Encoder design for H.264/AVC based on contrast sensitivity considering spatio-temporal direction dependency

It is really important to use the proper coding mode in the H.264 encoder, since it offers many more modes than the conventional methods such as MPEG-2. Typical H.264 encoders like JM and JSVM use squared error as the criterion of distortion for mode decision. However, squared error does not always provide a correct measure of the distortion from the viewpoint of subjective quality. In this paper, we investigate a mode decision algorithm based on the spatio-temporal contrast sensitivity model in order to improve the H.264 encoder. Our algorithm is designed considering the direction dependency of spatio-temporal frequency. Experiments show that our method can achieve average bit-rate savings of the order of 4.0 to 5.5% compared to the original JSVM. We confirm that both methods yield reconstructed images that basically have the same subjective image quality.