JPH0362797A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To enjoy a video image without color blurring on a television receiver by providing a variable delay line to an output of a reproduced color signal so as to detect the relation of time base position between a burst signal and a horizontal synchronizing signal so as to control the delay of the variable delay line. CONSTITUTION:A horizontal synchronizing signal C and a burst signal envelope B are fed to a timing detection circuit 45. Then the normal horizontal synchronizing signal obtained from the horizontal synchronizing signal and an output signal of a reference pulse generator 46 obtained from the burst signal position are compared. A timing deviation E is detected from the reference pulse D and the envelope B to obtain an output signal of the timing detection circuit 45. The output signal E decides the delay time of the variable delay line 41 and the advanced component of the reproduced color signal is corrected into the normal timing by the variable delay line 41. The output color signal of the variable delay line 41 and the luminance signal at the output of a low pass filter 35 are superimposed by a Y/C MIX circuit 36 to obtain the reproduced video output signal.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to magnetic recording and reproducing devices, particularly video tape recorders.

BACKGROUND OF THE INVENTION Recently, as the use of video tape recorders (VTRs) has expanded, their use in dubbing and editing has increased. Since the dubbing image quality deteriorates significantly at that time, improvements are desired. In particular, the time axis deviation between the reproduced color signal and the reproduced luminance signal (so-called Y/C timing deviation) increases, and if dubbing is repeated about three times, extreme color deviation may occur.

FIG. 3 shows a color signal/luminance signal processing circuit of a VTR. In FIG. 3, the cause of the Y/C timing shift is the variation in delay time of each filter in the color signal processing circuit and the luminance signal processing circuit. The signal processing operation will be explained with reference to FIG. Video input signal 1 is 2
The luminance signal is separated into a luminance signal and a color signal by an LPF of 3 and a BPF of 6, and the luminance signal is FM modulated by an FM modulator of 3, band-limited by an HPF of 4, and supplied to a recording amplifier of 5. On the other hand, the color signal is subjected to balanced modulation by the frequency converter 7 and the oscillator 8, and then passes through the LPF 9 to obtain a low-frequency color signal.The color signal then passes through the recording amplifier 5, where it is converted into a luminance FM signal and a low-frequency converted color signal. is recorded on 10 video heads after being superimposed. Also, during playback, the signal played by the video head 10 is amplified by the head amplifier 11, and the signal is amplified by the head amplifier 12.
A reproduced luminance FM signal is obtained by band separation in the PF, and a reproduced luminance signal is obtained in the 13 FM demodulators and the 14 LPF. In addition, 15 LPFs separate the reproduction low-frequency conversion color signal, 16 frequency converters, 17 reproduction variable oscillators, 1
A reproduced color signal corrected for jitter is obtained by a BPF of 8. A Y/CMIX circuit 19 mixes the reproduced luminance signal and the reproduced color signal to obtain a composite video output signal 20.

As shown in Figure 3, in a VTR, the color signal and luminance signal go through separate signal processing systems and are finally mixed to obtain a composite video output signal.
．． 4, 6.9, 12, 15゜14.18 If the delay time of each filter is not designed accurately, 19 Y/CM
Y/C timing shift occurs at IX. Furthermore, since each filter naturally has variations in delay time, variations occur in the Y/C timing between VTR devices.

Invention or problem to be solved If you dub using two VTRs, the VT
In RI, the color signal is 200ns compared to the luminance signal.
Assuming a condition where the ec timing is delayed and the color signal is delayed by 150 ns with respect to the luminance signal in VTR2, the reproduced video output signal of the VTRI is
It is supplied to the video input signal of TR2 and dubbing is performed. In this case, the Y/C timing difference of the video output signal recorded and played back by the VTR2 is 2QOnsec+150nsec.
c=35Qnsec, and a phenomenon (color streaks) in which the color signal is delayed with respect to the luminance signal can be detected on the TV screen, resulting in extremely unsightly image quality.

An object of the present invention is to automatically detect the Y/C timing shift during dubbing, correct the timing of the color signal, and obtain a reproduced video signal free of color shift.

Means for Solving the Problems The present invention is a magnetic recording and reproducing device that performs FM modulation on a video luminance signal to a high frequency, converts a video color signal to a low frequency, and records and reproduces the same on a magnetic recording medium. It is equipped with a circuit that detects the difference between the time axis of the color burst signal in the signal that has been high-frequency converted from the color signal and converted to the television color subcarrier frequency, and the time axis of the reproduced horizontal synchronization signal from the normal state. It is equipped with a circuit that changes the delay time of the color output signal depending on the output.

Effect of the present invention is that by using the configuration described in ``2'', the Y when dubbing is
/C The timing shift is automatically detected and the timing of the color signal is corrected, so that a reproduced video signal without color shift can be obtained.

Embodiment FIG. 1 shows a block diagram of a signal processing system during reproduction in a specific embodiment of the present invention. The signal reproduced by the video head 31- is band-separated by the bypass filter 33 and the low-pass filter 37, and the luminance component is separated by the FM demodulator 34 and the FM demodulator 34.
5 low-pass filter. The color signal is obtained by 38 heterodyne circuits, 39 variable oscillators, and 40 bandpass filters. At this time, the timing of the luminance signal output from the low-pass filter 35 and the color signal output from the band-pass filter 40 is at least 1 μs.
So that the ec error signal is ahead of the normal timing,
It is assumed that each filter in the reproduced signal system is designed.

As a means for detecting the progress of the color signal obtained from the band pass filter 40, a burst signal in the color signal is obtained by a burst gate circuit 42, and rectified by a detection circuit 43 to obtain an envelope waveform. A-E in Figure 1
The signals are shown as waveform diagrams in FIGS. 2A to 2E. In FIG. 2, (A) is a burst signal, (B) is a detection envelope, and the maximum point of the waveform in (B) is the burst center position.

On the other hand, when the horizontal synchronization signal in the luminance reproduction signal output from the low-pass filter 35 is extracted by the synchronization signal separation circuit 44,
This will look like (C) in Figure 2. Horizontal synchronization signal (C)
and the burst signal generator (B) are supplied to the timing detection circuit 45 (2, the normal horizontal synchronization signal obtained from the horizontal synchronization signal and the output signal of the reference pulse generator 46 obtained from the burst signal position). Compare. (D) in Figure 2 is the reference pulse;
Timing deviation ff1 (E) from (D) and (B) in the figure
is detected and used as the output signal of the timing detection circuit 45. This output signal (E) determines the delay time of the 41 variable delay lines, and the leading component of the reproduced color signal is transferred to the variable delay line 41.
Correct the timing to the normal timing. This variable delay line 4
The output color signal of No. 1 and the luminance signal of the output of the low-pass filter 35 are superimposed by the Y/CMTX circuit No. 36 to obtain a reproduced video output signal. As the variable delay line, it is possible to use a delay line for a CCD or the like, a tap-type switching delay line, etc.

Effects of the Invention If a variable delay line is provided at the output of the reproduced color signal as in the present invention, the time axis positional relationship between the burst signal and the horizontal synchronization signal is detected, and the amount of delay of the variable delay line is controlled. Even if a signal with shifted Y/C timing is reproduced due to dubbing, the variable delay line can automatically correct the timing to the normal timing, allowing you to enjoy images without color shift on your TV.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a reproducing system of an embodiment of the magnetic recording/reproducing apparatus of the present invention, FIG. 2 is a timing diagram showing waveforms of the main parts thereof, and FIG. 3 is a block diagram of a conventional example. 35...Low pass filter, 36...
Y/CMIX circuit, 40... Band pass filter, 41... Variable delay line, 42... Burst gate circuit, 43... Envelope detection circuit, 44 ......Synchronization separation circuit, 45...
- Timing detection circuit, 46...Reference pulse generator.

Claims (1)

[Claims] A magnetic recording and reproducing device that performs FM modulation on a video luminance signal to a high frequency, converts a video color signal to a low frequency, and records and reproduces it on a magnetic recording medium. Equipped with a circuit that detects the difference between the time axis of the color burst signal in the signal converted to the subcarrier frequency and the reproduced horizontal synchronization signal from the normal state, and changes the delay time of the color output signal by outputting the detection signal. What is claimed is: 1. A magnetic recording and reproducing device comprising a circuit for making the timing of a reproduced color signal coincide with the timing of a reproduced luminance signal.