JPH0463452B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field of the Invention] The present invention relates to an automatic magnetic tape speed switching device, and more particularly to an automatic magnetic tape speed switching device that detects a control pulse indicating the position of a recording track and automatically switches the magnetic tape speed during playback. . [Technical Background of the Invention] In a magnetic recording/reproducing apparatus, a control pulse _CTL is recorded on a control track 2 of a magnetic tape 1 shown in FIG. 1 to indicate the position of a recording track. The speed during recording varies depending on the recording mode. Below, for explanation, β mode (2.00cm/sec,
1st mode) and β mode (1.33cm/
It is assumed that data is recorded at two different speeds: second mode and second mode. The control pulse _CTL is reproduced by the control head 3 and sent to the first mode cycle determining circuit 5 and the second mode cycle determining circuit 6. The first mode period determination circuit 5 uses a comparison signal f ₁ (frequency is 27Hz)
If the signal is lower than that, an L level signal is output, and in other cases, an H level signal is output. The second mode period discrimination circuit 6 compares the frequency with the comparison signal f ₂ (frequency is 37 Hz), and outputs an L level signal if the frequency is higher, and an H level signal in other cases. The respective signals are outputted to pins 7a and 7b of the RS flip-flop 7, and a mode switching signal is outputted to the mode switching device 8 from the pin 7c.
On the other hand, from the capstan flywheel 9 to the head 1
The circuit signal F _G taken out at 0 is frequency-divided by the frequency division ratio determined by the first mode frequency divider 11 and the second mode frequency divider 12, and becomes a constant frequency. The rotation signal F _G converted to this constant frequency is sent to the capstan.
The output signal is fed back to the capstan motor 14 as an input signal to the AFC 13. Therefore, the running speed of the magnetic tape 1 in the first mode is
2.00cm/sec, maintained at 1.33cm/sec in the second mode. [Problems with Background Art] The playback modes include trick playback, ie, slow playback, in which the running speed of the magnetic tape 1 does not correspond to the first mode or second mode during recording. The running speed of the magnetic tape 2 during this trick playback is
The recording mode cannot be identified unless it is near 2.00cm/sec or 1.33cm/sec. Therefore, when entering trick regeneration, the trick regeneration signal is input to pin 7a of RS flip-flop 7 via pin 16 and diode 15, so that the state of RS flip-flop 7 does not change. Therefore, it is not possible to control various circuits according to the recording mode, such as setting the voltage applied to the capstan motor during intermittent slowing, switching video signal characteristics, etc. Also, if recording is in a different recording mode, press the mode switch 8.
Since the operation is locked by the trick reproduction signal and cannot be changed, abnormal operation may occur. Furthermore, at the start of recording mode judgment, the capstan
Since the running speed of the magnetic tape 1 cannot be determined until the AFC control is initiated by the AFC 13, the lighting and extinguishing of the recording mode indicator lamp etc. may become unstable and malfunction may occur. [Object of the Invention] The object of the present invention is to detect the angular velocities of the supply reel stand and the take-up reel stand at the time when the control pulses recorded on the magnetic tape are reproduced, and to calculate the interval between the control pulses on the magnetic tape from the angular velocities. An object of the present invention is to provide an automatic magnetic tape speed switching device that can always automatically switch speeds corresponding to recording modes by calculating the magnetic tape distance. [Summary of the Invention] The present invention is configured to determine the recording mode immediately upon reproducing control pulses recorded on a magnetic tape, and to switch the magnetic tape speed in accordance with the determined recording mode. At the first point in time when the control pulse is regenerated, the angular velocity of the supply reel base is detected from the first pulse train generated by the rotation of the supply reel base, and in the same manner, the angular velocity of the take-up reel base is detected from the second pulse train. It is designed to detect angular velocity. When the two angular velocities are known, the supply side reel stand (and take-up side reel stand) at the first point in time
The length of the winding tape can be calculated.
Therefore, the second control pulse that reproduces the next control pulse is
By calculating the length of the wound tape at the time point, the distance of the magnetic tape between the two control pulses can be obtained. Since the distance of this magnetic tape is constant in all parts unless the recording mode changes, the recording mode is determined by comparing it with fixed data stored in advance in the storage device. [Embodiment of the Invention] Hereinafter, an embodiment of the automatic magnetic tape speed switching device according to the present invention will be described in detail with reference to the drawings. Components that are the same in FIG. 2 and FIG. 1 are designated by the same reference numerals, so their explanation will be omitted. In FIG. 2, 17 is a cassette, and a supply reel 17a and a take-up reel 17b are placed on a supply reel stand 18 and a take-up reel stand 19, respectively. Supply side reel stand 18 and take-up side reel stand 19
The rotation is applied to a first angular velocity detector 24 and a second angular velocity detector 25 via reel pulse sensors 20, 21 and amplifiers 22, 23 as a train of first pulses _P1 and second pulses _P2, respectively. The control pulse sending circuit 26 receives the control pulse _CTL recorded on the magnetic tape 1 via the control head 3. This control pulse _CTL is shaped and supplied as a timing pulse to the first angular velocity detector 24, the second angular velocity detector 25, and the winding tape length calculation circuit 28. The first angular velocity detector 24 is a control pulse
Measure the pulse interval of the first pulse _P1 train at the time when _CTL is received. The reciprocal of the measured value is output to the winding tape length calculation circuit 27 as the first angular velocity ω ₁ . When the second angular velocity detector 24 receives the control pulse _CTL , it similarly obtains a second angular velocity ω ₂ from the train of second pulses P ₂ and outputs it to the winding tape length calculation circuit 27 . The winding tape length calculation circuit 27 receives the control pulse _CTL as a timing pulse.
Each time, the length of the tape wound on the supply reel 17a is calculated from the first angular velocity ω ₁ and the second angular velocity ω ₂ , and the calculated values are sequentially output to the magnetic tape distance calculation circuit 28 . The magnetic tape distance calculation circuit 28 is connected to the supply reel 17, which is sequentially input in accordance with the control pulse _CTL .
The distance of the magnetic tape narrowed by two control pulses _CTL is calculated from the numerical value of the length of the wound tape in a. The calculated magnetic tape distances are sequentially output to the comparator 29. The ROM 30 contains magnetic tape 1 related to the first mode (2.00 cm/sec) and the second mode (1.33 cm/sec).
data is recorded. Comparator 29 is ROM
The data set for 30 recording modes and the magnetic tape distance are compared. The mode switch 8 is controlled according to the comparison. In the figure, reference numeral 9a is a capstan, and 9b is a pinch roller. Next, the operation of the circuit will be explained. When the control pulse C _TL is sequentially reproduced at points t ₁ and t ₂ in FIG. 3A, the control pulse output circuit 26 outputs the shaped control pulse C _TL at point b as shown in FIG. 3B. Ru. t ₁
At the point, the first pulse at point C shown in Figure 3 C and D
Among the second pulses P ₂ at points P ₁ and d, the interval between the first two pulses (indicated by diagonal lines) is measured, and the first angular velocity ω ₁ and second angular velocity ω ₂ calculated as the reciprocals of this are the first angular velocity. It is output from the detector 24 and the second angular velocity detector 25. This measurement and calculation is
t ₂ points... are performed sequentially in response to the control pulse _CTL . When the magnetic tape 1 is in the direction shown by the arrow, the interval between the pulses changes from large to small on the supply reel 17a, and from small to large on the take-up reel 17b, and when the lengths of the respective winding tapes are equal, the measured pulses are separated from each other. The spacing between will be equal. When the first angular velocity ω ₁ and the second angular velocity ω ₂ are known, the tape velocity V _t shown in equation (13) in the table can be calculated. Also, the value of (13)
By substituting into equation (9), the length _L1 of the winding tape of the supply reel 17a can be obtained. The length L ₁ of the winding tape calculated by the winding tape length calculating circuit 27 and obtained by equation (9) in the table is sequentially outputted to the magnetic tape distance calculating circuit 28 . The magnetic tape distance arithmetic circuit 28 subtracts the next input value from the previously input value of the length _L1 of the winding tape to obtain the magnetic tape distance between the two control pulses _CTL . 29 in sequence. The comparator 29 compares a plurality of fixed data related to the recording mode of the ROM 30 with the input magnetic tape distance, and if they match, control corresponding to the determined recording mode is performed via the mode switch 8. The fixed data in ROM30 has a slight judgment width, so there is no judgment error due to measurement error or calculation error.

【table】

〔Effect of the invention〕

The automatic magnetic tape speed switching device according to the present invention includes two angular velocity detection means for detecting the angular velocity of the supply reel stand and the angular velocity of the take-up reel stand, and calculates the length of the tape to be wound on the supply reel from the two angular velocities. A first calculation means, a second calculation means for calculating a magnetic tape distance narrowed to two control pulses from a length of the wound tape, and a storage means for storing fixed data for each recording mode. Because of this configuration, it has the advantage that the magnetic tape distance narrowed to two control pulses can be calculated regardless of the running speed of the magnetic tape and whether it rotates forward or reverse. Therefore, even if the recording mode changes due to trick reproduction or the like, normal operation can be immediately continued. In addition, even in a transient state before being drawn into AFC control at the start of operation, the recording mode is immediately identified and the magnetic tape speed is switched, so there is no possibility of display lamps blinking due to malfunction.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a conventional magnetic tape speed switching device, FIG. 2 is a block diagram showing an embodiment of the magnetic tape speed switching device of the present invention, and FIGS. 3A to 3D are time charts of FIG. be. In the figure, 1 is a magnetic tape, 9 is a capstan flywheel, 9a is a capstan, 9b is a pinch roller, 17 is a cassette, 17a is a supply reel, 17b is a take-up reel, 18 is a supply side reel stand, 19 is Take-up side reel stand, 20 and 21 are reel pulse sensors, 24 is a first angular velocity detector, 25 is a second angular velocity detector, 26 is a control pulse sending circuit, 27 is a winding tape length calculation circuit, 2
8 is a magnetic tape distance calculation circuit, 29 is a comparator, 3
0 is ROM.

Claims (1)

[Claims] 1. The first pulse train and the second
a magnetic tape speed automatic switching device that generates a pulse train, a first angular velocity detection device that detects the angular velocity of the supply reel stand from the interval between pulses of the first pulse train at a first point in time when the control pulse is reproduced; means, second angular velocity detection means for detecting the angular velocity of the take-up reel stand from the interval between pulses of the second pulse train;
and a first calculation means for calculating the length of the first winding tape of the supply reel at the first time point from the first and second angular velocities obtained by the second angular velocity detection means; The length of the first winding tape at the time point and the length of the second winding tape at the second time point when the next control pulse is reproduced are calculated to determine the length between the first time point and the second time point. comprising a second calculation means for obtaining the distance of the magnetic tape, and a storage means for storing fixed data relating to the length of the magnetic tape narrowed by two control pulses recorded on the magnetic tape for each recording mode, The first time point and the second time point obtained by the second calculation means.
1. An automatic magnetic tape speed switching device, characterized in that the magnetic tape speed is changed according to a recording mode determined based on the magnetic tape distance between the points in time and the fixed data.