JPS60249485A - Picture reproducing device - Google Patents

Abstract

PURPOSE:To attain good slow pictures by writing video signals, which are read at every prescribed period, in the first and the second storage means alternately and reading out signals from one of these means while signals are written in the other. CONSTITUTION:When a slow reproducing command switch 264 is operated, a tape running driving circuit 25 sets a slow reproducing mode signal 251 to the high level and gives a reset signal 41 to a timing generator 32. At this time, a reproduced signal is given to head amplifiers 241 and 242, and a dropout is detected by a dropout detector 31 in response to a head switching signal 240. When the timing generator 32 starts the operation, signals are written in the first RAM33 and the second RAM34 alternately in every one field. Reading and writing are performed alternately at intervals of a time corresponding to n-number field periods, thereby attaining slow reproducing in 1/(n+1)-fold speed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a video playback device, and particularly to a video playback device that can provide a good playback screen when performing slow playback.

"Prior art" Video playback for playing back video signals recorded on magnetic recording media such as magnetic tape! ! There is a video tape recorder (hereinafter referred to as VTR). Usually, V
Since the TR is configured to be capable of both recording and reproducing video signals, recording and reproducing of a conventional VTR will be explained below.

FIG. 1 is a diagram showing the video recording section of a conventional VTR.
FIG. 2 is a diagram schematically showing a magnetic tape on which a video signal is recorded by the conventional video recording section shown in FIG. In FIG. 1, the video recording unit 10 includes a head drum 11 rotatably provided at a position where the magnetic tape 1 runs.
Contains.

On the circumference of the head drum 11 are a first head 12 and a second head 1 for recording or reproducing video signals.
3 (1800 in this figure). A magnetic tape 1 wound around a supply reel 14 and a take-up reel 15 is obliquely attached to the head drum 11. A capstan 16 is provided near the winding wheel 15 at a position where the magnetic tape 1 is sandwiched.
and a pinch roller 17 are provided.

By the way, when the VTR is a VH8 system, the length direction of the magnetic tape 1 and the positional relationship with the head drum 11 are different on the right side and the left side, so the video signal recorded on the magnetic tape 1 is The magnetic pattern is as shown in FIG.

The x in FIG. 2 indicates the running direction of the magnetic tape 1,
y indicates the running direction of the head. Also, in the VH8 system,
The first head 12 in FIG. 1 records the recorded A track 2 at an azimuth of 6 degrees, and the second head 13 records the currently recorded 8 track 3 at an azimuth of 16 degrees.

FIG. 3 is a circuit diagram of a conventional VTR. This circuit includes the recording system block 21. Head changeover switch 22, rotary transformer 23. It includes a reproduction system block 24, a tape running drive circuit 25, and a mode selection switch 26. The recording system block 21 is.

Video signal source 211. Luminance signal passing filter 212° Color signal passing filter 213. FM modulator 214° addition circuit 2
15 and a low frequency converter 216. On the other hand, the reproduction system block 24 includes the first and second head amplifiers 241
and 242. Reproduction signal selection switch 243. FMIJ
j image signal passing filter 244, FM demodulator 245. Low-pass color signal passing filter 246. High frequency converter 247. It includes an adder circuit 248 and an output terminal 249. Furthermore, the mode selection switch 26 is a recording command switch 261.
, reproduction command switch 262. stop command switch 263,
It includes a slow play command switch 264 and a pause command switch y-265.

Next, the operation of a conventional VTR will be explained with reference to FIGS. 1, 2, and 3.

First, signal processing in recording mode will be explained.

In the recording mode, the first changeover switch 221 and the second changeover switch 222 included in the head changeover switch 22 are switched to the upper side (the a contact side in FIG. 3). The video signal generated by the video signal source 211 consists of a luminance signal up to about 3MH7 and a chrominance signal of 3.58MH2. The luminance signal passes through a luminance signal passing filter 212 and is provided to an FM converter 214. The FMv modulator 214 modulates the luminance signal from 3.4MH7 to a 4.4MH2 FM signal and supplies it to the adder circuit 215. On the other hand, the color signal passes through a color signal pass filter 213 and is applied to a low-pass converter 216. Low frequency converter 21
6 converts the color signal by 629kl-jz times and supplies it to the addition circuit 275. The adding circuit 215 adds the FM-modulated luminance signal and the low-frequency converted color signal. This addition signal (that is, the frequency-modulated video signal) is given to the head 12 via a first changeover switch 221 included in the head changeover switch 22 and a transformer 231 included in the rotary transformer 23. The signal is applied to the head 13 via the No. 2 changeover switch 222 and the transformer 232. The head 12 records the modulated video signal (luminance signal and color signal) on the A track.

The head 13 records the modulated video signal ('R degree open signal and color signal @) on 8 tracks.

Next, signal processing in playback mode will be explained.

In this case, the reproduction command switch 262 is pressed. In response to this, the tape running drive circuit 25 operates the first changeover switch 221. included in the head changeover switch 22.
Then, the second changeover switch 222 is switched to the lower side (b contact side) to switch to the reproduction system. In this state, the recording signal (that is, the video signal) recorded on the A track 2 of the magnetic tape 1 is selected by the azimuth, is reproduced by the first head 12, and is transferred to the first head via the transformer 231 and switch 221. The signal is applied to the head amplifier 241. The first head amplifier 241 amplifies the reproduction signal and supplies it to the reproduction signal changeover switch 243. Similarly, the recording signal (
That is, the video signal) is reproduced by the second head 13 and provided to the second head amplifier 242 via the transformer 232 and switch 222. The second head amplifier 242 amplifies the playback signal and outputs it to the playback signal selection switch 24.
Give to 3. The playback signal changeover switch 243 transfers each output signal of the A track 2 and B track 3 to the head drum 1.
1 (FIG. 1) and applied to the FM video signal passing filter 244 and the low frequency color signal passing filter 246. The FM video signal passing filter 244 passes the FM video signal of the frequency band modulated by the 1M modulator 214 and supplies it to the FM @ modulator 245 .

The FM demodulator 245 derives a luminance signal from the F~1 video signal and supplies it to the adder circuit 248.

On the other hand, the low-pass color signal passing filter 246 is connected to the low-pass converter 2
The low frequency color signal converted in step 16 is passed through and applied to the high frequency converter 247. The high frequency converter 247 converts the low frequency color signal into a 3.58MH2 color signal,
Give to 48. Adding circuit 248 adds the demodulated luminance signal and color signal and outputs the result to output terminal 249 as a video signal.

Next, slow playback will be explained. Slow playback is performed based on the operation of the slow playback command switch 264, and one method for performing slow playback without noise at t7 in a VH8 system VTR is as follows.

That is, in slow playback, the j-jump is driven intermittently by repeating running and stopping, and in still playback, the above-mentioned intermittent drive is performed once or several times and then stopped.This method In this method, the positional relationship between the recording track and the rotating magnetic head when the tape is stopped must be within a range that does not interfere with noise on the playback screen.For this reason, with this method,
The control signal played while the tape is running is used as track position information, and by controlling the amount of tape travel after the control signal is detected, the tape is stopped at a position where no noise appears on the screen. There is.

Such a conventional control method is shown in FIG. 4, which shows the torque applied to the capstan motor, the tape speed, and the control signal. The tape is accelerated from time to to 11, and then runs at a constant speed. When a control signal is detected at time 12, braking is started after a delay time (t s - t 2 >), and at time 1, when the tape speed is approximately O, braking is terminated and the tape stops. Here, ( 1, -12) is called the tracking delay time, and increasing or decreasing this time increases or decreases the amount of tape feed.In conventional VTRs,
This tracking delay time can be adjusted by the user using a variable resistor so that the playback screen can be set at the best position, that is, at the optimum tape stop position.

In this way, in slow playback on conventional VTRs, the user must adjust the tracking delay time, that is, the optimal depth feed amount, each time, and the capstan must be intermittently driven.
A large capstan motor with a starting power of 1-lux was required for the tr. Furthermore, a complicated drive control circuit is required to perform the above-mentioned control operations. moreover,
Since the relative position 324 between the video tape and the video head changes between when the video tape is stopped and when the video head is running, the reproduction horizontal frequency changes, which has the disadvantage of requiring a special correction circuit.

SUMMARY OF THE INVENTION This invention has been made to eliminate the drawbacks of such conventional devices, and it uses a capstan motor with a variable resistor and a large starting torque to adjust the optimal tape feed amount.
In addition, we provide video playback a& that allows you to obtain good slow speed and screen quality without using a highly accurate drive control circuit.
The purpose is to

In summary, the present invention is such that the signals read at predetermined intervals are alternately written into the first and second storage means, and when -10,000 is being written, k is read from Hakata. By constructing #I, the video playback device is capable of performing good slow playback.

[Embodiments of the Invention] The details of the present invention will be made clear through a detailed explanation of the present invention.

FIG. 5 is a block diagram schematically showing the circuit configuration of a VTR which is one practical example of the present invention.

In the circuit of FIG. 5, duplicate explanations of parts similar to those of the circuit of FIG. 3 will be omitted, and the description will focus on parts unique to the circuit of FIG. 5. Differences in the groove bottoms of these two circuits exist in the following ① to ②.

■ In the circuit shown in FIG. 3, the head switch signal 240 is directly given to the playback signal changeover switch 243, but in the circuit shown in FIG. @251
This OR
The output of the circuit 250 is given to the playback signal changeover switch 243 (therefore, the playback signal changeover switch 243 is controlled 1liIJ).This slow playback mode signal 251 is of negative logic and is in slow playback mode. During this period, it remains active unless another mode command is input.

(2) The output of one of the first and second head amplifiers 241 and 242 (second head amplifier 242 in FIG. 5) is also provided to the dropout detector 31.

This dropout detector 31 is activated by a head switch signal 240 and performs dropout detection based on the output of this second head amplifier 242 only when the second head 13 scans the videotape. .

The tape running drive circuit 25 is connected to this dropout detector 3.
Based on the signal from 1, a command is sent to the capstan 76 (FIG. 1) to stop the videotape after slightly moving the tape to a position where there is no dropout.

■ In the circuit shown in FIG. 3, the output of the reproduction system block 24 is given as is to the output terminal 249, but in the circuit shown in FIG. given to the circuit. The outputs of these two RAMs 33 and 34 are added by an adder circuit 270 and then applied to an output terminal 249.

(2) The circuit shown in FIG. 5 includes a timing generator 32, which operates based on the operation of the slow play command switch 264 and the reset signal 41 from the tape running drive circuit 25. timing generator 3
Of the outputs of 2, control signals 42 and 43 are given to the first and second RAMs 33 and 34, respectively, and cause one field's worth of reproduced composite video signal to be written alternately into these two RAMs. This is a control signal for On the other hand, III
Similarly, the Jm signal 44.45 is sent to the first and second (7) RAMs.
33 and 34 respectively, and these two R
This is a 1IiIItIIJ signal for alternately reading out one field's worth of reproduced composite video signals from AM.

Further, a control signal 46, which is another output of the timing generator 32, is given to a tape running drive circuit M25, and this tape running drive circuit 25 responds to this control signal 46 to feed the tape by a desired amount. Generates a signal to

Next, the operation of the circuit shown in FIG. 5 will be explained with reference to the timing diagram shown in FIG. In FIG. 6, each control signal represents positive logic.

The feature of this circuit is in the slow playback operation, and the recording operation is the same as the conventional one, so only the playback operation will be explained. First, by operating the slow playback command switch 264, a slow playback command signal is generated. As a result, the tape running drive circuit 25 sets the slow playback mode signal @251 to the "H" level and provides the reset signal 41 to the timing generator 32.At this time, the switches 221 and 222 are set on the playback side (11
), and the reproduction signal is given to the first and second head amplifiers 241 and 242. As mentioned above, in the slow playback mode, the Z-playback mode signal 251
is activated and therefore the head switch signal 2
40, the second head amplifier 242
The dropout detector 31 inputs the output signal of
Perform dropout detection. Based on the output of the dropout detector 31, the tape running drive circuit 25 moves the videotape slightly until there are no dropouts, and the optimum position I! to obtain one field's worth of still surface I! When it comes to relationships, the videotape is stopped.

When this stop occurs, the reset signal 41 becomes II L
II, and the timing generator 32 starts operating.

After the timing generator 32 receives the reset signal 41,
One of the control signals 42 and 43 is sent to the first RAM 3.
3 or the second RAM 34, and the reproduced composite video signal for one field in the above-mentioned stopped state is input to the selected R.
Write to AM. In the timing diagram of FIG. 86, the first RAM 33 is selected as the RAM to be written first. At the start of the write operation, the control signal 45 is activated, and the contents recorded in the second RAM 34 are read an arbitrary number of times and outputted to the output terminal 249 through the processing circuit 270. After writing to the first RAM 42 is completed, the tape running drive circuit 25 moves the video tape by a desired amount in response to a control signal 46, and then stops it again. Here, the second RAM 34 is selected and the first
After writing into the second RAM 33, the reproduced composite video signal for the next one field is written into the second RAM 34 at an interval of n fields (n is an integer). At this time, the reproduced composite video signal stored in the first RAM 33 is read an arbitrary number of times and added times!
! It is output to the output terminal 249 via 8270. In this way, by alternately selecting the first and second RAMs 33 and 34 at intervals of time R corresponding to n field periods and alternately performing writing and reading, 1/<n-
1-1) Double speed slow playback can be obtained.

Although a VTR was considered in the above embodiment, the present invention can be applied to other video playback devices, and the present invention can be applied to both playback-only devices and devices capable of recording and playback. Applicable.

[Effects of the Invention] As explained above, the video playback device of the present invention does not require a variable resistor for adjusting the optimum tape feed amount, a capstan motor with a large starting torque,
Furthermore, it is possible to provide a video playback device that can provide a good slow playback screen without using a highly accurate drive control circuit, and also allows the slow playback speed to be arbitrarily set.

In addition, since the video signals are alternately stored and output by the first and second storage means, the signal read from either one of the storage means is always observed on the playback screen, and the signal read from one of the storage means is always observed. Another advantage is that there is no need to perform complicated timing settings for switching between the reproduced video actual signal and the subsequent signal from the storage means, unlike when only one is used.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a video recording section of a conventional VTR. Figure 2 shows the rk! tape on a VTR! FIG. 3 is a pattern diagram showing a recording pattern. FIG. 3 is a circuit diagram of a conventional VTR. FIG. 4 is a diagram showing a method of controlling slow playback operation in a conventional VTR. FIG. 5 is a circuit diagram showing a VTR circuit according to an embodiment of the present invention. FIG. 6 is a timing diagram for explaining the operation of the VTR shown in FIG. 5. In the figure, 1 is a magnetic tape, 10 is a video recording section, and 21 is a magnetic tape.
24 is a recording system block, 24 is a reproduction system block L cock, 25 is an Arp travel drive circuit, 31 is a dropout detector, 32
3 is a timing light generator, 33 is a first RAM, and 34 is a second RAM. Note that the same reference numerals in the figures or lc indicate corresponding parts. Agent Person Person Arrival Increase Yuushin 2 Figure 64 Figure 1° (+Uz C” ″ -Ginhou Gyo 3 Figure-21

Claims (3)

[Claims] (1) A video playback device for playing back a video signal recorded on a recording medium, comprising: video signal reading means for reading the video signal from the recording medium; and video signal reading means for driving the recording medium. a first drive means for moving the video signal relative to the video signal reading means;
and a second storage means, and a timing signal generation means for generating a timing signal according to a predetermined cycle, and the drive means moves the recording medium in response to a first output of the timing signal generation means. The operation of starting and then stopping is repeated in the period, and the first and second storage means are read by the video signal reading means at each period in response to the second output of the timing signal generation means. a video reproducing device which alternately writes the video signals written in the first and second storage means, and when the writing is performed in one of the first and second storage means, the other one outputs the video signal written therein; . (2) The video reproducing apparatus according to claim 1, wherein video signals for each field are sequentially recorded on the recording medium, and the period is a recording interval of n fields (n - an integer). (3) The recording medium has an array of a plurality of tracks on which video signals are sequentially recorded, and the ll! The 12-image reproduction device further includes dropout detection means for detecting a dropout in the reading based on the video signal read by the video signal reading means, and the drive means, when stopping the recording medium, Claim 1 or 2, wherein the recording medium is slightly moved in response to the output of the dropout detection means until the relative positional relationship between the video signal reading means and the track reaches a predetermined relationship. Video playback device as described @.