Motion Predictors and Motion Estimation in H.264 K. C. Yang

Outline Variable Size Block Matching in H.264 Concept of Variable Block Sizes Concept of Variable Block Sizes Motion Vector Predictors in H.264 Motion Vector Predictors in H.264 Fast Integer Motion Estimation for H.264 Video Coding Standard An Unsymmetrical-Cross Multi-Resolution Motion Search Algorithm for MPEG4- AVC/H.264 Coding

Motion Estimation Video clip Current frame Reference frame Motion vector

Variable Block Sizes in H   8 8  168  8 8  4 4  8 4  4

Block Type Decision Minimize the cost function m : Motion vector m : Motion vector p : Predicted motion vector p : Predicted motion vector MOTION : Largrange multiplier MOTION : Largrange multiplier c : current frame c : current frame r : reference frame r : reference frame Predicted MV Real MV cr

MV predictors UPUR LF UP LF UR

MV predictors UPUR LF UPUR LF UPUR LF pMV = median (MV UP, MP UR, MV LF ) pMV UP = MV UP, pMV DOWN = MV LF pMV LEFT = MV LF, pMV RIGHT = MV UR

MV predictors pMV a = median (MV UP, MP UR, MV LF ) pMV b = median (MV UP, MP UR, MV a ) pMV c = median (MV a, MP b, MV LF ) pMV d = median (MV a, MP b, MV c ) a b cd UPUR LF

Fast Integer Motion Estimation for H.264 Video Coding Standard Andy Chang, Peter H. W. Wong, Y.M. Yeung, and Oscar C. Au The Hong Kong University of Science and Technology ICME 2004

Observation Hit ratio (8 x 8 MV = 16 x 16 MV) (MV 8x – MV 16x, MV 8y – MV 16y ) Integer MV Sub-pel MV Foreman QCIF 93%76.6% Stefan QCIF 90%82.6% Block 0Block 1

Algorithm 8 x 8 block Full search Full search 16 x 16 block MV a, MV b, MV c, median(MV UP, MV UR,MV LF ) MV a, MV b, MV c, median(MV UP, MV UR,MV LF ) 16 x 8 block Up : MV a, MV b, MV UP Up : MV a, MV b, MV UP Down : MV c, MV d, MV LF Down : MV c, MV d, MV LF 8 x 16 block Left : MV a, MV c, MV LF Left : MV a, MV c, MV LF Right : MV b, MV d, MV UR Right : MV b, MV d, MV UR LF UPUR ab cd The ME is performed around the eight neighboring locations of the best predicted MV.

Simulation Results On average 69.7% computation saving. Stefan

An Unsymmetrical-Cross Multi-Resolution Motion Search Algorithm for MPEG4-AVC/H.264 Coding Peng Yang, Yu-Wen He, and Shi Qiang Yang Tsinghua University, China ICME 2004

Algorithm Predictor selection Motion estimation Unsymmetrical-cross search Unsymmetrical-cross search Multi-resolution grid search Multi-resolution grid search Extended hexagon-diamond based search Extended hexagon-diamond based search

MV Predictors Selection Higher level Lower level

16 x 16 block (0, 0), default predicted MV (0, 0), default predicted MVOthers (0, 0), default predicted MV, and up layer MV (0, 0), default predicted MV, and up layer MV e.g. e.g. Use the Lagrangian cost function to find the minimum. MV Predictors Selection

Unsymmetrical-Cross Search

Multi-Resolution Grid Search Extended hexagon-diamond based search

Simulation Results Compare with the Fast Full Search in JM6.1 time saving

Simulation Results Rate-distortion