Intra-prediction with adaptive sub-sampling

Intra-prediction improves coding performance by reducing inter-pixel redundancy. However, to accommodate the use of block transforms, not all pixels can be predicted from reconstructed pixels that are located close to themselves. This causes prediction performance to suffer as pixel values further apart are less correlated. This paper presents additional intra-prediction modes designed with the goal of improving prediction performance. Experimental results show an average gain of about 2% in KTA when the new modes are incorporated in the current 8×8 prediction modes. Since the new coding modes (8×8) are designed with transform size smaller than coding block size, the modes can also be useful when the prediction unit is larger than the maximum transform size. The use of smaller transform sizes can potentially lead to reduction of decoder complexity and implementation costs.