JPH04132481A - Video signal processing unit - Google Patents

Abstract

PURPOSE:To obtain a video signal without noise by replacing a video signal of a noise component into an equivalent part of a signal at one preceding horizontal synchronizing signal period. CONSTITUTION:An RF signal recorded by magnetic heads 1, 2 is reproduced and the signal is selected by a changeover circuit for each field. The changeover circuit 3 is controlled by a control signal generator 8 and its signal is demodulated into a video signal by a frequency demodulation circuit 4, a high frequency component is eliminated by a low pass filter 5 and the resulting video signal is outputted through a delay circuit 6 delaying the video signal by one horizontal synchronizing period and a changeover circuit 7. Then the changeover circuit 7 is controlled by a control signal generator 9 and the signal from the control signal generator 9 is synchronized with the signal from the control signal generator 8. In this case, the noise in the video signal caused by discontinuous phase of the RF signal caused at the changeover of an output of a magnetic head is replaced into an equivalent video signal at one preceding horizontal synchronizing signal period so as to be eliminated. Thus, an excellent pattern without noise is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to video signal processing in a magnetic recording and reproducing apparatus for recording and reproducing video signals.

Conventional technology The video signal is frequency modulated, and the first
．． FIG. 3 shows a conventional block diagram of a video signal reproducing system in a magnetic recording and reproducing apparatus that performs recording and reproducing using a second magnetic head. 1.2 is a magnetic head, 3 is a switching circuit,
4 is a frequency demodulation circuit, 5 is a low-pass filter, and 8 is a switching signal generator. The operation of the above-mentioned video magnetic recording and reproducing apparatus will be explained. A video frequency modulated wave signal (hereinafter referred to as RF multiplied signal) recorded on a magnetic recording medium is reproduced by magnetic heads 1 and 2, and the output thereof is outputted to a switching frequency demodulation circuit 4 by a switching circuit 3 for each field. . The switching circuit 3 is switched for each field by a switching signal supplied from a switching signal generating bag W8. The frequency demodulation circuit 4 demodulates the supplied RF multiplied signal video signal and outputs it to the low-pass filter 5. The low-pass filter 5 removes the double frequency component of the carrier wave.

Problems to be Solved by the Invention In such a conventional reproduction system, discontinuity in the phase of the RF multiplied signal occurs when the switching circuit 3 switches, and noise appears at the bottom of the monitor screen, and fluctuations due to jitter components occur. Therefore, it is very noticeable.

Means for Solving the Problems In order to achieve the above-mentioned object, the present invention provides a magnetic recording and reproducing apparatus that frequency-modulates a video signal and records and reproduces it using two different first and second magnetic heads for each field. , the above-mentioned No. 1. a second magnetic head; a first switching circuit that switches the output signal of the second magnetic head, a switching signal generator that controls the switching circuit, a frequency demodulation circuit, a low-pass filter, a delay circuit that delays by one horizontal synchronization period, and a second switching circuit that switches the output signal of the second magnetic head. a switching circuit and a second
The present invention is characterized in that the first control signal and the second control signal are synchronized.

Effect of the Invention With the above-described configuration, the present invention replaces the noise portion of the video signal caused by the discontinuity of the RF multiplied signal phase that occurs when switching the reproduced RF signal for each field by converting it into a portion corresponding to that one horizontal synchronization period before. It is replaced by .

EXAMPLE Hereinafter, an example of the present invention will be described with reference to FIGS. 1 and 2. In FIG. 1, a magnetic head 1
．． 2, the RF multiplied signal recorded on the magnetic recording medium is reproduced, and the switching circuit 3 switches the RF multiplied signal every field. The switching circuit 3 is controlled by a control signal generator 8. This output is demodulated into a video signal by the frequency demodulation circuit 4,
A low-pass filter 5 removes frequency components twice the carrier wave. This video signal passes through a circuit consisting of a delay circuit 6 that delays one horizontal synchronization period and a switching circuit 7, and is output to a monitor (not shown). This switching circuit 7 is controlled by a control signal generator 9, and the signal of the control signal generator 9 is synchronized with the signal of the control signal generator 8.

The operation in the above configuration will be explained. magnetic head 1.2
When the RF multiplied signal is reproduced from the magnetic recording medium and the switching circuit 3 is switched with a control signal as shown in FIG. 2(a), the RF
A phase discontinuity A occurs in the doubled signal C1. When demodulated into a video signal by this RF double signal frequency demodulation circuit 4, it becomes a video signal (like dl that includes noise B). Since tel passes through the low-pass filter 5 (it is delayed from cl by the delay time τ of the low-pass filter 5) The control signal generator generates a width 1 (1>
τ) to control the switching circuit 7.

The switching circuit 7 is supplied with the output signal of the low-pass filter 5 as shown in FIG. 2 and a signal obtained by delaying the output signal of the low-pass filter 5 as shown in FIG. has been done.

Since the switching circuit 7 is controlled by the control signal shown in FIG. 2 (bl), its output signal is the noise B shown in FIG. The result will be a video signal that does not match.

As described above, according to the video signal processing device according to the embodiment of the present invention, a noise-free video signal can be obtained by replacing the noise portion of the video signal with a portion corresponding to one horizontal synchronization period earlier.

Effects of the Invention As is clear from the above explanation, according to the present invention, the noise in the video signal caused by the discontinuity of the RF multiplied signal phase that occurs when switching the magnetic head output is reduced one horizontal synchronization period before. Since the noise can be removed by replacing a considerable portion of the video signal, a good screen without noise can be obtained even on a large screen.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a video signal processing device according to an embodiment of the present invention, FIG. 2 shows signal waveforms of each part of the device, and FIG.
The figure is a block diagram of a conventional video signal processing device. 6...1 horizontal synchronization period delay circuit, 7...
-Switching circuit, 9...control signal generator. Name of agent: Patent attorney Haruaki Ogata

Claims (1)

[Claims] The first frequency-modulated video signal is different for each field.
In a magnetic recording and reproducing device that performs recording and reproducing using a second magnetic head, the first and second magnetic heads;
a first switching circuit that switches the output signal of the second magnetic head, a switching signal generator that controls the switching circuit, a frequency demodulation circuit, and a low-pass filter;
It has a delay circuit that delays by one horizontal synchronization period, a second switching circuit, a first switching that switches the second, and a switching signal generator that controls the switching circuit, and includes a first control signal and a second switching circuit. A video signal processing device characterized in that two control signals are synchronized.