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Chapter 10: Presentation Information

RealOne Player provides several means for delivering information about a presentation, such as its title, author, and copyright. This chapter covers these information features, and explains the accessibility features available for sight-impaired persons.

Understanding Presentation Information

There are several types of presentation information available. Some types augment other types, some types override other types, and some types are available only to viewers who have devices that read accessibility information.

Information Encoded in Clips

Many clips have their own encoded information. When you create a RealVideo or RealAudio clip, for example, you can have Helix Producer encode certain types of information into the clip. Some of this information is used only by Internet search engines, but some is read by RealOne Player. The following are the most common types of information encoded into clips for display by RealOne Player:

In general, it's good practice always to encode information in the clip. This ensures that important information, such as a copyright, is present if the clip is not streamed using SMIL. Encoded information is the most basic level of presentation information, but you can override it using SMIL.

For More Information: See the documentation for your production tool for instructions on how to encode information into a clip.

Clip Source Tag and Group Information

A SMIL clip source tag, such as <video/> or <ref/>, can define title, author, copyright, and abstract information for the clip. There are two main advantages to defining this information in SMIL:

You can also define title, author, copyright, and abstract information for groups. This information then overrides the information defined for the individual clips. When several clips play in parallel, for example, RealOne Player does not display the title for each clip individually. You may therefore want to define a single group title that RealOne Player displays while the group is active.

For More Information: The section "Adding Clip and Group Information" describes how to add information to clip source tags and group tags. For more on groups, see Chapter 11.

SMIL Presentation Information

Within a SMIL file, you can define information for the entire presentation. This information supplements the clip or group information, but does not override it. This enables you to present two-levels of information to viewers:

Like clip information, the presentation information can give the title, author, copyright, and abstract. But you can also define any other information you wish through the header section <meta/> tags.

For More Information: The section "Defining Information for the SMIL Presentation" explains how to write the <meta/> tags.

Accessibility Information

The accessibility features define a different class of information. RealOne Player typically does not display this information. Instead, the information is read by assistive devices used by sight-impaired persons. This information can help these viewers choose which clips to play, and which links to click.

For More Information: See "Adding Accessibility Information" for more information on these features.

RealOne Player Related Info Pane

RealOne Player has a built-in related info pane meant for displaying information as a presentation plays. Through SMIL, you can open HTML pages in the related info pane at any point in a presentation. This HTML page can augment the presentation information described in this chapter.

For More Information: See "Opening HTML Pages in the Related Info Pane" for more information.

Coded Characters

In a SMIL header section, or within clip attribute values, quotation marks, apostrophes, ampersands, and angle brackets are interpreted as syntax markers. You need to use codes to have these characters show up as text in RealOne Player. As shown in the following table, codes begin with an ampersand ("&") and end with a semicolon (";"). SMIL interprets these codes the same way as popular Web browsers.

SMIL Coded Characters
Code Character Example
&quot; quotation mark "
&amp; ampersand &
&apos; apostrophe '
&lt; left angle bracket ("less than" sign) <
&gt; right angle bracket ("greater than" sign) >

For example, to add the following as a title:

Multimedia's <smil> & you

You enter this in the SMIL file:

"&quot;Multimedia&apos;s &lt;smil&gt; &amp; you&quot;"

Adding Clip and Group Information

The SMIL title, author, copyright, and abstract attributes let you add information to clip source tags and the <seq> and <par> group tags. This information overrides any similar information encoded within the clip itself. The following table summarizes these descriptive attributes.

Clip and Group Information Attributes
Attribute Value Function
abstract clip_abstract Sets a summary displayed in the "Now Playing" list.
author author_name Defines the author name.
copyright copyright_notice Provides a copyright notice.
title title_text Creates a title for the "Now Playing" list.

Each attribute takes a text string for its value. The following example shows the general form these attributes take in a clip source tag:

<ref src="..." title="title" author="name" copyright="date" abstract="abstract"/>

Where Title, Author, and Copyright Information Displays

Whether information is encoded in the clip, or added through SMIL or a Ram file, it appears in the following areas of RealOne Player:

Using Clips Within Groups

When you have a sequence of individual clips, you can display title and author information in the "Now Playing" list by omitting a <seq> tag, as described in "Creating Sequences Without Sequence Tags". When you leave the <seq> tag out, as shown in the following example, the individual clip titles display in RealOne Player:

<body>
<audio id="clip1" title="This is Clip 1" .../>
<audio id="clip2" title="This is Clip 2" .../>
...
</body>

When you group clips within a <seq>, <par>, or <excl> tag, the clip titles are ignored. You should therefore add title, author, and copyright information to the group tag, as shown in the following example:

<body>
<seq title="This is Sequence 1">
<audio id="clip1" .../>
<audio id="clip2" .../>
...
</seq>
</body>

As these examples illustrate, the use of <seq> and <par> tags affects whether group or clip information displays in RealOne Player. This, in turn, affects whether viewers can select parts of the SMIL presentation through clip or group listings in the "Now Playing" list:

Defining Information for the SMIL Presentation

Whereas clip source tags and group tags can define information about each clip or group, the SMIL file header can use <meta/> tags to define information, such as title, author, and copyright, for the entire presentation. Each <meta/> tag uses two attributes, name and content, as shown in the following example, which defines title, author, and copyright information:

<head>
<meta name="title" content="Bob and Susan Discuss Streaming Media"/>
<meta name="author" content="RealNetworks Media Productions"/>
<meta name="copyright" content="(c)2001 RealNetworks"/>
</head>

Tip: Name values, as in name="title", must be lowercase. When defining long content such as an abstract, don't use line breaks or tabs within a content value.

The presentation information displays in the following areas of RealOne Player:

Presentation Information

Presentation Information

Example of Presentation and Clip Information

The following SMIL example defines both presentation and clip information:

<smil xmlns="http://www.w3.org/2001/SMIL20/Language">
<head>
<meta name="title" content="Bob and Susan Discuss Streaming Media"/>
<meta name="author" content="RealNetworks Media Productions"/>
<meta name="copyright" content="(c)2001 RealNetworks"/>
</head>
<body>
<video src="clip1.rm" title="Bob Expounds His View"/>
<video src="clip2.rm" title="Susan Responds with Another Perspective"/>
<video src="clip3.rm" title="Summary: A Look at the Future"/>
</body>
</smil>

Because the sequence of video clips does not use a <seq> tag, the individual clip titles display in the "Now Playing" list, indented below the presentation title, as shown in the figure "RealOne Player `Now Playing' List".

Adding Accessibility Information

Although the clip, group, and presentation information attributes always display in RealOne Player, the accessibility attributes function only with assistive reading devices used by visually impaired viewers. The following table summarizes the attributes that help make your presentation accessible to all viewers. RealNetworks encourages you to add these attributes to your presentation.

Accessibility Attributes
Attribute Value Function Reference
alt text Provides alternate text. click here
longdesc text Gives a long description to assistive reading devices. click here
readIndex integer Sets the order in which clip information is read. click here

Including an Alternate Clip Description

Each clip source tag can include an alt attribute that uses short, descriptive text as its value. This alt value displays in RealOne Player when the viewer moves the screen pointer over the clip. It is good practice always to include an alt attribute for each clip. In the following example, the text "Introductory Video" displays when the viewer moves the screen pointer over the clip:

<video src="video1.rm" alt="Introductory Video"/>

Note: Unlike browsers that display image alt text before the images are downloaded, RealOne Player does not display alt text for clips before they play.

Tip: If the clip includes hyperlinks, the link's alt value or URL displays in place of the clip's alt text. For more on alt in hyperlinks, see "Displaying Alternate Link Text".

Using a Long Description

Each source tag can include a longdesc attribute that supplements the alt attribute. Some assistive-reading devices can read this long description for visually-impaired viewers. If you turn the clip into a hyperlink as described in Chapter 15, the description should describe the link destination. Here is an example:

<img src="button3.gif" longdesc="This is the third navigation button. Clicking it opens your browser to the home page for RealNetworks." .../>

Setting the Clip Read Order

When a visually-impaired viewer uses an assistive-reading device, the device typically reads the values of the title, alt, and longdesc attributes in each clip source tag. When clips play in parallel, the device reads the attributes in the order that the clip tags appear in the <par> group. To change this order, you can add readIndex attributes to the clip source tag. Each readIndex attribute, which has a default value of 0, takes a positive integer as a value. Here is an example:

<par>
<img ... alt="Link Button 1" longdesc="Start next video" readIndex="1"/>
<img ... alt="Link Button 2" longdesc="Visit home page" readIndex="2"/>
<video ... alt="Presentation Video" readIndex="0"/>
</par>

In the example above, the video source tag has the lowest readIndex value, so an assistive device reads that clip's alt attribute information first. Next, the device reads the first image's alt and longdesc attributes, followed by the second image's alt and longdesc attributes.

Note: If two or more source tags have the same readIndex value, clip information is read according to the order that the clip source tags appear in the markup.

For More Information: The section "Playing Clips in Parallel" describes parallel groups.


RealNetworks, Inc. ©2002 RealNetworks, Inc. All rights reserved.
For more information, visit RealNetworks
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