JPS6123494A - Video signal reproducing device - Google Patents

Abstract

PURPOSE:To apply line sequencing to a line sequential signal with no error even if the S/N in extremely low by discriminating the kind of the line sequential signal at each horizontal synchronizing period, processing statistically the signal at each prescribed period and controlling a simultaneous means. CONSTITUTION:A line sequential color difference signal (a) having a DC offset at a period of 2H is inputted from a terminal t1 and fed to a sample-and-hold circuit 1. On the other hand, a horizontal synchronizing signal (d) phase-locked to the horizontal synchronizing signal of a luminance signal is inputted to monostable multivibrators 7, 10 and a DFF8 from a terminal t2. An output signal (n) of the DFF8 is inputted to an EXOR 15 and an output signal (m) of the EXOR 15 is inputted to an EXOR 20. The connection of switches SW1, SW2 is switched by changing over an output signal (g) of the EXOR 20 to high and low levels to output a color difference signal subjected to line sequencing. Thus, even if the deterioration of the S/N due to dropout is produced in the signal (a), the phase of the switching signal (g) of the SW1, SW2 is not discontinuous.

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field The present invention relates to a video signal reproducing device, and more particularly to a device for reproducing a video signal including a line sequential signal.

<Description of Prior Art> Generally, when synchronizing line sequential signals, the type of the line sequential signals must be determined for each horizontal scanning period (H), and when recording or transmitting, the type must be determined. The signal format is such that it can be distinguished in some way. For example, when converting a 211 type signal into fIaJlrt and recording it, jj+ was offset and frequency offset was applied to the DC component with a 2H period, and a flag signal was added with a 2H period. However, when determining the type of a line sequential signal that has been subjected to these processes using a reproduction system, it is not possible to accurately determine the type due to effects such as dropout and transmission distortion.

The following will explain an example of a device that continuously reproduces a video signal containing a line-sequential color difference signal recorded in one field on a circular recording track on a magnetic sheet and having a DO offset of 2H period to reproduce a still image. do.

FIG. 1 is a block diagram showing the main structure of a conventional playback device of this type. Moreover, FIG. 2 is a waveform diagram showing the waveforms of each part of FIGS. 1(a) to (f).

In FIG. 1, tl is a terminal to which a line-sequential color difference signal obtained from the reproduced video signal is supplied, and t2 is a terminal to which a horizontal synchronizing signal obtained from the reproduced video signal is supplied.

Further, 1 is a sample and hold circuit, 2 is an amplifier that amplifies the output of the sample and hold circuit 1, 3 is a comparator that compares the output of the amplifier with a predetermined level, and 4 is a horizontal synchronizing signal that uses the output of the comparator 6 as a data input. (shown in Fig. 2(,i)) is a D-type flip-flop (D'F'?) that is triggered by the falling edge, 6 is an IH (61
556μ8θC) delay line, 7 is a monomulti which is triggered by the horizontal synchronization signal (a) and forms the signal shown in Figure 2(b), 8W1 and SW2 are DFFs. When the output signal of 4 is at a high level, swi E of SW2 is A%, F of SW2 is C, E of sw1 is B at low level,, [F of EW2
are connected to C, respectively, and transmit the line-to-line timed color difference signals to t.
3, it will be supplied to t4.

Assume that the center level is higher than that in 2 and is recorded with a line offset. At this time, if R-Y is being reproduced at a certain H, during that period, the output signal (b) of the mono multi 7
The signal sampled and held at the falling edge of is at high level. Therefore, the output signal of DFF 4 (e
) is at a high level. That is, if the output signal of the 1H delay line 6 is R-Y, E of swl is connected to A, and 9R-Y is output from the terminal t3. Similarly, from the terminal t4, the signal 9B-Y is outputted simultaneously.

However, when obtaining a line sequential color difference signal from a line sequential color difference signal with the above configuration, if there is some kind of flaw in the line sequential color difference signal at the sampling timing, such as BIN deterioration due to dropout, etc., the correct Do offset sample cannot be obtained. You will not be able to get hold results. Therefore, SW
This has the drawback that switching errors occur between L and SW2, and switching between R-Y and B-Y is reversed.

For example, S/) such as a dropout shown in arrow A in Fig. 2
Due to the deterioration of J, the period indicated by JOB becomes reversed. This becomes very noticeable on the playback screen. For example, if the color is blue, a red line will appear on the screen.

Particularly in the above-mentioned still image reproducing apparatus, there is a high possibility that deterioration of φ due to dropout or the like occurs in the same H, so that a conspicuous line always appears in the same part.

<Object of the Invention> The present invention has been made in view of the above-mentioned drawbacks, and provides a video signal reproducing device capable of converting a line-sequential signal into line-sequential signals without error even when the S/N ratio is very poor. It is intended to.

<Explanation based on examples> The present invention will be explained below using examples.

FIG. 3 is a diagram showing the main part configuration of a reproducing apparatus according to an embodiment of the present invention. Components in FIG. 6 that are the same as those in FIG. 1 are given the same numbers and their explanations will be omitted. 8 in the figure is a DF triggered by the rising and falling υ of the horizontal synchronization signal (a)
F, 9 is an exclusive OR circuit (EXOR), 10 is a monomulti that is input with a horizontal synchronizing signal and is triggered at the falling edge of the signal, and 11 is a current for the number of pulses of the output signal of the monomulti 10, and preheat settings. A counter that obtains a high-level Q output when counting the number of pulses (for example, 28), 12 is an AND gate that takes the logical AND of the output signals of FiXOR 9 and Mono Multi 10, and 13 is the output of 12 A counter that counts the number of pulses of the signal and obtains a high-level Q output when a preset number of pulses (for example, 27) is counted, and is reset by the Q output of the counter 11. 14 is the counter of the counter 13. DPIP which is triggered when the inertia signal rises and inverts the output, 15 is DF'F
li! which outputs the exclusive OR of the Q outputs of 8 and DI')'14. X0R116 is a DFF whose data input is a signal (PG) input from terminal t5 and synchronized with the rotation of a magnetic sheet (not shown), and which is triggered by the fall of the horizontal synchronization signal (a).
17 is a DFF that is triggered by the falling edge of the output signal of DFF' 16 and uses the output signal of DFF 14 as data input.
1 B is a DF that uses the output signal of DFF 17 as data input.
F 16 is a DFF triggered on the falling edge, 19 is a DFF
This is an EXOR to which the output signals of FfXOR 14 and 18 are input, and the output signals of 20 EXOR 15 and EfXOR 19 are input, and the connection of white Wl and SW2 is switched by the output signal of EXOR 20.

FIG. 4 is a timing chart showing the waveforms of each part of FIGS. 3(a) to (8). The operation of each part of the apparatus shown in FIG. 5 will be explained below using FIG. 4.

A line sequential color difference signal having a DC offset of 2H period as shown in FIG. Figure 4 (i) is a horizontal synchronization signal that is phase-synchronized with a horizontal synchronization signal of a luminance signal (not shown), and these are mono multi 7, mono multi 10, and DF
Figure 4 (→, (
The signals shown in θ) and (n) are obtained, respectively. As is well known, this input signal (a) is separately compensated for when a dropout occurs in the horizontal synchronizing signal due to dropout or the like.

” The output signal (n') of DFF 8 is input to EXOR 15, and the output signal of FiXOR' 15 (Fig. 4 (to)
) is input to InXOR” 20, vxoR2
0o By switching the output jF4 (q) between high level and low level, the connection of swl and SW2 can be switched, and a color difference signal timed between lines can be obtained in the same way as in the configuration shown in Fig. 1. . 4k) When the output signal (q) of EXOR20 is high level, E of SW1 is A, F of SW2
At low level, E of SWI is connected to B and F of 8W2, respectively.

In the above configuration, even if S/H deterioration occurs in the line sequential color difference signal due to dropout or the like as shown by A in FIG. 4(a), the phase of the switching signal (f) of swi and sw2 becomes discontinuous It won't happen. This is because the input signal of EXOR15 is a 2H cycle rectangular wave signal synchronized with the horizontal synchronization signal (
n) to input the other input signal (h) of EXOR15.
This is because unless the other input signal (1) of EXOR2n and BXOR2n is inverted, the phase of the output signal (q) of EXOR20 cannot become discontinuous. Moreover, as will be explained in detail later, it is a signal that is inverted when the counter 13 counts the set number of input pulses (2) for the output signal (h) of DFF1 '4, and also EXOR1
Since the output signal (1) of No. 9 is not inverted if PG is not input, P! The output signal (q) of JOR20 is never inverted.

Next, the output signal (h) of the DFF 14 mentioned above -? E
The operation when the output signal (1) of the XOR 19 is inverted will be described. FIG. 5 is a schematic diagram showing the recording format on the magnetic sheet in this embodiment, and FIG. 6 is a schematic diagram illustrating the general signal processing of the signal joint part in the recording format shown in FIG. 5. It is.

As shown in Figure 5, when the color difference line sequential signal recorded for one field is reproduced as it is (of course also the luminance signal)
o, s H skew will occur. As is well known, this is compensated for by alternately extracting a signal via the %H delay line and a signal not via the %H delay line, and a pseudo signal is generated from such a video signal for one field. I am getting a frame picture.

Further, as shown in FIG. 6, the above-mentioned falling edge of the 9 PG is made to coincide with the signal joint portion (shown in FIG. 5 O). That is, due to the falling of PG, the %H shown in FIG. 6(b) and (C)
Figure 5 (a/) by switching the shifted signal for each field,
An aging line sequential color difference signal shown at (θ) is obtained. However, in the line-sequential color difference signal obtained in this way, the type of color difference signal changes from the second field to the first field as shown in FIG. 6(a).
The transition from one field to another is continuous (alternating), but the transition from the first field to the second field is discontinuous. Therefore, in this case SWI,
The phase of the output signal of IuXOR20, which is the signal for switching SW2, must be made discontinuous.

Figure 7 shows Figures 3 (a) to (q) during field switching.
) is a timing chart showing waveforms of each part. FIG. 7(a) schematically represents a line-sequential color difference signal. As described above, at the switching point r from the first field to the second field, the output signal (0) from the comparator 3 becomes discontinuous.

However, since the output signal (m) of the EXOR 15 is not discontinuous, the output signal (f) of the wxoRq changes to the NO level, and the output signal (e) of the monomulti 10 passes through the AND gate 13, and its falling cycle is counted by the counter 13).

When this count reaches a preset value of 128, a high level output signal is obtained from the counter 13 for a period of 1H (as shown in FIG. 7(0)). This results in DFF 14
is inverted to the output signal (h) of EXOR15, and the output signal of EXOR15 (
m) will also be reversed.

That is, at this timing, the output signal of the EXOR 15 also becomes discontinuous and matches the phase of the output signal (c) of the comparator 3 mentioned above. Accordingly, the output of EiXOR9 changes to low level, and counting by counter 13 also stops.

On the other hand, PG(1) is input to the DFF 16 from the terminal t5. The output signal (j) of DI+'F 16 is D'FII'
The data (Q output of DIPF 17) sampled and held for each field of the output signal (h) of the DFF 14 inputted to 17.18 and inputted to the DFF 17 as data (Q output of DIPF 17) is delayed by one field and further inverted, that is, (
h) Is the signal (k) that preceded by about 128H the DF'? 1
B) is output as Q. Therefore, the output signal CI' of l This is a signal obtained by inverting the output signal (m) of .

In this way, even for discontinuities in the line-sequential color difference signal that occur during the transition from the first field to the second field,
SW1 and SW2 can be switched following each other. Also, except when the output (o) of the comparator and the output (m) of the BIOR 15 do not match with each other for 128H out of 256H by the counters 13 and 14, the Q output (h) of the DFF 14
This does not mean that it is reversed. Therefore, from the first field to the second
BXOR20 output (q
) is unlikely to be discontinuous, and 8W1.13W2 can satisfactorily perform synchronization even for line sequential signals with very poor φ.

Similarly, immediately after the start of playback, PG is used as shown in Fig. 7(k).
Although it is not possible to obtain a waveform as shown in FIG. 1, if the rotation of the PG and the magnetic sheet are synchronized after reproduction of at most several frames, a stable line-sequential color difference signal can be obtained by the above-described operation.

As described above, according to the reproducing apparatus having the configuration shown in FIG. 3, the polarity of the control signal for controlling the switch for synchronizing the line-sequential color difference signals is determined by using two counters and based on the majority voting method. Because of this, dropouts etc.
Erroneous synchronization is not performed even for video signals whose EVN is extremely degraded.

In addition, since the polarity of the control signal for switching the synchronization switch is detected to be discontinuous and the polarity of the control signal is made discontinuous using PG, if the polarity of the control signal becomes incorrect, it will be recorded. Since the period is equal to the phase error between the PG at the time and the PG at the time of reproduction, very accurate switching is possible.

By making the amplifier 2 after sample and hold a tuning amplifier for the frequency of %H, it is possible to provide inertia and to absorb a dropout of about 1 to 2H.

Further, when a dropout occurs, a dropout detection circuit can be used to mute the input to the counter 13 in FIG. 3 during the dropout period, thereby achieving more reliable operation.

Explanation of Effects> As described above in detail using the embodiments, according to the present invention, by statistically processing the result of determining the type of line sequential signal, a very bad line sequential signal of 8/N is eliminated. However, if you obtain a video signal reproducing device that can reproduce the line time without error, it will be distorted.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the main part configuration of a conventional device, FIG. 2 is a waveform diagram showing waveforms of the part shown in FIG. FIG. 4 is a timing chart showing the waveform of the section shown in FIG. 3, FIG. 5 is a schematic diagram showing the recording format on the magnetic sheet in the embodiment shown in FIG. 3, and FIG. FIG. 5 is a diagram for explaining general signal processing at the joint portion of signals in the recording format shown in FIG. 5. FIG. 7 is a timing chart showing the waveform of the section in FIG. tl is a terminal to which a line-sequential color difference signal is input, and t3 and t4 are terminals to which edge-synchronized color difference signals are output, respectively. 1 is a sample and hold circuit, 2 is an amplifier, and 3 is a comparator, which are included in the discrimination means. 11,13
14 is a DFF, and these are included in the processing means. 15, 19, and 20 are respectively lXOR, and these are included in the control means. 8W1 and 8W2 are switches, respectively, and these are included in the synchronization means.

Claims (1)

[Claims] A device for reproducing a video signal including a line sequential signal,
means for synchronizing the line sequential signals; means for determining the type of the preceding line sequential signal for each horizontal synchronization period; means for statistically processing the output of the determining means for each predetermined period; and the processing means. and means for controlling the synchronization means using a control signal obtained based on the output of the video signal reproducing apparatus.