The sockets in the video are BA15D and the circuit is from one spring pin to the other, with one filament in the bulb, power on one pin, ground on the other. This base uses an 1142 single filament bulb and is the bulb type you want if you want direct replacements in either LED or incandescent.
There is also a 1376 bulb that will physically fit the BA15D base, but has two filaments needing power at each pin and ground at the base. These will plug in but will not light in a typical marine wired BA15D base.
This is quite different from the more common BAY15D which looks the same but has two filaments with ground flowing through the bulb base and each filament powered by each individual pin. BAY15D has the two pins offset so you can only insert the bulb one way and uses an 1157 bulb, at first glance it looks like they would fit, but on closer examination, they won't. 1157 was a common taillight/stoplight bulb on cars before cars became giant plastic creations.