JPH0488755A - Ghost elimination device - Google Patents

Abstract

PURPOSE:To eliminate ghost by frequency-dividing a signal having a frequency being four times the frequency of a burst to recover a horizontal synchronizing signal and a vertical synchronizing signal, fetching a video signal into a memory and discriminating whether or not the signal is a GCR signal and revising a fetch position when the discrimination is not available. CONSTITUTION:When the processing of a channel is finished, a CPU 5 closes a switch 10 to apply a synchronizing signal from a synchronizing separator circuit 6 to a synchronizing signal recovery circuit 8. Moreover, the CPU 5 transfers an initial value to a register of a GCR gate circuit 9. Thus, signals seemingly to be 18H, 281H are fetched at first to waveform memories 4A, 4B. The CPU 5 discriminates whether or not eight sets of fetched signals are GCR signals. When discriminated to be the GCR signal, the CPU 5 opens the switch 10. When not discriminated, since it is discriminated that the vertical synchronizing signal from the circuit 6 is deviated due to ghost, the CPU 5 increments a content of a register of the gate circuit 9. Whether or not the signals are the GCR signals is discriminated further similarly, and the processing routine is repeated and when the signal is discriminated to be the GCR signal, the switch 10 is opened.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a ghost removal device that performs ghost removal using a ghost removal reference signal (GCR signal).

2. Prior Art The first generation of HDTV broadcasting, which aims to improve image quality while maintaining compatibility with current television systems, is about to begin, and ghost removal is attracting a lot of attention. Among the requirements for ghost removal performance are image quality evaluation after improvement and removal time. In other words, this means how quickly ghosts can be removed and the amount of ghosts remaining after removal can be reduced. As an example of a conventional ghost removal device, “Television Industry Society Technical Report RE80-6p
There is a ghost canceller reported in "P., 9-14, February 1980". This detects ghosts by using the differential signal of the leading edge of the vertical synchronization signal unique to television signals as a reference waveform, and performs correlation calculations on the time axis using the detected ghost signals to perform transformer detection. Ghosts are removed by sequentially correcting the tap coefficients of the versal filter.

In addition, as a ghost removal device using GCR signals,
Television Training Society Technical Report ROF Ta2-6゜pp,
There is a ghost canceller reported in "31-36". This is because the ghost removal section uses a transversal filter like the ghost canceller, but
The input and output of the transversal filter are transferred to the CPU through memory, and all ghost removal calculations including synchronous energization and processing between fields according to the transmission sequence are performed.

An example of a conventional ghost removal device will be described below with reference to the drawings. FIG. 3 is a schematic block diagram showing the configuration of a conventional ghost removal device.

In Fig. 3, 5 is a CPU, 2 is a transversal filter, 1 is an A/D converter, 3 is a D/A converter, 4 (4
A, 4B) are waveform memories, 6 is a synchronization separation circuit, and 7 is an oscillation circuit for a clock locked to the burst signal and having a frequency four times that of the burst signal.

The operation of the ghost removal device configured as above will be explained. The input video signal is sent to A/D converter 1
The signals are A/D converted and input to the transversal filter 2 and the waveform memory 4A, respectively. The input and output of transversal filter 2 are waveform memories 4A and 4B.
is input to the CPU 5 via the . The synchronization separation circuit 6 separates a horizontal synchronization signal and a vertical synchronization signal from the input video signal. The GCR gate circuit 11 generates signals indicating 18H and 281H from the synchronously separated horizontal and vertical synchronizing signals, and during that period, the signals are taken into the waveform memories 4A and 4B by DMA. In the first generation HDTV broadcast, the WRB signal and O pedestal signal shown in Fig. 4 (aJ, (b)) are as follows: WRB signal → O pedestal signal → WRB
Signal = 00 pedestal signal → 0 pedestal signal - +WR
The signal is transmitted in the same horizontal period in a sequence of 8 fields: B signal → 0 pedestal signal → WRB signal. The signal shown in FIG. 4(C) can be obtained by performing the calculation shown in equation 1 below on the signals of these 8 fields. However, Fn (n=1 to B) represents the signal of the nth field.Hereinafter, the processing between fields according to the transmission sequence as shown in the first equation will be referred to as field sequence processing.

F-1/4 ((Fl-F5) 10F6-F2)+(F
3-F7) 10 (FB-F4)l... (1) Actually, the signal shown in Figure 4 (d), which is obtained by differentiating the signal in Figure 4 (C), is used as the reference signal for ghost detection, and the following is done. Perform ghost removal calculation.

Generally speaking, M S E (Mean 5 square E
rror) method or Z F (Zero Forcin
g) method, etc., which sequentially correct on the time axis according to a certain algorithm to finally find the optimal tap coefficient. If the output signal of the transversal filter is 1Yk), the reference signal is (Rkl), the difference signal between the output signal of the transversal filter and the reference signal is (Ek), and the total number of taps is M+N+1, then the nth tap of the transversal filter is The coefficient C(1)1-1 is corrected based on the second equation below in the MSE method and the third equation in the ZF method.

However, α and β are coefficients for determining the amount of correction.

(Ci l axis "Ilx (Ci) i'1) - α・Σ
Yk-i・Ek...(2)--N (Ci) 'Angle el+ = ((i) (11
) −β・Ek(3) CPU 5 is
After performing the synchronous energization and feed sequence processing shown in the first equation, the calculation of the second or third equation is performed to repeatedly correct the tap coefficient. This series of processing is performed by software, and the remaining The process is repeated until the amount of ghost becomes sufficiently small.

In the conventional configuration, data is loaded into the waveform memory using G
The problem to be solved by the invention is to generate a GCR gate signal indicating each horizontal synchronization period of 18H281H in which a CR signal is inserted from a vertical synchronization signal and a horizontal synchronization signal obtained by synchronously separating an input video signal, and to perform the period using DMA. However, with the above configuration, if vertical synchronization separation is not performed properly due to strong ghosting, etc., and the vertical synchronization shifts or becomes unstable, the extraction of the GCR signal will also become unstable, making it impossible to capture the regular GCR signal. The problem was that it malfunctioned.

In view of the above problems, the present invention provides a ghost removal device that discriminates a GCR signal even if the synchronization separation operation is unstable and performs a ghost removal operation using the GCR signal.

Means for Solving the Problems In order to solve the above problems, the ghost removal device of the present invention has four bursts locked to a burst of video signals as an input.
A means for reproducing horizontal and vertical synchronizing signals by dividing a signal with twice the frequency, a means for capturing a video signal of an arbitrary horizontal period into a memory based on the reproduced synchronizing signal, and a means for capturing a video signal of an arbitrary horizontal period into a memory, and the captured signal is a GCR signal. GC.
It is equipped with a means for changing the capture position when it cannot be determined that it is an R signal.

Effect The present invention has the above-described configuration, so that the G
When data for one horizontal period other than the CR signal is captured, the captured signal is not used for ghost removal, and by searching for a new GCR signal sampling position, the GCR signal is captured correctly and ghost removal is performed. can be done.

Embodiment Hereinafter, a ghost removal device according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram of a circuit configuration of a ghost removal device in an embodiment of the present invention. In FIG. 1, 1 is an A/D converter, 2 is a transversal filter, 3 is a D/A converter, 4 is a waveform memory,
5 is a CPU, 6 is a synchronization separation circuit, 7 is an oscillation circuit that generates a clock signal locked to the burst of the input video signal, and 8 is a horizontal and vertical synchronization signal, and a synchronizer that reproduces horizontal and vertical synchronization signals based on the clock signal. 9 is a GCR gate circuit; 10 is a switch for connecting/disconnecting the vertical synchronization signal from the synchronization separation circuit 6;

The operation of the ghost removal device configured as described above will be described below. The input video signal is A/
The output of the transversal filter 2 is A/D converted and input to the transversal filter 2 and the waveform memory 4A, respectively.The output of the transversal filter 2 is input to the CPU 5 via the waveform memory 4B. The CPU 5 uses the waveform memory 4 to determine whether the input data is a GCR signal or not.
It is determined by software whether the eight sets of signal waveforms taken into A and 4B match the GCR signal transmission sequence.

- The two-way separation circuit 6 separates the horizontal and vertical synchronizing signals from the input video signal. *4 fsc oscillation circuit 7 generates a clock having a frequency four times that of the burst, which is locked to the burst of the input video signal.

The synchronization signal reproducing circuit 8 resets the signal obtained by frequency-dividing the clock from the 4fsc oscillation circuit 7 with the horizontal and vertical synchronization signals of the synchronization division M circuit ε, and reproduces each synchronization signal. - Once the input synchronization signal is regenerated, it resets with its own synchronization signal and continues reproducing the synchronization signal.The GCR gate circuit 9 uses the regenerated horizontal and vertical synchronization signals and the register set by the CPU A signal indicating l horizontal period is generated based on the value of .The initial values are 18H and 281H.Therefore,
Initially, signals believed to be 18H and 281H are taken into the waveform memories 4A and 4B. Thereafter, the CPU 5 performs field sequence processing in accordance with the first equation to capture a signal containing a ghost, and performs a difference with a reference signal stored internally in advance to obtain a ghost detection component. Thereafter, the transversal filter 2 is controlled by performing calculations shown in the second and third equations.

The operation will be explained below using FIG. 2.

When the channel changes, the CPU 5 turns on the switch IO to supply the synchronization signal from the synchronization separation circuit 6 to the synchronization signal reproducing circuit 8. Then, the initial value is transferred to the register of the GCR gate circuit 9. Therefore, initially the waveform memory 4
Signals thought to be 18H and 281H are taken into A and 4B. The CPU 5 determines whether the eight sets of signals taken in are GCR signals or not. Here, the determination is made based on the shape of the WRB and whether or not they are an 8-field sequence. CP if it is determined to be a GCR signal
U5 turns off switch lO. If it is not determined to be a GCR signal, it is considered that the vertical synchronization signal in the synchronization separation circuit 6 is shifted due to a ghost, so the CPU 5
The value of the register of the CR gate circuit 9 is incremented. After that, it is similarly determined whether or not it is a GCR signal,
This routine is repeated, and when it is determined that the signal is a GCR signal, the switch 10 is turned off. After this, a conventional ghost removal operation is performed.

Effects of the Invention As described above, according to the present invention, a synchronization signal is reproduced based on a signal locked to a burst, and a video signal of one arbitrary horizontal period is captured into a memory based on the reproduced synchronization signal.
By providing a means to determine whether the captured signal is a GCR signal, it is possible to prevent synchronization during strong ghosting, etc.
Even when the signal is unstable, it is possible to stably capture the GCR signal without capturing irregular data. Furthermore, since the synchronization signal from the synchronization separation circuit is disconnected/connected, even if the synchronization separation becomes unstable due to fluctuations in APL, the GCR signal can be extracted stably, and a stable ghost removal operation can be performed.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a ghost removal device according to an embodiment of the present invention, FIG. 2 is a flowchart of the processing flow of the ghost removal device of the present invention, and FIG. 3 is a block diagram of a conventional ghost removal device. Figure 4 is a waveform diagram for explaining the ghost removal operation (the waveform is the WRB signal waveform, (b) is the O pedestal waveform, (C) is the signal subjected to 8-field sequence processing, and (d) is the waveform of the ghost detection signal. It is a diagram. 2...Transversal filter, 4A, 4B
... Waveform memory, 5 ... CPU, 6.
... Synchronization separation circuit, 7 ... 4fsc oscillation circuit, 8 ... Synchronization signal regeneration circuit, 9 ...
・GCR gate circuit, 10... switch. 1! ! 1 Figure 2 Figure Figure (α) wRB layer! (b) 0be handstal number (C) 8 field sequence) 1st number in 1 (d) IriQtsufu! ! %kushidan number

Claims (2)

[Claims] (1) A device that performs ghost removal using a ghost removal reference signal includes an oscillation circuit that oscillates at four times the frequency of the burst, which is locked to the burst of the received video signal, and a clock of the oscillation circuit that is divided. a circuit that reproduces horizontal and vertical synchronization signals, a GCR gate circuit that specifies one specific horizontal period from the reproduced horizontal synchronization signal and vertical synchronization, and a circuit that captures the video signal of one specific horizontal period into a memory; A ghost removal device characterized by comprising means for determining whether a captured signal is a ghost removal reference signal. (2) A means for determining whether the signal is a Goroto removal reference signal,
2. The ghost removal apparatus according to claim 1, wherein the signal taken into the memory is processed by software, and a determination process is performed based on whether the signal matches a transmission sequence of a ghost removal reference signal.