White Film on Beer in Carboy
White film or flakes on top of beer is fairly common. It often happens in secondary, or in primary after the krausen falls.
Don't worry - your beer is probably fine!
Usually, this is the result of yeast colonies being carried to the top of the beer from the trub or yeast cake by CO2, although in some cases, it can be a sign of a bacterial or wild yeast infection.
Take a sample of the beer. Swirl it in a glass and see if it smells funky or infected. If you can't smell anything unusual, give it a taste. Does the beer taste sour?
If not, you just have rogue colonies of yeast on your beer. They may persist until you rack the beer, but should settle upon racking, and will not affect the smell, taste, or appearance of your final carbonated beer.
If the beer does smell/taste sour, then unfortunately, your beer has become infected. You'll probably have to scrap the batch. Scrub all equipment thoroughly with cleaner, and sanitize carefully before brewing again. If you ferment in a plastic bucket, ensure there are no scratches in the plastic, as they may harbor bugs. If there are scratches, replace the vessel.