With any on-demand session on BigMarker, you will decide whether or not users will need to register to view the video. If you decide to require registration, you'll also have an additional feature you can enable: Guest Viewing. To view these settings, head over to Basic Setup > Access and then into the On-demand tab.
When you enable guest viewing, you'll see an additional setting to determine the Guest viewing time limit. This will be the amount of time that users will be able to watch the video before having to register. The video will no longer play until they do so.
When enabled, guest viewing will affect the landing page as well as any widgets that you use outside of a BigMarker landing page.