JPH0478226B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for recording and reproducing a television composite video signal onto a magnetic disk.

[Prior Art] When one field or one frame of a television composite video signal is recorded on one track per revolution of a magnetic disk using the frequency modulation (hereinafter referred to as FM) method, the beginning and end of recording on each track are There will always be a seam between records. This recording seam appears as flickering on the television screen when played back, so the seam exists 7H (however, H is one horizontal synchronization cycle period) before the vertical synchronization signal. is set as,
Care has been taken not to appear on the actual TV screen.

[Problems to be Solved by the Invention] However, if a gap occurs at the seam of the FM recorded signal as shown in Figure 4, when it is reproduced and demodulated, the recorded seam will appear as shown in Figure Noise is generated in the vicinity including the eyes, and that noise is also generated in the sync signal part (a part lower than the pedestal level). The problem was that noise could be mistaken for an equalization pulse, disrupting vertical synchronization and causing the screen to vibrate up and down.

This invention was devised in order to eliminate these drawbacks, and it is a magnetic system that eliminates demodulation noise caused by recording seams and eliminates disturbances in vertical synchronization of composite video signals to obtain clear images. It is an object of the present invention to provide a method for recording and reproducing television composite video signals on a disk.

[Means for Solving the Problems] This invention records one field or one frame of a television composite video signal on one track per rotation of a magnetic disk using a frequency modulation method, and reads out the composite video signal from the magnetic disk. and includes at least the recording seam of the composite video signal within the range from the position of the horizontal synchronization signal that does not appear on the television screen before the vertical synchronization signal of the read composite video signal to the end of the vertical blanking period. The purpose is to superimpose a high frequency near the frequency of the carrier wave of the composite video signal, and then demodulate and reproduce the composite video signal.

Further, the present invention records one field or one frame of a television composite video signal on one track per rotation of a magnetic disk using a frequency modulation method, and also records the television composite video signal on the television screen before the vertical synchronization signal of the recorded composite video signal. Superimposing and recording a high frequency near the frequency of the carrier wave of the composite video signal so as to include at least the recording seam of the composite video signal within the range from the position of the horizontal synchronization signal that does not appear to the end of the vertical blanking period, The purpose is to demodulate and reproduce the recorded composite video signal.

[Operation] In the present invention having such a configuration, a high frequency is superimposed on the recording seam of the composite video signal read from the magnetic disk and in the vicinity thereof, thereby reproducing the composite video signal.

In addition, in the present invention, a television composite video signal is recorded on a magnetic disk, and a high frequency is superimposed and recorded in the vicinity of the recording seam of the recorded composite video signal. This ensures that there are no gaps.

[Embodiment of the Invention] An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, reference numeral 1 denotes a magnetic disk on which, for example, a television composite video signal of n fields (=n/2 frames) on n tracks is recorded using the FM method, with one field per rotation and one track.
A composite video signal recorded on the magnetic disk 1 is read by a reproduction head 2 and supplied to an adder 4 via a head amplifier 3.

The magnetic disk 1 is mounted on a flange 7 fixed to a rotating shaft 6 of a motor 5, as shown in FIG. A disk core 8 is provided at the center of the magnetic disk 1, and this core 8 is attached to the flange 7. A permanent magnet 9 is embedded in the flange 7, and a permanent magnet 9 is embedded at one point of the disk core 8.
A PG magnetic piece 10 is buried and magnetized by the permanent magnet 9. A PG coil 11 is provided above a portion through which the magnetic piece 10 passes as the magnetic disk 1 rotates. The point where the magnetic piece 10 is buried is the magnetic disk 1.
This almost coincides with the recording seam of the composite video signal of each track.

The PG coil 11 detects the passage of the magnetic piece 10 and supplies the detection output to a monostable multivibrator 13 via a pulse shaping circuit 12. The output of the multivibrator 13 is supplied to a gate circuit 14, and the gate of the gate circuit 14 is controlled to open. The gate circuit 14 receives a high frequency signal from an oscillator 15 that oscillates a high frequency near the frequency of the carrier wave of the composite video signal recorded on the magnetic disk 1, for example, a frequency corresponding to the gray color of a television signal. The gate circuit 14 opens its gate for a certain period of time in response to the output from the multivibrator 13, and during that time passes the high frequency signal from the oscillator 15 and supplies it to the adder 4. The oscillation period of the multivibrator 13 is set to, for example, several H (where 1H is one horizontal synchronization period).

The composite video signal from the adder 4 is supplied to a reproduction demodulation circuit 16. This demodulation circuit 16 demodulates the input composite video signal, and passes the demodulated signal to one contact 18 of a changeover switch 18 via a 0.5H delay circuit 17 that delays the demodulated signal by 1/2 time of the horizontal synchronization period.
a, and also directly to the other contact 18b of the changeover switch 18. The changeover switch 18 generates a switching pulse SWP that alternately goes high and low for each field.
In response to this, the contacts 18a and 18b are switched. The final reproduced composite video signal Sv is obtained from the changeover switch 18. In addition,
Here, each field is alternately delayed by 0.5H,
For example, the normal television standard format is the 1/2 interlaced format, and the NTSC
In the system, 1 frame = 2 fields, which is 525H, so 1 field = 262.5H, which results in a 0.5H shift in horizontal synchronization at the recording joint, and this is to correct this.

In the embodiment of the present invention having such a configuration, a composite video signal recorded on a certain track of the magnetic disk 1 is read out by the playback head 2, and sent to the playback demodulation circuit 1 via the head amplifier 3 and adder 4.
6. In this operation, when the magnetic piece 10 of the disk core 8 passes the position of the PG coil 11, a waveform as shown in a in FIG. 3 is generated in the PG coil 11. This waveform is the pulse shaping circuit 12
The signal is shaped into a rectangular wave as shown in FIG. As a result, the multivibrator 13 oscillates with a pulse width of several H, as shown in FIG. 3c, and controls the gate circuit 14 to open. As a result, a high frequency signal as shown in d of FIG. 3 is supplied from the gate circuit 14 to the adder 4. This timing is exactly within the range including the recording seam of the composite video signal input from the head amplifier 3. However, the output from the adder 4 at this time is in a form in which a high frequency signal is superimposed on the recording seam of the composite video signal and its vicinity, as shown in FIG. 3e. This will be displayed as gray on the screen of the television receiver. Moreover, the superposition of this high-frequency signal prevents noise from occurring in the periodic signal portion, and there is no risk of vertical synchronization being disturbed due to noise being mistakenly detected as an equalization pulse. Therefore, the screen is prevented from vibrating up and down due to the seams of recording, and a clear screen can be obtained.

In the above embodiment, the oscillator 15 is used and its frequency is set to a frequency corresponding to gray, but the invention is not limited to this. For example, when a color television is used, the color television An integer multiple of the color subcarrier (3.58MHz) of the digital signal, for example 2 times = 7.16M
Hz can also be used, and by doing so, the oscillator can be omitted.

Further, in the above embodiment, a high-frequency signal is superimposed in a range of several H before and after the seam of recording a composite video signal, but the invention is not necessarily limited to this. For example, a commercially available television receiver In some cases, the part from the leading edge of the vertical sync signal to 15H before is hidden at the bottom of the screen and is not displayed on the screen. There is no problem even if a high frequency signal is superimposed on the Further, even if the high frequency signal is superimposed on the vertical synchronizing signal, there is no problem since the vertical synchronizing signal is strong with respect to S/N, and there is no possibility that the television screen will be adversely affected by this. That is, in the present invention, at least within the range from the position of the horizontal synchronization signal that does not appear on the television screen before the vertical synchronization signal to the end of the vertical blanking period (to the end position of the equalization pulse located after the vertical synchronization signal). The high frequency signal may be superimposed so as to include the recording seam of the composite video signal.

In the above embodiment, only the television composite video signal is recorded on the magnetic disk, and after reading out the composite video signal, a high frequency signal is superimposed on the joint of the signal, but the present invention is not necessarily limited to this. Instead, a high frequency signal may be recorded in advance on a magnetic disk together with the composite video signal, with a high frequency signal superimposed on the joint of the signal. That is, a television composite video signal is recorded on a magnetic disk,
After that, at the joint of the composite video signal in each track, a high frequency signal corresponding to gray or a signal with a frequency that is an integral multiple of the color subcarrier is recorded using the same FM method as that signal recording method, and in this way, the composite video signal and the high frequency signal are superimposed. Even if the recorded data is reproduced and demodulated, it is possible to prevent noise from occurring in the synchronization signal portion, and to prevent vertical synchronization disturbance.

[Effects of the Invention] As detailed above, the present invention provides a magnetic disk that eliminates demodulation noise caused by recording seams and eliminates disturbances in vertical synchronization of composite video signals to obtain clear images. A method for recording and reproducing television composite video signals can be provided.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a schematic diagram showing the configuration of a magnetic disk section in the same embodiment, and FIG. 3 is an output waveform diagram of each part in FIG. FIG. 4 is a diagram showing a waveform near the recording seam of a composite video signal conventionally recorded on a magnetic disk, and FIG. 5 is a waveform diagram showing a conventionally demodulated composite video signal. 1... Magnetic disk, 2... Playback head, 4...
... Adder, 11 ... PG coil, 13 ... Monostable multivibrator, 14 ... Gate circuit, 16
...Regeneration demodulation circuit.

Claims (1)

[Claims] 1. One field or one frame of a television composite video signal is recorded on one track per rotation of a magnetic disk using a frequency modulation method, and the composite video signal is read from the magnetic disk and the read composite video is of the composite video signal so as to include at least the recording seam of the composite video signal within the range from the horizontal synchronization signal position that does not appear on the television screen before the vertical synchronization signal of the signal to the end of the vertical blanking period. A method for recording and reproducing a television composite video signal on a magnetic disk, which comprises superimposing a high frequency near the frequency of a carrier wave, and then demodulating and reproducing the composite video signal. 2. A television composite video signal for a magnetic disk according to claim 1, characterized in that the high frequency to be superimposed is set to a frequency corresponding to gray in the video signal or an integral multiple of the subcarrier frequency of a color television signal. How to record and play. 3 One field or one frame of a television composite video signal is recorded on one track per rotation of a magnetic disk using a frequency modulation method, and the horizontal synchronization that does not appear on the television screen before the vertical synchronization signal of the recorded composite video signal is recorded. A high frequency near the frequency of the carrier wave of the composite video signal is superimposed and recorded in a range from the signal position to the end of the vertical blanking period so as to include at least the recording seam of the composite video signal, and the recording is performed. A method for recording and reproducing a television composite video signal on a magnetic disk, which comprises demodulating and reproducing the composite video signal. 4. A television composite video signal for a magnetic disk according to claim 3, characterized in that the high frequency to be superimposed is set to a frequency corresponding to gray in the video signal or an integral multiple of the subcarrier frequency of a color television signal. How to record and play.