JPS6268370A - Pseudo synchronizing signal generating circuit - Google Patents

Abstract

PURPOSE:To improve the picture quality by generating a pseudo synchronizing signal in a video signal in place of the synchronizing signal of a reproduced video signal and clamping a level below the pedestal level of a luminance signal other than the synchronizing signal period to eliminate high-frequency whiskers at the tip of the synchronization. CONSTITUTION:A DC component is recovered for a reproduced video signal by a clamp circuit 2. The clamped video signal is inputted to a clip circuit 3 and a synchronizing detection circuit 5, the clip circuit 3 compares the video signal with a pedestal level from a reference voltage source 4 to clip the video signal below the pedestal level. The circuit 5 compares the synchronizing detection level from a reference voltage source 6 with the video signal to detect the synchronizing signal to the video signal and outputs a control signal to a pseudo synchronizing signal adder circuit 7 only during the synchronizing signal period. The circuit 7 adds the pseudo synchronizing signal with a pseudo synchronizing signal level having a constant amplitude to the output of the clip circuit 3 during the synchronizing period detected by the circuit 5. Thus, the high-frequency whiskers generated at the tip of the synchronization and the unarranged amplitude of the synchronizing signal are eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION 3. Detailed explanation of the invention Field of industrial application The present invention is applicable to, for example, a video disc player 17,
This invention relates to a pseudo synchronization signal generation circuit used in a circuit that reproduces a video recorded on a recording medium and processes it into a signal suitable for a television receiver.

2. Description of the Related Art Conventionally, a video signal has been processed using a synchronization signal of a reproduced video BI signal without inserting a pseudo synchronization signal into the reproduced video signal. FIG. 3 shows a waveform obtained by clamping a video signal reproduced by a conventional video signal processing circuit, and the video signal has whiskers due to dirt in the ground, missing bits, and characteristics of the RF circuit. When trying to improve the image quality by processing the reproduced video signal, there was a problem that the image quality could not be improved sufficiently due to this hair, and a problem that the hair that appeared at the tip of the synchronization signal caused a malfunction due to unreliable VQ error. .

Problems to be Solved by the Invention As described above, in the past, hair loss occurred at the synchronization end of the video signal reproduced from the recording medium, and the synchronization level changed, which adversely affected the television receiver and playback. In addition, abnormal conditions such as dust that occur when playing back video signals from a recording medium may cause whiskers smaller than the pedestal level to appear in the brightness signal of the video i signal outside the synchronized period, which may cause malfunction of the playback device. There are also problems that may impede the image quality.

The present invention solves the above-mentioned conventional problems, and uses a simple Q1 configuration to generate a pseudo synchronization signal in the video signal instead of the reproduction synchronization signal. can also be removed, and
The object of the present invention is to provide a pseudo synchronous signal generation circuit suitable for IC implementation.

Means for Solving the Problems In order to solve the above problems, the pseudo synchronization signal generation circuit of the present invention includes one stage of clamp circuit for clamping video No. 11, and a pedestal level control of the video signal clamped by this clamp circuit means. clipping circuit means for clipping the following signals to the pedestal level; synchronization detection means for detecting a synchronization signal section of the video FJ month clamped by the clamp circuit means; and a synchronization signal section detected by the synchronization detection means. The present invention further includes a pseudo synchronization signal adding circuit means for adding a pseudo synchronization signal to the video signal clipped by the clipping circuit means.

Effects According to the above configuration, a pseudo synchronization signal is generated in the video signal instead of the synchronization signal of the reproduced video signal, and the synchronization is performed by clamping the luminance signal below the best level outside the synchronization signal section. The synchronization level can be kept constant by removing whiskers at the tip of the signal, and it is also possible to remove whiskers that occur below the pedestal level of the reproduced signal, so it is possible to improve the image quality.

EXAMPLE Hereinafter, an example of the present invention will be explained with reference to IJ with reference to FIGS. 1 and 2.

FIG. 1 is a circuit block diagram of a pseudo synchronous signal generation circuit according to an embodiment of the present invention, in which 1 is a power terminal, 2 is a clamp circuit, 3 is a clip circuit, and 4 is a reference voltage for pedestal level. 5 is a synchronization detection circuit, 6 is a reference voltage source for the synchronization detection level, 7 is a pseudo synchronization No. 18 addition circuit, 8 is a reference voltage source for the pseudo synchronization signal level, and 9 is an output terminal.

Next, the operation will be explained with reference to FIG. Second
The waveform shown in Figure (a) shows a video signal reproduced from a recording medium. Since the DC component of this reproduced video signal has not been restored, the DC component is restored through the clamp circuit 2. FIG. 2(b) shows a video signal with the DC component restored.

This clamped video signal is input to a clip circuit 3 and a synchronization detection circuit 5. The clipping circuit 3 is a circuit that compares the video signal with a pedestal level from the reference voltage source 4 and clips a signal that is lower than the pedestal level of the video signal. FIG. 2(C) shows the clipped video signal. On the other hand, the synchronization detection circuit 5 compares the synchronization detection level from the reference voltage source 6 with the video signal, detects the synchronization signal of the video signal, and sends a control signal to the pseudo synchronization signal side frame circuit 7 only during the synchronization signal period. Output. Figure 2(b) shows the image (
The relationship between the H number and the synchronization detection level is shown in FIG. 2(d) for the output of the synchronization detection circuit 5. The pseudo synchronization signal side frame circuit 7 side controls a pseudo synchronization signal at a pseudo synchronization signal level with a constant amplitude in the synchronization period detected by the synchronization detection circuit 5 to the output of the clipping circuit 3 that clips the video signal at the pedestal level. do. FIG. 2(e) shows a video signal with pseudo synchronization No. 45 added. In this way, instead of the synchronizing signal of the reproduced video signal, a video signal in which a pseudo-periodic signal of constant amplitude is controlled in the same period is output.

In this way, the reproduced video @ signal is used to clip the signal level below the pedestal level of the video signal, and a pseudo synchronization signal of constant amplitude is added to the synchronization signal section and output. As a result, the whiskers that occur at the tip of the synchronization and the same l! This eliminates unevenness in the amplitude of the ll signal and removes whiskers below the pedestal level, improving image quality.
This pseudo synchronous signal generating circuit has the advantage of being able to reduce the number of L and can be realized with a simple circuit configuration.

Effects of the Invention As described above, according to the present invention, with a simple circuit configuration, it is possible to eliminate whiskers that occur at the synchronization end of the reproduced video 185] and unevenness in the amplitude of the synchronization signal.
Since it is also possible to remove whiskers that occur below the Bedesque level of the reproduced video signal, it is possible to improve the image quality.

[Brief explanation of drawings]

Fig. 1 is a circuit block diagram of a pseudo-Kaimei No. 3 generation circuit in 53 according to an embodiment of the present invention, Fig. 2 is a signal waveform diagram of each part of the circuit shown in Fig. 1, and Fig. 3 is a conventional video transmission signal. J to the processing circuit
31 is a waveform diagram of a state in which the reproduced video image enlightenment is clamped; FIG.

Claims (1)

[Claims] 1. Synchronization of a clamp circuit means for clamping a video signal, a clip circuit means for clipping a signal below the pedestal level of the video signal clamped by the clamp circuit means to the pedestal level, and a video signal clamped by the clamp circuit means. Pseudo synchronization comprising period detection means for detecting a signal section, and pseudo synchronization signal addition circuit means for adding a pseudo synchronization signal to the video signal clipped by the clipping circuit means in the synchronization signal section detected by the synchronization detection means. Signal generation circuit.