1. A method of encoding video images, where each image has a frame type, the method executed by a computer and comprising: receiving a plurality of macroblocks for an uncompressed image; determining a macroblock type for each macroblock; determining whether the image represents a scene change based upon a distribution of macroblock types of the macroblocks and the frame type of the image, wherein the scene change is determined as a function of a percentage of prediction macroblocks in the image; encoding the image without changing the frame type of the image in response to the determination of a scene change and the frame type of the image; and outputting the encoded image.