JPS63167585A - Helical scanning system video tape recorder - Google Patents

Abstract

PURPOSE:To obtain the picture quality the same as that at normal reproduction by writing a reproduced video signal to one memory at reverse reproduction and reading the stored data from the other memory and switching the operation at each field. CONSTITUTION:Depressing a reverse reproducing button from the stop state, a video signal changeover switch 21 is thrown to the position of an output terminal B by a video signal switching signal 22 and a reproduced video signal 32 reversed timewise from the output terminal B is converted into a digital signal by an A/D converter 23. Input and output control signals 35-38 are generated synchronously with a vertical synchronizing signal 34. When the input control signal 35 of a 2nd memory 25 is logical H, the output from the A/D converter 23 is written in the 2nd memory 25, and the output control signal 38 of the 1st memory 24 with H level and the already written data is read reversely timewise. In repeating the operation for each vertical synchronizing signal 34, the vertically correct pattern similar to the normal reproduction picture is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a helical scanning video tape recorder.

[Prior Art] FIG. 8 is a schematic diagram of a drive system in a conventional helical scanning video tape recorder.

In the figure, (1) is a magnetic tape, (2), (
3) is the video head, (0 is the video head (2),
(3) is the attached drum, (50) is the drum (
4) is a drum motor that rotates, (6) is a magnetic tape (
1) a capstan shaft for sending, (70) a capstan motor that rotates the capstan shaft (6), (8) a pinch roller that presses the magnetic tape (1) onto the capstan shaft (6), It rotates in the opposite direction to the rotation of the capstan shaft (6), and feeds the magnetic tape (1) together with the capstan shaft (6).

FIG. 9 shows @ traces of the video head during reverse playback of the video head in the video tape recorder, (9) is the audio track, (11) is the controller track,
(12) is a reverse reproduction section.

Next, the operation will be explained.

During normal playback, the drum motor (50) rotates to the left, and the drum (4) and video head (2) move in conjunction with it.

(3) also rotates to the left. In addition, a capstan motor (70
) rotates clockwise, and the interlocking capstan shaft (6) also rotates clockwise. Since the pinch roller (8) is pressed onto the capstan shaft (6) through the magnetic tape (1), it rotates to the left, which is opposite to the capstan shaft (8), and therefore the magnetic tape (1) rotates to the right. sent in the direction. On the contrary,
During reverse playback, the drum motor (50) rotates to the left as in normal playback, but the capstan motor (70) rotates to the left, the capstan shaft (6) also rotates to the left, and the pinch roller (8) rotates to the left. rotates clockwise, and the magnetic tape (1) is sent to the left, which is opposite to normal playback.

[Problems to be Solved by the Invention] The operation of the conventional helical scanning video tape recorder is as described above.
, (3) traces the trajectory shown in Figure 9, and since the tape running direction is opposite to that during normal playback, only the portion of the reverse playback section (12) shown with diagonal lines is played back, and compared to normal playback, the S/ N
deterioration, causing color shift and noise generation.

This invention was made in order to solve the above-mentioned problems, and it is an object of the present invention to provide a helical scanning video tape recorder that does not cause a drop in playback level compared to normal playback and can provide image quality equivalent to normal playback. The purpose is to

[Means for Solving the Problems] The reverse playback helical scanning video tape recorder according to the present invention rotates both the drum motor and the capstan motor in the opposite direction to the normal playback, and the reverse playback A memory timing control circuit controls the memory timing control circuit so that the playback video signal is written into one memory and at the same time the stored data is read out from the other memory in the opposite direction to the writing. This is what I did.

[Function] In this invention, by rotating the drum motor and the capstan motor in reverse during reverse playback, the image of the playback video signal before entering the first and second memories is the same as the playback video signal during normal playback. Although the video is upside down, by reading the video from the memory in reverse in time, it is converted into a regular video with a signal at the same level as the reproduced video signal during normal playback.

[Embodiments of the invention] Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic diagram showing the drive system of a reverse playback helical scanning video tape recorder according to the present invention, and the same parts as in the conventional one are given the same reference numerals and the explanation thereof will be omitted.

In the figure, (5) is a drum motor, which is set to rotate counterclockwise during normal playback and clockwise during reverse playback. (7) is a capstan motor, which is set to rotate clockwise during normal playback and counterclockwise during reverse playback.

Figure 2 shows the video head (2) during normal playback.

It shows the trajectory of (3), where (9) is an audio track, (10) is a video track, and (11) is a control track.

FIG. 3 is a block diagram showing the circuit configuration of the main parts of the video tape recorder of the present invention. In the same figure, (
21) is a changeover switch to which the playback video signal is input, and when it is switched to the output terminal A in a state other than reverse playback and the reverse playback button (not shown) is pressed, the switch signal (21) is input.
2) to switch to output terminal B. (
23) is an A/D converter connected to the output terminal B of the changeover switch (21), and (24) and (25) are first and second converters that store digital signals from the A/D converter (23). , (2B) is the memory (24) above,
This is a D/A converter that converts the output from (25) into an analog signal.

, (27) is the output terminal B of the changeover switch (21).
A sync separation circuit (28) is a memory timing control circuit which is connected to a sync separator circuit that separates a vertical sync signal from a reproduced video signal. Store the signal above in memory (24)
, (25) controls the timing required for writing and reading. When the input control signal (35) from this memory timing control circuit (28) is "H" on the second memory (25) side (the input control signal (37) of the first memory (24) is When the output control signal (3 days) is, for example, H” on the first memory (24) side (the second memory (25) ) is set so that the output control signal (3B) is +L''), data already stored in the memory (24) is read out, and these operations are switched for each field.

Next, we will explain the operation of the above configuration. 6 During normal playback, the video heads (2) and (3) move the video tracks (10) in the order of numbers 1.2...n-1 and n shown in FIG. At the output terminal A of the trace changeover switch (21), a normal playback video signal (31) as shown in FIG. 4 is output.

When the reverse playback button is pressed from a stopped state, the drum motor (5) rotates clockwise, the capstan motor (7) rotates counterclockwise, and the magnetic tape (1) is fed leftward. Also, if you press the reverse play button from normal play mode, the drum motor (
5) reverses from left rotation to right rotation, and the capstan motor (7) reverses from right rotation to left rotation. Video head (2) during these reverse playbacks.

The trajectory of (3) is alternately reversed (from the audio track (9) to the control track) in the order of (a), (b), (c), and (d) in Fig. (11)), the output terminal B of the selector switch (21) can obtain a signal (32) (FIG. 4) at the same level as normal playback. As is clear from Figure 4, the video signal (32) during reverse playback is temporally reversed, so when this reproduced video signal (32) is projected on the screen P, it looks like the one shown in Figure 6. It turns upside down. This temporally reversed video signal (32) is stored in the memories (24) and (25) in Figure 3.
After that, it will return to normal.

That is, when the reverse playback button is pressed, the video signal changeover switch (21) is switched to the output terminal B side by the video signal changeover signal (22), and the temporally reversed playback video signal (32) is output from the output terminal B. is A/D converter (23)
The signal is converted into a digital signal.

On the other hand, the reproduced video signal (32) is transmitted to the synchronization separation circuit (2).
7), only the vertical synchronization signal (34) (Fig. 5) is taken out and enters the memory timing control circuit (2B).
Input and output control signals (35) to (38) for the timing necessary to write and read digital signals from the A/D converter (23) into the first and second memories (24) and (25). (Figure 5) is generated.

The timing of the input and output control signals (35) to (38) will be explained with reference to the timing chart of FIG.

First, the input and output control signals (35)-(38) are generated in synchronization with the vertical synchronization signal (34). When the input control signal (35) of the second memory (25) is, for example, H'', the output from the A/D converter (23) is
5), at the same time, the output control signal (38) of the first memory (24) is, for example, "H", and reads out the data that has already been written in the reverse direction in time from when it was input. At this time, the output control signal (38) of the second memory (25) is "L", so no reading is performed, and the input control signal (37) of the first memory (24) is also "L", so no writing is performed. All operations take place within time a.

At the next vertical synchronization signal (34), the second memory (25)
The input control signal (35) becomes L'', writing is stopped, and at the same time the output control signal (36) becomes 1H'', reading begins, and the data written one field ago is temporally changed. The first memory (which is read from the reverse)
24) input control signal (37) becomes 'H' and the A/D
At the same time as writing the output digital signal from the converter (23), the output control signal (38) is low, so reading is stopped. All these operations are performed within a time interval.

The same operation as in time a is performed at time C with the next vertical synchronization signal (34). By repeating these operations, the output (33) from the D/A converter (26) (Fig. 4) becomes temporally opposite to the signal before passing through the A/D converter (23). signal, video head (2),
(3) controls the video track (10) (1
When tracing from 1) to audio track (9), the upper and lower correct screen P (Fig. 7) is obtained, just like the normal playback image, so it is equivalent to normal playback without S/N deterioration, color shift, and noise. You can obtain continuous reverse playback image quality.

Note that the above configuration has input and output control signals (3
By changing the timing of steps 5) to (38), it can be applied to reverse frame-by-frame forwarding, playback from memory, and reverse playback of still images, and can also be applied to current VH5 and Beta home video formats. Of course, it can be applied to other helical scanning formats as well.

[Effects of the Invention] As described above, according to the present invention, the drum motor and the capstan motor are rotated in reverse during reverse playback, and at the same time, the playback video signal is written to one memory while the other memory has already written it. By reading data in the reverse direction in time from when it is written, and switching this alternately for each field, S/N deterioration, color shift, noise, etc. are suppressed, and image quality equivalent to that of normal playback is obtained. be able to.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of the drive unit of a helical scanning video tape recorder according to an embodiment of the present invention, FIG. 2 is a diagram showing the trajectory of the video head in the same video tape recorder, and FIG. 3 is a diagram showing the trajectory of the video head in the same video tape recorder. A block diagram showing the circuit configuration of the main parts of the recorder, Fig. 4 is an explanatory diagram for comparing signals during reverse playback in the same video tape recorder with signals during normal playback, and Fig. 5 shows the memory in the same video tape recorder. Timing chart of input and output control signals, Figure 6 is a screen showing signals before they are written to memory during reverse playback, and Figure 7 is a screen showing signals read from memory during reverse playback. FIG. 8 is a schematic diagram of the drive section of a conventional helical scanning video tape recorder, and FIG. 9 is a diagram showing the trajectory of the video head during reverse playback of the conventional video tape recorder. (1)...magnetic tape, (5)...drum motor,
(7)...capstan motor, (24)...first
memory, (25)...second memory, (28)...
...Memory timing control circuit. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] (1) A drum motor that can rotate the video head in forward and reverse directions, a capstan motor that can run the magnetic tape in both forward and reverse directions, and both the drum motor and capstan motor that rotate in reverse during reverse playback. first and second memories for storing the reproduced video signal obtained by the reverse reproduction, and at the same time writing the reproduced video signal during reverse reproduction into one memory, the data already written from the other memory is written. What is claimed is: 1. A helical scanning type video tape recorder comprising: a memory timing control circuit that performs reading in the opposite direction in time, and controls the operation so that this operation is alternately switched for each field.