Not only is the timing calibrated, but also I think the setting (& a lot of the changes). The curtain change seems significant except that it's against a refle

Not only is the timing calibrated, but also I think the setting (& a lot of the changes). The curtain change seems significant except that it's against a reflective window with items visible behind in darkness - that lends itself to vague/semi-transparent objects being "acceptable" to the eye within that space. The blue & yellow picture and rug are also blurry/vague patterns which lend themselves to fading in/out. The ceiling is dirty off-white, lending itself to tiles being off-colour at times. The books on the shelves the same. The only very "finite" objects in the scene (and by far the easiest to notice changing) are the wine bottles.