Writing SMIL

Writing SMIL can in some ways make accessibility seem more difficult. For questions, this web page is helpful. Here is a bit on what they have to say about text timing:

“27.4.5.1. Time containers

Media elements are placed in special time container elements (<par>, <seq>, and <excl>) that define how the media should be played. The <par> element (short for “parallel”) defines a group of elements that play at the same time. The <seq> element defines a sequence of elements that play one after another, in the order in which they appear in the SMIL document.

When media elements are placed in the <excl> time container (short for “exclusive”), only one of those media elements can play at any given time.
27.4.5.2. Time control attributes

SMIL defines a number of attributes for indicating the specific timing of media elements and groups of elements (defined by time containers). Let’s take another look at the narrated slideshow sample from the beginning of this chapter:

<par dur=”15s”>
<audio src=”audio_file.mp3″ begin=”0s” id=”audio_1″ />
<seq>
<img src=”image_1.jpg” begin=”0s” />
<img src=”image_2.jpg” begin=”5s” />
<img src=”image_3.jpg” begin=”10s” />
</seq>
</par>

The dur attribute of in the <par> element specifies that the display of the elements in that group will have a duration of 15 seconds. The dur (duration) attribute can also be applied to specific media element tags. Some media, like audio and video, have implicit durations. Others, like text and images, require you to specify a duration. If you want an image to stay on throughout the presentation, set the value of dur to indefinite. ”

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