JPH0757012B2 - Ghost removal device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ghost eliminating device, and more particularly, to various ghost and waveform distortions contained in an input video signal in various video devices handling a TV (television) video signal. Regarding the ghost canceller to remove.

[Conventional technology]

A conventional ghost removing apparatus will be described with reference to FIG. FIG. 2 shows a conventional typical ghost removing device 10
Is a block system diagram of 11 is a transversal filter (synthesis filter composed of FIR filter, IIR filter, etc.), 12 is a waveform extraction circuit, 13 is a differential filter, 14 is a subtractor, 16 is a magnification setting circuit, and 17 is weighting. The setting circuit 18 is a reference waveform generating circuit.

The input video signal supplied from the input line l ₁ is extracted as an output video signal from the line l ₂ via the transversal filter 11, and is supplied to the waveform extraction circuit 12,
Here, a predetermined period including the reference signal and a certain period (for example, one horizontal scanning line segment) are extracted. When the reference signal is a step-shaped signal, the differentiation filter 13 performs differentiation in order to suppress the influence of DC fluctuation. The output of the differential filter 13 is output to the subtractor 14, where it is compared (subtracted in this embodiment) with the original reference signal waveform (internal reference waveform) calculated in advance by the reference waveform generation circuit 18. Based on the result of this comparison (error signal sequence), the magnification setting circuit 16 sets a predetermined magnification. This magnification is calculated from the result of calculating an evaluation function or the like from the error signal sequence.

In the weight setting circuit 17, the tap gain of each filter forming the transversal filter 11 is determined from the error signal sequence and the magnification. As a result, the transversal filter 11 outputs a video signal from which ghost has been removed (reduced). Since the weight setting circuit 17 needs an arithmetic function, it is composed exclusively of a microcomputer or a microprocessor. Further, the signal delay due to the processing time generated in the signal processing circuit having the above configuration will be omitted for convenience of explanation.

Here, an example of a calculation circuit from the error signal sequence to the block gain (configuration example of the weight setting circuit 17) will be described with reference to FIG. FIG. 3 is a block diagram of a concrete configuration example of the weighting setting circuit 17 which constitutes the conventional ghost removing device, 21 is an error column memory, 22 is a column number counter, and 23.
Is a multiplier, 24 is an adder, and 25 is a block gain column memory.

The signal of the error signal sequence supplied from the subtractor 14 via the line l ₃ is temporarily stored in the error sequence memory 21. The accumulated error signal sequence is stored in the column number counter 22 based on the clock signal.
Are read out according to the column number (address) generated in. A multiplier 23 multiplies the read error signal sequence by the conversion magnification set by the magnification setting circuit 16. Further, the previous tap gain read from the tap gain column memory 25 is added in the adder 24 according to the same column number as the column number for the error rate memory 21, and the contents (numerical value) of the tap gain column memory 25 are sequentially rewritten. And its tap gain string is passed through line l ₄ to the transversal filter.
It is output to 11. By repeating the above operation and successively updating the tap gain, the ghost and the waveform distortion contained in the input video signal are removed.

[Problems to be Solved by the Invention]

In the above conventional ghost removing device, the reference waveform generating circuit 18
There is the following problem because the magnification for setting the tap gain is constant due to the error between the reference signal and the taken-in signal. That is, the influence of the tap gain rewriting near the center tap mainly composed of the FIR filter also influences the signal corresponding to the tap outside thereof. If this is applied to the case of ghost elimination operation, if the waveform equalization of tap gain rewriting due to the action near the center tap works, the waveform of the normal ghost outside that will change accordingly, and it corresponds to the normal ghost. The tap gain must be updated again at the next tap gain update, which takes a long time to remove the ghost, resulting in a problem that the work becomes slow.

[Means for Solving the Problems]

The ghost removing apparatus of the present invention is provided with a weight setting circuit, which is a main part of the ghost removing apparatus, which temporarily stores the error signal sequence supplied from the subtractor and the error sequence memory which supplies the column number to the error sequence memory. Input the column number counter that reads the error signal sequence and the conversion scale factor set by the scale factor setting circuit, identify the tap gain section according to the same column number as the column number for the error sequence memory, and convert for each section. A section identification table that further corrects the magnification, a multiplier that performs multiplication by multiplying the read error signal sequence by the corrected conversion factor, and the signal sequence from the multiplier is temporarily stored, The tap gain column memory that reads the tap gain according to the same column number as the column number for the error column memory and outputs it to the transversal filter, and the tap gain column memory that reads it. The tap gain sequence of the transversal filter is divided into a plurality of sections, and the tap gain sequence of the transversal filter is divided into a plurality of sections. By changing the conversion ratio of the tap gain sequence determination from the error sequence between the waveform and the reference waveform generated by the reference waveform generation circuit for each section, and by performing the ghost removal operation by sequentially updating the tap gain, The above problems have been resolved.

〔Example〕

An embodiment of the ghost removing device of the present invention will be described with reference to FIG. FIG. 1 is a block diagram showing a configuration example of a main part of a ghost removing device 10 of the present invention {an example of a calculation circuit from an error signal sequence to a tap gain (weighting setting circuit 17)}, and FIG. The same components as those shown in the conventional example are designated by the same reference numerals, and detailed description thereof will be omitted. As is clear from comparing the two figures, the device of the present invention 10
The weight setting circuit 17 includes a section identification table 26 in addition to the circuits in the conventional example, which is inserted and connected between the magnification setting circuit 16 and the multiplier 23 as shown in the first drawing, and further has a column number ( The column number counter 22 is also connected to input (address). The section identification table 26
It is composed of ROM, etc.

With such a configuration, the tap gain converges quickly in a section where the conversion rate is increased, and when the change in tap gain in that section affects other sections, the effect is reduced quickly, so the conversion rate is reduced. Convergence of the section that did is also faster. Specifically, the convergence near the center tap becomes faster, so the waveform equalization ends earlier, and the need to update the taps for normal ghosts due to the effects of waveform equalization is reduced, which reduces ghost elimination. It has become possible to reduce the time required.

Hereinafter, a specific operation will be described with reference to FIG. The signal of the error signal sequence supplied via the line l ₃ is temporarily stored in the error sequence memory 21 and read according to the column number (address) generated by the column number counter 22. On the other hand, the conversion magnification set by the magnification setting circuit 16 is supplied to the section identification table 26, the section of tap gain (preset) is identified according to the same column number as the column number for the error column memory 21, The conversion factor is further corrected depending on the section. Next, the corrected conversion factor is
The read error signal sequence is multiplied by the multiplier 23 to perform multiplication.

Further, the previous tap gain read from the tap gain column memory 25 is added in the adder 24 according to the same column number as the column number for the error column memory 21, and the contents (numerical value) of the tap gain column memory 25 are sequentially rewritten. At the same time, the tap gain string is output to the transversal filter 11 via the line l ₄ .

Here, a method of correcting the magnification for each section will be described with reference to the timing chart of FIG. FIG. 4 (A) shows an example of the error sequence obtained by the subtracter 14, and FIG. 4 (B) is a diagram showing the tap gain sequence obtained by the magnification setting circuit 16 in the error sequence. The length in the vertical direction in FIG. 7A is the value of the difference between the captured waveform extracted by the waveform extracting circuit 12 and the internal reference waveform from the reference waveform generating circuit 18, and the vertical length in FIG. The length in the direction is the value of the coefficient (tap gain) given to the filter 11 (all are digital data calculated by a digital circuit). Further, in FIG. 4, the section sandwiched by two broken lines is near the center tap of the filter, and the conversion magnification is assumed to be corrected to α ₁ in this section, and the conversion magnification is α _{2 in the} other sections. Shall be corrected to. alpha ₁ is somewhat {up to 3 times than the alpha ₂ in a range of convergence of the tap gain is performed stably (alpha ₁ ≒ 3
α ₂ )} Increase. The section of α ₁ has the effect of equalizing the waveform distortion due to the proximity ghost, and when the tap gain in this section is changed, the signal of the section corresponding to α ₂ of the captured signal also changes. Therefore, in the section of α ₂ , the tap gain must be updated again, but as described above, α
_{When 1} is larger than α ₂ , convergence of the section of α ₁ becomes faster, so that it becomes less necessary to re-update the tap gain of the section of α ₂ by updating the tap gain of the section of α ₁ , and as a result,
The total number of tap gain updates required until convergence can be reduced, and the time required for ghost removal can be shortened.

[Effect]

As described above, according to the ghost removing apparatus of the present invention, the convergence of the section in which the conversion magnification is small is accelerated, and the tap gain in the vicinity of the center tap is accelerated. Since the number of times is reduced, the waveform equalization ends early, the tap for normal ghost need not be updated due to the influence of the waveform equalization, and the time required for ghost removal can be shortened. Further, since it is a part of the tap gain series that the conversion magnification is increased, it has an excellent feature that the stability of the tap gain control until the ghost is removed hardly deteriorates.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration example of a main part of a ghost removing device of the present invention, FIG. 2 is a block diagram showing an overall configuration of the ghost removing device of the present invention and a conventional ghost removing device, and FIG. 3 is a conventional ghost removing device. FIG. 4 is a block diagram showing a configuration example of a main part, and FIG. 4 is a conceptual diagram of calculation of an evaluation function. 10 ... Ghost elimination device, 11 ... Transversal filter, 12 ... Waveform extraction circuit, 14 ... Subtractor, 16 ... Magnification setting circuit, 17 ... Weighting setting circuit, 18 ... Reference waveform generation circuit, 21 …… Error column memory, 22 …… Column number counter,
23 ... Multiplier, 24 ... Adder, 25 ... Tap gain sequence memory, 26 ... Section identification table.

Claims (1)

[Claims] 1. A FIR filter or IIR filter,
A transversal filter that removes a ghost component in an input video signal by setting those tap gains and a signal for a predetermined fixed period that includes a reference signal for ghost detection included in the input video signal are extracted. A waveform extraction circuit, a reference waveform generation circuit for generating a reference waveform signal synchronized with the extracted reference signal, a reference signal extracted from the input video signal, and a waveform of the reference signal obtained by the reference waveform generation circuit. A subtractor that compares the two and outputs an error signal sequence according to the comparison result, a magnification setting circuit that sets a magnification according to the error signal, and an output signal of the magnification setting circuit that is converted into weighting data. A ghost removing apparatus comprising: a weight setting circuit that supplies tap gain setting data to the transversal filter; An error sequence memory for temporarily storing the error signal sequence supplied from the subtractor, a column number counter for supplying a column number to the error sequence memory and reading out the temporarily stored error signal sequence, and the magnification setting A conversion factor set in the circuit is input, a section of tap gain is identified according to the same column number as the column number for the error sequence memory, and a section identification table for further correcting the conversion factor for each section, A multiplier for performing multiplication by multiplying the read error signal sequence by the corrected conversion factor, a signal sequence from the multiplier is temporarily stored, and is the same as the column number for the error sequence memory. The tap gain string memory that reads the tap gain according to the column number and outputs the tap gain to the transversal filter, and the tap gain that has been read one time before from the tap gain string memory are described above. The tap gain sequence of the transversal filter is divided into a plurality of sections by being configured with an adder that adds to the tap gain from the calculator, and the waveform of the reference signal extracted by the waveform extraction circuit and the reference waveform The ghost is characterized in that the conversion rate for determining the tap gain sequence from the error sequence with the reference waveform generated by the generation circuit is changed for each of the above intervals, and the ghost elimination operation is performed by sequentially updating the tap gain. Removal device.