Chroma Signal Knee Clipping Process - Sony SS-HQ1 Application Notes

10.4.8. Chroma Signal Knee Clipping Process

In cases where the chroma variable gamma circuit input level exceeds 200%, the knee output can be clipped
to a constant level.
160 [%]
140 [%]
120 [%]
100 [%]
80 [%]
100 [%]
Table 10.4-4 CKNCLIP (or UCKNCLIP) Function Explanation
Parameter
CKNCLIP
CAT2_Byte30_bit3,4
UCKNCLIP
CAT13_Byte53_bit3,4
The output level depends on the CKNEE (UCKNEE) setting.
Examples:
CKNCLIP=1[h] & (CKNEE=3[h] & CKNEE2=1[h]) -> Output is clipped to 100% chroma knee output at 300%
CKNCLIP=1[h] & CKNEE=4[h] -> Output is clipped to 160% chroma knee output at 300% input and higher.
CKNCLIP=3[h] & CKNEE=4[h] -> Output is clipped to 120% chroma knee output at 200% input and higher.
<Note>
These output characteristics are based on the use of a chroma variable gamma circuit. If overflowing occurs
(e.g., if R-Y and B-Y color difference conversion processes or YC-Mix processes are used in a later step),
clipping or suppression (drop in output level with high input) may occur in the output chroma signal at low
levels.
CKNEE=4
CKNEE=3 & CKNEE2=1
200 [%]
INPUT Level ( more over 100 [%] )
Fig 10.4-8 Chroma Signal Knee Clipping Process
Setting
value
0[h] No chroma knee output clipping
1[h] Clips chroma knee output at 300% input and higher
2[h] Clips chroma knee output at 250% input and higher
3[h] Clips chroma knee output at 200% input and higher
CKNCLIP=2
CKNCLIP=3
300 [%]
Description
input and higher.
107
- SS-HQ1 Application Notes -
Ver.1.0.0 January 7, 2005
CKNCLIP=1
CKNCLIP=1
400 [%]
Remarks
Depends on
output level
=CKNEE
(UCKNEE).
Also linked to
CKNEE2=1[h]
(UCKNEE2=1[h]).