Knox Video VS-200 - Manual (Page 38)

K NOX V IDEO VS-200 O PERATION M ANUAL
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This menu item allows you to swap the foreground and background images when
Lock mode is set to Lock & Mix. It will have no effect in any other mode (since no
background is present).
Normally, your foreground is the input (window) source and your background is the
lock source. This then allows you to superimpose any graphics or video input on top
of the lock source by keying out a certain color or range of colors in the input source.
Swapping them means that the input source moves to the background and the lock
source is now in front of it. Thus you are now keying out the lock source colors to
reveal the input source behind it.
Note that this is different to simply swapping over the input and lock sources as that
would affect the final output resolution – see examples below:
Input
source Lock
source Swap Foreground
(keyed) Background
(non-keyed) Output
resolution
XGA NTSC Off XGA NTSC NTSC
XGA NTSC On NTSC XGA NTSC
NTSC XGA Off NTSC XGA XGA
NTSC XGA On XGA NTSC XGA
(XGA is 1024x768)
You will see that the Swap between foreground and background has no effect on the
output resolution as this is always set by the Lock source.
The Min/Max parameters are used to select what range of Y (luminance/grey-scale)
values are made transparent within the selected window/lock source. In order to key
out part of an image, start with the max value and increase it until the required lighter
parts within the window/lock source disappear. Then adjust the min level to bring
back any darker parts of the image.
The Y Key softness option removes noise from the keyed image, generally at the
edges. Adjust as required to make the edges of the key as sharp or as soft as
desired. The noise is where the analog to digital process (A/D conversion) may not
sample a 50% brightness as being exactly 50% i.e. sometimes 49% and sometimes
51%. Increasing the softness value will broaden the range of keyed colors so that
the keying of images varies depending on how close a color is to the keyed-out
range.
Adjust keyers
Y Key min/max [ 0] [ 32]
Adjust keyers
Y Key softness [ 0]
Adjust keyers
Y Key invert [Off]