We proposed a method for reducing LCD motion blur in MPEG domain and analyzing the cause of LCD motion blur. The problem of LCD motion blur is caused by slow response time of liquid crystal and hold-type displaying method of LCDs. The proposed method uses MPEG motion vectors and frequency coefficients of DCT blocks to improve the motion blurs. First, we interpreted the aperture and response time effect of LCD in frequency domain then, modeled sharpening mask filters for the compensation. We confirmed the reduction of motion blurs in LCDs by a motion image simulator.

We propose a method to retrieve similar and duplicate images from a JPEG (Joint Photographic Image Group) image database. Similarity level is decided based on the DCT (Discrete Cosine Transform) coefficients signs. The method is simple and fast because it uses the DCT coefficients signs as features, which can be obtained directly after partial decoding of JPEG bitstream. The method is robust to JPEG compression, in which similarity level of duplicate images, i.e., images that are compressed from the same original images with different compression ratios, is not disguised due to JPEG compression. Simulation results showed the superiority of the method compared to previous methods in terms of computational complexity and robustness to JPEG compression.