JPH04119790A - Luminance signal chrominance signal separator - Google Patents

Abstract

PURPOSE:To eliminate a chrominance signal invaded in a luminance signal by providing a polarity conversion circuit which decides a phase of an output of a selection circuit depending on an output of a decision circuit, a phase of a 1st sum signal and a phase of a 1st difference signal and a subtractor which subtracts an output of the polarity conversion circuit from the 1st sum signal to the separator. CONSTITUTION:When an input sg6 to a polarity conversion circuit 23 is '1', the circuit 23 outputs a signal with a same polarity as that of an input sg3 and a signal outputted from a selection circuit 22. On the other hand, when the input sg6 to a polarity conversion circuit 23 is '0' and an input sg7 to the polarity conversion circuit 23 is '1' (when an output of a subtractor 17 is negative), the circuit 23 outputs a signal with a same polarity as that of the input sg3 and the signal outputted from the selection circuit 22. A subtractor 11 subtracts an output of a multiplier 24 from a signal Yh1 and outputs a signal as a high frequency component Yh2 of a final luminance signal. The signal Yh2 is given to a subtractor 13, in which the signal Yh2 is subtracted from a high frequency component of the luminance signal S11 and a chrominance signal is obtained and outputted from an output terminal 15. Moreover, the high frequency component Yh2 of the luminance signal is added to a low frequency component of the luminance signal outputted from an LPF 2 at an adder 12, the luminance signal is obtained and outputted from an output terminal 14.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an apparatus for separating a decoded video signal into a luminance signal and a chrominance signal.

BACKGROUND ART FIG. 4 is a block diagram of a conventional luminance signal/chrominance signal separation device, which includes one-line memories 402 and 403, a comb filter A
405, comb filter B4O6, bandpass filter 4
07, a correlation detection circuit 404, a selection circuit 408, and a bypass filter (HPF) 409.

When an NTSC signal is input from the input terminal 401 of the conventional luminance signal chrominance signal separation device configured as described above,
The signals are input to one line memories 402 and 403 one after another. Now, the input signal is S1, and the output of the IH memory 402 is S2. The output of IH memo IJ 403 is assumed to be 83. These pixel signals 31 S2. FIG. 6A shows the position of S3 on the screen and the phase of the color subcarrier. As shown in FIG. 0, the phase of the color subcarrier is inverted line by line.

The comb filter A405 ilKs Sl from S2 to output a signal C1 that includes the low frequency parts of the chrominance signal and the luminance signal, and the comb filter B subtracts 53 from S2 to include the low frequency parts of the chrominance signal and the luminance signal. The bandpass filter 407 outputs the signal C2, and the bandpass filter 407 outputs the signal C3 centered on the color subcarrier.

The correlation detection circuit 404 detects the correlation between the pixel S2 of interest and the neighboring pixels S1 and S3, and outputs a signal indicating an optimal filter to the selection circuit 408. Correlation detection and optimal filter selection are performed as follows, for example:
Compare the absolute values of the high-frequency components of Sl, S2, and S3, and if the magnitudes of S2 and 81 are close, S2 has a strong correlation with Sl,
The optimal filter is the comb filter A405, and if the sizes of S2 and 33 are close, S2 has a strong correlation with S3,
The optimal filter is the comb filter B4O6, and if the difference between S2 and Sl or S3 is greater than the dark value, then S2 is
There is no correlation with either l or 33, and the optimal filter is bandpass filter 407. In this way, the selection circuit 408 selects the optimum filter based on the output of the correlation detection circuit 404, the low frequency component is removed by the HPF 409, and a color signal is obtained from the output terminal 411. Further, this color signal is subtracted from the original signal S2 by a power reduction circuit 410, and a luminance signal is obtained from an output terminal 412.

For example, in this conventional luminance signal chrominance signal separation device, FIG.
When a signal like the one shown in Figure 1 is input, the signal switches between red and black at a certain line, so the association selects a comb filter that uses pixels with strong correlation to achieve separation without deterioration. I can do it. FIG. 6B shows the change in the signal at this boundary. In FIG. 6B, the signals on the L-1 line and the L line indicate a red color signal, and there is a boundary between the L line and the L+1 line, and since the L+1 line is black, there is no color signal.Here, When separating the L line signal, since the absolute values of the L line and L-1 line signals are equal, it is determined that the correlation between the L line and the L-1 line is strong. However, since the absolute values of the L line signal and the L+1 line signal are not equal, the L line and L'+
The correlation between the 1st line and the L- line was determined to be weak.
Y/C separation is performed using one line of signals.

Problem to be Solved by the Invention However, when the signal shown in FIG. 5B is input to the conventional luminance signal/chrominance signal separation device shown in FIG. 4 configured as described above, the boundary of this signal is a curved line. In the diagonal portion, the signal changes smoothly. Therefore, the signals at the boundary become as shown in (a), (b), and (c) of FIG. 3A, for example.

This figure shows a half-cycle signal of the color signal, and L-
The magnitude of the color signal gradually decreases from the first line. In the conventional luminance signal/chrominance signal separation device shown in FIG. 4, it is determined that there is no correlation between the pixel S2 of interest and the pixels above and below, and a bandpass filter is often used. However, if a bandpass filter is used in edge areas or areas where vertical correlation is weak, the high frequency part of the luminance signal will be lost and the image will become blurry.To prevent this, reducing the area in which bandpass filters are used will cause the image to become blurred. This has the problem that dot interference increases.

Means for Solving the Problems The present invention provides a first means for obtaining a first difference signal between one line or two lines of a decoded video signal, and a first summation signal between one line of the decoded video signal. a first adder for obtaining a signal, a second means for obtaining a second difference signal between one line of the output of the first adder, and the smaller of the first difference signal and the second difference signal. a selection circuit that selects a high frequency component of the decoded video signal, a determination circuit that determines whether the high frequency component of the decoded video signal is a luminance signal or a color signal, and a determination circuit that determines whether the high frequency component of the decoded video signal is a luminance signal or a color signal; Provided is a luminance signal/chrominance signal separation device having a polarity conversion circuit that determines the phase of the output of the selection circuit from the phase of the difference signal, and a subtracter that subtracts the output of the polarity conversion circuit from the first sum signal. It is something to do.

The effect selection circuit obtains a difference signal between lines, the polarity conversion circuit changes the polarity of this difference signal according to the characteristics of the image, and by subtracting it from the output of the comb filter, it is possible to suppress deterioration of image quality without reducing resolution. I can do it.

Embodiment FIG. 1 is a block diagram of a luminance signal color signal separation device according to a first embodiment of the present invention.

As shown in FIG. 1, a low pass filter (LPF) 2,
High-pass communication filter () (PF) 3, adders 4 and 12
, subtracters 11, 13, 17 and 19, l line memory (IH memory) 5 and 6, absolute value circuit (ABS) 1
6.18. Consists of 20 and 21, a selection circuit 22, a polarity conversion circuit 23. 1/2 adders 8 and 24, an exclusive OR circuit 7. a 1-bit IH memory 9, and an OR circuit 10. There is.

When an NTSC signal is input from the input terminal 1 of the luminance signal and color signal separation device configured as above, the HPF 3 extracts a high frequency signal including the high frequency portion of the color signal and the luminance signal, and the LPF 2 extracts the luminance signal. The low frequency part of is extracted. On the other hand, the output of HPF 3 is input to IH memory 5, where H
The output of PF3 is set to Sll, and the output of IH memory 5 is set to 51.
Set it to 2.

Sll and 312 are added by the adder 4 and then input to the 1/2 multiplier 8. The adder 4 and the multiplier 8 constitute a comb-shaped filter, and the output is the high-frequency portion of the luminance signal (
Yhl).

Now, Sll and S12 are input to absolute value circuits 16 and 18, respectively, and a subtracter 17 subtracts the output of ABSlB from the output of ABS16. Furthermore, this subtractor 1
The output of 7 is input to the absolute value circuit 21 and further input to the selection circuit 22.

Furthermore, Sll and S12 are input to an adder 4, and the output of the adder 4 is input to an IH memory 6. The output signal is subtracted from the input signal of the IH memory 6 in the subtracter 19 and input to the absolute value circuit 20.

The output of the absolute value circuit 20 is input to the selection circuit 22.The 0 selection circuit 22 selects and outputs the smaller of the absolute value circuits 20 and 21.The output of the 0 selection circuit 22 is input to the polarity conversion circuit 23. be done. Here, polarity conversion circuit 2
3 has three other input signals. It is subtractor 1
7) (sg7), the most significant bit (sg6) of the output of the OR circuit 10, and the most significant bit (sg3) of Yhl, where sg5 is obtained as follows.

The most significant bit (sign bit) sgl of 311 and the most significant bit (sign bit) sg2 of 512 are exclusive OR circuit 7
is input. sg which is the exclusive OR of sgl and sg2
4 is input to the 1-bit IH memory 9 and delayed by 1 line. And its output is eline delayed sg5
and the above sg4 are input to the OR circuit 10, and the logical sum of sg4 and sg5 is sg5.

The polarity conversion circuit 23 outputs the input signal from the selection circuit 22 with the same polarity as sg3 when sg6 is u1''.On the other hand, when sg6 is 0'' and sg7 is 1'' (the output of the subtracter 17 is negative) ) The input signal from the selection circuit 22 is output with the same polarity as sg3. sg6 is “0”
When sg7 is "0" (when the output of the subtracter 17 is positive), the polarity of the input signal from the selection circuit 22 is reversed to that of sg3 and output.

The output of the polarity conversion circuit 23 is halved by a 1/2 multiplier 24 and input to the subtracter 11. In the subtracter 11, Yhl
The output of the multiplier 24 is then subtracted and output as the high frequency portion Yh2 of the final luminance signal. This Yh2 is subtracted from the high frequency signal Sll by the subtracter 13 to obtain a color signal, and the output terminal 1
Output from 5. Also, the high frequency part Yh2 of the luminance signal is L
The adder 12 adds the low frequency portion of the luminance signal output from the PF 2 to obtain a luminance signal, which is output from the output terminal 14 .

The above operation will be explained using an example of the signal waveform shown in FIG. FIG. 3 shows the signals of three consecutive lines L-1, L and L+1 and the corresponding output Yh of the multiplier 8.
l, output A1 of the absolute value circuit 20, output A2 of the absolute value circuit 21, output A3 of the multiplier 24, and output Y of the subtracter 11
h2 is shown. In FIG. 3A, the signal on the L-1 line, the signal S12 on the L line, and the signal 31 on the L+1 line.
1 is the color signal shown in (a), (b), and (C), but there is no correlation between them. Yhl is the sum of Sll and 312 multiplied by 0.5 as shown in (d). Therefore, unnecessary color signals are mixed into the luminance signal. The output A1 of the absolute value circuit 20 is as shown in (e), and the output A2 of the absolute value circuit 21 is as shown in (f).The 0 selection circuit 22 selects and outputs the smaller input signal. A
I is output. Now, the input signal of the IH memory 5 in FIG. 1 is the L line signal S12, and the output of the IH memory 5 is the L line signal S12.
-1 line signal, since the polarities of these signals are different, the output sg4 of the exclusive OR circuit 7 becomes "1", and at the time one line later, the output sg5 of the 1-bit IH memory 9 becomes "1". "1", and the output of the OR circuit 10 also becomes "1". In this case, the polarity conversion circuit 23 makes the polarity of the output signal the same as sg3, so the output A3 of the multiplier 24 has the same polarity as Yhl, and A1 half the size (Yhl
The subtracter 11 subtracts A3 from Yhl to remove unnecessary components.

Next, an explanation will be given using another example of a signal waveform shown in FIG. 3B. In Figure 3B, as shown in (a), (b), and (c), the L-1 line and the L line have the same luminance signal, but the L+l line has no signal, so Yhl is S
The level is half of 12, which is an unnecessary luminance component. Al and A2 have the same size as shown in FIG. 3B (e) and (f), and this signal is output from the selection circuit 22. By the way, since the signals on these three lines are luminance signals, the output sg4 of the exclusive OR circuit 7 and the output sg5 of the 1-bit IH memory 9 are 0'', and L+1
Since the signal S12 on the L line is larger than the signal Sll on the line, the output of the subtracter 17 becomes negative, and sg7 becomes 1''.
becomes. Also, since Yhl is positive, sg3 is “O”.
Therefore, the polarity conversion circuit 23 changes the polarity of the input signal to sg.
Same as 3, make it positive and output. Then, the signal A3 becomes a signal shown in the figure, and the subtracter 11 subtracts A3 from Yhl to remove unnecessary luminance signals.

Further, the explanation will be made using another signal waveform example shown in FIG. 3C. In FIG. 3C, there are luminance signals on three lines as shown in (a), -) and (C), but there is no correlation.

Yhl becomes as shown by the mountain and is smaller than Sll. AI and A2 become as shown in (e) and (f), and the selection circuit 22 selects A1 in (e). 3-line signal Since is a luminance signal, sg6 becomes ゛°0pa.

At this time, since Si2 is smaller than Sll, sg7 is ``0''
0 par. Moreover, since Yhl is positive, sg3 becomes 0'°.

Therefore, the polarity conversion circuit 23 converts the input signal into a negative signal having a phase opposite to that of sg3 and outputs it.

Therefore, A3 becomes the signal shown in (6). Then, by subtracting A3 from Yhl in the subtracter 11, Yh2 becomes the same signal as Sll, as shown in (5).

In this way, unnecessary components mixed into the comb filter can be removed according to the luminance signal and color signal.

FIG. 2 shows a second luminance signal/chrominance signal separation device according to a second embodiment of the present invention. This luminance signal color signal separation device is PAL
This device is for signals, and the only difference from the luminance signal/chrominance signal separation device in FIG. 1 is that the IH memory 5 in FIG. 1 is replaced with a 2H memory 205 in FIG. In PAL signals, color signals are shifted by 90 degrees for each line. Therefore, the relationship between color signals separated by two lines is exactly the same as the relationship between color signals separated by one line in the NTSC signal. Therefore, IH in Figure 1
By changing the memory 5 to a 2H memory, the same operation for PAL signals as the device of FIG. 1 for NTSC signals can be obtained.

Effects of the Invention As described above, the present invention obtains the signal difference between lines, determines the sign of this signal according to each situation, and subtracts it from the output of the comb filter, thereby obtaining the high frequency part of the luminance signal. The color signal mixed into the luminance signal can be removed without deteriorating the luminance signal, which has a great practical effect.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of a luminance signal/color signal separation device according to a first embodiment of the present invention, FIG. 2 is a block diagram of a luminance signal/chrominance signal separation device according to a second embodiment of the present invention, and FIG. An explanatory diagram of the operation of a luminance signal color signal separation device, FIG. 4 is a configuration diagram of a conventional luminance signal color signal separation device, FIG. 5 is a screen diagram showing an example of a video signal for explanation, and FIG. 6 is an NTSC signal. FIG. 2...Low pass filter, 3...Bypass filter, 4.12...Adder, 5.6.
...IH memory, 9...1 bit IH
Memory, 16.1820.21...Absolute value circuit, 11.13.17゜19...Subtractor, 7...
...Exclusive OR circuit, 1o...OR circuit, 22...Selection circuit, 23.Old...Polarity conversion circuit, 8,24...Multiplier , 205・old・2H
memory. Name of agent: Patent attorney Haruaki Ogata, 2 people, 3rd grade A, +1 line (CJ r (9J A 3, 1st grade, 7-- (h) h2 (h) h2 Figure, scratch line)

Claims (6)

[Claims] (1) a first means for obtaining a first difference signal between one line of the decoded video signal; a first adder for obtaining a first sum signal between one line of the decoded video signal; second means for obtaining a second difference signal between one line of the output of the first adder;
a selection circuit that selects the smaller of the difference signal and the second difference signal; a determination circuit that determines whether the high frequency component of the decoded video signal is a luminance signal or a color signal; a polarity conversion circuit that determines the phase of the output of the selection circuit from the phase of the output and the first sum signal and the phase of the first difference signal; and a subtraction that subtracts the output of the polarity conversion circuit from the first sum signal. A luminance signal chrominance signal separation device having a device. (2) The luminance signal/chrominance signal separation device according to claim 1, wherein the first means obtains a difference signal between two lines of the decoded video signal. (3) The first means includes a first memory that delays the decoded video signal by one line, a first subtracter that obtains the difference between the absolute value of the input and output of the first memory, and a second The luminance signal and chrominance signal according to claim 1, wherein the means comprises a second memory for delaying the first sum signal by one line period, and a second subtracter for obtaining the difference between the input and output of this memory. Separation device. (4) The first means includes a third memory that delays the decoded video signal by two lines, a first subtracter that obtains the difference between the absolute values of the input and output of the third memory, and the second The luminance signal color according to claim 2, wherein the means comprises a fourth memory for delaying the first sum signal by one line period, and a second subtracter for obtaining the difference between the input and output of this memory. Signal separation device. (5) A selection circuit selects the smaller of the absolute value of the output of the first means and the absolute value of the output of the second means, and the determination circuit indicates the polarity of the high frequency signal of the decoded video signal. signal 1
a fifth memory that delays the line period; an exclusive OR circuit that calculates the exclusive OR of the input and output of the fifth memory; and a sixth memory that delays the output of the exclusive OR circuit by one line period. , Claim 1 comprises an OR circuit that calculates the OR of the input and output of this sixth memory.
The luminance signal color signal separation device according to item 1 or 2. (6) A polarity determination circuit makes the polarity of the input signal the same as the polarity of the output of the first adder when the determination circuit determines that the high frequency signal of the decoded video signal is a color signal; When the determination circuit determines that the high frequency signal of the decoded video signal is a luminance signal and the polarity of the first difference signal is negative, the polarity of the input signal is made the same as the polarity of the output of the first adder. , and when the determination circuit determines that the high-frequency signal of the decoded video signal is a luminance signal and the first difference signal is positive, the polarity of the input signal is changed to the polarity of the output of the first adder. A luminance signal/chrominance signal separation device according to claim 1 or 2, wherein the luminance signal and color signal are reversed.