Is it possible to change the shape of a video from rectangle to circular?

Not in Storyline. What you could do is drop the video into PowerPoint and crop to a circle. Then save the PPT slide as a .MP4. This will give you a video with a circle shape. However, the video bounding box is still rectangular. But visually it'll look like a circle.

In addition to Tom's excellent suggestion, you can leverage Storyline's ability to overlay embedded videos with other objects. Use the donut shape (Insert > Shape > Donut] to mask the video in a circle. Rough video of the steps is attached.

I am going to try both of these and see how they work in my project.  Thank you for the suggestions.  

Here are some examples of the cropping in PPT I used for a Rise demo a while back. I think they look nice, but you still have a rectangular video. 

Tom - I couldn't figure out how to send you just the one slide series of my project, so I made a document to show you my dilemma.  If I'm following everything correctly, I do not think what I ant to do is possible.  Please let me know what you think.

There's nothing in the doc

Tom,

Let’s see if it works as an attachment to this email.

Ann Jarrett 

Don't see an attachment. You also may want to edit this comment and remove your personal info.

Can you do a screen shot. Windows has a snipping tool and you can attach that.

Here is a PDF.  Is it possibly because it's coming from my dropbox and you need permission?  I will save on my desktop to try.

I believe either approach will work (you may have to make the width of the donut ring narrower and add some filled rectangles to fill any gaps). Assuming you're using layers to display each tab's information, you can just replicate the tab set on each layer so that they overlay the video or donut/rectangle mask.

Agreed.