JPH0522635A - Reference signal identification/extraction method - Google Patents

Abstract

PURPOSE:To attain the accurate detection of a reference signal even with addi tion of a ghost by identifying the reference signal after extracting four types of parameters such as the signal waveform width, the steep degree, the differen tial sum and the differential element number from the signal to be identified. CONSTITUTION:An output is generated from an AND circuit 15 and a pulse signal is decided with the small signal waveform width W, the large steep degree DN, the large differential sum DLN, and the large differential element number DE, respectively. Then, an output is generated from an AND circuit 16 and a bar signal is decided with the large width W, the small steep degree DN, the small sum DLN, and the small number DE, respectively. Furthermore, an output is generated from an AND circuit 17 and a color bar waveform or a staircase wave is decided with the large width W, the medium sharpness DN, the small sum DLN, and the medium number DE, respectively. In such a constitution, the waveform of a VITS(vertically inserted test signal) is accurately identified. Then the VITS is used for equalization of waveforms as long as the VITS serves as a reference signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reference signal identifying and extracting method for identifying and extracting a reference signal required for waveform equalization from VITS (Vertical inserted test signal) signals included in television transmission waves.

[0002]

2. Description of the Related Art Generally, a ghost exists as one of the causes of image quality deterioration in television. In order to remove this ghost, it is effective to make full use of digital signal processing using a transversal filter. In this digital signal processing, a certain signal is used as a reference signal, the reference signal and the incoming signal are compared, and waveform equalization is performed to match the waveform of the incoming signal with the reference signal waveform. In the case of terrestrial broadcasting in Japan, a signal defined at a fixed position as a GCR signal is inserted as a reference signal required for this waveform equalization.

On the other hand, also in the case of CATV, since there are proximity ghosts due to transmission system distortion, pre-ghosts due to direct wave interference, and normal ghosts that occur when receiving a terrestrial broadcasting station, a waveform equalization technique is required. When performing waveform equalization in CATV, the problem is what to do with the reference signal. That is, a reference signal having a sufficient frequency characteristic is not inserted at a fixed position within the vertical blanking period as in Japanese terrestrial broadcasting. Therefore, in order to select a reference signal from the VITS signals inserted for testing within the vertical blanking period, the reference signal identification and extraction function is required.

The VITS signal has a different signal waveform and position depending on the broadcasting station, and a signal processing process for automatically identifying and extracting the reference signal is required. A typical waveform of the VITS signal is shown in FIG. 5 is a pulse waveform, 6 is a bar waveform, 7
Is a gradation wave, and 8 is a color bar waveform. Also, a _{0 to} a ₃
Indicates the start point of each waveform 5 to 8, and b _{0 to} b ₃ indicates the end point of each waveform 5 to 8. Of these VITS signals, it is known that the pulse waveform 5 and the bar waveform 6 are effective as the reference signal. Therefore, a process of extracting the pulse waveform 5 or the bar waveform 6 from the VITS signal is required.

As this identification and extraction method, there is a method of obtaining the difference from the reference signal. FIG. 3A shows the amplitude P, the starting point a ₁ ,
A bar signal at the end point b ₁ is shown, and this signal is used as a reference signal f (x) for bar waveform extraction. Identification target signal g ′
When the VITS signal (x) is a signal represented by the amplitude q, the start point a, and the end point b ₁ as shown in FIG. 3B, if the difference from the reference signal is obtained as it is, it becomes a large value. An erroneous judgment occurs. Therefore, the identification target signal g ′
It is necessary to standardize (x).

The identification target signal g standardized in FIG.
(X) is shown. g (x) is amplitude P, start point a ₁ , end point b ₁
And the bar waveform having the same characteristics as the reference signal can be obtained.

[0007]

[Equation 1]

The difference value between the identification object signal g (i) and the reference signal f (i), which are standardized as shown in the equation 1, is added, and when the difference value is small, the identification object signal g (x) is barred. It can be recognized as a signal.

FIG. 4 shows a block configuration of the above-mentioned discrimination processing, in which the VITS signal as the discrimination target signal is standardized by the normalization circuit 1.
And the difference processing circuit 3 performs difference processing with the bar waveform reference signal, and the value Sb is used as a threshold value processing circuit 4.
, And if Sb is below the threshold value, it is recognized as a bar waveform,
If Sb is equal to or more than the threshold value, it is recognized as a signal other than the bar signal.

Next, consider the case where a ghost is added to the VITS signal which is the identification target signal. FIG. 5 (a) shows a reference bar waveform f (x), and FIG. 5 (b) shows an identification target standardized signal g (x) of the ghost-added bar waveform. As is clear from FIG. 5, when the ghost is added even in the bar waveform, f (x) and g (x)
The difference value Sb of is large, and an erroneous determination occurs in which the identification target signal g ′ (x) is not recognized as a bar waveform. Therefore,
For a bar waveform with a ghost, the frequency of erroneous determination increases as the amplitude and delay time increase, and the difference value S
The method of finding b was not a good method.

FIG. 6 shows another conventional reference signal identification and extraction method, in which 9 is a counter and 10 is a line memory. After resetting the counter 9 by the external synchronization signal (vertical synchronization separation signal) E, the counter 9 clocks the clock signal f _C.
The counting operation of is executed. The clock signal f _C has a horizontal synchronizing frequency f _H, for example. When performing waveform equalization, a reference signal which is the basis of calculation must be selected and extracted, but the counter 9 outputs a select signal to a position of an arbitrary number of lines in the field for one line period. The select signal SEL becomes a write enable signal in the line memory 10, and a predetermined reference signal is written in the memory and used for calculation. In this way, the counter 9 displays the select signal SEL at the position of the predetermined number of lines.
Is output and the reference signal is extracted.

[0012]

The conventional reference signal identification and extraction method is as described above, and the difference value Sb from the reference signal becomes large with respect to the identification target signal to which the ghost is added, and the error is erroneous. There was a problem of making a decision. or,
If the vertical sync separation signal E is missing or contains noise, the counter 9 malfunctions and a predetermined reference signal cannot be extracted.

The present invention has been made in order to solve the above problems, and even if a ghost-added identification target signal, the vertical sync separation signal is missing or contains noise. It is an object of the present invention to obtain a reference signal identification and extraction method that does not cause misjudgment even in cases.

[0014]

A reference signal identification and extraction method according to the present invention is provided with a signal waveform width of a VITS signal, steepness,
The reference signal is discriminated and extracted using four parameters of differential sum and the number of differential elements.

Further, the reference signal identifying and extracting method according to the present invention determines the left-right symmetry of the VITS signal, and when it is symmetric, it is left as it is, and when it is asymmetric, smoothing processing is performed, and then VI.
The difference processing between the TS signal and the reference signal is performed, and when the difference processed value is equal to or less than a predetermined value, the reference signal is identified and extracted.

Further, the reference signal identifying and extracting method according to the present invention is provided with a counter for outputting a select signal for identifying and extracting the reference signal, and this counter provides a self-excited trigger signal and a window having the same period as the vertical synchronization separation signal. Signals are generated simultaneously, the counter is reset by the vertical sync separation signal when the vertical sync separation signal is outside the window and the phase difference from the self-excitation trigger signal is constant, and in other cases, the counter is started by the self-excitation trigger signal. It is to reset.

[0017]

In the present invention, four parameters are extracted from the VITS signal, and it is determined by these parameters whether or not the signal is the reference signal.

Further, in the present invention, when the VITS signal is asymmetric due to a ghost or the like, it is compared with the reference signal after being smoothed, and when the difference is small, it is determined as the reference signal.

Further, according to the present invention, the counter for generating the select signal for identifying and extracting the reference signal simultaneously outputs the self-excited trigger signal and the window signal having the same period as the vertical sync separation signal, and the vertical sync separation signal. Is outside the window and the phase difference from the self-exciting trigger signal is constant, the counter is reset by the vertical sync separation signal, and in other cases, the counter is reset by the self-exciting trigger signal.

[0020]

Embodiment 1 An embodiment of the present invention will be described below with reference to the drawings. In this embodiment, necessary parameters are used to identify and extract a necessary reference signal from the VITS signal. First,
The first parameter is the signal waveform width W, which indicates the distance (time width) between the start point a and the end point b of the signal, and (2)
Shown in formula W = | b−a | (2) The signal waveform width W has a large value for a bar waveform, a color bar waveform, and a staircase wave, but has a small value for a pulse waveform.

The second parameter is a parameter indicating the steepness D _N. This parameter is shown in Equation 2.

[0022]

[Equation 2]

The maximum value in the signal waveform f (x) is defined as P _N, and the maximum values are arranged in order from P _N , P _N-1 , P _N-2 , ..., P _Ni , ... P _N and i
The parameter value D _N indicating the steepness of the signal waveform is obtained by taking the difference with the second largest value P _Ni and adding them in order. In addition, in Equation 2, the addition result is divided by P _N · β to perform normalization. Parameter D
_N has a large value in the case of a pulse waveform, a small value in the case of a bar waveform, and an intermediate value between the case of a pulse waveform and the case of a bar waveform in the case of a color bar waveform and a staircase wave.

Next, the parameters extracted from the signal waveform obtained by differentiating the original signal will be described. The VITS signal waveform f (x) and its differential waveform f ′ (x) are shown in FIG.
It shows in (b). Equation 3 shows the third parameter value DL _N using this differential signal.

[0025]

[Equation 3]

DL _N represents the sum of the absolute values of the differential values, and DP _N represents the maximum value of the differential waveform f '(x). Number 3
In by dividing the maximum value DP _N and signal width b-a, it is performed standardized. The parameter DL _N has a large value for a pulse signal, but has a small value for a bar signal, a color bar signal, and a staircase wave.

The fourth parameter DE represents the number of elements having a level value above a certain threshold value in the differential waveform, and can be expressed by equation 4.

[0028]

[Equation 4]

In the above equation, α is a positive integer, and the parameter DE indicates the number of elements whose differentiated value is larger than α. The parameter DE shows a small value for the bar waveform and a large value for the pulse waveform. Further, it shows an intermediate value for the color bar waveform and the staircase wave. Table 1 shows the values of each parameter for each waveform of the VITS signal.
Are shown together.

[0030]

[Table 1]

FIG. 1 shows a configuration for identifying the reference signal from the VITS signal based on Table 1. There are four types of waveforms to identify: pulse waveform, bar waveform, color bar waveform, and staircase waveform. 11 detection section for detecting a signal waveform width W of the VITS signal, 12 detector for detecting a steepness D _N of the VITS signal, 13 detector for detecting the differential sum DL _N of VITS signal, 14 of the VITS signal Detectors 15 to 17 for detecting the number DE of differential elements are AND circuits to which the outputs of the detectors 11 to 14 are selectively input.

In the configuration of FIG. 1, the signal waveform width W is small,
When the steepness D _N is large, the differential sum DL _N is large, and the number of differential elements DE is large, an output is generated from the AND circuit 15 and it is determined to be a pulse signal. Further, when the signal waveform width W is large, the steepness _DN is small, the differential sum DL _N is small, and the number of differential elements DE is small, an output is generated from the AND circuit 16 and it is determined to be a bar signal.
Furthermore, the signal waveform width W is large, the steepness D _N is medium, and the differential sum D is
AND circuit 17 when L _N is small and the number of differential elements DE is medium
Generates an output and determines that it is a color bar waveform or a staircase wave. In this way, the waveform of the VITS signal is accurately identified, and if the identified signal is the reference signal, waveform equalization is performed using this signal.

Embodiment 2 FIG. 8 is a block diagram for carrying out the discrimination processing of the reference signal from the VITS signal according to the embodiment 2, 18 is a symmetry judging section for checking the left-right symmetry of the VITS signal which is the discrimination object signal, 19 Is a smoothing processing unit that executes a smoothing process of adding the value of the last part of the VITS signal to the value of the first part when the VITS signal is asymmetrical, and 20 is the VITS signal and its smoothing process based on the symmetry determination result. This is a switch that switches between and.

Next, the operation will be described. When a ghost is added to the bar signal which is the identification target signal, FIG.
The waveform is as shown in (a), and the waveform is distorted so that the waveform becomes asymmetric. To correctly recognize this waveform as a bar signal,
It is necessary to correct this asymmetric bar signal. The smoothing processing unit 19 plays this role. First, the discrimination target signal g (x) is differentiated and then converted into an absolute value.
Obtain | g '(x) | shown in (b). This | g '
In (x) |, the differential value corresponding to the trailing falling edge of the bar waveform exists at the position of β.

Also, a small value is generated at the position of the waveform end point b due to the distortion due to the ghost component. By detecting and scanning the data of | g ′ (x) | from the end, the positions β, b
Can be asked. The range from β to b indicates the range of the distorted portion due to the influence of the ghost. Figure 9
(C) shows the smoothing process, in which the data from β to b are added in order from the head position of the waveform g (x), and the process shown in Formula 5 is performed.

[0036]

[Equation 5]

As shown in the above equation, the smoothing processing of adding and moving the protruding ghost component existing at the end of the waveform to the beginning of the waveform can generate a bar waveform without distortion at the start point a and the end point β. it can. This smoothing process is not performed on the left-right symmetric bar signal that does not include the ghost, but only on the left-right asymmetric bar signal that includes the distortion due to the ghost. Therefore, the symmetry determination unit 18 that determines whether the identification target signal is bilaterally symmetrical is required.
In order to investigate this left-right symmetry, the parameter value shown in Expression 6 is used. P is the maximum value of the reference signal f (x).

[0038]

[Equation 6]

The above-mentioned parameter E _N is calculated. When E _N is small, it can be regarded as a left-right symmetrical type, and when it is large, it can be regarded as a left-right asymmetrical type. These operations will be described with reference to FIG.
The symmetry determination unit 18 determines the left-right symmetry of the signal to be identified, and switches the switch 20 according to the result. In the case of left-right symmetry, the identification target signal passes through the switch 20 as it is, but in the case of left-right asymmetry, it passes through the switch 20 via the smoothing processing unit 19.

When the signal to be identified is a bar waveform including a ghost, the waveform g _N (x) shown in FIG. 10B passes through the switch 20. This signal is standardized by the standardization circuit 1 and has a waveform g _NL (x) shown in FIG.
This signal g _NL (x) is output to the difference processing circuit 3 in FIG.
Difference processing with the bar signal which is the reference signal f (x) shown in (a) is executed, the value Sb is compared with the threshold value in the threshold processing circuit 4, and when Sb is smaller than the threshold value, it is an identification target signal. The VITS signal is recognized as a bar signal, and when it is large, it is recognized as other than the bar signal.

On the other hand, when the recognition target signal is a color bar, a staircase wave, etc., even if the smoothing process is executed, it does not become a shaped waveform as shown in FIG.
Is a large value, and it is recognized that it is not a bar signal.
In the case of a symmetrical wave, it is recognized as a bar waveform as in the conventional case shown in FIG. As described above, the bar signal is originally a symmetric signal, but even if the signal becomes an asymmetric signal due to the addition of the ghost, the smoothing process removes the ghost distortion and performs shaping, which is recognized as a bar signal. To be done.

Third Embodiment FIG. 11 is a block diagram for performing a reference signal discrimination process from a VITS signal according to the third embodiment. Reference numeral 21 is a window generator, 22 is a phase difference detection / judgment device, 23 and 24 are AND circuits, and 25. Is an OR circuit.

FIG. 12 is a flow chart showing the operation according to this embodiment. First, the operation is started by turning on the power or switching the channel, and in step 1, the counter 9 starts counting. The counter 9 is adapted to generate the self-excited trigger I at the count number corresponding to the vertical synchronization period T. At the same time, in step 2, the counter 9 also generates a window output W near the self-excited trigger I. This situation is shown in FIG. In step 3, it is determined whether or not the external synchronization signal E is input. If it is not input, the process proceeds to step 7, and the self-excitation trigger I output from the counter 9 resets the signal.

When the external synchronizing signal E is input, the routine proceeds to step 4, where it is judged whether or not the external synchronizing signal E is in the window output W, and if it is present, it is recognized as a correct synchronizing signal. , In step 7, reset by self-excited trigger I. When the external synchronizing signal E is not in the window output W, the routine proceeds to step 5, where it is judged whether the phase difference between E and I is equal. That is, when the external synchronizing signal E is outside the window W, the phase difference between E and I is T ₁ , T in FIG.
_It becomes ₂ and the phase difference is not fixed. In this case, the external synchronization signal E is determined to be noise, and the process proceeds to step 7 to reset by the self-excited trigger I.

On the other hand, as shown in FIG. 13B, when E is outside the window W and the phase difference T ₁ between E and I is equal over several fields, the external synchronization signal E is determined to be correct. Then, the process proceeds to step 6 and resets with the signal E. For this determination, the accuracy is higher when the determination is performed several times than twice. Further, the counter 9 generates the self-excited trigger I every vertical synchronization signal T seconds, but if E is a correct external synchronization signal at this time, the incoming E will enter the window W thereafter. E in the window W
Are ignored as shown in step 4. Therefore, at this time, the self-excited trigger I continues to be used as a correct reset signal.

Next, the operation will be described with reference to FIG. The counter 9 counts the clock f _C and is reset by the R terminal input. Further, the counter 9 outputs a self-excited trigger I for each predetermined count value, and when the external synchronization signal E is not input, the self-excited trigger 1 is input to the R terminal via the OR circuit 25,
Reset yourself. Therefore, the counter 9 is repeatedly reset at each cycle of the self-excited trigger I.

Further, the window W is simultaneously generated from the counter 9 through the window generator 21, and when E arrives outside the window W, the external synchronizing signal E passes through the AND circuit 23. The phase difference detection / determination unit 22 receives E and I and detects the phase difference. When the phase difference is constant, the external synchronization signal E is determined to be a correct signal, and E is the AND circuit 24,
It is input to the R terminal of the counter 9 via the OR circuit 25,
The counter 9 is reset. If the phase difference is not constant, the external synchronization signal E is determined to be noise, and the counter 9 is not reset by E. In this way, the counter 9 operates properly even when the external synchronization signal E is missing or when there is noise, and the select signal for extracting the reference signal is also correctly output from the counter 9 and no malfunction occurs.

[0048]

As described above, according to the present invention, the discrimination operation is performed using the parameters effective for the reference signal discrimination extraction, and the waveform is shaped by the smoothing process when the discrimination target signal is asymmetrical. Therefore, the reference signal can be accurately identified and extracted even for a signal having a waveform distortion due to the addition of a ghost.

When the vertical sync separation signal is missing or contains noise, the counter is reset by the self-excited trigger signal generated by itself.
The counter always operates correctly, the select signal for extracting the reference signal can be accurately output, and the reference signal can be accurately extracted.

[Brief description of drawings]

FIG. 1 is a configuration diagram according to a first embodiment of the method of the present invention.

FIG. 2 is a waveform diagram of a VITS signal.

FIG. 3 is an explanatory waveform diagram of a conventional method.

FIG. 4 is a configuration diagram of a conventional method.

FIG. 5 is a waveform diagram of a bar signal.

FIG. 6 is a block diagram of another conventional method.

FIG. 7 is a waveform diagram of a VITS signal and its differential signal according to the first embodiment of the present invention.

FIG. 8 is a configuration diagram according to a second embodiment of the method of the present invention.

FIG. 9 is an explanatory diagram of a smoothing processing operation according to the second embodiment of the present invention.

FIG. 10 is a waveform diagram illustrating an operation according to the second embodiment of the present invention.

FIG. 11 is a configuration diagram according to a third embodiment of the present invention.

FIG. 12 is a flowchart showing an operation according to the third embodiment of the present invention.

FIG. 13 is a time chart showing an operation according to the third embodiment of the present invention.

[Explanation of symbols]

1 standardization circuit 2 reference signal 3 Difference processing circuit 4 Threshold processing circuit 11 Signal width detector 12 Steepness detector 13 Differential sum detector 14 Differential element number detector 15-17, 23, 24 AND circuit 18 Symmetry determination unit 19 Smoothing processing unit 20 switches 21 wind generator 22 Phase difference detector 25 OR circuit

Claims (3)

[Claims] 1. In a television receiver performing waveform equalization using any of VITS signals included in a television transmission wave as a reference signal, a signal waveform width indicating a time width from a start point to an end point of the signal, the signal and its maximum value. The steepness that expresses the steepness of the signal by obtaining the difference from the value, the original signal is differentiated, the differential sum obtained by adding the values of this differential signal, and the number of elements having a value greater than or equal to a predetermined value in the differential signal Number of differential elements to show 4
A reference signal identification and extraction method characterized by identifying a reference signal using a parameter of a type. 2. A television receiver that performs waveform equalization using any one of VITS signals included in a television transmitted wave as a reference signal, determines the left-right symmetry of the signal, and when the signal is symmetrical, In the case of asymmetry, after performing the smoothing process of adding the value of the last part of the signal to the value of the first part to shape the waveform distortion due to the ghost, the difference process between the signal and the reference signal is performed, and the difference process value A reference signal identification and extraction method for identifying a reference signal when is less than or equal to a predetermined value. 3. A television receiver that performs waveform equalization using any one of VITS signals included in a television transmission wave as a reference signal is provided with a counter that generates a select signal for identifying and extracting the reference signal. Generates a self-exciting trigger signal having the same period as the vertical sync separation signal and a window output at the same time, the vertical sync separation signal is outside the window, and the phase difference between the vertical sync separation signal and the self-excitation trigger signal is equal over several fields. A reference signal identification and extraction method characterized in that the counter is reset by a vertical sync separation signal, and the counter is reset by a self-excited trigger signal in other cases.