JPS6051090A - Special reproducing device - Google Patents

Abstract

PURPOSE:To maintain a tracking follow-up motion stably against disturbance and enable to reproduce slow motion reproduction with high quality by displacing a video head with a combined signal of the first, second and third control signals. CONSTITUTION:A reproduced video signal (a) reproduced from a magnetic tape 1 through the video head 2 is detected by a detector 4 to output a reproduction signal (b). The signal (b) is digitized by an A/D converter 6 and inputted to a bus line 8. On the other hand, a reproducing head mechanism 15 is connected mechanically to the head 2 to change a relative position vertically to a video track by a control signal (c) from the bus line 8. A CPU10, an ROM11 and an interface circuit 16 inputting a tape running direction signal (d) and a tape running speed signal (s) are connected to the bus line 8. A control signal (c) is configured with the first control signal c1 of saw tooth wave corresponding to the signal (d) and the second and third control signals c2, c3 mounting the head 2 on the video track. Thus, the tracking follow-up motion can be maintained stably.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention reproduces slow motion, quick motion, still images, etc. by running the tape at a tape running speed different from the tape running speed when all the television picture signals stored on the tape are stored. The present invention relates to a special playback device for obtaining a special playback screen, and particularly to a special playback device in a helical scanning magnetic playback device.

One of the methods for recording television video signals on an all-magnetic tape is to run a magnetic tape t-t attached to a cylinder (drum) containing a rotating head, and to record an oblique image of the video signal on the tape in its longitudinal direction. There is a helical scanning video tape Φ recorder device that forms a video track (video track), and it is widely used not only for consumer use but also for professional purposes such as industrial and broadcasting purposes. In this helical scanning video tape recorder device, one field or multiple fields of video signals are usually recorded on one video track, and the rotating heald is synchronized with the vertical synchronization signal of the input video signal to be recorded. It is designed to rotate. We will discuss the case where one field of video signal is recorded on one video track, but does the present invention record one field of video signal on one video track? Needless to say, this is not limited to the case of recording.

When one field video signal is recorded on one video track, the rotary head should be positioned so that the vertical blanking section of the television signal is at the end (edge of the tape) of the first track of each video. Rotation is controlled. This control is performed by comparing the phase of a tachometer signal generated by detecting the rotational phase of the rotary head with a vertical synchronization signal of the input video signal to control the rotation of the rotary head. Therefore, during recording, the vertical synchronization signal of the input video signal and the tachometer signal always have a constant phase relationship.

When constantly reproducing a recorded video signal, the rotary head rotates at a constant number of revolutions, such as by rotating in synchronization with a synchronization signal sent from a reference synchronization signal generator or other reference signals. controlled. In this case, the running phase of the tape is controlled such that the rotating head tracks directly over the video track, for example by controlling the rotation of a capstan that drives the tape.

In the case of special playback, which features a special motion effect by combining only the tape running speed with the tape running speed during recording (steady running speed), does the 5-rotation head have a trajectory different from the recorded video track? Scan the tape. For example, when stopping a tape, if the rotating head is completely on a video track at the start of the scan near one end of the tape (e.g., the bottom edge), then - near the end of the scan, near the other end of the tape (e.g., the top edge). Now the rotating head will be on the adjacent video track. In other words, a rotary head that has been scanning one video track gradually deviates from that track and eventually scans the next track.

In the tape pattern of a tape recorded by a helical scanning video recorder device, a blank band (guard pantono) is usually provided between the video tracks, and the width ratio of the video track to the guard band is set to about 2:1. Therefore, as the rotating head falls from the track, the S/N ratio (signal to noise ratio) of the signal deteriorates, and the period during which the rotating head is scanning across two tracks is Beat interference occurs, significantly degrading the image quality.Also, when the tape is slowly run in the forward direction (steady running direction) or in the reverse direction from a stationary state, a slow motion screen corresponding to the tape running speed is played. However, in this case, the rotating head typically falls off the video track within the screen, causing bands of the image containing noise and beat disturbances to appear on the screen, and to move around the screen as the tape travels. , move upward or downward.

Such a special Mosi! ! / In order to prevent deterioration of image quality during playback, for example, as shown in Japanese Patent Laid-Open No. 55-63187, by moving (displacing) the video playback head perpendicularly to the video track, An automatic tracking method has been proposed that prevents the video playback head from falling off the video track by retracting the video track.According to this method,
When the tape is played back while being held still, for example, the video playback head that has passed through point P in FIG. 1 can be gradually displaced to trace the dashed line PQ. In this case, the video playback head will trace correctly on the track (
In this case, when the scanning head enters the vertical blanking period of the video signal, the video reproducing head is quickly fully displaced in the direction of point Q'. In this way, the video playback head will pass through point P again, and this operation can be repeated. Image reproduction during this series of operations - The displacement of the head with respect to the rotation plane becomes a sawtooth wave. That is, the displacement increases in proportion to the scanning as it moves from point P to point Q, returns to point Q' at the end of the track (artist blanking period), and becomes 0 at point P. In this case, the video playback head will suddenly be displaced by one track pitch at the end of the track. This displacement? 11- It is called a rack jump.

Now consider the case where the tape slowly moves in the same direction as the steady running of the tape (hereinafter this direction will be referred to as the forward direction) (hereinafter referred to as forward direction slow motion I!I/). If the video playback head is fixed on a rotating plane, P in Figure 1
As the tape moves around the point, the area where it has fallen off the track will be scanned. If the video playback head can be moved, the track P can be changed by moving the video playback head.
Q can be scanned repeatedly several times. However, when the video playback head approaches the displacement limit, it will not jump one track and will pass through 9 points and scan the next track (at this moment (It will be the same as track scanning during steady driving).

Now consider a case where the tape moves slowly in the direction opposite to the steady running of the tape (hereinafter this direction will be referred to as the opposite direction) (hereinafter referred to as slow motion in the opposite direction). 1 As in the case of slow motion in the @ direction, the video playback head is on track P.
Qt - After scanning several times, when it comes close to the limit of displacement, it suddenly shifts by 2 tracks, passes near the point Q'', and shifts to the previous track.This displacement totals 2 tracks.・It's called a jump.

The slow motion speed in the forward direction gradually increases), and when the speed reaches steady running speed, the one-track jump disappears. If it becomes faster than the steady running speed, then once every few times.
Occasionally, when the video playback spatula reaches its limit of displacement, an entire track may be skipped to proceed. In this case, it is called a full skip jump.

FIG. 2 shows the movement of the video playback head in the case of special playback such as stillness and slow motion. In Figure 2,
(a) is twice the speed of steady running (forward direction), (cl) is 1.
5 times speed, H → 1 or 2 times speed, ni) is steady running speed, (force is O, S times speed, (to) is 0.5 times speed, (g) is 0.2 times speed, (force is stationary, ( ) is 0.2x speed in the reverse direction, and (nu) is 1x speed in the reverse direction.Represents the trajectory of the movement of the video playback head within the rotating head.Of course, the video playback head must move when running normally. There is no. Skip/jump is when the vehicle moves suddenly from top to bottom when it is faster than steady running.

In the case of static upward motion and forward slow motion, the sudden movement from the bottom to the top is a 1+2 jump. In the case of reverse slow motion, in addition to the 1-track jump, there is also a 2-track jump where the amount is suddenly doubled from the bottom to the top of the 1-track jump.

In the above explanation, the scanning of the video playback head starts at P.
It is assumed that it starts from a point, that is, from the center of the video track. Normally, in the case of steady playback, tracking is performed by controlling the capster/, as mentioned above, so it is good to start scanning the video track from the center.In the case of special playback, such as still playback or slow motion, the video playback head and the tape run. There is generally no relationship between the two. For this reason, tracking generally needs to be considered separately. That is, even if the video playback head is moved as shown in FIG. 2 according to the running speed of the tape, the video track and the scanning locus of the video playback head will be parallel to each other, but tracking may not always be achieved. However, during steady running, tracking is achieved by fully controlling the rotational phase of the capstan and changing the tape running phase, that is, the phase of the video track, and moving the video playback head in parallel in the direction perpendicular to the rotating plane. This is completely equivalent to tracking that matches the tape scanning phase of the video playback head with the phase of the video track, so in the case of special playback, by moving the video playback head in parallel up and down the entire operating trajectory shown in Figure 2. Tracking can also be maintained.

Conventionally, in addition to moving the video playback head in accordance with the tape running speed, a method for controlling the scanning trajectory of the video playback head to be in the center of the video track has been done by moving the video playback head to move the played signal (generally the video signal). By FM
There is a method of controlling the modulated high frequency signal) so that it is maximized. FIG. 3 shows the relationship between the relative position of the video playback head in the vertical direction with respect to the video track and the playback signal level.

When the video playback head is in the center of the video track (3rd
The playback signal level reaches its maximum at point a in Figure 3), and when the video playback head moves away from the center of the video track b (point a in Figure 3).
-b or a-c), the playback signal level gradually decreases, and when the video playback head is deviated from the center of the video track by a distance of 172 the video track width (including the guard band) (at the point shown in Figure 3 or At point 0), the reproduced signal level is at its minimum, and when it is further off, the reproduced signal level increases again by reproducing the signal recorded on the adjacent video track.

Now, the video playback head is pointing to the video track as shown in Figure 3.
If it is at the point, the reproduced signal level SO is obtained. If the video playback head is intentionally moved to point 11, which is closer to point b by ΔP, the playback signal level will change from f3o to 8.
Decrease to 1. On the other hand, from the video playback head t-20 point to 22
When moving to the point, the reproduction signal level increases from SO to 8 snow. Also.

When the video playback head is at point a, that is, when tracking is achieved, if the position of the video playback head is moved by a small amount, the level of the playback signal decreases regardless of the direction of movement;
When the video playback head is completely off the video track, such as at point or zero, if the video playback head is moved by a small amount, the playback signal level will increase regardless of the direction of movement.

When you move the video playback head by a minute amount, the direction of movement and
Although it is possible to know the center sound of the video track from the increase/decrease in the playback signal level, when this control is started from the point shown in Figure 3 or from the 0 point, it may not be possible to know the center point a of the video track. This is because the playback signal level increases no matter which side of the video track the video playback head moves in the vertical direction. If you think about it, you can definitely see the entire center of the video track. However, in reality, even if the video playback head perfectly traces the center of the video track, the playback signal level S11 changes from moment to moment due to changes in the contact between the magnetic tape and the video playback head, changes in tape tension, recording frequency, etc. do.

In other words, since the playback signal level changes due to factors other than changes in the relative position between the video track and the video playback head, the video playback head is moved to the center of the video track based only on the increase or decrease in the playback signal level when the video playback head is moved by a minute amount. It is difficult to maintain tracking.

The above means that even if it is assumed that the video track recorded on the tape is an ideal straight line, there are disturbance elements caused by various factors that impede the acquisition of highly accurate control signals. Furthermore, it is known that the linearity of an actual video track has a curve within a defined standard. The shape and amount of curvature is relatively low among devices from the same manufacturer, and the deviation in video track curvature between devices is small. Even with the same device, the video track composition may vary slightly depending on various factors such as usage conditions such as temperature and humidity, the age of the tape used, and the degree of wear on the tape running mechanism of the device. . In this case, the deviation of the video track is generally not so large as to pose a problem in terms of tracking accuracy. However, because the shape of the video track curvature differs between devices manufactured by different manufacturers, the deviation of the video track curvature may be large, affecting tracking accuracy and causing a decrease in image quality. In severe cases, noise may be observed in a single image, resulting in a definite problem. This relationship is shown in FIG. In general, when the video tracks are aligned at the center as shown in the figure, it can be seen that there is a significant difference in the curvature between the X and Y video tracks at both ends of the tape. Considering the difference in video track curvature in directional slow motion, in the case of forward directional slow motion motion, it is the same as the tape running direction during recording. Therefore, the tape tension before and after the video head drum mechanism to which the rotary head is attached can be maintained approximately the same as during recording. However, in reverse slow motion, the tape running direction is opposite to that during recording, and the tape tensions before and after the video head drum mechanism have an opposite relationship to that during recording. This difference in tape tension affects the video track curvature, causing curvature at both ends of the deodorant as shown in FIG. 6, causing tracking errors. The difference in tracking caused by the video track curvature mentioned above can be solved by conventional automatic track following devices, such as those introduced in Japanese Patent Laid-Open No. 5
7-23368 is not corrected.

SUMMARY OF THE INVENTION An object of the present invention is to provide a special playback device that is capable of stable tracking control and that can correct tracking errors caused by the above-mentioned video track composition.

Although the amount and direction of video track bending are not always constant and vary, there is a correlation with the running direction and running speed of the magnetic tape.

This means that when correcting tracking errors caused by video track curvature, a correction signal is uniquely generated based on certain fixed data, and the displacement it'1 of the video head is
This means that it is not possible to compensate in all cases for the video track music position, which changes depending on the running direction and speed of the magnetic tape. , -f: In the present invention, a signal for correcting tracking errors caused by video track curvature is generated in accordance with changes in the track curvature, that is, in accordance with the running direction and running speed of the magnetic tape. This enables optimal tracking control i11' that compensates for video track distortion in all cases.

The present invention provides a means for generating a first control signal having a sawtooth shape with a slope corresponding to the tape running speed, and a sawtooth shape or an approximate curve thereof having a slope that compensates for a tracking error depending on the tape running speed and the running direction. and means for generating a third control signal for causing the entire video head to displace in accordance with the amplitude of the reproduced signal from the video track. The entire feature is that the video head is displaced by a signal that is a combination of the second and third control signals.

An embodiment of the present invention will be described with reference to all of FIGS. 7 to 10. FIG. 7 is a block diagram showing the configuration of this device. In the figure, a reproduced video signal a reproduced from a magnetic tape 1 through a video head 2t is amplified by an amplifier 3 and rectified by a detector 4.

The output of the detector 4 is an envelope of the reproduced video signal a (hereinafter referred to as a reproduced signal). The reproduced signal further passes through a low-pass filter 5 to remove unnecessary high frequency components, is converted into a digital signal by an analog-to-digital converter 6, and is then connected to a pass line 8 via an interface circuit 7vi. . On the other hand, the playback head drive signal C passes through the interface circuit 12 from the path line/8, converts it into an analog signal at the digital-to-analog converter 13, and is further amplified by the playback head drive signal amplifier 14 to be converted to a playback head drive signal. It is input to fl15. Since the video playback head 2 is mechanically connected to the playback head drive mechanism 15, the playback head drive signal C allows the video playback head 2 to change its relative position in the vertical direction with respect to the video track recorded on the tape l. It has become. A random access memory 9 (hereinafter referred to as RAM) for storing the A/D converted playback signal b2.
Central processing unit (CPU)10. A read-only memory 11 in which a control program 2 is stored is connected to the pass line 8. A tape running direction signal d and a tape running speed signal SU are connected to the pass line 8 via an interface circuit 16ft.

Furthermore, an interface circuit 17 is connected to the pass line 8 for outputting an 1-track jump signal 11, a 2-track:9-track jump signal 12°, and a skip jump signal 1st according to the displacement of the video playback head 2 to the outside. Preset data of the data preset switch group 18 is connected to the pass line 8 via an input p-7 ace circuit 19t''.

Next, a method of generating the reproducing head drive signal C will be explained. Figure 8 shows an example of static city regeneration, and the control signal CI
Control signal 03L is a sawtooth waveform control signal generated from the tape running speed signal d, and is a signal for placing the video playback head 2 on the center of the video track. This is a step wave-like control signal generated from the control direction with respect to the vertical direction of the video track.

Here, the control signal C3 is set to 0.0 in the RF output from the head.
This is a displacement signal that gives a change of about 5 to 1.0 dB.

Here, the control signal C2 is a control signal for correcting tracking errors due to curvature of the video track. Control signal C
2 is output throughout the entire video track, and its waveform shape changes approximately depending on the tape speed, and a desired control signal can be obtained by optimizing its amplitude value.

In this embodiment, a correction signal having characteristics as shown in the figure is output at the start portion of the video track (approximately 1/4 section of the video track) in response to static playback. The amplitude a of the control signal Cz is varied according to the preset data in order to set the correction amount to the optimum value, and the signal waveform corresponds one-to-one to the running direction and running speed of the magnetic tape. . These control signals C1°C2 and Cst-CPU perform an addition operation to obtain a control signal C.

Next, generation of the control signal C2 will be described in detail. On Minomoto's side, the entire section of the video track is divided into 32 equal parts and the correction data t-
I remember R10 lock K. That is, high-order music #t-3 for correction
It is approximated by two straight lines. In addition, the tape running speed is quantized by dividing the speed from stationary to steady playback speed (PLAY) into 16 equal parts as the minimum unit, and in the forward direction from Seiya to twice the steady playback speed, and in the reverse direction from stationary to steady playback speed. All 49 copies are quantized, including the playback speed. The 49 correction patterns approximated by 32 straight lines are R(
Stored in JMI 1. A correction pattern corresponding to the direction signal d1 and traveling speed signal S read from l1016 is selected from 49 correction patterns, and further l
One of the 32 section data is selected by the timing signal read from 1020. On the other hand, the preset data of the switch group 18 read from l1019 is multiplied by the selected correction data to obtain the control signal C2. Each calculation and control is performed by CPU10 shown in FIG.

Next, generation of the control signal C3 will be described in detail with reference to FIG. In order to distinguish the video tracks, the video tracks are tentatively named N-2, N-1, and N in the reproduction 111it. However, 1
For example, during still playback, the same video track recorded on the tape is played back.

N-2 to N are the same video tracks on the tape, and during constant speed playback, N-2 to N are consecutive video tracks adjacent to each other on the tape. Further, the head control direction has two values, for example, above or below with respect to the vertical direction of the video track. Suppose now that the video playback head is displaced in the direction of Dl to play back the video track N-lTh and a playback signal level b1 is obtained. Here, in order to reproduce the video track N, the head control direction Do f is calculated. Since the playback signal level bl was obtained by displacing the video playback head 2iDxO direction with respect to the playback signal level b2 of the N-2 track, the playback signal levels b2 and b□ were compared and their increase/decrease and the direction of DI were determined. From this, the head control direction DO is determined. This truth table is shown in FIG. In FIG. 10, the control direction is assumed to be 1 at the top and 0 at the bottom with respect to the vertical direction of the video track. For example, when b□>b2 and D1=00, that is, video track N
-1 When reproducing section 1e, when the video reproducing head 2 is completely displaced downward and the reproducing signal level increases.

Section 1 of video track N? This means that the video playback head 2t is displaced downward during playback. That is, when the reproduction signal level increases or remains the same, the video reproduction head 2 is displaced in the same direction as the previous time, and when the reproduction signal level decreases, it is displaced in the opposite direction. In this example, the control of the video playback head is divided into t-1 track t-3 and the center 1/3
This is done in the section of . The reason for this is that the most stable reproduction signal is generally obtained at the center of the video track.

The reproduced signal level and head control direction shown in FIG. 9 are stored in the RAM 9 shown in FIG. 7 for one track, and the logic table shown in FIG. 10 is stored in the AMII shown in FIG. The various calculations and controls are performed by the CPU10 shown in FIG.

In the control signal C2, a control voltage obtained by comparing the reproduced signal level at the center of the video track is applied to the entire track. These control signals C1, C2 and C
3 is added by CPU l0 and output to l1012,
The I)/A converter 13 converts the g-bit digital signal into an analog signal, which is amplified by the drive amplifier 14 to obtain a reproduction head drive signal C.

When a general recorded tape is played back by this device, the deviation in shape and amount of bending between the video track at the time of recording and the apparent video track at the time of playback is uniquely determined. Therefore, by manually presetting the data presetting switch group 18 only once, it is possible to correct the tracking error caused by the video track curvature. In this example, a broken line approximation is performed by presetting the correction amplitude to only one value, but it is obvious that the approximation is not limited to this and that a curved line approximation is also possible.

As described above, the present invention provides a sawtooth control signal generated from a tape running speed signal, a control signal for tracking the video playback head to the center of the video track, and a control signal for completely correcting tracking errors caused by video track curvature. By creating a control signal for the video playback signal and mixing these three control signals to create a signal for displacing the video playback head, it is possible to stably maintain the tracking operation even when disturbances occur to the video playback signal, and to maintain the full tracking operation even when the video playback signal is disturbed. This makes it possible to correct tracking errors caused by track curvature, thereby making it possible to perform high-quality slow motion playback.

[Brief explanation of the drawing]

FIG. 1 is a diagram illustrating video tracks on a tape of a helical scanning video tape recorder device in which the present invention is implemented. FIGS. 2A to 39 are diagrams showing the displacement status of the video playback head in the case of special playback. FIG. 3 is a diagram showing the video playback signal level with respect to the relative position of the video playback head and the video track. Figure 4 is a diagram showing the curved shape of a video track. Figure 5 is a diagram showing the tape and video playback head positions of a helical scanning video tape recorder device in which the present invention is implemented. Figure 6 is a diagram showing video playback. A diagram showing the inter-track correlation of signals. FIG. 7 is a block diagram showing the configuration of an embodiment of the present invention. FIG. 8 is a diagram showing the drive signal of the video playback head. FIG. 9 is a diagram showing the drive signal of the video playback head. A diagram explaining the generation. Figure 10 is a diagram showing the control direction of the image reproduction head.

Claims (1)

[Claims] In a helical scan type video tape recorder, a video head attached to a rotating head is used for special playback by displacing all video tracks in a sawtooth waveform in the vertical direction. means for generating a first control signal; means for detecting the running speed and direction of the tape and outputting a detection result; and a sawtooth waveform or an approximate curve thereof having an inclination to compensate for a tracking error according to the detection result. and means for generating a third control signal for displacing the video head in accordance with the amplitude of the reproduced signal from the video track, A special playback device characterized in that a video head is displaced by a signal that is a combination of control signals.