名师推荐深入分析梳状滤波器原理Comb-filter
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Check Y signal only. Switch mode when difference exceeds a
threshold value.
Detection algorithm
Normal way (upper). Special detection (bottom). Use these two detections. (T1,T2,T3)
constant[ monochrome receivers]).
180 degrees
2D comb filter
Important concept…picture information (y , c) is about the same from line to line .
Special case( y - c , y + c ).
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).
Y
Y
C
Y’ C’
Mode A (detection (1,3) > T3)
Which means the vertical detail defference is serious.
Bandpass filter performs better than comb filter.
Y
Mode B (detection (1,3) < T3)&(detection (2,3) > T2)
Reference
பைடு நூலகம்
Which means 3 lines have almost the same Y-C information.
Mode C better than B.
Mode D
Y
(T1<detection (1,3) < T3)&(detection (2,3) < T2)
Which means that detection(2,3)
(composite)
NTSC composite signal
Video signal prepared for broadcast contains two major parts, the luminance (Y) and chrominance (C).
Basic concept for Y C separate
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
dominates.
Mode D
Conclusion
2D,3D,adaptive 2D.
Academic : adaptive 2D comb filter (less gate count ,more strategy).
Earn money : 3D/2D switch (best performance ,largest area)
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)
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
Use under that 3 lines are so close. Can separate better than B.
Mode D (2D simple comb filter)
Use under that detection(2,3) dominates.
Common method for difference detection
y y+c
y-c
2c
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.
( 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.
1.Frequency- notch , bandpass filter ( in early years ).
2.Chrominance phase differencecomb filter ( today ).
Frequency
Luminance & chrominance frequency
The mostly encountered situation. Use bandpass filter to eliminate
little difference between Y.
Y
Mode C (detection (1,3) < T1)&(detection (2,3) < T2)
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.
threshold value.
Detection algorithm
Normal way (upper). Special detection (bottom). Use these two detections. (T1,T2,T3)
constant[ monochrome receivers]).
180 degrees
2D comb filter
Important concept…picture information (y , c) is about the same from line to line .
Special case( y - c , y + c ).
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).
Y
Y
C
Y’ C’
Mode A (detection (1,3) > T3)
Which means the vertical detail defference is serious.
Bandpass filter performs better than comb filter.
Y
Mode B (detection (1,3) < T3)&(detection (2,3) > T2)
Reference
பைடு நூலகம்
Which means 3 lines have almost the same Y-C information.
Mode C better than B.
Mode D
Y
(T1<detection (1,3) < T3)&(detection (2,3) < T2)
Which means that detection(2,3)
(composite)
NTSC composite signal
Video signal prepared for broadcast contains two major parts, the luminance (Y) and chrominance (C).
Basic concept for Y C separate
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
dominates.
Mode D
Conclusion
2D,3D,adaptive 2D.
Academic : adaptive 2D comb filter (less gate count ,more strategy).
Earn money : 3D/2D switch (best performance ,largest area)
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)
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
Use under that 3 lines are so close. Can separate better than B.
Mode D (2D simple comb filter)
Use under that detection(2,3) dominates.
Common method for difference detection
y y+c
y-c
2c
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.
( 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.
1.Frequency- notch , bandpass filter ( in early years ).
2.Chrominance phase differencecomb filter ( today ).
Frequency
Luminance & chrominance frequency
The mostly encountered situation. Use bandpass filter to eliminate
little difference between Y.
Y
Mode C (detection (1,3) < T1)&(detection (2,3) < T2)
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.