Barco R9004120, Руководство пользователя

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12. Advanced Settings
Another value that is subject to alteration is the amplitude of the signal, resulting in an altered “Gain” of the signal ( “white level” or
contrast ).
The alterations of the three color signals will happen independently i.e. the colors will end to be unbalanced, image 12-2
B
Black leve
0.7V
Image 12-1
Black leve
∆
G
∆Β
∆
R
R
G
B
Image 12-2
One can conclude here that a good color tracking can only be met by using three previously (input) balanced
color signals
Analog Digital Conversion
The analog color signals must pass through an Analog/Digital conversion circuit prior to any digital processing in the PMP.
A typical ADC transforms the analog value into an 8 bit coded digital signal.
The graphic shows that when converting a signal containing a DC offset component the range of the converter is not optimally used.
Black level
∆
R
ADC
0
255
i1 : superfleous information
i2 : video information
Image 12-3
One can conclude here that a good data conversion can only be met by using three previously (input) balanced
color signals
The objective of input balancing
The objective in input balancing is to “set” the same black level and the same white level for the three colors of a particular input
source.
Black level setting : brightness
White level setting : contrast
The same absolute black and white level for the three colors allow the same reference for Brightness and contrast control of the
picture !
These two references also set the range in which the ADC will work for that particular source (this explains also why each input
balance setting is linked to a particular source and thus saved in the image file).
70 R5976672 SOLARIS LC40 01042004