JPH10224816A - Digital y/c separation circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To optimally separate luminance signal and chrominace signal according to the correlation between a pixel of interest and a peripheral pixel by detecting vertical and horizontal correlations based on pixel data between the pixel of interest and the peripheral pixel, picks out the chrominance signal by BPF at the time of judging correlation to be low, and subtracting this from an NTSC signal so as to obtain the luminance signal. SOLUTION: A correlation detection judging part 20 compares the level difference between the pixel of interest and the peripheral pixel of the same phase of the chrominance signal as this with a reference value to judge the presence/absence of correlation. When correlation is low, a data composing and selecting part 22 selects the luminance signal and the chrominance signal from a BPF Y/C separation part 18 to output to output terminals 24, 26, and subtracts the color signal sampled by BPF from the NTSC signal to obtain the luminance signal. When correlation is high, the luminance and chrominance signals separated by vertical or horizontal comb line filters 14 and 16 are outputted to output terminals 24 and 26.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to a digital NTS.
C (National TelevisionSystem)
The present invention relates to a digital Y / C separation circuit for separating a luminance signal and a chrominance signal from a digital NTSC signal. This NTSC signal represents an NTSC composite color television signal.

[0002]

2. Description of the Related Art A conventional digital Y / C separation circuit separates a luminance signal and a chrominance signal from a digital NTSC signal by using a vertical comb filter or a band pass filter (BPF).

[0003]

However, since a luminance signal and a chrominance signal are separated from a digital NTSC signal by using a vertical comb filter or a BPF, the luminance signal and the chrominance signal are not correlated in the vertical direction. There is a problem that the signals cannot be sufficiently separated. For example, in an image having a horizontal edge, there is a problem that the original luminance signal and color signal cannot be obtained.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and has been developed in consideration of a digital Y / Y signal capable of optimally separating a luminance signal and a color signal according to the correlation between a target pixel and peripheral pixels.
It is an object to provide a C separation circuit.

[0005]

According to the present invention, there is provided a digital Y / C separation circuit for separating a luminance signal and a chrominance signal from a digital NTSC signal, based on a data operation between pixels in which the phase of the chrominance signal is inverted. A vertical comb filter for separating a luminance signal and a vertical component of a chrominance signal from the NTSC signal; and a luminance signal and a chrominance signal from the NTSC signal based on a data operation between pixels in which the phase of the chrominance signal is inverted. A horizontal comb filter for separating the horizontal component of
A BPF / Y / C separation unit for extracting a color signal from the NTSC signal by the PF and subtracting the color signal from the NTSC signal to obtain a luminance signal; and pixel data of a target pixel and peripheral pixels having the same phase of the color signal. The vertical and horizontal correlations of the pixel of interest are detected based on the correlation value, and the correlation detection
A determining unit, when the correlation detecting / determining unit determines that there is a correlation, outputs the luminance signal and the color signal by combining the outputs of the vertical comb filter and the horizontal comb filter according to the detection value; When it is determined that there is no correlation, a data synthesis / selection unit that outputs a luminance signal and a color signal obtained by the BPF / Y / C separation unit is provided.

The vertical comb filter separates the luminance signal and the vertical component of the chrominance signal from the NTSC signal based on the data operation between the pixels in which the phase of the chrominance signal is inverted. The horizontal component of the luminance signal and the horizontal component of the chrominance signal are separated from the NTSC signal based on the data operation between the pixels whose phases are in an inverting relationship.
In F, a color signal is extracted from the NTSC signal, and the color signal is subtracted from the NTSC signal to obtain a luminance signal.
The correlation detection / determination unit detects the vertical and horizontal correlation of the target pixel based on the pixel data of the target pixel and peripheral pixels having the same phase of the color signal, and based on the detected value, The data combining / selecting unit determines presence / absence, and when the correlation detecting / determining unit determines that there is correlation, combines the outputs of the vertical comb filter and the horizontal comb filter according to the detection value (correlation). A luminance signal and a color signal are output, and when it is determined that there is no correlation, the luminance signal and the color signal obtained by the BPF / Y / C separation unit are output.

In order to simplify the structure of the vertical comb filter and the horizontal comb filter, the vertical comb filter is used to reduce the pixel data of the target pixel and the peripheral pixel located above and below the adjacent scanning line in the same field. Based on the sum and the difference, the vertical components of the luminance signal and the chrominance signal are separated from the digital NTSC signal, and the horizontal comb filter forms the sum of the pixel data of the target pixel and the peripheral pixels located on the same scanning line in the same field. Digital NTSC based on
It is configured to separate the horizontal components of the luminance signal and the chrominance signal from the signal.

In order to simplify the structure of the correlation detection / judgment unit, the correlation detection / judgment unit determines whether the pixel of interest and the peripheral pixel located on two or three adjacent scanning lines in the same field are located. The vertical and horizontal correlations are detected based on the pixel data, and the presence or absence of the correlation is determined based on the detected values.

In order to further simplify the configuration of the correlation detection / judgment unit, the correlation detection / judgment unit detects the signal level difference between the target pixel and the surrounding pixels, and based on the detected value, determines the level of the target pixel. The signal level difference in the vertical and horizontal directions is calculated, and the calculated value is compared with a reference value to determine the presence or absence of correlation.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. In FIG. 1, reference numeral 10 denotes an input terminal of a digital NTSC signal.
Is connected to a data delay unit 12, and the data delay unit 12
, The vertical comb filter 14, the horizontal comb filter 16, the BPF / Y / C separation unit 18, the correlation detection
Each of the judging sections 20 is connected, and a data synthesizing / selecting section 22 is connected to an output side of the judging section 20, and a separated luminance signal (hereinafter referred to as a Y signal) and a color signal ( Output terminals 24 and 26 for outputting a C signal are connected.

The data delay section 12 is connected to the input terminal 1
The NTSC signal input to 0 is delayed by a predetermined scanning line (for example, one or two scanning lines) to generate and output pixel data of a target pixel and peripheral pixels required for data processing in a subsequent stage. I have. This pixel of interest represents a pixel of current interest in the current field, and peripheral pixels represent pixels located around the pixel of interest. Specifically, as shown in FIG. 2, when the target pixel X is on the lower scanning line of two adjacent scanning lines in the current field, the pixel a directly above the upper scanning line, The pixel A, the pixel B on the upper right and the pixel b on the left on the lower scanning line are peripheral pixels.
The peripheral pixels A and B and the target pixel X are a C signal (color signal).
Have the same phase relationship, and the peripheral pixels a and b and the pixel of interest X have the C signal phase inverted from each other (reverse phase relationship).
It is in.

The vertical comb filter 14 outputs vertical components Yv and Cv of the Y signal and the C signal based on the sum and difference between the pixel data of the target pixel X and the pixel data of the peripheral pixel a output from the data delay unit 12. It is configured to be. The horizontal comb filter 16 outputs the horizontal components Yh and Ch of the Y signal and the C signal based on the sum and difference between the pixel data of the target pixel X and the pixel data of the peripheral pixel b output from the data delay unit 12. It is configured. The BPF / Y / C separation unit 18 extracts a C signal from the NTSC signal and outputs a BPF (band-pass filter).
An arithmetic unit (for example, a subtractor) for obtaining a Y signal by subtracting from the C signal is mainly configured.

The correlation detection / determination section 20 detects the level differences Ε (X, A) and Ε (X, B) between the target pixel X and the NTSC signals (composite video signals) of the peripheral pixels A and B, and Based on the detected value, the vertical and horizontal level differences Ε (V) and Ε (H) of the target pixel X are calculated, and the absolute values of the level differences Ε (V) and Ε (H) are calculated as a reference value Ε ( R
EF) (> 0), and | Ε (V) | <Ε (RE
F), if at least one of the conditions of | Ｈ (H) | <Ε (REF) is satisfied, it is determined that there is a correlation; otherwise, it is determined that there is no correlation. These Ε (V) and Ε (H) are calculated based on the following equations (1) and (2). Ε (V) = Ε (X, A) + Ε (X, B) (1) Ε (H) = Ε (X, A) −Ε (X, B) (2)

The data synthesizing / selecting unit 22 determines the following (A) based on the judgment of the correlation detecting / judging unit 20:
It is configured to have the function described in (b). (A) When the judgment has a correlation, | Ε (V) | <Ε (R
EF) and | Ε (H) | <Ε (REF), and when it is determined that there is a correlation, the data combining / selecting unit 22 outputs the output Yv of the vertical comb filter 14. , Cv and the outputs Yh, C of the horizontal comb filter 16
h are synthesized according to the level differences Ε (V) and Ε (H), and a Y signal and a C signal that satisfy the following equations (3) and (4) are output. Y = (1−α) Yv + αYh (3) C = (1−α) Cv + αCh (4) α and (1−α) in the above equations (3) and (4) are expressed by the following equation (5)
Represents the ratio between the absolute values of the level differences Ε (V) and Ε (H). | Ε (V) | / | Ε (H) | = α / (1−α) (5) (2) If the judgment is that there is no correlation, | Ε (V) | <Ε (R
EF) and | Ε (H) | <Ε (REF) are not satisfied, and if it is determined that there is no correlation, data synthesis
The selection unit 22 outputs the Y output from the BPF / Y / C separation unit 18.
The signal and the C signal are output to output terminals 24 and 26.

Next, the operation of FIG. 1 will be described with reference to FIG. The data delay unit 12 delays the digital NTSC signal input to the input terminal 10 by a predetermined scanning line, and as shown in FIG. 2, the target pixel X and the peripheral pixels A and B on adjacent scanning lines in the same field. , A and b are created and output.

The vertical comb filter 14 generates a vertical component Yv of the Y signal and the C signal based on a sum and a difference between the pixel data of the target pixel X and the pixel data of the peripheral pixel a output from the data delay unit 12.
Cv, and the horizontal comb filter 16 outputs a horizontal component Y of the Y signal and the C signal based on the sum and difference of the pixel data of the target pixel X and the pixel data of the peripheral pixel b output from the data delay unit 12.
h and Ch, and the BPF / Y / C separation unit 18
A C signal is extracted from the SC signal and output, and the extracted C signal is subtracted from the NTSC signal to output a Y signal.

The correlation detection / determination unit 20 determines the level difference Ε (X, A), Ε (X, B) between the target pixel X and the peripheral pixels A and B.
Is detected, and the target pixel X is calculated using the above equations (1) and (2).
レ ベ ル (V) and Ε (H) are calculated, and the absolute values of the level differences 絶 対 (V) and Ε (H) are calculated as reference values Ε (REF) (> 0). Compare |
(V) | <Ε (REF), | Ε (H) | <Ε (REF)
If at least one of the conditions is satisfied, it is determined that there is correlation, and if not, it is determined that there is no correlation.

If it is determined that there is a correlation, the data synthesizing / selecting section 22 outputs the output Y of the vertical comb filter 14.
V, Cv and the outputs Yh, Ch of the horizontal comb filter 16 are synthesized according to the level differences Ε (V), Ε (H), and the Y and C signals satisfying the equations (3) and (4) Is output. Y = (1−α) Yv + αYh (3) C = (1−α) Cv + αCh (4)

In the equations (3) and (4), the ratio between (1-α) and α is, as expressed by the equation (5), the vertical
Absolute value of horizontal signal level difference | Ε (V) |, | Ε
(H) | represents the reciprocal of the ratio, and | Ε (V) |, | Ε
(H) | indicates that the correlation becomes higher as the value becomes smaller. Therefore, the Y signal and the C signal in Expressions (3) and (4) become higher as the correlation in the vertical direction becomes higher (that is, | Ε (V) | Becomes smaller), the proportion occupied by the vertical components Yv and Cv increases, and the higher the correlation in the horizontal direction (ie, the smaller | Ε (H) |), the more the horizontal components Yh and Ch become.
Occupies a larger proportion. Therefore, when there is a correlation and the vertical frequency component of the NTSC signal is high, the Y / C separation by the horizontal comb filter 16 is performed,
When the horizontal frequency component of the SC signal is high, Y / C separation by the vertical comb filter 14 is performed.

When it is determined that there is no correlation, the data synthesizing / selecting section 22 selects the Y signal and the C signal output from the BPF / Y / C separating section 18 and outputs them to the output terminals 24 and 26. . Therefore, when there is no correlation and both the vertical frequency component and the horizontal frequency component of the NTSC signal are high, the BPF / Y / C separation unit 18 performs Y / C separation.

In the above embodiment, the data delay section obtains pixel data of a target pixel and neighboring pixels located on two adjacent scanning lines in the same field, and the correlation detecting / determining section determines the target pixel. Based on the pixel data of the target pixel and the peripheral pixel, a signal level difference between the target pixel and the peripheral pixel is detected, and a vertical and horizontal signal level difference of the target pixel is calculated based on the detected value. Although the present invention is not limited to this, the present invention is not limited to this. The data delay unit obtains the pixel data of the target pixel and the peripheral pixels having the same phase of the color signal and obtains the correlation. The detection / determination unit detects a signal level difference between the target pixel and the peripheral pixel based on the pixel data of the target pixel and the peripheral pixel, and determines a vertical and horizontal signal level difference of the target pixel based on the detected value. Calculated, and can be utilized for those to determine the presence or absence of correlation by comparing the calculated value with a reference value.

For example, as shown in FIGS. 3 and 4, a data delay unit causes a target pixel X and neighboring pixels A, B, C, and C located on three adjacent scanning lines in the same field.
D pixel data is obtained, and the correlation detection / determination unit detects vertical and horizontal correlations based on the pixel data of the target pixel X and the peripheral pixels A, B, C, and D,
The present invention can also be applied to a case where the detection value is compared with a reference value to determine the presence or absence of the correlation.

That is, the level differences Ε (X, A), Ε (X, B), Ε (X) between the pixel of interest X and the surrounding pixels A, B, C, D having the same phase relationship of the C signal (color signal). X, C), Ε
(X, D) is detected, and based on the following equations (1a) and (2a), the level difference Ε between the vertical direction and the horizontal direction of the target pixel X is obtained.
(V) and (H) are calculated, and the level difference Ε
(V), the absolute value of 絶 対 (H) is used as the reference value Ε (REF) (>
0), | Ε (V) | <Ε (REF), | Ε
If at least one of the conditions of (H) | <ＲＥ (REF) is satisfied, it is determined that there is a correlation, and if not, it is determined that there is no correlation. Ε (V) = Ε (X, A) + Ε (X, B) + Ε (X, C) (1a) Ε (H) = Ε (X, B) −Ε (X, C) + Ε (X, D ) ... (2a)

If it is determined that there is a correlation, the data synthesizing / selecting section 22 outputs the output Y of the vertical comb filter 14.
V, Cv and the outputs Yh, Ch of the horizontal comb filter 16 are synthesized according to the level differences Ε (V), Ε (H), and the Y and C signals satisfying the equations (3) and (4) Is output. Y = (1−α) Yv + αYh (3) C = (1−α) Cv + αCh (4)

As is apparent from the equations (1a) and (2a) and the conditions for determining the presence or absence of correlation, the absolute value of the vertical signal level difference | Ε (V) | and the absolute value of the horizontal signal level difference | Ε (H) | indicates that the smaller the value is, the higher the correlation is. Therefore, considering equation (5), equation (3)
In the Y signal and the C signal of (4), the proportion of the vertical components Yv and Cv increases as the correlation in the vertical direction increases, and the proportion of the horizontal components Yh and Ch increases as the correlation in the horizontal direction increases. . Therefore, there is a correlation and NTS
When the vertical frequency component of the C signal is high, Y / C separation is performed by the horizontal comb filter 16. When the horizontal frequency component of the NTSC signal is high, the vertical comb filter 1 is used.
4, Y / C separation is performed.

When it is determined that there is no correlation, the data synthesizing / selecting section 22 selects the Y signal and the C signal output from the BPF / Y / C separating section 18 and outputs them to the output terminals 24 and 26. . For this reason, when there is no correlation as in the case where the change in the luminance level of the video is large, and when both the vertical frequency component and the horizontal frequency component of the NTSC signal are high, the BPF
Y / C separation is performed by the Y / C separation unit 18.

In the above embodiment, the data delay section obtains the pixel data of the pixel of interest and the neighboring pixels located on two or three adjacent scanning lines in the same field, and the correlation detection / determination section determines these pixel data. A signal level difference between the target pixel and the peripheral pixel is detected based on pixel data of the pixel and the peripheral pixel, and a vertical and horizontal signal level difference of the target pixel is calculated based on the detected value. Although the presence or absence of the correlation is determined by comparing with the value, the present invention is not limited to this, and the phase of the color signal is the same as that of the target pixel and the peripheral pixel. What is necessary is to detect the horizontal correlation and determine the presence or absence of the correlation based on the detected value.

In the above-described embodiment, the vertical comb filter has a color signal phase inverting relation and a sum of pixel data of a pixel of interest and peripheral pixels located above and below an adjacent scanning line in the same field. Based on the difference, the vertical components of the luminance signal and the chrominance signal are separated from the NTSC signal, and the horizontal comb filter has a phase inversion of the chrominance signal and a pixel of interest located on the same scanning line in the same field. Based on the sum and difference of pixel data of peripheral pixels, NTS
Although the horizontal and vertical components of the luminance signal and the chrominance signal are separated from the C signal, the present invention is not limited to this. The horizontal comb filter separates the luminance signal and the vertical component of the chrominance signal from the NTSC signal based on the NTSC signal. What is necessary is just to separate the horizontal component of the color signal.

[0029]

The present invention comprises a vertical comb filter, a horizontal comb filter, a BPF / Y / C separation unit, a correlation detection / judgment unit, and a data synthesis / selection unit. The vertical and horizontal correlations of the target pixel are detected, and the presence / absence of the correlation is determined based on the detected value. When there is correlation, the vertical comb filter and the horizontal comb filter are determined by the data synthesis / selection unit. Are output according to the detected value (correlation) to output a luminance signal and a color signal. When there is no correlation, the luminance signal and the color signal obtained by the BPF / Y / C separation unit are output. With this configuration, it is possible to separate the optimal luminance signal and color signal according to the correlation between the target pixel and the peripheral pixels from the NTSC signal.

That is, when there is a correlation between the target pixel and peripheral pixels and the vertical frequency component of the NTSC signal is high,
Y / C separation by horizontal comb filter is performed, and NTS
When the horizontal frequency component of the C signal is high, Y / C separation by the vertical comb filter is performed. When there is no correlation between the target pixel and the peripheral pixels, Y / C separation by the BPF / Y / C separation unit is performed.
Since the / C separation is performed, it is possible to separate the optimal luminance signal and color signal according to the correlation between the target pixel and the peripheral pixels from the NTSC signal.

A vertical comb filter performs digital NTS based on the sum and difference of pixel data of a target pixel and a peripheral pixel located above and below an adjacent scanning line in the same field.
A vertical comb filter separates the vertical components of the luminance signal and the chrominance signal from the C signal, and a horizontal comb filter performs digital NTSC based on the sum and difference of pixel data of a target pixel and peripheral pixels located on the same scanning line in the same field. In the case where the horizontal components of the luminance signal and the chrominance signal are separated from the signal, the configuration of the vertical comb filter and the horizontal comb filter can be simplified.

A correlation detection / determination unit detects vertical and horizontal correlations based on pixel data of a target pixel and neighboring pixels located on two or three adjacent scanning lines in the same field. In addition, when configured to determine the presence or absence of correlation by comparing this detection value with the reference value,
The configuration of the correlation detection / judgment unit can be simplified.

A correlation detection / judgment unit detects a signal level difference between the target pixel and peripheral pixels, calculates a vertical and horizontal signal level difference of the target pixel based on the detected value, and uses the calculated value as a reference. When the configuration is such that the presence or absence of the correlation is determined by comparing with the value, the configuration of the correlation detection / determination unit can be further simplified.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a digital Y / C separation circuit according to the present invention.

FIG. 2 is an explanatory diagram showing a case where a target pixel and a peripheral pixel are present on two adjacent scanning lines in the same field in order to explain the operation of FIG. 1;

FIG. 3 is an explanatory diagram showing a case where a target pixel and a peripheral pixel are present on three adjacent scanning lines in the same field in order to explain an operation of another embodiment of the present invention.

FIG. 4 is an explanatory diagram showing a signal level difference between a target pixel and peripheral pixels in which the phase of a C signal (color signal) has an in-phase relationship in FIG. 3;

[Description of Signs] 10: input terminal, 12: data delay unit, 14: vertical comb filter, 16: horizontal comb filter, 18
... BPF / Y / C separation unit, 20 ... Correlation detection / judgment unit, 22 ... Data synthesis / selection unit, 24, 26 ... Output terminals, A, B, C, D ... Peripheral pixels having an in-phase relationship, a, b... Peripheral pixels in which the phase of the target pixel X and the color signal have an inversion relationship (reverse phase relationship), B
PF: band pass filter, C signal: color signal, NT
SC signal: NTSC composite color television signal (composite video signal), X: target pixel, Y signal: luminance signal, Ε (H): horizontal signal level difference of target pixel X (value indicating horizontal correlation) ), Ε (V)... Vertical signal level difference (value indicating vertical correlation) of target pixel X, Ε (X, A), Ε (X, B), Ε (X,
C), Ε (X, D) ... target pixel X and peripheral pixels A, B,
Signal level difference between C and D pixels.

Claims (5)

[Claims] 1. A digital Y / C separation circuit for separating a luminance signal and a chrominance signal from a digital NTSC signal,
A vertical comb filter for separating a vertical component of a luminance signal and a color signal from the NTSC signal based on a data operation between pixels whose color signals have an inversion relationship; Based on the data operation of
A horizontal comb filter for separating a horizontal component of a luminance signal and a color signal from a TSC signal; and extracting a color signal from the NTSC signal with a BPF and extracting the color signal from the NTSC signal.
A BPF / Y / C separation unit that obtains a luminance signal by subtracting the luminance signal from a signal, and detects vertical and horizontal correlation of the target pixel based on pixel data of a target pixel and peripheral pixels having the same phase of a color signal; A correlation detection / judgment unit for judging the presence or absence of a correlation based on the detected value; and an output of the vertical comb filter and the horizontal comb filter when the correlation detection / judgment unit judges that there is a correlation. Are combined according to the detection value to output a luminance signal and a color signal, and when it is determined that there is no correlation, the data synthesis / output unit outputs the luminance signal and the color signal obtained by the BPF / Y / C separation unit. A digital Y / C separation circuit, comprising: a selection unit. 2. A vertical comb filter according to claim 1, wherein the phases of the color signals are in an inverting relationship, and the vertical comb filter is based on the sum and difference between pixel data of a pixel of interest and pixel data located above and below an adjacent scanning line in the same field. , The vertical components of the luminance signal and the chrominance signal are separated from the NTSC signal.
The horizontal components of the luminance signal and the color signal are converted from the NTSC signal based on the sum and difference of the pixel data of the target pixel and the peripheral pixel located on the same scanning line in the same field while the phases of the color signals are in an inversion relationship. 2. The digital Y / C separation circuit according to claim 1, wherein the separation is performed. 3. A correlation detection / judgment unit calculates a vertical and horizontal correlation of a pixel of interest based on pixel data of a pixel of interest and neighboring pixels located on two adjacent scanning lines in the same field. 3. The digital Y / C separation circuit according to claim 1, wherein the digital Y / C separation circuit detects the correlation and determines the presence or absence of the correlation based on the detected value. 4. A correlation detection / judgment unit detects a vertical and horizontal correlation of a target pixel based on pixel data of a target pixel and neighboring pixels located on three adjacent scanning lines in the same field. 3. The digital Y / C separation circuit according to claim 1, wherein the digital Y / C separation circuit detects the correlation and determines the presence or absence of the correlation based on the detected value. 5. A correlation detection / judgment unit detects a signal level difference between a target pixel and a peripheral pixel, and calculates a vertical and horizontal signal level difference of the target pixel based on the detected value. 5. The digital Y / C separation circuit according to claim 1, wherein the presence / absence of correlation is determined by comparing the digital Y / C with a reference value.