Accessiblity with Slide Overlays (overtop of video backgrounds)

Hello Everyone I am developing a Captivate presentation using interactive video backgrounds with slide overlays. However, I have learned that there is accessibility limitations.   Some of my clients use ‘screen readers’ because of a visual impairment.  (Jaws,  and Dragon) Is this the case?   Will screen readers no be able to pick up the overlay slide content when it sits on top of a video? Any tips to get around this would be greatly appreciated. Cheers Todd