Thanks Derek,
Analog clamping circuit is always on. Also clamp capacitor is near (about 1 cm) the ADV7188.
Tomorrow i'll test manual luma gaining as you mentioned. But my main question is: is my video signal cut at the 1.6V ?(ADC max range) and am i, because of this, missing some picture resolution data?
is digital gain setting enough? Should i worry about the incorrect clamp level?
Also is this a good idea to disable internal clamp circuitry and manually (externally) give a dc level by two resistors (voltage divider) about 0.9V ?