JPH0475711B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a video signal reproducing device, and is particularly suitable for application to variable speed reproduction of a recording medium formed by sequentially arranging a large number of recording tracks diagonally. It is something.

[Background technology and its problems]

In a video tape recorder (VTR), which is a video signal reproducing device of this type, the recorded image can be monitored by fast-forwarding the tape as a recording medium and reproducing the video signal from the recording track scanned by the video head. There is something I did. That is, as shown in FIG. 1, a large number of recording tracks 3 are formed diagonally adjacent to each other by a video head 2 on a tape 1 running at a normal speed, and when the tape 1 is played at a fast forward playback mode, the tape 1 is played at, for example, triple speed. By fast forwarding the tape 1 from the running start end of the first track 3A to the second track 3A.
The video head 2 scans along the travel path 4 across the track 3C to the end of the third track 3C.

The playback signal obtained from video head 2 at this time
As shown in FIG. 2, S1 mainly scans the first track 3A in the first scanning section A from the state in which the head 2 is scanning the first track 3A to the state in which it moves to the second track 3B. video signal of
S1A is reproduced, and following this first scanning section A, the head 2 scans the second track 3B and then moves to the third track 3C.
In the scanning section B, the video signal S1B of the second track 3B is mainly reproduced, and following this second scanning section B, in the third scanning section C in which the head 2 scans the third track 3C. The video signal S1C of the third track 3C is mainly reproduced.

However, in reality, as shown in FIG. 3, the head 2 moves from the first track 3A to the second track 3B.
When moving from the second track 3B to the third track 3C, both the video signals of the first and second tracks 3A, 3B and the video signals of the second and third tracks 3B, 3C are used. Ranges Y1 and Y2 exist at the boundary positions of scanning sections A and B and at the boundary positions of scanning sections B and C, in which both are simultaneously reproduced and both signal levels are quite low, and in these ranges Y1 and Y2, the signal level is quite low. It is not possible to obtain a video signal, and this results in the appearance of noise called guard bands 7A and 7B on the screen 6 as shown in FIG.

In addition, as shown in FIG. 2, the video signal S1 near the guard bands 7A and 7B is caused by the fact that the tracks 3A, 3B and 3C are sequentially shifted from each other by a predetermined phase amount x. It is unavoidable that video signal portions W having a phase amount corresponding to the shift are reproduced redundantly, and as a result, the monitorable image 6 becomes elongated in the vertical direction (particularly downward).

Incidentally, if the head 2 moves to the second track 3B at the position of phase a2 of the reproduced signal S1A of the first track 3A, the reproduced signal of the second track 3B
The phase of S1B becomes a2-x, and since the video signal portion W from a2-x to a2 is a portion that has already been reproduced in the reproduced signal S1A of the first track 3A, it overlaps. Similarly, the second track
If the head 2 moves to the third track 3B at the position a3 of the phase a3 of the reproduced signal S1B of the third track 3B, the phase of the reproduced signal S1C from the third track 3B becomes a3-x, and from a3-x to a3 The video signal portion W is a portion that has already been reproduced in the reproduction signal S1B of the second track 3B, and thus overlaps with the portion W of the video signal.

Therefore, the image 6 appearing on the monitor is reproduced signals S1A, S1B, and S1B obtained by the head 2 scanning the scanning sections A, B, and C, as shown in FIG.
Image portions 6A, 6B, 6 formed by S1C
C is obtained, and these image parts 6A, 6B, 6C
Guard bands 7A and 7B are generated at the boundaries between the two. The same image as the end portion of the image portion 6A near the guard band 7A is overlapped at the start portion of the image portion 6B near the guard band 7A, and similarly, an image is generated at the start portion of the image portion 6C near the guard band 7B. The same image as the end portion of portion 6B near guard band 7B will be duplicated.

However, considering the purpose of fast-forward playback, it is desirable that the image obtained by fast-forward playback be as close as possible to the image obtained during normal playback.
Particularly regarding the image of FIG. 4, firstly, the downward extension of the image should be made as small as possible; secondly, the widths of guard bands 7A and 7B should be made as narrow as possible, and if possible, they should be removed; and thirdly, guardbands 7A and 7B should be removed as much as possible.
It is desirable to minimize the overlapping area of the image portions that occurs near 7B and 7B.

[Purpose of the invention]

The present invention has been made in consideration of the above points, and
The aim is to effectively reduce the problems of image length, guard band width, and overlap of image parts.

[Summary of the invention]

In order to achieve this purpose, the present invention includes:
When the guard band noise signal generated in the reproduced signal obtained from the head when the head crosses between recording tracks in the fast forward playback mode is stored in the temporary storage memory or read out, the guard band noise signal is changed and controlled by changing the line address. Extract the noise signal line data.

〔Example〕

An embodiment of the present invention will be described in detail below with reference to the drawings. In FIG. 5, reference numeral 11 denotes a video signal demodulation circuit, in which the playback signal S1 of the head 2 in the fast-forward playback mode is
is stored in the temporary storage video signal memory 13 by the address signal S2 of the line address sequential control circuit 12 with line addresses that naturally increase in 1H intervals (that is, one horizontal synchronization interval), and then the data in the memory 13 is stored. The signals are sequentially read out 1H at a time and sent out as the output video signal S3. In practice, the video signal memory 13 is included in a time axis correction circuit provided in the video signal demodulation circuit 11, and controls the timing of reading out data from the memory 13 to adjust the time axis of the output video signal S3. It is designed so that it can be controlled as necessary (for example, the output video signal
Processing such as decompression and extension of S3).

As shown in FIG. 6, the line address sequence control circuit 12 receives the horizontal synchronizing signal S4 included in the reproduced signal of the head 2 through an input terminal 15 to an automatic frequency control circuit 16 (including a dropout correction circuit), and addresses the lines. A count timing pulse signal S5 for the counter 17 is formed. In this way, the address counter 17 sends out to the video signal memory 13 a write address signal S6 which is counted up naturally at a speed corresponding to the scanning speed of the head 2 with respect to the tape 1.

The write address signal S6 is also applied to the address change circuit 18. The address change circuit 18 outputs a changed address signal S7 obtained by subtracting a predetermined number of line addresses k from the contents of the address signal S6 to the address counter 1 through a load gate circuit 19.
7 as the load data signal S8. Here, the address change circuit 18 has the function of extracting some or all of the lines forming the guard bands 7A and 7B of the image 6 in FIG. 4, and the number k of lines to be extracted is set as change data. ing.

A guard band end detection signal S9 from a guard band end detection circuit 20 is applied to the load gate circuit 19 as an open control signal. The guard band end detection circuit 20 receives, for example, a reproduced signal from the head 2.
For example, when the signal level of S1 is in a dropout state, which is below a predetermined level, a guard band detection signal S10 that falls to a logic "L" level is applied through the terminal 21, and when this guard band detection signal S11 returns, it rises. At this time, the guard band end detection circuit 20 sends out a guard band end detection signal S9 having a predetermined pulse width. At this time, the load gate circuit 19 opens and loads the address change signal S7 of the address change circuit 18 into the address counter 17.

Thus, the contents of the address counter 17 are the same as the guard band 7 when the guard band detection signal S10 rises.
When the data of the line address corresponding to A or 7B (Fig. 4) has finished being stored in the memory 13, the contents of the address signal S6 are changed to a line obtained by subtracting the predetermined number of drawn lines k from the address at the end of storage. address, and then updates the incoming data with the already stored data for k lines of guard bands 7A and 7B, and as a result, the updated data of the lines storing guard band noise signals is updated. Data will be extracted from memory 13.

In this embodiment, the fast-forward reproduction mode signal S11 is applied to the load gate circuit 19 as an open condition signal through the terminal 22, so that the address counter 17 can be loaded by the address change signal S7 only in the fast-forward reproduction mode. ing.

In the above configuration, when the head 2 is in the fast-forward playback mode and is scanning the first scanning section A (FIG. 1), the video signal S1A is played back from the first track 3A as described above with respect to FIG. 7th
As shown in the figure, line address M1 of memory 13
...M2... is stored one line at a time in the memory area. Here, guard band noise data representing guard band 7A is stored in the memory area extending before and after address M2, which corresponds to the point where scanning section A shifts to scanning section B, but eventually the storage area of guard band 7A becomes address M2. When it ends at M3, the guard band end detection circuit 20 detects this and sends an address change signal to the address change circuit 18.
Load S7 into address counter 17.

At this time, the address signal S6 is the address M4 (=M3-k) obtained by subtracting the number of addresses k from the address M3.
Therefore, the memory 13 updates and stores the signals that arrive from now on in the memory area starting from address M4. The signal that will arrive hereafter is the video signal S1B reproduced from the track 3B by the head 2 scanning the second scanning section B, and this is stored in the memory area at addresses M4...M2...M3...M5... for one line. They will be stored one by one.

After that, a guard band 7B is generated near the point where the head 2 moves from the scanning section B to the scanning section C, and is stored in the memory area before and after the address M5 corresponding to the point where the guard band 7B shifts, but eventually the noise of the guard band 7B The data storage area is the address
When it ends at M6, the guard band end detection circuit 20 detects this and loads the address change signal S7 of the address change circuit 18 into the address counter 17.

Therefore, the address signal S6 becomes the address M7 (=M6 - k) obtained by subtracting the address number k from the address M6, and thereafter the memory 13 is reproduced from the track 3C by the head 2 scanning the third scanning section C. Video signal S1C to address M7…M5…M6…
Store one line at a time in the M8's memory area.

In this way, head 2 scans the scanning sections A, B, and C.
The guard band noise generated in the reproduced signal S1 is temporarily stored in the memory 13 each time the track is changed while the data is sequentially scanned, but each time the guard band ends, the address change circuit 18 operates and a new signal arrives. By returning the video signal to the memory area in the memory 13 that stores the guard band noise and overwriting it, the storage area for the guard band noise data remaining in the memory 13 is significantly reduced.

If the data thus stored in the memory 13 is read out using naturally increasing addresses, the image shown in FIG. 8 is obtained.

According to the configuration shown in FIG. 6, a predetermined number of line data forming the guard bands 7A and 7B in FIG. The width can be narrowed, making it easier to monitor the image 6. In addition to this, guard band 7A
The noise data corresponding to 7B and 7B are reproduced by the reproduced signal S1 every time the head 2 changes the track being scanned.
Since the line data corresponding to the overlap playback signal part that occurs in the playback signal part is included, it is possible to extract the line data corresponding to the overlap playback signal part, so that it is possible to reproduce an image that is substantially close to the image obtained during normal playback during fast-forward playback. become.

From this point of view, if the number k of lines to be extracted is made equal to the amount of positional deviation x between the tracks 3A, 3B, and 3C, it is possible to obtain an image that does not extend for approximately the same amount of time as the image during normal reproduction.

In a preferred embodiment, the misalignment between tracks is
9 when 2.5H and tape running speed is 10x
guard bands appear, and their pitch is (25+
262.5) ÷ 9 = 32 lines, of which the number of lines that become guard band noise is about 1/10 (about 3 to 4 lines). At this time, by extracting 2.5H (actually 2H or 3H) of the guard band noise according to the present invention, the noise can be reduced to less than half.

In this example, if the tape running speed is 20 times faster, the number of guard band noise lines is 2H.
Therefore, by subtracting 2 to 3 H according to the present invention, guard band noise can be prevented from appearing in the image.

Although the above example describes the case of recording and reproducing with one head, it is also possible to record component signals on multiple tracks using multiple heads.
The present invention can be applied in the same manner as described above even in the case where each head reproduces video signals from the plurality of tracks in the fast-forward reproduction mode.

Furthermore, in the above example, the line data of the guard band noise signal is extracted when storing the video signal in the temporary storage memory, but instead of this, all the reproduced video signals are stored in the memory. Even if the line data of the guard band noise signal is extracted during subsequent reading, the same effect as in the above case can be obtained.

〔Effect of the invention〕

As described above, according to the present invention, by extracting the guard band noise that occurs in the playback signal when the head moves between tracks in the fast forward playback mode, an image with less downward extension and a narrow guard band width is obtained. In addition, by removing overlapping reproduced signal portions based on positional deviation between tracks, it is possible to obtain an image substantially the same as that obtained during normal reproduction. In this way, useful information can be used effectively without being lost.
Incidentally, as a countermeasure to the screen lengthening, it may be possible to provide a window in the time axis correction circuit to mask the top, bottom, or top and bottom of the screen.
In this way, there is a problem in that the guard band remains wide even though the effective screen is cut off, but the present invention can effectively solve this problem.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing the movement of the head in fast-forward playback mode, FIGS. 2 and 3 are signal diagrams showing the reproduction signal, FIG. 4 is a schematic diagram showing a conventional monitor image, and FIG. The figure is a block diagram showing an embodiment of the video signal reproducing device according to the present invention, and FIG. 6 is a block diagram showing the detailed configuration of the line address control circuit.
FIG. 7 is a schematic diagram for explaining how data is stored in the memory, and FIG. 8 is a schematic diagram showing a monitor image obtained by the configuration of FIG. 6. 1...Tape, 2...Head, 3, 3A, 3
B, 3C... Track, 11... Video signal demodulation circuit, 12... Line address control circuit, 13...
Video signal memory for temporary storage, 16... automatic frequency control circuit, 17... address counter, 18...
Address change circuit, 19...Load gate circuit,
20...Guard band end detection circuit.

Claims (1)

[Claims] 1 During fast-forward playback mode, the playback signal obtained from the head that scans across a plurality of recording tracks formed adjacent to each other is stored line by line in a temporary storage memory, and then the stored playback signal is sequentially accessed by line address. In the video signal reproducing apparatus, a guard band noise signal generated in the reproduced signal when the head crosses between the tracks is stored in the temporary memory, or when read out, the guard band noise signal is stored in the temporary memory. A video signal reproducing device comprising a line address control circuit that extracts line data of the guard band noise signal by changing and controlling the line address.