JPH04282981A - Video reproducing device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video reproducing apparatus, and more specifically to a helical scan type video reproducing apparatus.

0002

2. Description of the Related Art Conventionally, in a helical scan type video playback device that records video signals diagonally with respect to the longitudinal direction of a magnetic tape, a rotating magnetic head for video playback is moved in the width direction of the recording track (or in the direction of the magnetic tape). This type is fixed to a rotating drum via an actuator such as a piezoelectric element or bimorph element that can be freely displaced in the longitudinal direction of the recording track, and by driving the actuator, the tracing position of the rotating magnetic head with respect to the recording track can be controlled or finely adjusted. Things were being carried out.

For example, consider a case where slow reproduction at 1/2 speed is performed using a reproduction apparatus in which two magnetic heads having different azimuths are attached to a rotating drum facing each other at 180 degrees. In this case, if we focus on the magnetic head of one azimuth, if the actuator is not driven, the image track of the matching azimuth will be traced, and then the image track of the adjacent another azimuth will be traced. Moreover, at this time, the tracing direction of the head and the longitudinal direction of the track do not match.

Therefore, in the conventional example, the actuator is driven to move the magnetic head in the width direction of the recording track (or in the longitudinal direction of the magnetic tape) so as to trace the same video track of the corresponding azimuth for two consecutive frame periods.
I was trying to shift it to .

Specifically, a pattern generator generates a signal of a desired pattern with a period corresponding to the playback speed, and the output drives the actuator. FIG. 3 shows a recording track pattern by a magnetic head A having a certain (for example, positive) azimuth and a magnetic head B having a different (for example, negative) azimuth. A0, A1, A2, . . . are recording tracks with the same azimuth as the magnetic head A, and B0, B1, B2, .
. is a recording track with the same azimuth as magnetic head B. FIG. 4 shows a waveform diagram of head switching pulses for magnetic heads A and B and drive signals for each actuator of magnetic heads A and B during slow playback at 1/2 speed. Figure 4 (1)
is a head switching pulse, (2) is a drive signal that drives the actuator of magnetic head A, and (3) is a drive signal that drives the actuator of magnetic head B.

By driving the actuator of magnetic head A to displace magnetic head A using a drive signal as shown in FIG. 4(2), magnetic head A moves to the next track after tracing track A0 in FIG. The same track A0 is traced in each frame, and when one frame has passed, track A1 is traced. Similarly, magnetic head B is displaced by driving the actuator of magnetic head B with a drive signal as shown in FIG. Track B0 is traced twice, and track B1 is traced twice in the next two frames. Furthermore, the head tracing direction at this time can be made to precisely match the track longitudinal direction.

As described above, in 1/2 speed reproduction, one track is traced twice in two frames, and the output of the magnetic head is subjected to reproduction video processing and output. Also, 1/n(n
is an integer) When playing at double speed, one track is traced n times in n frames.

[0008]

As described above, in the conventional example, one track is traced n times in n frames during 1/n speed playback. Generally, when playing at a speed less than 1x, each frame is played more than once on average, so
There were the following problems. First, in order to trace the same track n times in n frames, the actuator of the magnetic head must be driven by a considerable amount in each frame, and a drive signal with a complicated waveform must be generated. It won't happen. Moreover, since a large amount of electric power is generally required to drive this actuator, the electric power consumption becomes extremely large. Secondly, it is necessary to widen the displacement range of the magnetic head by the actuator, which requires the use of an expensive and highly functional actuator, and as the displacement width increases, power consumption further increases.

[0009] Accordingly, an object of the present invention is to provide a video reproducing apparatus that solves these problems.

0010

[Means for Solving the Problems] A video playback device according to the present invention is a helical scan type video playback device, which includes:
The magnetic head is attached to a rotating drum via an actuator that can be freely displaced in a predetermined direction. During playback at less than 1x speed, the actuator adjusts the position of the magnetic head to play back the recorded signal, and the reproduced video is stored in the image memory. The present invention is characterized in that an operation of storing the image in the image memory and an operation of outputting the video stored in the image memory as a reproduced video signal with the actuator inactive are performed alternately.

[0011]

[Operation] By using the above means, the position of the magnetic head only needs to be adjusted for the minimum necessary period even in reproduction at a speed less than 1x. That is, the period for adjusting the position of the magnetic head is shortened, and the range of adjustment is small.Thereby, an inexpensive actuator can be used, and power consumption can be minimized.

0012

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 shows a block diagram of an embodiment of the present invention. 10 is a magnetic tape on which a video signal is recorded in a track pattern as shown in FIG. 3, and 12a and 12b are magnetic heads attached to a rotating drum (not shown) facing each other at 180 degrees. The magnetic heads 12a and 12b have different azimuths. 14 is a head changeover switch that selects the output of the magnetic heads 12a and 12b, 16 is an amplifier that amplifies the head output selected by the head changeover switch 14, and 18 is an A/D converter that returns the output of the amplifier 16 to a digital signal. , 20 is a playback processing circuit that performs video playback processing by digital signal processing using the frame memory 22, and 24 is a D/A converter that converts the digital playback video signal output from the playback processing circuit 20 into an analog signal. , 26 are output terminals for reproduced video signals.

Further, 30a and 30b are piezoelectric elements that respectively displace the magnetic heads 12a and 12b in the width direction of the recording track. That is, the magnetic heads 12a, 12b are fixed to a rotating drum (not shown) via piezoelectric elements 30a, 30b. 32 is a piezoelectric element 30a according to the head switching signal HSW and the control signal CTL indicating the playback speed.
, 30b is a pattern generation circuit that generates digital drive signals. The generated digital drive signal waveform is preset or programmed according to the playback speed.

34 and 36 are D/D converters that convert the digital drive signal generated by the pattern generation circuit 32 into an analog signal.
The A converters 38 and 40 are low-pass filters (LPFs) that remove high frequency components from the outputs of the D/A converters 34 and 36.
, 42 and 44 are amplifiers that amplify the outputs of the LPFs 38 and 40 and apply them to the piezoelectric elements 30a and 30b, respectively.

FIG. 2 shows the drive signal waveform and the displacement positions of the magnetic heads 12a and 12b in the case of 1/2 speed reproduction. 2(1) shows the head switching signal, FIG. 2(2) shows the digital drive signal waveform for driving the piezoelectric element 30a of the magnetic head 12a (however, it is shown as an analog waveform for easy understanding), and FIG. 2(3) shows the digital drive signal waveform that drives the piezoelectric element 30a of the magnetic head 12a. is the displacement position of the magnetic head 12a,
(4) shows the digital drive signal waveform that drives the piezoelectric element 30b of the magnetic head 12b (however, it is shown as an analog waveform for easy understanding), and (5) shows the displacement position of the magnetic head 12b. .

That is, the pattern generation circuit 32 generates a digital drive signal (FIG. 2 (2),
(4)) is generated. This digital drive signal is D/A
It is converted into an analog signal by converters 34 and 36, and the LP
The signal is band-limited by F38, 40, amplified by amplifiers 42, 44, and applied to piezoelectric elements 30a, 30b. This causes the magnetic heads 12a and 12b to move as shown in FIG. 2(3).
The magnetic heads 12a, 12b are displaced as shown in (5).
Each traces the target track only once every two frames.

In the reproduction system, the head changeover switch 14 is switched by a head changeover signal, and the heads 12a,
The output of 12b is amplified by amplifier 16, digitized by D/A converter 18, and applied to reproduction processing circuit 20. In the first frame of FIG. 2, the reproduction processing circuit 20
performs normal reproduction processing on the reproduction signals from the magnetic heads 12a and 12b, writes the digital reproduction signals into the frame memory 22, and outputs them to the D/A converter 24. The D/A converter 24 converts the digital signal into an analog signal and outputs it to the output terminal 26.

In the second frame of FIG. 2, the magnetic head 12
a, 12b do not trace the corresponding tracks. The reproduction processing circuit 20 reads the reproduction data of the first frame stored in the frame memory 22 and sends it to the D/A converter 2.
4 and is converted into an analog signal and output to the output terminal 26.

In the above-described embodiment, 1/2 speed playback was taken as an example, but the present invention can also be applied to (n/m) times speed playback (n<m). That is, the same effect can be expected by controlling the actuator during a period of n frames out of m frames, keeping the actuator inactive during the remaining period, and reading out the reproduced video signal from the memory.

Furthermore, in this embodiment, when the actuator is activated, the reproduced video signal is subjected to normal processing and outputted. However, writing to the memory 22 is performed only when the actuator is activated, and the memory 22 is A configuration may also be adopted in which the reproduced video signal is always read from.

Generalizing the above, in the present invention, for playback at less than 1x speed, the actuator is operated to reproduce the video signal recorded on the target track and store it in the memory, and the state in which the video signal is stored in the memory A state in which the stored playback video is read out and output as a playback video signal is alternately repeated. As a result, the position adjustment of the magnetic head only needs to be carried out for the minimum necessary period, and the actuator for the magnetic head only needs to have a small displacement width.

[0023]

As can be easily understood from the above description, according to the present invention, the position adjustment range of the magnetic head can be small for reproduction at less than 1x speed, and the position adjustment period can also be shortened. Therefore, an inexpensive actuator can be used and power consumption can be minimized.

[Brief explanation of the drawing]

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

FIG. 2 is a diagram showing drive waveforms of piezoelectric elements 30a and 30b and displacement positions of magnetic heads 12a and 12b.

FIG. 3 is a general track pattern.

FIG. 4 is a drive waveform diagram of head displacement in a conventional example.

[Explanation of symbols]

10: Magnetic tape 12a, 12b: Magnetic head
14: Head selection switch 16: Amplifier 18: A
/D converter 20: Reproduction processing circuit 22: Frame memory 24: D/A converter 26: Reproduction video signal output terminal 30a, 30b: Piezoelectric element 32: Pattern generation circuit 34, 36: D/A converter 38
, 40: Low-pass filter 42, 44: Amplifier

Claims (1)

[Claims] Claim 1: A helical scan type video playback device, in which a magnetic head is attached to a rotating drum via an actuator that can be freely displaced in a predetermined direction, and when playing at a speed lower than 1x, the magnetic head is moved by the actuator. Adjust the position of the actuator to reproduce the recorded signal, and alternately store the reproduced video in the image memory, and deactivate the actuator and output the video stored in the image memory as the reproduced video signal. A video playback device characterized by: