JPS6125386A - Reproducing device of video signal - Google Patents

Abstract

PURPOSE:To synchronize satisfactorily a line sequential signal in terms of normal reproduction state period by deciding a polarity of a control signal for controlling a switch used for synchronization of a line sequential signal with use of two counters based on a view like a majority decision. CONSTITUTION:A line sequential color difference signal having a DC component DC offset by 2H period is inputted from a terminal t1, and supplied to a sample and hold circuit 1. Then an output signal (n) of a DFE8 is inputted to an EXOR 15, and its output signal (m) is inputted to an EXOR20. When its output signal (q) is switched to high and low levels, the connection between switches SW1 and SW2 is switched, thereby obtaining line-synchronized color difference signal. At this time, when a polarity of a control signal for controlling the switches SW1 and SW2 used for synchronizing the line sequential color difference signal is decided with use of counters 11 and 13 based on a view like a majority decision, the erroneous synchronization will not be executed with respect to a video signal whose S/N is markedly deteriorated due to drop-out, etc.

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 two types of signals are line-sequentially recorded, a direct current component (DC) offset and a frequency offset are performed with a 2H period, or a flag signal is added with a 2H period. However, when the type of line sequential signal subjected to these processes is to be determined by 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 DC 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 (g).

In FIG. 1, tl is a terminal to which a line-sequential color difference signal obtained from a reproduced video signal is supplied, and t2 is a terminal to which a horizontal synchronizing signal obtained from a 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 l, 3 is a comparator that compares the output of the amplifier with a predetermined level, and 4 is a horizontal synchronizing signal ( Second
6 is an IH (63,556p
sec) delay line, 7 is a monomulti, which is triggered by the horizontal synchronizing signal (d) and forms a signal as shown in Figure 2 (b), SWI and SW2 are when the output of DFF4 is high level, the E of SWI is A, F of SW2 are connected to C, E of SWI is connected to B, and F of SW2 is connected to C when the level is low, and the line-to-line timed color difference signals are supplied to t3 and t4, respectively.

Now, the line sequential color difference signals are red (R) - luminance (Y) and blue (B
)-luminance (Y)@, and R-Y has a higher center level than B-Y and is recorded with a line offset. At this time, if R-Y is being reproduced at a certain H level, during that period, the signal sampled and held at the falling edge of the output signal (b) of the monomulti 7 is at a high level. Therefore, the output signal (e) of the DFF4 at the next H becomes high level. That is, if the output signal of the IH delay line 6 is R-Y, E of SW1 is connected to A, and the synchronized R-Y is output from the terminal t3. Similarly, the terminal t
4 outputs the synchronized B-Y.

However, when obtaining a line-sequential color-difference signal from a line-sequential color-difference signal with the above-described configuration, if there is some kind of flaw in the line-sequential color-difference signal at the sampling timing, such as S/N deterioration due to dropouts, it is difficult to obtain the correct DC offset. Sample hold results cannot be obtained. Therefore SWI
This has the drawback that switching errors occur in SW2 and SW2, and switching between RY and BY is reversed. For example, the second
Due to S/N deterioration such as dropout shown by arrow A in the figure, the period shown by B becomes reversed, which is very noticeable on the playback screen. For example, in the case of blue-color, a red line will appear on the screen.Especially in the above-mentioned still image playback device, there is a high possibility of S/N deterioration due to dropouts etc. at the same H, so always A noticeable line will appear in the same area.

<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. The purpose is 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 as an embodiment of the present invention. Components in Figure 3 that are similar to those in Figure 1 are given the same numbers and explanations are omitted.
is a DFF triggered by the falling edge of the horizontal synchronization signal (d),
9 is an exclusive OR circuit (EXOR), 10 is a mono multi-channel that receives a horizontal synchronizing signal and is triggered at the falling edge of the horizontal synchronizing signal;
1 counts the number of pulses of the output signal of the monomulti IO, and when the first number of pulses set in advance (for example, 28) is counted, the Q1 output (0) of high level is set in advance in the same way. a counter that obtains a high-level Q2 output when counting the number of second pulses (for example, 36); 12;
is an AND gate that takes the logical product of the output signals of EXOR9 and monomulti IO, and 13 is an AND gate that calculates the AND gate of the output signals of EXOR9 and MonoMulti IO, and 13 is an AND gate that counts the number of pulses of the output signal of 12, and a preset third number of pulses (for example, 27) is counted. When the Q3 output (p) is at high level, the fourth pulse number (p), which is set in advance, is
For example, when counting 18), a high-level Q4 output is obtained, and the counter 14 is reset by the output Q1 or Q2 of the counter 11, and the counter 14 is triggered when the output signal Q3 or Q4 of the counter 13 rises. An inverting DFF, 15, is an EXOR that outputs the exclusive OR of the Q outputs of DFF8 and DFF14, and 16 is a signal (PG) inputted from a terminal t5 and synchronized with the rotation of a magnetic sheet (not shown).
) is the data input, and 17 is a DFF that is triggered by the falling edge of the horizontal synchronizing signal (d).DFF is triggered by the falling edge of the output signal of 16 and uses the output signal of DFF14 as the data input.18 is the output signal of DFF17. is a DFF that is triggered by the falling edge of DFF16, and 19 is DFF as a data input.
The outputs of FF14 and FF18 are input, and 6EXOR120 is an EXOR to which the output signals of EXOR15 and EXOR19 are input.
1, and the connection of SW2 can be changed. SW3.
SW4 is a switch that is input from a terminal t6 and is switched by a TRF signal that is at a high level only during a transition period, as will be described later. In addition, SW3 outputs the Q1 output of the counter 11 when the TRF signal is at a low level, and outputs Q2 when the TRF signal is at a high level.
The outputs are respectively supplied to the clear terminals of the counters 13. SW4 also controls the Q of the counter 13 when the TRF signal is at low level.
3 output, Q4 output when /＼ level is DFF14 respectively.
Supplied to the clock pulse input terminal of the

FIG. 4 is a timing chart showing the waveforms of each part of FIGS. 3A to 3S, and the operation of each part of the apparatus shown in FIG. 3 will be explained below using FIG. A line-sequential color difference signal having a D'C offset in 2H synchronization as shown in FIG. FIG. 4(d) shows a horizontal synchronizing signal that is phase-synchronized with the horizontal synchronizing signal of the luminance signal (not shown), and when this signal is input to the monopletia, monomulti 10, and DFF 8, respectively, the signal shown in FIG. 4(b) is obtained.

The signals shown in (e) and (n) are obtained, respectively. As is well known, this input signal (d) is separately compensated for when a dropout occurs in the horizontal synchronizing signal due to dropout or the like.

The output signal (n) of DFF8 is input to EXOR15,
The output signal of EXORl 5 (shown in Figure 4(m)) is E
Input to XOR20, output signal (q) of EXOR20
By switching between the low level and the low level, S
By switching the connections of WI and SW2, it is possible to obtain line-to-line timed color difference signals in the same manner as in the configuration shown in FIG. In other words, when the output signal (q) of EXOR20 is /\I level, S
WI E is A, SW2 F is C, when low level sw
E of i is connected to B, and F of SW2 is connected to D, respectively.

In the above configuration, even if S/N degradation 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 (g) of SWI and SW2 becomes discontinuous. It won't happen.

This is because a 2H synchronized square wave signal (n) synchronized with the horizontal synchronization signal is used as the input signal of EXOR15, and
This is because unless the other input signal (h) of the XOR 15 and the other input signal (h) of the EXOR 20 are inverted, the phase of the output signal (q) of the EXOR 20 cannot become discontinuous. Moreover, as will be explained in detail later, when the TRF signal is at a low level, the output signal (h) of the DFF 14 is a signal that is inverted when the counter 13 counts the set number of input pulses (27), and also the EXOR l
PG is not input for output signal (AC) of 9)
Since C± is not inverted in the case, the output signal (q) of EXOR 20 is not inverted due to several H dropouts.

Next, the output signal (h) of DFF14 mentioned above and EXOR1
The operation when the output signal (sentence) of No. 9 is inverted will be explained. FIG. 5 is a schematic diagram showing the recording format on the magnetic sheet in this embodiment, and FIG. 6 is a schematic diagram for explaining the general signal processing of the signal joint part in the recording format shown in FIG. It is a schematic diagram.

As shown in FIG. 5, when the color difference sequential signal recorded for one field is reproduced as it is (of course, the luminance signal as well) is 0.
This results in 5H skew, as is well known.)
Compensation is made by alternately extracting signals that pass through the SH delay line and signals that do not pass through the SH delay line, and a frame image is obtained in a pseudo manner from such a video signal for one field. .

Further, as shown in FIG. 6, the falling edge of the PG mentioned above and the signal joint portion (shown in t145, C) are made to coincide.

That is, by switching the ylH shifted signals shown in Figures (b) and (C) with the falling edge of PG for each field, the signals shown in Figure 6 (d)
), line-sequential color difference signals as shown in (e) are obtained. However, in the line-sequential color difference signal obtained in this way, the change in the type of color difference signal is continuous (alternating) when moving from the second field to the first field, as shown in FIG. 6(d). , the transition from the first field to the second field becomes discontinuous, so in this case SWI
, the phase of the output signal of EXOR20, which is the signal for switching to 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. 147
Figure (a) schematically represents a line-sequential color difference signal. As described above, at the switching point from the $1 field to the second field, the output signal (C) from the comparator 3 becomes discontinuous. However, the output signal (m) of EXORl5
is not discontinuous, so the output signal (f) of EXOR9
changes to high level, and the output signal of mono multi 10 (fl
l) passes through the AND gate 13, and its falling edge is counted by the counter 13.

When this count value reaches a preset value (128), a high level output signal is obtained from the counter 13 during the IH period (shown in FIG. 147 (0)), which causes the output signal of the DFF 14 ( h) and EXORl 5
The output signal (m) of is also inverted. 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 EXOR 9 changes to a roll bell, and counting by counter 13 also stops.

On the other hand, PG(i) is input to the DFF 16 from the terminal t5. The output signal (j) of 0FF18 is input to DFF17 and 18, and DFF1 is inputted as data to DFF17.
The data obtained by sampling and holding the output signal (h) of 4 for each field (Q output of DFF17) is delayed by 1 field, and the inverted signal, that is, the signal (k) which precedes (h) by about 128H, is output from DFF18 by Q. is output as Therefore, the output signal (also) of EXOR19 is at a high level from the inversion of the Q output (k) of DFF18 until the inversion of the Q output (h) of DFF14, and during this period, the output signal (q) of EXOR20 is the output signal (q) of EXOR15 ( m) is the inverted signal.

Like this t! Even when the line-sequential color difference signal is discontinuous during transition from the i41 field to the second field, SWI and SW2 can be tracked and switched. In addition, the output of the comparator (0) and the output of EXORl5 (m
) does not match, the Q output of DFF14 (
h) is never inverted, therefore, it is unthinkable that the output (q) of EXOR20 becomes discontinuous except when transitioning from the first field to the second field, and it is a line sequential signal with very poor S/H. Also, synchronization can be performed satisfactorily by SWI and SW2.

The above describes the operation when the TRF signal (1) is at low level. The TRF signal (1) is at a low level in a steady reproduction state, and is at a high level in a transient state such as when switching reproduction tracks or starting reproduction.

If the same operation as described above was performed when the TRF signal (1) is at a high level, SWI, SW
When the two switches are completely opposite.

That is, even when the phase of the output signal (q) of the EXOR 20 is determined, the output signal (m) of the EXOR 15 remains in the same phase until the counter number of the counter 13 reaches the set value. , the phase of the switching control signal (q) of SW2 is reversed, so the types of output signals (R-Y and B-Y) to terminals t3 and t4, which are synchronized and outputted as line-sequential signals, are They will be replaced during this period.

Therefore, in the embodiment shown in FIG. 3, when the TRF signal (1) is at a high level, that is, in a transient state, the Q2 output of the counter 11 is supplied to the clear terminal of the counter 13, and the Q2 output of the counter 11 is supplied to the clock of the DFF 14. The Q4 output of the counter 13 is supplied to the pulse input terminal. In other words, during a transient state, SWI is performed for 18H out of 36H.

If SW2 is switched in the opposite direction, the transfer output signal (q) of EXOR20 is reversed so that normal line time can be achieved.

As described above, according to the reproducing apparatus having the configuration shown in FIG. 3, the switch for synchronizing the line-sequential color difference signals is controlled by using two counters and a majority decision method during the steady reproduction state period. Since the polarity of the control signal is determined, erroneous synchronization will not be performed even for video signals whose S/N ratio is extremely deteriorated due to dropouts or the like.

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 the PG, if the polarity of the control signal is incorrect, it will be detected when recording. Since the period is equal to the phase error between the PG at the time of playback and the PG at the time of reproduction, very accurate switching is possible.

Furthermore, in the transient state period, since the period for performing majority voting is shortened, it is possible to quickly and accurately calculate the line time.

Incidentally, 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 dropout of about 1 to 2H.

Further, when a dropout occurs, a dropout detection circuit is used to mute the input to the counter 13 in FIG. 3 during the dropout period, thereby making it possible to perform more reliable operation.

Furthermore, the TRF signal is a signal that distinguishes between a steady state and a transient state by some method, but if it becomes a steady state instantly after being in a transient state, the TRF signal will be
It is preferable to keep it at a high level for about the H period, which allows for more reliable operation.

Explanation of effects> As explained above in detail using the examples, according to the present invention, both in the steady regeneration state and in other states,
By varying the period required for statistical processing, line-sequential signals can be synchronized extremely well in each state.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing the main part configuration of a conventional playback device, Fig. 2 is a timing chart showing the waveform of the numbered part in Fig. 3, and Fig. 3 is a main part of a playback device as an embodiment of the present invention. A block diagram showing the configuration, Fig. 4 is a timing chart showing the waveform of the numbered part in Fig. 3, Fig. 5 is a schematic diagram showing the recording format of the magnetic sheet t in this embodiment, and Fig. 6 is Fig. 5. FIG. 7 is a timing chart showing the waveform of the numbered part in the third figure. SWI and SW2 are switches included in the synchronization means, respectively. SW3. SW4 is a switch, 11.13 is D and FF, and these are included in the processing means. 14
is DFF, 15°19.20 is EXOR1, and these are included in the control means. (3) L H (4J L-1111------------
--------11111111cJ)L-1------
−−−−−−−−−−−−−−−−−−−−−−−−−(
4) L
---11---(S)

Claims (1)

[Scope of Claims] An apparatus for reproducing a video signal including a line-sequential signal, comprising: means for synchronizing the line-sequential signal; and means for determining the type of the line-sequential signal for each horizontal synchronization period. Means for statistically processing the output of the discriminating means every first predetermined period in the steady regeneration state and every second predetermined period set shorter than the first predetermined period before entering the state. and means for controlling the synchronization means using a control signal obtained based on the processing means.