JPS6141055B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a magnetic tape drive control device for a magnetic tape having absolute addresses expressed in time.

VTR (video tape recorder), especially for editing
In the case of a VTR, the frame number and time, such as hours, minutes, and seconds, are displayed on the side edge of the magnetic tape or in the vertical blanking part of the slant track, corresponding to one frame of the video signal recorded on the slant track. It is well known that a magnetic tape is used on which an absolute address is recorded as a time code signal.

In such a VTR, a so-called pre-roll is performed in which the magnetic tape is quickly run to a target absolute address on the magnetic tape based on an absolute address signal reproduced from the magnetic tape. In this case, the magnetic tape is fast forwarded (hereinafter abbreviated as FF).
If you run it and stop it near the target absolute address,
The magnetic tape can be run to the target absolute address of the magnetic tape very quickly and stopped there. That is, for example, the rotational speed of the take-up reel motor or the supply reel motor as a means for driving the magnetic tape is set higher than the normal speed to drive the magnetic tape.
If you run FF and turn off the power to the motor a little before the target absolute address, the magnetic tape will continue to run a little after that, causing a so-called overrun. can stop the magnetic tape. However, the amount of overrun of the magnetic tape varies depending on its running speed. It is generally known that the amount of overrun is proportional to the square of the tape feeding speed. However, it cannot be denied that the proportionality constant varies somewhat depending on the tape position at that time.

Therefore, there is a method to gradually reduce the tape speed with some margin before the magnetic tape approaches the target absolute address, and then run it at a low constant speed near the target absolute address and then stop it. Calculation of how to control the tape speed to reduce the speed based on the speed of the tape is complicated, and if you try to do this calculation with a simple circuit,
This has the disadvantage that a lot of time is wasted, and the time required for pre-calls ends up being longer. Furthermore, if it is attempted to accurately control the tape speed, the arithmetic circuit for this purpose becomes extremely complex.

The present invention has a magnetic tape having a simple configuration, which controls the speed of the magnetic tape suitable for the overrun characteristics of the magnetic tape, and allows the magnetic tape on which a time code signal is recorded to quickly travel to a desired target position. This paper attempts to propose a drive control device.

A tape drive control device according to the present invention includes means for reproducing a time code signal representing the current tape position from a magnetic tape on which the time code signal is recorded, and a time code signal representing the reproduced time code signal and a target tape position. and a tape running speed means for detecting the running speed υ of the magnetic tape. υ ² = The present invention is characterized in that the drive of the magnetic tape is controlled in accordance with a tape speed-tape length curve that satisfies Kx (K is a constant).

An embodiment of the present invention will be described in detail below with reference to FIG. 1 is a supply reel, 2 is a take-up reel, 3 is a tape guide drum, 4 is a magnetic tape, 5
6 is a motor that drives the supply reel 1, and 6 is a motor that drives the take-up reel 2. As is well known, the tape guide drum 3 is composed of, for example, a lower fixed drum and an upper rotating drum, and is provided with one or more recording/reproducing rotating magnetic heads, erasing rotating magnetic heads, etc. On the magnetic tape 4, for example, as described above, on its side edge, there is a signal (time code signal) of an absolute address representing the frame number corresponding to each frame of the recorded video signal and the time corresponding to that frame, that is, hours, minutes, and seconds. is recorded.

7 is a tape running speed detection roller; 9 is a magnetic gear that rotates together with this roller 7; 10 and 11;
1 is a detection head, and these rollers 7, magnetic gear 9, and detection heads 10 and 11 constitute a tape running speed detection device 8. For example, AC motors are used as the motors 5 and 6, and a commercial AC power of, for example, 100V is supplied to the AC power input terminal 12, and this AC current is supplied to the motor 5 through triacs 13 and 14, which are semiconductor-controlled rectifiers, respectively.
and 6.

Detection pulses from the detection heads 10 and 11 of the tape running speed detection device 8 are supplied to the Schmitt trigger circuits 15 and 16 for waveform shaping, and the respective output pulses are directly supplied to exclusive OR circuits 19 and 20, as well as to the Schmitt trigger circuits. The outputs of 15 and 16 are connected to integration circuits 17 and 1, respectively.
8 through exclusive OR circuits 19 and 2
0. The outputs of these exclusive OR circuits 19 and 20 are supplied to an OR circuit 21, the output of which is supplied to a frequency discriminator 22, and a DC voltage corresponding to the tape speed is output. Then, this DC voltage is supplied to the positive phase amplifier 23 and amplified, and the output of this amplifier 23 is supplied to the negative phase amplifier 25, so that DC voltages having opposite phases to each other are obtained from these amplifiers 23 and 25, respectively. There is. 24 is a variable resistor for controlling the gain of the amplifier 23;
26 is a variable resistor for gain control of the amplifier 25. Each output of these amplifiers 23 and 25 is supplied to a switch circuit 27, and its two outputs are supplied to analog comparison circuits 29 and 30. Further, the AC voltage from the input terminal 12 is supplied to the sawtooth wave generation circuit 61 via the DC blocking coupling circuit (transformer) 60, from which a sawtooth wave signal having a frequency corresponding to the frequency of the AC voltage is obtained. These sawtooth wave signals are supplied to the above-mentioned analog comparison circuits 29 and 30, respectively, and are compared in level with the two outputs of the switch circuit 27. The outputs of these comparison circuits 29 and 30 are supplied to trigger pulse generation circuits 31 and 32, respectively, and the respective outputs are passed through DC blocking coupling circuits (transformers) 33 and 34 to triac 13, respectively.
and 14 as a control signal. Thus, in the triaxes 13 and 14, the flow angle of the alternating current supplied to the motor 5 or 6 is controlled based on the comparison outputs from the analog comparators 29 and 30.

Next, the configuration of the above-mentioned switch circuit 27 will be explained. The switch circuit 27 includes switches 27A and 27
B, which are switched in conjunction with each other. These switches 27A and 27B are connected to the comparator circuit 2, respectively.
A movable contact m connected to the input side of 9 and 30
It has a fixed contact ff for FF running, a fixed contact cs for low constant speed, and a fixed contact st for stopping. A fixed contact cs of the switch 27A is connected to the output side of the amplifier 23, and a fixed contact cs of the switch 27B is connected to the output side of the remover 25. Also, the fixed contact ff of switch 27A
and st are assumed to be free contacts. The fixed contact st of the switch 27B is also a floating contact, but the fixed contact ff is connected to the positive electrode of the variable DC power supply 28.

40 is a tape position detection circuit, to which a time code signal reproduced from the magnetic tape 4 is supplied from an input terminal 51. This tape position detection circuit 4
At 0, the tape position x ₁ is detected based on the absolute address signal reproduced from the magnetic tape 4 having the absolute address expressed in time. This x ₁ is a signal representing digitized time. In this case, the frame number is ignored. That is, this tape position x ₁ is a code signal indicating the hour, minute, and second according to the absolute address on the magnetic tape 4. 47 is a target tape position setting circuit (register). This target tape position setting circuit 47 sets a target tape position _x0 corresponding to the target absolute address of the magnetic tape 4. This target tape position _x0 also indicates an absolute address expressed in time on the magnetic tape 4, and is also a code signal expressed in hours, minutes, and seconds. 41 is a first unit for calculating the time corresponding to the tape length x from the target tape position x ₁ based on the absolute address signal reproduced from the magnetic tape 4 to the target tape position x ₀ corresponding to the target absolute address of the magnetic tape 4. It is an arithmetic circuit. This tape length x
is expressed in hours, minutes, and seconds, but in this case, if time is ignored, it is expressed in minutes and seconds. The output x of this first arithmetic circuit 41 is expressed as x=x ₀ -x ₁ . 42 is thus connected to the first arithmetic circuit 4
This is a data conversion circuit that converts 1 minute of the time x calculated in step 1 into ²⁶ seconds, and further converts 10 seconds into ²³ seconds in this example. Then, the output x of this first arithmetic circuit 41
is supplied to the data conversion circuit 42, and the converted time x' is output. Further, 54 is a tape speed detection circuit, to which an input terminal is supplied with, for example, a CTL signal or a time code signal recorded on a magnetic tape, and the period of the signal (proportional to the reciprocal of the tape speed) is digitized. Something is output. The tape speed detecting means 53 may be constituted by this tape speed detecting circuit 54 and a control head, a time code signal head, or the above-described tape running speed detecting device 8 and its associated circuits. A second calculation circuit 43 calculates the converted time x' and the tape speed detected by the tape speed detection means 53. For example, a digital signal corresponding to the cycle of the CTL signal is obtained from the tape speed detection circuit 54, and this is designated as T. And this second
The calculation circuit 43 calculates x' and T and outputs T ² x' as an output. and,
The output of this second arithmetic circuit 43 is supplied to a digital comparator 44. 45 is a first tape speed control range setting circuit. The setting circuit 45 outputs two reference values k ₃ and k ₄ , which are supplied to the digital comparator 44 and digitally compared in level with the output T ² x' of the second arithmetic circuit 43. . The comparison output is then supplied to the switch circuit 27 as a control signal.

Further, the output x of the first arithmetic circuit 41 is supplied to a digital comparator 48, where it is compared with the output a from the second tape speed control range setting circuit 50, and the comparison output is supplied to the switch circuit 27 as a control signal. be done. Further, the output x of the first arithmetic circuit 41 is supplied to a digital comparator 49, where it is compared with the output from the second tape speed control range setting circuit 50, and the comparison output is supplied to the switch circuit 27 as a control signal. Ru.

Next, the operation of the main parts of this magnetic tape drive control device will be explained. First, as shown in the flowchart of FIG. 2, the VTR is started, and then an FF drive command is issued. In this way, the movable contacts m of the switches 27A and 27B of the switch circuit 27 are respectively connected to the fixed contacts ff (the control circuit for this is not shown), so that the motor 6 on the take-up reel 2 side is Electric current is supplied to cause the motor 6 to rotate at high speed. In this case, the servo circuit based on the detection pulse from the tape running speed detector 8 does not operate. Then, in the tape position detection circuit 40, the absolute address when the magnetic tape 4 is running FF,
That is, the time is detected. Also, the tape speed detection circuit 5
4, the tape speed is detected as the period T of the CTL signal, which is its reciprocal. The first calculation circuit 41 performs the calculation x ₀ -x ₁ =x. Then, in the data conversion circuit 42, the time x is changed to the time x as described above.
It is converted to x′. Then, x' and T are computed in the second arithmetic circuit 43, and an output of T ² x' is obtained. And this output T ² x′ is the digital comparator 44
and is compared with reference values k ₃ and k ₄ from the first tape speed control range setting circuit 45. When T ² x' is larger than k ₄ , the movable contacts m of each switch 27A and 27B of the switch circuit 27 are still on _the fixed contact ff side, and when T ² Each switch 27
The movable contacts m of A and 27B are switched to the fixed contacts st, and the power supplied to the motor 6 is cut off. The high-speed rotation and rotation stop of the motor 6 are sequentially and alternately performed based on the comparison output of the digital comparator 44. In the above case, the magnetic tape 4 is caused to travel FF and stopped by controlling the rotation of the motor 6, but instead of being stopped, it may be caused to travel at a low constant speed.

Then, in the digital comparator 48, the tape length x
When becomes smaller than a (approximately 2 seconds based on the absolute address of the magnetic tape 4), the switch 27A,
The movable contact m of 27B is switched to the fixed contact cs, and the magnetic tape 4 is caused to run at a low constant speed. Furthermore, in the digital comparator 49, the tape length x
generates an output and switches the switch circuit _to Each movable contact m of each switch 27A, 27B of 27 is a fixed contact.
st, the power supply to the motor 6 is cut off, and then the magnetic tape 4 overruns and stops running at the target tape position _x0 based on the target absolute address. The operation is thus completed. In the above embodiment, the case of FF running of the magnetic tape 4 was described, but the same applies to the case of rewinding running.

Next, with reference to FIG. 3, the operating principle of the magnetic tape drive control device of the present invention will be further explained. As mentioned above, the amount of magnetic tape overrun is proportional to the square of the tape speed. Therefore, it is proportional to the reciprocal of the tape speed. The relationship between T and tape position x is T ² x=k ₁ . In this case, k ₁ varies somewhat depending on the tape position. Therefore, we set a value k _{2 that} is slightly larger than k ₁ , and when T ^{2 x} > k ₂ , the motor 6 is rotated at high speed, and when T 2 This operation is repeated until the length x approaches 0, and the magnetic tape 4 is run at a low constant speed just before x=0, and then the motor 6 is started to run at a low constant speed just before the target tape position, taking into account overrun. If the supplied drive current is cut off, the magnetic tape 4 will stop at the target tape position x0 where x= ₀ .

Next, the method of controlling the drive of this magnetic tape will be further explained with reference to FIG. here,
If the running speed of the tape 4 is υ (this is proportional to 1/T) and the running distance of the tape 4 until it stops running after stopping the supply of drive current to the motor 6 is x, then the running distance of the tape 4 is The relational expression between x and the running speed υ of the tape 4 is υ ² =K'x, as shown as a curve in FIG. Here, K' is a constant. Therefore, when the tape 4 is running at a running speed υ ₁ , the motor 6
When the supply of drive current to the tape 4 is cut off, the tape 4 travels by x ₁ and then stops, as is clear from FIG.
That is, when the difference between the current tape position and the target tape position is x ₁ and the current tape running speed is υ ₁ , when the supply of drive current to the motor 6 is cut off, the running speed of the tape 4 follows the curve. It becomes lower along the line and finally stops at the target tape position.

Here, considering the variation of the constant K', by setting the tape running speed to a value υ ₂ smaller than υ 1 when the difference between the current tape position and the target tape position _is x ₁ , the tape 4 Overrun can be avoided. Therefore, considering what kind of profile the running speed of the tape 4 is controlled from υ ₂ according to, the case where it is controlled along the curve in Fig. 5 according to the formula υ ² = Kx and the case where it is controlled according to the equation of υ 2 = Kx and , υ=Lx, and may be controlled along the straight line in FIG. 5. Note that K and L are constants. Comparing these, the curved line is more efficient. That is, a curved line has a higher average tape running speed than a straight line, and it takes less time to reach the target tape position.

The constant K may be any value less than or equal to the constant K', and K=K' is the case where the running control of the tape 4 is ideal, and in practice K<K'. Note that when K=K', the tape reaches the target position from the current position in the minimum time.

Therefore, the running of the tape 4 is controlled by repeatedly rotating the motor 6 at high speed and cutting off the drive current to the motor 6 so that the running speed of the tape 4 decreases along the curve. In reality, when the tape approaches the target position, the tape 4 is run at a low constant speed, and then the supply of drive current to the motor 6 is cut off.

In FIG. 3, the horizontal axis shows the tape speed in logarithm, and the vertical axis shows the conversion time x' corresponding to tape length x and the corresponding number of frames in logarithm. The dashed-dotted line indicates the straight line of T ² x=k ₁ . By the way, if x≒x', as shown in Figure 4, if the horizontal axis is the time x corresponding to the tape length and the vertical axis is the conversion time x' corresponding to the tape length, then the time corresponding to the tape length is The polygonal line W showing the relationship between x and the conversion time x' depending on the tape length has an error between +6.7% and -20% on both sides of 0%. Therefore, instead of K ₂ mentioned above, k ₃ and k ₄
As shown in FIG. 3, the motor 6 is made to rotate at high speed when T ² x′>k ₄ , and the power to the motor 6 is turned off when T ² x′<k ₃ , and k ₃ ≦T ² When x'≦k ₄ , by not issuing a switching control command to the switch circuit 27, the running of the magnetic tape 4 is controlled within the tape speed control range indicated by diagonal lines in FIG. It turns out.

Furthermore, if the control of the tape 4 in the shaded area in FIG. 3 is illustrated in accordance with FIG. 5, it will become as shown in FIG. 6. That is, the tape 4 is rotated at high speed by the motor 6 so that the running speed decreases between the curve according to the formula υ ² =K ₂ x and the curve according to the formula υ ² =K ₁ x. By repeatedly cutting off the drive current to the motor 6, its running is controlled. In addition, K ₁ and K ₂ are constants,
K′>K ₂ >K ₁ .

First, the motor 6 is rotated at high speed to cause the magnetic tape 4 to travel FF, and then the motor 6 is alternately rotated and stopped at high speed to adjust the tape speed υ (proportional to 1/T) and tape length. The relationship with conversion time x' is kept within the tape speed range indicated by diagonal lines. Tape position x ₁ is target tape position x ₀
When the position a (for example, 2 seconds) is reached, the motor 6 is rotated at a low constant speed to cause the magnetic tape 4 to run at a low constant speed, and an overrun is taken into account at b, for example, one to several frames before the target tape position _x0 . If the drive current to the motor 6 is then cut off, the magnetic tape 4 will stop at the target position.

In the present invention, in particular, the data conversion circuit 42 converts 1 minute of the tape length x indicated by time into 2 ⁶
In addition to converting 10 seconds to ²³ seconds in the case of the embodiment, the operation to obtain T ² x' in the second arithmetic circuit is only binary multiplication, and the configuration of the arithmetic circuit is It becomes easy. Further, since the time x depending on the tape length and the conversion time x' depending on the tape length have very small errors as shown in FIG. 4, there is no practical problem.

According to the above-described magnetic tape drive control device of the present invention, a magnetic tape having a simple configuration and an absolute address represented by time can be moved to a desired target tape position by speed control appropriate to its overrun characteristics. It can be made to run quickly. In particular, depending on the tape length, you can change the time from 1 minute to 2 to ⁶ seconds or as necessary.
When converting 10 seconds into ²³ seconds, the calculation circuit becomes extremely simple.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, FIG. 2 is a flowchart for explaining the operation of the present invention, and FIGS. FIG. 3 is a characteristic curve diagram for explaining the operation of the invention. 4 is a magnetic tape, 5 and 6 are motors as magnetic tape drive means, 27 is a switch circuit, 27
A and 27B are the respective switches, 40 is a tape position detection circuit, 41 is a first arithmetic circuit, 42 is a data conversion circuit, 43 is a second arithmetic circuit, 44 is a digital comparator, and 45 is a first tape speed 47 is a target tape position setting circuit; 48 and 49 are digital comparators; 50 is a second tape speed control range setting circuit; 53 is tape speed detection means;
54 is a tape speed detection circuit.

Claims (1)

[Claims] 1. Means for reproducing a time code signal representing a current tape position from a magnetic tape on which a time code signal is recorded; The tape length signal x corresponding to the tape length from the current tape position to the target tape position is
and a tape running speed detection means for detecting the running speed υ of the magnetic tape, and the magnetic tape is adjusted according to the tape speed-tape length curve that satisfies υ ² = Kx (K is a constant). A magnetic tape drive control device characterized by controlling the drive of a tape. 2 The above magnetic tape drive control is defined by two tape speed-tape length curves that satisfy υ ² = K ₁ x υ = K ₂ x (K ₁ and K ₂ are constants such that K ₁ < K ₂ ). 2. The magnetic tape drive control device according to claim 1, wherein the magnetic tape drive control device operates within a speed range in which the magnetic tape drive is performed.