JPH06339103A - Magnetic recording and reproducing device - Google Patents

Abstract

PURPOSE:To provide a magnetic recording and reproducing device in which a capstan motor is driven at a low speed so as to feed a magnetic tape by a predetermined frame. CONSTITUTION:The magnetic recording and reproducing device in which a capstan motor is driven at a low speed from a still picture state to feed by a predetermined frame is provided with a drive pulse generating means 7 generating a drive pulse based on, a low speed drive signal, an FG 12 fitted to the capstan motor, 1st and 2nd counter means 13,14 counting an output pulse of the frequency generator, a 1st comparator means 17 comparing the count data from the 1st count means 13 with 1st data equivalent to feed quantity required for driving a magnetic tape at a low speed, a drive pulse control means 9 controlling the generated quantity of the drive pulse by an output of the 1st comparator means 17, a 2nd comparator means 18 comparing the count data from the 2nd counter means 14 with 2nd data less than the feed quantity of the prescribed frame, and a control means 16 revising the 1st data with an output of the 2nd comparator means 18.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a magnetic recording / reproducing apparatus capable of driving a capstan motor at a low speed to feed a magnetic tape in a predetermined frame.

[0002]

2. Description of the Related Art In a helical scan type VTR which forms a recording track tilted with respect to the longitudinal direction of a tape, a video signal of one field is formed on one recording track, so that reproduction is performed with the tape running stopped. You can get the output. Then, in this still image reproduction, noise generated when the scanning locus is different from that recorded can be driven into the vertical blanking period by changing the tape stop position. That is, it is possible to prevent noise from being generated in the still image reproduced image.

As one of the noise purging methods, there is a method of driving the magnetic tape at a low speed and stopping the running of the tape when the noise during reproduction output and the pulse indicating the vertical blanking period coincide with each other. (JP-A-4-37337
No. 9).

According to this method, when the magnetic tape is driven at a low speed, a frequency generator (hereinafter referred to as F
The output pulse of G) is counted, and a fixed amount of tape is always fed so that noise is driven into the vertical blanking period.

By the way, the VTR for editing has a function of sending a frame in order to find a position to be edited from the above-mentioned still picture reproduction state. Conventionally, in order to carry out this frame feeding, the above-mentioned low speed driving is repeated to drive noise into the vertical blanking period, and the magnetic tape is fed by a predetermined frame depending on the number of times it is driven.

[0006]

However, when the magnetic tape is driven at a low speed in the above-mentioned structure, the feeding amount of the magnetic tape corresponding to a predetermined frame is not known, so that the vertical movement is ensured at the predetermined frame. The width of the reference pulse indicating the blanking period must be set wide, which may cause noise at the top or bottom of the playback screen.

It is also possible to control the feed amount corresponding to a predetermined frame by accumulating the counts of FG pulses during low speed driving. However, when the low speed driving is stopped, the magnetic tape is slightly fed due to inertia. There is a drawback in that the magnetic tape cannot be accurately fed by a predetermined frame even if the FG pulse is counted only during low speed driving.

Further, when the load applied to the capstan motor changes depending on the winding diameter of the tape, the ambient temperature, etc., this problem becomes remarkable.

[0009]

Therefore, in the present invention, a drive pulse generating means for generating a drive pulse based on a low speed drive signal, and an FG attached to a capstan motor.
And first and second counting means for counting the output pulse of the FG (hereinafter, FG pulse), count data from the first counting means, and a feed amount necessary for driving the magnetic tape at a low speed. First comparing means for comparing the first data to be generated, driving pulse control means for controlling the generation amount of the driving pulse by the output of the first comparing means, count data from the second counting means and the predetermined frame. The second comparing means for comparing the second data smaller than the feeding amount of the second data and the control means for changing the first data by the output of the second comparing means.

[0010]

According to the above construction, the first and second comparing means for counting and comparing the FG pulses are provided, the magnetic tape is fed to the vicinity of the predetermined frame by the second comparing means, and the final comparing means is used for the final comparison. Since the feeding amount is determined, the magnetic tape can be fed accurately by a predetermined frame.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit block diagram of the embodiment, and FIG. 2 is a waveform diagram of each part for explaining the operation.

In FIG. 1, 1 is an input terminal to which a reproduced video signal is connected, 2 is an input terminal to which a head switching (RF switching pulse) signal having a predetermined phase relationship with the reproduced video signal is connected, and 3 is a reproduced video. The noise detection circuit detects noise from a signal and outputs a detection pulse d having a predetermined pulse width. Reference numeral 4 is a reference pulse generating circuit which outputs a pulse having a predetermined width corresponding to the vertical blanking period from the timing of the fall of the head switching signal. Here, the pulse having a predetermined width is set as narrow as possible so that noise is not generated on the reproduction screen. Reference numeral 5 detects whether or not the timing positions of the output of the noise detection circuit 3 and the output of the reference pulse generation circuit 4 match, and when they match, a reset signal and a LOW signal are output to a second counting circuit and an AND gate 10, which will be described later. It is a position detection circuit that supplies a signal.

Reference numeral 6 is an input terminal to which a low-speed drive signal a issued for sending a magnetic tape for a predetermined frame is connected, 7 is a D-type flip-flop, 8 is a differentiation circuit for differentiating the Q output of the flip-flop 7, and 9 is a drive. An RS flip-flop that controls the amount of pulse generation, 10 is an AND gate that supplies a drive pulse to a capstan motor 11 until the magnetic tape is sent for a predetermined frame, 11 is a capstan motor, 1
F is attached to the capstan motor 11 and outputs an FG pulse according to the rotation of the capstan motor 11.
G. Reference numeral 13 is a first counting circuit that counts FG pulses only during the HIGH period of RF switching pulses, and 14 is a second counting circuit that counts FG pulses until noise is driven into the vertical blanking period.

Reference numeral 15 denotes data corresponding to a feed amount required for driving the magnetic tape at a low speed, second data smaller than a feed amount of a predetermined frame, and a moving amount caused by inertia of the capstan motor 11 as shown in FIG. Is a control circuit which stores a characteristic table indicating the above, and 16 is a control circuit which performs arithmetic operation and reads various data from the storage circuit 15 and supplies the data to first and second comparison circuits 17 and 18 which will be described later. Reference numeral 17 is a first comparison circuit that compares the count data counted by the first counting circuit with the first data read by the control circuit 16 and supplies a reset signal to the RS flip-flop 9 when they match, The count data counted by the second counting circuit is compared with the second data read by the storage circuit 16, and when they match, the control circuit 16
2 is a second comparison circuit for supplying a coincidence signal to.

Next, the operation of the present invention will be described with reference to FIG.

To carry out the frame feeding of the present invention, as in the prior art, the low speed driving is first repeated to drive the noise into the vertical blanking period so that the noise is not generated in the still image reproduced image.

In this state, for example, when feeding the magnetic tape by one frame, first, the operation button (not shown) of the VTR is operated. As a result, the low-speed drive signal a rises to HIGH level and is supplied to the D terminal of the D-type flip-flop 7. When the RF switching pulse c is supplied to the CK terminal of the D-type flip-flop 7, the H output is output from the Q output terminal.
The H level is output and supplied to the set terminal of the RS flip-flop 9 via the differentiating circuit 8. The RS flip-flop 9 receives the HIGH level and supplies a drive pulse to the AND gate 10. At this time, since the output of the position detection circuit 5 of the AND gate 10 is at the HIGH level, the drive pulse is applied to the capstan motor 11.

As a result, the capstan motor 11 is driven at a low speed, and the FG pulse is generated from the FG 12. This FG pulse is transmitted to the first and second counting circuits 1
The first data counted in 3 and 14 are sequentially supplied to the first and second comparison circuits 17 and 18. The first comparison circuit 17 compares the count data counted by the first counting circuit 13 with the first data read from the storage circuit 15 by the control circuit 16. Here, as the data used at this time, preset data (here, “4”) is read because it is necessary to always drive the magnetic tape by a fixed amount. When the first comparison circuit 17 detects a match,
The reset signal f is supplied to the reset terminal of the RS flip-flop 9, and the generation of the drive pulse d is stopped. At this time, the magnetic tape is slightly fed due to the inertia of the capstan motor. That is, two FG pulses are counted due to inertia as shown in FIG. 2e.

When the above-mentioned low speed driving is performed from the still image reproducing state, the positional relationship between the track on the magnetic tape and the rotary head is deviated, and noise is generated in the reproduced video signal as shown in FIG. 2b. This noise is detected i by the noise position detection circuit 3, and the position detection circuit 5 detects whether or not the timing position matches the reference pulse j from the reference pulse generation circuit 4. In this case, since they do not match, AND gate 1
A HIGH level k is supplied to 0. Then, the above-mentioned low-speed operation is repeated, and when the noise and the timing position of the reference pulse coincide with each other, the LOW level k is supplied to the AND gate 10 to stop the low-speed driving and stop the low-speed driving signal. A reset signal is supplied to the reset terminal of to clear the count data. Therefore, the low speed driving is repeated until the noise is drawn in the vertical blanking period.

On the other hand, the second comparison circuit 18 compares the count data counted by the second counting circuit 14 with the second data read by the control circuit 16 from the memory circuit 15. Here, as the second data used at this time, preset data smaller than the feed amount of one frame is read. For example, if the FG attached to the capstan motor 11 generates a pulse of 2160 Hz in 1 second, the pulse generated in one frame will be 72 Hz. Therefore, the second data set here is less than the feed amount of one frame, and therefore, for example, "68".
Are stored in the storage circuit 15.

When the second comparison circuit 18 detects a match, it supplies a match signal to the control circuit 16, whereby the control circuit 16 receives the second signal when the magnetic tape is stopped.
The final drive amount is calculated by fetching the count data of the counting circuit 14, and the data is extracted from the calculation result by referring to the characteristic table representing the movement amount generated by the inertia of the capstan motor, and the first comparison circuit is used as the first data. Supply to 17. As a result, the first comparison circuit 17 has the changed first
The data is compared with the count data from the first counting circuit 13, and when a match is detected, a reset signal is supplied to the RS flip-flop 9, and the RS flip-flop 9 receives the reset signal and stops the drive pulse. Since the feeding amount of the magnetic tape at this time also considers the feeding amount generated by inertia, one frame can be fed accurately.

Therefore, according to the present embodiment, the FG pulse of the FG attached to the capstan motor 11 is counted, and one frame is sent in consideration of the movement amount caused by the inertia of the capstan motor 11. ,
The magnetic tape can be fed very accurately, and even if one frame is fed, noise can be reliably driven into the vertical blanking period.

In this embodiment, only one characteristic table showing the inertia is prepared, but in the case of the magnetic tape, considering that the tape feed amount due to the inertia is different at the beginning and the end of the tape winding, A plurality of characteristic tables representing the amount of movement caused by inertia corresponding to the beginning and end of winding of the magnetic tape are prepared, and the tape disclosed immediately prior to the 1-frame feed mode by using the technique disclosed in Japanese Patent Application Laid-Open No. 2-81389. The remaining amount may be calculated and the characteristic table may be selected based on the remaining amount data.

In this embodiment, the second data is set in the storage circuit 15 in advance. However, the count data of the second counting circuit 14 when the first frame feeding is performed, that is, the reset signal of the position detecting circuit 5 is performed. The count data at the time when the second counting circuit 14 is cleared by the above may be stored in the storage circuit 15 as the second data, and thereafter the data may be used to control.

[0025]

According to the present invention, when the magnetic tape is fed by a predetermined frame, the feeding amount is controlled by counting the FG pulses, so that the magnetic tape can be fed accurately by the predetermined frame. Further, even when the magnetic tape is sent by a predetermined frame, the noise can be surely driven into the vertical blanking period, so that there is no fear that noise will occur on the reproduction screen.

[Brief description of drawings]

FIG. 1 is a circuit block diagram showing an embodiment of the present invention.

FIG. 2 is a waveform chart of each part showing the operation of the embodiment.

FIG. 3 is a characteristic table showing a movement amount caused by inertia of a capstan motor.

[Explanation of symbols]

 7 D-type flip-flop 9 RS flip-flop 12 Frequency generator (FG) 13 First counting circuit 14 Second counting circuit 16 Control circuit 17 First comparison circuit 18 Second comparison circuit

Claims (1)

[Claims] 1. A video signal recorded on a magnetic tape is reproduced as a still image, and the stopped magnetic tape is driven at a low speed in a predetermined direction to drive noise into a vertical blanking period. In this state, a capstan motor is driven at a low speed. In a magnetic recording / reproducing apparatus capable of sending a predetermined frame, a drive pulse generating means for generating a drive pulse based on a low speed drive signal, a frequency generator attached to a capstan motor, and an output pulse of the frequency generator. First and second counting
Counting means, first comparing means for comparing the counting data from the first counting means with the first data corresponding to the feed amount required to drive the magnetic tape at a low speed, and the output of the first comparing means Drive pulse control means for controlling the generation amount of the drive pulse by means of: second comparing means for comparing the count data from the second counting means with second data smaller than the feed amount of the predetermined frame; A magnetic recording / reproducing apparatus comprising: a control unit that changes the first data according to an output of a comparison unit.