Checking for Updates

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It is often necessary to check for an update in the playlist while the current playlist is playing. To do that, simply use the "Refresh" meta tag as shown below. 

<smil>
  <head>
    <meta http-equiv="Refresh" content="60"/>
  </head>
  <body>
    ...
  </body>
</smil>

The playlist will reload itself every 60 seconds (or any specified interval).

Best Practice: Using Static SMIL File

You may be tempted to use a server-side script to dynamically feed your playlist to the players. However, the simplest and most scalable way to host the SMIL playlist is to store it as a static file on the server. Updates are applied to the file when user chooses to update the schedule. When you perform the update, make sure the change is "atomic" so that players will not download a partial SMIL while it is being updated. Create the new SMIL file separately, and renaming it to the name of the old SMIL version is one way to do this.

If you are using a server-side script as the "master entry point" for all your players, it is recommended that you use an HTTP "Location:" header to redirect your player to its corresponding SMIL file once you have determined the player's identity (see Player ID).

Using a Dynamic Server-side Script

If you must use a dynamic server-side script to generate your SMIL file, make sure you supply an HTTP "Last-Modified:" header so the player does not abruptly restart its playback each time it checks for an update. If the last modified time has not changed, SMIL player will not reload the file and therefore will not restart playback.

It is a good practice to support the header. Media feeds that are designed to serve a large user base typically support the Last-Modified: header, such as:

http://api.flickr.com/services/feeds/photos_public.gne 

---response begin---
HTTP/1.1 200 OK
...
Last-Modified: Wed, 18 Nov 2009 11:16:01 GMT
...

---response end---

Last-Modified: info is used by proxies to maintain their cache. Suppose 10,000 players access your playlist once every 10 minutes, it would not be wise to serve them via a live script (which would pull on YOUR SOURCE 1,000 times per minute, wasting lots of bandwidth and processor cycles).

Related

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