Datavideo DVK-300HD, Быстрый старт

Страница: 34 / 43

18 DVK-300HD
In order to fully understand the keying algorithm of the DVK 300 it is necessary to define the no -
tion of the distance |x|. This is used to denote the difference between a parameter of a given colour
and the keyed colour (
Background color ). The following distances are considered as parameters:
◾
The difference due to luminance.
◾
The difference due to chrominance.
4.1
Mode
4.1.1. Chroma key
This function enables the DVK 300 to be used for chromatic keying.
4.1.2. Luma key
This function enables the DVK 300 to be used for luminance-based keying.
4.1.3. Disable key
This function switches the DVK 300 off.
4.2
Chromatic key functions
4.2.1. Chrominance keyer
4.2.1.1.
Background color (Green/Blue)
This function enables the (keyed) background colour to be selected between green and blue.
The reference colour, i.e. the keyed colour (
Background color
), should be defined at point 0 on
the x-axis and then the distance |x|, which will constitute the maximum colour difference between
the keyed colour and its opposite colour, should be defined.
If the keyed colour is green (0,255,0), the distance |x| in the RGB space can be depicted as follows:
The dependence of transparency on the colour distace from keyed colour is presented in the chart
on the next page.
An extended description of the functions
Drawing 34.
Depiction of the distance |x| in the RGB space
G
R
B
|x|