A Novel Approach of Intra-Prediction Mode Selection in H264在H.264帧内预测模式选择的新方法-PPT课件

Features
• The basic image block unit
– H.264: 4x4 size – MPEG-1/2/4 and H.261/3: 8x8 size
• Some advance features of H.264
– – – – 4x4 integer DCT Intra-prediction in I-frame coding Quarter-pixel motion compensation Multiple reference frame and multiple block size for P-frame coding
Signaling I-Prediction Mode (3-4)
• The encoder sends a flag for each 4x4 block, prev_intra4x4_pred_mode
Signaling I-Prediction Mode (2-4)
• In below figure, C is the current 4x4 block to be encoded
• For current block C, the encoder and decoder calculate the most probable prediction mode, the minimum of the prediction modes of A and B • If either of these neighboring blocks is not available, the corresponding value A or B is set to 2 (DC prediction mode)
Luminance Macroblock in a QCIF Frame
4x4 Intra Prediction (1-2)
• 4x4 block and its neighboring pixels
• 4x4 luma prediction mode
4x4 Intra Prediction (2-2)
• A prediction mode is a way to generate 16 predictive pixel values (named a to p) using some or all of the neighboring pixels A to Q
– Mode 0: Vertical prediction mode in which pixels a, e, i and m are predicted by A – Mode 1: Horizontal prediction mode in which pixels a, b, c and d are predicted by I – Mode 2: DC prediction in which all pixels (a to p) are predicted by (A+B+C+D+I+J+K+L)/8 – The other modes are similar except that the directions are different
– Example of profiling
• Signaling I-Prediction Mode • Conclusion • References
AVC Encoder Overview
Idea issue!
Introduction
• In the upcoming H.264, intra-prediction for each 4x4 block is used to compress I-frame
– However, the full search algorithm to choose one of the 9 prediction modes is computationally expensive
• A novel approach of mode selection
– Mode selection method based on partial computation of the cost function ( Cost16 = SAD16 + 2Rλ(QP) ), early termination and selective computation of highly probable mode – Using the selective search algorithm of each prediction mode
A Novel Approach of Intra-Prediction Mode Selection for 4x4 in H.264
(First_Edition)
2019.07.07 Summer Vacation Seminar Myoung-Seo Kim
Contents
• • • • • AVC Encoder overview Introduction Features Luminance Macroblock in a QCIF Frame 4x4 Intra prediction
Example of profiling
• Prediction iction Mode (1-4)
• The choice of intra prediction mode for each 4x4 block must be signaled to the decoder and this could potentially require a large number of bits • To encode the prediction mode for each 4x4 block efficiently, the correlation between spatially adjacent blocks is exploited probability list!