CPP100
SECTION 9
CPP1OPS
25/10/06
www.snellwilcox.com
Version 1 Issue 6
9.5
Recursive Filtering cont.
Bias setting
An alternative mechanism for modifying the level of noise reduction is to use the bias function to introduce a
small offset value to the threshold calculations of the noise floor detector. The THRESHOLD setting can then
be left in AUTO position and the bias control can still be used to increase or decrease the amount of noise
reduction applied to the picture. The behaviour of the bias function is as follows:
-3
Less Noise Reduction
0
Default setting
+3
More noise reduction
Examples for use
Recursive noise reduction is a powerful method of reducing electronically generated or white noise in video or
film sources. Additionally it can be effective in reducing the level of film grain and to some extent film weave.
A typical range of settings may be described by the following table:
Noise Reduction
Setting
Luminance
Level
Chrominance
Level
Bias
Threshold
Setting
Low
Min
Min
0 (Default)
AUTO
Low-Medium
Min
Min
+3
AUTO
Medium
Min
Med
0 (Default)
AUTO
Medium-High
Med
Med
+3
AUTO
High
Med
Max
0 (Default)
AUTO
High-Maximum
Med
Max
+3
AUTO
Maximum
Max
X-Colour
Not relevant
15
Note the bias setting is an offset to the AUTOmatic noise floor measurement and is only effective when the
microprocessor is controlling the closed loop system. Setting the threshold manually effectively opens the loop
therefore the bias adjustment setting no longer has any effect.
RECURSIVE
LUMA
-3 .. 0 .. +3
CHROMA
BIAS
THRESHOLD
