PREDICTIVE SHAPE CODING USING GENERIC POLYGON APPROXIMATION Jong-il Kim and Brain L. Evans Circuits and Systems, ISCAS '98. Proceedings of the 1998 IEEE International Symposium on, Volume: 5, 1998

Outline Lossy Shape Coding Using Generalized Chain Coding Generalized Predictive Shape Coding Simulation

Lossy Shape Coding Using Generalized Chain Coding

Lossy Shape Coding Using Generalized Chain Coding (con’t) Polygon approximation

Lossy Shape Coding Using Generalized Chain Coding (con’t) Vertex coding –Ri = Vi – Vi-1 –x_max_magnitude, y_max_magnitude –x_dynamic_range_indicator y_dynamic_range_indicator Example ： V = (80,60),(105,66),(85,70),(70,63) R = (25,6),(-20,4),(-15,-7) x_max_magnitude = 25, x_dynamic_range_indicator = 4 y_max_magnitude = 7, y_dynamic_range_indicator = 2

Lossy Shape Coding Using Generalized Chain Coding (con’t) octant number containing the sign bit of x and y A flag indicating which component is the major component –Example ： Ri(y) < Ri(x),Ri’s major component is the x-component

Lossy Shape Coding Using Generalized Chain Coding (con’t) If Ri(y) < Ri(x),Ri’s major component is the x-component –major_component needs (x_dynamic_range_indicator+1) bits –Minor_component needs min( y_dynamic_range_indicator+1,  lg|Ri(x)|+1  )

Lossy Shape Coding Using Generalized Chain Coding (con’t) Example ： –Dynamic range –31~+31, Ri = (6,-3) –Header : x_dynamic_range_indicator = 4=>3 bits y_dynamic_range_indicator = 4=>3 bits –Ri in bitstream ： Octant = 7=>3bits major_component (|x|>|y|,|x|=6) 4+1=>5 bits minor_component : min(4+1,  lg(6+1)  )=>3 bits

Generalized Predictive Shape Coding

Contour Motion Estimation Ic, Ir ： current and reference contour set Nc, Nr ： current and reference contour length A contour pel matching algorithm finds the offset vector (mv x, mv y ) to maximize the number of element in Ic ∩ Ir (mv x,mv y ) Comparison operation ： 2*Nc*Nr times

Contour Motion Estimation Global motion estimation ： all of the contour in a VOP Local motion estimation ： single contour in a VOP Lossless or Lossy motion estimation ： –A contour pel in current contour is within d max range from a reference contour pel

(a)(b) d max =1 (c)(d) d max =2

Coding of matched and mismatched contour position – Reference Index Based Coding Matched contour position –2D -> 1D –Reference contour length is Lr ， just need  lg Lr  –Initial index is 1(the first pel during raster scan) ， counter clockwise direction have increasing indices –For example (last page) Lr = 100 (V2,V3,V4,V1) = (30,38,45,58) Mismatched contour position –Generalized chain coding (octant,major,minor)

Simulation Ec ： average bit for a contour pel

Simulation (con’t)

Conclusion Propose a new predictive binary shape coding method