JPS62154887A - Video recording and reproducing device - Google Patents

Abstract

PURPOSE:To attain a rapid reproducing minimizing a noise bar and improving its quality by detecting recording track width on a tape from the envelope signal of a reproducing signal and supplying an optimum comparing potential level to a comparator to automatically adjust a writing range in a memory. CONSTITUTION:Different track width values recorded on a magnetic tape are respectively detected by an envelope detecting signal and an optimum potential as an comparing potential to a comparator is switched within a field and supplied to the comparator based on the detected result. Namely, a table determining the optimum reference voltage to the comparator 6 is referred based on the time of level 'L' obtained over a two-field period to determine the optimum potential levels corresponding to respective track width and potential levels corresponding to S1 and S2. The table is previously written in the program memory 22 of a microcomputer 20 and switched by a microcomputer 20 so that the comparing potential of the comparator 6 is S2 in the periods N1, N3, N5 and the comparing potential is S1 in the periods N2, N4.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a video recording and reproducing device, and in particular, to a video recording and reproducing device that uses field memory to obtain high-quality reproduced images with reduced noise and noise during high-speed reproduction. It is.

(Prior Art) As a conventional example, we will explain the case where high-speed playback of a video tape recorder (hereinafter referred to as VTR) using field memory is performed at an even number multiple of 4 times. Here, in general, high-speed playback is performed at an odd number multiple of speed. This takes advantage of the property that the noise bar locks because the noise position is the same for each field.On the other hand, at even multiple speeds, the noise position and the signal position alternate for each field, By utilizing this property and using memory, it is possible to narrow the noise par in some cases.

FIG. 4 shows the high-speed playback system of the conventional VTR. In the figure, 1 is a recorded video tape, and the playback signal is guided to a preamplifier 3 via video heads 2a and 2b.
Thereafter, the reproduced signal is sent to the video signal processing circuit 4.

On the other hand, 5 is an envelope detector that extracts the envelope of the reproduced signal from the output of the preamplifier 3, and its output is led to a comparator 6 that compares it with a certain level, and is sent to the video signal processing circuit 4 to the field memory 8.
The output signal is sent to the memory control circuit 7 which generates the write timing and address of the output signal. Also,
A synchronizing signal is sent from the video signal processing circuit 4 to the memory control circuit 7.

The field memory 8 is a dual port memory (not shown) and has a random output and a serial output as an output port, and if the serial port is used, writing and reading from the memory can be performed asynchronously. The operation here is an asynchronous operation in which the contents of the field memory 8 are read out using a serial port while writing the reproduced signal from the video signal processing circuit 4 into the field memory 8.

On the other hand, 9 is a control head, and based on this output, the servo circuit 10 controls the capstan motor 11 .
The reel motor 12 is controlled to control tape running in each mode.

Next, the operation will be explained. Here, since special playback (high speed playback, slow playback, and still image playback) is emphasized, video tapes recorded on VTRs having different video head widths will be taken as an example.

Suppose that videotape 1 is being played back at 4x speed in the reverse direction. FIGS. 5 and 6 are diagrams for explaining the operation at this time. In FIG. 5, 50 is a video track recorded on a magnetic tape, and when adjacent tracks A and B have different track widths, that is, (track width of A)>(track width of B). It shows. In addition, A and B represent azimuth recording, and for 8, the video head 2a is turned to the video head 2a, and for B, the video head 2a is turned to the video head 2a.
b have the same azimuth.

Now, when the video head 2a traces the broken line 51 in the figure, the output of the envelope waveform 5 of the reproduced signal becomes <81 in FIG. 6 due to azimuth recording. Similarly, when the throat 2b traces the trajectory of the broken line 52 in the figure, the output shown in FIG. 6(b) is obtained. These Figure 6(a),
When the contents of the two fields in (b) are interpolated with each other on the time axis, one field image as shown in FIG. 6(c) is obtained, which is stored in the field memory 8 and displayed on the monitor. Here, Fig. 6 (al, (bl,
(The envelope waveform indicated by cl represents only the upper side of the vertically symmetrical AC waveform.

By the way, when writing the image interpolated on the time axis shown in FIG. 6(C) to the field memory 8, the comparator 6
However, as shown in Figure 5, if the 1-rack widths of A and B are different, if the comparison potential of A problem occurs. That is, in FIG. 6 (C1, comparator 6
For example, if the comparison potential of N is set to a constant value S1, then N
2. The N4 part is interpolated smoothly and the screens are connected, but the Nl part.

N3. Since there is no reproduction signal in the N5 part, a noise bar appears on the screen. Also, when the comparison potential is set to 82, the N H, N3, and N5 parts are connected smoothly, but this time, the N2. In the N4 part, the contents are rewritten every time for each field, so that part looks blurry on the screen, and noise appears at both ends of the part.In any case, the interpolated image is not smooth. I can't get a good quality connected screen.

[Problem that the invention seeks to solve]

As described above, in the method of obtaining signal information by interpolating the contents of each field by performing high-speed playback of a magnetic tape whose recording track width is not the same on a VTR using field memory at an even multiple speed, If the comparison potential of the comparator 6 is set to a constant value, it is impossible to obtain an image with less noise and blur during high-speed reproduction.

The present invention provides video recording and playback that can obtain high-quality images with minimal noise bars and blurring of playback signals from field memory during high-speed playback even when the widths of tracks recorded on a magnetic tape are not the same. It provides equipment.

[Means for solving problems]

The video recording and reproducing apparatus according to the present invention uses a microcomputer or the like to detect different track widths recorded on a magnetic tape from envelope detection signals, and based on the detection results, outputs a comparison potential to a comparator.
The optimum potential is switched and supplied within one field.

[Effect]

In the present invention, each 1-rank width recorded on the magnetic tape is automatically detected by a microcomputer, etc., and the potential supplied to the comparator is adjusted accordingly to minimize noise and blur on the screen. This allows you to obtain high-quality images during high-speed playback.

〔Example〕

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

In FIG. 1, 20 is a one-chip microcomputer (hereinafter simply referred to as a microcomputer), which receives the synchronizing signal from the video signal processing circuit 4 and the output from the comparator 6, and controls the optimum potential to the comparator 6. /
Input/output circuit 2 that outputs via the A converter 30
1. Data memory 23 for temporarily storing data. Timer 24 having a timer function and timer memory. A microprocessor 25 that performs calculations. and a program memory 22 that controls operations. The microcomputer 20 and the comparator 6 serve as means for detecting the recording track width on the magnetic tape 1.
The A converter 30 constitutes level setting means for setting the level of the comparison voltage supplied to the comparator L/-6. The rest of the structure is similar to the conventional structure, and the same reference numerals as in FIG. 4 represent the same components.

Next, the operation will be explained.

Now, assume that the video heads 2a and 2b reproduce the trajectories 51 and 52 of the video track 50 in FIG. 5 on the magnetic tape 1 at 4x speed in the reverse direction. The reproduced envelope obtained at this time is shown in FIG. The maximum potential is almost determined by the preamplifier 3, and the potential of 415 is known in advance.At this time, the output from the comparator 6 for two field periods is
The result is as shown in Figures (ag and (b)).In addition, in Figure 2,
A potential of 415 or higher is expressed as a level "L".

Here, the time T1 to T10 during which the logic level is inverted is measured. And the time it falls to level “L” (T3-
T2. T5-T4. T7-T6. Tg・-T8)
By measuring , it is possible to know what track width the signals are recorded on the magnetic tape 1. This is the level
This is because there is a relationship that the track width is narrower as the time of "L" increases by %fi.Also, the reason why the time is measured over two fields is because each field may be recorded with a different head width. From the time of the level "L" obtained over two fields in the above manner, the optimum reference voltage to the comparator 6 is determined based on the assumption that recording has already been performed with various track widths. With reference to FIG. 6, the optimum potential corresponding to each 1-rank width, that is, the potential corresponding to S1 and N2 in FIG. 6 trot is determined.

The above table is the program memory 22 in the microcomputer 20.
It is written in advance. Then, in order to obtain an image in which noise bars and blur are minimized, periods Nl, N3. N
In N2.5, the comparison potential of the comparator is 82. At N4, the microcomputer 20 switches the comparison potential to Sl. In other words, Figure 2 (C)
As shown in 'r6. T2. T9. T4. At time T10, the comparison potential is alternately switched between Sl and s2. The output of the comparator 6 obtained in this way is shown in FIG. 2(d). Here, the logic level of di (in FIG. 2) is simply the read mode (
level "H") and glance mode (level "L").

Note that the write and read modes here are for the random input and random output ports of the dual port memory used in the previously explained Finilt memory 8, and in the read mode, the memory contents are This means that it is not something that is read and output, but rather that it is not written to memory.

That is, it is assumed that the output of the memory contents as the original read mode is performed using a serial port, and that the operation is asynchronous with random input.

By supplying the comparison potential in this way, a reproduced signal in which envelopes interpolated for each field are smoothly connected is written into the field memory 8, and a high-quality reproduced image with minimal noise bars and blurring can be obtained.

The above will be explained with reference to the flowchart shown in FIG. Here, the vertical synchronization signal is used as a reference as the time axis, and the vertical blanking interval 1tJj is set to the level "L".

In FIG. 3, first, address 0 of the data memory 23 is initialized and set to "1" (step 100). Next, in order to supply the maximum potential 415 of the envelope detection signal to the comparator 6, data corresponding to the potential is outputted to the D/A converter 30 via the input/output circuit 21 (step 101). Then, the rise of the vertical synchronization signal from the video signal processing circuit 4 is detected (steer knob 102)
do. Next, if the content of address 0 is "1", the timer 2 does not start until the output logic of the comparator 6 becomes level "L".
4, and if it is "6", the timer 24 is started regardless of the output logic (steps 103 and 10).
4.105). This is to distinguish between (al and (bl) in FIG. 6, and to perform the following operations starting from the case of (al).

When the output of the comparator 6 is inverted after the timer 24 starts, the value of the timer 24 at that time is first recorded at address 1 of the data memory 23 (step 106.
l07). Then rlJ to the contents of memory address 0.
is added to make "2" (step 108). Then, the process returns to step 106 and performs the same operation, and records the time from when the timer 24 starts until the output logic of the comparator 6 is inverted at addresses 1 to 5, ↑, a. Then add “1” to the contents of address 0 (step 108) and r6
If it is J, return to step 102 (ste knob 10
9) For the second field, perform the same operation as for the first field, and store the time in addresses 6 to 10, and when the content of address 0 becomes "11", store it in addresses 1 to 10. Based on T1 to 'T''10, St, S
2 is determined (step 110, 1lla).

Next, the contents of address 6 are exchanged with address 1, the contents of address 8 are exchanged with address 2, and the contents of address 10 are exchanged with address 5 (step 11 l b). The dirt should be removed at 'F6°T2. T8. T
4. This is a front 4P provision for alternately switching the comparison potential at the time of TIO. When the rising edge of vertical synchronization is detected (step 112), the potential corresponding to S2 is first output from the microcomputer 20 through the D/A converter 30 as the comparison potential of the comparator 6 (step 1
13).

Then, the timer 24 is reset and started (step 114), and rlJ is placed in address 0 to initialize it (step 115). Then, the comparison potential is switched from 81 to 82 during the IR when the value of the timer 24 is equal to or exceeds the value of T6 entered at address 1 (step 116).
, 117). Then add “1” to the contents of address 0 and add “2” to the contents of address 0.
”, and this time, the moment the value of timer 24 exceeds the value of T2 stored in address 2, the comparison potential is changed from 82 to 81.
(steps 118, 120, 121). Similarly, at the moment when the value of the timer 24 exceeds the value of T13, T4, and T10 stored in addresses 3 to 5, Sl and 82 are alternately switched.

When the content of address 0 becomes "6" in step 119, the process moves on to step 124, where it becomes 1 of 2 feel toro. The second field has almost the same f, 1> as the first field, but the Fieldro initially sets the comparison potential of the comparator 6 to S2, but in the second field, it detects the rising edge of the vertical synchronizing signal (step 12
4) Then, first set 81 as the comparison potential and step 12
5), Reset the timer 24 and start it. Step 126). Put "1" in address 0 and initialize it. Go to step 120. After that, perform the same operations as in the first field described above. Once the 2nd field toro operation is completed, the same operation as in the 1st field is repeated.

In this embodiment, the recording track width is detected from the envelope detection signal, and the comparison potential of the comparator 6 is determined accordingly to adjust the writing range to the memory. Even with tapes recorded with , the width of the noise bar can always be minimized without manual adjustment, resulting in high-quality playback video.

In addition, although the case of 4x speed playback was explained as high-speed playback in the embodiment, the present invention is not limited to this 4x speed, and can be applied to any high-speed playback as long as it is an even numbered speed.
The same effects as in the above embodiment can be obtained.

Further, although a microcomputer is used in the above embodiment, each control means may be configured by hardware, and the same effects as in the above embodiment can be obtained.

Furthermore, although the field memory used here is a dual-port memory (or multi-port memory), it may also be a general-purpose memory.

〔Effect of the invention〕

As described above, according to the present invention, the recording track width on the tape is detected from the envelope signal of the reproduced signal, and the optimal comparison potential is supplied to the comparator based on the detected content, and the writing range to the memory is automatically determined. Since the adjustment is made, it is possible to perform high-speed playback with good quality and minimum noise parity, regardless of the recording track width of the tape.

[Brief explanation of drawings]

FIG. 1 is a block configuration diagram of a video recording and reproducing apparatus according to an embodiment of the present invention, FIG. 2 is a signal waveform diagram for explaining the operation of the apparatus, and FIG. 3 is a diagram for explaining the operation of the apparatus. Flowchart diagram; Figure 4 is a block diagram of a conventional video recording and reproducing device; Figure 5 is a diagram showing the head trajectory when a video track recorded on a magnetic tape is played back at high speed; Figure 6 is a diagram showing the head trajectory when playing back a video track recorded on a magnetic tape at high speed. FIG. 3 is a diagram showing a preamplifier output of a reproduced signal. ■...Magnetic tape, 2a, 2b...Magnetic head, 5
・・・Envelope safety device, 6...Comparator, 7
- Memory control, 8... Field memory, 20... Microcomputer, 30... D/A
converter. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (1)

[Claims] (1) During high-speed playback, when the playback signal level from the recorded magnetic tape is higher than a preset level, the playback signal is stored in the field memory, and this stored content is used as the synchronization signal of the playback signal. In a video recording and reproducing apparatus that reads data asynchronously, the recording track width detection means measures the recording track width based on an envelope detection signal of a reproduction signal obtained when a magnetic head crosses the recording track on the magnetic tape; A video recording and reproducing apparatus comprising: level setting means for controlling switching of the predetermined level within one field based on the result and setting the predetermined level to an optimal level for signal reproduction.