SU557516A1 - Device for adjusting video path gamma correction - Google Patents

Description

one

The invention relates to television technology and can be used in video path equipment to improve the quality of television images, especially when transmitting movies.

A device for adjusting gamma correction in a video path is known, comprising a logarithmifier, a first adder, a serially connected attenuator, an antilog device and a second adder, as well as an extinguishing pulse generator, the outputs of which are connected to one of the inputs of each adder l.

However, the known device has a low accuracy of gamma correction adjustment.

The aim of the invention is to improve the accuracy of the adjustment of gamma correction.

For this, the device for regulating the gamma correction of a video path, containing a heater, a first adder, a series-connected attenuator, an anti-logarithm and a second sum, an ator, and also an extinguishing pulse generator, the outputs of which are connected to one of the inputs of each adder, are entered peak detector, comparison circuit and reference signal generator, the first adder is connected to the attenuator input, the input is connected to the logarithm, and the attenuator output is connected via the peak detector to the first comparison input, the second input which is connected to the reference signal generator and the output-control input to

attenuator ,.

The schematic diagram shows the block diagram of the proposed device.

The device for adjusting the gamma correlation and the video path contains a logarithm 1, a first adder 2, a serially connected attenuator 3, an anti-logrifmator 4 and a second adder 5, as well as an extinguishing pulse generator 6, a peak detector 7, a comparison circuit 8 and

generator 9 etalo signals. The outputs of the damping generator are connected to one I9 inputs of each of the adders 2 and 5. To the input of the attenuator is connected the first adder 2, the input connected to the logarithm 1, and the output

Attenuator 3 is connected via the peak detector 7 to the first input of the comparison circuit 8, the second input of which is connected to the generator 9 of reference signals, and the output to the control input of the attenuator 3. The proposed device operates as follows.

The input of the logarithm 1 receives the video signal, which is pre-normalized by the white level. This signal may have a different dynamic range, and the objective of the proposed device is to bring the dynamic range of the output signal to a certain rate, corresponding to the capabilities of the television system. The logarithm 1 performs the conversion

gg-x

Y r - t-i

where is x

-prokormlirovanny entrance., - And A KS

NOI signal;

 at

- normalized output V, j (1 s

NOA signal;

J. L A X s

-AVianasoH logarithm.

 ll and n

The first adder 2 during the return stroke on the line at 6, sends to the video signal imulu7: sylles lsheki from the generator of extinguishing pulses 8. amorct and which was installed} —standable to the otnoi-o level in the preliminary prolor: h: 01rov, annoys , on amult video signal. The level Imschl, ,, peredae JYi during the return stroke on the line, serves to tie the signal by the initial level fixation scheme and in this sense is the beginning, the counting. The transfer of this level, which occurred in adder 2, causes a change in the entire signal magnitude according to the expression:

gg-x

eg.D

Further, the signal passes through the attribute 3, the transmission coefficient of which is set equal to the required gamma correction value of the video path. A signal is generated at the attenuator output.

eg-;

V

eg-D

This signal is nociynaeT on antilog of torus ™ 4, which performs the following conversion:

2,

Z is the normalized output signal of the actilogarithmator, B „is the output range of an - ll and n

tilogarnfmator,

   where j is the contrast ratio

To automatically adjust the gamma correction of the video path, it is necessary to measure the dynamic range of the input signal, which is most conveniently judged by

/ Ggg-d

The signal necessary for controlling the dynamic range can be obtained from the output of the first sum of the matrix 2 or attenuator 3. Due to the complete replacement of the level of zero brightness during the blanking interval to the maximum white level in the proposed device, the following automatic control scheme is formed.

The signal from the output of the attenuator 3 is fed to the peak detector 7, and a slowly varying signal corresponding to the dynamic range of the television image is generated at its output. In comparison circuit 8, the signal from the output of the peak detector 7 is compared with the reference signal coming from the generator 9 of the reference signals ,

The error signal highlighted in the comparison circuit is fed to the control input of the attenuator and its transmission coefficient in such a way that the error signal, as output of the comparison circuit, is minimized. In this case, the dynamic range of the input signal is reduced to the value specified by the generator of reference signals,

In the proposed device, the accuracy of gamma correction adjustment is increased. With this device, the quality of the television image is improved when transferring films that are poorly balanced in contrast to various reportage materials, and the workload of the staff is reduced.

Claims (1)

1. Technical description of the telecast, MK U11 - 69 of the company Rank Sintell (Angshsch).