JPS634780A - Video signal reproducing device - Google Patents

Abstract

PURPOSE:To obtain a good picture which hardly generates noise when the track is changed without increasing the number of reproducing heads by inserting a reproducing signal delayed by a field delaying circuit into a silence signal part occurred at the time of high speed reproducing. CONSTITUTION:A switch 7 changes over a usual reproducing signal not to pass through a field delaying circuit out of the outputs of heads A and B and a switch 8 changes over the reproducing signal through the field delaying circuit. A switching signal generating device 9 controls these switches 7 and 8 so that the head selection by the switches 7 and 8 can be mutually different. The reproducing signal from two heads through a channel 1 and a channel 3 comes to be one signal by the switch 7, and simultaneously, the reproducing signal delayed for one field by field delaying circuits 5 and 6 provided at a channel 2 and a channel 4 is changed over for the field by the switch 8, and synthesized to one signal.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention provides a function for extracting and reproducing signals on a tape while running the tape at high speed, and searching for recorded contents on the tape in a short time. The present invention relates to a video signal reproducing device comprising:

<Prior art> In a helical scan type video tape recorder,
When using the conventional high-speed playback method, if the tape is running in the same direction as during recording, the head will scan the tape in the scanning pattern shown in Figure 2, and if the tape is running in the opposite direction to that during recording. In this case, the scanning pattern shown in FIG. 4 is obtained.

For example, as shown in FIG. 2, the head (A) that starts scanning from track number T1 is TI
+T2. . . . , the head (B) scans across each track of T7, and then the head (B) scans across each of the T-th tracks as shown in trajectory b]. Perform scanning. After that, it switches to head (A) again, and this is track T 15+ T 16+...
....

Scanning is performed like a locus a2 that crosses T21, and the same scanning pattern is repeated thereafter. FIG. 3 shows signals obtained by the head (A) and head (B) in this case. Now, this video tape recorder records T1 with the head (B), records T2 with the head (A), and so on in a repeating manner, and the head (A) moves the head in the +α0 direction, for example. In the so-called azimuth recording method using a head with a tilted gap, so-called azimuth angle, when scanning T1-T1, the reproduced signal from T1 cannot be obtained sufficiently due to so-called azimuth loss, and - At T2, since the azimuth angle is the same, a reproduced signal can be obtained. That is, in scanning by head (A),
A reproduced signal cannot be obtained from the odd-numbered tracks, and a reproduced signal can only be obtained from the even-numbered tracks. Also, the head (
In case B), for example, when the head gap is tilted in the -α direction, if T8 to TI4 are scanned, the reproduced signal will not be obtained from the even-numbered tracks, but will be obtained only from the odd-numbered tracks.

Similarly, when running the chive in the opposite direction to the recording time, the fourth
As shown in the figure, by scanning with the head (A).

When scanning with the head (B), reproduction signals are obtained only from odd-numbered tracks.

The signals obtained by the head (A) and head (8) in this case are shown in FIG.

<Problems to be solved by the invention> In the case of the above-mentioned high-speed reproduction, the head (A) and the head (B
) Each output does not have a continuous waveform as shown in Figures 3 and 5, and there is a part with no 18 in the middle.
Usually, tape recording systems often involve FM modulation recording, so if the read signal is demodulated as it is, this no-signal portion will be reproduced as very unsightly noise.

A conventional method to solve the above drawback is to make the width of the playback head wider than the recording track width to reduce the no-signal area as much as possible, but even in this case, the no-signal area inevitably remains, making it difficult to obtain sufficient playback image quality. It was difficult to obtain.

In addition, when recording at two or more tape speeds, if the width of the playback head is widened, if the tape speed is slow, adjacent tracks will also be scanned, and unnecessary signals from the adjacent tracks will also be played back. It is not desirable to gradually widen the width of the reproducing head because this interferes with the signal desired to be reproduced and results in a very unsightly image. For this reason, the conventional method was to prepare several sets of heads according to the tape speed during recording, and to switch between them according to the recording and playback speed, but this method was complicated and expensive. It was very expensive.

Means for Solving the Problems> The present invention has been made in order to solve the above problems, and is capable of high-speed reproduction in the H position for reproducing video signals recorded on a recording medium by a helical scan type video signal recording device. Sometimes,
means for obtaining a playback output from the video head; a field delay circuit that delays the playback output from the video head by one field; a switch for selecting the playback output from the video head and the output of the field delay circuit; (with a switching signal generation means that generates a switching signal, and a field delay circuit)! ! The extended playback signal is inserted into the no-signal portion that occurs during high-speed playback.

Effect> According to the above configuration, it is possible to eliminate the gradual signal portion during high-speed reproduction using only a normal reproduction head, and therefore, a continuous reproduced video signal can be obtained.

<Example> An example of the present invention will be described below. FIG. 6 shows a tape scanning pattern according to the present invention, in which the tape is run at high speed in the same direction as the tape is running during recording.The signal reproduced by the head (A) in the first field is the head of FIG. This is the hatched portion on the scanning locus a1, and its output waveform is the portion al in FIG. 7(a). In the next field during this high-speed playback, the head (B
) scans the part shown in the scanning locus bl in FIG. 6, and its output waveform is the 7th [! As shown in bl of I(a).

The scanning by both heads (A) and (B) is repeated thereafter.

In FIG. 1, the reproduced video signal from the head (A) is divided into path 1 and path 2, and the signal on path 2 is sent to a field consisting of an AD converter 5a, a field memory 5b, a DA converter 5c, and a low-pass filter 5d. It is added to the delay circuit 5. First, the analog video signal on path 2 is sampled and held by the AD converter 5a, and converted into a digital signal. After this digital signal is stored in the field memory 5b, it is read out with a delay of one field.

The read signal is converted back into an analog video signal by the DA converter 50 and outputted via the low-pass filter 5d. - On the other hand, the reproduced video signal from the head (8) is divided into paths 3 and 4, and the signal on path 4 is sent to the AD converter 6a, field memory 6b, and DA converter 6 as in the field delay circuit 5 described above.
c, and passes through a field delay circuit 6 composed of a CI-pass filter 6d, and is similarly delayed by one field. The iH signal on path 2 and path 4 delayed through the field delay circuit as described above is sent to switch 8. Note that the paths 1 and 3 are applied to the switch 7 without going through the field delay circuit.

Switches 7 and 8 are switches for selecting outputs from the heads (A) and (B), and are switched for each field by a switching signal for head switching from a switching signal generator 9. Switch 7 is the head (A),
Among the outputs of (B), the normal reproduction signal which does not pass through the field delay circuit is switched, and the switch 8 switches the reproduction iH signal through the field delay circuit. A switching signal generator 9 controls these switches 7.8 so that head selection by the switches 7.8 is different from each other. For example, a signal having the opposite phase to the switching signal applied to the switch 7 is applied to the switch 8. If the switch 7 and the switch 8 are set to , the switches 7 and 8 are switched to select different heads.

Therefore, if the switch 7.8 is configured as described above, the playback signals from the two heads that have passed through the paths 1 and 3 become one signal as shown in FIG. 7(a) by the switch 7, and at the same time and the field delay time provided on route 4''
The reproduced signal delayed by l fields by 05 and 6 is
Switch 8 is used to switch each field, as shown in Fig. 7 (B).
The signals are combined into one signal shown in . As mentioned above, control signals with opposite phases are applied to switch 8 and switch 7, so when the head (B) output is output from switch 7, the output from switch 8 is delayed by one field. When the output of head (A) is output and the output of head (A) is output from switch 7, l is output from switch 8.
The field-delayed head (B) outputs the output, and the process is repeated thereafter.

Switch 7 shown in No. 71ffl (a) and (b).
The output signals of 8 are further applied to the switch 13 and are combined into one signal shown in FIG. 7(d). This switch】
In order to obtain 3 switching signals, the outputs of the switches 7 and 7 are envelope-detected by envelope detectors 10 and 11, respectively, and the respective outputs are input to a comparator 12. Comparator 1
2 compares the levels of these two signals and outputs a comparison output signal.

For example, as shown in Fig. 7(c), the signal level shown in Fig. 7(a) falls when it becomes smaller than the bell shown in Fig. 7(b), and conversely, when it becomes larger, This is a pulse waveform that rises when the

Using this as a switching signal, in addition to switch 7.3, the output of the switch 7.8 is switched to the side where the signal exists to obtain the continuous reproduced video signal shown in FIG. 7(d). Also,
Even when the tape is run in the opposite direction to that during recording, continuous reproduced video signals can be obtained using the same method.

The switch mentioned above? , 8, 13. Each switching method is merely an example, and Ike's method may also be used.

Furthermore, in Figures 7(a) and 7(b), when the signal in section al and the signal in section b1 are combined, it is necessary to interpolate each other in time, so the tape running speed during high-speed playback is different from that at the time of recording. It must be an even multiple of .

<Effects of the Invention> As explained above, the video signal reproducing device of the present invention has a means for obtaining a playback output from the video head during high-speed playback, and a field delay that delays the playback output from the video head by one field. A circuit, a switch for selecting the playback output from the video head and the output of the field delay circuit, and a switching signal generating means for generating a switching signal for the switch, and a reproduction word delayed by the field delay circuit. , which is inserted into the no-signal portion that occurs during high-speed playback. Therefore, even when the present invention is applied to a video tape recorder having two or more types of tape recording speeds, the present invention can be applied without increasing the number of playback heads.
It is possible to obtain a high-quality screen with almost no noise when changing tracks, and it is also inexpensive and practically useful.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of the present invention, FIG. 2 is a diagram showing an example of a conventional tape scanning pattern when the tape is run in the same direction as the tape running direction during recording during high-speed playback, and FIG. is the playback head output waveform of scanning according to Fig. 2,
FIG. 4 is a diagram showing -1511 of a conventional tape scanning pattern when the tape is run in the opposite direction to the 20 o'clock tape running direction during high-speed playback, and FIG. 5 is a reproduction head output waveform of scanning according to FIG. FIG. 6 is a diagram showing an example of a tape scanning pattern according to the present invention when the tape is run in the same direction as the tape running direction during recording, and FIG. 7 is a reproducing head output waveform in the case of FIG.

Claims (2)

[Claims] (1) In a device for reproducing a video signal recorded on a recording medium by a helical scan video signal recording device, means for obtaining a playback output from a video head during high-speed playback;
a field delay circuit that delays the playback output from the video head by one field; a switch that selects between the playback output from the video head and the output of the field delay circuit; and switching signal generating means that generates a switching signal for the switch. and each time the switching signal generating means generates a switching signal so that an output that is a composite of the playback output from the video head and the output of the field delay circuit is obtained on the output side of the switch. Video signal reproducing device. (2) The video signal reproducing apparatus according to claim 1, wherein during the high-speed reproduction, the recording medium is run at an even number times the speed of recording.