From the video it looks like it has been leaking for a while. There are lots of possibilities. I would start looking at the top of the engine first. It could be a heater hose, heater control valve, intake manifold gasket, head gasket, freeze plug in a head or the block. I think there are three freeze plugs on each side of the block, with one being above the starter. I would use a cooling system pressure tester, you can borrow one from many auto parts stores for free. This way you don’t have to have the engine running or a hot engine while trying to determine the source of the leak. You probably will have to remove the starter to get a better view.
