1 Error Concealment for Shape in MPEG-4 Object-Based Coding Student: Jieh-Yuean Hsu Advisor: Prof. David W. Lin

2 Reference [1]Meng-Yuan Liu, “ Real-Time Implementation of MPEG-4 Video Encoder Using SIMD-Enhanced Intel Process ”, M.S. thesis, Department of Electrical Engineering, Nation Chiao Tung University, Hsinchu, Taiwan, July 2004 [2]Cheng Huang and Paul Salama, ” Error Concealment for Shape in MPEG-4 Object-Based Video Coding ”, IEEE Transactions on Image Processing, Vol. 14, No. 4, April 2005.

3 Reference [3]Guido M. Schuster, Aggelos K. Katsaggelos, ” Motion Compensated Shape Error Concealment ”, IEEE Transactions on Image Processing, Vol. 15, NO. 2, February 2006

4 Outline Introduction of MPEG-4 Object-Based Coding Error Concealment Boundary Extraction Boundary patching Boundary Filling Experimental Result Conclusion

5 Outline Introduction of MPEG-4 Object-Based Coding Error Concealment Boundary Extraction Boundary patching Boundary Filling Experimental Result Conclusion

6 VO and VOP VO: Video Objects VOP: Video Object Planes A sequence of VOPs is referred to as a VO I-VOP: Intra-coded P-VOP: Predictive-coded B-VOP: Bidirectionally predictive-coded

7 VO and VOP

8 VOP information Spatial (Intra) Shape (Object-Based Only) Texture Temporal (Inter) Motion

9 Structure of VO Encoder

10 Shape Information Alpha plane Binary alpha plane Gray scale alpha plane

11 Binary Mask 16 BAB Transparent Opaque Boundary

12 Outline Introduction of MPEG-4 Object-Based Coding Error Concealment Boundary Extraction Boundary patching Boundary Filling Experimental Result Conclusion

13 Basic Assumption The shape of the objects does not drastically change between the current VOP and the reference VOP It is assumed that the reference VOP is undamaged

14 Boundary Extraction Use the 8-neighborhood If any pixel in the 8-neighborhood of a current pixel doesn ’ t belong the object boundary The boundary will be 4-connected

15 Boundary Extraction

16 4-connected Boundary

17 Boundary Patching Find the number of endpoints A boundary pixel having only one 4-connected neighbor The number of endpoints must be even Partition the endpoints in the current VOP

18 Boundary Patching Endpoints A a c C B b

19 Boundary Patching Patching by Global Motion Compensation Some parameter: Scale: Centroid:

20 Boundary Patching orientation angle: Rotation angle:

21 Boundary Patching Current VOP Reference VOP

22 Boundary Patching Reference VOP Current VOP

23 Boundary Patching Mapping A a c C B b A a c C B b Current VOP Reference VOP

24 Boundary Patching Traverse the boundary of the ref. VOP, and record the order of endpoints ex: Map each pixel in curve whose endpoints belong to different pair ex,,

25 Boundary Patching Reference VOPCurrent VOP a A c C B b Recovered pixel

26 Boundary Filling Filling in the closed boundary of the VOP with opaque pixels After filling, we can get the recovered VOP Recovered VOP

27 Outline Introduction of MPEG-4 Object-Based Coding Error Concealment Boundary Extraction Boundary patching Boundary Filling Experimental Result Conclusion

28 Experimental Result brea_qcif, 30 fps

29 Experimental Result

30 Experimental Result Akiyo_cif, 10fps

31 Experimental Result

32 Experimental Result brea_qcif, 10 fps

33 Outline Introduction of MPEG-4 Object-Based Coding Error Concealment Boundary Extraction Boundary patching Boundary Filling Experimental Result Conclusion

34 Conclusion The method for shape concealment based on global motion compensation It works well for video sequence with slow motion and high frame rate It can achieve good result, even the shape is severely damaged Extra information added resulted in 5% increase for stream size, and it is acceptable