In a method of black level and gain control setting, including the steps of applying (42) at least two mutually differing control values (Vd1, Vd2) in a first predetermined ratio, and controlling (35, 3, 7, 15) the black level and gain in response to the at least two mutually differing control values (Vd1, Vd2), at least two mutually differing reference values (Iref1, Iref2) in a second predetermined ratio and corresponding to the at least two mutually differing control values (Vd1, Vd2) are applied (47) to the controlling step (35, 3, 7, 15), where a predetermined relationship exists between the first predetermined ratio and the second predetermined ratio, a first error value depending on a first control value (Vd1) and a first reference value (Iref1) is integrated (43) to obtain a black level setting value, and a second error value depending on a second control value (Vd2) and a second reference value (Iref2) is integrated (44) to obtain a gain setting value.
An improved digital cut-off control loop for black level adjustment in a video processor for controlling RGB output signals. The improved circuit advantageously provides a higher resolution of the black level adjustment, and a short cut-off convergence time when the TV set is switched on. The improved circuit can also blank the RGB output when the cut-off control loop has not converged to the correct level.
An apparatus for automatically stabilizing the black level of a displayed picture when (1) an automatic black level stabilizing function is OFF, (2) black level error occurs between at an ON state and at an OFF state and (3) black level variation and picture disturbance occurs during activation and deactivation of the automatic black level stabilizer. Black level variations when the automatic black level stabilizer are OFF is controlled by processing a cathode current in a negative feedback loop and controlling a CRT grid voltage, storing a divided grid voltage during a converging period and processing the grid voltage in another negative feedback loop in order to adjust the grid voltage to an ON state value.
A digitized luminance signal, representing the luminance component of a picture signal, is adjusted according to data stored in a memory. The data are output according to the value of the digitized luminance signal and multiplied by a weighting signal generated according to the amount of black area represented by the digitized luminance signal. The digitized luminance signal is then multiplied by a value obtained from the weighted product data. Use of the weighting signal enables the luminance scale to be stretched and compressed according to various different control characteristics without the need to store separate data for each characteristic in the memory.
In order to reduce the total capacity of a ROM used for adjustment of the black level and the white level of a digitized luminance signal for a television receiver, for example, a comparator compares the input luminance signal with a predetermined threshold value, a NOT gate inverts the input luminance signal, a first switching unit selects the input luminance signal or the output of the NOT gate, a ROM outputs an adjustment characteristic signal responsive to the output of the first switching unit, a multiplier multiplies the output of the ROM by a weighting signal and outputs the result of the multiplication as an adjustment value, a subtractor subtracts the adjustment value from the input luminance signal, an adder adds the adjustment value to the input luminance signal, and a second switching unit selects the output of the subtractor or the output of the adder.
