1. A method of classifying a temporal sampling pattern of a sequence of images that represents a moving image, wherein an image in the sequence of images has an associated preceding image and an associated succeeding image, the method comprising: deriving a preceding inter-image pixel-value difference by subtracting the associated preceding image from the image; deriving a succeeding inter-image pixel-value difference by subtracting the image from the associated succeeding image; and classifying the image in the sequence of images according to a relationship between the preceding inter-image pixel-value difference and the succeeding inter-image pixel-value difference.