JPS63136887A - Video recording and reproducing device - Google Patents

Abstract

PURPOSE:To enable a high speed reproduction with a good quality by supplying the most suitable reference potential to a comparator from the envelope signal of a regenerated signal corresponding to the time base variation of a recorded track width on a tape or of the regenerated signal, and adjusting the range of a write-in into a memory. CONSTITUTION:This device is provided with a microcomputer 20, a comparator 6, and a detecting means to detect the time base variation of a picture recorded track width on a video tape 1 and of the regenerated envelope signal, by an OR gate 13, and also with a level setting means to set the level of the reference potential, to be supplied to the comparator 6, by the microcomputer 20 and a D/A converter 30. Thus, because the most suitable potential at that time is supplied to the comparator 6, automatically corresponding to the time base variation of the recorded track width on the tape 1 and of the regenerated signal, an operation, such as to narrow the width of a noise bar manually as looking at the reproduced picture from the field memory 8 directly, comes useless, and besides, the useless noise bar is not displayed, and the reproduced picture with a good quality is easily obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a video recording and reproducing device, and particularly to a video recording and reproducing device that uses a field memory to obtain high-quality reproduced images with reduced noise bars during high-speed reproduction.

[Prior Art] - As a conventional example, a case will be described in which high-speed playback of a video tape recorder (hereinafter referred to as VTR) using a field memory is performed at an even multiple of 4 times the speed. Here, the high-speed playback is generally selected from an odd-numbered multiple speed, but this takes advantage of the property that the noise bar locks since 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 in each field, and if this property is utilized and memory is used, the noise bar can be made narrower in some cases.

FIG. 5 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 from 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. Further, a synchronization signal is sent from the video signal processing circuit 4 to the memory control circuit 7.

Note that the field memory 8 is a dual port memory (not shown) and has a random output and a serial output as output ports, and if a 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.

Suppose that videotape 1 is being played back at 4x speed in the reverse direction. FIGS. 6 and 7 are diagrams for explaining the operation at this time. In Figure 6, 50 is a video trunk, A and B represent azimuth recording,
The video head 2a has the same azimuth for A, and the video head 2b has the same azimuth for B.

Now, when the video head 2a traces the broken line d in the figure, the output of the preamplifier 3 of the reproduced signal becomes as shown in FIG. 7(a) due to azimuth recording. Similarly, video head 2b
When traces the locus of the broken line (e) in the figure, it becomes as shown in Figure 7 (b).
) output is obtained. When the contents of these two fields in Figure 7 (81, (b)) are interpolated with each other on the time axis, the
A one-field image as shown in FIG. 3(C) is obtained, which is stored in the field memory 8 and displayed on the monitor. Here, the envelope waveforms shown in FIGS. 7(a), (b), and (C) represent only the upper side of the vertically symmetrical AC waveform.

The content of the L field is such that the width of the video track is equal to or larger than the width of the magnetic head and there is no guard band. In fact, for example, in popular machines that have a head configuration that uses both the standard mode and the 3x mode in the VH3 system, the head specification is mainly for the 3x mode.

When recording in standard mode with a device with such specifications, a guard band is created on the video trunk 50, and 51 in FIG.
The video track will look like the one shown below.

7 do 2 a+2 on this video track 51 to video
The output of the preamplifier 3 obtained by b tracing the trajectory of the broken lines f and g in the figure is shown in Fig. 9 (a) and (b
), and the image of one field obtained by mutually interpolating these on the time axis becomes as shown in FIG. 9(C).

By the way, when writing the image interpolated on the time axis shown in FIGS. 7 and 9 (C) into the field memory 8, it is necessary to change the comparison potential of the comparator 6. That is, in FIG. 7(C), if the comparison potential of the comparator 6 is set to the level indicated by 81 and the portion written to the field memory 8 is limited, the interpolated image information is smoothly connected.

However, in FIG. 9(C), when a potential corresponding to Sl is applied to the comparator 6 in the same way as above, no image information can be obtained because there is no signal at the area indicated by J, and it becomes a noise bar on the screen. I'll get lost. Furthermore, when the head hits the tape poorly during high-speed playback, the obtained playback envelope signal causes time axis fluctuations. for example,
In FIG. 7(b), if the reproduced signal changes from the signal shown by the solid line to the signal shown by the broken line due to time axis fluctuation, then
In Fig. 7(C), if the potential indicated by 81 were applied as is in the same manner as above, no signal would be obtained in the part indicated by K due to time axis fluctuations, and it would appear as a noise bar on the screen. I end up.

[Problem that the invention seeks to solve]

As described above, in a system that uses field memory to perform high-speed playback at even multiple speeds and obtain signal information by interpolating the contents of each field, the recording track width on the tape and the resulting playback envelope signal The width of the noise bar cannot be narrowed unless the comparison potential at the comparator is varied according to the time-axis fluctuation of the noise bar and the writing range to the memory is adjusted.

This invention was made in view of the above points, and even when the recording track width on the tape differs from tape to tape, or even when the playback signal fluctuates on the time axis, the playback signal from the field memory during high-speed playback is An object of the present invention is to obtain a video recording and reproducing device capable of obtaining high-quality video with the minimum width of a noise bar.

[Means for solving problems]

In this invention, a microcomputer or the like is used to detect the recording trunk width on the tape and the time axis fluctuation of the playback signal from the envelope detection signal, and correspondingly, the optimal potential at that time is supplied to the comparator as a comparison potential. .

[Effect]

This invention automatically responds to the track width recorded on the tape and the time axis fluctuations of the playback signal, and supplies the optimum potential at that time to the comparator. There is no need to perform operations such as narrowing the width of the noise bar, and unnecessary noise bars are no longer displayed, making it easy to obtain high-quality reproduced images.

〔Example〕

Hereinafter, embodiments of the present invention will be described 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. A data memory 23 that temporarily stores data, a timer 24 that has a timer function and a timer memory, a microprocessor 25 that performs calculations, a program memory 22 that controls operation commands, and "H'" level or L level. The microcomputer 20, the comparator 6, and the OR gate 13 serve as means for detecting the recording trunk width on the video tape 1 and the time axis fluctuation of the playback envelope signal. The microcomputer 20 and the D/A converter 30 constitute a level setting means for setting the level of the comparison potential supplied to the comparator 6.Other configurations are the same as the conventional configuration, and the same symbols as in FIG. 4 are the same. represents.

Next, the operation will be explained.

Now, f of the video track 51 in FIG. 8 is recorded on the video tape 1 by the video heads 2a and 2b.

Suppose that the trajectory of g is played back in the opposite direction at 4x speed. This special reproduction envelope is shown in Figures 9(a) and (b), and is 1/3 of the maximum potential of this envelope.
The output from the microcomputer 20 is supplied to the comparator 6 via the D/A converter 30 in order to use the potential as the reference potential for comparison of the comparator 6.

Note that the maximum potential here is almost determined by the preamplifier 3, and the above-mentioned ⅓ potential is known in advance.

Furthermore, "1/3 potential" was selected as the comparison reference voltage in consideration of the noise margin of the reproduced signal, the superposition of DC components by the envelope detection circuit 5, and the like.

When such a potential is supplied as a comparison potential to the comparator 6, the outputs of the two fields obtained from the comparator 6 become as shown in FIGS. 2(a) and 2(b), respectively.

Here, the logic levels in FIGS. 2(a) and 2(b) simply refer to the read mode (level "
H”) and write 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 field memory 8 described previously, and the read mode is for reading and outputting the memory contents. This means that it is not written to memory.

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

Here, if we measure the times T1 and T2 between the levels "L" of Figure 2 (al, (bl), we can use the measured values to correlate with differences in recording track width and time axis fluctuations of the reproduced signal. Figure 7(a), (output of comparator 6 obtained from bl, Figure 2(C).

In (d), the period of level "L" is longer than in Fig. 2 (al) and (b), where the recording track width is narrow, and in Fig. 7 (b).
If the reproduced signal changes due to time axis fluctuations as shown by the broken line in , the output of the comparator 6 at that time will be the second
The result will be as shown in Figure (d)'. In other words, as can be seen by comparing with (d) for the same recording trunk width, the time of level "L" changes in accordance with the time axis fluctuation. Therefore, if the times TI and T2 are measured, changes in the times TI and T2 will cause the T1. It is possible to correlate T'2 with the difference in recording trunk width and the time axis fluctuation of the re-outgoing signal.

The above-mentioned times TI and T2 are measured over two fields. This is because there is a possibility that each field is recorded with a different head width, and it is also necessary to cope with time axis fluctuations for each field. Based on the times Tl and T2 obtained over two field periods as described above, reference is made to a table in which the optimum reference voltage to the comparator 6 corresponding to various values of TI and T2 is already determined, and each The optimal potential corresponding to Tl and T2 is D
/A converter 30. The above table is written in the program memory 22 in the microcomputer 20 in advance.

In this way, as the comparison supply voltage to the comparator 6, the potentials at 82 points of the waveform shown in FIG. 9(C) are applied to the voltage recorded on the track 51 shown in FIG.
In addition, for what is recorded on the track 50 shown in FIG. 6, the potential shown in FIG.
If a time axis fluctuation as shown by the broken line in Figure (b) occurs, supplying the potential shown at 83 in Figure 7 (C1) will ensure that the envelopes interpolated for each field are connected smoothly. The reproduced signal is written into the field memory 8, and a high-quality reproduced image with the narrowest noise bar width is obtained.

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

In the flowchart of FIG. 4, first, the output circuit 26 in the microcomputer 26 outputs "(" to prohibit writing to the memo (step 100). Next, the data memory 23 in the microcomputer 20 The memory of is initialized and 1 is set at address O (step 101).Next, in order to supply the comparator 6 with a potential that is 1/3 of the maximum potential of the envelope signal, the input/output circuit of the D/A converter 30 is 21 to output the potential code (step 102
).

After performing the initial settings in this way, when the rising edge of the vertical synchronizing signal obtained from the video signal processing circuit 4 is detected (step 103), the falling edge of the output from the comparator 6 is detected for writing to the field memory 8. When this is detected, the timer 24 in the microcomputer 20 is reset and started (step 105).

If the rising edge of the vertical synchronizing signal and the falling edge of the output signal of the comparator 6 are not detected, wait until they are detected. Next, after the timer is started, the rise of the output signal of the comparator 6 is detected, and it is determined whether the output logic has been inverted (step 106). If it is not detected, wait until it is detected.

If detected, the timer value of the timer 24 in the microcomputer 20 is stored in the address specified by the contents of address θ of the data memory 23 (step 107), and 1 is added to the contents of address 0 (step 108). That is, here processing step 1
After the timer value is written to the memory address 1 specified by 01, it becomes 2.

Then, determine whether the content of address 0 is 3 (
Step 109). Here, since the content of address O is 2, the process returns to step 103. Then, the second field is measured in the same manner as the first field. Then, in processing step 109, the content of address 0 is 3, so the process moves to the next step. That is, step 109 is a processing step for determining whether or not measurements have been made over two fields. At this point, T1 and T2 have been measured in the waveforms (al, (bl) of FIG. 2, and the corresponding values have been written to addresses 1 and 2 of the memory, respectively.

Next, the process moves to step 110, and the contents obtained by the measurements up to now, that is, the contents of address 1.2 in the data memory 23, and the table values previously created in the area of the program memory 22 in the microcomputer 20 are combined. Compare. The table here includes various TIs determined experimentally in advance,
The optimum comparison potential to the comparator 6 for the value of T2 is recorded. Therefore, a corresponding optimum potential is selected from this table, and this potential code is output (step 111). Here, the code is BC expressed in binary numbers.
Indicates D code.

Next, the rising edge of vertical synchronization is detected (step 112).

If not detected, wait until it is detected.

Then, 'L' is output from the output circuit 26 (step 1
13). This opens the gate of the OR gate 13, and the output of the comparator 6 (in step 111, the gate of the comparator 6
(obtained by outputting the optimum potential to the field memory 8). The I write/read signal is input to the memory control 7 via the OR gate 13, and writing to the field memory 8 is started by the optimum write/read signal.

Next, vertical synchronization is detected twice (steps 114 and 115).
), this is because signals for two fields are written into the field memory 8, and reproduced signals are interpolated with each other within the memory 8.

Next, the output circuit 26 outputs “H” (step 11
6). As a result, writing to the field memory 8 is inhibited again, and the contents written to the memory 8 immediately before appear as a still image on the screen until the next "L" is output.

Next, it is determined whether the mode is speed search (step 117), and if it is not the speed search mode, it moves to the next process, and if it is the speed search mode, it returns to step 101 again to respond to the time axis fluctuation. Measure TI and T2 again.

FIG. 3 shows the vertical synchronizing signal and the output logic from the output circuit 26 in the above processing. In this figure, T1 and T2 are measured while the output logic is "H". Then, TI between the two fields that are “L”,
Synthesize the screen with the minimum noise bar using the optimal write/read signal corresponding to T2, and measure TI and T2 again in the next "H' period to correspond to time axis fluctuations, and during that time, synthesize immediately before Input the image from the field memory as a still image.

In this embodiment, the comparison potential of the comparator 6 is determined using the envelope detection signal according to the difference in recording track width and the time axis fluctuation of the reproduced envelope detection signal, so manual adjustment is not required. (You can always minimize the width of the noise bar and get high-quality playback images.)

In the above embodiment, the case of 4x playback was explained as high-speed playback, but the present invention is not limited to this 4x speed, but can be applied to any even numbered speed, and the above embodiment The same effect as in the example 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, the field memory used here is dual-port memory (or multi-port memory).
This can also be done with general purpose memory.

〔Effect of the invention〕

As described above, according to the present invention, the optimal comparison potential is supplied to the comparator according to the recording trunk width on the tape and the time axis fluctuation of the reproduced signal from the envelope signal of the reproduced signal, and the writing range to the memory is automatically determined. Since the adjustment is made in a consistent manner, it is possible to perform high-quality high-speed playback with minimal noise bars, taking into account time axis fluctuations, regardless of the tape recorded with any recording track width.

[Brief explanation of the drawing]

FIG. 1 is a block configuration diagram of a video recording and reproducing device according to an embodiment of the present invention, FIGS. 2 and 3 are signal waveform diagrams for explaining the operation of the device, and FIG. 4 is a diagram showing the operation of the device. Flowchart for explanation; FIG. 5 is a block diagram of a conventional video recording and reproducing device; FIG. 6 is a diagram showing the head trajectory when a video track recorded without guard panning is played back at high speed; and FIG. FIG. 8 is a diagram showing the head trajectory when a guard band recorded video track is played back at high speed, and FIG. 9 is a diagram showing the reproduction preamp output. 1... Magnetic tape, 2a, 2b... Magnetic head, 5
... Envelope detector, 6... Comparator, 7
...Memory control, 8...Field memory, 13...OR gate, 20...Microcomputer. Note that the same reference numerals in the figures indicate the same or equivalent parts. Embedded Ken Hayase - Figure 1 Figure 2 Figure 5 Figure 7 To 17-yi, 〆1l14f--→ Figure 9

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, a comparison means for comparing an envelope detection signal of a reproduced signal obtained when a magnetic head crosses a recording track on the magnetic tape with a certain level, and a comparison result that determines whether one of the signals is higher than the other. a detection means for measuring a large or small time and detecting a recording track width and a time axis fluctuation of the envelope detection signal based on the measurement result;
A video recording and reproducing apparatus comprising: level setting means for setting the predetermined level to an optimum level for signal reproduction based on the detection result.