1. A Coding Technique for the Contours in Smoothly Perfect Eight-Connectivity Based on Two-Stage Motion Compensation Sung Ho Cho, Rin Chul Kim, Seung Seok Oh, Sang Uk Lee IEEE TRANSACTIONS ON CIRCUITS AND SYSTEMS FOR VIDEO TECHNOLOGY, FEB 1999

2. INTRODUCTION Object-oriented video coding – 1989 Object-oriented video coding – 1989 –Three parameters of each object : motion, shape and color. A predictive contour coding technique was proposed by C. GU in 1995 A predictive contour coding technique was proposed by C. GU in 1995 –Exploit the temporal correlation i Motion-failure region (MF) Chain coding Motion vector i+1 Motion compensation

3. INTRODUCTION Proposed technique Proposed technique –Based on Gu ’ s technique Contour simplification (smooth) Contour simplification (smooth) –Contour extraction –8-connected chain coding Two-stage motion compensation Two-stage motion compensation

4. R1 R2 CONTOUR SIMPLIFICATION Morphological filter Morphological filter obj Remove spark regions caused by noise or excessively detailed objects xxxxx 1 object -> 2 objects 1 chain code -> 2 chain codes

5. CONTOUR SIMPLIFICATION Majority filter (C. Gu 1995) Majority filter (C. Gu 1995) –B: an area surrounds point x. –(L 1, …, L k ) : k different labels in B. –N i : the number of pixels having L i is N i. –P(x) : the original label in point x. Majority filter x B: 2 L 1 : L 2 : L 3 : L 4 : N 1 :8 N 2 :6 N 3 :6 N 4 :5 P(x): M(P(x)) = L 1

6. CONTOUR SIMPLIFICATION Majority filter (cont.) Majority filter (cont.) –Choose the dominant label around the point M 1 (P(x))M 2 (P(x)) x x x 5 vs 42 vs 74 vs 5 obj

7. CONTOUR SIMPLIFICATION Two ways to show contours Two ways to show contours –Pixel domain Useless for one pixel-wide region Useless for one pixel-wide region –Half-pixel domain R1 R2R3 XX pixel

8. CONTOUR SIMPLIFICATION 8-connected chain coding 8-connected chain coding x M(P(X)) x 4 vs 5 x M(P(X)) x 3 vs 6

9. TWO-STAGE MOTION COMPENSATION Gu ’ s technique Gu ’ s technique –Large overhead Proposed technique Proposed technique –Global motion compensation –Local motion compensation obj i Obj i+1 8 Start codes and chain codes needed Motion-Failure region (MF)

10. TWO-STAGE MOTION COMPENSATION Global motion compensation Global motion compensation 1.Search the global motion vector (GMV). (the motion vector for the object) 2.Global motion compensation (GMC). 3.Extract the contours from the GMC image and current frame, respectively. 4.Compare both contours and divide the current contour into the GMC and global motion failure (GMF) segments. obj

11. TWO-STAGE MOTION COMPENSATION Local motion compensation (for GMF) Local motion compensation (for GMF) 1.Search local motion vector (LMV) form a search area. (find the contour points locally coincident with the contour points belonging to the GMF segment) 2.Divide GMF segment into LMC and LMF segment. 3.GMC and LMC segments are reconstructed by GMV and LMV, respectively. 4.LMF segments use chain coding.

12. TWO-STAGE MOTION COMPENSATION Current frame Previous frame Global motion compensation (GMC) Global motion vector (GMV) GMC segment GMF segment Local motion compensation (LMC) Chain coding Local motion vector, Chain code (LMV)

13. TWO-STAGE MOTION COMPENSATION Error band Error band –Reduce the bit amount for the contours. Start point End point Current contour MC contour

14. TWO-STAGE MOTION COMPENSATION Bit-stream syntax Bit-stream syntax Header Code1 st Segment Code2 nd Segment CodeTermination Code GMV, start point (relative position) MC Segment Code (GMC, LMC Segment) MF Segment Code (LMF Segment) MC Flag, LMV, Segment Length MC Flag, Chain Code

15. SIMULATIONS ImageProposedCAE Claire134.11211.69 Foreman318.07422.64 Weather284.68325.61 Bits/Frame required for encoding the contours Performance of the proposed technique with various error bands Claire Foreman