Parallel Playlist

The SMIL parallel playlist is a list of media objects that start playback simultaneously.

Children of the parallel playlist can be specified to start at a specific "wallclock" time defined by the player's real-time clock. See the section on Wallclock for details.

Basic parallel playback

The following example will play both <seq> playlists at the same time. Each <seq> is playing in its respective region.

<par>
    <seq repeatCount="indefinite">
        <img src="pic1.jpg" dur="5s" region="main" />
        <img src="pic2.jpg" dur="5s" region="main" />
        <img src="pic3.jpg" dur="5s" region="main" />
    </seq>

    <seq repeatCount="indefinite">
        <img src="side1.jpg" dur="5s" region="side" />
        <img src="side2.jpg" dur="5s" region="side" />
        <img src="side3.jpg" dur="5s" region="side" />
    </seq>
</par>

Parallelism is effectively per region: children of a <par> targeting different regions run concurrently (as above), while media elements placed directly in a <par> but sharing the same region still play one after another — a region shows one element at a time. For parallel playback, structure the <par> as one child <seq>/<par> per region.

A classic a-smil pattern pairs a slide show <seq> with a background <audio> track inside the same <par>. The <audio> tag is not supported by the signageOS SMIL Player, though — see Not supported. Play the slide show as a plain <seq> instead; it will run silently.

Source: a-smil.org