ok 1.start by making the object editable
2.use the ploygon tool and select one side of the cube(it well change color)
3. with it selected go to the selection menu and click set selection,this will add a triangle in your objects tab next to the cube
4.in the attributes window name the selection whatever you want…like (side 1)
5.make your material with your pic or video in the color
6. drag it into the cube in the objects window
7. now in the attributes window ,where it says selection put in the name of the selections you made…..like (side 1 )
Do this for all sides one at a time..just make sure when doing your 2ed side of the cube ,when your going to set the selection{MAKE SURE THE FIRST SELECTION TRIANGLE IS NOT HIGHLIGHTED} OR IT WELL JUST ADD BOTH SIDES TO THE FIRST SELECTION …GOOD LUCK
cinema 4d