KR940004269Y1 - Stability circuit of display picture of video diproductor - Google Patents

Abstract

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Description

Playback screen stabilization circuit of video player

1 is a reproduction screen stabilization circuit diagram of the present invention.

FIG. 2 is a waveform diagram of each part of FIG. 1 (a)-(e) and FIG.

* Explanation of symbols for main parts of the drawings

1: Head Switching Signal Differentiator 2: Pseudo Vertical Synchronous Signal Generator

3: dropout detection unit 4: integrator

5: Schmitt trigger unit 6: Output control unit

7 video signal demodulator 8 mixer

9: Buffer HS: Head Switching Signal

The present invention stabilizes the playback screen of a video player that generates a pseudo vertical synchronization signal and stabilizes the playback screen when the video tape is played in a video player such as a video tape recorder capable of playing back video signals recorded on a video tape. It is about a circuit.

Conventional video players generate pseudo vertical synchronizing signals separately and mix them with the reproduced video signal regardless of the state of the reproduced video signal when shifting the videotape such as high speed forward search playback, high speed reverse search playback, slow playback, and still playback. I was.

At this time, the pseudo vertical synchronization signal is always generated at the timing using the control signal reproduced from the video tape, so that the state of the playback screen is substantially stabilized. However, the pseudo vertical synchronization signal is controlled by the basic timing of the control signal. The timing of stabilization of the playback screen is somewhat late due to the generation of the signal, and even when the playback video signal is clean, the pseudo vertical synchronization signal is generated and mixed to harm the playback screen.

When the video tape is played at a constant speed, the original vertical sync signal mixed with the reproduced video signal is output as it is, without generating a pseudo vertical sync signal. Therefore, the video signal recorded on the video tape is poor. When the state of the vertical synchronization signal of the video signal is bad, there is a problem such that the playback screen flows up or down.

Therefore, an object of the present invention is to generate a pseudo vertical synchronous signal using a head switching signal, and detect a drop out portion of a reproduced video signal regardless of the constant speed reproduction and the variable speed reproduction of a video tape, and only when a drop out occurs. The present invention provides a playback screen stabilization circuit which mixes a vertical synchronization signal with a playback video signal so that the playback timing is stabilized quickly and the playback screen is stabilized.

The reproduction screen stabilization circuit of the present invention having such a purpose differentiates the rising section and the falling section of the head switching signal respectively, mixes and shapes them to generate a pseudo vertical synchronization signal, and reproduces the generated pseudo vertical synchronization signal. The playback picture is stabilized by mixing instead of the original vertical synchronizing signal mixed in the.

In particular, the present invention detects the dropout of the reproduced RF video signal irrespective of the constant speed reproduction and the variable speed reproduction, and mixes the pseudo vertical synchronization signal with the reproduced image signal during the detected dropout period, thereby performing constant speed reproduction and variable speed reproduction of the video tape. Regardless, the playback screen becomes stable.

Hereinafter, a reproduction screen stabilization circuit of the present invention having the above purpose will be described in detail with reference to the accompanying drawings.

1 is a reproduction screen stabilization circuit diagram of the present invention, as shown therein, resistors R ₁ -R ₅ and transistors TR ₁ which differentiate and output the rising and falling sections of the head switching signal HS. And a comparator for outputting a pseudo vertical synchronization signal by shaping the output signal of the head switching signal differentiator 1 and the head switching signal differentiator _{1 with} condensers C ₁ and C ₂ and diodes D ₁ and D ₂ . (COMP ₁ , COMP ₂ ), a pseudo vertical synchronous signal generator (2) consisting of resistors (R ₆ -R ₉ ) and condensers (C ₃ ), and a dropout of a reproduced RF video signal reproduced from a video tape. An integrator ₄ composed of a resistor R ₁₀ and a capacitor C ₄ integrating the output signal of the drop out detection unit 3 and a Schmitt inverting the output signal of the integrator 4 to detect a drop out period. The dropout period is equal to the trigger section 5 and the output signal of the Schmitt trigger section 5. Only with the pseudo vertical synchronizing signal generator (2) resistance is that the output pseudo vertical synchronizing signal (R ₁₁₎ and a transistor output control section 6 as (TR _2), the pseudo-vertical synchronizing signal generator (3) Resistor (R _12- R ₁₅ ) and transistor (TR ₃ ) for removing the vertical synchronous signal of the reproduced video signal output from the video signal demodulator 7 and mixing the pseudo vertical synchronous signal according to the pseudo vertical synchronous signal output from And a buffer (9) consisting of a transistor (TR ₄ ), a resistor (R ₁₆ , R ₁₇ ), and a capacitor (C ₅ ) for buffering the output signal of the mixer (8).

In the description of the drawings, reference numeral Vcc denotes a power supply terminal.

According to the present invention configured as described above, when the head switching signal HS is input as shown in (a) of FIG. 2 while power is applied to the power supply terminal Vcc, the input head switching signal HS is a resistor ( Inverted through an inverting amplifier consisting of R ₁ -R ₃ ) and transistor TR ₁ , as shown in FIG. 2 (b), and in FIG. 2 by a capacitor C ₁ and a resistor R ₄ . After the differentiation as shown in c), the negative differential signal is cut off, only the positive differential signal is output through the diode D ₁ , and the head switching signal HS is also the capacitor C ₂ and the resistor R ₅ . After the derivative is differentiated as shown in (d) of FIG. 2, the negative differential signal is blocked, and only the positive differential signal is output through the diode D ₂ , so that the head switching signal differential 1 is shown in FIG. As shown in the drawing, the differential signal of the rising and falling sections of the head switching signal HS is output.

In this way, the head switching signal differentiator 1 outputs the differential signal of the rising and falling sections of the head switching signal HS, and the output differential signal is the comparator COMP ₁ of the pseudo vertical synchronous signal generator 2. the inverting input terminal (-) is applied to the non-inverting input terminal (+) is applied to a reference voltage to split the power of the power supply terminal (Vcc) to the resistor (R _6, R _7), so the comparator (COMP ₁₎ is The differential signal of the head switching signal HS is compared with the reference voltage to output a pulse signal, and the output pulse signal is compared with the reference voltage by the comparator COMP ₂ to output a pseudo vertical synchronization signal.

When the reproduced RF video signal reproduced from the videotape is input, the inputted reproduced RF video signal is demodulated by the video signal demodulator 7 to output the reproduced video signal, and is inputted to the drop out detection unit 3 so as to drop out. Is detected.

Here, assuming that the a drop outro reproduced RF video signal is input as shown in the third degree (a), drop outro detection unit 3 is a constant voltage (V _D as shown in the third degree (b) ) The dropout below is detected and the pulse signal is output, and the output pulse signal is integrated through the integrator 4 as shown in FIG. Since the trigger unit 5 outputs a pulse signal as shown in (d) of FIG. 3, the transistor TR ₂ of the output control unit 6 is turned on and off while the output of the pseudo vertical synchronization signal generator 2 is output. When the signal is controlled, i.e., no dropout is generated, the Schmitt trigger unit 5 outputs a high potential, the transistor TR ₂ is turned on, and the pseudo vertical synchronous signal generator 2 outputs the pseudo vertical synchronous signal. and the ground via a transistor (TR _2), the drop outro When generated, Schmidt tree refused (5) and outputs a low potential, the transistor (TR ₂₎ is turned off is input to the pseudo vertical synchronizing signal mixer (8).

As the drop out occurs, when the pseudo vertical synchronizing signal output from the pseudo vertical synchronizing signal generator 2 is input to the mixer 8, the transistor TR ₃ is turned on by the pseudo vertical synchronizing signal to turn on the image signal demodulator. Since the original vertical synchronizing signal mixed with the reproduced video signal demodulated in (7) is grounded through the resistor R ₁₃ and the transistor TR ₃ , only the reproduced video signal in which the vertical synchronizing signal is not mixed is resisted (R _14). And a pseudo vertical synchronous signal output from the pseudo vertical synchronous signal generator 2 are output through the resistor R ₁₅ to be mixed with the reproduced video signal, i.e., a dropout occurs. The vertical synchronizing signal mixed in the control unit is removed, the pseudo vertical synchronizing signal is mixed and output, and the reproduced video signal output in this manner is output through the buffer 9.

As described in detail above, the present invention eliminates the original vertical synchronization signal mixed with the reproduced video signal when a drop out occurs regardless of the shift reproduction and the constant reproduction, and reproduces the image by mixing the pseudo vertical synchronization signal. As well as stabilization, the stabilization time is fast, so that the user can more comfortably watch the playback screen.

Claims (1)

A pseudo vertical synchronizing signal is generated by shaping the head switching signal differentiator 1 for differentiating the head switching signal HS and outputting the differential signal between the rising and falling sections, and the output signal of the head switching signal differentiator 1. Integrator 4 which integrates the pseudo vertical synchronous signal generator 2, the output signal of the dropout detector 3 which detects the dropout of the reproduced RF video signal, and the reproduced RF by the output signal of the integrator 4 The pseudo vertical synchronization signal of the pseudo vertical synchronization signal generator 2 is output only during the Schmitt trigger unit 5 for detecting the drop out period of the video signal and the output signal drop out period of the Schmitt trigger unit 5. The original vertical synchronizing signal of the reproduced video signal is removed in accordance with the output control unit 6 and the pseudo vertical synchronizing signal output from the pseudo vertical synchronizing signal generator 2, and the pseudo vertical synchronizing signal is reproduced. A playback screen stabilization circuit for a video player, characterized in that it comprises a mixer (8) mixed in a mixer.