>

<root-layout id="main" width="320" height="240"

background-color="red"/>

<region id="r1" width="160" height="120" />

<region id="r2" width="50%" height="100%"

left="100" top="0" />

</layout>

</head>

The first region is named r1, and is 160 x 120 pixels, extending from the top-left corner of the display area (the default position for a region).

The second region, r2, is half as wide as the display area (width=”50%”) and fills it from top to bottom (height=”100%”). Region r2 is offset 100 pixels from the left edge of the display area (left=”100”). Since the first region is 160 pixels wide, the two regions overlap by 60 pixels.

The top-left corner of a media element is always aligned with the top-left corner of the region it is displayed in. If you need to position an image somewhere else, just create another region at a different position—you can have as many regions as you like, and each one uses only a few bytes.

The <region/> tag accepts the following parameters:

• id—gives each region a name, much like an HTML frame name.

• height and width—define the size of the region, either in pixels or as a percentage of the display area.

• top and left (optional)—specify the position of the region within the display area, either in pixels or as a percentage of the display area.

  By default, a region extends from the top-left corner of the display area. You can change this by specifying a top and left offset. For example, top=”50%”left=”100” creates a region whose top-left corner is halfway down and 100 pixels from the left edge of the display area.

  If you set the top or left parameter, you must specify bothtop and left as a pair, even if one of them is zero.

• z-index (optional)—specifies the layering order when regions overlap.

  When regions overlap, one lies on top of the other. By default, a region defined later in the layout is on top of any regions defined earlier. You can set the layering explicitly using the z-index parameter. The layer with the highest z-index value is on top. The following example defines three regions with explicit z-axis values.

<region id="r1" width="160" height="120" z-index="3" />

<region id="r2" width="160" height="120" z-index="2" />

<region id="r3" width="160" height="120" z-index="1" />

The three regions overlap completely, with r1 on top, r2 in the middle, and r3 at the bottom of the pile. If no z-index values had been specified, the layering would be reversed, with the last-defined region on top.

• fit (optional)—defines how media elements are cropped or scaled if they have pixel dimensions different from the region they’re displayed in. There are four possible values for this parameter:

  • fit=”hidden” (default)—images are not scaled. If an image is larger than the region, it is cropped. If an image is smaller than a region, part of the region is left empty.

  • fit=”fill”—images are scaled to match the height and width of the region, so an image always fills the region completely. The image’s aspect ratio may be distorted to make it fit.

  • fit=”meet”—images are scaled to meet the region’s boundaries while preserving each image’s aspect ratio, without cropping. An image may not fill the region completely, but always fills either the whole width or the whole height. The image is not cropped or distorted.

  • fit=”slice”—images are scaled to fill the region completely while preserving each image’s aspect ratio, cropping if necessary. If the aspect ratio of an image differs from the region, the image is cropped by taking a slice from the edge or bottom where it would extend beyond the region.

Unlike HTML, scaling and cropping are applied to regions, not images. If you want to display different images on the same part of the screen, using different fit settings, create more than one region with the same area and x,y coordinates, but different fit values, and assign each image to the appropriate region. Create as many regions as you need.

Listing 1-4 is a SMIL document with two overlapping regions. It looks like a red rectangle when you play it using QuickTime Player, because regions are invisible; they just define areas where media elements can be displayed.

Listing 2-4  SMIL with overlapping regions

<smil>

<head>

<layout>

<root-layout id="main" width="320" height="240"

background-color="red"/>

<region id="r1" width="160" height="120" />

<region id="r2" width="50%" height="100%" left="100"

top="0" fit="fill" />

</layout>

</head>

<body> </body>

</smil>

<seq>

    <audio src="audio1.mp3" />

    <audio src="audio2.aiff" />

    <audio src="audio3.wav" />

</seq>

<seq>

    <img src="image1.jpg" region="r1" dur="5 sec" />

    <img src="image2.gif" region="r1" dur="7 sec" />

</seq>

<par>

    <audio src="themesong.mp3" />

    <img src="poster.jpg" region="r1" dur="30 sec" />

    <text src="lyrics.txt" region="r2" dur="30 sec" />

</par>

<seq>

    <video src="Intro.mov" region="r1" />

    <par>

        <audio src="narration.aiff" />

        <video src="slides.mov" region="r1" />

    </par>

    <text src="credits.txt" dur="20 sec" region="r1" />

</seq>

<seq>

    <par>

        <img src="slide1A.jpeg" region="left" dur="30 sec" />

        <img src="slide1B.jpeg" region="right" dur="30 sec" />

    </par>

    <par>

        <img src="slide2A.jpeg" region="left" dur="30 sec" />

        <img src="slide2B.jpeg" region="right" dur="30 sec" />

    </par>

.

.

.

</seq>

<par>

    <seq>

        <img src="slide1A.jpeg" region="left" dur="30 sec" />

        <img src="slide2A.jpeg" region="left" dur="30 sec" />

.

.

.

    </seq>

    <seq>

        <img src="slide1B.jpeg" region="right" dur="30 sec" />

        <img src="slide2B.jpeg" region="right" dur="30 sec" />

.

.

.

    </seq>

</par>

SMIL Media Elements

SMIL media elements are classified by type and specified by URL. Each visual media element is assigned to a region defined in the layout. The media type, the URL, and the region for visual media must be specified. All other parameters are optional.

<audio src="http://www.myserver.com/path/myaudio.mp3" />

<video src="rtsp://streamserver.com/VideoOnDemand.mov"/>

<img src="slides/slide01.jpg" />

<text src="subtitles.txt" />

<textstream src="rtsp://streamserver.com/streamtext.mov" />

<animation "http://www.myserver.com/myanim.flc" />

<text region="aregion" dur="1:30" src="data:text/plain,Copyright Apple Computer, 2000" />

<smil>

<head>

    <layout>

        <root-layout id="slideshow" width="320" height="240"

            background-color="black"/>

        <region id="r1" width="100%" height="100%" fit="meet" />

    </layout>

</head>

<body>

    <seq>

    <img src="http://www.myserver.com/ourlogo.jpg"

        region="r1" dur="5sec" />

    <img src="slide1.jpg" region="r1" dur="5sec" />

    <img src="slide2.jpg" region="r1" dur="5sec" />

    </seq>

</body>

</smil>

<img src="slide1.jpg" region="r1" dur="30sec" />

<audio src="sound1.wav" dur="1:05" />

dur="00:00:05.000"

dur="00:05.000"

dur="05.000"

dur="05"

dur="5 Sec"

<img src="slide1.jpg" region="r1" begin="5sec"/>

<img src="slide1.jpg" region="r1" begin="5sec" end="35sec" />

"id(idname)(event)"

<par>

    <audio src="themesong.mp3" id="x" />

    <img src="poster.jpg" region="r1" end="id(x)(end)" />

    <text src="lyrics.txt" region="r2" end="id(x)(end)" />

</par>

<par>

    <audio src="Sound1.aif" id="master" />

    <audio src="Sound2.aif" begin="id(master)(5sec)" />

    <audio src="Sound3.aif" end="id(master)(end)" />

</par>

 <video src="some.mov" region="movieregion"

     clip-begin = "npt=0:04"

     clip-end = "npt=1:01"

 />

SMIL HREF Links

You can make any visual media element in a SMIL document into a clickable link by using the <a></a> tags. You can direct the URL to load in a browser window or to replace the current SMIL presentation.

To make a visual element into a link, take the following steps:

• Precede the element with the <a> tag.

• Put the URL of the link in the href parameter of the <a> tag.

  • Set the show parameter of the <a> tag to new or replace.

  • Follow the element with the </a> tag.

In the following example, the Apple website loads in the default browser window if the user clicks in region r1 while poster.jpg is being displayed.

<a href="http://www.apple.com/" show="new" >

    <img src="poster.jpg" region="r1" dur="00:05" />

</a>

The show parameter can have two possible values:

• show=”replace”—replaces the current SMIL presentation in the plug-in or QuickTime Player (whichever is active). In this case, the URL must specify something that QuickTime can play.

• show=”new”—opens the URL in the default browser window. In this case, the URL can specify a web page or anything the browser or one of its plug-ins can display.

You can use show=”new” to target a specific browser frame, specific browser window, or QuickTime Player, using the target SMIL extension. Refer to the section QuickTime SMIL Extensions, for more information.

QuickTime doesn’t currently allow you to jump to a named point in SMIL presentations—you can’t use URLs of the form href=name.smi#name or href=#name.

Dynamic SMIL Elements

You can automatically present different elements to different viewers using the <switch></switch> tags.

SMIL supports a set of user attributes, such as screen resolution, color depth, maximum data rate, and language. Groups of elements can be listed between <switch> and </switch> tags. QuickTime selects one element from the list based on user attributes, much like QuickTime’s alternate track and alternate movie mechanism.

This can be used to select an audio track based on language, as shown in the following example:

        <switch>

            <audio src="french.aif" system-language="fr"/>

            <audio src="german.aif" system-language="de"/>

            <audio src="english.aif" system-language="en"/>

        </switch>

This example selects french.aif for French speakers, german.aif for German speakers, and english.aif for English speakers.

The <switch> element selects the first item in the list that matches the user’s system attributes. If you select an item based on connection speed, order the elements from highest speed to lowest speed—QuickTime loads the first element whose requirement is less than or equal to the viewer’s connection speed, as illustrated in the following example:

<switch>

    <audio src="192k.mp3" system-bitrate=192000"/>

    <audio src="128k.mp3" system-bitrate="128000"/>

    <audio src="qdesign.mov" system-bitrate="28800"/>

</switch>

To provide a default, make the default the last item in the list and don’t specify a required attribute. It’s usually a good idea to include a default, as there may be cases you haven’t allowed for explicitly. The following example selects french.aif for French speakers, german.aif for German speakers, and english.aif for all others.

        <switch>

            <audio src="french.aif" system-language="fr"/>

            <audio src="german.aif" system-language="de"/>

            <audio src="english.aif"/>

        </switch>

QuickTime supports the following user attributes:

• system-bitrate—corresponds to the user’s connection speed in the QuickTime Settings control panel. The QuickTime settings are specified in kilobits per second, but system-bitrate is set in bits per second, so multiply the QuickTime setting by 1000 to get the correct system-bitrate. For example, the correct system-bitrate for QuickTime’s “56 Kbps Modem/ISDN” is 56000 and the system-bitrate corresponding to “256 Kbps DSL/Cable” is 256000.

• system-screen-size—the minimum required screen resolution in pixels. The resolution is specified by HEIGHTxWIDTH. Note that this is contrary to common usage—a 640 x 480 minimum screen resolution is specified by setting system-screen-size=”480x640”.

• system-screen-depth—the minimum required color depth, in bits. Common values are 8 (256 colors), 16 (thousands of colors), and 24 (millions of colors).

• system-language—corresponds the user’s system language setting. The language is specified by a two-character code matching the ISO 639 language code specification, such as these:

  • Arabic—AR

  • Chinese—ZH

  • Danish—DA

  • Dutch—NL

  • English—EN

  • French—FR

  • German—DE

  • Greek—EL

  • Italian—IT

  • Japanese—JA

  • Korean—KO

  • Persian (Farsi)—FA

  • Polish—PL

  • Portuguese—PT

  • Russian—RU

  • Spanish—ES

  • Swahili—SW

  • Swedish—SV

For additional language codes, refer to http://www.oasis-open.org/cover/iso639a.html

Structural Elements Supported in QuickTime

• <smil></smil>

• <head></head>

• <layout></layout>

• <root-layout></root-layout>

  • height

  • width

  • id

  • background-color

• <region/>

  • height

  • width

  • top

  • left

  • z-index

  • fit (hidden,fill,meet,slice)

• <body></body>

• <seq></seq>

• <par></par>

Media Elements Supported in QuickTime

QuickTime supports the following media elements. Media typing in SMIL is not strict, so media types that do not have an exact match in SMIL, such as Flash and VR, can be labeled as animation or video in a SMIL file.

• <audio/>

• <video/>

• <img/>

• <text/>

• <textstream/>

• <animation/>

Media elements can contain the following attributes:

• src

• id

• region

• dur

• begin

• end

• clip-begin

• clip-end

If used inside a <switch> element, media elements can contain the following attributes as system requirements:

• system-language

• system-bitrate

• system-screen-size

• system-screen-depth

Dynamic Elements supported in QuickTime

QuickTime supports the following dynamic SMIL elements.

• <a></a>

  • href

  • show (new,replace)

  • target

• <switch></switch>

  • system-language

  • system-bitrate

  • system-screen-size

  • system-screen-depth

SMIL Root Element Attribute Extensions

The QuickTime SMIL extensions define the following additional attributes for the <smil> element:

autoplay

Specifies whether the presentation should automatically start playback. Legal values are true or false. The default is false. Common usage:

<smil xmlns:qt="http://www.apple.com/quicktime/resources/smilextensions"

qt:autoplay="true"/>

next

Specifies to the player that after this presentation is finished, the presentation referenced in the attribute value should be invoked and played in the same space. Used to chain presentations together. A valid attribute value is any URL. This capability is equivalent to the QuickTime browser plug-in’s qtnext attribute. The following example shows common usage:

<smil xmlns:qt="http://www.apple.com/quicktime/resources/smilextensions"

qt:next="nextpresentation.smi"/>

time-slider

Specifies whether a time-slider or “scrubber” should be included in the user interface. Legal values are true or false. The default is false. Because QuickTime normally loads SMIL media elements dynamically as needed, the known duration of the overall media presentation can change as a movie is played or navigated. This can be confusing to the user, as the current time indicator may jump around, speed up, or slow down unexpectedly. Consequently, the time-slider is not normally displayed in SMIL presentations. The time-slider can still be a valuable tool for navigating a presentation, however, and can be enabled by setting the time-slider attribute to true. You can modify the behavior of the time-slider using the immediate-instantiation attribute and the chapter-mode attribute. The following example shows common usage:

<smil xmlns:qt="http://www.apple.com/quicktime/resources/smilextensions"

qt:time-slider="true"/>

chapter-mode

Specifies the behavior of the time-slider (if it is included in the user interface by setting the time-slider attribute true). Legal values are all or clip. The default value is all.

In all mode, the time-slider can be used to navigate through the entire presentation and shows the current time in the presentation timeline as a whole. The time-slider represents the entire duration of the presentation, which is the sum of the durations of all elements in all sequences (the duration of a parallel group is the duration of the longest element in that group).

In clip mode, the time-slider can be used to navigate within the currently playing element and shows the current time within that element. The time-slider represents the duration of the current element in the sequence, or the duration of the longest element in the current parallel group.

The clip setting is useful for long presentations where the granularity of the timeline may be unacceptably low. It is also useful for network-based presentations, particularly those using streaming media, where the actual duration of a movie isn’t known until it has started to play. The example that follows shows common usage:

<smil xmlns:qt="http://www.apple.com/quicktime/resources/smilextensions"

qt:chapter-mode="clip"/>

immediate-instantiation

Specifies whether the media objects within the presentation should be instantiated immediately (at the time the presentation itself is instantiated), or whether instantiation should be deferred until the element is about to be played. Legal values are true (immediate) or false (when needed). Default is false. Instantiation means getting an instance of an object ready to play, and may involve opening or downloading a file, opening a stream, and importing a non-QuickTime media type into QuickTime.

The value of this attribute may be set on a per-media-object basis, using it as an attribute of individual media-object elements, as described in the following section, or as an attribute of the presentation as a whole, as shown in the following usage example.

Setting the immediate-instantiation attribute to true in the <smil> element causes all media objects used in the presentation to be instantiated immediately; this can make it easier for QuickTime to correctly determine the duration of the presentation before it begins, making the time-slider behavior more consistant. However, to instantiate all of the presentation elements at once can take considerable time and memory, particularly for a complex presentation or one being loaded over an Internet connection. Therefore, it is recommended that this attribute be used in the <smil> element only after careful consideration and testing. Common usage:

<smil xmlns:qt="http://www.apple.com/quicktime/resources/smilextensions"

qt:immediate-instantiation="true"/>

Media Object Attribute Extensions

The QuickTime SMIL extensions define the following additional attributes for SMIL media elements.

composite-mode

Specifies how to composite a visual media element against the background color and visual media elements in overlapping regions that are lower on the z-axis. Media objects may be opaque, partly transparent, or translucent to varying degrees. This attribute’s value is a combination of a text string identifying the mode and an optional semicolon followed by a second parameter, which varies depending on the mode. The composite-mode SMIL attribute is equivalent to the graphics mode property of a QuickTime video track. Possible modes are:

• copy, none, direct—Any of these three values specify that the element is opaque. Elements below it on the z-axis are completely obscured where the elements overlap. This is the default mode for most image formats (a GIF with a designated transparent color defaults to transparent-color mode; a Photoshop image with an alpha channel defaults to alpha mode).

• blend;percent—Specifies a weighted blend between the image and the background, with the degree of opacity specified by an integer percent value (for example composite-mode=”blend;50%”). Elements lower on the z-axis are partly visible through the current element, determined using a blend algorithm. A setting of 100% makes an object completely opaque, 0% makes it completely transparent.

• transparent-color;color—Specifies that all pixels of a particular color within the image should be treated as transparent. Accepts a second parameter, color, which specifies the color value to be rendered as transparent. The color parameter may be any valid color specification supported by Cascading Style Sheets Level 2, such as red, #ff0000, #f00, rgb(255,0,0), or rgb(100%,0%,0%). Elements lower on the z-axis are visible through any transparent pixels.

• alpha,straight-alpha,premultiplied-white-alpha,premultiplied-black-alpha—Specify that the image has an internal alpha channel that should be used when compositing. The values alpha and straight-alpha refer to a separate alpha channel; the premultiplied modes are used for images that have been premultiplied with an alpha channel against a white or black background, respectively. Elements lower on the z-axis are visible to the degree specified by the alpha component of each pixel.

• straight-alpha-blend—Specifies that the image has an internal alpha channel as a separate component, and that the alpha weight should also be multiplied by a percentage blend value, which is specified by a second parameter, with 0% meaning completely transparent and 100% meaning unmodified alpha. This has the effect of adding a degree of translucence to the object as a whole, in addition to any graduated translucence specified in the alpha channel.

Example usage:

    <img src="test.png" qt:composite-mode="alpha" />

    <img src="test.png" qt:composite-mode="blend;20%" />

    <img src="test.png" qt:composite-mode="transparent-color;#0e1d0f" />

    <img src="test.png" qt:composite-mode="straight-alpha-blend;10%" />

immediate-instantiation

Specifies whether this element should be instantiated immediately when the SMIL presentation is instantiated, or whether instantiation should be deferred until this element is about to be presented. Legal values are true or false. Default is false. Instantiation may require opening or downloading a file, opening a stream, and importing a non-QuickTime media format into QuickTime. Immediate instantiation may add to the time and memory required to begin the presentation, but may also ensure a seamless presentation once display begins. See also: bitrate. Example usage:

    <img src="bkgimage.png" qt:immediate-instantiation="true" />

bitrate

Specifies the bitrate at which a media object would need to be transmitted in order to play back in real time. This is used to allow QuickTime to estimate how far in advance it should attempt to read a deferred-instantitation media object in order to provide seamless playback. Possible values are positive integers, in units of bits-per-second. Example usage:

<video src="stream56k.mov" qt:bitrate="56000" />

system-mime-type-supported

Specifies to the player the MIME type that needs to be supported in order to be able to play back this particular media-object. This is distinct from the the type attribute because it is used in conjunction with the <switch> element in SMIL (in the same manner as system attributes such as system-bitrate). Legal values are character strings matching a valid MIME type. Example usage:

<switch>

<img src="qt.mov"qt:system-mime-type-supported="video/quicktime"/>

<img src="someother.suffix"qt:system-mime-type-supported= "some-other/mime-type"/>

</switch>

attach-timebase

Determines whether a child movie has an independent timebase or is linked to the timebase of the parent movie. (Each media element is loaded into QuickTime as a child movie. The parent movie is the SMIL presentation as a whole.) Default is true, which slaves the child’s timebase to its parent’s. This means the play/pause buttons control both the child movie and the SMIL presentation. Setting attach-timebase to false makes the child independent, which can be useful for allowing the user to interact directly with child movies, particularly multiple child movies within a parallel element. Be aware that when attach-timebase is set false, the play/pause controls do not affect the child movie, so you may need to provide some other method of control, such as sprites with wired actions. Example usage:

    <img src="movie2.mov" qt:attach-timebase="true"/>

chapter

Specifies a chapter name to attach to this particular media object, which then may be used by the player to provide a higher-level navigation UI than a simple linear control. A list of chapters appears in the control bar, allowing the user to jump to the beginning of any chapter. The beginning of the media element is the beginning of a chapter. Legal values are a character string (display of long strings may be truncated unless the movie is very wide). Example usage:

    <img src="movie1.mov"qt:chapter="Chapter 1--Intro"/>

Playing SMIL Files on the Desktop

To play a SMIL file in QuickTime, it must be given a file extension that QuickTime is registered to play, prefereably .smi or .smil. Such a file can be dragged onto the QuickTime Player icon or opened in QuickTime Player by choosing Open from the File menu.

Double-clicking a SMIL file may or may not open the file in QuickTime Player. It depends on what application has most recently registered for the SMIL file type with the user’s operating system. For example, installing RealPlayer typically makes it the default SMIL player. On Macintosh computers, the application registered as the file creator generally takes precedence when a file is double-clicked, so a SMIL file may open in the text editor used to create it.

To be certain that a SMIL presentation will open in QuickTime Player when double-clicked from the desktop, drag the file onto the QuickTime Player icon and save as a self-contained movie (requires QuickTime Pro). This saves the movie data structure that results from importing a SMIL file. It should always open in QuickTime Player, and should open considerably faster than a raw SMIL file, particularly a SMIL file with many structural elements.

You should be aware that a self-contained movie file saved from a SMIL presentation does not include the media elements referenced by the SMIL file. The movie is “self-contained” in the respect that it no longer relies on the original SMIL file. It remains dependent on the external media objects referenced in the SMIL file.

Playing SMIL Files in QuickTime from a Web Page

To play a SMIL file in QuickTime, a web browser must call either the QuickTime plug-in or ActiveX control, or the QuickTime Player application. Because multiple applications and plug-ins may be registered for the SMIL file type, you need to help the browser to choose QuickTime. There are several ways to do this.

The simplest method is to save the SMIL file as a QuickTime movie, as described in the previous section, Playing SMIL Files on the Desktop. You can then embed the SMIL file in a web page as you would any QuickTime movie. See “HTML Scripting Guide for QuickTime” for additional information.

Other methods of assisting a browser to choose QuickTime are somewhat browser-dependent. It is possible to combine methods to cover all common cases, however.

The most common browser is Internet Explorer for Windows (IE/Win). You can tell IE/Win to play media in QuickTime by using the <object> tag with the QuickTime class ID and code base. For example:

<OBJECT

CLASSID="clsid:02BF25D5-8C17-4B23-BC80-D3488ABDDC6B"

CODEBASE="http://www.apple.com/qtactivex/qtplugin.cab"

WIDTH="320" HEIGHT="256" >

<PARAM NAME="src" VALUE="My.smil" />

</OBJECT>

As shown in the example, the class ID for QuickTime is 02BF25D5-8C17-4B23-BC80-D3488ABDDC6B and the code base is http://www.apple.com/qtactivex/qtplugin.cab .

For all other browsers, you can use the QTSRC attribute in the <embed> tag. This requires you to embed a file in your web page that only QuickTime is registered to play, such as a QuickTime movie (.mov) or QuickTime image file (.qtif). The browser invokes the QuickTime plug-in to play the embedded file (the browser may also download the embedded file). The QuickTime plug-in recognizes the QTSRC attribute and loads the SMIL file, as shown in this example:

<EMBED

SRC="Some.mov"

QTSRC="My.smil"

WIDTH="320" HEIGHT="256"

PLUGINSPAGE="www.apple.com/quicktime/download"

TYPE="video/quicktime" />

Note that the PLUGINSPAGE and TYPE attributes tell the browser where to get the QuickTime plug-in and that this is a QuickTime movie file.

Note also that the file whose name is passed in the SRC attribute is not actually displayed, but that it may be downloaded by the browser. For this reason, it is best to pass the name of a very small QuickTime movie or QuickTime image file. You can make such a movie file by opening a single-pixel GIF in QuickTime Player and saving it as a self-contained movie.

The <embed> tag actually works with IE/Win, much as it does in other browsers, but IE/Win does not recognize the PLUGINSPAGE command. Consequently, if the <embed> tag is used alone, IE/Win does not offer to download QuickTime for users who need it. For this reason, it is recommended to combine both the <object> and <embed> tags. This provides a reliable user experience regardless of the user’s browser or operating system. Listing 1-8 provides an example.

Listing 2-8  Combining the object and embed tags

<OBJECT

CLASSID="clsid:02BF25D5-8C17-4B23-BC80-D3488ABDDC6B"

CODEBASE="http://www.apple.com/qtactivex/qtplugin.cab"

WIDTH="320" HEIGHT="256" >

<PARAM NAME="src" VALUE="My.smil" />

<EMBED

SRC="Some.mov"

QTSRC="My.smil"

WIDTH="320" HEIGHT="256"

PLUGINSPAGE="www.apple.com/quicktime/download"

TYPE="video/quicktime" />

</OBJECT>

Note that the <embed> tag must be closed with either a /> or a </embed> tag to work correctly inside an <object></object> tagset.

Other methods of playing a SMIL file in a web browser include using the HREF attribute to target QuickTime Player, using a QuickTime reference movie, and using an XML QuickTime Media Link file. For details, see “HTML Scripting Guide for QuickTime.”