JPH0364169A - Contour compensation circuit - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to eight contour compensation ports for video signals, and particularly to a contour compensation circuit capable of extracting a contour signal suitable for the brightness and gradation of a screen.

[Summary of the invention]

The present invention makes it possible to adjust the gain of a signal within a specific level range of an input video signal prior to contour signal extraction,
This is a contour compensation circuit that can obtain contour signals suitable for the brightness and gradation level of each screen.

[Conventional technology]

In television cameras, the contour compensation circuit is often provided after the video signal passes through a gamma correction circuit that imparts gamma characteristics to the video signal. If it is necessary to pass the signal through a contour compensation circuit in a video reproducing device or the like, the video signal to which the γ characteristic has been imparted will naturally be used.

By the way, in conventional contour compensation circuits, the contour signal extracted from the video signal and the original video signal are combined to compensate for the contour of the video. , the contour signal extraction method is sometimes devised. For example, in a TV camera, if you want to emphasize the gradation near the white level without making the noise near the black level noticeable, extract the contour signal after level conversion using the inverted T characteristic, and extract the contour signal from the original image with the γ characteristic. Combination with signals may be performed. Further, a gain characteristic other than the above-mentioned inverted T characteristic may be used. However, since these techniques obtain contour signals with fixed gain characteristics, it is not possible to adapt the contour signals each time to individual screens where the brightness and gradation of the image vary.

[Problem to be solved by the invention]

In the present invention, the problems described in the prior art are solved, and
An object of the present invention is to obtain a contour compensation circuit that can respond to changes in brightness and gradation for each screen of video and obtain a contour signal suitable for that screen.

[Means to solve the problem]

In the present invention, there is provided a branch circuit that branches an input video signal into a first circuit and a second circuit, and a contour signal that extracts a signal of the contour portion from the video signal branched to the first circuit. It has an extraction circuit, a main gain adjustment circuit that amplifies and adjusts the gain of the extracted contour signal, and a synthesis circuit that synthesizes the output of the main gain adjustment circuit and the video signal branched to the second circuit. In the contour compensation circuit, a sub gain adjustment circuit is provided between the branch circuit and the contour signal extraction circuit, which can adjust the gain of a signal within a specific level range of the video signal branched to the first circuit. This is a characteristic contour compensation circuit.

[Effect]

In the present invention, the gain of a specific level range of the input video signal can be adjusted prior to contour signal extraction. For example, different gain settings are made for near the black level, intermediate level, and near the white level, and the gain settings can be changed for each screen. For example, the gain at an intermediate level can be changed at any time by comparing it with a library pre-stored in a semiconductor memory.

Therefore, a contour signal suitable for the brightness and gradation level of each screen can be obtained, and contour compensation can be performed according to the brightness and gradation level of each screen.

〔Example〕

The present invention will be described in detail with reference to FIG.

It has a branch circuit l that branches an input video signal into a first circuit and a second circuit, and the video signal branched to the first circuit is adjusted to a specific level of the video signal by a sub-gain adjustment circuit 2, which will be described in detail later. The contour signal extraction circuit 3 extracts the signal of the contour part of the video signal, the main gain adjustment circuit 4 adjusts the level of the entire contour signal, and the synthesis circuit 5 branches the signal to the second circuit. The contour is corrected by combining it with the video signal.

In the tank bottom described above, the branch circuit 1 may be configured using, for example, an emitter follower circuit of a transistor or a source follower circuit of a field effect transistor as a buffer amplifier, or the branch circuit 1 may be simply divided in wiring. The contour signal extraction circuit 3 can be provided with separate vertical contour signal circuits and horizontal contour signal circuits, for example. For example, a technique for obtaining a contour signal by calculating a video signal delayed using a delay circuit and a video signal before the delay is well known.

Although not particularly shown in the synthesis circuit 5, if necessary, the second circuit is connected to the second circuit so that the main stream of the video signal transmitted from the second circuit and the contour signal transmitted from the main gain adjustment circuit 4 can be level-aligned and time-aligned. It goes without saying that processing such as amplification and delay of the video signals of the circuits is performed before synthesis.

Note that the input video signal is usually a video signal given a γ characteristic. Also, R (red), G (green), B
It may be a combination of video signals of three colors (blue) in a predetermined ratio or an arbitrary ratio, and for example, it may be a signal in which only one color of G (green) is selected.

Next, the sub gain adjustment circuit 2 will be explained according to FIG. In the example shown in Figure 2, the video signal from the first circuit is divided into three categories depending on the input level, and A<input level difference<B
The gain can be adjusted in the range of . For example, even if the output level difference H-E in the interval A<X<B is changed to F-H, the output level difference I-H in the interval B<X<C is equal to C, -F. It's Nishide.

In other words, in the sections of the graph in Figure 2 where the slopes (i.e., gains) are equal, the output level differences for the same input level differences are equal, so it is possible to create sections with different gains for each input level and adjust the gain only for that specific section. By doing so, the input/output characteristics shown in FIG. 2 can be achieved.

In Figure 2, there are three categories depending on the input level.
There is no need to be particular about this, and for example, it is possible to set a section in which a substantially inverse γ characteristic can be obtained, and make it possible to adjust the gain of one or more of the sections. Although not shown, the optimal gain on the brightness gradation side of the image is stored in a semiconductor memory, and the stored information is obtained by detecting, for example, the peak value, average value, median, dynamic range, etc. of the video signal level. It is also possible to set the gain for each input level classification by checking with the input level. Of course, it goes without saying that the sub gain may be adjusted while observing on a video monitor.

In addition, the video signal circuit may be, for example, R (red), G (green), B (
In the case where the contour compensation circuit of the present invention is provided separately for each color component such as blue), the contour compensation circuit of the present invention can be provided for each color component, but it is also possible to distribute the output of the main adjustment circuit 4 to each video signal circuit. In this way, only the combining circuit may be provided in each video signal circuit.

〔Effect of the invention〕

By implementing the present invention, it is possible to obtain a contour compensation circuit that extracts a contour signal after adjusting the gain of a signal in a specific level range of an input video signal.

As a result, it is possible to obtain video equipment such as a television camera that can perform contour compensation suitable for each screen in response to changes in brightness and gradation for each video screen.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a block diagram of an embodiment of the present invention.
This is an example of input/output characteristics of the sub gain adjustment circuit shown in the figure. 1-----------------One branch circuit 2--・-・
・−・・−・−・Sub gain adjustment circuit 3・・・・・−1−−
−−−−−−Contour extraction circuit 4・・−−−−−−−・−・
- Main gain adjustment circuit 5 - Synthesis circuit Block diagram of an embodiment of the present invention Fig. 1 Hatake 1 of Fig. 1 Input/output characteristics of the gain adjustment circuit I voltage Fig. 2 471-

Claims (1)

[Scope of Claims] A contour comprising a branching circuit that branches an input video signal into a first circuit and a second circuit, and extracting a signal of the contour portion from the video signal branched to the first circuit. a signal extraction circuit, a main gain adjustment circuit that amplifies the extracted contour signal and adjusts the gain, and a synthesis circuit that combines the output of the main gain adjustment circuit and the video signal branched to the second circuit. In the contour compensation circuit, the first circuit is connected between the branch circuit and the contour signal extraction circuit.
1. A contour compensation circuit comprising a sub-gain adjustment circuit capable of adjusting the gain of a signal within a specific level range of a video signal branched into the circuit.