7. Image Menu
Black level

∆

G

∆Β

∆

R
R
GB
Image7-25
Onecan conclude here that a good color tracking can only be met by using three previously (input) balanced
color signals
Analog Digital Conversion
Theanalog color signals must pass through an Analog/Digital conversion circuit priorto any digital processing in the PMP.
Atypical ADC transforms the an alogvalue into an 8 bit co ded digitals ignal.
Thegraphic 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 : superfluous information
i2 : video information
Image7-26
Onecan 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
Thesame absolute black and white level for the three colors allows the same reference for Brightness and contrast control ofth e
picture !
These two references also set the range in which the ADC will work for that particular source ( this explains also why each input
balances ettingis linked to a particular source and thus saved in the image file).
How can it be done ?
Tobalance the three color signals of a particular source there are conditions; in fact we must know the black and the white level of
the source i.e. :
1. thesource in question must be able to generate a white signal, ideally a 100% white (background) full screen pattern
2. thesource in question must be able to generate a black signal, ideally a 100 % black (background) full screen pattern
68 R5976491 IQ PRO G500 01/02/2007