It is a window. They are filming in day time. Using maximum lighting.
The point the photo was taken from is below the reflection. For a flat wall, flat painting on the wall, with flat glass this means the reflection is of something above the painting (angle of incidence, blah, blah)- i.e. the Top of a window. You can see the curtain on the left of the reflection if you look closely.
t.photofag