Grass Valley 8981NR - Manual (Page 14)

14 8981NR Instruction Manual
Configuration
Median Filter
This filtering method acts to replace individual pixels with one of its neigh-
boring pixels in the horizontal direction if it is not with the value range of
the nearest neighboring pixels. This type of filtering is very effective for
single pixel impulse noise where there is no horizontal (line) picture corre-
lation.
The median filter is enabled with an On/Off control. This type of filter has
a larger peak level than the random noise so it occurs before the recursive
filter.
If no impulse noise is present in the signal, it is recommended to leave the
median filter in the Off position, as high frequency horizontal resolution
(sharpness) is reduced with its use.
Other Noise Filter Controls
The following controls are also included with the noise filtering to aid in
making noise adjustments:
Display Bar – when enabled, a sliding horizontal white bar will indicate the
relative value for noise threshold (top) and recursive coefficient (bottom)
on a black background, indicating the full-scale position.
Split Screen – when enabled, allows the output to be split for comparing the
unprocessed video data on the right to the processed video on the left.
Random Noise Generator – when enabled, pseudo-random, wide-band
noise with no average DC value at a peak level of about 8 IRE will be added
to the input. This level is at a practical limit for using recursive filtering and
can be used for experimenting with the noise threshold and recursion coef-
ficient controls. Most actual noise sources will be lower than with this gen-
erator and will require lower settings.
Impulse Noise Generator – when enabled, and the random noise generator
is also enabled, positive, single pixel impulse of about 50 IRE are added to
the noise generator output. This control is useful for testing the median
filter.
Note When the module is powered down, upon restart the Display Bar, Split
Screen, Random Noise Generator, and Impulse Noise Generator will be dis-
abled and must be re-enabled using the local or remote controls.