2020918 JCTVCA 022 Multiple Predictor Sets for Intra

2020/9/18 JCTVC-A 022 Multiple Predictor Sets for Intra Coding Lingzhi Liu Huawei Technologies Co. , LTD. HUAWEI TECHNOLOGIES CO. , LTD. www. huawei. com

Agenda l Introduction l Multiple predictor sets for intra coding l Encoding and decoding processes l Experimental results l Complexity analysis l Conclusion l Future work HUAWEI TECHNOLOGIES CO. , LTD. Page 2

Introduction l l Predictor Set in H. 264/AVC p Directional Subset: 8 directional predictors p Non-directional Subset: 1 DC predictor Works well for general sequences but not enough for complex textures. l. Directional Subset: 8 Directional Prediction Mode l. Non-directional Subset: 1 no-directionnel Mode (DC Mode) HUAWEI TECHNOLOGIES CO. , LTD. Page 3

Multiple predictor sets for intra coding --Ideas l Introduce more predictors to improve the accuracy of predictors. l Keep current framework. p l Keep the prediction method for intra prediction mode. Easy extension to bigger block size HUAWEI TECHNOLOGIES CO. , LTD. Page 4

Multiple predictor sets for intra coding --New predictor set l 1 directional subset: 8 predictors l 1 non-directional subset: 1 predictor l Template matching as the non-directional predictor l HUAWEI TECHNOLOGIES CO. , LTD. Directional subset: Uniformly rotating the directional subset in H. 264/AVC of 12. 5 degree counterclockwise Page 5

Encoding and decoding processes l Current two predictor sets are supported p One flag on macroblock level to indicate the selected predictor set p The same method is used to predict intra prediction mode from neighbor blocks in spite of which predictor set it belongs to. n Reason: the predictors with same intra prediction mode number in different predictor set have similar texture features l Syntax change: if( transform_8 x 8_mode_flag && mb_type = = I_Nx. N ) { transform_size_8 x 8_flag predictor_set_flag } HUAWEI TECHNOLOGIES CO. , LTD. Page 6

Experimental results --testing condition l Jm 11. 0 kta 26 r 1 l Constraint set 1 and 2 (All I-frame, CABAC ), Constraint set 2( All Iframe, CAVLC ) p MPSI is applied to Intra 4 x 4 and Intra 8 x 8 prediction for all constrain sets p RDO enabled p RDOQ enabled p Full length CFP test sequences (WQVGA, WVGA, 720 P and 1080 P) p Use QPs defined in Alpha anchor. HUAWEI TECHNOLOGIES CO. , LTD. Page 7

Experimental results --Constraint set 1 and 2 (All I-frame, CABAC ) HUAWEI TECHNOLOGIES CO. , LTD. Page 8

Experimental results --Constraint set 2( All I-frame, CAVLC ) HUAWEI TECHNOLOGIES CO. , LTD. Page 9

Experimental results -- MPSI + ALF HUAWEI TECHNOLOGIES CO. , LTD. Page 10

Complexity analysis --Encoding time HUAWEI TECHNOLOGIES CO. , LTD. Page 11

Complexity analysis --Decoding time HUAWEI TECHNOLOGIES CO. , LTD. Page 12

Percentage of predictor sets HUAWEI TECHNOLOGIES CO. , LTD. Page 13

Conclusion l A new predictor set with similar subsets as in H. 264/AVC is introduced to get better prediction of local images with complex textures. l The same method in H. 264/AVC can be used to predict the intra prediction mode. l MPSI achieves 3. 14 % bit reduction at Constraint set 1 and 2 (CABAC), and 3. 89% bit reduction at Constraint set 2 (CAVLC) on average. l Moreover, MPSI is compatible with other KTA tools, and is able to achieve more coding gain when used together. HUAWEI TECHNOLOGIES CO. , LTD. Page 14

Future work l Extend MPSI to block size larger than 8 x 8 (16 x 16, 32 x 32, etc) l Introduce more predictor sets to improve the accuracy of intra prediction for larger block sizes. HUAWEI TECHNOLOGIES CO. , LTD. Page 15

l HUAWEI TECHNOLOGIES CO. , LTD. lzliu@huawei. com Page 16