JPH02250467A - Ghost detection circuit - Google Patents

Abstract

PURPOSE:To make ghost detection stable by selecting either output signal of the output signals of 1st and 2nd ghost cancellation reference signal (GCR) signal extraction pulse generating circuits for ghost elimination so as to check whether or not a vertical synchronizing signal separator circuit of a television signal is correctly operated. CONSTITUTION:When a pulse to fetch a GCR signal is generated by using 4fsc, it cannot cope with the case with occurrence of a discontinuous vertical synchronizing signal caused at the changeover of a camera. Then a vertical synchronizing confirmation circuit 119 monitors the discontinuity of the vertical synchronizing signal and when discontinuity takes place, a 1st GCR signal extraction pulse generating circuit 116 is used to generate again a GCR signal extraction pulse at a normal position and then a 2nd GCR signal extraction pulse generating circuit 116 is used to generate the GCR signal extraction pulse. Thus, the system copes with even the discontinuity of the vertical synchronizing signal to detect ghost stably at all times.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a ghost detection circuit used in a ghost removal device such as a television receiver.

[Conventional technology]

In a television receiver, when radio waves arriving directly from the transmitting antenna (desired waves) and radio waves reflected from buildings, etc. (reflected waves) are simultaneously received by the receiving antenna, an image due to the desired waves and the reflected waves are generated. A so-called ghost occurs, where the image appears shifted.

Such ghosts are a major factor in deteriorating the image quality of television receivers, and various methods have been attempted in the past to remove or prevent ghosts. One of them is a ghost removal device using a transversal filter in the video band. (Unexamined Japanese Patent Publication No. 55-
149523, etc.) This method connects a large number of delay elements in series, each having a minute delay time determined by the highest frequency component included in the video signal, weights the output signals of each delay element with a coefficient circuit, and then adds them. This is to obtain a ghost compensation signal that removes ghosts.

Generally, ghost detection is performed by differentiating the leading edge of the vertical synchronization signal (Japanese Patent Laid-Open No. 55-149523, etc.), but in this case, there are the following problems.

(1) Due to insufficient band of the synchronization signal, high-frequency components of ghosts (contours and color ghosts) remain unerased.

(2) Due to the deterioration of linearity at the relay station, even if the ghost of the synchronization signal can be completely removed, the ghost of the video signal remains.

In order to solve this problem, the Broadcasting Technology Development Council is currently using a standard signal for ghost removal (hereinafter referred to as
Consideration has been given to transmitting a GCR signal (referred to as a GCR signal) by inserting it into the superimposed blanking period of a television signal, and detecting ghosts using this GCR signal on the television receiver side.

The following two signals have been proposed as candidates for the GCR signal.

(a) As shown in Fig. 12, 8 fields are considered as one cycle, and the 1st, 5th, and 6.8th fields have a waveform f1. f5. f6. fB, black level signals f2. f4. f5. f7 is transmitted from the broadcasting station, and the receiver side performs the calculation shown in the following equation.

(rl-rs)+(f6-rl)+(f!5-f7)+(f8-f4) (
1) As a result, the par waveform f1. f5. f6. The horizontal synchronizing signal and its ghost component, the color burst signal and its ghost component, and the ghost component of the previous line signal included in the waveform f2. f4. f5. f7, and a bar waveform as shown in FIG. 13a is obtained. By differentiating this waveform, ghosts up to the delay time τW can be detected, as shown in bK of the figure.

(b) Of the waveforms shown in Fig. 12 f1 to f8, fl and f3
゜f5. Insert f7 only into odd fields. Or
f2. f4. f6. Insert f8 into the even field.

On the receiver side, the calculation shown in equation (2) is performed when inserting into an odd field, and the calculation shown in equation (3) is performed when inserting into an even field.

(fi-f5)+(f'!-f7)
(2) (f6-f2)+(1-f4)
(3) As a result of the calculation of equation (2) or equation (3), a waveform as shown in FIG. 15 can be obtained as in the case of (a).

[Problem to be solved by the invention]

However, in the GCR signal described above, as shown in (1) to (3) 2, signals sent for each different field are added and subtracted to create a signal for ghost detection, so it is necessary to extract each signal accurately. be.

In other words, if the sample position of the GCR signal shifts, as shown in Figure 14, after performing the calculations of equations (1) to (3), the ghost of the horizontal synchronization signal and burst signal will be completely removed. This results in false detection of ghosts.

An object of the present invention is to provide a GCR signal extraction circuit that can accurately extract the above-mentioned GCR signal.

[Means to solve the problem]

The above purpose is.

A field discrimination circuit that determines whether the field of a television signal is an odd number or an even number, a first GCR signal sampling pulse generation circuit that counts the number of horizontal synchronization signals and generates a first GCR signal sampling pulse, and a color subcarrier. Signal multiplied by 4 (hereinafter referred to as 4fso)
a second GCR signal sampling pulse generation circuit that counts the number of GCR signal sampling pulses and generates a second GCR signal sampling pulse; an output of one of the output signals of the first and second GCR signal sampling pulse generation circuits; Vertical synchronization line i! that checks whether the switch circuit that selects the signal and the superimposed synchronization signal separation circuit for television signals are operating correctly. circuit, at the start of ghost detection or in the vertical synchronization confirmation circuit,
When it is determined that the first direct phase signal separation circuit is not operating correctly, K confirms that the field is an odd field by the field discrimination circuit, and selects the output signal of the first GCR signal sampling pulse generation circuit. However, from the next field onward, this is achieved by providing a switch control circuit that controls the switch circuit to select the output signal of the second GCR signal sampling pulse generation circuit.

[Effect]

At the start of ghost detection, counting horizontal synchronization signals using the first GCR signal sampling pulse generation circuit,
GCR during the horizontal synchronization signal period in which the GCR signal is inserted.
generates a signal sampling pulse, and then the second GC
By using an R signal sampling pulse generation circuit and counting 4fso to generate a GCR signal sampling pulse,
A stable GCR signal sampling pulse can be obtained for the reasons described below.

Horizontal synchronization signal (H
), vertical synchronization signal (V), and color printing carrier wave (fso) K have the following relationship.

4faom910-1i,,,525-455 @V Therefore, since 4fso is an integral multiple of the horizontal synchronization signal (H) and vertical synchronization signal (V), it is difficult to determine in which horizontal synchronization signal period the GCR signal is inserted. However, by counting 4fao, the GCR signal sampling pulse can always be obtained at a fixed position.

For example, if a GCR signal is inserted at the 19th H of an odd field, 4fso is set to 525, 455, 2.
It is sufficient to create a pulse that captures the KGCR signal every time it is counted.

However, when the pulse for capturing the GCR signal is created using 4fIIo as described above, there is a problem that it cannot cope with discontinuity of the vertical synchronization signal that occurs when switching cameras, etc.

Therefore, the vertical synchronization confirmation circuit monitors the discontinuity of the vertical synchronization signal, and if discontinuity occurs, the first GOR signal sampling pulse generation circuit is used to generate the GαR signal sampling pulse again at the correct position. If a GCR signal sampling pulse is then generated by the 20th GCR signal sampling pulse generation circuit, discontinuity of the vertical synchronizing signal can also be dealt with.

〔Example〕

Embodiments of the present invention will be described below with reference to FIG.

FIG. 1 is a block diagram illustrating an embodiment of a ghost detection circuit (100) according to the present invention. In the same figure, 110
is the 4fso input terminal, 111 is the vertical synchronization signal (V, 5Y
NC) input terminal, 112 is the horizontal synchronization signal (H, 5YNC)
) input terminal, 113 is a reset signal input terminal indicating when the system is started, 114 is a GCR signal extraction pulse output terminal, 115 is a field discrimination circuit, 116 is the first GC
R signal sampling pulse generation circuit, 117 @2 GCR signal sampling pulse generation circuit, 118 switch circuit, 11
9 is a switch control circuit, and 119 is a vertical synchronization confirmation circuit.

The operation of the present ghost detection circuit 100 will be explained using FIG. 2. However, it is assumed that the GCR signal is inserted in both fields at the 19th H of the horizontal synchronization period.

The field discrimination circuit 115 has a vertical synchronization signal input terminal 1.
The vertical synchronizing signal shown in FIG. 2(b) inputted from 11 (
V, 5YNG) and the horizontal synchronization signal (H, 5YNC) shown in FIG.
), a signal is created which is High in odd fields and Low in even fields, as shown in FIG. 2(d).

The first GCR signal sampling pulse generation circuit 116 generates the GCR signal sampling pulse shown in FIG. 2(a) at 19H of the horizontal synchronization period by counting the number of horizontal synchronization signals from the vertical synchronization signal.

The second GCR signal extraction pulse generation circuit 117
4 input from the 4fso input terminal 110 based on the output signal of the GCR signal sampling pulse generation circuit 116 of
Repeat the operation of counting fso by a predetermined number until you reach an odd number.
The GCR signal sampling pulse shown in FIG. 2 (Q) is repeatedly generated in even fields.

The switch circuit 118 selects the output signal of the first GCR signal sampling pulse generation circuit 116 (a side) or the output signal of the second GCR signal sampling pulse generation circuit 117 (b side) according to the output signal of the switch control circuit 120. Choose one.

The switch control circuit 120 performs the following two operations.

(1) When the system is started, the switch circuit 118 is closed to the a side by a reset signal (RIilSET) inputted from the reset signal input terminal 113 indicating when the system is started. After confirming from the output signal of the field discrimination circuit 115 that the output signal of the first GCR signal sampling pulse generation circuit 116 is output from the GCR signal sampling pulse in the odd field, the output signal of the field discrimination circuit 115 is determined as follows. After showing even fields,
The switch circuit 118 is closed bflK and maintained in that state.

(2) When the output signal of the vertical synchronization confirmation circuit 119 indicates discontinuity of the vertical synchronization signal, the switch circuit 118 is
Close it to the side and perform the operation (1) above.

The first ffi is the field discrimination circuit 11 shown in FIG.
5 is a block diagram showing an example of the configuration of No. 5; FIG. In the same figure,
Blocks with the same numbers as in FIG. 1 indicate the same functional blocks; 310 is a vertical synchronizing signal shaping pulse generation circuit;
311 is an AND circuit, 312 is a field discrimination signal generation circuit, and 620 is a field discrimination signal output terminal.

Using FIG. 4, the field discrimination circuit 11 shown in FIG.
The operation of step 5 will be explained.

The vertical synchronization signal shaping pulse generation circuit 510 generates 4fso input from the 4fao input terminal 110 from the rising edge of the vertical synchronization signal (V, 5YNC) shown in FIG. 4(a) input from the vertical synchronization signal input terminal 111. By counting approximately 455 times, a superimposed synchronization signal shaping pulse whose pulse width shown in FIG. 4(0) is approximately half of the horizontal synchronization period is generated.

The AND circuit 311 receives the output signal of the vertical synchronization signal shaping pulse generation circuit 310 and the horizontal synchronization signal (H, 5Y
NG) and H only in the case of an even field.
, 5YNC.

The field discrimination signal generation circuit 512 includes an AND circuit 31
Depending on whether there is a H, 5YNC pulse in the output signal of 1,
It is determined whether the field is odd or even, and as shown in FIG. 4(d), Hlgh in the odd field.

In an even field, a field discrimination signal that becomes Low is generated.

FIG. 5 shows the first GCR signal sampling pulse generation circuit 11.
FIG. 6 is a block diagram showing an example of the configuration of No. 6; In the same figure,
Blocks with the same numbers as in FIG. 1 indicate the same functional blocks, 510 is a superimposed synchronization signal shaping pulse generation circuit, 5
11 is a counter, 512 is a decoder, 513 is the first G
This is a CR signal extraction pulse output terminal.

The operation of the first GCR signal sampling pulse generation circuit 116 shown in FIG. 5 will be described below with reference to FIGS. 6 and 7.

The superposition synchronization signal shaping pulse generation circuit 510 counts around 700 4fao from the rise of the vertical synchronization signal (V, 5YNC) shown in FIGS. 6 and 7(b), and (o) Generate a superimposed synchronization signal shaping pulse whose pulse width indicated by the IC is approximately 1/2 or more and H or less (H is the horizontal synchronization period).

The counter 511 is reset at the falling edge of the superimposed synchronization signal shaping pulse, and then the horizontal synchronization signal (H, 5YN
C) Count.

As shown in the video signals of FIGS. 6 and 7, the decoder 512 decodes 15 of the output signals of the counter 511 when the GCR signal is inserted at the 191st position, as shown in the video signals of FIGS. A first GCR signal sampling pulse shown in Figure (d) is generated.

FIG. 8 shows the second GCR signal sampling pulse generation circuit 11.
7 is a block diagram illustrating an example of the configuration of FIG. In the same figure,
Blocks with the same numbers as in FIG. 1 indicate the same functional blocks, 810 is an edge detection circuit, 811 is a switch,
812 is a counter, 813 is a pulse generation circuit, and 814 is a second GCR signal extraction pulse output terminal.

The edge detection circuit 810 detects the rising edge of the output signal of the first GCR signal extraction pulse generation circuit 116.

The switch 811 causes the switch circuit 118 shown in FIG. 1 to output the output signal (a
When the side) is selected, the a side is selected, and when the output signal of the second GCR signal sampling pulse generation circuit 117 (b side) is selected, the b side is selected.

The counter 812 counts 4fso for 265H (H is the horizontal synchronization period). Here, the odd field 19
From the Hth to the 19th even field is 263)! ,
Since there is an interval of 262H from the 19th H of the even field to the 19th H of the odd field, the initial value of the counter 812 is set by the output signal of the counter 812 to (1) 0 for an odd field (2) 910 for an even field. By doing so, it is possible to select a horizontal synchronization period in which a GCR signal is always inserted in both odd and even fields. However, when the switch 811 is closed to the a side, the above initial value is loaded with the output signal of the edge detection circuit 810, that is, the output signal of the first GCR signal sampling pulse generation circuit 116.

The pulse generation circuit 815 generates a second GCR signal sampling pulse by making the pulse width of the output signal of the counter 812 approximately IH (H is the horizontal synchronization period).

FIG. 9 is a block diagram showing an example of the configuration of the vertical synchronization confirmation circuit 119. In this figure, blocks with the same numbers as in FIG. 1 indicate the same functional blocks. 910 is a counter, 911 is a decoder, 912 is a correct/incorrect judgment period pulse generation circuit, 913 is a correct/incorrect judgment signal generating circuit, and 914 is a correct/incorrect judgment signal output terminal.

The operation of the vertical synchronization confirmation circuit 119 will be explained using FIG. 10.

The counter 910 is reset by the output signal (first or second GCR signal sampling pulse) of the switch circuit 118, and counts horizontal synchronization signals from the 20th H of the horizontal synchronization period.

The decoder 911 decodes 262 and 264 when the output signal of the field discrimination circuit 115 indicates an odd field, and 263 and 265 when it indicates an even field, and decodes (0) * (d) and ( 0), (d
) Outputs the signal shown in

The correct/incorrect determination period pulse generation circuit 912 includes a decoder 911
From the output signal of , a signal shown in (e) K in FIG. 10 is output.

The correct/incorrect determination signal generating circuit 915 determines whether or not there is a vertical synchronizing signal within the period of the output signal of the correct/incorrect determining period pulse generating circuit 912, and if there is, the signal is set to Hlgh.

If there is no such signal, a low signal is output.

FIG. 11 is a block diagram showing an example of the configuration of the switch control circuit shown in FIG. 1. In the figure, blocks with the same honorifics as in Figure 1 indicate the same functional blocks.
01 is a NAND circuit, 1102 is an inverter circuit, 1
104 is an AND circuit, 1105 is a 7-lip-flop circuit, and 1106 is a switch control signal output terminal.

The NAND circuit 1101 operates before the start of ghost detection (R1
11131'l' signal 113 is Low) or when discontinuity of the vertical synchronization signal occurs (the output signal of the vertical synchronization confirmation circuit 119 is Low), the flip-flop circuit 1105
By clearing the switch control signal is set to Low.
to cause the switch circuit 118 to select the first GCR signal extraction pulse.

The AND circuit 1104 and the inverter circuit 1102 detect the fall of the GCR signal sampling pulse 114 when the output signal of the field discrimination circuit 115 indicates an odd field (the output signal is Hlgh), and pass the signal to the 7-lip-flop circuit 1105. After the start of ghost detection (RE811T signal 113
When the vertical synchronization signal is normal (algh) and the vertical synchronization signal is normal (the output signal of the vertical synchronization confirmation circuit 119 is Low), after the first GCR signal sampling pulse of the odd field occurs, the switch control signal is set to Hlgh, and after that, The switch circuit 118 is caused to select the second GCR signal sampling pulse.

In the embodiment described above, at the start of ghost detection or when discontinuity of the vertical synchronization signal occurs, after selecting the first GCR signal sampling pulse of the odd field, the second GCR signal sampling pulse is selected.
The reason for selecting the CR signal sampling pulse is as follows: (1) Discontinuity in the vertical synchronization signal at the broadcasting station is likely to occur when switching from an even field to an odd field because television broadcasts are sent in interlaced format. (2) When GCR signals are sent in both fields, it is easier to perform subsequent processing if the starting field for capturing the 8-field signal is determined in advance.

Note that when the GCR signal is inserted only in odd fields, the embodiment described above is configured so that the output signal of the second GCR signal sampling pulse generation circuit 117 is generated only in odd fields. It goes without saying that it is sufficient to do this by (taking the AlID of the output signal of the second GCR signal extraction pulse generation circuit 117 and the output signal of the field discrimination circuit 115).

Furthermore, in the case where the GCR signal is inserted only in even fields, in the embodiment described above, the output signals of the first GCR signal sampling pulse generation circuit 116 and the second GCR signal sampling pulse generation circuit 117 are For details, it is necessary to configure it so that it occurs only in odd-numbered fields, and to set it to Hlgh, which is the input terminal on the output signal side of the field discrimination circuit 115 of the AND circuit 1104 of the switch control circuit 120 shown in FIG. There is no need to explain it.

〔Effect of the invention〕

As described above, according to the present invention, since the GCR signal sampling pulse is generated using 4fso, the pulse generation position can be stabilized. In addition, even if there is discontinuity in the vertical synchronization signal that occurs when switching cameras at a broadcasting station,
Since a vertical synchronization confirmation circuit is provided and the GCR signal sampling pulse is regenerated using the horizontal synchronization signal and then generated using 4fso, malfunctions in sampling the GCR signal can be prevented.

Therefore, it is possible to provide a ghost detection circuit that always stably detects ghosts based on GCR signals.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the ghost detection circuit according to the present invention, FIG. 2 is a waveform diagram illustrating the operation of the ghost detection circuit shown in FIG. A block diagram showing a configuration example, FIG. 4 is a waveform diagram explaining the operation of the field discrimination circuit in FIG. 3, and FIG.
A block diagram showing an example of the configuration of the first GOR signal extraction pulse generation circuit shown in the figure, FIGS.
A waveform diagram explaining the operation of the GCR signal sampling pulse generation circuit, FIG. 8 is a block diagram showing an example of the configuration of the second GCR signal sampling pulse generation circuit in FIG. 1, and FIG. 9 is a superposition of FIG. 1. Block diagram showing a configuration example of a synchronization confirmation circuit, No. 10
11 is a block diagram showing an example of the configuration of the switch control circuit shown in FIG. 1; FIG. 12 is a waveform chart showing an example of the GCR signal; FIG. 13 is a waveform diagram showing the ghost detection method using the GCR signal of FIG. 12, and FIG. 14 is a waveform diagram showing the GCR signal after subtraction when the sampling phase is shifted. 100...Ghost detection circuit 110...4fsa input terminal 111...Vertical synchronization signal input terminal 112...Horizontal synchronization signal input terminal 113...Reset signal input terminal 114...GCR signal sampling pulse output terminal 115・
...Field discrimination circuit 116...First GCR signal sampling pulse generation circuit 117...Second GCR signal sampling pulse generation circuit 11B...Switch circuit 119...Vertical synchronization confirmation circuit 120...Switch Control circuit 310... Vertical synchronization signal shaping pulse generation circuit 311.
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Claims (1)

[Claims] 1. Ghost removal reference signal (hereinafter referred to as GCR) inserted into any horizontal period of the vertical line period of a television signal.
In the ghost detection circuit that detects ghosts added to television signals using (signal), there is a field discrimination circuit that determines whether the field of the television signal is odd or even, and a field discrimination circuit that counts the number of horizontal synchronization signals. a first GCR signal sampling pulse generation circuit that generates a first GCR signal sampling pulse; and a second GCR signal that counts the number of signals phase-locked to the color subcarrier and generates a second GCR signal sampling pulse. a sampling pulse generation circuit and the first and second GCRs;
a switch circuit that selects one of the output signals of the signal extraction pulse generation circuit; a vertical synchronization confirmation circuit that checks whether the television signal vertical synchronization signal separation circuit is operating correctly; and the switch. A ghost detection circuit comprising a switch control circuit for controlling the circuit. 2. At the start of ghost detection or when the vertical synchronization confirmation circuit determines that the vertical synchronization signal separation circuit is not operating correctly, the switch control circuit controls the output signal of the first GCR signal sampling pulse generation circuit. 2. The ghost detection circuit according to claim 1, wherein said switch circuit is controlled to select. 3. At the start of ghost detection or when the vertical synchronization confirmation circuit determines that the vertical synchronization signal separation circuit is not operating correctly, the switch control circuit detects an odd field when the output signal of the field discrimination circuit indicates an odd field. Selecting the output signal of the first GCR signal sampling pulse generation circuit,
2. The ghost detection circuit according to claim 1, further comprising controlling said switch circuit to select the output signal of said second GCR signal sampling pulse generation circuit. 4. The field discrimination circuit includes a vertical synchronizing signal shaping pulse generation circuit that makes the pulse width of the vertical synchronizing signal approximately half the horizontal synchronizing period, and a horizontal synchronizing signal shaping pulse generation circuit that makes the pulse width of the vertical synchronizing signal approximately half the horizontal synchronizing period, 2. The ghost detection circuit according to claim 1, further comprising a circuit for determining whether or not there is a synchronization signal. 5. At the start of ghost detection or when discontinuity of the vertical synchronization signal occurs, extract the GCR signal using the horizontal synchronization signal, and then extract the GCR signal using the color subcarrier to detect ghosts. A ghost detection method characterized by: 6. At the start of ghost detection or when a discontinuity of the vertical synchronization signal occurs, the horizontal synchronization signal of the odd field is used to extract the GCR signal, and after that, the GCR signal is extracted using the color subcarrier.
A ghost detection method characterized by extracting a CI signal and detecting a ghost.