Interesting.  As far as the windows to the right, they appear to be in a section of the building which apparently is either a vestibule or room of some sort and built inward as you can detect by the wall coming into the room to the right of the "window".  I'm guessing you are correct about that being a window and it is also higher and much larger than the others (like a old time factory window – remember this is in China) and also quite high above the floor.  This could, in some way, also explain to a small degree why is there is difference in the natural light from those on the right from the larger one with the same light source.  Interesting also is the scale of the individuals to the window at the very end.  After looking at the clip, something about having these two individuals on camera somewhat throws up a red flag.  On the surface, they don't seem to have anything to do with this, but you only see a 1.07 minute clip – nothing before, nothing after except these two heading off to the right.  Another thing I noticed is, that if this is supposed to be a cctv camera, it's another case of how things are edited.  Note the differences in the shots.

I don't speak Chinese either but I think unless someone knows exactly where this building is located, it's surroundings, including how the building itself is physically situated in terms of the sun, etc., the type of building it is and any objects outside and/or attached to the building, it's very difficult to determine.  To me, if this is in fact an old building and especially if it's not actually "in use" since there is nothing around to tell what the building is or has been used for, it would make sense that the orbs are either dust thrown up or insects as you said.

All in all, it is a very interesting clip.  Thanks for putting it up for discussion Revenant.