JPS6193793A - Magnetic recording method - Google Patents

Abstract

PURPOSE:To prevent color noises at overlapped part in case of joint pickup of a fade-out and a fade-in video signal by recording a color burst while suppressing the recording level of the burst during the period of fade-out. CONSTITUTION:A low frequency conversion color signal inputted from a terminal 21 is mixed with a luminance FM signal 25 by a transistor (TR)28 via an LPF22 and TRs 26, 27 and fed to a recording amplifier circuit 29. In recording a fade-out video signal, a signal shown in figure is fed to a fade-out control signal input 23 and when the value of the bias resistor 24 is selected so as to turn on the TR29 with a DC level of the control signal exceeding a point B, the TR29 is turned on during the period B-C and a color signal is not obtained as the output of the TR27. Thus, the overlapped write of the color burst signal in recording the fade-out video signal is prevented, and color noise generation is suppressed at fade-out and fade-in joint pickup recording.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a magnetic recording method for recording video signals by a fade-out operation, which is one of the special recording methods in a VTR.

A conventional magnetic recording method for recording and reproducing video signals by a fade-out operation will be described below.

Figure 1 shows the change in the video signal brightness level due to a conventional fade-out operation, and the time from the start of the fade-out operation from state A to the completion of the fade-out is approximately 4 hours. ~6 seconds. In the state of Ha,
There is no brightness signal and only the 9 synchronization signal and color burst signal are left.

When recording a fade-out video signal as shown in FIG. 1, a problem arises when, after fade-out recording, the recording state is temporarily stopped and the video signal is recorded again. The state at this time will be explained using FIG. 2.

Fig. 2 shows an example of a tape running system of a VTR, in which 1 is a rotary cylinder, 2 is a video head, 3 is a video chive, 4 is a full-width erasing head, 6 is a guide post, and 6 is a conical guide. .

If the video head 2 records a fade-out signal as shown in FIG. 1 after all conventionally recorded patterns on the tape are erased by the full-width erase head 4, at the end of the recording, Only the synchronization signal and color burst signal as shown in Fig. 1C will be recorded.

If you try to record the entire video signal again after stopping the recorded sound, if you continue recording from the previous recording stop position (human dot in Figure 2), the start-up of the capstan servo or the start-up of the video signal circuit will cause , there is no continuity between the previously recorded track and the newly recorded track, and when the joint is played back, the discontinuous portion appears as noise.

In order to solve this problem, with current VTRs, when recording is stopped, the tape is rewound to point 0 in Figure 2, the tape is stopped at this position, and when recording is started again, it runs to point B. During this time, continuity of recording and tracking is maintained.

At this time, the period from the human point to the full-width erase head 4 is 1 month 4 to record a new signal on top of the previously recorded signal.
831. @M＊yj, □. 6. I'm in that state.

If the previously recorded signal is a fade-out signal, the sync signal and color burst signal remain in the overwritten portion from point A to the full-width erase head 4. A new video signal is recorded on top of this signal,
The problem here is a signal with a long wavelength (629KH in the VH3 system) such as a low-frequency conversion color burst signal.
In the z, β system, 688K [1z] is recorded deeply in the magnetic layer of the video tape, so it cannot be erased sufficiently even if it is overwritten with a short wavelength signal such as a luminance signal. A particular problem arises when the signal to be overwritten is a fade-in video signal and the timing of the previously recorded signal and the vertical synchronization signal are out of sync.

FIG. 3 shows an example of a magnetic tape recording pattern, where a is an odd field pattern, b is an even field pattern, C is a full-width erase head in the tape running direction 4;
This is the same as the entry point in FIG. 2, and is the recording start position when recording the next video signal, and the period from M to 4 is the overwriting period.

When recording a fade-in video signal from a person's position,
If the timing of the vertical synchronization signal of that signal starts from even field b, there will be no problem, but if it starts from odd field b, as shown in Figure 4, the overwriting period will be different from the regular color burst. , one more color burst will be recorded during the horizontal scanning period,
When this joint portion is played back, color noise will occur on the monitor screen. The timing of this recording start is irregular, and the occurrence of color noise cannot be suppressed. Furthermore, color noise is most noticeable when the fade-out video signal and the fade-in video signal are spliced 9.

OBJECT OF THE INVENTION The present invention solves the above-mentioned conventional problems, and provides a magnetic recording method that does not generate color noise in the overwritten portion when recording a fade-out video signal and a fade-in video signal in succession. The entire purpose is to provide.

Composition of the Invention The present invention is a magnetic recording method characterized in that a color burst signal is suppressed and recorded in response to a command signal for controlling a fade-out operation when recording a fade-out video signal. This prevents color noise from occurring during continuous fade-out and fade-in shooting by preventing double color burst recording of a portion.

DESCRIPTION OF EMBODIMENTS FIG. 5 shows a block diagram embodying a magnetic recording method in an embodiment of the present invention.

In FIG. 6, 1 is a video signal input terminal, 2 is a low-pass filter, 3 is a GC circuit, 4 is an FM modulation circuit, 5 is a mixing circuit, 6 is a band-pass filter, 7 is a balanced modulation circuit,
8 is a fixed oscillator, 9 is a low-pass filter, 1o is a color output control circuit, 11 is a fade-out control signal sent from the system control circuit, 12 is a recording amplifier circuit, and 13 is a video head.

The operation of the magnetic recording method of this embodiment configured as described above will be described below.

The video signal input from 1 is separated into a luminance signal and a color signal by a 2.6 filter. The luminance signal is 2,
It is FM modulated by the circuit 3.4 (level control) and enters the mixing circuit 5.

On the other hand, the color signal is low frequency converted by 7 balanced modulation circuits, mixed with the luminance signal, and then passed through all 12 recording amplifier circuits.
3 video head records on the magnetic tape. The above is for a normal video signal, but if the signal to be recorded is a fade-out video signal, a control signal as shown in Figure 6 is sent to the 10 color output control circuits (syscon circuit = 9). . In FIG. 6, M is the fade-out start position, C is the end position, and the period between B and 0 is the overwriting period. When the output of 10 is stopped during the period from when the fade-out control signal reaches point B to when it reaches point 0, the mixing circuit 5 receives a color signal (here, ("7-''-X
) M"y) Iti?s') Rfx n・Next, a specific example of this color output control circuit will be explained.

In FIG. 7, 21 is a low frequency conversion color signal input terminal;
22 is a low-pass filter, 23 is a fade-out video signal input, 24 is a bias resistor, 25 is a 7M modulated wave input, 26 to 29 are transistors, and 30 is a recording amplifier circuit.

The low-pass conversion color signal inputted from 21 passes through a low-pass filter 22, passes through transistors 26 and 27, and is converted to a luminance FM signal 25 and MI! by a transistor 28. and is applied to the recording amplification circuit 29.

However, when recording a fade-out video signal, 2
A control signal as shown in FIG. 6 is added to 3.
When the DC level of the control signal exceeds point B, the transistor 29 is turned on (if the value of the ear resistor 24 is determined, the transistor 29 is turned on during the period B and C in Figure 6), and the color is turned on. No signal is available as the output of transistor 27.

Effects of the Invention As described above, the present invention controls the output of the color output circuit using the fade-out control signal, thereby overwriting the color burst signal in the case of recording a fade-out video signal. It is possible to prevent color noise from occurring when recording continuous shots of fade-outs and fade-ins.

[Brief explanation of the drawing]

Figure 1 is a signal waveform diagram showing changes in brightness of the fade-out signal, Figure 2 is a configuration diagram showing an example of a VTR tape running system, and Figure 3 is a diagram of the magnetic tape pattern when recording a fade-out signal. FIG. 4 is a pattern diagram showing a magnetic tape pattern when fade-out and fade-in are taken sequentially. FIG. 5 is a block diagram of a magnetic recording method in an embodiment of the present invention. Figure 6 is a signal diagram showing an example of a fade-out control signal;
The figure is a specific circuit diagram showing a color output circuit in one embodiment of the present invention. 2.9...Low pass filter, 3...
A (lrC circuit, 4...FM modulation circuit, 5...
... Mixing circuit, 6 ... Bandpass filter, 7 ... Balanced modulation circuit, 8 ... Fixed oscillator, 10 ... Color output control circuit , 13...
...Video head. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure A Figure 4

Claims (2)

[Claims] (1) When recording a video signal on a magnetic recording medium, if the video signal to be recorded is a faded out signal, the recording level of the color burst is suppressed during the fade out period. A magnetic recording method characterized by: (2) The magnetic recording method according to claim 1, wherein a command signal for controlling fade-out is used when suppressing the recording level of the color burst signal.