Improved Linebased Image Coding by Exploiting LongDistance Correlations Linebased coding has shown its potential in improving the coding efficiency of intraframeimage coding due to its flexibility in prediction. In our previous work we proposed an efficient linebased image coding method (LIC) by adaptive linebyline prediction (ALP) and adaptive residue coding. In this paper we further improve this linebased coding scheme by exploiting longdistance correlations in prediction. Linebyline template matching (LTM) is introduced to perform the longdistance prediction. Experiments in the KTA software show that the LTM scheme can effectively improve the performance of LIC at low bitrates and also brings some improvement at high bitrates. Up to I db gain is achieved compared to previous LIC and 1.5db compared to KTA on images with regular patterns or strong edges. Up to 20% rate reduction over KTA is also achieved on some standard video sequences with different resolutions.

Rotational Weighted Averaged Template Matching for Intra Prediction Intra prediction is an important step in video coding, which improves compression efficiency by reducing spatial redundancy. High Efficiency Video Coding (HEVC) has a total of 35 prediction modes, including 33 angular modes and a DC mode as well as a Planar mode. These modes usually exploit local directional signal correlations. In order to represent prediction blocks with nonlocal complex texture and content, template matching was proposed. However, there may be blocks exist in an image with the same content but with different rotation angles. In this paper, we propose an improved intra template matching prediction method, which extends the intra template matching technique by making the matched template rotated during template matching process. Also, in order to improve the efficiency of prediction, this paper adopts a weighted template matching method to predict the target block by averaging sum of the weighted corresponding remote blocks of three most similar remote templates. The experimental results show that for AllIntra configuration, the overall coding gain in BDrate is about 5.1% at most and 0.63% on average comparing to averaged template matching in HEVC. Moreover, our approach can achieve 13.2% coding gain at most and 2.0% on average comparing to HEVC test model HM16.9.