Intra prediction with spatial gradient
Shohei Matsuo, Seishi Takamura, Kazuto Kamikura, Yoshiyuki Yashima · Proceedings of SPIE, the International Society for Optical Engineering/Proceedings of SPIE · 2008
Spatial intra prediction has been added recently to the latest video coding standard H.264/AVC. In the intra prediction of H.264/AVC, there are 9, 9 and 4 prediction modes for 4×4, 8×8 and 16×16 blocks, respectively. Prediction signals are generated by using one or several reference pixels. The value of a reference pixel is copied as the prediction value. In some prediction modes, we calculate a weighted mean by averaging several pixels. The same prediction value is copied to several of the pixels lying in the prediction direction. However, if original image has patterns like gradations, the residual energy could increase which would result in low coding efficiency. In this paper, we propose a new intra prediction that generates prediction signals with a spatial gradient to deal with this problem. Simulation results show that it improves the picture quality and reduce the bit-rate by about 0.14 dB and 1.0 % on average for CIF sequences, respectively. It is also confirmed that our method is effective at high bit-rates.