深入分析梳状滤波器原理Comb-filter课件.pptVIP

Comb Filter  Outline Y-C separation 2D comb filter 3D comb filter 2D adaptive comb filter conclusion Comb filter (Y-C separator) Separate the incoming composite video signal into luminance (Y) and chrominance (C). NTSC composite signal Video signal prepared for broadcast contains two major parts, the luminance (Y) and chrominance (C). Basic concept for Y C separate 1.Frequency- notch , bandpass filter ( in early years ). 2.Chrominance phase difference- comb filter ( today ). Frequency Notch/bandpass filter system significant overlap , energy go through. Chrominance phase difference chroma burst reference and the chroma information is reversed by 180 degrees on alternate lines (luminance of the system to remain constant[ monochrome receivers]). 2D comb filter Important concept…picture information (y , c) is about the same from line to line . Special case( y - c , y + c ). Why we call it a comb filter 2D weighting comb filter different colors vertically through the picture . (1/4,1/2,1/4). the transition from one color to another is softened. Horizontal delay analog: glass delay line , CCD . digital : memory . 3D comb filter compare information in successive frames .(odd) perfect separation of Y and C for still frame images ( key advantage over the 2D filter ). motion or serious color changes , 3D filter may perform no better than the 2D filter. has to store two frames of video data. Problems Vertical detail difference (adjacent lines). Motion difference (adjacent frames). Adaptive comb filter 1.Detect and select one form. 2.Correction terms. 3.Weighting and sum . An improved 2D adaptive comb filter Overview (mode A,B,C,D) Mode A (does not perform comb filtering) Only when video image has serious vertical difference. Just a bandpass filter. Mode B (2D weighting with bandpass filter) Normal mode ,Y-C can be separated quite well. Mode C (2D weighting without bandpass filter) Use under that 3 lines are so close. Can separate better than B. Mode