Captioning - Checkpoint (b)
The law states:
"Equivalent alternatives for any multimedia presentation shall be synchronized with the presentation."
Captioning allows your deaf users to understand multimedia content with audio. This guideline requires your text alternatives from Alternate Text to synchronize with the content. There are many tools to help you, especially a free tool called MAGPie. MAGPie allows you to caption windows media files.
Helpful Web Sites
NCAM MAGPie Video Captioning Tool