JPH0373676A - Noise removing circuit for ghost removing device - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is applied to a ghost removal device that uses ghost removal standard No. 4 to remove ghost signals from video signals containing ghosts. The present invention relates to a suitable noise removal circuit.

[Prior Art] A ghost removal device that uses a ghost removal reference signal has been developed in order to remove a ghost signal from a video signal containing ghosts.

An example of a ghost removal reference signal (OCR signal) inserted into a video signal to remove ghosts is shown in FIG.

This OCR signal is a signal with an 8-field period,
As shown in the figure, it is inserted within the vertical blanking period of the video signal. In the 1st, 3rd, 6th and 8th fields, the rising edge is 5.
An OCR waveform with inX/X1 falling characteristic of 2T is inserted. O-pedestal waveforms having the same setup as the OCR waveform are inserted into the second, fourth, fifth and seventh fields.

These two waveforms (OCR waveform and O-pedestal waveform) form an 8-field sequence that is repeatedly sent out every 8 fields as shown in the figure.

FIG. 5 shows a ghost removal device that uses this OCR signal to remove ghosts.

The video signal input from the video signal input terminal 10 is sent to the delay circuit 12 and the front ghost transversal filter 1.
3 and the respective outputs are added at addition 1M14. The output of the adder 14 is added to the output signal of the post-ghost transversal filter 16, which is input to the next addition N15. The output signal of the adder 15 is input to a rear ghost transversal filter 16, a video signal output terminal 17, and an 8-field arithmetic circuit 18, respectively.

The initial coefficients of the transversal filters 13 and 16 are all O.

A gate pulse for GCR No. 8 generated by the gate pulse generation circuit 24 is sent to the 8-field arithmetic circuit 18 from the synchronization signal No. 43 inputted from the synchronization signal input terminal 23 .

The 8-field arithmetic circuit 18 takes in the GCR signal portion of the video signal and performs the following arithmetic processing.

In other words, in the 8-field sequence shown in Figure 3, G
The field of the CR waveform, thus the 1st 3.6.8 field, is added and the field of the O pedestal waveform, thus the 2.4.5° 7 field, is subtracted.

Through this arithmetic processing, signals existing before and after the inserted OCR signal (sync signal, burst signal, previous line signal, etc.) are removed, and only the OCR waveform shown in FIG. 4A is output. This OCR waveform is the noise removal circuit 2
6 to remove noise components included in the OCR waveform, and then to the differential port ii! ! Differential processing is performed at 519 (FIG. 4B). This differential signal is input to subtraction N21.

On the other hand, in the reference signal generation circuit 20, the differential signal is
1, a 5jnX/X pulse reference No. 8 as shown in FIG. 4C is generated. Then, the difference signal between the differential signal obtained in subtraction N21 and the reference signal is transmitted to the filter coefficient setting circuit 22.

The filter coefficient setting circuit 22 first calculates and sets the coefficients of the front ghost transversal filter 13 using the difference signal. Then, after the front ghost is removed, the difference signal is obtained again in the same way, and the coefficients of the rear ghost transversal filter 16 are calculated and set, and the rear ghost is removed.

Note that the ghost removal range is up to just before the 2T pulse present in the latter half of the differential signal in FIG. 4B.

FIG. 6 is a system diagram of the noise removal circuit 26, and it is assumed that the number of times of addition processing for noise removal is n times (n is an integer).

The OCR signal input from the noise removal input terminal 1 is supplied to the adder 2 and the noise removal control circuit 9.

The adder 2 adds the input signal and the output signal of the line memory 25, and the sum signal is added to the line memory 25 and 1/n.
It is led to a circuit (attenuation circuit) 4.

When the number of additions reaches n, the noise removal control circuit 9 clears the contents of the line memory 25 and at the same time causes the 1/n circuit 4 to convert the sum signal into 1/n and output it. That is, the noise removal circuit 26 averages and outputs the signals of n times, and when this is finished, it starts the noise removal process again for the next n times.

[Problems to be Solved by the Invention] The noise removal circuit 26 used in such a ghost removal device uses the output of the 8-field arithmetic circuit 18 to remove noise from the OCR signal. ,
Considering the number of noise removal processes n, the differential signal is output to the subtracter 21 only once every 8n fields in total, so the filter coefficients can be set only once every 8n fields.

Then, when the filter coefficient is set -1, the output number 8 changes accordingly, so it is necessary to wait for 8n fields again, and it takes a considerable amount of time until the ghost is removed.

Therefore, the present invention solves these problems and proposes a noise removal circuit that can shorten the time until ghosts are removed.

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention provides a noise removal circuit of a ghost removal device that uses an 8-field sequence of ghost removal reference signals to remove ghosts. an adding means for adding an input video signal and an already stored video signal; a first storage means for storing the addition output for each field of an 8-field sequence; When 1/n
a second storage means for storing the output for each field; and a switching means for switching between an output signal from the storage means and an input video signal, and a second storage means for storing the output for each field. The present invention is characterized in that the ghost removal reference signal inserted into the video signal is replaced with a ghost removal reference signal from which noise has been removed, and the signal is output in an 8-field sequence.

[Operation] In this configuration, noise removal of the OCR4M signal is performed at the input stage of the video signal. The signal with that noise removed (
The ghost contained in the video signal is removed in the processing system after the 8-field arithmetic circuit 18 using the stored signal until the noise removal by the next n times of averaging is completed. do.

In this way, after the first 8n fields,
Since the filter coefficients are set once every eight fields, the time required to remove ghosts can be shortened.

[Embodiment] Next, an example of a noise removal circuit for a ghost removal device according to the present invention will be described in detail with reference to FIG. 1 and subsequent figures.

First, FIG. 2 shows a ghost removal device to which the present invention is applied. In this figure, explanation of the same parts as in the configuration of FIG. 5 will be omitted.

Noise removal circuit 11 for OCR signals according to the present invention
is placed before the ghost removal process, and performs ghost processing using the noise removed OCR signal.

Therefore, the front ghost transpersal filter 13
This noise removal circuit 11 is inserted in the preceding stage, and is supplied with the video No. 48 from the input terminal 10, and also receives the GCR gate signal from the gate pulse generation port '1524 as a control signal.

The OCR waveform output from the 8-field arithmetic circuit 18 is directly supplied to the differentiating circuit 19.

The noise removal circuit 11 is configured as II as shown in FIG.

The video signal input from the noise removal input terminal 1 is input to the adder N2 and the switch circuit 6. In the adder 2, the input signal is stored in an 8-line memory 3 which functions as a first storage means.
The sum signal is input to an 8-line memory 3 and a 1/n circuit (arithmetic circuit) 4. n is any integer, and in this example a value of about 32 is used, but this is just an example.

The OCR waveform (signal) for 8 fields after noise removal outputted from the 1/n circuit 4 is supplied to an 8-line memory 5 which functions as a second storage means. That is,
OCR waveforms for 8 fields from 1st field to 8th field (additional average value signal for n times) are outputted to this 8-line memory 5 once every 8n fields.

The OCR gate signal input from the OCR gate input terminal 8 is input to the noise removal control vA path 9 and the switch circuit 6, and the predetermined control signal generated by the noise removal control circuit 9 is applied to the 8 line memories 3.5 and 1/ n circuit 4.

In the 8-line memory 3, the noise removal control circuit 9
An OCR signal is stored for each field in the 8-field sequence shown in FIG. 3 according to a control signal from the adder N2. That is, the OCR signals are added 0 times for each of the 1st to 8th fields, and the addition output of each field is sent to the 1/n circuit 4.

After n additions, the 8 line memory 3 is cleared and the next n
It is prepared for the addition process of times.

The 1/n circuit 4 averages the eight OCR signals added n times for each field, and stores them in the 8-line memory 5 for each field.

The averaged signal of the OCR signals stored for each field is the averaged signal of the next n times, which is 1/n.
OCR from input terminal 1 until output from circuit 4
The 8-line memory 5 outputs the averaged GCR signal of each field to the switch circuit 6 in accordance with the timing at which the signal is input.

Then, when the 0CR4ε number obtained by adding and averaging the next n times is sent, it is stored again and the same operation is repeated.

The switch circuit 6 selects the output signal of the 8-line memory 5 during the OCR signal insertion period, and outputs the video signal from the input terminal 1 as it is to the output terminal 7 during other periods.

Through the above-described operation, the noise removal circuit 11 outputs the OCR from which noise has been removed from the first 8n fields onward.
A signal is output every field in an 8 field sequence. Therefore, in the 8-field calculation circuit 18, the filter coefficient setting process is performed once every 8 fields by calculating the input OCR signal in units of 8 fields after noise removal.

That is, even if the content of the GCR signal output from the 8-line memory 5 is the same for the period of 8n fields, the OCR signal input to the 8-field arithmetic circuit 18 is the signal that has passed through the transversal filter 13.16. , and the filter coefficients of the transpersal filter 13.16 are:
Since the settings are reset every 8 fields based on the output of the 8-field arithmetic circuit 18, the ghost removal process is executed every 8 fields.

[Effects of the Invention] As explained above, according to the configuration of the present invention, after the first 8n fields, the filter coefficients are set once every 8 fields. It has the characteristic that the time taken is significantly shorter than that of the conventional method.

Figure 5 is a configuration diagram of a ghost removal device according to the prior art;
The figure is a system diagram of a conventional noise removal circuit.

3.5・ 4 ◆ 11・ 13, 16 ・ 18・ 19・ 20・ 22・ ・First and second storage means ・1/n circuit for calculation ・Noise removal circuit ・Transpersal filter ・8 field calculation circuit ・Differential circuit ・Reference I S generation circuit ・Filter coefficient setting circuit

[Brief explanation of drawings]

Claims (1)

[Claims] (1) In a noise removal circuit for a ghost removal device that uses an 8-field sequence ghost removal reference signal to remove ghosts, an addition means for adding an input video signal and an already stored video signal; , a first storage means for storing the addition output for each field of the 8-field sequence, an arithmetic means for dividing the output by 1/n when the output has been n times (n is an integer), and outputting the resultant output for each field. It has a second storage means for storing each field, and a switching means for switching between the output signal from the storage means and the input video signal, and the switching means replaces the ghost removal reference signal inserted into the input video signal. 1. A noise removal circuit for a ghost removal device, characterized in that the signal is replaced with a ghost removal reference signal from which noise has been removed, and is output in an 8-field sequence.