JPS63121368A - Magnetic picture recording and reproducing device - Google Patents

Abstract

PURPOSE:To execute slow motion reproduction by executing modulation with a value in which a tracking error signal at the time of travelling which has detected the start period of a tape travelling stop is multiplied by the value calculated from the amplitude of the tracking error signal at the time of stopping. CONSTITUTION:The tracking error signal is detected from a reproduced signal obtained by a magnetic head 1, and is transmitted to a microcomputer 5. The computer 5 outputs various control signals for executing slow motion reproduction from the tracking error signal and a head scan switching signal. The computer 5 stores the amplitude of the tracking error signal when the magnetic tape travel stops at the time of slow motion reproduction, caltulates and stores the value in proportion to the stored amplitude. With the value in which the detected tracking error signal when the tape travels is multiplied by the calculated value, modulation is executed, and it is outputted to a speed control circuit 6 as the start timing of a brake. Even if the sensitivity of the tracking error signal changes thus, slow motion reproduction can be executed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to magnetic recording and reproducing devices, particularly rotary head type VTRs.
This relates to a VTR in which a tracking error signal for tape feeding is obtained from a playback signal from a video head.
This is in between slow motion playback.

Conventional technology VTRs with the ``8 mm video'' standard record a 4-frequency pilot signal for tracking control along with the video signal as a tracking control method, and during playback, the track to be played is The level difference between the crosstalk components of the pilot signals is used as a tracking error signal.

A method of detecting a tracking error signal using a pilot signal will be explained below.

In FIG. 8, A1. Bl, A2. B2... are each recording track recorded by the A head and the B head.

Arrow (a) indicates the scanning direction of the rotary head. In each recording track, each pilot signal indicated by r1 to f4 is sequentially recorded for each field together with the video signal. The recording order of pilot signals is fl, f2 . f3. f4
(7) Cycling in order m, and fl is recorded next to f4. Further, within each field period, the type of pilot signal is fixed and recorded. The frequency of the pilot signal is set to the values shown in Table 1, for example. In addition, in Table 1, "H indicates the frequency of the horizontal synchronizing signal in the video signal,
This indicates that the frequency is 6.5 times the frequency of the 8.5fH horizontal synchronization signal.

Table 1 The frequency difference of the pilot signal between each recording track 1 is the 8th
As shown in the figure, the frequency is fH or 3fH.

When the head scans the AI (1=1.2...) track, the frequency difference between the pilot signal of the scanning track and the pilot signal recorded on the adjacent track on the right side on the paper is always fH, and It is always 3f
It is H. When the head scans 81 (1=1.2...) tracks, the relationship is opposite to the above, and the frequency difference between the pilot signal and the adjacent track on the right is always 3 f H
, and the one on the left is always "H".

Since the pilot signal is a relatively low frequency signal around 100 kHz, the pilot signal recorded on the adjacent track can be reproduced as a crosstalk signal without the head scanning the adjacent track.
The pilot signal obtained when the head on-tracks the A2 track and performs reproduction scanning is f3. f2. It is a composite signal of fl, and its level is highest at f3, followed by f2.
°f4 is played back at the same level. When the head slightly deviates from track A2 toward track 82 and performs reproduction scanning, the level of the pilot signal obtained is f3. f4.
It becomes smaller in the order of f2. Conversely, if the head shifts to the track B2 side and scans, the obtained pilot signal will be f.
3. f2. It becomes smaller in the order of f4. Therefore, by separating and extracting the difference signals fH and 3fH between the pilot signal on the main scanning track and each pilot signal recorded on both adjacent tracks, and comparing the reproduction levels of both signals, The amount and direction of head displacement can be known.

FIG. 9 is a block diagram of a reproducing circuit for obtaining a tracking error signal. In FIG. 9, a circuit 102 to which a reproduced signal in which a video signal, a pilot, and a signal are combined is inputted from a terminal 101 is a low-pass filter, which extracts only the pilot signal from the combined reproduced signal. The pilot signal obtained at the time is a composite signal of the pilot signals recorded on the main scanning track and both adjacent tracks.0 circuit 103 is a balanced modulator, and the aforementioned composite pilot signal is supplied from the terminal 104. Multiply by the reference signal. The reference signal supplied from the terminal 104 supplies a signal with the same frequency as the pilot signal recorded on the main scanning track. For example, in FIG. The input signal to the device 103 is f2. f3. f4, and the signal input from the terminal 104 is "3".

Therefore, the output signal of balanced modulator 103 is f2. f3. f4
Signals of the sum and difference frequencies of each signal of and the signal of f3 are output. Circuit 105 is a tuned amplifier tuned to the fH signal, and circuit 107 is a tuned amplifier tuned to the 3 r H signal. Circuits 106 and 108 are amplitude detectors, and circuit 109 is a level comparator. Therefore, each pilot signal taken out as a crosstalk signal from both adjacent tracks is taken out as a difference signal with the pilot signal recorded on the main scanning track, and then the level comparator 109 determines the level. A signal corresponding to the difference is taken out to terminal 110. As for the signal obtained at the terminal 110, when the reproduction level of fH is higher than the reproduction level of 3fH, a (+) potential corresponding to the level difference is taken out, and in the opposite case, a (-) potential is taken out. terminal 1
Since the signal extracted at 10 includes information on the amount and direction of the head's track deviation, it can be used as a tracking error signal. However, a tracking error signal that is actually suitable for practical use requires further processing. This is because, as is clear from FIG. 8, the relationship between the direction of head deviation and the resulting chestnut calculation output (-fH or 3fH) for the A1 track and the Bl track is opposite to each other. be. For this reason, the analog inverter 111
By using the switch 112, the signal at the terminal 110 can be inverted in an analog manner when the head scans the Al track and when the head scans the Bl track. 110! c'' connection, and when scanning the BJ track, it is connected to the output of the analog inverter 111. This depends on whether the pilot signal name is odd or even.
This can be handled by switching. As a result, terminal 114
The output signal of is always (+
) is shifted to the left, a (-) potential is always applied. Therefore, by controlling the capstan motor using the signal obtained at the terminal 114, the head can always be scanned on-track on the main scanning track.

The above is an outline of the method for obtaining a tracking error signal using pilot signals of four frequencies.

FIG. 2 is a timing waveform diagram showing a method of intermittent slow motion and motion playback in 8 mm video. FIG. 3 is a diagram showing the same operation on a tape recording pattern. First, assume that the tape is stopped. A1 in this state. Continue until head scanning of Bl. At this time, since the track to be scanned does not change, the pilot signal of the track remains, for example, fl. In FIG. 3, the head scans from the lower right to the upper left. The tracking error signal at this time has a sawtooth waveform that repeatedly changes from a state in which the head is ahead by 0.5 track pitch to a state in which it is behind by 0.5 track pitch for each head scan. The tracking error at the center of the track is in an on-track state. The output of the head at this time is maximum at the center of the scan, and decreases slightly at the beginning and end of the scan. However, if the width of the head is set wider than the track pitch, it is possible to prevent the output from decreasing, so there is no problem in practice.

Next, tape feeding is started in the A2 head scan.

That is, the motor is started near the center of the A2 scan.

The target speed of the motor is the same speed as the speed at the time of recording. That is, from the middle of scan A2, the tape feeding speed becomes 1x speed. In FIG. 3, the head scans from the lower right to the center in the same way as when stopped, and from the center it scans parallel to the track.

The tracking error signal at this time becomes flat from the middle of scan A2. Moreover, since the signal is sent at 1x speed from the on-track state, the tracking error signal is almost equal to the on-track value. Therefore, the output of the head can be maintained at the maximum output state after starting the motor.

Next, in scanning 82, if the tape feeding speed is 1x speed, the head scans the adjacent track, so the pilot signal used is r2.

In FIG. 3, scanning is performed parallel to the track.

The tracking error signal obtained at this time is flat as in the previous scan. The head output remains at maximum output.

Next, in head scan A3, since the tape has advanced one more track, f3 is used as the pilot signal. Now, in scanning A3, tape feeding is stopped approximately at the center of scanning.

In other words, the brakes are applied approximately at the center of the scan. This allows the motor to stop suddenly. In FIG. 3, the head scans from the bottom center of the track parallel to the track to the center of the track, and from there it scans toward the top left. The tracking error signal changes from a previously flat state to a sawtooth waveform similar to the scanning of AI and B2. That is, the tracking error signal starts to lag from the center of the 83, and at the end of the scan, there is a lag of 0.5 track pitch.

The scanning after the next B3 is in a stopped state, the pilot signal used is f3, and the tracking error signal is AI,
Like Bl, it has a sawtooth waveform, and the output of the head is maximum at the center of the scan, and slightly decreases at the beginning and end of the scan. In FIG. 3, the head corresponds to scanning from the lower right to the upper left. Note that since 8 mm video is recorded in an azimuth manner, it is necessary to select a playback head according to the azimuth of the track to be scanned, but this is well known and will not be described here.

Now, when playing an actual tape, it does not always stop at the same place due to fluctuations in the starting characteristics of the motor and variations in the mechanical accuracy of the device, so it is necessary to perform tracking control. That is, in scan B2, the tracking error signal is checked, and if the tape is in an advanced state, the brake start time is advanced, and if the tape is in a delayed state, the t-brake start time is delayed. For example, if the tracking error signal is delayed by 0.1 tora Nikubich, the brake start timing may be delayed by 0.1 head scanning period. This allows the tape to always be stopped at the same position.

Problems to be Solved by the Invention This method of detecting a tracking error signal uses the difference in level of crosstalk components from adjacent tracks for a scanned track as a tracking error signal. The tracking error detection sensitivity changes depending on the reproduction level. For example, on tapes recorded with different VTI't, the recording level of the pilot signal may be different. Therefore, even if the tracking error signal is read at a constant speed and the amount of track deviation is determined, the amount of track deviation may differ from the actual track deviation depending on the recording level.

For this reason, in the past, it was necessary to insert an automatic gain control circuit (AGC) before the above-mentioned balanced modulator in order to keep the pilot signal level constant during reproduction.

Means for Solving the Problem In order to solve the conventional problem, the present invention uses an arithmetic circuit to determine the relationship between the tracking error signal and the actual track deviation from the amplitude of the tracking error signal when the tape is stopped. This relationship is used to know the actual track deviation during constant speed driving, and the conventional automatic gain control circuit is not particularly required.

The action calculation circuit outputs a tracking error signal of 1 when the tape is stopped.
The amplitude of the tracking error signal is calculated by reading two or more points per head scan. Since the amplitude of the tracking error signal is one track pitch when the tape is stopped, it is possible to know how much track deviation corresponds to 1 volt of the tracking error signal. Using this result, if the tracking error signal is known, the actual amount of track deviation can be calculated. Therefore, when the tape is being fed at a constant speed, the tracking error signal can be used to determine how much the braking start timing should be modulated.

Embodiments Before explaining the embodiments, the principle of the present invention will first be explained. FIG. 7 is a waveform diagram comparing the tracking error signal with the head scan switching signal when the tape is stopped running. When the reference pilot signal is fixed while the tape is stopped, the tracking error signal becomes a kind of sawtooth waveform. When the reproduction level of the tracking pilot signal is high, the rate of change becomes large, as shown by the broken line, and when the reproduction level of the pilot signal is low, the rate of change of the sawtooth waveform becomes small, as shown by the solid line. In this way, the rate of change of the tracking error signal varies depending on the reproduction level, but in any case, the amplitude is equal to one track pitch. Therefore, by detecting the rate of change of the tracking error signal when the tape is stopped, the detection sensitivity of the tracking error signal with respect to track deviation can be determined. For example, the difference between the tracking error signal at timings (a) and (b) is , is clearly proportional to the rate of change. If the time difference between (a) and (b) is 1/2 head scanning period, the signal difference is 1/2
This corresponds to 2 tracks. Examples using this principle will be described below.

FIG. 1 is a circuit block diagram showing the overall configuration of an embodiment of the present invention. That is, a reproduction signal obtained from the magnetic head 1 is sent to a video signal reproduction circuit 3 and a tracking error signal detection circuit 4 via an amplifier 2. The video signal reproducing circuit 3 processes the reproduced signal and outputs it as a video signal.

On the other hand, the tracking error signal detection circuit 4 is a circuit for obtaining a tracking error signal from a reproduced signal, and its principle is as already explained. The tracking error signal obtained from the tracking error signal 4 is sent to the microcomputer 5. The microcomputer 5 reads the tracking error signal and the head scan switching signal and outputs various control commands for slow motion reproduction. The commands include a reference pilot signal selection signal to the tracking error signal detection circuit 4, and a speed command/brake command to the speed control circuit 6 of the capstan motor 8. Capstan motor8. The speed control circuit 6 inputs the rotation detection signal obtained from the capstan rotation detector 9, and
A drive command for controlling the rotational speed of the capstan motor 8 to a constant value is sent to the capstan motor 8 via the motor drive circuit 7.

4 to 6 are flowcharts showing the processing contents of the microcomputer 5 in FIG. 1, FIG. 4 is a schematic flowchart, and the pJIS diagram shows the method of calculating the amplitude and sensitivity of the tracking error signal. FIG. 6 is a flowchart for calculating the timing to start braking.

FIG. 4 is a flowchart showing an outline of the processing of the microcomputer 5. This process is assumed to be performed at regular intervals.For example, a timer interrupt may be used to perform this process for each timer interrupt. First, in process 21, the number of timer interrupts is checked.

Then, depending on the check result, processes 22, 23, 24
．． It branches to 25. First, if the capstan motor is being accelerated, the process branches to process 22, and if the capstan motor is being fed at a constant speed, the process branches to process 28. If the brake is in operation, the process branches to process 24, and if the brake is stopped, the process branches to process 25. If it is accelerating, process 2
2, an acceleration command is output to the capstan motor. Then, the process ends and the process waits until the next timer interrupt.

If constant speed feeding is in progress, the process proceeds to step 23 and outputs a command to rotate the capstan motor at a constant speed of 1x speed. The process then proceeds to step 26, where it is checked whether it is the timing to calculate the brake start timing. If it is not the timing to calculate, the process ends and the process waits until the next timer interrupt. If it is the timing to calculate, the process advances to step 27 and calculates the brake start timing from the tracking error signal. This calculation method will be explained in FIG.

When processing 27t' is completed, the process waits until the next timer interrupt. If the timing is such that the brake is being operated, a brake command for the capstan motor is output in step 24, and the process waits until the next timer interrupt. Also, if the capstan motor is stopped, process 2
Proceed to step 5, output the capstan motor stop command,
Proceeding to process 28, the amplitude of the tracking error signal is calculated.

The method of calculating the amplitude will be explained with reference to FIG. The content of the process shown in FIG. 4 is 0 or more, which is a wait time until the next timer interrupt after the amplitude calculation is completed.

FIG. 5 is a flowchart showing a method of calculating the amplitude of the tracking error signal in the process shown in FIG. First, in process 31, it is checked whether 1/4 period has elapsed since the spatula/do started scanning the track. This can be known, for example, by the number of timer interrupts.

If at that point, proceed to process 32; otherwise,
Proceed to process 33. In process 32, the current value of the tracking error signal is stored in the first memory FvIEM1, and the process ends. In process 38, it is checked whether 3/4 period has elapsed since the start of head scanning.

If the 3/4 period has elapsed, proceed to process 34;
Otherwise, the process ends. In process 34, the value of the tracking error signal is stored in the second memory MEM2,
Proceeding to process 35, in process 35, the first memory MEMI
and the second memory MEM2, and the obtained difference 2
Let the multiplied value be the amplitude of the tracking error signal.

Next, the process proceeds to step 36, in which a conversion coefficient between the tracking error signal and the brake start timing is calculated from the amplitude. The method of calculating the conversion coefficient is as follows.

Coefficient=(timer interrupt period)/(amplitude) zc head scanning period) When this calculation is completed, the process shown in FIG. 5 is completed.

FIG. 6 is a flowchart showing a method of calculating the timing for starting the brake operation shown in FIG. 4. In step 40, the value of the tracking error signal is multiplied by the conversion coefficient obtained in FIG. , the value subtracted from the preset brake start timing reference value,
This is the actual brake start timing.

With the above processing, even if the level of the reproduced pilot signal changes, it is possible to always know the accurate amount of off-track even without the need for an automatic gain control circuit, which is conventionally required.

Now, in the explanation of this embodiment, it has been explained that the head scans the center of the track when the tape stops running, but in reality, if we consider the initial stopped state, the head scans the center of the track. In this case, as shown in FIG. 11, it is first checked whether the value of the tracking error signal at the center of scanning (s) is approximately at the center. If it is approximately at the center as shown in waveform (a), the tape is stopped so that the head scans approximately the center of the track, so no special processing is required.Also, as shown in waveform (b), The tracking error signal may shift significantly in the (+) direction. In this case, the head is scanning another track.

In the case of waveform (b), since it is in an advanced state, it is sufficient to advance the reference pilot signal by one.Also, as in waveform (C), the tracking error signal may deviate greatly in the (-) direction. In this case as well, the head is scanning another track. In the case of waveform (c), since it is in a delayed state, it is sufficient to delay the reference pilot signal by one. By adjusting the reference pilot signal at the time of stop in this way, it is possible to transition to a state where it is easy to calculate the detection sensitivity of the tracking error signal, and also to select the track closest to the moxibustion for the next intermittent slow motion playback. It turns out.

FIG. 10 is a flowchart showing processing in such a case. The result of process 33 in FIG. 5 is N
Insert at the destination in case o. In FIG. 10, as a process 201, it is checked whether the timing is (S). If the timing is (S), proceed to process 202;
Otherwise, exit. In process 202, it is checked whether the tracking error signal at (S) is a sufficiently large value with respect to the center value, and if it is a sufficiently large value, the process proceeds to process 203; otherwise, the process proceeds to process 204. , upon finishing the process 203 of advancing the reference pilot signal,
The process shown in FIG. 10 ends. In process 204, it is checked whether the tracking error signal at timing (s) is sufficiently small. If it is sufficiently small, the process proceeds to process 205, and if not, the process of FIG. 10 is ended. In process 205, one reference pilot signal is returned, and the process in FIG. 10 ends.

Alternatively, it is also possible to correct the stop position by transporting the tape using a capstan motor so that the initial stop position is at the center of the track.

As described in detail, the present invention provides a slow motion system that eliminates the need for an automatic gain control circuit, which was required in the past, since the reproduction level of the pilot signal fluctuates and the sensitivity of the tracking error signal changes. This provides a reproduction method.

In this example, a microcomputer was used to detect fluctuations in detection sensitivity of the tracking error signal, output an intermittent feed command for the capstan motor, and output a reference pilot signal switching command. As shown in Japanese Unexamined Patent Publication No. 81-178762, there is a method of controlling the speed of the capstan motor and performing tracking division using a tracking error signal using an arithmetic circuit. The present invention has great effects because it can be realized by a microcomputer and no new arithmetic circuit is required.

[Brief explanation of the drawing]

Figure 1 is a circuit block diagram showing the configuration of an embodiment of the present invention, Figure 2 is a timing waveform diagram showing a method for intermittent slow motion playback in 8mm video, Figure 3 is a diagram of the same pattern, and Figure 4. , FIG. 5, and FIG. 6 are flowcharts showing the processing flow of the microcomputer in FIG. Explanatory diagram showing the recording pattern of pilot signals in 8 mm video, No. 9
The figure is a block diagram showing the configuration of the tracking error signal detection circuit, Figure 10 is a flowchart showing the processing method when the first stop position is not at the center of the track, and Figure 11 is the operating principle of the processing in the flowchart in Figure 10. FIG. DESCRIPTION OF SYMBOLS 1... Magnetic head, 4... Tracking error signal detection circuit, 5... Microcomputer, 6... Capstan motor speed control circuit. Name of agent Patent attorney Toshio Nakao 1 person Figure 1 Figure 3 Figure 5 Figure 6 rXi Figure 7 Figure 9 Bi Figure 8 fH8IfF, l3krsh 3fs9 Figure 9 tos iθ6 Figure 10 Figure 11 C3) 1, i17-

Claims (1)

[Claims] Video signals and tracking control pilot signals are recorded and reproduced as discontinuous magnetization trajectories on the magnetic tape by a rotating head, and during reproduction, a crosstalk pilot signal from both adjacent tracks to the track to be reproduced is generated based on the level difference. In a magnetic recording/playback device that realizes slow motion playback by obtaining a tracking error and intermittently feeding the tape, detecting a tracking error signal when the magnetic tape stops running during slow motion playback, and detecting and storing its amplitude. and means for calculating and storing a value proportional to the detected and memorized amplitude, which detects a tracking error signal during running of the magnetic tape, and determines when to start stopping tape running based on the detected tracking error signal during running of the magnetic tape. A magnetic recording/reproducing apparatus characterized in that modulation is performed by a value obtained by multiplying a tracking error signal by the calculated value.