JPS60171879A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To prevent an inversion phenomenon by detecting a high frequency component from a video signal, superimposing the component at the horizontal blanking period of the video signal and applying the result with FM modulation for recording. CONSTITUTION:A video signal 1 is led to an HPF7 and a high frequency component is extracted. This signal is used as position information by a position detector and fed to a data encoder 10. Moreover, a signal 1 is fed to a Y comb line filter 5 and a luminance level detector 6 outputs a level just after a limiter outut is detected to the data encoder 10. The encoder 10 encodes the information and superimposes it at the horizontal blanking period by a data superimposing device 2.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a video signal inversion compensation circuit in a magnetic recording/reproducing device.

[Technical background of the invention and its problems]

In a magnetic recording/reproducing device, if an imbalance occurs between the upper and lower sidebands of the reproduced FM signal, distortion occurs in the rising part of the video signal from black to white, where part of it does not reach the zero level and is captured. If the signal is passed through the limiter as it is, the zero-crossing point with information on the rising edge will be lost, causing a so-called inversion phenomenon.

As a means to prevent this reversal phenomenon, there are methods such as using a double limiter in the demodulation circuit, but there is no complete reversal prevention measure yet.

[Purpose of the invention]

The present invention has been made in view of these points, and an object of the present invention is to provide a magnetic recording/reproducing apparatus equipped with a reversal phenomenon compensation circuit that can completely compensate for reversal.

[Summary of the invention]

The present invention detects high frequency components of a video signal during recording, reads the position within the horizontal synchronization period and the level immediately after that, and converts each information into several bits of data to be detected. Superimposed on the horizontal blanking period of the video signal of the synchronization period, FM modulated and recorded on a magnetic recording medium,
During reproduction, the reproduced signal is FM demodulated to separate the data of the horizontal blanking period, and this data is returned to position/level information, and the inversion is detected from the FM (lfi modulated signal).

When this inversion is detected, a pseudo video signal is generated from the position information and level information and inserted into the inverted portion of the demodulated signal delayed by one horizontal opening period.

〔Effect of the invention〕

According to the present invention, the one-inversion phenomenon is completely compensated for, and the video signal can be reproduced satisfactorily.

[Embodiments of the invention]

The present invention will be explained in detail below with reference to the drawings.

FIG. 1 is a block diagram of a recording section of a magnetic recording/reproducing apparatus according to the present invention.

The recording FM signal 1 is guided to the HPF 7, and high-frequency components are eliminated. This signal is further transmitted to the 'J Mitter 8, and a signal above a certain level is output. This limiter output is a part where the reversal phenomenon is likely to occur, and is treated as position information by the position detector 9, and is sent to the data encoder 1.
0.

Further, the video signal 1 is guided to a Y<L type filter 5, a luminance signal is taken out, and guided to a luminance level detector 6. The brightness level detector 6 detects I immediately after the limiter output is detected.
The RE level is output to the data encoder 10. The data encoder 10 converts the aforementioned position information/Ill and E information into data signals of several bits each.

This data encoding is performed for each horizontal synchronization period, and the data is superimposed by the data superimposition device 21 on the horizontal blanking after the video signal of the horizontal synchronization period to be coded. The encoder clock and the position detector clock are generated by a clock generator 12 in synchronization with a synchronization signal of a video signal separated by a synchronization separator 11 based on the output of an oscillator 13. When the data-superimposed signal is inserted into, for example, a front porch, it becomes as shown in FIG. 2 1al. In the figure, H is a horizontal synchronizing signal, C is a color burst signal, and 14 is superimposed data. Figure 2+b) is an enlarged view of the superimposed data section, showing the position data in the first half and the level data in the second half. The data superimposed video signal passes through a modulation process circuit 3 and is converted into a recording FM signal 4.

FIG. 3 shows a block diagram of the demodulation circuit.

The data-superimposed reproduced FM signal 15 passes through a demodulation process circuit 16 and is demodulated into a luminance signal 24.

The demodulated luminance signal is supplied to a data separator 21, and data between horizontal blankings is extracted. The extracted data is processed by the data decoder 22.

The decoded possible inversion positions and their IIV3 levels are derived. And these position and level signals are
The signal is input to the pseudo luminance signal generator 23.

On the other hand, the demodulated signal is sent to the inversion detector 171, and when one inversion is detected, the detection signal is transmitted to the pseudo luminance signal generator 23. When the inversion portion matches the positional information at the time of recording, the pseudo-luminance signal generator 23 generates a pseudo-luminance signal at the IR and E levels at the time of recording, and supplies it to the inserter 19. Inserter 19
The IH delay device 17 inserts the pseudo luminance signal into the inverted portion of the demodulated signal delayed by one horizontal opening period.

When no inversion is detected, inserter 19 does nothing to the demodulated signal. The clock necessary for the reproduction block section is generated by a clock generator 121 based on the output of the eye generator 13. Clock generation''-: 12 is the synchronous separator 11
It is locked with the synchronization signal of the demodulated signal separated by.

As shown in FIG. 1, the inversion phenomenon can be compensated for by this invention.

In the above explanation, the inversion compensation was described at one location per horizontal period, but compensation at multiple locations is also possible by increasing the number of bits.

Further, although the composite luminance signal has been taken as an example of the superimposed signal, it goes without saying that in the case of FM recording of a color difference signal, there is also a method of superimposing it on the blanking period of the color difference signal.

[Brief explanation of the drawing]

FIG. 1 is a recording circuit block diagram of a magnetic recording/reproducing apparatus of the present invention, FIG. 2 is a video signal waveform diagram with data superimposed according to the present invention, and FIG. 3 is a reproducing circuit block diagram of a magnetic recording/reproducing apparatus of the present invention. It is. 1... Recorded train signal, 2... Data superimposition device, 3...
- Modulation process circuit, 4... Recording FM signal, 5...
Y<L. shaped filter, 6... brightness level detector, 7...H
DF, 8...Limiter-19...Position detector, 10
...Data encoder, 11...Sync separator, 1
2... Clock generator, 13... Oscillator, 14...
- Superimposed data, 15... Reproduction FM signal, 16... Demodulation process circuit, 17... Inversion detector, 18... I
H delay device, 19... Enlarger, 20... Reproduction FM signal, 21... Data separator, 22... Data encoder, 23... Pseudo luminance signal generator, 24... tx
Tonal brightness signal.

Claims (1)

[Claims] An apparatus for magnetically recording and reproducing frequency-modulated acupuncture signals on a disk or tape. The iron-containing material to be recorded includes a detector that detects the high frequency component of the signal and reads the position within the horizontal synchronization period and the level immediately after that, and the position and level information of each horizontal synchronization period detected by this detector. A data encoder that operates using a clock synchronized with a video signal that converts data into a few bits of data. A superimposition circuit that superimposes the data obtained by the encoder on the horizontal blanking period of the video signal of the detected synchronization period, and a recording circuit that frequency-modulates the video signal with this data superimposed and records it on a magnetic medium. A circuit that reproduces a signal from the recording medium and demodulates its frequency; a separation circuit that separates horizontal blanking period data of the demodulated signal; and a data decoder that returns the separated data to position and level information. A pseudo image signal generator that generates a pseudo image signal based on the image information of the data decoder; a detector that detects an inversion phenomenon from the demodulated signal; A magnetic recording and reproducing apparatus comprising: a circuit for inserting the bond-simulating one-image signal into a video signal delayed by one horizontal period.