JPH03183269A - Ghost eliminating device - Google Patents

Abstract

PURPOSE:To considerably shorten the processing time and to eliminate an influence of the variance due to disturbance of an input signal by synchronously adding a GCR signal or a vertical synchronizing signal by a CPU and transferring this signal to a RAM after field sequence processing and switching the read timing to each horizontal period or vertical period to repeatedly read out the signal. CONSTITUTION:An input video signal is inputted to a ghost eliminating circuit 3. A CPU 5 repeatedly takes in the input video signal and sufficiently performs synchronous addition to improve S/N. Thereafter, the field sequence processing is performed, and the signal is transferred to a RAM 1 and is written. Hereafter, a switching circuit 2 selects the (b) side to repeatedly read out the RAM 1. The signal in the RAM 1 is read out while switching the read timing to each horizontal period or vertical period by a read timing control circuit 6 and is taken into a CPU 5 in the same manner as first taking-in of the input video signal.

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 GCR signal or a vertical synchronization signal.

Conventional Technology The first generation of EDTV broadcasting, which aims to improve picture quality while maintaining compatibility with current television systems, is about to begin, and ghost removal is attracting a lot of attention. Image quality evaluation value after improvement to ghost removal performance required in this,
There is an item for removal time. In other words, it is possible to remove ghosts in a short time and with a small amount of ghosts remaining after removal. As an example of a conventional ghost removal device, the Televisine Society Technical Report RE80-6, pp.
There is a ghost canceller reported on 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 a GCR signal, the Technical Report of the Television Society of Japan ROFT81-6, pp. 31
There is a ghost canceller reported in -36. This uses a transversal filter in the ghost canceller like the ghost canceller described above, but the input and output of the transversal filter are taken into the CPU via memory, and synchronous addition is performed between fields according to the transmission sequence. Performs all ghost removal calculations including the processing of . 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, 12 is a transversal filter,
20 is an A/D converter, 21 is a D/A converter, and 22 is a waveform memory. The operation of the ghost removal device configured as above will be explained. The input video signal is
The signals are A/D converted by an A/D converter 20 and input to a transversal filter 12 and a waveform memory 22, respectively. The input and output of the transversal filter 12 are input to the CPU 5 via the waveform memory 22. In the first generation EDTV broadcast, the W shown in Figures 4(a) and (b)
The RB signal and the ○ pedestal signal are transmitted in the same horizontal period in a sequence that goes around in 8 fields: WRB signal - +O pedestal signal -> WRB signal - ○ pedestal signal -> O pedestal signal -> WRB 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 8> is the nth
Represents field signals. 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)+ (F6-F2)+
(F3-F7)+ (FB-F4)) ・・・・・・
・(1) Actually, the signal shown in FIG. 4(d), which is obtained by differentiating the signal in FIG. 4(C), is used as the reference signal for ghost detection, and the following ghost removal calculation is performed. Generally, the tap of a transversal filter is used. MSE (M
ean 5quare Error) method or ZF
(Zero Forcing) method, etc., and these methods sequentially correct on the time axis according to a certain algorithm to finally find the optimal tap coefficient. The output signal of the transversal filter is (Yk), and the reference signal is (Yk).
Rkl, l - The difference signal between the output signal of the Lanceversal filter and the reference signal (Ekl, the total number of taps is M+N+l
Then, the n-th tap coefficient Co11 [' of the transversal fill is corrected based on the following equation 2 in the MSE method, and based on the equation 3 in the ZF method. However, α and β are coefficients for determining the amount of correction.

fc i l ""' = (Ci) "'α・Σ
Yk-i-Ek ......(2)=-M (Cil le+-11, 1Ci) (++1-β・
Ei (3) After performing the synchronous addition and field sequence processing shown in the first equation, the CPU 5 repeatedly corrects the tap coefficients by calculating the second or third equation.

A series of these processes is performed by software, and a flow chart thereof is shown in FIG. In this process, the process is repeated until the amount of residual ghost in ghost detection becomes sufficiently small.

In the conventional configuration, when the S/N of the input video signal is low, synchronous addition of the 8 fields shown in equation 1 alone will no longer separate the ghost and noise when the residual ghost f reaches a level almost equal to the noise signal level. It becomes impossible to distinguish, and this level becomes the performance limit for ghost removal. Therefore, in order to reduce the amount of residual ghosts and improve ghost removal performance, it is necessary to sufficiently perform synchronous addition to improve the S/N ratio for the above reasons.

However, the processing time increases in proportion to the number of synchronous additions, resulting in a longer ghost removal time. Furthermore, each time the correction is made, the input signal is
This means that there is instability in the operation, such as divergence, due to re-importing the data into the PU. That is, when corrections are made sequentially on the time axis, the optimal solution for the tap coefficient is determined according to a fixed procedure while oscillating, so it is easily affected by noise and other disturbances. If the tap coefficients are affected and the combination of tap coefficients becomes a tap coefficient sequence that causes divergence, the output of the transversal filter 12 will diverge.

Problems to be Solved by the Invention In the configuration of a conventional ghost removal device, in order to reduce the amount of residual ghosts as much as possible and improve ghost removal performance, it is necessary to perform sufficient synchronous addition to improve the S/N ratio. On the other hand, increasing the number of synchronous additions results in a longer ghost removal time. Furthermore, since corrections are made sequentially on the time axis, not only does the ghost removal time increase, but also the influence of external disturbances becomes more likely, increasing the possibility of divergence. In view of the above-mentioned problems, the present invention reduces the amount of ghosts remaining after ghost removal as much as possible, and also significantly shortens the removal time compared to the conventional method in which a signal is captured every time the tap coefficient is successively corrected. An object of the present invention is to provide a ghost removal device that can improve stability.

Means for Solving the Problem In order to achieve this goal, the CPU performs synchronous addition and field sequence processing on the GCR signal or vertical synchronization signal, transfers it to RAM, and reads out the RAM during the horizontal period. The signal read out repeatedly and the input signal of the ghost removal device are switched between every vertical period and the input signal of the ghost removal device, and the signals are input to the ghost removal means.

In the present invention, once synchronous addition and field sequence processing are performed using the above-described configuration, this signal is repeatedly read out in the RAM to perform ghost removal calculations. This greatly reduces processing time without having to import signals each time the tap coefficients are successively corrected, and by providing a sufficient number of synchronous additions, the S/N ratio is sufficiently improved, and fluctuations due to disturbances in the input signal are avoided. Avoid being influenced.

EXAMPLE Hereinafter, a ghost removal device according to an example of the present invention will be described with reference to the drawings. FIG. 1 is a schematic block diagram of the circuit configuration of a ghost removal device in a first embodiment of the present invention. In Fig. 1, 1 is a RAM, 2 is a switching circuit,
3 is a ghost removal circuit, 4 is a memory, 5 is a CPU, and 6 is a read timing control circuit. The operation of the ghost removal device configured as described above will be described below.

Initially, the switching circuit 2 selects the a side, and the ghost removal circuit 3 receives an input video signal.

The input and output of the ghost removal circuit are taken into the CPU 5 via the memory 4. The CPU 5 repeatedly takes in input video signals and performs sufficient synchronous addition to improve the S/N ratio. Thereafter, the field sequence processing shown in equation 1 is performed to calculate the signal shown in FIG. 4(d). This signal is transferred from the CPU 5 to the RAMI and written. After this, the switching circuit 2 selects the b side and repeatedly reads out the RAMI. The readout timing control circuit 6 determines whether the signal from the RAMI is read every horizontal period or every vertical period. The signal is switched, read out, and captured into the CPU 5 in the same way as when the input video signal was first captured.

The CPtJ5 performs a difference with a reference signal previously held internally, performs calculations shown in the second equation and the third equation, and controls the ghost removal circuit 3. A flowchart of the processing at this time is shown in FIG.

Here, assuming that N fields are required for synchronous addition, M times for correction, and L fields are required for ghost detection + calculation + tap coefficient correction, when comparing the conventional method and the configuration of the present invention when all processing is performed. , the processing time ratio α is as shown in the fourth equation below.

α=N+M*L/ (N+1.)*M...
...(4) Here, the synchronous addition is 128 as the value for - boat fishing.
Field, number of corrections 20 times, ghost detection + calculation +
If we consider the case where the tap coefficient is corrected by one field, α becomes 1/17, which is a significant reduction.

Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. FIG. 2 is a block diagram showing a specific embodiment of the present invention. In FIG. 2, lO is a GCR signal sampling circuit, and 11 is a FIFO.

12 is a transversal filter, 13 is a selector, 1
4 is a counter, 15 is the number of times of synchronous separation, and 16 is a reset circuit. The GCR signal extraction circuit IO generates a gate pulse signal during the period when the GCR signal is superimposed. Further, the reset circuit 16 generates a reset pulse for resetting the FIFO II from the horizontal synchronization signal 2 and the vertical synchronization signal from the synchronization separation circuit 15. The input video signal is input to the transversal filter 12 with the switch 2 selecting the C side. Transversal filter 12
The input and output of gate pulse signal period selector 1
3 supplies the counter output to the memory address,
It is written to memory 4 by DMA processing. After this memory 4
An address is supplied from the CPU and read into the CPU 5, where it performs synchronous addition and field sequence processing shown by the first equation, all of which are processed by software within the CPU. After performing this series of processing a necessary number of times, select b with switch 1 and transfer it to PIFO II. After the transfer is completed, switch 1 is switched to the d side and the FIFO
II repeatedly outputs the signal read out and written by the CPU. FIFO II controlled by reset circuit
Switch whether to read for each horizontal sync signal or for each vertical sync signal.

On the other hand, the switch 2 is also switched to the d side at the same time, and the output of the FIFO II is input to the transversal filter 12. After transferring to FIFO II in this way, the FIFO
By using the I signal, it is possible to process signals that have already been subjected to synchronous addition and field sequence processing each time, thereby shortening the processing time and making it possible to operate stably as if using a fixed signal source.

Effects of the Invention As described above, according to the present invention, after performing -degree synchronous addition and field sequence processing, this signal is switched with the input video signal for use, thereby significantly shortening the processing time and improving stability. It becomes possible to remove ghosts by raising the level.

[Brief explanation of drawings]

FIG. 1 is a schematic block diagram of a ghost removal device according to an embodiment of the present invention, FIG. 2 is a block diagram of a specific embodiment of the ghost removal device of the present invention, and FIG. 3 is a block diagram of a conventional ghost removal device. Block diagram, Figure 4(a) is a signal waveform diagram of the WRB signal, Figure 4(b) is a signal waveform diagram of the O pedestal signal, Figure 4(C) is a signal waveform diagram after field sequence processing, FIG. 4(d) is a signal waveform diagram obtained by differentiating FIG. 4(C), FIG. 5 is a flowchart of conventional ghost removal processing, and FIG. 6 is a flowchart of ghost removal processing of the present invention. l...RAM, 2...switching circuit, 3.
...Ghost removal circuit, 4...Memory,
5...CPU, 6...Read timing control circuit, 10...GCR signal extraction circuit,
11... FIFo, 12... Transversal filter, 13... Selector, 14...
... Counter, 15 ... Synchronization separation circuit,
16...J set circuit.

Claims (1)

[Claims] A ghost removal device that performs ghost removal using a GCR signal or a vertical synchronization signal, comprising means for performing ghost removal, and means for switching the input of the ghost removal device between an input video signal of the ghost removal device and an output signal of a RAM; A memory that captures the input signal and output signal of the ghost removal means, and a memory that captures the signal of the memory and performs processing between fields according to a synchronous addition and transmission sequence and a ghost removal operation so as to enable a ghost removal operation. and a readout timing control circuit that controls readout timing from the RAM and switches whether to read out every horizontal period or every vertical period. 2. A ghost removal device, characterized in that, after the signal processed between the two is transferred, the switching means inputs this signal to the ghost removal means at the read timing.