Adding Audio descriptions with SMIL 1.0

This tutorial assumes that you already have audio description files, either as one long file or as several short files.

Writing the SMIL

The biggest challenge in adding audio descriptions is the timing. MAGpie 1.0 is a free tool which can be used to determine the exact times when audio descriptions need to be added. Once the exact times are determined, adding the necessary markup in the SMIL is easy.

Audio descriptions all in one continuous file:

If your descriptions are in one file, you will need to use 'clip-begin' and either 'dur' or 'clip-end' to set the starting and ending times for each description. The final <audio> tag in the example below assumes that the end of the last segment of "ad.wav" coincides with the end of the file.

<body>
  <par>
	  <video src="video.mpg" region="videoregion"/>
	  <audio src="ad.wav" begin="11.34s" clip-begin="0s" dur="2.3s"/>
	  <audio src="ad.wav" begin="20.12s" clip-begin="3.1s" dur="2.1s"/>
	  <audio src="ad.wav" begin="26.76s" clip-begin="6.4s" dur=1.1s"/>
	  <audio src="ad.wav" begin="32.94s" clip-begin="8.0s"/>
  </par>
</body>

Audio descriptions in separate files:

When descriptions are in separate files, you will need to add fewer attributes to each <audio> tag, but you wind up with a greater number of audio files. the markup below is the same as the markup above, except for the changes necessary to accommodate the separate files.

<body>
  <par>
	  <video src="video.mpg" region="videoregion"/>
	  <audio src="ad1.wav" begin="11.34s"/>
	  <audio src="ad2.wav" begin="20.12s"/>
	  <audio src="ad3.wav" begin="26.76s"/>
	  <audio src="ad4.wav" begin="32.94s"/>
  </par>
</body>

Back to Audio Descriptions in Rich Media