JPS6096084A - Video-signal reproducer - Google Patents

Abstract

PURPOSE:To suppress the noise in a luminance signal obtained from a reproduction video signal by switching and controlling a change-over circuit by a switching pulse, and by substituting the signal part around the switching time point of the reproduction video signal from plural rotational magnetic heads in the luminance signal for the output of an integrating circuit. CONSTITUTION:In a switching pulse forming circuit 14, a change-over signal (a) is supplied to an integrating circuit 12 which is composed of a register 10 and a condenser 11; the output of the change-over signal (a) and the integrating circuit 12 is supplied to an exclusive ''or'' circuit 9, and its output is supplied to an amplifier circuit 13 and amplified. A switching pulse (c), which is obtained at the output side of the amplifier circuit 13, rises at the change-over time (t) of the change-over signal (a), and its pulse width is a little wider than gamma. In a change- over circuit 2, its moveable contact 5 is always connected to a stationary contact 3 side, the contact 5 is switched to a stationary contact 4 side only at the time of the switching pulse (c) arrival, and a luminance signal (e), which is suppressed to the noise (n) having a small peak-to-peak value, is outputted.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a video signal reproducing apparatus which switches and outputs reproduced video signals from a plurality of rotating magnetic heads.

BACKGROUND TECHNOLOGY AND PROBLEMS In a conventional VTR, a pair of rotating magnetic heads divided by approximately 180 angles is provided on a tape guide drum, and during recording, each pair of rotating magnetic heads alternately scans one field of a video signal. are recorded on a magnetic tape so as to sequentially form one recording track diagonally with respect to the longitudinal direction of the magnetic tape, and during reproduction, each recording track on the magnetic tape is alternately reproduced by a pair of rotating magnetic heads. , the reproduced video signal is switched and outputted for each field within the vertical blanking section.

Therefore, the FM modulated luminance signal in the reproduced video signal is
Within the vertical blanking section of the luminance signal obtained by M demodulation,
Noise occurs due to transients or discontinuities in the FM carrier due to switching of the reproduced video signal, causing synchronization disturbance.

Conventionally, in order to eliminate or suppress such noise, switching pulses created based on the switching signals of the reproduced video signals from a pair of rotating magnetic heads are supplied to a 1° dropout compensation circuit to generate a brightness signal. The noisy signal portion of the luminance signal was replaced with the signal portion before IH() (where horizontal period).

However, such conventional devices have the following problems.

In other words, when the switching signal and the playback video signal are phase-locked, the time point at which the noise occurs is within the 3H equalization pulse approximately 2.25H before the leading edge of the vertical synchronization signal, and the noise occurs in the luminance signal. The signal portion is replaced with a part of the video signal, and the level of the replaced signal portion is therefore significantly different from the original level, which is not desirable in terms of standards.

In addition, if the above-mentioned phase lock is off, the switching point of the switching signal may fall within the vertical synchronization signal of the luminance signal, and in that case, the noisy signal part of the luminance signal may be significantly higher than the original level. There is a risk that the pedestal may be replaced at a different pedestal level, and in this case, it is not only unfavorable in terms of standards, but also
This will lead to a new synchronization disorder.

Purpose of the Invention In view of the above points, the present invention provides a video signal reproducing device which switches and outputs reproduced video signals from a plurality of rotating magnetic heads, and provides a video signal obtained from the reproduced video signals by switching the reproduced video signals. The present invention attempts to propose a method that can suppress noise in a luminance signal without substantially changing the original level of the signal portion in which the noise is mixed.

SUMMARY OF THE INVENTION The present invention provides a video signal reproducing device that switches and outputs reproduced video signals from a plurality of rotating magnetic heads. An integrating circuit to which a luminance signal is supplied, a switching circuit that switches the output of the luminance signal and the integrating circuit, and a switching pulse that is generated near the switching point based on the switching signal that switches the reproduced video signals from the plurality of rotating magnetic heads. The switching circuit is controlled by the switching pulse from the switching pulse forming circuit, and the signal portion of the luminance signal near the switching point of the reproduced video signal from the plurality of rotating magnetic heads is outputted from the integrating circuit. This is done in such a way that it can be replaced.

According to the present invention described above, in a video signal reproducing device configured to switch and output the reproduced video signals from a plurality of rotating magnetic heads, the luminance signal obtained from the reproduced video signal by switching the reproduced video signals. This makes it possible to suppress noise without substantially changing the original level of the signal portion in which the noise is mixed.

Embodiment An embodiment of the present invention will be described below with reference to FIG. This embodiment is a case in which the present invention is applied to the two-head type VTR mentioned at the beginning. In Figure 1, s Tl p
T2 is an input terminal, and T3 is an output terminal.

An FM modulated luminance signal in the reproduced video signal is supplied to the input terminal T1. A switching signal a (see FIG. 2A) of the reproduced video signal is supplied to the input terminal T2.

The noise-suppressed luminance signal e (second
(see Figure E) is output.

The FM modulated luminance signal (b) from the input terminal T1 is supplied to the FM demodulator (including a capacitor coupling circuit) (1) and is FM demodulated, resulting in a luminance signal b (see Figure 2B).
is a switching circuit (actually a semiconductor switch circuit) (2) comprising fixed contacts (3), (4) and a movable contact (5).
is supplied to the fixed contact (3).

As shown in Figure 2B, this luminance signal is
is the 3H vertical synchronization signal, EP is the previous 3H equalization pulse, and ■S is the video signal. When the switching signal a and the luminance signal S are phase-locked, the noise N is generated 2.25H before the leading edge of the vertical synchronizing signal VD. The generation point of this noise N is delayed by τ from the switching point t of the switching signal a, and after this delay &1 the FM modulated luminance signal passes through a hash filter, a filter, an equalizer, etc.
This is because the signal is supplied to the input terminal T1.

This luminance signal is an integrator circuit (the DC component is cut) (
6) and is integrated, then supplied to an amplifier circuit (7) and amplified. In the output d of this amplifier circuit (7) (see the second diagram), the noise N of the luminance signal is at its peak -
Noise n whose peak value is significantly reduced by integration
is changing. In addition, the time constant of this integrating circuit (6) is
So that the peak-to-peak value of the noise n is as small as possible,
Set it small.

The output d of the amplifier circuit (7) is supplied to a DC level adjustment (setting) circuit (8), and the DC level is adjusted so that its pedestal level matches the pedestal level of the luminance signal obtained from the FM demodulation circuit (IJ). After the adjustment (setting) is carried out, it is supplied to the fixed contact (4) of the switching circuit (2).

The switching signal a (see Fig. 2 A) from the input terminal T2 is supplied to the switching pulse forming circuit αa, and the switching pulse C obtained from this (see Fig. 2 C and capacitor Q) is supplied to the switching pulse forming circuit αa.
is supplied to an integrating circuit a2 consisting of υ.

The switching signal a and the output of the integrating circuit Q are supplied to an exclusive OR circuit (9), and the output thereof is supplied to an amplifier circuit α for amplification. As shown in FIG. 2C, the switching pulse C obtained at the output side of the amplifier circuit a rises at the switching time t of the switching signal a, and its pulse width is τ. It is a slightly wider pulse.

Thus, in the switching circuit (2), the movable contact (
5) is always connected to the fixed contact (3) side, and is switched to the fixed contact (4) side only when the switching pulse C arrives. Thus, the output terminal T3 outputs a luminance signal e (see FIG. 2 E) in which the peak-to-peak dog noise N is suppressed to the small peak-to-peak noise n. .

Note that the number of rotating magnetic heads may be greater than two.

According to such a video signal reproducing apparatus, in a video signal reproducing apparatus which switches and outputs reproduced video signals from a plurality of rotating magnetic heads, it is difficult to determine at which position in the luminance signal the switching point of the switching signal is located. Regardless, it is possible to suppress the noise in the luminance signal obtained from the reproduced video signal by switching the reproduced video signal without changing the original level of the signal portion in which the noise is mixed. can get things.

Effects of the Invention According to the present invention described above, in a video signal reproducing apparatus which switches and outputs reproduced video signals from a plurality of rotating magnetic heads, it is possible to determine at which position of the luminance signal the switching point of the switching signal is. To suppress noise in a luminance signal obtained from a reproduced video signal by switching the reproduced video signal, regardless of whether the noise is present, without substantially changing the original level of the signal portion in which the noise is mixed. You can get what you can.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of a video signal reproducing apparatus according to the present invention, and FIG. 2 is a waveform diagram for explaining the same. (1) is an FM demodulation circuit, (2) is a switching circuit, (6) is an integrating circuit, and I is a switching pulse forming circuit.

Claims (1)

[Claims] In a video signal reproducing device configured to switch and output reproduced video signals from a plurality of rotating magnetic heads, a luminance signal obtained by FM demodulating an FM modulated luminance signal in the reproduced video signal is supplied. an integrating circuit, a switching circuit for switching the luminance signal and the output of the integrating circuit, and a circuit for forming a switching pulse generated near the switching point based on the switching signal for switching the reproduced video signals from the plurality of rotating magnetic heads. Then, the switching circuit is switched and controlled by the switching pulse from the switching pulse forming circuit, and the signal portion of the luminance signal near the switching point of the reproduced video signals from the plurality of rotating magnetic heads is outputted from the integrating circuit. A video signal reproducing device characterized in that the video signal is replaced by the following.