JPS59140781A - Video signal processing circuit - Google Patents

Abstract

PURPOSE:To reduce the input terminals of an integrated circuit in number by switching output terminal in responding to recording/reproducing switching signals which indicate recording operation and reproducing operation and outputting signals, and impressing a clip level control signal in recording operation and a pseudo vertical synchronizing signal in reproduction. CONSTITUTION:The output of the 2nd selecting circuit 26 is inputted to a white clipping circuit 5 during recording by a switching reproduction signal inputted from a terminal 21 and level control over while clipping is performed there. The pseudo vertical pulse, on the other hand, is applied from a terminal 41 to the 2nd selecting circuit 26, but this signal is cut off by the recording/reproducing switching signal and not transmitted. This pseudo vertical pulse is not cut off and added to a video signal during reproduction.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a video signal processing circuit for a video tape recorder, and particularly to a luminance signal processing circuit.

Configuration and Problems of Conventional Example A block diagram of the luminance signal system of a conventional video tape coder is shown in FIG. The video signal input is separated into a luminance signal component by a low-pass filter 1, and the separated luminance signal component is shaped into a luminance signal with a constant synchronizing signal voltage by an automatic gain control circuit 2, and then by a clamp circuit. 3, the DC voltage of the synchronizing signal section is made constant. The pre-emphasis circuit 4 emphasizes the high range of the luminance signal, the white dark clip circuit 5 clips the overshoot portion of the luminance signal according to the control voltage applied to the terminal 23, and the FM modulation circuit 6 clips the overshoot portion of the luminance signal. , the FM luminance signal is FM modulated, a high-pass filter 7 creates a low-frequency chroma signal part, a recording amplification circuit 8 amplifies the FM luminance signal, and the 11 or more signals recorded on the head 9 are used as a luminance signal recording system. be.

Next, the luminance signal reproduction system will be explained. A playback signal is taken out from the head 9, a playback preamplifier circuit 10 amplifies the playback signal, a head switching circuit 11 switches the head channel, a high-pass filter 12 separates the luminance signal component, and a drop The dropout portion is compensated by the out compensation circuit 13, and the F
The M demodulation circuit 15 converts it into a video luminance signal, and the low-pass filter 16 creates a high-frequency chroma signal.
A de-emphasis circuit 17 returns the high frequency range to its original level, a noise removal circuit 18 reduces noise, and an output amplification circuit 19 amplifies and outputs the signal. Incidentally, during special reproduction in which the tape is reproduced at a tape speed different from that during recording, a pseudo vertical pulse is inputted from the terminal 22 and combined with the video signal. Still, pre-emphasis circuit 4, de-emphasis circuit 1
A recording/reproduction switching signal used in γ is input from a terminal 21.

Here, as shown by the broken lines in FIG. , consisting of a one-chip integrated circuit device 24 (hereinafter referred to as IC),
The noise removal circuit 18 and the output amplification circuit 19 are separate ICs 25
It consisted of

However, as mentioned above, the conventional method requires two ICs, the IC 24 and the IC 26, which has the disadvantage of increasing the number of parts. On the other hand, in video tape recorders, there is a demand for reducing the number of parts in order to promote miniaturization and weight reduction. Unfortunately, when IC24 and IC25 are configured as one chip, there is a drawback that the number of input terminals increases.

OBJECTS OF THE INVENTION The present invention is intended to eliminate such problems, and to provide a video signal processing circuit using an integrated circuit device with increased integration and a reduced number of input/output terminals.

Structure of the Invention The video signal processing circuit of the present invention converts a signal applied to a first input terminal into a recording/reproducing switching signal applied to a second input terminal indicating recording/reproducing. A selection circuit that switches output to the first output terminal and a second output terminal during playback, a dark clip circuit or a white clip circuit connected to the first output terminal, and a selection circuit connected to the second output terminal. and a pseudo vertical synchronization signal mixing means, which applies a crib level control signal during recording and a pseudo vertical synchronization signal during playback to the first input terminal, and is characterized in that the integrated circuit This allows the number of input terminals to be reduced.

DESCRIPTION OF THE EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. 2 and 3.

FIG. 2 is a block diagram of a luminance signal system of a video tape recorder using an integrated circuit device which is an embodiment of the present invention;
FIG. 3 is an equivalent circuit diagram of a portion of the same circuit device.

In FIG. 2, blocks 1 to 19 are the same as the blocks in FIG. 1 and are connected in the same way.

25 in the figure is a first selection circuit, and an actual circuit example thereof is shown in FIG. Furthermore, 26 in FIG. 2 is a second selection circuit, and an equivalent circuit diagram of 26 is shown in FIG. The first selection circuit 26 and the second selection circuit 26 are connected through a terminal 41 that shares the control of the clip level and the input of the pseudo vertical pulse. Further, the second selection circuit 26 is connected to a recording/reproduction switching signal input terminal 21 . As shown in FIG. 3, the first selection circuit 25 includes a variable resistor 34 that controls the clip level of the white clip circuit 6 during recording, and a variable resistor 34 that controls the clip level of the white clip circuit 6 during recording.
6, a diode 44 blocking current flow so as not to change the base voltage of the transistor 32;
Also, a transistor 39 to which a pseudo vertical pulse is input to the base, and a resistor 4 for dividing the power supply voltage during reproduction.
It consists of 3゜i5. The second selection circuit 26
As shown in the figure, transistor 3 forming the differential amplification word
1 p 32, transistors 28 and 29 that function as switching, and emitter follower transistor 27.
33.38, Inverting amplification transistor 30.36, 37
．． It consists of 40.

Next, the operation of this device will be explained.

During recording, the power supplied only during recording is connected to variable resistor 3.
4 is input to the base of the transistor 32 through the level control and pseudo vertical voltage input terminal 41 of the white clip circuit 5.
．． A differential amplifier 32 outputs the signal to the collector of the transistor 31. During recording, the transistor 28 is turned off by a recording/reproducing switching signal inputted from the recording/reproducing switching signal terminal 21. Therefore, the collector output of the transistor 31 is input to the base of the transistor 27, level-shifted, and the transistor 27
The signal is output to the emitter of and input to the white clip circuit 6. Here, the voltage input to the white clip level control and pseudo vertical pulse input terminal 41 is also input to the base of the transistor 33. However, since the recording/reproducing switching signal inputted from the recording/reproducing switching signal input terminal 42 turns on the transistor 9, the input to the base of the transistor 30 is cut off, and no signal is transmitted.

During playback, a pseudo-vertical pulse is input to the honocrit adjustment and pseudo-vertical pulse input terminal 41 by the power supply supplied only during playback and the pseudo-vertical pulse input to the base of the switching transistor 390, and this is applied to the transistor 40.30. After being inverted and amplified twice at , it is added to the video signal. During reproduction, the recording/reproducing signal input to the recording/reproducing switching signal terminal 42 turns off the transistor 29 and turns on the transistor 28 . As a result, the signal of the pseudo-vertical pulse is transmitted without being blocked by the transistor 29. Is there a transistor in the white clip circuit? Since the signal is blocked by 8, the pseudo vertical pulse input is not input.

Note that in this embodiment, the level adjustment terminal of the white knob 1 knob circuit and the pseudo vertical node input terminal are shared, but the level adjustment terminal of the dark knob 1 knob circuit and the pseudo vertical node input terminal are shared. It can also be shared with other users in the same way.

Effects of the Invention As described above, according to the present invention, it is possible to provide a video signal processing circuit using an integrated circuit device with an increased degree of integration and a reduced number of input/output terminals.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a luminance signal system of a video tape recorder using a conventional integrated circuit device, and Fig. 2 is a block diagram of a luminance signal system of a video tape recorder using an integrated circuit device according to an embodiment of the present invention. 3 is an equivalent circuit diagram of a portion of the block diagram of FIG. 2. 1...Low pass filter, 2...
Automatic gain control circuit, 3... Clamp circuit, 4.
...Pre-emphasis circuit, 5 ... White/dark clip circuit, 6 ... FM modulation circuit, 7 ... High-pass filter, 8 ...・
... Recording amplifier circuit, 9... Head, 1o...
... Reproduction preamplifier circuit, 11... Head switching circuit, 12... High-pass filter, 13.
...Dropout compensation circuit, 14...
Limiter, 15...FM demodulation circuit, 16...
...Low pass filter, 17... De-emphasis circuit, 18... Noise removal circuit, 19
... Output amplification circuit, 20 ... Recording/playback switching circuit, 21... Recording/playback switching signal input terminal, 22... Pseudo vertical pulse input terminal, 23・
... Clip circuit adjustment terminal.

Claims (1)

[Claims] The signal applied to the first input terminal is output to the first output terminal during recording and to the second output terminal during playback, depending on the recording/reproduction switching signal applied to the second input terminal indicating recording and reproduction. a selection circuit for switching output to each output terminal;
a dark clipping circuit or a white clipping circuit connected to the output terminal of the circuit, and a pseudo vertical synchronization signal mixing means connected to the second output terminal, and a clip level control circuit connected to the first input terminal during recording. A video signal processing circuit characterized in that a pseudo vertical synchronization signal is applied to each signal during playback.