Judging wind speed based on flags and inland-water observations
I would call that about a force 3. But be aware that one of the problems near shore is that the shoreline, buildings, and topography have a large effect on the local winds - both direction and speed. Also fetch makes a difference - waves don't have enough time/space to build to their full size without sufficient fetch. Not the case in your video but it is difficult to evaluate waves when looking downwind because you see the less-steep backs of the waves and maybe only the tips of the whitecaps.

Sea kayakers have some decent resources for estimating winds near-shore because most kayakers spend the majority of their time in that environment. Here is one example.