2.2.2.2 Y/C Separation
Y/C separation may be done using adaptive 5-line (5-H delay) comb filters or a chroma trap filter. The comb filter can
be selectively bypassed in the luma or chroma path. If the comb filter is bypassed in the luma path, then chroma trap
filters are used which are shown in Figure 2−8 through Figure 2−11. TI’s patented adaptive comb filter algorithm
reduces artifacts such as hanging dots at color boundaries. It detects and properly handles false colors in high
frequency luminance images such as a multiburst pattern or circle pattern. Adaptive comb filtering is the
recommended mode of operation.
10
5
10
5
Notch3 Filter
Notch2 Filter
0
0
−5
−5
−10
−15
−20
−25
−30
−35
−40
−10
−15
−20
−25
−30
−35
−40
Notch1 Filter
Notch2 Filter
Notch3 Filter
Notch1 Filter
No Notch Filter
No Notch Filter
0
1
2
3
4
5
6
7
0
1
2
3
4
5
6
7
f − Frequency − MHz
f − Frequency − MHz
Figure 2−8. Chroma Trap Filter Frequency
Response, NTSC Square Pixel Sampling
Figure 2−9. Chroma Trap Filter Frequency
Response, NTSC ITU-R BT.601 Sampling
10
5
10
5
Notch3 Filter
Notch 3 Filter
0
0
−5
−5
−10
−15
−20
−25
−30
−35
−40
−10
−15
−20
−25
−30
−35
−40
Notch1 Filter
Notch2 Filter
Notch 1 Filter
Notch 2 Filter
No Notch Filter
No Notch Filter
0
1
2
3
4
5
6
7
0
1
2
3
4
5
6
7
f − Frequency − MHz
f − Frequency − MHz
Figure 2−10. Chroma Trap Filter Frequency
Response, PAL ITU-R BT.601 Sampling
Figure 2−11. Chroma Trap Filter Frequency
Response, PAL Square Pixel Sampling
2−6
TI [ TEXAS INSTRUMENTS ]
