JPH0458678A - Circuit for eliminating waveform distortion - Google Patents

Abstract

PURPOSE:To improve the ease of use by providing a means displaying propriety of ghost elimination in addition to a display means for displaying presence of a ghost elimination signal. CONSTITUTION:Part of a video signal SY is extracted from a transversal filter 3 and fed to an overflow detection circuit 221 and a detection signal SOVR going to 1 when the signal SY exceeds the dynamic range of the filter 3 is fed to an OR circuit 224. Moreover, a tap coefficient from a conversion circuit 25 is fed to a detection circuit 222 and a detection signal STAP going to 1 when a tap coefficient reaches an outlier is fed to an OR circuit 224. Moreover, a horizontal synchronizing pulse HD and a clock CK are fed to a detection circuit 223 from a generating circuit 9 and a detection signal SABN going to 1 when number of clocks for one horizontal period is a defective value is fed to the circuit 224. The output of the circuit 224 is fed to an AND circuit 225 and a detection signal SG is fed to the AND circuit 225 and its AND output SAND is fed to a display use LED 42.

Description

[Detailed description of the invention] The explanation will be given in the following order.

A. Industrial application field B. Summary of the invention C Conventional technology D Problems to be solved by the invention E. Means to solve the problem (Figure 1) F. Effect G Example G. First embodiment (Fig. 1) G2 second embodiment (rod 2 diagram) Effect of H 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 ease of use, 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, ghost wave components can be removed from a received video signal as follows.

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

Then, on the receiving side, GC of the received video signal is performed.
The waveforms of the R signal (which includes a ghost wave component) and the GCR signal formed on the receiving side are compared to extract the coast wave component, and in order to eliminate the extracted ghost wave component, the signal is passed through a transversal filter, for example. Control characteristics.

As the GCR signal at this time, a signal 5GCR as shown in FIG. 3 is considered.

That is, in the same figure, I (D is the horizontal synchronizing pulse, B
R5T indicates a burst signal, and the first GCR signal WRB
As shown in FIG. 5A, is a bar waveform located behind the horizontal period, and has a width of 44.7 μsec and a level of 70 IRB. Also, the rise characteristic is 5
This is the ringing characteristic of inX/X.

Further, the 20th GCR signal PDS has a pedestal waveform (0 level), as shown in the same figure.

As shown in FIG. 4A, the 8-field period of the video signal is used as a repeating period, and the first, third, sixth,
18th line or 2nd line of 8th field period
The signal WRB is inserted into the 81st line, and the remaining 2nd and 4th lines
, the signal PDS is inserted into the 18th line or the 281st line of the 5th and 7th field periods, and this G
A video signal with CR signal 5GCR inserted is transmitted.

Then, the first to eighth GCR signals 5GCR are
I-8ll, if the receiving side performs the calculation as shown in FIG. 3, the calculation result will be a signal GCR as shown in FIG. 3C. Furthermore, if there is a ghost, this signal GCR will also include the ghost wave component Sg.

Therefore, ghost removal can be performed from the signal GCR (and Sg) resulting from this calculation.

In this case, the burst signal BRST, the color signal and the horizontal synchronization pulse I ([1 is
Since they are in phase with each other, the burst signal BR3T, the color signal, and the horizontal synchronization pulse HD are each canceled out when calculating the signals S, ~S.

Therefore, the signal GCR (and ghost wave component Sg) resulting from the calculation does not include the burst signal BRST, color signal, and horizontal synchronizing pulse, so it is difficult to eliminate so-called front ghosts and rear ghosts, waveform equalization, etc. It can be used for up to 45 microseconds.

Moreover, false detection does not occur even for long ghosts up to about 80 μsec.

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

That is, (1) shows the video detection circuit of the television receiver, and the above-mentioned GCR signal 5GCR is output from this detection circuit (1).
A color composite video signal SY to which 1 is added is extracted.

Further, (9) indicates a clock signal forming circuit, in which the video signal SY from the detection circuit (7) is supplied to the synchronization separation circuit (7), horizontal and vertical synchronization pulses are taken out, and these pulses are ).

Furthermore, the signal SY from the detection circuit (1) is supplied to the burst gate circuit (8) and a burst signal is extracted.
This burst signal is supplied to the forming circuit (9).

In this manner, various timing signals and a clock CK synchronized with the horizontal and vertical synchronizing pulses and the burst signal signal are formed in the forming circuit (9), and these signals are supplied to the respective circuits.

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

Then, the video signal SY from the detection circuit (1) is
One sample is supplied to the D converter (2), for example, 8
It is converted into a bit digital video signal SY. Then, this signal SY is supplied to a D/A converter 4) through a transversal filter (3) of, for example, 640 stages (640 chips), where it is converted into the original analog video signal SY, and this signal SY is converted into the original analog video signal SY. It is taken out to the terminal (5).

In this case, in the detection circuit (10), the GCR
A ghost wave component is detected from the signal 5GCR, and the passing characteristic of the filter (3) is successively corrected based on the detection output to remove the ghost wave component as described above.

That is, the calculation shown in FIG. 4B can be rewritten as shown in FIG.
This indicates that it is sufficient to integrate the R signals 5GCR in order.

Therefore, the digitized video signal SY from the adder circuit (6) is supplied to the gate circuit (11) to extract the GCR signal 5GCR (including the previous and subsequent detection periods), and this signal 5GCR is transferred to the buffer memory IJ ( 12) is supplied to the GCR of that field period for each field period.
Signal 5GCR is retained.

Then, the GCR signal 5GCR of this memory (12) is
It is supplied to an arithmetic circuit (21). This calculation circuit (21)
Although the following circuits (22) to (26) are actually constructed by the microcomputer (20) and software, they are represented by hardware here.

Then, in the arithmetic circuit (21), the memo 'J (12
) is sequentially added or subtracted in accordance with the formula shown in FIG. is extracted, and these signals GCR and Sg are supplied to the subtraction circuit (22), and at the same time, a reference waveform signal GCR (Fig. 3C) is extracted from the reference GCR signal forming circuit (23), and this signal GCR is subtracted. It is supplied to the circuit (22).

Therefore, from the subtraction circuit (22), the received signal G
A ghost wave component Sg of CR is extracted. Note that this ghost wave component Sg is also an error component from which the ghost cannot be removed.

Since the signal GCR has a bar waveform, in order to make it a pulse response, the ghost wave component Sg is supplied to a differentiating circuit (24) to form a differentiated pulse Pg, and this pulse Pg is supplied to a converting circuit (25). .

In this conversion circuit (25), the pulse Pg is converted into a signal ST representing the correction amount of the tap coefficient (tap gain) of the filter (3), and this signal ST is supplied to the filter (3). The pass characteristic of the filter (3) is controlled so that the cancellation signal SC (this is a cancellation signal for the ghost wave component of the GCR signal 5GCR) extracted from the GCR signal 5GCR cancels and removes the ghost wave component included in the GCR signal 5GCH. be done.

Then, since such processing is repeated thereafter, the characteristics of the transversal filter (3) are adjusted little by little, that is, the characteristics of the filter (3) are successively corrected,
The GCR signal 5 gradually converges to a characteristic that removes the ghost wave component Sg of the GCR.

Then, when the characteristics of filter (3) converge sufficiently, G
The ghost wave component Sg of the CR signal 5GCR is reduced to a negligible level, but 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 at the terminal (5).

Note that at this time, the GCR signal G from the arithmetic circuit (21)
CR (and its ghost wave component Sg) is detected by the detection circuit (2
6), the presence or absence of the GCR signal GCR is detected, and the detection signal SG is supplied to the LED (31) for display.
supplied to

In this way, the GCR signal 5GC is added to the received video signal SY.
When R is added, the detection signal SG causes the L
E D (31) is lit, which causes the GCR signal 5G
It is displayed that CR is being received or that the ghost removal circuit is operating.

Literature: 1989 National Conference Journal of the Television Society of Japan "Ghost Cancellation Standard Signal System" D Problems to be Solved by the Invention By the way, in the ghost cancellation circuit as described above,
Depending on the state of the ghost, the tap coefficients of the transversal filter (3) may not be able to converge correctly, resulting in an even worse playback screen.

Furthermore, even when ghosts are severe, appropriate ghost removal cannot be performed. Furthermore, when a video signal other than a standard video signal, such as a VTR playback signal, is supplied, the time axis is not very stable, so the timing of the detection circuit (10) and microcomputer (20) is shifted, and normal ghost removal is not possible. In some cases, the operation is not performed and the playback screen becomes worse.

Therefore, when the ghost removal circuit cannot operate normally, it turns off the LED (31) even if the GCR signal 5GCR is added to the video signal SY.
D (31) is blinking to indicate that the ghost wave cannot be removed.

However, by simply turning off the LED (31), it is not possible to distinguish whether the GCR signal 5GCR is not added to the video signal SY or whether the ghost wave cannot be removed.

Furthermore, if the LED (31) is blinked, the user does not know what the user is doing, and it is difficult to convey the meaning that ghost waves cannot be removed. For example, it may be mistaken that the GCR signal 5GCR is added or not added.

This invention attempts to solve these problems.

E. Means for Solving the Problem Therefore, in accordance with the present invention, in correspondence with the embodiments described later, a detection circuit (26) for detecting whether the received video signal SY contains the GCR signal 5GCR is provided. The display is controlled by the output of this detection circuit (26), and the LED (31) displays whether or not the received video signal SY contains the GCR signal 5GCR, and the waveform distortion of the received video signal SY. Discrimination circuits (221) to (225>) that determine whether the component can be removed, and another circuit that is controlled by the output of this determination circuit and displays whether the waveform distortion component of the received video signal SY can be removed. L E
D (42) is provided.

F Effect: The state of the received video signal SY and the operating state of the coast removal circuit are correctly communicated to the user.

G Example G1 First Example In FIG. (41). Then, the control signal 3w is supplied from the microcomputer (20) to the switch circuit (41),
The output signal of this switch circuit (41) is taken out to the terminal (5).

Also, a part of the video signal SY is taken out from the transversal filter (3) and the overflow detection circuit (2
21), a detection signal 5DVR that becomes "l" when the signal SY overflows the dynamic range of the filter (3) is taken out, and this signal 5OVR is supplied to the OR circuit ('224).

Furthermore, the tap coefficient from the conversion circuit (25) is supplied to the detection circuit (222), and a detection signal 5TAP that becomes "1" when the tap coefficient becomes an abnormal value is extracted.
This signal 5TAP is supplied to the OR circuit (224).

Further, the horizontal synchronizing pulse HD and the tally clock CK are supplied from the forming circuit (9) to the detection circuit (223>), and a detection signal 5ABN which becomes "1" when the number of clocks in one horizontal period is an abnormal value is taken out. This signal 5ABN is supplied to the OR circuit (224).

Then, the output of this OR circuit (224) is the AND circuit (
At the same time, the detection signal SG from the detection circuit (26) is also supplied to the AND circuit (225), and the AND output 5AND is used as the display LED (42).
supplied to

Note that the circuits (221) to (225) described above are similar to the circuit (221) to (225).
1) to (26) are composed of the same components 1, a microcomputer (20), and software, but here they are expressed by hardware.

Further, a trigger circuit (43) is provided, and from this trigger circuit (43), channels are switched, power is turned on, ghost removal key operation by the user, VTR playback operation, and TV broadcast reception is performed from the VTR playback mode. At the time of switching to the mode, etc., the trigger pulse Pt
is taken out, and this pulse Pt is supplied to the microcomputer (20) as a start signal for setting the filter (3) tutting coefficient.

The pulse Pt is also supplied to the conversion circuit (25),
When starting to set a tap coefficient, the tap coefficient is cleared.

According to such a configuration, during steady state, 3W is "0", and the switch circuit (41) is connected to the converter (4) as shown in the figure.
) side is connected.

Therefore, during normal operation, this ghost removal circuit has a configuration equivalent to that shown in FIG. 5, and performs the same ghost removal operation.

However, if the channel is changed at any time, the power is turned on, the ghost removal key is operated, the VTR is played, etc., the trigger circuit (43) is sent to the microcontroller (
20) is supplied with a trigger pulse Pt. Then, based on this pulse Pt, the microcomputer (20) selects SW-“
1", the switch circuit (41) is connected in the opposite way to the diagram, and the video signal SY from the detection circuit (1) is connected to the terminal (5).
It is taken out.

In addition, in the microcomputer (20), the GCR signal 5GC
The process for removing the ghost wave component is started using R, and the characteristics of the filter (3) are adjusted little by little as described above, that is, the characteristics of the filter (3) are successively modified, and the GCR signal 5GCR gradually converges to a characteristic that removes the ghost wave component Sg.

In this case, since SG="1", the LED <31
) lights up to display that the GCR signal 5GCR is added to the video signal SY.

Also, at this time, if everything is normal, 5OV
R="O", 5TAP="0", 5ABN="O"
”, so 5AND = “0” and L E D (4
2) is not lit, and the user is informed that the ghost wave removal process is being performed normally.

However, for example, if the tap coefficient of the transversal filter (3) cannot be properly converged because it cannot deal with the ghost state, 5TAP = "1", so 5AND
- becomes "1" and the LED (42) lights up.

Therefore, the user is informed that ghost waves cannot be removed normally.

Also, for example, if the ghost is severe and cannot be removed properly, 5OVR-“1” will be obtained, so 5A
ND- becomes "1", the LED (42) lights up, and it is displayed that the ghost wave cannot be removed normally.

Furthermore, for example, when a VTR playback signal is supplied, but its time axis is not very stable, 5ABN="
1” and 5AND = “1”, so L E
D (42) lights up to indicate that ghost waves cannot be removed.

Note that when the GCR signal 5GCR is not added to the video signal SY, SG="0", so the signal 5O
Regardless of VR, 5TAP, or 5ABN, LED (
42) does not light up.

Also, during the period when the characteristics of the filter (3) are set, 3W = "1", and the video signal SY from the detection circuit (1) is output as is to the terminal (5), so this setting During this period, even if the level of the video signal SY from the filter <3) is disturbed, this will not adversely affect the display (not shown).

Thus, according to the present invention, GCR is added to the video signal SY.
When signal 5GCR is added, this is L E
D(31) is displayed, but in this case, especially according to the present invention, a ghost state is detected and the detection signal 5A is
Since ND is supplied to LED (42), GCR
When there is a ghost that cannot be properly removed by the signal 5GCR, this is displayed by the LED (42).

Therefore, when the GCR signal 5GCR is added to the video signal SY, but the ghost state exceeds the ability to remove it, this can be reliably notified to the user. For example, there is no misunderstanding that the GCR signal 5GCR is added or not added.

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

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

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

Further, the signal ST from the detection circuit (10) is transmitted through the filter (
52) and (54) as a control signal for their pass characteristics.

Therefore, since the subtraction circuit (51) and filter (52) are configured in a feedforward type loop,
A video signal SY from which adjacent ghost wave components including front ghosts have been removed is taken out from the subtraction circuit (51).

In addition, since the subtraction circuit (53) and the filter (54) are configured in a feedback type loop, the subtraction circuit (53)
43), the video signal SY from which the long ghost wave component has been removed is extracted.

Therefore, the video signal SY from which the close ghost wave component and the long ghost wave component have been removed can be taken out at the terminal (5).

H Effects of the Invention According to this invention, the state of a ghost is detected and the detection signal 5AND is supplied to the LED (42), so when a ghost cannot be removed normally with the GCR signal 5GCR, this can be used. Displayed by LED (42).

Therefore, when the GCR signal 5GCR is added to the video signal SY, but the ghost state exceeds the ability to remove it, this can be reliably notified to the user. For example, there is no misunderstanding that the GCR signal 5GCR is added or not added.

[Brief explanation of drawings]

Figures 1 and 2 are system diagrams of an example of this invention, and Figures 3 to 51! 1 is a diagram for explaining the same. (1) is a video detection circuit, (2) is an A/D converter, (
3) is a transversal filter, (4) D/A
:1 inverter, (10) is a detection circuit, (11) is a gate circuit, (12) is a buffer memory, (20) is a microcomputer, (221) to (223) are detection circuits,
(31) and (42) are LEDs. Wave mouth diagram 3

Claims (1)

[Claims] A received video signal is supplied to a transversal filter, a GCR signal is extracted from the output signal of the transversal filter, a waveform distortion component is extracted from the extracted GCR signal, and a waveform distortion component is extracted from the extracted waveform distortion component. In the waveform distortion removal circuit, the video signal from which the waveform distortion component has been removed is extracted from the transversal filter by controlling the pass characteristics of the transversal filter based on the received video signal, wherein the GCR signal is included in the received video signal. a detection circuit for detecting whether or not the GCR signal is included in the received video signal; It has a determination circuit that determines whether the waveform distortion component can be removed or not, and another display means that is controlled by the output of the determination circuit and displays whether or not the waveform distortion component of the received video signal can be removed. Waveform distortion removal circuit.