JP2008053921A - Ghost removing apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a ghost removing apparatus capable of filter generation preventing the breakdown of videos as much as possible, which copes with all phenomena in a transmission path. <P>SOLUTION: The ghost removing apparatus includes: a waveform analysis part 1 for performing comparison analysis of the waveform of received GCR signals and the waveform of internal GCR reference signals; a GR filter coefficient generation part 2 for generating a filter coefficient using comparison analysis results by the waveform analysis part 1; a GR filter part 3 for generating a filter from the generated filter coefficient; a unit time count part 4 for counting the number of fields of the waveform of video signals and measuring elapsed time; and a GCR signal extraction part for performing computation for each unit time and taking out GCR signals from the video signals. The waveform analysis part 1 includes a means for changing frequency characteristics for computing the filter coefficient, and changes the frequency characteristics corresponding to time lapse from the start of a ghost removing operation. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a ghost removing apparatus that removes a ghost from a video signal by passing the received video signal through a filter.

  The ghost removing apparatus removes ghosts by comparing an internal GCR reference signal and a GCR signal sent from a broadcasting station.

The broadcast station superimposes and transmits the GCR signal during the vertical blanking period of the video signal.
The GCR signal causes ghost, waveform distortion, etc. depending on the transmission path, and the TV receives the GCR signal having the waveform distortion and ghost.

The TV compares the received GCR signal with the internal GCR reference signal, and creates a filter for returning to the same form as the internal GCR reference signal.
By passing the received video signal through the filter, waveform distortion and ghost in the transmission path are reduced.

Conventionally, a ghost removing apparatus for removing a ghost from a video signal has been proposed as Patent Document 1 and Patent Document 2.
JP 2000-156800 A Japanese Patent Laid-Open No. 10-42167

  In the conventional ghost removing apparatus, the acquisition of the received GCR signal is calculated by a unit time of 8 fields.

  When the unit time is short, the filter is updated faster, but the generation of the filter becomes unstable compared to when the unit time is long.

  Also, when the unit time is long, the generation of the filter is stable, but the filter update is slower than when the unit time is short.

  Furthermore, if an incorrect filter is generated when generating a filter, the video may fail.

  In order to prevent the generation of this incorrect filter, the time until the filter is reflected is shortened as much as possible while preventing the generation of the incorrect filter, such as by increasing the unit time until the filter is calculated. There is a need to reduce discomfort during the renewal.

  It is also important to prevent generation of erroneous filters due to noise, sag, frequency characteristics, and the like.

  Therefore, the present invention has been made in view of the above circumstances, and at the time of generating a filter for removing a ghost, in order to prevent generation of an erroneous filter, frequency characteristics are controlled in each block, and a transmission line It is an object of the present invention to provide a ghost removing apparatus capable of generating a filter that can prevent any video collapse as much as possible, and that can cope with any phenomenon in the world.

  In order to solve the problems of the prior art, the ghost removing apparatus of the present invention receives a video signal including a GCR signal, and compares and analyzes the waveform of the received GCR signal and the waveform of the GCR reference signal held therein. A waveform analysis unit that performs the filter analysis, a GR filter coefficient creation unit that creates a filter coefficient using a comparison analysis result by the waveform analysis unit, a GR filter unit that creates a filter from the created filter coefficient, and a field of the waveform of the video signal A unit time counting unit that counts the number and measures the elapsed time, and a GCR signal extraction unit that calculates and extracts the GCR signal from the video signal every unit time, and is generated on the transmission line by passing the received video signal through a filter In the ghost removing apparatus that removes the ghost from the video signal, the waveform analyzer uses a frequency characteristic for calculating a filter coefficient. And means for changing the which is a circuit configuration, characterized in that changing the frequency characteristics according to the time elapsed from the ghost canceling operation start.

  In the ghost removal apparatus of the present invention, the waveform analysis unit restricts the frequency band used for the filter coefficient calculation to a stable frequency band immediately after the start of the ghost removal operation, and widens the frequency band over time. Yes.

  In the ghost elimination apparatus of the present invention, the waveform analysis unit calculates a received GCR signal within a new unit time, compares the calculation result of the new received GCR signal with the received GCR signal used so far, The frequency characteristics are controlled according to the comparison result.

  In the ghost removing apparatus of the present invention, the waveform analysis unit has means for measuring the noise amount of the received video signal, and controls the frequency characteristics according to the measured noise amount of the video signal.

  In the ghost removal apparatus of the present invention, the waveform analysis unit stops the ghost removal operation according to the measured noise amount of the video signal.

  In the ghost elimination apparatus of the present invention, the waveform analysis unit has means for measuring the sag amount of the received video signal, and controls the frequency characteristics according to the measured sag amount of the video signal.

  In the ghost removal apparatus of the present invention, the waveform analysis unit stops the ghost removal operation according to the sag amount of the measured video signal.

  In the ghost removing apparatus of the present invention, the waveform analysis unit analyzes frequency change information in the transmission path of the received GCR signal, and controls frequency characteristics based on the analyzed frequency change information.

  In the ghost removing apparatus of the present invention, the waveform analysis unit changes the frequency characteristic for calculating the filter coefficient by controlling the frequency characteristic of the internal GCR reference signal.

  In the ghost removal apparatus of the present invention, the waveform analysis unit has means for executing Fourier transform when calculating the filter coefficient, and after the Fourier transform, the filter coefficient is determined by limiting the maximum gain of each frequency band. The frequency characteristic for calculation is changed.

  The ghost removing apparatus of the present invention has a configuration characterized by using a combination of a plurality of ghost removing methods described above.

  As described above, according to the present invention, when generating a filter for removing a ghost, in order to prevent generation of an erroneous filter, frequency characteristics are controlled in each block to cope with all phenomena in the transmission path. Thus, it is possible to obtain a ghost removing apparatus capable of generating a filter that prevents the video from being broken as much as possible.

  Hereinafter, a ghost removing apparatus according to the best mode for carrying out the present invention will be described in detail with reference to the drawings.

  The ghost removal apparatus of the present invention receives a video signal including a GCR (Ghost Cancel Reference) signal, and performs a waveform analysis unit 1 for performing a comparative analysis between the waveform of the received GCR signal and the waveform of the GCR reference signal held therein. A GR (ghost reducer) filter coefficient creating unit 2 that creates a filter coefficient using the comparison analysis result by the waveform analyzing unit 1, a GR filter unit 3 that creates a filter from the created filter coefficient, and a waveform of the video signal A unit time counting unit 4 that counts the number of fields and measures elapsed time, and a GCR signal extraction unit that calculates the unit time and extracts a GCR signal from the video signal.

  The ghost removing apparatus of the present invention is an apparatus that removes a ghost generated in a transmission path from a video signal by passing the received video signal through a filter.

  In the ghost removing apparatus of the present invention, the waveform analysis unit 1 has means for changing the frequency characteristics for calculating the filter coefficient.

  In the ghost removal apparatus of the present invention, the waveform analysis unit 1 changes the frequency characteristics with the passage of time from the start of the ghost removal operation.

  In the ghost removal apparatus of the present invention, the waveform analysis unit 1 limits the frequency band used for the filter coefficient calculation to a stable frequency band immediately after the start of the ghost removal operation, and widens the frequency band over time. Yes.

  In the ghost removing apparatus of the present invention, the waveform analysis unit 1 calculates a received GCR signal within a new unit time, compares the calculation result of the new received GCR signal with the received GCR signal used so far, The frequency characteristics are controlled according to the comparison result.

  In the ghost removing apparatus of the present invention, the waveform analysis unit 1 has means for measuring the noise amount of the received video signal.

  In the ghost removing apparatus of the present invention, the waveform analysis unit 1 controls the frequency characteristics according to the measured noise amount of the video signal.

  In the ghost removal apparatus of the present invention, the waveform analysis unit 1 stops the ghost removal operation according to the measured noise amount of the video signal.

  In the ghost removing apparatus of the present invention, the waveform analysis unit 1 has means for measuring the sag amount of the received video signal.

  In the ghost removing apparatus of the present invention, the waveform analysis unit 1 controls the frequency characteristics according to the measured sag amount of the video signal.

  In the ghost removal apparatus of the present invention, the waveform analysis unit 1 stops the ghost removal operation according to the sag amount of the measured video signal.

  In the ghost removing apparatus of the present invention, the waveform analysis unit 1 analyzes frequency change information in the transmission path of the received GCR signal, and controls the frequency characteristics based on the analyzed frequency change information.

  In the ghost removing apparatus of the present invention, the waveform analyzer 1 controls the frequency characteristic of the internal GCR reference signal to change the frequency characteristic for calculating the filter coefficient.

  The ghost removing apparatus of the present invention includes means for executing Fourier transform when the waveform analysis unit 1 calculates filter coefficients.

  In the ghost removing apparatus of the present invention, the waveform analysis unit 1 changes the frequency characteristics for calculating the filter coefficient by limiting the maximum gain of each frequency band after Fourier transform.

  The ghost removing apparatus of the present invention uses a plurality of the ghost removing methods described above in combination.

  In the ghost removing apparatus of the present invention, the waveform analysis unit 1 analyzes the frequency change information on the transmission path of the received GCR signal by comparing the received GCR signal with the internal GCR reference signal.

  In the ghost elimination apparatus of the present invention, the waveform analysis unit 1 analyzes the frequency change information in the transmission path of the received GCR signal by comparing the result of Fourier transform of the received GCR signal and the internal GCR reference signal. It has become.

  In the ghost removal apparatus of the present invention, the waveform analysis unit 1 controls the frequency characteristic of the received GCR signal to change the frequency characteristic for calculating the filter coefficient.

  The ghost removing apparatus of the present invention has means for the waveform analysis unit 1 to calculate the received GCR signal used so far and the received GCR signal calculated by the calculation within a new unit time. The frequency characteristic for calculating the filter coefficient is changed by controlling the frequency characteristic of the GCR signal.

  In the ghost removing apparatus of the present invention, the waveform analysis unit 1 performs Fourier transform on the internal GCR reference signal when calculating the filter coefficient, and limits the frequency band of the internal GCR reference signal after Fourier transform, thereby obtaining the filter coefficient. The frequency characteristic for calculation is changed.

  In the ghost removing apparatus of the present invention, the waveform analysis unit 1 performs a Fourier transform on the received GCR signal when calculating the filter coefficient, and calculates the filter coefficient by limiting the frequency band of the received GCR signal after the Fourier transform. For this purpose, the frequency characteristics are changed.

  In the ghost removing apparatus of the present invention, the waveform analysis unit 1 changes the frequency characteristics for calculating the filter coefficient by limiting the frequency band of the calculation result of the received GCR signal after Fourier transform and the internal GCR reference signal. It is like that.

  In the ghost removing apparatus of the present invention, the waveform analysis unit 1 calculates the filter coefficient by limiting the frequency band of the result obtained by performing the inverse Fourier transform on the calculation result of the received GCR signal after the Fourier transform and the internal GCR reference signal. The frequency characteristic of is changed.

  In the ghost removing apparatus of the present invention, the waveform analysis unit 1 applies a coefficient for correcting each frequency band gain after Fourier transform, thereby changing the frequency characteristic for calculating the filter coefficient.

  In the ghost removing apparatus of the present invention, when the waveform analysis unit 1 creates a sag reference value of a video signal, the reference value is changed between V sag and H sag.

FIG. 1 is a block diagram illustrating an example of a configuration of a ghost removing apparatus according to an embodiment of the present invention.
An example of the ghost removing apparatus of the present invention will be described with reference to FIG.
As shown in FIG. 1, the ghost removing apparatus includes a waveform analysis unit 1, a GR filter coefficient creation unit 2, a GR filter unit 3, a unit time counting unit 4, and a GCR signal extraction unit (not shown). Become.

  The waveform analysis unit 1 compares and analyzes the waveform of the input GCR signal and the waveform of the GCR reference signal provided therein, and returns the waveform of the input GCR signal to the waveform of the internal GCR reference signal. The function is calculated, and the calculation result is output to the GR filter coefficient creation unit 2.

  The GR filter coefficient creation unit 2 calculates a filter coefficient from the function.

  The GR filter unit 3 generates a filter having a filter coefficient as a result calculated by the GR filter coefficient creation unit 2, and outputs a video in which a ghost is deleted from the video signal.

  The unit time counting unit 4 counts the number of fields of the waveform of the input video signal.

  The GCR signal extraction unit calculates the GCR signal from the received video signal that is calculated every unit time.

FIG. 2 is a diagram illustrating an example of GCR 8-field sequence calculation.
First, the specification of the GCR signal will be briefly described with reference to FIG.
The reference GCR signal is on lines 18 and 281 in the vertical blanking period of the video signal.

  Then, a signal with GCR in an 8-field sequence and a signal with only a black level without GCR are sent four times each.

  The ghost elimination apparatus takes a difference based on the received 8-field sequence (with GCR: Field1, Field3, Field6, Field8, no GCR with only black level: Field2, Field4, Field5, Field7) The burst signal is removed and only the GCR signal is taken out. (See Figure 2)

  By performing a Fourier transform analysis on the information, frequency change information on the transmission path can be obtained, and a function for restoring the frequency can be created.

  Also, from the response of the differential waveform of the GCR signal, the ghost is analyzed by analyzing how much the ghost is delayed, the magnitude and phase of the ghost, and reducing the ghost at that location. Reduce.

FIG. 3 is an explanatory diagram illustrating a first example of a procedure of processing performed by the waveform analysis unit in the ghost removing apparatus according to the embodiment of the present invention.
Hereinafter, details of the waveform analysis unit 1 will be described with reference to FIG.
First, an 8-field sequence unit time (8 fields × n) of the received GCR signal y () is assumed to be y (n).
The unit time is controlled by setting the value of n.

The new calculation result y (n) is added to the previous result yo (n).
At this time, a reflection ratio a indicating how much the new calculation result is reflected in the previous result is set.
Therefore, yo (n) = (1−a) × yo (n) + a × y (n).

Incidentally, when 100% of the new calculation result is used, a = 1 and yo (n) = y (n).
Of course, when no new calculation result is used, a = 0 and yo (n) = yo (n).

  Next, let Yo (k) be the result of Fourier transform of yo (n).

  The internal GCR reference signal is x (), and the Fourier transform result of the internal GCR reference signal is X (k).

  Using the Fourier transform results of the received GCR signal and the internal GCR reference signal, the channel frequency response is Z (k) = Yo (k) / X (k).

  The result of inverse Fourier transform of the channel frequency response Z (k) is the channel impulse response z (n).

  This channel impulse response z (n) is passed to the GR filter coefficient creation unit 2.

  As for a filter of a general ghost removing apparatus, an FIR (Finite Impulse Response) filter is used for a near ghost, and an Infinite Impulse Response (IIR) filter is used for a far ghost.

  The GR filter coefficient creation unit 2 that has received z (n) is processed by dividing into a near ghost and a far ghost, and ideal FIR filter coefficients and IIR filter coefficients are designed.

  And the value of a filter coefficient is set in GR filter part 3, and a filter is generated.

  In FIG. 3, the frequency characteristics for calculating the filter coefficient are changed by comparing the elapsed time, yo (n) and y (n), noise, sag, and the like.

FIG. 4 is an explanatory diagram illustrating an example 2 of a procedure of processing performed by the waveform analysis unit in the ghost removing apparatus according to the embodiment of the present invention.
Here, as shown in FIG. 4, as an example of the frequency change information, GCR change information can be calculated by gcr (n) = x () −y (n).

  The processing procedure performed by the waveform analysis unit shown in FIG. 4 is almost the same as that in FIG.

FIG. 5 is an explanatory diagram illustrating an example 3 of a procedure of processing performed by the waveform analysis unit in the ghost removing apparatus according to the embodiment of the present invention.
Here, as shown in FIG. 5, the frequency change information after Fourier transform is F (k) = X (k) −Yo (k).

  The processing procedure performed by the waveform analysis unit shown in FIG. 5 is substantially the same as that in FIG.

The ghost removing apparatus of the present invention has the following features.
(1) In the ghost removing apparatus of the present invention, the waveform analysis unit 1 changes the frequency characteristic for calculating the filter coefficient according to the passage of time from the start of the ghost removing operation.

  As a method of changing the frequency characteristics, in the case of FIG. 3, the block of y (n), yo (n), Yo (k), Z (k), z (n), x (), X (k), etc. There is a method for controlling the frequency characteristics.

  For example, it is possible to limit the frequency by filtering the received GCR signal y (n) per unit time.

  Further, the frequency characteristic of the generated filter can be changed by multiplying the result of the Fourier transform by limiting the frequency band.

  For example, by limiting the high frequency component, it is possible to prevent image quality degradation due to high frequency noise enhancement.

  Also, by applying a small coefficient to weaken the improvement level, it is possible to prevent the video from being broken during a strong ghost.

  Furthermore, if it is determined from the GCR change information and frequency change information shown in FIGS. 4 and 5 that the ghost of the received GCR signal is very large, there is a greater possibility that an erroneous filter will be generated. k) is multiplied by a small coefficient or the maximum gain is limited to prevent generation of a false filter.

(2) In the ghost removal apparatus of the present invention, the waveform analysis unit 1 limits the frequency band used for the filter coefficient calculation to a stable frequency band immediately after the start of the ghost removal operation, and widens the frequency band over time.

  At the start of the ghost removal operation, the filter coefficient is not stable, so the frequency band to be used is limited, and the filter is generated using only the stable frequency band.

  When the filter coefficient becomes stable, the frequency band is gradually widened.

(3) In the ghost removing apparatus of the present invention, the waveform analysis unit 1 calculates a received GCR signal within a new unit time, and calculates a new received GCR signal calculation result and the received GCR signal used so far. The frequency characteristics are controlled according to the comparison result.

  That is, in FIG. 3, the new calculation result y (n) is compared with the previous result yo (n) to control the frequency characteristics of each block.

  For example, when y (n) is significantly different from yo (n), there is a high possibility that a noise component is suddenly added to y (n), and therefore the frequency of y (n) is limited.

(4) In the ghost removing apparatus of the present invention, the waveform analysis unit 1 measures the amount of noise of the received video signal and controls the frequency characteristics of each block according to the measured amount of noise of the video signal.

For example, when there is a lot of noise, the high frequency component is limited.
This prevents the generation of an erroneous filter due to noise.

  There are many methods for detecting the amount of noise, and no particular definition is provided here.

  For example, the amount of noise can be confirmed by taking the difference between two GCR-containing signals from the reference GCR signal.

  Of course, the amount of noise can be confirmed in the same manner by taking the difference between the signals without GCR that are sent only at the black level.

(5) In the ghost removing apparatus of the present invention, the waveform analysis unit 1 measures the sag amount of the received video signal, and controls the frequency characteristics of each block according to the measured sag amount of the video signal.

  For example, when the sag is large, the frequency is controlled so as to reduce the strength of ghost removal.

  In addition, there is no special regulation regarding the detection method of the sag amount.

  For example, it is possible to detect the sag amount from the change amount of the bottom of the synchronization of each field or each line.

  When determining the sag reference value, it is effective to change the reference value between the V sag and the H sag.

(6) In the ghost removing apparatus of the present invention, the waveform analysis unit 1 analyzes the frequency change information on the transmission path of the received GCR signal, and controls the frequency characteristics of each block based on the analyzed frequency change information.

  For example, when a strong ghost is generated in the transmission path, the possibility of generating an erroneous filter increases. Therefore, the generation of an erroneous filter is prevented by limiting the frequency used for calculation.

  For example, when the strength at an arbitrary frequency f is d, if the frequency is greater than a certain threshold, the frequency component is not corrected for the input signal.

  For example, there are methods such as deleting or reducing the frequency components of Yo (k) and Z (k).

Further, the limit amount is controlled according to the value of d.
For example, when d is large, the frequency component of f in Z (k) is halved.
When d is larger, the frequency component of f of Z (k) is set to 1/3.

  It is also possible to use an average value of an arbitrary frequency range or the entire frequency region instead of an arbitrary frequency.

(7) In the ghost removing apparatus of the present invention, the waveform analysis unit 1 analyzes the frequency change information on the transmission path of the received GCR signal by comparing the received GCR signal with the internal GCR reference signal.

That is, as shown in FIG. 4, the received GCR signal is compared with the internal GCR reference signal as means for obtaining frequency change information on the transmission line.
Based on GCR change information which is an example of the frequency change information, frequency control of each block is performed.

(8) In the ghost removal apparatus of the present invention, the waveform analysis unit 1 analyzes the frequency change information on the transmission path of the received GCR signal by comparing the results of Fourier transform of the received GCR signal and the internal GCR reference signal. .

That is, as shown in FIG. 5, as a means for obtaining frequency change information on the transmission path, the result of Fourier transform of the received GCR signal and the GCR reference signal held therein is compared.
Based on the frequency change information, frequency control of each block is performed.

(9) In the ghost removal apparatus of the present invention, the waveform analysis unit 1 changes the frequency characteristic for calculating the filter coefficient by controlling the frequency characteristic of the internal GCR reference signal.

  That is, the frequency characteristics of the internal GCR reference signal x () are controlled in FIGS.

For example, the high frequency of the internal GCR reference signal x () is limited by a low-pass filter.
As a result, in the ghost removal operation, the limited high-frequency component is ignored, so that the high-frequency component is not corrected, but there is no failure such as noise amplification of the high-frequency component.

(10) In the ghost removing apparatus of the present invention, the waveform analysis unit 1 changes the frequency characteristic for calculating the filter coefficient by controlling the frequency characteristic of the received GCR signal.

  That is, the frequency characteristics of the received GCR signal y (n) are controlled in FIGS.

(11) In the ghost removing apparatus of the present invention, the waveform analysis unit 1 controls the frequency characteristic of the GCR signal after the calculation to change the frequency characteristic for calculating the filter coefficient.

  That is, the frequency characteristics of the GCR signal yo (n) after calculation are controlled in FIGS.

(12) In the ghost removing apparatus of the present invention, the waveform analysis unit 1 performs Fourier transform on the internal GCR reference signal when calculating the filter coefficient, and limits the frequency band of the internal GCR reference signal after Fourier transform. The frequency characteristic for calculating the filter coefficient is changed.

  That is, the frequency characteristic of the internal GCR reference signal X (k) after Fourier transform is controlled in FIGS.

(13) In the ghost removing apparatus of the present invention, the waveform analysis unit 1 performs a Fourier transform on the received GCR signal when calculating the filter coefficient, and limits the frequency band of the received GCR signal after the Fourier transform. The frequency characteristic for calculating is changed.

  That is, the frequency characteristic of the received GCR signal Yo (k) after Fourier transform is controlled in FIGS.

(14) In the ghost removing apparatus of the present invention, the waveform analysis unit 1 uses the frequency characteristics for calculating the filter coefficient by limiting the frequency band of the calculation result of the received GCR signal and the internal GCR reference signal after the Fourier transform. To change.

  That is, the frequency characteristics of the calculation result Z (k) of the received GCR signal after the Fourier transform and the internal GCR reference signal are controlled in FIGS.

(15) In the ghost removing apparatus of the present invention, the waveform analysis unit 1 limits the frequency band of the result obtained by performing inverse Fourier transform on the calculation result of the received GCR signal after Fourier transform and the internal GCR reference signal, thereby reducing the filter coefficient. The frequency characteristic for calculation is changed.

  That is, in FIG. 3, 4, and 5, the frequency characteristic of the result z (n) obtained by performing inverse Fourier transform on the calculation result of the received GCR signal after Fourier transform and the internal GCR reference signal is controlled.

(16) In the ghost removing apparatus of the present invention, the waveform analysis unit 1 changes the frequency characteristic for calculating the filter coefficient by applying a coefficient for correcting each frequency band gain after Fourier transform.

That is, the frequency characteristics of the filter are controlled by applying coefficients to Yo (k), x (), Z (k), etc. in FIGS.
For example, adjustment is possible by applying a coefficient b such as b * Z (k).

(17) In the ghost removing apparatus of the present invention, the waveform analysis unit 1 changes the frequency characteristics for calculating the filter coefficient by limiting the maximum gain of each frequency band after Fourier transform.

  That is, in FIGS. 3, 4, and 5, the maximum gains such as Yo (k), x (), Z (k) are limited.

For example, when the ghost of the received GCR signal is very large due to frequency change information or GCR change information after Fourier transform, there is a high possibility that an erroneous filter is generated as it is.
Therefore, limiting the maximum gain of Z (k) prevents the generation of an erroneous filter.

(18) In the ghost removal apparatus of the present invention, the waveform analysis unit 1 stops the ghost removal operation according to the measured noise amount of the video signal.

If the ghost removal operation is performed when there is a lot of noise, the possibility of generating an erroneous filter increases.
Therefore, when the noise is equal to or higher than a reference value, the ghost removal operation is stopped.

(19) In the ghost removal apparatus of the present invention, the waveform analysis unit 1 stops the ghost removal operation according to the measured sag amount of the video signal.
If the ghost removal operation is performed when the sag is large, the possibility of generating a false filter increases.
Therefore, when the sag is greater than a certain reference value, the ghost removal operation is stopped.

  When determining the sag reference value, it is effective to change the reference value between the V sag and the H sag.

(20) In the ghost removing apparatus of the present invention, when the waveform analysis unit 1 creates the sag reference value, the reference value is changed between the V sag and the H sag.

  Here, the V sag is a sag generated for each field, and the H sag is a sag generated for each line.

The block diagram which shows an example of a structure of the ghost removal apparatus which concerns on the Example of this invention. The figure which shows an example of 8 field sequence calculation of GCR. Explanatory drawing which shows Example 1 of the procedure of the process performed in the waveform analysis part in the ghost removal apparatus which concerns on the Example of this invention. Explanatory drawing which shows Example 2 of the procedure of the process performed in the waveform analysis part in the ghost removal apparatus which concerns on the Example of this invention. Explanatory drawing which shows Example 3 of the procedure of the process performed in the waveform analysis part in the ghost removal apparatus which concerns on the Example of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Waveform analysis part 2 GR filter coefficient preparation part 3 GR filter part 4 Unit time count part

Claims (11)

A waveform analysis unit that receives a video signal including a GCR signal, performs a comparative analysis between the waveform of the received GCR signal and the waveform of the GCR reference signal that is internally contained therein, and a filter using the comparison analysis result by the waveform analysis unit A GR filter coefficient creating section for creating coefficients, a GR filter section for generating a filter from the created filter coefficients, a unit time counting section for counting the number of fields of the waveform of the video signal and measuring the elapsed time, and for each unit time In a ghost removing apparatus that comprises a GCR signal extraction unit that calculates and extracts a GCR signal from a video signal, and removes a ghost generated in the transmission path from the video signal by passing the received video signal through a filter.
The ghost removal apparatus, wherein the waveform analysis unit has means for changing a frequency characteristic for calculating a filter coefficient, and changes the frequency characteristic with the passage of time from the start of the ghost removal operation.   2. The ghost removing apparatus according to claim 1, wherein the waveform analyzing unit restricts a frequency band used for calculation of a filter coefficient to a stable frequency band immediately after the start of the ghost removing operation, and widens the frequency band over time.   The waveform analysis unit calculates a received GCR signal within a new unit time, compares the calculation result of the new received GCR signal with the received GCR signal used so far, and determines the frequency characteristics according to the comparison result. The ghost removing device according to claim 1, wherein the ghost removing device is controlled.   The ghost removing apparatus according to claim 1, wherein the waveform analysis unit includes means for measuring a noise amount of the received video signal, and controls the frequency characteristics according to the measured noise amount of the video signal.   The ghost removing apparatus according to claim 4, wherein the waveform analyzing unit stops the ghost removing operation according to the measured noise amount of the video signal.   The ghost removing apparatus according to claim 1, wherein the waveform analysis unit includes means for measuring a sag amount of the received video signal, and controls the frequency characteristics according to the measured sag amount of the video signal.   The ghost removing apparatus according to claim 5, wherein the waveform analyzing unit stops the ghost removing operation according to the sag amount of the measured video signal.   The ghost removing apparatus according to claim 1, wherein the waveform analysis unit analyzes frequency change information on a transmission path of a received GCR signal and controls frequency characteristics based on the analyzed frequency change information.   The ghost removing apparatus according to claim 1, wherein the waveform analysis unit changes a frequency characteristic for calculating a filter coefficient by controlling a frequency characteristic of an internal GCR reference signal.   The waveform analysis unit has means for executing a Fourier transform when calculating the filter coefficient, and after the Fourier transform, the frequency characteristics for calculating the filter coefficient are changed by limiting the maximum gain of each frequency band. The ghost removing apparatus according to claim 1.   11. A ghost removing apparatus using a plurality of the ghost removing methods according to claim 1 in combination.