JP2822268B2 - Circuit for removing waveform distortion - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The description will be made in the following order.

A Industrial Field of Use B Summary of the Invention C Prior Art D Problems to be Solved by the Invention E Means for Solving the Problems (FIG. 1) F Function G Embodiment G ₁ First Embodiment (1st Embodiment) FIG. G ₂ Second embodiment (FIG. 2) H Effect of the invention A Industrial application field The present invention relates to a circuit for removing waveform distortion of a video signal.

B. Summary of the Invention The present invention improves usability, for example, by providing means for displaying whether or not ghost removal is possible in a ghost removal circuit, in addition to means for displaying the presence or absence of a ghost removal signal.

C. Prior Art In a television receiver, the following method may be used to remove a ghost wave component from a received video signal.

That is, on the transmission side, a ghost canceling reference signal (hereinafter, referred to as a GCR signal) is added to the video signal.

Then, on the receiving side, the GC of the received video signal is
The R signal (including the ghost wave component) and the GCR signal formed on the receiving side are compared in waveform to extract the ghost wave component, and pass through a transversal filter so that the extracted ghost wave component disappears. Control characteristics.

Then, a signal SGCR as shown in FIG. 3 is considered as the GCR signal at this time.

That is, in the figure, HD is the horizontal synchronization pulse, BRST
Represents a burst signal, and the first GCR signal WRB has a bar waveform located at the back of the horizontal period, a width of 44.7 μs, and a level of 70 IRE, as shown in FIG. . The rising characteristic is a ringing characteristic of sinX / X.

Further, the second GCR signal PDS is, as shown in FIG.
ぺ Destal waveform (0 level).

Then, as shown in FIG. 4A, the eight-field period of the video signal is a repetition period, and the eighteenth line or the eighteenth field period of the first, third, sixth, and eighth field periods is used.
The signal WRB is inserted in the 281 line, and the 18th line or the 18th line in the remaining second, fourth, fifth, and seventh field periods is inserted.
The signal PDS is inserted into 281 lines, and the video signal with the GCR signal SGCR inserted is transmitted.

Then, the first to eighth GCR signals SGCR are transmitted to the signals S _{1 to} S _8.
Then, if the receiving side performs an operation as shown in FIG. B, the operation result is a signal as shown in FIG. 3C.
GCR. If there is a ghost, this signal GCR also includes the ghost wave component Sg.

Therefore, the ghost can be removed from the signal GCR (and Sg) of the operation result.

In this case, 8 field period apart the burst signal BRST, the color signal and the horizontal synchronization pulses HD, since each of phase with each other, when calculating the signal S ₁ to S _8, the burst signal BRST, the color signal and the horizontal synchronizing pulse HD Are offset each other.

Therefore, since the signal GCR (and the ghost wave component Sg) of the operation result does not include the burst signal BRST, the color signal, and the horizontal synchronization pulse HD, the so-called front ghost and rear ghost removal and waveform equalization are performed. Up to 45 μs can be handled. In addition, erroneous detection does not occur even for a long ghost up to about 80 μsec.

FIG. 5 shows an example of a ghost removal circuit using this GCR signal SGCR.

That is, (1) shows a video detection circuit of the television receiver, and the color composite video signal SY to which the above-mentioned GCR signal SGCR is added is extracted from the detection circuit (1).

Further, (9) shows a clock signal forming circuit, in which the video signal SY from the detecting circuit (7) is supplied to a sync separating circuit (7) to extract horizontal and vertical sync pulses, and these pulses are formed by the forming circuit (9). ). Further, the signal SY from the detection circuit (1) is supplied to a burst gate circuit (8) to extract a burst signal, and this burst signal is supplied to a formation circuit (9).

In this way, in the formation circuit (9), various timing signals and clocks CK synchronized with the horizontal and vertical synchronization pulses and the burst signal signal are formed, and these signals are supplied for their avoidance.

At this time, if the frequency of the clock CK is four times the color subcarrier frequency, one horizontal period is 910 clocks.

The video signal SY from the detection circuit (1) is A / D
One sample is supplied to the converter (2) and converted into a digital video signal SY of, for example, 8 bits. This signal SY is supplied to a D / A converter (4) through a transversal filter (3) of, for example, 640 stages (640 taps) and converted into an original analog video signal SY. It is taken out in (5).

In this case, a ghost wave component is detected from the GCR signal SGCR in the detection circuit (10), and the pass characteristic of the filter (3) is successively corrected by this detection output to remove the ghost wave component as described above. .

That is, the operation shown in FIG. 4B can be rewritten as shown in FIG.
This indicates that the R signal SGCR should be accumulated in order.

Then, the digitized video signal SY from the adding circuit (6) is supplied to the gate circuit (11) and the GCR signal SGC
R (including the preceding and following detection periods) is taken out and this signal SGC
R is supplied to the buffer memory (12), and the GCR signal SGCR in the field period is held every field period.

Then, the GCR signal SGCR of the memory (12) is supplied to the arithmetic circuit (21). The arithmetic circuit (21) and the following circuits (22) to (26) are actually constituted by a microcomputer (20) and software, but are represented here by hardware.

Then, in the arithmetic circuit (21), the GCR signal SGCR held in the memory (12) is sequentially added or subtracted in each field period according to the equation of FIG. A certain signal GCR and a ghost wave component Sg are taken out, these signals GCR and Sg are supplied to a subtraction circuit (22), and a reference GCR signal forming circuit (23) outputs a reference waveform signal GCR (FIG. 3C). The signal GCR is taken out and supplied to a subtraction circuit (22).

Therefore, from the subtraction circuit (22), the received signal GC
The ghost wave component Sg of R is extracted. Note that the ghost wave component Sg is also an error component that could not be removed from the ghost.

Since the signal GCR has a bar waveform, a ghost wave component Sg is supplied to a differentiating circuit (24) to obtain a differentiated pulse Pg in order to obtain a pulse response.
Supplied to

Then, in this conversion circuit (25), the pulse Pg is converted into a signal ST of a correction amount of the tap coefficient (tap gain) of the filter (3), and this signal ST is supplied to the filter (3), and the filter (3) Signal SC extracted from
The pass characteristic of the filter (3) is controlled such that (this is a cancel signal for the ghost wave component of the GCR signal SGCR) cancels out and removes the ghost wave component included in the GCR signal SGCR.

Then, since such processing is repeated,
The characteristics of the transversal filter (3) are adjusted little by little, that is, the characteristics of the filter (3) are sequentially corrected, and gradually converge to the characteristics of removing the ghost wave component Sg of the GCR signal SGCR.

When the characteristics of the filter (3) sufficiently converge,
The ghost wave component Sg of the GCR signal SGCR is reduced to a negligible level. At this time, the ghost wave component of the original video signal SY is also at a negligible level.

Therefore, the video signal SY from which the ghost wave component has been removed is taken out from the terminal (5).

At this time, the GCR signal GCR from the arithmetic circuit (21) is
The ghost wave component Sg is supplied to a detection circuit (26) to detect the presence or absence of the GCR signal GCR, and the detection signal SG is supplied to a display LED (31).

Thus, when the GCR signal SGCR is added to the received video signal SY, the LED (31) is turned on by the detection signal SG, whereby the GCR signal SGCR is received, or the ghost removal circuit operates. Is displayed.

Literature: 1989 National Convention of the Institute of Television Engineers of Japan "Ghost cancellation reference signal system" D Problems to be solved by the invention By the way, in the ghost removal circuit as described above, depending on the state of ghost, the transversal filter (3) is The tap coefficients may not converge correctly, resulting in a terrible playback screen.

Also, when the ghost is severe, the ghost cannot be properly removed. Furthermore, when a video signal other than the standard video signal, for example, a VTR playback signal is supplied, its time axis is not very stable, so that the timing of the detection circuit (10) or the microcomputer (20) is shifted and normal ghost removal is performed. The operation may not be performed and the reproduction screen may be terrible.

Therefore, when the ghost elimination circuit cannot operate normally, the LED (31) is turned off or the LED (31) is turned on and off, even if the GCR signal SGCR is added to the video signal SY. Indicates that it cannot be removed.

However, if the LED (31) is simply turned off, it cannot be determined whether the GCR signal SGCR is not added to the video signal SY or the ghost wave cannot be removed.

Also, when the LED (31) is blinked, the user does not know what he is doing, and it is difficult to convey the meaning that the ghost wave cannot be removed. For example, it may be mistaken that the GCR signal SGCR is added or not added.

The present invention is intended to solve such a problem.

E Means for Solving the Problems Therefore, in the present invention, according to an embodiment described later, a detection circuit (26) for detecting whether or not the received video signal SY includes the GCR signal SGCR; The display is controlled by the output of the detection circuit (26), and an LED (31) for indicating whether or not the received video signal SY includes the GCR signal SGCR, and a waveform distortion component of the received video signal SY are removed. Discrimination circuits (221) to (225) for judging whether or not it is possible, and another LED (42) which is controlled by the output of the discrimination circuit and indicates whether or not the waveform distortion component of the received video signal SY can be removed. And are provided.

F Function The state of the received video signal SY and the operation state of the ghost removal circuit are correctly transmitted to the user.

G Embodiment G ₁ First Embodiment In FIG. 1, a video signal SY from a D / A converter (4) is supplied to a switch circuit (41), and a video signal SY from a detection circuit (1) is supplied to the switch circuit (41). Switch circuit (41)
Supplied to The control signal Sw is supplied from the microcomputer (20) to the switch circuit (41), and the output signal of the switch circuit (41) is taken out to the terminal (5).

Further, a part of the video signal SY is extracted from the transversal filter (3), and the overflow detection circuit (22)
The detection signal SOVR which is supplied to 1) and becomes "1" when the signal SY overflows the dynamic range of the filter (3) is taken out, and this signal SOVR is output to the OR circuit (224).
Supplied to

Further, the tap coefficient from the conversion circuit (25) is supplied to the detection circuit (222), and a detection signal STAP which becomes "1" when the tap coefficient becomes an abnormal value is extracted.
STAP is supplied to the OR circuit (224).

Further, the horizontal synchronizing pulse HD and the clock CK are supplied from the formation circuit (9) to the detection circuit (223), and the detection signal becomes “1” when the number of clocks in one horizontal period is an abnormal value.
The SABN is extracted and the signal SABN is supplied to the OR circuit (224).

The output of this OR circuit (224) is the AND circuit (2
25), the detection signal SG from the detection circuit (26) is supplied to the AND circuit (225), and the AND output SAND is supplied to the display LED (42).

The circuits (221) to (225) described above correspond to the circuits (21) to (21).
Like (26), it is composed of a microcomputer (20) and software, but is represented here by hardware.

Further, a trigger circuit (43) is provided. From the trigger circuit (43), channel switching, power-on,
The trigger pulse Pt is extracted when the user operates the ghost removal key, performs the VTR playback operation, or switches from the VTR playback mode to the television broadcast reception mode. The pulse Pt is output to the microcomputer (20). Is supplied as a start signal for setting the tap coefficient of the filter (3).

The pulse Pt is also supplied to the conversion circuit (25), and when the setting of the tap coefficient is started, the tap coefficient is cleared.

According to such a configuration, Sw = “0” in a normal state, and the switch circuit (41) is connected to the converter (4) as shown in FIG.
Connected to the side.

Therefore, in a steady state, this ghost removal circuit
The configuration is equivalent to that of FIG. 5, and the same ghost removal operation is performed.

However, when the channel is switched, the power is turned on or the ghost removal key is operated, and the VTR playback operation is performed at any time, the microcomputer (2) is output from the trigger circuit (43).
0) is supplied with a trigger pulse Pt. Then, based on the pulse Pt, the microcomputer (20) sets Sw = "1", the switch circuit (41) is connected in the opposite direction as shown, and the video signal SY from the detection circuit (1) is connected to the terminal (5). Is taken out.

In the microcomputer (20), processing for removing a ghost wave component is started using the GCR signal SGCR.
As described above, the characteristics of the filter (3) are adjusted little by little, that is, the characteristics of the filter (3) are sequentially corrected,
It gradually converges to the characteristic of removing the ghost wave component Sg of the GCR signal SGCR.

In this case, since SG = "1", the LED (31) is turned on to indicate that the GCR signal SGCR is added to the video signal SY.

Also, at this time, if everything is normal, SOVR
= “0”, STAP = “0”, SABN = “0”, so SAND = “0”, the LED (42) does not turn on, and the user is informed that the ghost wave removal processing is performed normally. Be told.

However, for example, when the tap coefficient of the transversal filter (3) cannot be properly converged because the ghost state cannot be dealt with, STAP = “1”, so that SAND = “1”, and the LED (42) is turned on. Therefore, the user is informed that the ghost wave cannot be removed normally.

Also, for example, when the ghost is so bad that proper ghost removal cannot be performed, SOVR = “1”, so that SAND =
It becomes “1” and the LED (42) lights, indicating that ghost wave removal cannot be performed normally.

Further, for example, when a playback signal of a VTR is supplied but its time axis is not very stable, SABN = “1” and SAND = “1”, so that the LED (42) is turned on and the ghost wave Is displayed that cannot be removed.

When the GCR signal SGCR is not added to the video signal SY, SG = “0”, so that the signals SOVR, STAP, SA
The LED (42) does not light up regardless of BN.

Also, while the characteristics of the filter (3) are set, Sw = “1”, and the video signal from the detection circuit (1) is output.
Since SY is output to the terminal (5) as it is, even if the level of the video signal SY from the filter (3) is disturbed during this set period, this does not adversely affect the display (not shown).

Thus, according to the present invention, when the GCR signal SGCR is added to the video signal SY, the LED (31) is displayed. In this case, particularly according to the present invention, the ghost state is detected. Since the detection signal SAND is supplied to the LED (42), when the ghost cannot be normally removed by the GCR signal SGCR, this is displayed by the LED (42).

Therefore, although the GCR signal SGCR is added to the video signal SY, when the ghost state exceeds the removal capability, it is possible to reliably notify the user of this.
For example, it cannot be mistaken that the GCR signal SGCR is added or not added.

G2 _Second Embodiment FIG. 2 shows another connection example of the transversal filter (3).

That is, the video signal SY from the A / D converter (2)
Is supplied to a first subtraction circuit (51), and the first
Is supplied to a subtraction circuit (51) through a transversal filter (52).

The output signal of the subtraction circuit (51) is further supplied to a second subtraction circuit (53), and the output signal of the subtraction circuit (53) is passed through a second transversal filter (54). (53), and the output signal of the subtraction circuit (53) is supplied to the D / A converter (4).

Also, the signal SY from the detection circuit (10) is applied to the filter (5
2) and (54) are supplied as control signals for the passing characteristics.

Therefore, since the subtraction circuit (51) and the filter (52) are configured as a feedforward loop, the video signal SY from which the nearby ghost wave component including the previous ghost has been removed is extracted from the subtraction circuit (51). .

Also, since the subtraction circuit (53) and the filter (54) are configured as a feedback loop, the subtraction circuit (4
From 3), the video signal SY from which the long ghost wave component has been removed is extracted.

Therefore, the video signal SY from which the near ghost wave component and the long ghost wave component have been removed can be extracted from the terminal (5).

H According to the present invention, the ghost state is detected and the detection signal SAND is supplied to the LED (42).
For ghosts that cannot be removed properly with CR,
This is indicated by the LED (42).

Therefore, although the GCR signal SGCR is added to the video signal SY, when the ghost state exceeds the removal capability, it is possible to reliably notify the user of this.
For example, it cannot be mistaken that the GCR signal SGCR is added or not added.

[Brief description of the drawings]

FIGS. 1 and 2 are system diagrams of an example of the present invention, and FIGS. 3 to 5 are diagrams for explanation thereof. (1) is a video detection circuit, (2) is an A / D converter,
(3) is a transversal filter, (4) is a D / A converter, (10) is a detection circuit, (11) is a gate circuit, (1)
2) is a buffer memory, (20) is a microcomputer, (221) to (223) are detection circuits, (31) and (42) are LE
D.

Continuation of the front page (72) Inventor Takayu Nagamine 6-7-35 Kita-Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation (58) Field surveyed (Int.Cl. ⁶ , DB name) H04N ^5/ 14- 5/217

Claims (1)

(57) [Claims] 1. A received video signal is supplied to a transversal filter, a GCR signal is extracted from an output signal of the transversal filter, a waveform distortion component is extracted from the extracted GCR signal, and based on the extracted waveform distortion component. A waveform distortion removing circuit configured to control a pass characteristic of the transversal filter to extract a video signal from which a waveform distortion component has been removed from the transversal filter, wherein the received video signal includes the GCR signal. A detection circuit for detecting whether or not the display is controlled by an output of the detection circuit, a display means for displaying whether or not the GCR signal is included in the received video signal, and a waveform of the received video signal A discriminating circuit for discriminating whether the distortion component can be removed, and an output of the discriminating circuit. And a separate display means for controlling whether or not the waveform distortion component of the received video signal can be removed.