JPS60136050A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To attain a framing servo function which is free from the effect of noise, etc. by producing faithfully the reference signal which detected the 1st and 2nd fields and at the same time neglecting the disturbance of the reference signal due to noise, dropout, etc. CONSTITUTION:When a switch 5 is set at the side (a), an FF2 has the same function as an FF1. Then the FF2 divides a clock input into 1/2 when the switch 5 is set at the side (b). These sides (a) and (b) correspond to output levels H and L of a comparator 6 respectively. When the pulse lacks at the point (a), the switch 5 is set at the side (b). The constants of circuits 4 and 6 are set so that the output of the circuit 6 is set at H if the H continues for a period longer than four fields. Then the output of the circuit 6 is kept at L, and the output Q of the FF2 receives no effect of noises. Then the continuance of the 1st and 2nd fields change at the middle of their courses and the output of an exclusive OR gate 3 has H continuously. Thus the output of an integration circuit 6 is set at L, and the switch 5 is changed to the side (a). Then the output of the gate 3 is changed to L and the output of the circuit 6 is changed to L after four fields. The switch 5 is changed to the side (b), and the output Q of the FF2 keeps a state where the framing is newly obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to magnetic recording and reproducing apparatuses such as broadcast and business VTRs.

Conventional configurations and their problems In recent years, broadcasting and business VTRs with editing functions have
A framing servo function has been introduced to ensure that screens at editing points are connected exactly on a field-by-field basis. In addition to editing machines, we also use portable VTRs.
Also, in home VTRs, VTRs with a connection function are used.
There are many TRs, and these VTRs are equipped with a framing servo function to eliminate image disturbances in the transition areas.

The framing servo function distinguishes between the first field and the second field in the video signal, so that no matter how many times you edit or splice, the recorded signal on the tape will always be the first, second, first field.

The second function is to connect all fields in a continuous manner, thereby ensuring that the reproduced video signal has no disturbances at the joints.

The conventional framing servo function will be described below with reference to the drawings.

FIG. 1 is a timing chart of framing.

A is video signal, CII'i video signal squid-ra-tori 1
Indicates a pressed ■ pulse. Normally, in a VTR that does not have a framing function, the pulse C is divided by a frit clock to create a % pulse D, and this is used as the standard for recording and displaying the serial number servo.In this case, the pulse D is The rise and fall of is synchronized with v nox, but
1st. There is no second field.

To establish a synchronous relationship with the first and second fields,
For example, the first field V-nogle is always set to the 7-second reference, and the pulse generated at 7 is used as the reference for the flame mink servo.

A specific example of this is shown below.

In Fig. 1, B is the HD pulse received from the video signal, C is the V/: pulse, and B and D are the second
A detector like the one shown in Figure 1 is used to detect hummum. To explain the operation below, this detector 1 detects the output of the D flip-flop 2 in FIG. 2 when the rising edge of pulse C in FIG. fd H level, outside the HD pulse width (
This Q output is taken out as the output (as a reference signal) shown in FIG. As a result, the V pulse C of the first field becomes H, and the V pulse C of the second field becomes L, thus creating a well-framed reference signal like D in Figure 1 (NTSC: 30
26 fields on PAL).

However, with the above configuration, there is no problem if the signal is in an ideal state, but if the SYNC section contains noise, it has the disadvantage of being extremely susceptible to noise. That is, there may be noise in the SYNC section, and the HSYNC that creates the HD to be compared may be instantaneously disturbed, or there may be whisker noise, etc., which may deviate from the original position. To give an example in Figure 3, if there is noise near point a in Figure 3, or if the input signal is balanced and the phase is disturbed, the reference output should be B, but the waveform shown in C is Become. In this case, if control is performed using C as a reference for the VTR, the continuity of the reference signal will be disrupted, and therefore the continuity of the cylinder servo during recording will be disrupted. Editing V
In a TR or the like, the SYNC section is likely to be disturbed due to the input signal being edited by switching signals from several VTRs (players), or the tape being damaged. The conventional framing servo method is as follows.
It has the following problems.

OBJECTS OF THE INVENTION It is an object of the present invention to provide a magnetic recording and reproducing apparatus having a framing servo function that is not disturbed by noise or bouncing of an input video signal.

Structure of the Invention In the magnetic recording and reproducing apparatus of the present invention, the framing servo device includes a circuit that separates a horizontal synchronizing signal and a vertical bright signal of a video signal, and compares the separated vertical synchronizing signal with a horizontal bright signal. By doing this, the first and second fields of the video signal are detected.
30 Hz in C.

The first to produce a ratio of 25 in PAL and SECAM.

The first means includes a switching voltage converter that can simply convert the vertical synchronizing signal into a frequency divider that divides the vertical synchronization signal by %. A slave switch is provided, and a circuit is provided to compare the phase of the output when the switch is simply on the branching device side and the output of the second means described in d. The device is configured so that the output of the first means for creating the switch is collected as a reference signal, and thereby the framing detection method allows extraction of a reference signal unaffected by noise etc. from the input video signal. This is what realizes the device.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described with reference to the drawings.

FIG. 2 shows a block diagram of a framing detector in an embodiment of the present invention. FIG. 3 shows an operation timing chart of the same embodiment.

In FIG. 2, 1 is a D flip-flop, and the D input HD is read in at the rising edge of the clock input V pulse - and is transmitted to the output Q. 2 is a D flip-flop like 1, and when switch 5 is on the a side, D flip-flop 2 operates exactly the same as 1, and the Q output is equal to that of D flip-flop 1. When the switch 5 is on the b side, the D flip-flop 2 simply divides the clock input, and its Q output is not necessarily the same as the Q output of the D flip-flop 1. 3 is a phase comparator using an exclusive OR gate, 4 is an integrating circuit, and 6 is a comparator.

The a side and the b side of the switch 6 are controlled by the output of the comparator 6, so that when the L level is on the b side, and when the H level is on the a side.

Now, if the outputs of D flip-flops 1 and 2 are in the same phase, the output of exclusive OR gate 3 is low l/bell,
Comparator 6 output cover low. Therefore, the switch 6 is fixed to the b side. When the outputs of the D flip-flops 1 and 2 are opposite in phase, the output of the exclusive OR gate 3 is at a high level, the output of the comparator 6 is at a high level, and the switch 6 is therefore fixed to the a side. From the above, 1. In a steady state where a video signal in which the second frames are consecutive without any problem is input, the switch 6 is fixed to the b side.

Now, let us consider a case where noise is introduced at a certain point (a) in the video signal. In Fig. 3, noise enters point a, and HD
Suppose that the pulse is disturbed and the pulse is missing. At this time, the switch 6 with the two D flip-flops in Figure 2 is on the b side, and it is only a branch of the V pulse, so the output is
This is B in the diagram.

Therefore, the output of the phase comparator 3 becomes D in FIG.

Now, in Fig. 2, the integration time constant of the integrator circuit 4 and the comparator threshold hold of the comparator 6 are such that the output of the comparator 6 becomes H only after 4 consecutive hours of H (60m5eC in NTSC) or more. Configure it like this. At this time, the output of the integrating circuit 4 becomes as shown in D in FIG. 3, and therefore, the output of the comparator 1/-6 remains at L, so that the switch 6 maintains the b side. Therefore, the Q output of the D flip-flop 2, that is, the reference signal output, is not affected by noise and is basically the same as the first. It is possible to continue sending the signal B in FIG. 3 while maintaining the relationship in the second field.

Next, the first. If the continuity of the second field changes midway, that is, if the output or franging of D flip-flop 2 becomes different, then D flip-flop 1
, 2 are shifted by 180, so the output of the exclusive OR gate 3 is HKf. When the H state is reached (1- for 4 fields or more), the output of the integrating circuit 6 becomes L, and the emparator 6 holds the output (Fig. 3E).
Va ) is exceeded, so comparator 6 is inverted and H
become. Therefore, switch 5 switches B to A, and D flip-flop 2 becomes the same circuit as switch 1.

Then, the Q output of D flip-flop 2 is inverted, and D
It has the same phase as the Q output of the flip-flop 1 and changes to the output cover L of the exclusive OR gate 3. After about 4 field times, the output of the comparator 6 becomes L, the switch 6 switches to the b side, and the D flip-flop 2
The Q output of continues to be held in that state, that is, in the newly fringed state.

As described above, according to this embodiment, the first . In addition to faithfully creating a reference signal that detects the second field, it also eliminates noise and tape dropouts.
Also, by ignoring disturbances in the reference signal due to lack of H sync due to bouncing that occurs when switching input signals, framing servo I! is not affected by noise, etc. Noh is realized.

In addition, in the above embodiment, a method using a flip-flop as shown in FIG. 3A [as shown in FIG. However, the present invention is not limited to this embodiment, and any combination of a divisional unit, an integration (noise removal) circuit, and a switch may be used as long as it has the above function.

FIG. 4 shows a specific circuit example.

14 is an integration circuit, 16 is a comparator, and 15 is a switch. It is determined by the comparator 16. There are 15 switches, corresponding to switch 5 in Figure 2. When the output of comparator 16 is high level, ■1 turns on and D flip-flops 11 and 12 become the same circuit, and when it is low level, ■2 turns on. Thus, the D flip-flop 12 becomes a mere flip-flop.

Effects of the Invention As is clear from the above explanation, the framing servo device of the magnetic recording and reproducing device of the present invention includes a circuit that separates the horizontal synchronization signal and vertical synchronization signal of the video signal, and the separated vertical synchronization signal. A reference signal (30H in NTSC, PAL
The first step is to create a SECAM function (261). The first means is provided with a switching electronic switch that can simply convert the vertically identical signal into a frequency divider that divides the frequency by %, and the switch is on the side of a simple divider. has a circuit that compares the phase of the output of the first means with the output of the second means and integrates the comparison output, and collects the output of the first means that operates the switch with the integrated output as a reference signal. Therefore, the first means, that is, the reference signal output from the Q output of the D flip-flop 12 in FIG. 4 completely detects the first and second fields of the video signal. It has the excellent effect of producing a continuous framing reference signal that corrects the effects of input signal noise, dropouts, lack of horizontal synchronization signal, and disturbances caused by bouncing, etc., that occur when switching signals. It will be done.

Furthermore, due to this effect, the image quality may deteriorate after dubbing or editing many times, or if the tape is damaged, there may be noise or omissions in the synchronization signal part. This has the effect of solving the major problems of the prior art, such as the framing being disturbed due to signal disturbance, and therefore the recording servo being disturbed.

[Brief explanation of the drawing]

Figure 1 is a timing chart showing framing, Figure 2 is a timing chart showing framing.
FIG. 3 is a block diagram of a magnetic recording/reproducing apparatus according to an embodiment of the present invention, FIG. 3 is a timing chart showing the operation of the embodiment, and FIG. 4 is a specific circuit diagram of the embodiment. 1.2,11. 12...D flip-flop, 3.13...Exclusive OR gate, 4
゜14...Integrator circuit, 5.15...Switch, 6゜16...Comparator.

Claims (1)

[Claims] A circuit that separates a horizontal synchronization signal and a vertical synchronization signal of the video signal, respectively, and a first field and a second field of the video signal by comparing the vertical synchronization signal separated by the separating circuit with the horizontal synchronization signal. The first step is to generate a detected reference signal. said first means;
The means is provided with a changeover switch capable of converting the vertical synchronization signal into a frequency divider, and the output when the changeover switch is on the frequency divider side and the output of the second means. It has a circuit that compares the phase of and integrates the comparison output.
A magnetic recording/reproducing apparatus characterized in that the output of the first means for operating the switch using the integrated output is taken out as a reference signal.