Repetitive Filtering-Based Intra Prediction Scheme for HEVC

Abstract

In high efficiency video coding intra coding framework is built on the prediction of spatial sampling. Intra prediction is used in high efficiency video encoder to remove spatial redundancy. The intra prediction operates according to transform block size. The previously encoded boundary sample of the neighboring transform block is used as the reference pixel. The spatial redundancy is removed by predicting the pixels in the region of the coding block from the reference pixel. Copying-based method is used for intra prediction process in high efficiency video encoder (H.265). The proposed research work is carried out in two phases. In the first phase theoretical analysis of intra prediction block is performed with due consideration of the first-order Gaussian Markov model as a reference under two distinct conditions: 1. The pixel values differ from the model values to large extent and 2. The distance between the reference pixel and predicted pixel is too large. Both of these cases are evaluated by finding the correlation between reference pixel and coding block pixel. The coding gain is used as the performance parameter which indicates the prediction accuracy of the intra prediction process. The analysis shows that in both of these conditions the corresponding correlation is very weak and the coding gain declines, in such conditions prediction weight should be very small. In the second phase paper proposed an improvement to copying-based method in the second phase. The repetitive smoothing filter is added as an extra mode to the traditional copying-based method. The number of iterations of the filter is adaptively changed based on the correlation between the reference and block pixels. The repetitive filter with varying number of iterations number reduces the number of encoding bits up to 2.5% on high resolution video sequences. In the repetitive filtering number of times the filter is iterated is decided by the correlation between current and reference pixel. The significant reduction in the number of bits increases the coding gain of the high efficiency video encoder than the default value of the coding gain.