JP2919710B2 - Magnetic recording / reproducing device - Google Patents

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 for displaying a reproduction screen on a frame-by-frame basis and displaying the time, and more particularly, to a method for counting the number of frames at the time of low-speed driving.

[0002]

2. Description of the Related Art If a playback screen can be counted in units of hours, minutes, seconds, and frames, video editing in units of frames becomes possible, which is very effective when performing video editing. When determining the position of the playback screen in frame units, the conventional VT
In R, a control signal (hereinafter, a CTL signal) recorded on a magnetic tape is counted. That is, 1
In a / 2 inch VTR, the CTL signal at the edge of the magnetic tape is reproduced by a control head, and if this is counted, the reproduction position can be known in frame units.

[0003] In video editing, a transition from still reproduction to slow reproduction or a transition from still reproduction to reverse slow reproduction is frequently performed. At this time, since the magnetic tape is sent at a very low speed, the CTL signal is not reproduced, and a counting error occurs, so that there has been a problem that an accurate number of frames cannot be obtained.

In order to solve this problem, Japanese Patent Laid-Open Publication No.
In Japanese Patent Publication No. 8178 (G11B27 / 17), the number of output pulses (hereinafter referred to as FG pulses) of a frequency generator generated with the rotation of a capstan motor is counted by a number corresponding to a feed amount of one frame of a magnetic tape. , A pseudo CTL signal is generated, and the number of pseudo CTL signals is counted to display the correct number of frames.

[0005]

However, recent VTs
As the R mechanism, in order to reduce the number of motors, a system in which a reel base is driven via a rubber belt from a capstan motor is often used. When the low-speed drive (intermittent drive) is performed using this mechanism as described above, the capstan motor is reversed by the tension of the rubber belt every time the capstan motor stops. Due to this inversion phenomenon, an FG pulse in the reverse direction is generated, and the counter circuit counts the FG pulse in the reverse direction to create a pseudo CTL signal. There is a disadvantage that a large number of frames cannot be obtained.

[0006]

Accordingly, the present invention provides a magnetic recording / reproducing apparatus which counts a control signal recorded on a magnetic tape, converts the control signal into a frame unit time, and displays the time. Drive pulse generating means for generating a drive pulse to the capstan motor, prohibiting means for prohibiting supply of a control signal to the counting means by the low-speed drive signal, and noise detection for extracting noise of a reproduced video signal from a magnetic tape Means, reference pulse generating means for generating a pulse signal at a phase position corresponding to a vertical blanking period of a reproduced video signal, and comparing means for generating an output when the noise and the pulse signal are compared and matched. The output of the comparison means is counted during the period in which the low-speed drive signal is being issued.

[0007]

According to the above arrangement, the noise generated when the scanning track of the magnetic head is different from the recording track during low-speed driving is compared with the reference pulse signal corresponding to the vertical blanking period. Since it is determined that the tape has been sent for one frame and an output is issued to the counting means, the number of frames can be accurately counted.

[0008]

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, reference numeral 1 denotes an input terminal to which a reproduced video signal b is connected, 2 denotes an input terminal to which a head switching (RF switching pulse) signal c having a predetermined phase relationship with the reproduced video signal is connected, and 3 denotes an input terminal. A noise position detection circuit that detects noise from a reproduced video signal and outputs a detection pulse signal h having a predetermined pulse width. Reference numeral 4 denotes a reference pulse generation circuit that outputs a reference pulse signal i having a predetermined width corresponding to the vertical blanking period from the falling timing of the head switching signal. Reference numeral 5 indicates whether or not the timing position of the output of the noise position detection circuit 3 and the output of the reference pulse generation circuit 4 coincide with each other. 13. Second counting circuit 1
1 is a first comparing circuit that supplies a HIGH signal and a reset signal to the first comparator.

Reference numeral 6 denotes an input terminal to which a low-speed drive signal a for intermittently sending the magnetic tape is connected, 7 a D-type flip-flop, 8 a monostable multivibrator for controlling the amount of drive pulses generated, 9 Is the capstan motor,
Reference numeral 10 denotes a frequency generator (hereinafter, referred to as FG) which is attached to the capstan motor 9 and outputs an FG pulse according to the rotation of the capstan motor 9. 11 is a first counting circuit for counting FG pulses, 12 is a second comparing circuit for comparing a predetermined value smaller than the feed amount of one frame with the output of the first counting circuit 11, and 13 is a first comparing circuit. And an AND gate (third comparing means) for comparing the five outputs with the output of the second comparing circuit 12. Here, the second counting circuit 11, the second comparing circuit 12, and the AND gate 13 are circuits for masking the output of the first comparing circuit 5 until the FG pulse reaches a preset predetermined value. That is, if the magnetic tape has a scratch or the like, noise may be generated at a position other than the position where the reproduced video signal should be. For example, when the noise matches the reference pulse, the first comparison circuit malfunctions. I do.
Therefore, in order to minimize this malfunction, masking is performed up to the vicinity of one frame.

Reference numeral 14 denotes a control head for reproducing the CTL signal recorded on the magnetic tape, 15 denotes a waveform shaping circuit for shaping the CTL signal reproduced by the control head, 16 denotes an inverter circuit, 17 and 18 denote switches,
Reference numeral 19 denotes a first counting circuit which counts the output of the AND gate 13 during low-speed driving, and counts the CTL signal except during low-speed driving.
Reference numeral 0 denotes a display circuit for displaying hours, minutes, seconds, and the number of frames in frame units.

Here, the switches 17 and 18 are interlocked, and when the low-speed drive signal goes high, the switch 18 is turned on and the switch 19 is turned off as shown. As a result, the first counting circuit 19 performs a counting operation by the output of the AND gate 13 during the period when the low-speed drive signal is being issued.

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

When performing low-speed driving, the VTR is first set to a still state. At this time, the reproduced image is stopped in a state where the noise is driven into the vertical blanking period so that noise is not generated in the reproduced image.

In this state, for example, when the magnetic tape is intermittently driven at a low speed, an operation unit (not shown) such as a jog shuttle of the VTR is operated. As a result, the low-speed drive signal a rises to the 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 clock (CK) terminal of the D-type flip-flop 7, a HIGH level is output from the Q output terminal and supplied to the trigger (T) terminal of the monostable multivibrator 8. In response to the HIGH level, the monostable multivibrator 8 outputs a drive pulse d determined by the resistor R and the capacitor C to the capstan motor 9.
Is applied.

Further, the switch 17 is turned off by the above-mentioned low-speed drive signal a, so that the C
The supply of the TL signal is prohibited. When the switch 18 is
Since the count is N, the first counting circuit 19 performs a counting operation by the output of the AND gate 13.

The capstan motor 9 is driven at a low speed by the drive pulse d.
Is generated. The FG pulse e is counted by the second counting circuit 11, and the counted value is sequentially supplied to the second comparing circuit 12. In the second comparison circuit 12, the count value f counted by the second counting circuit 11 is compared with a preset value of 1
A predetermined value smaller than the frame feed amount is compared, and when they match, a HIGH level is supplied to the AND gate 13. Here, for example, if the FG attached to the capstan motor 9 generates a pulse of 2160 Hz per second, the pulse generated in one frame is 72H.
z. Therefore, the predetermined value set in the second comparison circuit 12 is a value smaller than the feed amount of one frame and, for example, “52” in consideration of the number of FG pulses when inverted.
Is set. When the above-described low-speed driving is performed from the still playback state, the positional relationship between the track on the magnetic tape and the rotary head is shifted, and noise is generated in the playback video signal as shown in FIG. This noise is detected by the noise position detection circuit 3, and the first comparison circuit 5 detects whether or not the timing position matches the reference pulse signal i from the reference pulse generation circuit 4. In this case, since they do not match, the HIGH level j is not supplied to one of the AND gates 13. When the above-described low-speed driving is repeated, the count value of the second counting circuit 11 matches the predetermined value “52” in the second comparing circuit 12 as shown in FIG. The HIGH level g is supplied to one of the AND gates 13. Thereby, at least the second counting circuit 12
However, until the 52 FG pulses are counted, the magnetic tape is scratched, and even if noise is generated, the magnetic tape is masked, so that no malfunction occurs.

When the timing position of the noise h coincides with the timing position of the reference pulse signal i, a high level j is supplied to the other of the AND gate 13. This gives A
The ND gate 13 outputs a HIGH level k, which is supplied to the first counting circuit 19 via the switch 18 and also supplies a reset signal to the reset (R) terminal of the second counting circuit 11 to clear the count value. . First counting circuit 19
Receives the HIGH level from the AND gate 13,
Update one count value. Then, the updated count value is supplied to the display circuit 20, and the hour, minute, second, and number of frames are displayed.

Therefore, according to the present embodiment, one frame is produced by the coincidence output obtained by comparing the noise in the reproduced video signal generated when the magnetic tape is driven at a low speed with the reference pulse signal corresponding to the vertical blanking period. Is counted, so that the number of frames can be accurately displayed.

In this embodiment, the capstan motor 9
When the capstan motor 9 is rotated in the reverse direction (reverse slow reproduction), the first counting circuit 19 is rotated by the direction instruction signal (not shown). Is controlled in the down direction.

In the present embodiment, the mechanism system for driving the reel base via the rubber belt from the capstan motor has been described. However, it is needless to say that the mechanism system can be implemented with a dedicated driving motor. . It goes without saying that the block diagram of this embodiment can be processed by software.

[0022]

According to the present invention, one frame is counted by the coincidence output obtained by comparing the noise generated when the magnetic tape is driven at a low speed with the reference pulse signal corresponding to the vertical blanking period. , The number of frames can be accurately counted and displayed.

Further, since the output of the first comparison circuit is masked until the vicinity of one frame by counting the FG pulse, malfunctions can be prevented up to the vicinity of one frame even if the magnetic tape is damaged. it can.

[Brief description of the 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.

[Explanation of symbols]

 3 Reference pulse generating circuit 4 Noise position detecting circuit 5 First comparing circuit 8 Monostable multivibrator 10 Frequency generator (FG) 11 Second counting circuit 12 Second comparing circuit 13 AND gate (third comparing means) 17 Switch 18 Switch 19 1st counting circuit

Claims (2)

(57) [Claims] 1. A magnetic recording / reproducing apparatus comprising: a counting means for counting a control signal recorded on a magnetic tape; and a display means for converting an output of the counting means into a time in frame units and displaying the time. Drive pulse generation means for generating a drive pulse to the capstan motor based on the drive signal; prohibition means for prohibiting supply of the control signal to the counting means by the low-speed drive signal; Noise detection means for extracting noise, reference pulse creation means for generating a pulse signal at a phase position corresponding to a vertical blanking period of a reproduced video signal, and output when a comparison is made between the noise and the pulse signal. And comparing the output of the comparing means with the counting means during the period in which the low-speed drive signal is issued. Magnetic recording and reproducing apparatus characterized. 2. A magnetic recording / reproducing apparatus comprising: a first counting means for counting a control signal recorded on a magnetic tape; and a display means for converting an output of the first counting means into a time in frame units and displaying the time. A driving pulse generating means for generating a driving pulse to the capstan motor based on the low speed driving signal; a prohibiting means for prohibiting the supply of the control signal to the first counting means by the low speed driving signal; A noise detection unit that extracts noise of the reproduced video signal from the tape, a reference pulse generation unit that generates a pulse signal at a phase position corresponding to a vertical blanking period of the reproduced video signal, and compares the noise with the pulse signal. First comparing means for generating an output when the frequencies match, a frequency generator attached to the capstan motor, and an output of the frequency generator. A second counting means for counting the number of pulses, a second comparing means for comparing the count value from the second counting means with a predetermined count value smaller than the feed amount of one frame, and outputting an output when they match, And a third comparing means for comparing the output of the first comparing means with the output of the second comparing means. During the period in which the low-speed drive signal is issued, the output of the third comparing means is output by the first counting means. A magnetic recording / reproducing apparatus characterized by counting.