JP2512008B2 - Method and apparatus for removing pseudo sync pulses and / or AGC pulses from a video signal - Google Patents

Description

Description: FIELD OF THE INVENTION This invention relates to a method and apparatus for removing added pulses from a video signal so that the video signal can be copied. More specifically, the present invention relates to a method and process for removing an AGC (positive) pulse added to a video signal or a pseudo sync pulse added to the video signal to inhibit copying of the video signal. It is a thing. The method and apparatus are also useful for the main combination of the added pulses described above.

PRIOR ART In Applicant's U.S. Pat. No. 4,631,603, a television receiver produces a video image from a transformed signal.
It is described that videotape recording performed by the modified signal generally modifies the video signal so that it does not produce an acceptable image.

Techniques for such inhibition rely on the addition of a high level positive pulse (hereinafter referred to as an AGC pulse) to the video signal following the trailing edge of some percentage of the sync pulse. The addition of this pulse occurs during the back porch region of the video signal, ie the blanking interval. These additional pulses cause the video signal level automatic gain control system in the video tape recorder to make an error in the determination of the video signal level, thereby making the recording of the video signal unacceptable.

According to the above technique, what is referred to as a sync pulse may be either a normal sync pulse of the video signal (including both equalization pulses and wide pulses) or a pseudo sync pulse added to the video signal. Pseudo sync pulses lying from the blanking signal level of the video signal to the normal sync chip level are added to the video signal during some lines of the vertical blanking interval. Alternatively, a blanking interval line may be added immediately preceding this vertical blanking interval and / or immediately continuing. These added lines are blanked specifically for the prohibit feature. According to the method of this technique, each pseudo sync pulse is expected to be followed by an AGC pulse (ie, a positive pulse), respectively, while only a portion of the normal sync pulse in the video signal is followed by an AGC pulse. It

[Problems to be Solved by the Invention] The present invention provides a pseudo sync pulse and / or an AGC pulse added from a video signal to prohibit recording of a video signal existing in a predetermined video signal in an arbitrary format. Methods and devices for removal are provided. By such removal, the video signal can be normally recorded.

Accordingly, it is an object of the present invention to provide a method and apparatus for removing pseudo sync pulses and AGC pulses from a video signal which has been modified such that the video tape recording is done on a cleaned video signal.

[Means and Actions for Solving Problems] This method and apparatus can take various different embodiments depending on a predetermined modified video signal. However, the present invention generally provides a normal video recording with any modified video signal having a pseudo sync pulse and / or AGC pulse added for the purpose of inhibiting the recording of the modified video signal. It is what allows it to be done.

Briefly, according to one aspect of the invention, the added AGC pulse is removed from the video signal by selective blanking of the video signal for a predetermined period following the generation of the sync pulse. Similarly, the elimination of the added pseudo sync pulse is achieved by the selective clipping of the negative going pseudo sync pulse based on the detection of the sync pulse with the generation of the line frequency square wave.

The present invention includes both a method and apparatus for effecting removal of one of the aforementioned types of pulses added to interfere with recording or any combination of such "inhibition" pulses.

Other objects and effects of the present invention will become apparent from the following detailed description with reference to the accompanying drawings.

[Embodiment] Referring to the block diagram of FIG.
The video signal input to is transformed by the pseudo sync pulse or the AGC pulse as described above. Buffer amplifier 10
May be a unity gain amplifier and transmits the video signal with its added pulse to the sync tip clamp 12. Sync tip clamp 12 holds the negative voltage sync tip of both the normally occurring sync pulse and the added pseudo sync pulse at a constant negative voltage regardless of changes in average image signal level or amplifier gain level or other bias source. Let
The clamp voltage of sync tip clamp 12 is selected at this point such that the blanking level voltage of the video signal is at or very close to zero volts. This fact requires that the overall video signal level be constant and known.

It will be appreciated by those skilled in the art that clamps actuated during the back porch blanking interval are preferred for synchronous tip clamps. This is due to the fact that the overall video level does not have to be known to ensure the blanking level is at 0 volts. Such an alternative clamping mechanism can be used as a feature of the present invention and is only activated during those back porch intervals where AGC pulses are not present. This added complexity outweighs the advantages of such an alternative clamp. Therefore, the embodiment of FIG. 1 uses a sync tip clamp exclusively as known to those skilled in the art. Other basic devices as known to those skilled in the art, such as sync separators and monostable multivibrators, are shown schematically.

The output of the sync tip clamp 12 is directly fed to one of the inputs of an electrically controlled switch 14. The selection of the output of switch 14 is controlled in accordance with the present invention to blank the positive AGC pulse from the video signal. A full description of this feature is given below. FIG. 2 (a) shows the modified video signal described above which is prohibited from being recorded as output by the sync tip clamp 12. Code 16
Indicates a normal sync pulse, while reference numeral 18 indicates a pseudo sync pulse in accordance with a forbidden modification made to the video signal. Second
Reference numeral 20 in (a), (g), (h), and (i) of the figure indicates color burst information included in a normal video signal having a color formation. The method of the invention is of course equally applicable to non-color video signals.

The dashed box 22 in FIG. 1 represents a bandpass filter, which resonates at the color subcarrier frequency of the color burst information 20 and has a Q value of about 1. This band-pass filter 22 selectively filters the AGC pulse with respect to the color burst information of the band-pass frequency to remove it.
The color burst information is separated from the GC pulse and the filter then supplies this color burst to the second input of switch 14. FIG. 2G shows the input waveform from the bandpass filter 22 to the switch 14. This bandpass filter is of course omitted when the invention is applied to monochrome. The bandpass filter may be of any known form, for example it may comprise an RLC tuning circuit including a resistor 24, a variable inductance 26 and a capacitor 28 as shown in FIG.

Note that FIG. 2 (g) clearly shows that the bandpass filter 22 always outputs a 0 volt signal level except when color burst information is generated.
This blanking signal level is useful for regenerating the AGC pulse free video signal by proper selection of the input of switch 14. This will be described in more detail below.

The modified input video signal from buffer amplifier 10 also drives sync separator 30. The sync separation device 30 is therefore provided with a normal sync pulse 16 as shown in FIG.
And a signal indicating both the pseudo sync pulse 18 is output.
The leading edge of each such sync pulse (both normal and pseudo types) triggers the monostable multivibrator 32. The embodiment of FIG. 1 shows a monostable multivibrator in a 1 microsecond monostable state, but other time intervals are also possible in the present invention. The illustrated embodiment can be implemented for all time intervals.

The output of the monostable multivibrator 32 is shown in Fig. 2 (b).
Shown in waveform, comparison with FIG. 2a clearly shows that both the leading edges of the normal sync pulse 16 and the pseudo sync pulse 18 trigger the monostable multivibrator 32.

As shown in FIG. 1, the 1 microsecond output pulse from the monostable multivibrator 32 drives the sync tip clamp 12 so that it is clamped at a predetermined voltage as described above.

The trigger based on the trailing edge of each sync pulse is used in connection with a monostable multivibrator 34 shown in FIG. 1 as a 5 microsecond monostable multivibrator in the embodiment. FIG. 2 (c) shows the output of the monostable multivibrator 34 and clearly shows that the indicated pulse output of the monostable multivibrator 34 is based on the trailing edge of the sync pulse of FIG. 2 (a). Shows. These 5 microsecond monostable pulses of the monostable multivibrator 34 are switched 14
Used for control of. Switch 14 is configured such that the output of bandpass filter 22 is connected to the output of switch 14 whenever the pulse of monostable multivibrator 34 is high. On the contrary, monostable multivibrator 34
The output of the sync tip clamp 12 is connected to the output of the switch 14 whenever the pulse is low.

As mentioned at the beginning, AGC pulse (or positive pulse)
Occurs only following the sync pulse. Further, as used in Applicant's another application, the AGC pulse occurs only during the 5 microsecond period immediately following the sync or pseudo sync pulse. Therefore, the selection of bandpass filter 22 during the 5 microsecond period immediately following the sync pulse controls the output of switch 14 to remove the AGC pulse 36 of FIG. 2 (a) from the video signal. . The output of switch 14 is shown in the waveform of FIG. 2 (h), indicating that AGC pulse 36 is eliminated at this point. However, the pseudo sync pulse 18 is still present. Also note that the color burst information 20 is output by the switch 14 (see h in FIG. 2). This color burst information is output by the bandpass filter 22 because it occurs during the 5 microsecond period during which the switch 14 is connected to the output of the bandpass filter 22.

The above description of selected portions of FIG. 1 is the remainder of FIG. 1 for removing AGC pulses from a video signal if it is necessary to enable acceptable video recording of the video signal. Shows a device that can be used separately from the circuit of FIG. In other words, if the removal of only the AGC pulse is considered appropriate, then the appropriately buffered output of switch 14 can be used as the video output of the apparatus of FIG. 1 for input to the video recorder.

The remaining circuitry of the FIG. 1 embodiment is primarily used to remove spurious sync pulses from the modified video signal input to buffer amplifier 10. That is, if the video signal transformed by the addition of only the pseudo sync signal (no addition of the AGC pulse) is processed, the switch 14 is always turned on to form a circuit that only removes the pseudo sync pulse. Side position (synchronous tip clamp input position). Of course, the embodiment of FIG. 1 eliminates only the pseudo sync pulse if it is the only type of pulse added to the video signal. Similarly the first
The device in the figure removes only the AGC pulse if only the AGC pulse is added to the normal video signal. However, the entire apparatus of FIG. 1 eliminates both the added pseudo sync pulse and the added AGC pulse, if present.

The video signal from buffer amplifier 10 is switched to effect removal of pseudo sync pulse 18 from the modified video signal.
14 (either via the sync tip clamp 12 or the bandpass filter 22) and additionally by the negative peak clipper circuit 38. Clipper circuit 38
The clipping level can be set variably, and the operational amplifier
It is determined by the voltage level applied to the 40 non-inverting inputs. Diode 42 and resistor 44 form part of the well-known clipping configuration for operational amplifier 40 and resistor 46 and
48 is a voltage level input to complete the clipper circuit 38
Forming a voltage divider with V.

The clipping level of the clipper circuit 38 is the operational amplifier 40.
Can be variably set by a particular selection of the voltage level applied to the non-inverting input of. A digital signal on conductor 50 (or alternatively high and low level analog signals) is used to control the variable setting of the negative voltage clipping of operational amplifier 40. The generation of the switch control signal on conductor 50 is described further below.

The clicker circuit 38 operates as follows. Operational amplifier 40
Does not transmit a signal voltage that is more negative than the voltage at its non-inverting terminal. Therefore, if the voltage at this non-inverting terminal is set to 0 volts, all sync pulses (eg normal sync pulses) and other negative voltages (eg pseudo sync pulses) are removed from the video signal. . However,
If this voltage is set to, for example, about -0.5 volts, the component of the video signal at the output of switch 14
Since nothing is more negative than 0.3 volts, the video signal passes through the clipper circuit 38 undeformed by clipping. See the voltage level in FIG. 2 (a). The operation of the sync tip clamp 12 allows setting of this exact negative voltage limit. Resistors 46 and 48 form a voltage divider circuit which, together with the bias voltage -V, serves to convert the high / low logic voltage signal levels on conductor 50 to 0 and -0.5 volts, respectively.

Therefore, the clipper circuit 38 actually functions as a negative peak clipper circuit only when the signal level on conductor 50 is high. In other words, the "high" signal on conductor 50 is a resistance 4
6,48 and bias voltage -V to convert to a 0 volt input to the non-inverting terminal of operational amplifier 40. During such an input, all voltages that are more negative than 0 volts are clipper circuits.
38 is cut off, that is, clipped and output.

The remaining circuit shown in the lower half of FIG. 1 provides an appropriate pulse train on conductor 50 to cause clipper circuit 38 to remove all negative voltages from the video signal except those originating from normal sync pulses. It is intended to occur. When operated with such a suitable pulse train, the resulting output of clipper circuit 38 is therefore all added pseudo sync pulses and AGC pulse pairs (to allow acceptable video recording of that output). Or individual pulses)
Is a video signal from which is removed.

Referring again to FIG. 1, the voltage controlled oscillator 52 operates at twice the line frequency of the video signal (ie, 31.468 kHz). The voltage controlled oscillator 52 is phase locked by the sync separator 30 by the phase detector and filter 54 by the leading edge of the normal sync pulse output. Divider 56 and 4 microsecond monostable multivibrator 58 operate with phase detector and filter 54 in a well known manner to provide a phase locked loop for voltage controlled oscillator 52. FIG. 2 (d) shows a voltage controlled oscillator passing through a divider 56.
The line frequency square wave output by 52 is shown.
In other words, FIG. 2D shows the output waveform from the divider 56.

The negative edge of the waveform in FIG. 2 (d) triggers the pulse output of the 4 microsecond monostable multivibrator 58.
Figure 2 (e) is a 4-microsecond monostable multivibrator.
The waveform output by 58 is shown. These pulses shown in FIG. 2 (e) sample the leading edge of the sync pulse from sync separator 30 in phase detector and filter 54. The transmission characteristics of the phase detector and filter 54 and the voltage controlled oscillator 52 are selected so that the voltage controlled oscillator 52 is locked in the phase relationship shown by the various waveforms in FIG. The detailed design of this phase locked loop is well known to those skilled in the art and need not be discussed at length here. However, it should be noted that the phase detection system including the monostable multivibrator 58 and the phase detector and filter 54 prevents the phase locked loop from being disturbed by the generation of the pseudo sync pulse 18.

FIG. 3A shows a time sequence of various lines in a predetermined video signal field. FIG. 3B shows a normal sync pulse train in the vertical sync area of image transmission.
FIG. 3g shows the required waveform on conductor 50 of FIG. 1 to allow the pulse shown in FIG. 3b to pass without being clipped by clipper circuit 38. Show. Therefore, the generation of the waveform shown in FIG. 3 (g) is a special feature of the present invention, and is derived as follows as an example. Of course, other circuits for generating the waveform shown in FIG. 3 (g) are included in the technical scope of the present invention.

Voltage controlled oscillator with twice the line frequency
The pulses from 52 are counted by a 10 bit counter 59. The counter 59 is reset to 0 by the output of the field pulse generator 60. Field pulse generator 60 receives input from sync separator 30 and effectively signals the completion of each field of the video signal. FIG. 3 (h) shows a single pulse occurring on the first video signal line shown as line segment 0 in FIG. 3 (a). The data line from counter 59 is read-only memory (RO
M) 62 connected to the address input of this memory, which acts as a state detector in this device. In other words, read-only memory 62 is configured as a 2 × 1024 array and is programmed to provide a signal on conductors 64 and 66 from each of its outputs. These signals selectively correspond to the occurrence of a particular video signal line (or state). The waveforms of the first and second outputs are shown in (e) and () of FIG. 3, respectively. Figure 3 (e)
The signals represented by the waveforms in (f) and (f) are used in conjunction with the remaining logic elements of FIG. 1 to generate the necessary control signals on the aforementioned conductor 50 as shown in FIG. 38
Let the appropriate function be performed.

The time interval as shown in FIG. 3 (a) is associated with the address status in the vertical sync area as shown in connection with the status detector (ROM) 62. Note that the state 0 interval in FIG. 3 (a) corresponds to the field reset pulse in FIG. 3 (h).

A 10 microsecond monostable multivibrator 68 is connected in series with the line between the voltage controlled oscillator 52 and one input of the OR gate 70. The other input of OR gate 70 is connected to the output of AND gate 72. 2 of AND gate 72
This input is supplied with the output of divider 56 (waveform of FIG. 2d) and the first output on conductor 64 of state detector 62 (waveform of FIG. 3e). The output of the OR gate 70 is used as one of the inputs of the AND gate 74, the other input of which is supplied with the second output on the conductor 66 of the status detector 62 (waveform in FIG. 3f). It These two signals are AND gates
An AND operation is performed at 74 to obtain the desired waveform on lead 50 as shown in FIG. Those skilled in the art can easily confirm the output shown in FIG. 3 (g) by comparing the following four waveforms. : FIG. 2 (d) (showing the output of the divider 56); FIG. 3 (e) (showing the output of the state detector 62 on the lead wire 64); FIG. 3 (c) (the OR gate 70).
3 (f) and 4 (b) (the second output of the state detector 62 on lead 66 is shown on two respective time scales). Shown). By using these four basic waveforms and by causing the AND gates 72 and 74 and the OR gate 70 to perform the specified operation, the operational amplifier 40 is enabled to allow the cancellation of the negative going pseudo sync pulse. The waveform shown in FIG. 3 (g) for the proper control of is obtained.

The waveforms of FIGS. 3 (e) and 3 (f) are reproduced in the waveforms of FIGS. 4 (a) and 4 (b) on a much wider time scale. As shown at the bottom of FIG. 2, the entire time frame of the contents of FIG. 2 is equivalent to one video signal line (ie 63.55 microseconds). FIG. 3 shows a number of half lines 515-10. FIG. 4 shows the vertical blanking interval of 20 lines (or 40 half lines or states) in dashed lines, and the boundaries of the time limits shown in FIG. 3 in other dashed lines.

From FIG. 4 the clipping action of the clipper circuit 38 is inoperable for most of the active field except some lines on either side of the vertical blanking interval where pseudo sync pulses may be used. It is recognized that Prevent normal clipping of color information that may be below these blanking levels. Clipper circuit 38 is also disabled during the three lines of the vertical blanking interval during which a normal wide sync pulse is being generated.

Finally, referring to FIG. 2 (i), the buffer amplifier 76
, Which shows that the normal sync pulse 16 and the color burst information 20 are retained, but the pseudo sync pulse 18 and the AGC pulse 36 have been removed, which results in FIG. ) Video signal can be recorded on the video tape.

As mentioned above, in practice it is not necessary to completely remove all AGC pulses, it is sufficient if most of the AGC pulses are removed. Instead, depending on the accuracy of how the original video signal was transformed, it would be sufficient to simply eliminate most of the pseudo sync pulses. As such, several minor variations are possible on the embodiment of FIG. 1 which allows for selective removal of pseudo sync pulses or AGC pulses and combinations thereof. Similarly to those skilled in the art AGC
It is not necessary to remove all of the pulses or pseudo sync pulses, it is necessary to erase some percentage of them, and the small variations of the FIG. 1 embodiment that may be desired are easily recognized, Will be understood. Also, as a functional embodiment of the invention, instead of removing them completely, the amplitude of some of the additional pulses is reduced (eg, the amplitude of the AGC pulse is reduced to 70%).
% Decrease). All such modifications and alterations should be included in the technical scope of the present invention described in the claims.

[Brief description of drawings]

FIG. 1 is a block diagram of an apparatus according to one embodiment of the present invention, and FIGS. 2, 3, and 4 are waveforms and timing diagrams related to the operation of the apparatus of FIG. 10,76 ... Buffer amplifier, 12 ... Synchronous chip clamp, 14 ... Switch, 22 ... Band pass filter, 30 ...
… Synchronous separation device, 32,34,58,68 …… Monostable multivibrator, 38 …… Clipper circuit, 52 …… Voltage controlled oscillator,
54 …… Phase detector and filter, 56 …… Divider, 59…
... Counter, 60 ... Field pulse generator, 62 ... Read-only memory, 70 ... OR gate, 72,74 ... AND gate.

Claims (19)

(57) [Claims] 1. A video signal to which a pseudo sync pulse for prohibiting video recording is added during or near a vertical blanking interval, and a normal sync pulse is detected from the video signal separately from the pseudo sync pulse. Then, a timing signal is obtained from the normal sync pulse, and according to the timing signal, at least some periods of the pseudo sync pulse suppress a selected portion of the video signal, and at other times the video signal is suppressed. By passing without changing substantially including the normal synchronization pulse,
A method for suppressing an added pseudo-sync pulse, characterized in that at least a main part of the pseudo-sync pulse is suppressed to output a regenerated video signal capable of video recording. 2. The step of obtaining the timing signal by distinguishing the normal sync pulse from the pseudo sync pulse to obtain the timing signal includes obtaining the timing signal corresponding to only the normal sync pulse using the line frequency of the video signal. A method as claimed in claim 1 characterized. 3. An AG for inhibiting video recording after a sync pulse including a normal sync pulse and a pseudo sync pulse during or near a vertical blanking interval.
The video signal to which the C pulse is added is supplied, only the color burst signal of the video signal is separated and left, and the signal in which the AGC pulse is suppressed is formed, and the sync pulse of the video signal is detected. A timing signal is obtained from the sync pulse, and the color burst signal is left during the time corresponding to the AGC pulse according to the timing signal, but the signal in which the AGC pulse is suppressed is passed, and the time other than the time corresponding to the AGC pulse is passed. Suppressing the added AGC pulse characterized by obtaining the video signal that enables video recording by suppressing the AGC pulse by allowing the video signal including the synchronization pulse to pass substantially unchanged in time. Method. 4. The step of forming a signal in which the AGC pulse is suppressed includes holding the output at a predetermined value at all times except the color burst signal in the video signal left after being separated. A method according to claim 3, characterized in that 5. The method according to claim 4, wherein the predetermined value is within a range of 0 to 30% of the amplitude value of the attenuated AGC pulse. 6. A video signal to which a pair of pseudo sync pulse and AGC pulse for inhibiting video recording is added during or near a vertical blanking interval, and a pseudo sync with a normal sync pulse of the video signal is supplied. A sync pulse including a pulse is detected, the detected sync pulse is used as a first timing signal to suppress the AGC pulse from the video signal, and a normal sync pulse of the detected sync pulse is simulated. The normal sync pulse is detected separately from the sync pulse to obtain a second timing signal, and at least some periods of the pseudo sync pulse are responsive to the second timing signal to select a selected portion of the video signal. Pseudo-synchronization is achieved by suppressing the signal and allowing the video signal including the normal sync pulse to pass through without any change during other periods. Luz and AG
A method for suppressing a pair of added pseudo sync pulse and AGC pulse, which is characterized in that a pair of C pulses is suppressed and a regenerated video signal which can be recorded is output. 7. The step of suppressing the AGC pulse comprises separating and extracting only a color burst signal from a video signal,
7. A method as claimed in claim 6, characterized in that the retrieved color burst signal is reinserted into the video signal after each normal sync pulse. 8. A device for suppressing a pseudo sync pulse from a video signal to which a pseudo sync pulse for inhibiting video recording is added during or near a vertical blanking interval, the sync pulse being normal to the video signal. Is detected by distinguishing it from a pseudo sync pulse, a logic circuit for obtaining a timing signal by the normal sync pulse detected by the above distinction, and a first operation state for suppressing the input signal. A second operating state of passing the signal substantially unchanged, and operating in the first operating state during a time period including the pseudo synchronizing pulse in response to the timing signal to operate the pseudo synchronizing pulse. Suppressing at least some of them, and operating in the second operating state at times other than the above time without substantially changing the video signal including the normal sync pulse. Device having the selection operation unit for bulk. 9. The apparatus according to claim 8, wherein the selection operation means is a negative peak clipping circuit that removes a negative value component in the first operation state. 10. The synchronizing signal detecting circuit divides a doubled frequency of a synchronizing signal including a voltage control oscillator for transmitting at a frequency twice the line frequency and a normal synchronizing pulse and a pseudo synchronizing pulse. A phase detector that includes a phase detector that compares the phase with a signal, and is phase-locked to the leading edge of only a normal sync pulse, and the logic circuit is responsive to an output from the phase-locked loop to perform the selection operation. Device according to claim 8, characterized in that it supplies said timing signal to means. 11. A method for inhibiting video recording after a sync pulse comprising normal sync pulses and pseudo sync pulses during or near a vertical blanking interval.
A device for suppressing an AGC pulse from a video signal to which an AGC pulse is added, which is a means for forming a signal in which only the color burst signal of the video signal is separated and left and the AGC pulse is suppressed, and a normal video signal A sync signal detection circuit for detecting a sync pulse including a sync pulse and a pseudo sync pulse, a timing signal generation circuit for generating a timing signal from the normal sync pulse and the pseudo sync pulse of the detected sync pulse, and And a second operation state in which the input second signal is passed, and a second operation state in which the input second signal is passed, and during the time corresponding to the AGC pulse in accordance with the timing signal. It operates in the first operation state and leaves the color burst signal but suppresses the AGC pulse and sends the output signal to the output at a time other than the time corresponding to the AGC pulse. Is a device that includes a switch circuit that operates in the second operating state and sends a video signal including the sync pulse to the output. 12. The means for forming a signal in which the AGC pulse is suppressed comprises a filter means for allowing only a color burst signal to pass and for providing a predetermined blanking reference at times other than the time corresponding to the color burst signal. The apparatus of claim 11 including. 13. The apparatus of claim 12, wherein the predetermined blanking criterion has a value within the range of 0 to 30% of the amplitude value of the AGC pulse. 14. A device for suppressing a pair of pseudo sync pulse and AGC pulse from a video signal added with a pair of pseudo sync pulse and AGC pulse for inhibiting video recording during or near a vertical blanking interval. A sync signal detection circuit for detecting a sync pulse including a normal sync pulse and a pseudo sync pulse of the video signal; and a first timing signal generation for generating a first timing signal from the detected sync pulse. A circuit, an AGC pulse suppressing means for suppressing the AGC pulse from the video signal using the first timing signal, and a synchronization for detecting a normal synchronization pulse of the detected synchronization pulses separately from a pseudo synchronization pulse Second timing for obtaining a second timing signal by the signal separation circuit and the normal sync pulse detected by the above distinction A signal generation circuit, a first operating state in which the input signal is suppressed and a second operating state in which the input signal is allowed to pass without substantially changing, and according to the second timing signal. By operating in the first operation state during the time including the pseudo sync pulse, at least some of the pseudo sync pulses are suppressed, and by operating in the second operation state at times other than the time. An apparatus including selection operation means for passing a video signal including a normal synchronizing pulse substantially unchanged. 15. The AGC pulse suppressing means comprises a filter means for passing only a color burst signal and giving a predetermined blanking reference at times other than the time corresponding to the color burst signal, and the first timing signal. According to the switch means for passing the output from the filter means during the time corresponding to the AGC pulse, and for passing the video signal including the synchronizing pulse at the time other than the time corresponding to the AGC pulse. The device of claim 14 in the scope of. 16. The AGC pulse suppression means comprises sync chip clamp means for holding a sync chip of the video signal at a constant negative voltage in response to the sync signal detection circuit. The device of claim 15 in the scope of. 17. The synchronizing signal separation circuit divides the doubled frequency of a synchronizing signal including a normal control pulse and a pseudo-synchronization pulse into a voltage control oscillator for transmitting at a frequency twice the line frequency. A phase detector for phase-locking the signal to the signal, and comprising a phase-locked loop that is phase-locked to the leading edge of the normal sync pulse only, the second timing signal generating circuit responsive to the voltage controlled oscillator. 15. The apparatus of claim 14 including state detection counter means for monitoring the video signal line state and logic means for outputting the second timing signal in response to the voltage controlled oscillator and the state detection counter means. 18. The second timing signal generation circuit comprises:
18. The apparatus according to claim 17, further comprising field pulse generation means for resetting the state detection counter means when one field of the video signal is completed in response to the synchronization signal detection circuit. 19. The apparatus according to claim 14, wherein the selection operation means is a negative peak clipping circuit that removes a negative value component in the first operation state.