JPH0481391B2 - - Google Patents

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 without noise bars during high-speed reproduction.

[Conventional technology]

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, an odd-numbered speed is generally selected for high-speed playback, but this takes advantage of the property that the noise 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, and if this property is used in a means that uses memory, the noise bar can be made narrower in some cases.

Figure 4 shows the high-speed playback system of the conventional VTR mentioned above.
In the figure, 1 is a recorded videotape,
The reproduced signal is led to a preamplifier 3 via the video heads 2a and 2b, and then sent to a video signal processing circuit 4. On the other hand, 5 is preamp 3
This is an envelope detector that extracts the envelope of the reproduced signal by the output of It is sent to the memory control circuit 7 which generates timing and addresses. Further, 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 output ports, and if the serial port is used, writing and reading from the memory can be performed asynchronously. The operation here is to transfer the video signal processing circuit 4 to the field memory 8.
An asynchronous operation is performed in which the contents of the field memory 8 are read out using the serial port while writing the reproduction signal from the field memory 8 .

On the other hand, 9 is a control head, and based on this output, a servo circuit 10 controls a capstor motor 11 and a reel motor 12 to control the running of the tape 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. 5 and 6 are diagrams for explaining the operation at this time. In FIG. 5, 50 is a video track, and A and B represent azimuth recording, with the video head 2a for A and the video head 2b for B having the same azimuth.

Now, when the video head 2a traces the broken line c in the figure, the output of the preamplifier 3 of the reproduced signal becomes as shown in FIG. 6a due to azimuth recording. Similarly, when the video head 2b traces the trajectory indicated by the broken line d in the figure, the output shown in FIG. 6b is obtained. When the contents of these two fields a and b in Fig. 6 are interpolated with each other on the time axis, a single field image as shown in Fig. 6 c is obtained, which is stored in the field memory 8 and displayed on the monitor. Ru.

The content of one field with almost no noise bars is obtained when 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 a popular VHS system, the head configuration is such that the standard mode and the 3x mode are used together, and the head specification is mainly for the 3x mode.

When standard mode recording is performed using a device with such specifications, 1/2 to 2/3 of the video track 50 becomes a guard band, resulting in a video track as shown at 51 in FIG. The outputs of the preamplifier 3 obtained by tracing the trajectories of broken lines e and f in the figure on this video track 51 by the video heads 2a and 2b are as shown in FIG. An image of one field interpolated with each other along the axes is shown in FIG. 8c. The portion g shown in FIG. 8 is an area where no video signal is obtained, and appears as a relatively large noise bar on the monitor screen.

[Problem that the invention seeks to solve]

As mentioned above, when a video track with a guard band is played back at high speed, there is a drawback that the noise cover cannot be completely removed even if field memory is applied.

The present invention solves the above-mentioned drawbacks and provides a video recording and reproducing device that can obtain high-quality video without noise bars even when playing back a video track with a guard band at high speed. .

[Means for solving problems]

In this invention, the noise bar position is predicted from the envelope detection signal using a microcomputer or the like, and data is not written to the memory address corresponding to the noise bar position based on the predicted determination.

[Effect]

In this invention, the position of the noise bar is predicted and writing of the noise bar to the memory is thereby stopped, so there is no need to perform operations such as removing the noise part through address operations in the memory and rearranging the memory contents again. Therefore, no new operations are required to asynchronously read out the memory contents in real time, and high-quality playback images can be easily obtained.

〔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 microcomputer);
This includes an input/output circuit 21 that receives the output from the comparator 6 and outputs an address update stop signal to the memory control circuit 7, a data memory 23 that temporarily stores data, a timer function, and a timer memory. It includes a timer 24, a mymallo processor 25 that performs calculations, and a program memory 22 that administers operation commands.
The microcomputer 20 and the comparator 6 are used as a noise part prediction means to predict the position of the guard band noise, and the microcomputer 20 and the memory control circuit 7 are used as an address control means to stop the addressing of the memory address position corresponding to the guard band noise part. is configured. The rest of the structure is the same as the conventional structure, and the same reference numerals as in FIG. 4 represent equivalent parts.

Next, we will discuss the operation.

Assume that the video heads 2a and 2b reproduce the trajectories e and f of the video tracks 51 in FIG. 7 on the video tape 1 at 4 times the speed in the reverse direction.
The outputs from the comparator 6 based on the reproduction envelope obtained at this time are shown in Fig. 2 a and b, respectively.
become that way. Here, the logic levels in FIGS. 2a and 2b simply indicate the read mode (level "H") and write mode (level "L") for the field memory 8.

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 out the memory contents. It does not mean that it is output, but rather that it is not written to memory. That is, it is assumed that the output of memory contents in the original read mode is performed using a serial port, and that the operation is asynchronous with random input.

By the way, when the rising and falling points between the two fields of the signals shown in FIG. 2a and b are detected, the waveform shown in FIG. 2c is obtained, and the "H" level portion of this waveform represents the noise bar portion. Therefore, Figure c
If the address update to the field memory 8 is stopped and the contents from the signal processing circuit 4 are no longer written to the memory 8 while the signal is at "H" level, the noise bar is removed and writing to the field memory 8 is stopped. It is something that can be done.

The operations described above are performed by the microcomputer 20 shown in FIG.
This will be explained with reference to the flowchart.

In the flowchart of FIG. 3, first, the address of the data memory 23 in the microcomputer 20 is initialized and set to address "1" (step 100).
Next, when the rising edge of the vertical synchronizing signal obtained from the signal processing circuit 4 is detected (step 101), the microcomputer 2
The timer 24 in 0 is initialized and started (steps 103-104). If the rising edge of the vertical synchronizing signal is not detected, the process is held until it is detected, or if the processing operation is in progress, the process moves to the next process (step 102).

Next, the output of the comparator 6 shown in FIG. 2a is read, and it is determined whether or not the logic level has been inverted to the current level (step 105). If it is not reversed, hold it until it is reversed. If it had been reversed,
The timer value at that time is written to the designated address location of the data memory 23. Then, the address is updated by +1 (steps 106-107). That is, here, after the timer value is written to address 1 specified in processing step (100), the address becomes address 2. This written content is the T1 value shown by the waveform in FIG. 2a.

Next, it is determined whether the address value incremented by 1 in the processing step (107) has become equal to "7" (step 108). This is because after measuring the T1 value to T6 value of the waveforms in Figure 2 a and b, the write memory address for each value is "1" to "6".
Address value "7" indicates that the measurement has ended. Therefore, if the address value is less than "7", that is, "1" to "6", repeat steps (101) to (107) described above to measure the T1 value and then write the contents to the corresponding memory location. In exactly the same way, T2-T6 values can also be measured and written to the appropriate memory location. When the measurement of the T1 to T6 values is completed, the address of the data memory 23 is reset to address 1 (step 109).

The future processing will be based on the results obtained from the previous processing.
This is a process for determining the noise bar position based on the T1 to T6 values. That is, when the rising edge of the vertical synchronizing signal from the video signal processing circuit 4 is detected again (step 110), the output to the memory control circuit 7 is set to the "L" level (step 111). Thereafter, the timer 24 is reset and restarted (processing steps 112 to 113).

Next, the microcomputer processor 25 compares the value of the started timer 24 with the contents of addresses "1" to "6" in the data memory 23, that is, the values T1 to T6 (steps 114 to 119). In this way,
First, the T1 values, which are the contents of address "1", become the same (step 114). Here, the "L" level output is inverted and the "H" level is output (step 120). Then, the contents of address "4", that is, the T4 value, become the same (step 117). At this time as well, the output level is similarly inverted to the "L" level (step 120). As described above, if the same procedure is performed for each of the remaining values of T2, T3, T5, and T6, the waveform shown in FIG. 2c will be obtained.
Note that after the processing for the T6 value (step 121) is completed, it is the same as the processing for one field has been completed, so the process returns to the judgment step 110 again to prepare for the processing of the next field.

In this embodiment, data is not written to the memory address corresponding to the noise bar position, so it is possible to perform noiseless high-speed playback without using a special head or a large number of head configurations. Since noise position information is obtained from the reproduction signal obtained by actually reproducing the video tape at high speed, noiseless high-speed reproduction is possible no matter what format the video track is recorded in. Furthermore, in this embodiment, there is no need to perform operations such as removing noise portions and rearranging the memory contents again using address operations in the memory, and no new operations are required to read out the memory contents asynchronously in real time. do not.

Here, in this embodiment, an example in which the noise bar is not relatively large is described, so there is no problem because the unrecorded part caused by recording except for the part corresponding to the noise bar is out of the display area. However, when the noise bar is large to a certain extent, unrecorded portions may appear below the display area. In such a case, it is desirable to insert a dummy non-recording zone above the display area and change the address of the field memory so that the true video portion is located in the center of the display area.

In the above embodiment, 4x speed was described 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 present invention can be applied to any even-numbered high-speed playback. Effects can be obtained.

In addition, although a microcomputer was used in the above embodiment,
Each control means may be constituted by hardware, and the same effects as in the above embodiment can be obtained.

〔Effect of the invention〕

As described above, according to the present invention, the noise bar position is predicted from the envelope detection signal of the reproduced signal, and data is not written to the memory address corresponding to the noise bar position, so there is no need to use a complicated configuration. , and has the effect of enabling noiseless high-speed reproduction of any recording format.

[Brief explanation of the drawing]

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 an operational 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 block diagram of a conventional video recording and reproducing device.
The figure shows the head trajectory when a video track recorded without guard band is played back at high speed. Figure 6 shows the preamplifier output of the playback signal. Figure 7
The figure shows the head locus when a guard band recorded video track is played back at high speed, and FIG. 8 shows the preamplifier output of the playback signal. DESCRIPTION OF SYMBOLS 1... Magnetic tape, 2a, 2b... Magnetic head, 5... Envelope detector, 6... Comparator, 7... Memory control circuit, 8... Field memory, 20... Microcomputer. 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 exceeds a predetermined level, the playback signal is stored in a field memory, and the stored content is used as the playback signal. In a video recording and reproducing apparatus that reads data asynchronously with a synchronization signal, noise position prediction means predicts the position of guard band noise generated when a magnetic head crosses a recording track on the magnetic tape based on an envelope detection signal of the reproduced signal. and address control means for stopping the addressing of the memory address position corresponding to the guard band noise portion based on the prediction result of the noise position prediction means when writing the reproduced signal to the field memory. Video recording and playback device.