Generate images from AVAssetImageGenerator gives same image duplicates for different times

Question

I am trying to generate thumbnail images from a video using the following code. It does generate UIImages but the images are all the same at different time. For example, for

Answer 1

By default AVAssetImageGenerator gives itself very generous tolerances when fetching frames for a given time. If you use copyCGImage's actualTime you'll see in practice that it's something like one or two seconds, although technically it's kCMTimeFlags_PositiveInfinity, so in your short video half of your frames will be duplicates.

So set the tolerances to something smaller to see unique frames:

imageGenerator.requestedTimeToleranceBefore = CMTimeMake(1, 15)
imageGenerator.requestedTimeToleranceAfter = CMTimeMake(1, 15)