Cumulus provides several ways of previewing assets:

Viewing an asset in Preview view or window lets you add user comments to it. In Fullscreen Preview you can compare up to six different assets and add labels and ratings. The Fullscreen Slide Show displays assets as fullscreen previews in a slide show. The Preview pane can be opened additionally at the left side of a collection window.

For the preview of video files, an appropriate player is used which provides usual controls (play/pause, stop, volume control, timeline, full screen, etc).