In PowerPoint, your inserted movie clip is always placed as in a traditional rectangular shape, which is exactly what most users expect since it does seem safe and conventional. However, PowerPoint 2011 allows you to crop your movie to various shapes such as a circle, an oval, a wave, a triangle, or any of PowerPoint’s default shapes. However, while selecting shapes for your movie clips, do remember that most of the shapes other than a Rectangle may crop out some parts of your movie clips. That’s why you can play around with shapes such as a rounded rectangle — but ponder a lot before you place a movie within a semi-circle or a pointed star!
Learn about Movie Shapes in PowerPoint 2011 for Mac.

