You can make your Interactive Study Material available for a time window of your choosing. This is possible in the settings of you assignment by enabling the 'Deadlines & realtime control'.
You can choose to open and close the assignment manually, or you can schedule a date and time at which the assignment will automatically open and close for the students. It is also possible to open or close the assignment, they do not both have to be enabled.
The video will always be visible to the students, even before opening and after closing the assignment. Students contributions are affected by deadline control, below you can see an overview of how opening or closing affects the ability by students to contribute.