Captions displaying over shared screen powerpoint are often unreadable.

I can record a meeting on my computer, and I can see the captions are displayed, but when during the meeting a powerpoint has white background, but during playback the white captions are displayed in white and therefore invisible.   Need some way to have the captions displayed in an area of the playback screen that doesn't compete with the meeting video.  Is there a way to do that?  I've included an image showing the white captions overlaying the playback of a shared screen powerpoint.