JPH0531998B2 - - Google Patents

Description

[Detailed Description of the Invention] (a) Industrial Application Field The present invention is a magnetic playback device (video tape recorder) that helically scans a magnetic tape using a pair of magnetic heads having different azimuth angles. The present invention relates to a pseudo vertical synchronization signal generator that generates a pseudo vertical synchronization signal during playback and still playback.

(b) Prior Art First, FIGS. 6 and 7 will be explained. 6th
The figure is a schematic diagram of still playback on a recording track, and FIG. 7 is a schematic diagram of 1/2 speed slow playback on a recording track. 1) is a track recorded by helically scanning a magnetic tape (not shown), and 2 is a track recorded by a magnetic head B (not shown) having the other azimuth angle helically scanning the magnetic tape. Tracks 3 and 4 are the vertical synchronizing signals recorded on tracks 1 and 2, respectively; 5, indicated by the two-dot chain line; 5, the center line of the scanning locus by the magnetic heads A and B; and 6, 7, indicated by the one-dot chain line, This is the center line of the scanning trajectory by magnetic heads A and B. Note that X is the distance required to sequentially record the tracks 1 and 2 in the width direction of the magnetic tape, and
4 is recorded, for example, at a position a=6.5H (1H is one horizontal scanning period) from the recording start position of tracks 1 and 2, that is, the switching positions m and n of magnetic heads A and B, respectively.

Here, when still playback is executed from the normal playback state as shown in FIG. Distance from n to reproducing vertical synchronization signal 4 b ₁
When the magnetic head A scans the trajectory having the center line 5, the vertical synchronization signal 3 is output from the switching position n.
There will be a difference of about 1.5H between the distance b ₂ and the distance it takes to reproduce.

In addition, as shown in Figure 7, it is 1/2 from the normal playback state.
When performing double-speed slow playback, the switching positions of magnetic head A are m, n, and the switching positions of magnetic head B are p, q. When magnetic head A scans a trajectory having center line 6, switching positions m, Distances c ₁ and c ₄ from n to reproducing vertical synchronizing signal 3, and distance from switching positions p and q to reproducing vertical synchronizing signal 4 when magnetic head B scans a trajectory having center line 7 Comparing c ₂ and c ₃ , there is a relationship of c ₂ < c ₁ < c ₃ < c ₄ , resulting in a difference of approximately 0.75H, which is 1/2 of the still reproduction time.

In other words, the playback position of the vertical synchronization signal during still playback and 1/2 speed slow playback is at each magnetic head A,
B and the switching position.

There is no problem if only the above is used, but magnetic heads A and B
have different azimuth angles, so during still playback and 1/2 speed slow playback, magnetic heads A,
Even if tracks 1 and 2 are scanned in B, it is not possible to obtain the same envelope as during normal playback, and in particular, the reproduced vertical synchronization signal is canceled by the noise caused by the decrease in the envelope, and the images cannot be synchronized. There was a problem that the image became distorted when it disappeared.

In order to solve this problem, still playback and 1/
It is sufficient to insert a pseudo vertical synchronization signal just before the vertical synchronization signal played during double-speed slow playback. An example of this technology is FISHER's video model.
FVH-840 “SFRVICE MANUAL Vol.4” No.
Fig. 2-3-22 etc. on page 60 are presented.

Fig. 4 is a circuit diagram showing an example of this technology, Fig. 5 is a timing chart showing waveforms of various parts in Fig. 4, and 8 is an input terminal to which switching signals of a pair of magnetic heads (not shown) are input. , 9 and 10 are monomultis that are triggered by the rising and falling edges of the switching signals, 11 is a monomultiplier that is triggered by the output of either one of the monomultis 9 and 10, and 12 is a monomultiplier to which a power supply voltage is applied. 13 is a power supply line; 14 and 15 are resistors and capacitors connected in series between the power supply line 13 and the ground to form a time constant circuit;
One end of the resistor 14 is connected to the monomulti 9, 16 is a two-contact switch that is connected to the power line 13 and is operated by a mode switching signal from the system control, and 17 and 18 are e-contacts of the switch 16, respectively. and a variable resistor whose one end is connected to the f contact, 19 is the variable resistor 17,1
8 and the ground, the other ends of the variable resistors 17 and 18 are connected to the monomulti 10, and the switch 16
When the switch 16 is switched to the E contact, a time constant circuit is formed by the variable resistor 17 and the capacitor 19, and when the switch 16 is switched to the F contact, the variable resistor 18 and the capacitor 19 form a time constant circuit. , 21 is the power line 13
A variable resistor and a capacitor are connected in series between the variable resistor 20 and the ground, and constitute a time constant circuit, one end of the variable resistor 20 being connected to the monomulti 11, and 22 being a variable resistor and a capacitor that are connected in series to each other in response to a mode switching signal. A switching circuit 23 that divides the frequency of the switching signal by two during playback and outputs a high-level signal during still playback is connected in parallel to the monomulti 11,
a switch 24 operated by the output of the frequency divider 22;
25 is a mixer for mixing the pseudo vertical sync signal and the video signal; 26 is the output terminal of the mixer 25; be. Note that the generation positions of vertical synchronization signals in various television receivers do not necessarily match.
Variable resistors 17 and 1 are used for setting the generation timing of pseudo vertical synchronization signals for each television receiver.
8 and 20 are provided.

When performing 1/2 speed slow playback in FIG. 4, the mode switching signal from the system control causes the switch 16 to switch to the e contact and the switching circuit 22 to divide the switching signal by two. Further, a power supply voltage is applied to the power supply terminal 12, and the switching signal shown in FIG.
The frequency is divided into two as shown in Figure B.

First, when the switching signal rises and the 2-frequency divided signal is at a high level (hereinafter referred to as "H"), the pulse shown in FIG. Output. The pulse is sent to the pseudo synchronization generating circuit 2 via the switch 23, which is closed by the "H" divided-by-2 signal.
4, and the pulse shown in FIG. 5, which is delayed by time _t1 from the rising edge of the switching signal, is output from the pseudo synchronization generating circuit 24.

When the switching signal falls and the frequency-divided signal rises, the monomulti 10 outputs the pulse shown in FIG. The pulse is “H” 2
The pulse shown in FIG. 5 is inputted to the pseudo synchronization generation circuit 24 via the switch 23 which is closed by the frequency divided signal, and is output from the pseudo synchronization generation circuit ₂₄ , as shown in FIG. be done.

When the switching signal rises and the frequency-divided signal is at a low level (hereinafter referred to as "L"), the resistor 14
The pulse shown in FIG. 5C is output from the monomulti 9 according to the time constant determined by the capacitor 15. Here, since the switch 23 is opened by the "L" divided-by-2 signal, the mono multi 11 is triggered by the mono multi 9 output, and the time constant determined by the variable resistor 20 and the capacitor 21 Therefore, the monomulti 11 outputs the pulse shown in FIG. 5E. The pulse is then input to the pseudo synchronization generating circuit 24, and the pulse shown in FIG. 5, which is delayed by time _t3 from the rising edge of the switching signal, is output.

When the switching signal and the divided-by-2 signal fall,
The pulse shown in FIG. 5D is output from the monomulti 10 according to a time constant determined by the variable resistor 17 and the capacitor 19. Here, switch 23 is "L" 2
Mono multi 1
1 is triggered by the output of the monomulti 10, and the pulse shown in FIG. The pulse is then input to the pseudo synchronization generating circuit 24, and the pulse shown in FIG. 5, which is delayed by time _t4 from the rising edge of the switching signal, is output.

The delay times t ₁ , t ₂ , t ₃ , repeatedly obtained from the above
The pulse at t ₄ is in a relationship corresponding to the vertical synchronization signal reproduced at distances c ₁ , c ₂ , c ₃ , and c ₄ shown in FIG. That is, the pulses having delay times t ₁ , t ₂ , t ₃ , and t ₄ are mixed with the video signal by the mixer 25 and inserted as a pseudo vertical synchronization signal immediately before the vertical synchronization signal to be reproduced. 1/ from this
Image distortion during double speed slow playback is prevented.

When performing still playback in FIG. 4, the mode switching signal from the system controller causes the switch 16 to be switched to the f contact and the switching circuit 22 to output a signal at a constant level of "H". Further, a power supply voltage is applied to the power supply terminal 12, and the switch 23 is always closed by the "H" signal output from the switching circuit 22.

First, when the switching signal rises, the monomulti 9 outputs the pulse shown in FIG. The pulse is inputted to the pseudo-synchronization generation circuit 24 via the switch 23, and the pulse shown in _FIG .

When the switching signal falls, the monomulti 10 outputs a pulse shown by a dashed-dotted line in FIG. This pulse is input to the pseudo-synchronous generation circuit 24 via the switch ₂₃ , and the pulse shown in the dashed line in _{FIG .} Output from 4.

As described above, the pulses with delay times t ₁ and t ₀ repeatedly obtained are in a relationship corresponding to the vertical synchronization signal reproduced at the distances b ₁ and b ₂ shown in FIG. In other words, the pulses having delay times t ₁ and t ₀ are mixed with the video signal by the mixer 25 and inserted as a pseudo vertical sync signal immediately before the vertical sync signal to be reproduced. Image distortion is prevented.

(c) Problems to be Solved by the Invention If we consider the relationship between the pulse delay times t ₁ , t ₂ , t ₃ , and t ₄ that occur during 1/2 speed slow playback, we can see that the resistance 14 and the capacitor 15 Since the time constant determined by is constant, the time t ₁ is a fixed value, and t ₂ = t ₁ + α t ₃ = t ₁ + β {where β is the pulse output time of the monomulti 11} t ₄ = t ₂ + β A relational expression is obtained.

Also, the delay time of the pulse that occurs during still playback.
Considering the relationship between t ₁ and t ₀ , the time t ₁ is a fixed value as in the case of 1/2 speed slow playback, and as explained using FIGS. 6 and 7, t ₀ − Since t ₁ =2(t ₂ −t ₁ ), the relational expression t ₀ =t ₁ +2α is obtained.

From this, by adjusting the variable resistors 17, 18, and 20, t ₂ ≧t ₁ , t ₂ <t ₁ t ₀ ≧t ₁ , t ₀ <t ₁ t ₃ >t ₁ t ₄ >t _2. It becomes possible to set the generation timing of the pseudo vertical synchronization signal.

As mentioned above, since the vertical synchronization signal generation positions in various television receivers do not necessarily match, it is necessary to use a variable resistor for television receivers that are used for 1/2 speed slow playback and still playback image monitoring for the first time. The generation timing of the pseudo vertical synchronization signal must be set again by adjusting the steps 17, 18, and 20. However, even if the variable resistor 20 is adjusted, the times t ₃ and t ₄ are each changed to the time t ₁
and t ₂ or less, there was a problem that it was difficult to set times t ₃ and t ₄ near times t ₁ and t ₂ , respectively. Furthermore, this time t ₃ and
The reason for setting t ₄ near t ₁ and t ₂ is that for some television receivers, t ₁ ≒ t ₃ and t ₂ ≒ t ₄ are the best points for synchronization stability. . Also,
During 1/2 speed slow playback and still playback, it is necessary to change the time constant of the monomulti 10 by changing the switch 16, resulting in a problem that the configuration becomes complicated.

(d) Means for Solving the Problems The present invention has been made to solve the above problems, and provides a magnetic reproducing apparatus that helically scans a magnetic tape with a pair of magnetic heads having different azimuth angles. a control means that receives a switching signal of a pair of magnetic heads or a waveform equivalent to the switching signal as an input signal and outputs a control signal corresponding to each mode of 1/2 speed slow playback and still playback; It has a first time constant circuit that sets the delay time of the pseudo vertical synchronization signal with respect to the falling edge, and the input signal input thereto is passed through or output as a single pulse or continuous pulse by the output of the control means. a first signal processing means; and an adjustable second time constant circuit for setting the delay time; It has a second signal processing means that outputs one pulse or a continuous pulse, and an adjustable third time constant circuit that sets the delay time,
The output of the control means causes the second
The third signal processing means passes through the output of the signal processing means or outputs it as a single pulse, and the pseudo synchronization generating means generates the pseudo vertical synchronization signal from the output of the third signal processing means.

(e) Effect: According to the pseudo vertical synchronization signal generating device of the present invention, the second and third functions adjust the delay time of the pseudo vertical synchronization signal with respect to the rising or falling edge of the input signal according to each television receiver. The adjustment range of the time constant circuit is expanded, and switching and adjustment of the second and third time constant circuits becomes unnecessary no matter which mode, 1/2 speed slow playback or still playback, is selected.

(f) Examples The details of the present invention will be specifically explained by referring to illustrated examples.

Fig. 1 is a circuit diagram showing the present invention, Fig. 2 is a timing chart showing waveforms of various parts during 1/2 speed slow playback in Fig. 1, and Fig. 3 shows waveforms of various parts during still playback in Fig. 1. This is a timing chart.

To explain the figure number and structure of Figure 1, 2
7 is a power supply terminal to which a power supply voltage is applied; 28 is a power line; 29 is an input terminal to which a switching signal for a pair of magnetic heads is input; 30 is a mode switching signal from the system control and the switching signal is input; 31 is the mode switching signal, switching signal and switching circuit 3 which divides the frequency of the switching signal into 2 during double speed slow playback and outputs an "H" signal during still playback;
A control signal generation circuit to which a 0 output is input,
The switching circuit 30 and the control signal generating circuit 31 constitute a control means, 32 is a monomulti connected to the input terminal 29, and 33 is a monomulti 3 connected to the input terminal 29.
Switches 34 and 35 connected in parallel to 2 and operated by the output of the control signal generation circuit 31 are resistors and capacitors connected in series between the power supply line 28 and the ground and forming a first time constant circuit. , one end of the resistor 34 is connected to the monomulti 32 and the control signal generating circuit 31, and 36 is a switch connected between one end of the resistor 34 and the ground and operated by the output of the control signal generating circuit 31. , the monomulti 32, the switch 33,3
6, a resistor 34 and a capacitor 35 constitute a first signal processing means, 37 is a mono multi connected to the mono multi 32, 48 is connected in parallel to the mono multi 37, and the control signal generating circuit 31 Switches 38 and 39 operated by the output are connected in series between the power supply line 28 and the ground, and are variable resistors and capacitors constituting a second time constant circuit, one end of the variable resistor 38 being connected to the monomultiple 37 and the control signal generation circuit 31, and 40 is a switch connected between one end of the variable resistor 38 and the ground, and operated by the output of the control signal generation circuit 31, and is connected to the monomulti 37, the resistor 38, Capacitor 39 and switch 4
0 and 48 constitute a second signal processing means, 41 is a mono multi connected to the mono multi 37, and 42 is a switch connected in parallel to the mono multi 41 and operated by the output of the switching circuit 30. , 43 and 44 are a variable resistor and a capacitor that are connected in series between the power supply line 28 and the ground and constitute a third time constant circuit, one end of the variable resistor 43 is connected to the monomulti 41, and the A third signal processing means is constituted by a monomulti 41, a switch 42, a resistor 43, and a capacitor 44, and 45 is connected to the monomulti 41 and serves as a pseudo synchronization generating means for generating a pseudo vertical synchronization signal. A generating circuit 46 is connected to the pseudo synchronization generating circuit 45, and a mixer 47 is an output terminal of the mixer 46 for mixing the pseudo vertical synchronization signal and the video signal. Note that the generation positions of the vertical synchronization signals in various television receivers do not necessarily coincide, and variable resistors 38 and 43 are provided for setting the generation timing of the pseudo vertical synchronization signal for each television receiver.

When performing 1/2 speed slow playback in FIG. 1, the power supply voltage is applied to the power supply terminal 27, and the switching signal shown in FIG. The frequency is divided into two as follows.

When the switching signal rises and the frequency-divided signal is "H", the output of the control generation signal circuit 31 opens and closes the switches 33 and 48, respectively, and the "H" frequency-divided signal closes the switch 42. First, the pulse shown in FIG. However, just before the pulse reaches the threshold level _S1 , the output of the control signal generation circuit 31 triggers the switch 3.
6 is instantaneously closed, the monomulti 32 outputs a pulse at a threshold level _S1 following the above pulse, as shown in FIG. 2C. The continuous pulses are then inputted to the pseudo synchronization generating circuit 45 via the switches 48 and 42, and the pulses shown in FIG. 2 are outputted with a delay of time _t1 from the rising edge of the switching signal.

When the switching signal falls and the frequency-divided signal rises, the switches 33 and 48 are opened by the output of the control signal generation circuit 31, and the switch 42 is closed by the "H" frequency-divided signal.
According to the time constant determined by the capacitor 35, the monomulti 32 outputs the pulse shown in FIG. The monomulti 37 is triggered by the output of the monomulti 32, and the pulse shown in FIG.
The pulse is input to the pseudo synchronization generating circuit 45 via the switch 42, and the pulse shown in FIG. 2 is output delayed by a time _T2 from the falling edge of the switching signal.

When the switching signal rises and the frequency-divided signal is "L", the switches 33 and 48 are opened and closed by the output of the control signal generation circuit 31, and the switch 42 is opened by the frequency-divided signal of "L". , First, the pulse shown in FIG. Mono multi 41 will be triggered by mono multi 32 output,
The pulse shown in FIG. 2E is output from the monomulti 41 according to a time constant determined by the variable resistor 43 and the capacitor 44. The pulse is then input to the pseudo synchronization generating circuit 45, and the pulse shown in FIG. 2, which is delayed by time _T3 from the rising edge of the switching signal, is output.

When the switching signal and the divided-by-2 signal fall,
The output of the control signal generation circuit 31 causes the switch 33,
48 are respectively closed and opened, and the 2 of "L"
The switch 42 is opened by the frequency-divided signal, and the pulse shown in FIG. Monomulti 41 is monomulti 3
7 output, and the monomulti 41 outputs the pulse shown in FIG. The pulse is generated by the pseudo synchronous generation circuit 4.
5, and the pulse shown in FIG. ₂ delayed by time T4 from the falling edge of the switching signal is output.

The delay times T ₁ , T 2 , T ₂ ,
The pulses at T ₃ and T ₄ are located at distances c ₁ , c ₂ , c ₃ , and
This relationship corresponds to the vertical synchronization signal reproduced at position _c4 . That is, the pulses having delay times T ₁ , T ₂ , T ₃ , and T ₄ are mixed with the video signal by the mixer 46 and inserted as a pseudo vertical synchronization signal immediately before the vertical synchronization signal to be reproduced. This prevents image distortion during 1/2 speed slow playback.

When performing still playback in FIG. 1, a power supply voltage is applied to the power supply terminal ₂₇ , and the switching circuit 30
An "H" signal is output from the switch 42, and the switch 42 is always closed.

When the switching signal shown in FIG. 3A, which is the same as that in FIG. Depending on the constant, the monomulti 32 outputs the pulse shown in FIG. 3B. However, just before the pulse reaches the threshold level _S1 , the switch 36 is instantaneously closed by the output of the control signal generation circuit 31. A continuous pulse of threshold level _S1 is output. The continuous pulses are then inputted to the pseudo synchronization generating circuit 45 via the switches 48 and 42, and the pulses shown in FIG. 3D are outputted with a delay of time _T1 from the rising edge of the switching signal.

When the switching signal falls, the switches 33 and 48 are closed and opened, respectively, by the output of the control signal generation circuit 31, and the time constant determined by the variable resistor 38 and the capacitor 39 first changes the output from the monomulti 37 to FIG. 3C. The pulse shown is output. However, just before the pulse reaches the threshold level _S1 , the switch 40 is instantaneously closed by the output of the control signal generation circuit 31.
As shown in FIG. 3C, the monomulti 37 outputs a pulse at a threshold level _S2 following the above pulse. The continuous pulses are then input to the pseudo synchronization generating circuit 45 via the switch 42, and the third pulse is inputted to the pseudo synchronization generating circuit 45 via the switch 42, and the third pulse is delayed by the time _T0 from the falling edge of the switching signal.
The pulse shown in Figure D is output.

As described above, the pulses with delay times T ₁ and T ₀ repeatedly obtained are in a relationship corresponding to the vertical synchronization signal reproduced at the distances b ₁ and b ₂ shown in FIG. That is, the pulses with delay times T ₁ and T ₀ are sent to the mixer 46
The signal is mixed with the video signal and inserted as a pseudo vertical synchronization signal immediately before the reproduced vertical synchronization signal, thereby preventing image distortion during still reproduction. Note that a waveform equivalent to the switching signal may be used instead of the switching signal.

Here, the single pulse generation time of the monomulti 32,
That is, the fixed value is _T5 , and the pulse delay times _T0 , _T1 , which occur during 1/2 speed slow playback and still playback are
Considering the relationship between T ₂ , T ₃ , and T ₄ , in the case of 1/2x slow playback, T1 = 2 x T5 T2 = T5 + T6 = T1 + (T6 - T5) T3 = T5 + T7 = T1 + (T7 - T5 ) T4=T6+T7=T2+(T7-T5) Therefore, by adjusting the variable resistors 38 and 43, T2<T1, T3<T1, T4<T2, which could not be adjusted by the conventional circuit, can be adjusted by T5. The relationship is also possible, and in the case of still playback, T0 = 2 x T6 = T1 + 2
(T6 - T5), so it is possible to set the pseudo vertical synchronization signal generation timing without changing the monomulti constant.

(G) Effects of the Invention According to the pseudo vertical synchronization signal generating device of the present invention, the time constant circuit that adjusts the delay time of the pseudo vertical synchronization signal with respect to the rising or falling edge of the input signal according to each television receiver. The adjustment range has been expanded, and there is no need to switch or adjust the time constant circuit no matter which mode, 1/2 speed slow playback or still playback, is selected, making it easier for the user to make adjustments. It will be done.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the present invention, Fig. 2 is a timing chart showing waveforms of various parts during 1/2 speed slow playback in Fig. 1, and Fig. 3 shows waveforms of various parts during still playback in Fig. 1. Timing chart, Fig. 4 is a conventional circuit diagram, Fig. 5 is a timing chart showing waveforms of each part of Fig. 4, Fig. 6
The figure is a schematic diagram of still playback on a recording track, and FIG. 7 is a schematic diagram of 1/2 speed slow reproduction of a recording track. 30...Switching circuit, 31...Control signal generation circuit, 32, 37, 41...Mono multi, 33, 3
6,40,42,48...Switch, 34...Resistor, 35,39,44...Capacitor, 38,4
3...Variable resistor, 45...Pseudo synchronous generation circuit.

Claims (1)

[Claims] 1. In a magnetic playback device that helically scans a magnetic tape using a pair of magnetic heads with different azimuth angles, switching signals of the pair of magnetic heads or a waveform equivalent to the switching signals are used as input signals, and 1/2 speed slow playback and It has a control means for outputting a control signal according to each mode of still playback, and a first time constant circuit for setting a delay time of a pseudo vertical synchronization signal with respect to the rising and falling edges of the input signal, and the control means outputs has a first signal processing means that passes the input signal input thereto or outputs it as a single pulse or a continuous pulse, and an adjustable second time constant circuit that sets the delay time, a second signal processing means for passing through or outputting the first signal processing means output input thereto as a single pulse or a continuous pulse according to the control means output; and an adjustable second signal processing means for setting the delay time. a third signal processing means having a time constant circuit of 3, and passing through the output of the second signal processing means input thereto or outputting it as a single pulse according to the output of the control means; and the third signal processing means. A device for generating a pseudo vertical synchronization signal, comprising pseudo synchronization generating means for generating the pseudo vertical synchronization signal from an output of the means.