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Introduction

The purpose of intra prediction is to eliminate the space relationship of current picture. Before H264, there are almost no 'modern' intra prediction. Usually use DC prediction (MPEG2/MPEG4) and AC prediction (MPEG4) to act as intra prediction. Another purpose of intra prediction is that he prediction process does not depend on other picture. Current picture could complete the intra prediction by it itself. So intra prediction are use for Intra (I) frame, which be used as anchor frame for the following decoding. The following inter prediction frame will use it as reference. The H264 introduce several mode for intra predition which different according to block size.

4x4 Intra Prediction

9 types of intra prediction for 4x4 mode

4 types of intra prediction for 16x16 (luma) and 8x8 (luma when 8x8 transform enabled and chroma) mode

• Mode 0 (vertical): extrapolation from upper samples (H).
• Mode 1 (horizontal): extrapolation from left samples (V).
• Mode 2 (DC): mean of upper and left-hand samples (H+V).
• Mode 4 (Plane): a linear “plane” function is fitted to the upper and left-hand samples H and V. This works well in areas of smoothly-varying luminance.