JPH04177979A - Ghost elimination device - Google Patents

Abstract

PURPOSE:To eliminate effectively only noise without distorting a tap coefficient group by providing a coring section and a noise detection section which detects an integration value of an absolute value of the tap coefficient group generated from a waveform just before a reference waveform as a noise level and increases a threshold level of the coring section as the detected value increases to the elimination device. CONSTITUTION:A noise detection section 26 calculates an integration value of an absolute value of a part generated from a waveform just before a reference waveform in a tap coefficient group outputted from an inverse Fourier transformation section 24 and detects the calculated value as a noise level and sets a threshold level increasing together with the increase in the detected noise level to the coring section 25. A ghost elimination filter 30 uses a transversal filter to generate a pseudo ghost and eliminates ghost by subtracting the pseudo ghost from an original reception television signal and outputs the result to an output terminal OUT. Thus, the tap coefficient group at a high level required for eliminating the ghost is not distorted but only the noise is effectively eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a ghost removal device installed in a television receiver.

(Prior Art) A ghost division device installed in a television receiver includes a transversal filter for generating pseudo-ghosts, and detects a ghost from the waveform of a received television signal and sets it in the transversal filter. and a ghost detection section that generates a group of tap coefficients. The ghost detection section is usually configured to detect a ghost based on a reference waveform extracted from a predetermined portion of a received television signal and waveforms before and after the reference waveform.

This ghost removal device takes various measures to reduce the influence of noise contained in the received television signal.

Patent application No. 1-8 filed earlier by the applicant and already published
According to No. 7224 (Japanese Unexamined Patent Publication No. 2001-1999), a low-pass filter unit removes the high-frequency components of the generated tap coefficient group by considering them to be due to the influence of noise; A ghost removal device is disclosed that reduces the influence of noise by comprising a noise detection section that detects a noise level from a region immediately before a reference waveform and, as the noise level increases, lowers a high-side cutoff frequency of the low-pass filter section. ing.

(Problems to be Solved by the Invention) The ghost removal device of the prior application has a configuration in which the high-frequency components of the tap coefficients are regarded as noise and are removed by the low-pass filter section. Therefore, there is a problem that distortion due to the influence of filtering also exists in the tap coefficient group on the low frequency side, and the ghost removal performance deteriorates.

Further, the ghost removal device of the prior application is configured to control the cutoff frequency of the low-pass filter section based on the noise component contained in the received television signal. Therefore, the noise in the tap coefficient group is detected indirectly, which poses a problem in terms of noise detection accuracy.

(Means for Solving the Problem) According to an uninvented ghost removal device, a coring section that performs coring on a group of tap coefficients generated from a reference waveform and a waveform immediately after it, and a waveform immediately before the reference waveform and a noise detection unit that detects the integrated value of the absolute values of the evening knob coefficient group generated from the noise level, and increases the darkness value of the coring unit as the detected value increases. , is configured to directly detect the noise included in the tap coefficient group and to effectively remove only the noise without distorting the high-level tap coefficient group necessary for ghost removal.

Hereinafter, the functions of the uninvented invention will be explained in detail together with examples.

(Embodiment) FIG. 1 is a block diagram showing the configuration of a ghost removal device according to an embodiment of the invention, in which IN is an input terminal for a received television signal to be ghost removed, 10 is a reference waveform extraction unit, and 20 30 is a ghost detection section, 30 is a ghost removal filter section, and OUT is an output terminal for the received television signal from which ghosts have been removed.

The reference waveform extraction section 10 in the previous stage includes a timing generation section 11,
A/D conversion section 12, addition section 13, and extracted waveform holding section 14
It consists of The ghost detection section 20 in the latter stage includes an extracted waveform Fourier transform section 21, a reference waveform Fourier coefficient holding section 22, a division section 23, an inverse Fourier transform section 24, a coring section 25 with a variable darkness value, a noise detection section 26, and a tap coefficient group. It consists of a holding register 27.

The analog received television signal supplied to the input terminal IN is supplied to the ghost removal filter section 3o, and is also sent to the timing generation section 11 of the reference waveform extraction section 1o and the A/
The signal is supplied to the D converter 12. The timing generation unit 11 detects various synchronization signals included in the received television signal, and based on these, instructs the extraction timing of the reference waveform inserted at a predetermined location of the received television signal and the waveforms before and after the reference waveform. The adder 1 generates a signal that
3 and is supplied to the extracted waveform holding unit 14.

A, /r) The received television signal converted into a digital signal in the converting section 12 is subjected to time averaging processing by addition with the old held data held in the extracted waveform holding section 14 in the adding section 13, and the extracted waveform is It is held by the holding part 14. This time averaging process by repeating the addition with the old held data is performed over a shorter period of time, for example, number+fields, than in the conventional apparatus. The reference waveform whose noise components have been reduced by this time averaging process is
The signal is supplied to the ghost detection section 20.

The extracted waveform Fourier transform unit 21 of the ghost detection unit 20 is
By performing Fourier transform on the reference waveform extracted in the previous stage and the waveforms before and after it, Fourier transform coefficients of the extracted waveform distorted by ghosts are generated. On the other hand, the reference waveform Fourier coefficient holding unit 22 contains in advance Fourier coefficients generated by Fourier transforming the reference waveform to be inserted into a predetermined position of the transmitted television signal and the undistorted waveforms before and after the reference waveform. Retained.

The dividing unit 23 divides the output of the extracted waveform Fourier transform unit 21 by the output of the reference waveform Fourier coefficient holding unit 23 to generate Fourier coefficients of the ghost that is occurring, and outputs it to the inverse Fourier transform unit 24 at the next stage. do. The inverse Fourier transform unit 24 generates a group of tap coefficients necessary for generating a pseudo ghost based on the Fourier coefficients of the ghost received from the previous stage,
It is output to the coring section 25 at the next stage.

The coring unit 25 selects and outputs only those tap coefficients whose absolute values exceed a predetermined darkness value from among the tap coefficients received from the previous stage. The noise detection unit 26 calculates the integrated value of the absolute value of the portion generated from the waveform immediately before the reference waveform among the tap coefficient group output from the inverse Fourier transform unit 24, and regards this calculated value as the noise level. to detect. Noise detection section 26
sets a darkness value in the coring unit 25 that increases with the increase in the detected noise level. The tap coefficient group cored by the coring unit 25 is held in the tap coefficient group holding register 27.

The ghost removal filter 30 converts the received television signal supplied from the input terminal IN into a digital signal,
This digital television signal and ghost detection section 20
A pseudo-ghost is generated by a transversal filter according to a group of tap coefficients supplied from the transversal filter, and ghost removal is performed by subtracting the pseudo-ghost from the original received television signal, and the result is output to the output terminal OUT.

The noise detection unit 26 in FIG. 1 is composed of an absolute value generation unit 26a and an integration unit 26b, as illustrated in block M in FIG. It is configured to integrate and output this to an output terminal O as a noise level.

An example of a reference waveform inserted into the outgoing television signal is
As illustrated in FIG. 3(A), it is a step-like waveform superimposed on the latter half of the pedestal of a predetermined line within the vertical blanking period. As shown in FIG. 3(B), the extracted waveform received by the receiver, extracted while undergoing time averaging processing, and output from the reference waveform section 10 is distorted due to the influence of ghosts and has a relatively high frequency. It contains low-level noise components. In this case, ghost detection starts from the point immediately before the step waveform, and noise detection is performed from the start point of ghost detection to the point immediately before the step waveform rises and falls. .

(Effects of the Invention) As described above in detail, the ghost removal device of the present invention includes a coring section that performs coring on a group of tap coefficients, and a coring section that performs coring on a group of tap coefficients. Since the structure is equipped with a noise detection section that increases the darkness value of the tap coefficient group, it is possible to directly detect the noise in the tap coefficient group, and to make only the noise effective without distorting the high-level tap coefficient group necessary for ghost removal. This has the effect of being able to be removed.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the configuration of a ghost removal device according to an embodiment of the present invention, FIG. 2 is a block diagram showing an example of the configuration of the noise detection section 26 in FIG. 1, and FIG. FIG. 2 is a conceptual diagram illustrating a reference waveform to be inserted at a predetermined location of the reference waveform and a waveform of a received television signal including the reference waveform. DESCRIPTION OF SYMBOLS 10... Reference waveform extraction part, 20... Ghost detection part, 21... Extracted waveform Fourier transform part, 22... Reference waveform Fourier coefficient holding part, 23... Division part, 24...
- Inverse Fourier transform section, 25...coring section, 26.
. . . Noise detection section, 30 . . . Ghost removal filter section. Patent applicant: NEC Home Electronics Co., Ltd.

Claims (1)

[Claims] A transversal filter for generating a pseudo-ghost;
A ghost removal device comprising: a ghost detection unit that detects a ghost based on a reference waveform extracted from a predetermined part of a received television signal and waveforms before and after the reference waveform and generates a group of tap coefficients to be set in the transversal filter; The ghost detection unit includes a coring unit that performs coring on a group of tap coefficients generated from the reference waveform and the waveform immediately after the reference waveform, and a coring unit that performs coring on a group of tap coefficients generated from the waveform immediately before the reference waveform; A ghost removal device comprising: a noise detection unit that detects an integrated value as a noise level, and increases a threshold value of the coring unit as the detected value increases.