MPEG-4 Part 2, VisuaPPrediction module:GOPVideosequenceGOPGOPGOP
Prediction module: GOP MPEG-4 Part 2, Visual Video sequence GOP GOP GOP
MPEG-4 Part 2.VisualPTextureencoding:predictionmodule5-12-(5+1)/22-5P国2-1PBy differences,reduce the dynamic ofthe information to encode
Texture encoding : prediction module MPEG-4 Part 2, Visual By differences, reduce the dynamic of the information to encode 1 . 5-1 2-(5+1)/2 2-5 2-1
MPEG-4Part 2.VisualPPrediction modulewithMotion CompensationVxVyAfterpredictionandmotionInitial imageAfterpredictioncompensationMotion compensation strongly reduces the information dynamics
Prediction module with Motion Compensation MPEG-4 Part 2, Visual Motion compensation strongly reduces the information dynamics Initial image After prediction + Vx Vy After prediction and motion compensation
MPEG-4 Part 2, VisualPMotionvectors(MVs)Mode1MV:onemotionvectorforone MBMode4MV:onemotionvectorforeachblockinMBTheMVs areestimated onlyforthe luma(Y)componentDifferential coding of MVs with respect to theneighbourhood口Quarter-pelaccuracyNew Global MVs estimation for the entire image Direct mode forthe bidirectional compensationMotion estimation methods are not subjectto standardization!
Motion vectors (MVs) MPEG-4 Part 2, Visual Motion estimation methods are not subject to standardization! Mode 1MV: one motion vector for one MB Mode 4MV: one motion vector for each block in MB The MVs are estimated only for the luma (Y) component Quarter-pel accuracy Global MVs estimation for the entire image Direct mode for the bidirectional compensation Differential coding of MVs with respect to the neighbourhood New
MPEG-4 Part 2, VisualPQuarter-pelmotionestimationNeInteger(pel)motionestimation:the MVs areinteger-problemforthe sub-pixelmotion between two frames-importantpredictionerrorSolution:half and quarterpel motion estimationBilinearinterpolationInterpolation-8pelneighbourhood-a=(-8A+24A-48Az+160A,+160B,-48B,+24Bs-8B.)m0d256b=(A+B+1)mod(2)d=(A+B+C+D+2)mod(4)b'=(a+b+1)mod(2)d'=(a+b+c+d+2)mod(4)HalfQuarterIncrease MVsresolution,but reduce the prediction error
Quarter-pel motion estimation MPEG-4 Part 2, Visual Increase MVs resolution, but reduce the prediction error Integer (pel) motion estimation: the MVs are intege r - problem for the sub-pixel motion between two frames - important prediction error Solution: half and quarter pel motion estimation Bilinear interpolation Half A B C b c d D b=(A+B+1)mod(2) d=(A+B+C+D+2)mod(4) Interpolation - 8 pel neighbourhood Quarter A4 A 3 A2 A1 B1 B 2 B 3 B 4 a a=(-8A4+24A3-48A 2+160A1+160B1-48B 2+24B3-8B 4) mod 256 b c a d b’ c’ d’ b’=(a+b+1)mod(2) d’=(a+b+c+d+2)mod(4) New