14. The computer system of claim 13 , wherein the cost function comprises a target cost indicative of a difference between a visual feature vector in the visual feature vector sequence and a visual feature vector related to a real sample image.
14. The computer system of claim 13 , wherein the cost function comprises a target cost indicative of a difference between a visual feature vector in the visual feature vector sequence and a visual feature vector related to a real sample image. 15. The computer system of claim 14 , wherein the cost function comprises a concatenation cost indicative of a difference between adjacent real sample images in the sequence of real sample images.