JPH039428Y2 - - Google Patents

Description

[Detailed Description of the Invention] Purpose of the Invention Industrial Application Field The present invention relates to a television signal Y/C separation circuit that separates a luminance signal and a chrominance signal by utilizing the correlation of television signals.

2. Description of the Related Art In standard television systems such as the NTSC system, luminance signals and chrominance signals are interleaved in frequency, so it is generally difficult to completely separate the two on the receiving side. If the separation of the luminance signal and color signal (hereinafter referred to as "Y/C separation") is insufficient, image quality will deteriorate, such as a decrease in the resolution of the luminance signal.

Therefore, in place of the conventional frequency separation method, a method has been proposed in which Y/C separation is performed by utilizing the correlation between video signals specific to standard television signals. That is, for both odd-numbered fields and even-numbered fields, if we pay attention to the phases of video signals of adjacent scanning lines within one field, the luminance signals are in phase with each other, and the color signals are in phase with each other. Furthermore, if attention is paid to the amplitudes of video signals of these adjacent scanning lines, there is generally a correlation with respect to both brightness and color. Therefore, if we take the sum of the video signals of these adjacent scanning lines, we get
The color signals are almost canceled out, and a luminance signal with approximately double the amplitude is obtained. Furthermore, by taking the difference between the video signals of adjacent scanning lines, the luminance signals are almost canceled out, and a color signal with approximately double the amplitude is obtained. Therefore, by extracting 1/2 of the above sum and difference, Y/C
Separation can be performed.

Also, between odd-numbered fields and between even-numbered fields belonging to adjacent frames, the luminance signals are in phase with each other, and the chrominance signals are in phase with each other. Furthermore, the amplitudes of video signals in these adjacent frames generally have a correlation. Therefore, when the image signals in these adjacent frames are summed, the color signals are almost canceled out, and a luminance signal with approximately double the amplitude is obtained. Furthermore, by taking the difference between the video signals in adjacent frames, the luminance signals are almost canceled out and a color signal with approximately double the amplitude is obtained. That is, by extracting 1/2 of the above sum and difference,
Y/C separation can be performed.

In this way, using the correlation of video signals, Y/C
There are two methods for performing separation: a method that uses correlation between scanning lines and a method that uses correlation between frames. Since both methods are based on the assumption that there is a correlation between scanning lines or frames, as the degree of correlation decreases, Y/C separation becomes insufficient and image quality deteriorates. The degree of correlation between scan lines is reduced when the scan lines are at vertical contours within the screen. On the other hand, the correlation between frames decreases as the intensity of screen movement increases. Therefore, the luminance signal and chrominance signal, which have been separated by Y/C using the correlation between scanning lines and the correlation between frames, are weighted and added. A motion-adaptive type that increases the weighting of the separated luminance signal and chrominance signal based on the correlation between the scanning lines when there is large screen movement. A Y/C separation scheme has been proposed.

Problems to be Solved by the Invention The conventional motion adaptive Y/C separation method described above is configured to detect screen motion based on the magnitude of the difference between luminance signals of adjacent frames.
For example, the patent application filed earlier by the applicant in 1982-
Please refer to the specification of No. 224398 "Television Signal Conversion System".

Therefore, in the conventional method, even if there is movement in the color signal, if there is no movement in the luminance signal, it is treated as if there is no movement. In such a case, there is a problem that the Y/C separation becomes insufficient and the color signal leaks into the luminance signal, causing dot interference and deteriorating the image quality.

Means for Solving the Constituent Problems of the Invention The present invention, which solves the problems of the prior art described above, determines that there is movement not only in the luminance signal but also in the color signal when there is a change between frames, and weights the signal. configured to perform control.

Hereinafter, the operation of the present invention will be explained in detail using examples.

Embodiment of the Invention FIG. 1 is a block diagram showing the configuration of a television signal conversion circuit equipped with a Y/C separation circuit according to an embodiment of the invention.

This television signal conversion circuit includes a sync separation circuit 10, an A/D conversion circuit 20, and a Y/C separation circuit 3.
0 and a signal processing circuit 40, and the other parts other than the Y/C separation circuit 30 have the same configuration as the television signal conversion circuit to which the "television signal conversion method" of the earlier application is applied. ing.

In the Y/C separation circuit 30, 31 is a first Y/C separator that uses correlation between scanning lines, 32 is a second Y/C separator that uses correlation between frames,
33 is a motion detection/control circuit, 34 is a switch, 3
5 is a coefficient addition circuit.

A synchronization separation circuit 10 separates a vertical synchronization signal V and a horizontal synchronization signal H from the composite video signal input to this television signal conversion circuit. The video signal separated from the synchronization signal is converted into a digital signal by the A/D conversion circuit 20 and then supplied to the Y/C separation circuit 30. A portion of the video signal supplied to the Y/C separation circuit 30 is supplied to the first Y/C separator 31. The first Y/C separator 31 includes a delay circuit that delays the supplied video signal by one horizontal scanning line, and an adder and a subtracter that add and subtract the scanning lines before and after the delay. Y/C separation is performed on the video signal based on the correlation between scanning lines.
The separated color signal CL and luminance signal YL are supplied to a switch 34 and a coefficient addition circuit 35, respectively.

On the other hand, the other part of the video signal is supplied to the frame memory 21 in the second Y/C separation circuit 32. This frame memory 21 stores one frame (two fields) of the supplied video signal.
functions as a delay means that provides a delay of . Therefore, when the input and output of the frame memory 21 are subtracted by the subtracter 22, a chrominance signal 2C having approximately double the amplitude of the interframe difference signal ΔY of the luminance signal is obtained. When this subtraction result is passed through a bandpass filter 23 whose center frequency matches the color subcarrier frequency of 3.5 MHz, a color signal CF based on interframe correlation is obtained. The color signal CF based on this interframe correlation is
The signal is supplied to the switch 34. At the same time, the above color signal
CF is subtracted from the video signal supplied to the subtracter 24, and the subtracter 24 outputs a luminance signal YF based on the interframe correlation. The luminance signal YF output from the subtracter 24 is supplied to a coefficient addition circuit 35.

In this way, the switch 34 receives the Y/C separated color signal CL based on the correlation between the scanning lines;
A color signal CF separated in Y/C based on the correlation between frames is supplied, and a luminance signal YL separated in Y/C based on the correlation between scanning lines is supplied to the coefficient adding circuit 35.
and a luminance signal YF separated by Y/C based on the correlation between frames.

In parallel with the above Y/C separation operation, the subtracter 22
Inter-frame difference signal of the luminance signal output from △
A color signal 2C having an amplitude approximately double that of Y is supplied to the motion detection/control circuit 33. On the other hand, in the adder 36, the input and output of the frame memory 21 are added, and an inter-frame difference signal ΔC of the luminance signal 2Y and the color signal with almost double amplitude is outputted and supplied to the motion detection/control circuit 33. be done. Motion detection/control circuit 3
3 detects the movement of the screen based on the above signals, issues a switching command SW to the switch 34, supplies a weighting coefficient K to the coefficient addition circuit 35, and instructs the signal processing circuit 40 to create an interpolation signal. A signal M is provided indicating the intensity of the movement required.

FIG. 2 is a block diagram showing an example of the configuration of the motion detection/control circuit 33.

The signal ΔY+2C supplied from the subtracter 22 in the Y/C separation circuit 32 is passed through a low-pass filter 4 that passes frequency components lower than the 3.58 MHz color subcarrier.
1, the color signal component is removed. The inter-frame difference ΔY of the luminance signal that has passed through the low-pass filter 41 is determined by the absolute value circuit 42 as a non-polar amplitude |
is converted to △Y｜, and the highest value detection circuit (NAM) 4
5. On the other hand, the signal 2Y+ΔC supplied from the adder 36 in the Y/C separation circuit 30 is
The luminance signal component is removed in a bandpass filter 43 that passes the frequency component of the 3.58 MHz color subcarrier. The inter-frame difference △C of the color signal that has passed through the band-pass filter 43 is converted into a non-polar amplitude |△C| in the absolute value circuit 44, and is further converted into a non-polar amplitude |△C| by a coefficient unit 46 to provide a coefficient for balancing with the luminance signal. After being multiplied by k, it is supplied to a maximum value detection circuit (NAM) 45.

The maximum value detection circuit 45 detects |△Y| and k|△C|
The larger one is selected, and the selected one is supplied to the comparison circuit 54. The comparison circuit 54 is supplied with |
△Y| or k|△C| is compared with the reference value REF1 set in the reference value setting circuit 50, and if the former is larger, a switching command is issued to the switch 34.
Emit SW. That is, when the absolute value |△Y| or k|△C| of the inter-frame difference signal is smaller than the reference REF1, the color signal CF separated by Y/C based on the inter-frame correlation is passed through the switch 34. The color signal CL is transmitted to the subsequent signal processing circuit 40, and in the opposite case, the color signal CL separated into Y/C based on the correlation between scanning lines is transmitted to the signal processing circuit 40 via the switch 34.

In parallel, the absolute value |△Y| of the inter-frame difference of the luminance signal is used as the weighting coefficient K during addition in the coefficient adding circuit 35.
5. The coefficient addition circuit 35 weights the Y/C separated luminance signal YL based on the correlation between scanning lines, in proportion to the magnitude of the signal K.

Further, the absolute value |△Y| of the inter-frame difference of the luminance signal output from the absolute value circuit 42 is determined by the three comparators 51 to 53 and the reference values REF2 to REF4.
is supplied to a motion detection circuit consisting of three reference value setting circuits 47 to 49, each of which has been set. The three reference values REF are REF2, REF3,
It is increased in the order of REF4. The motion detection circuit is
As shown in FIG. 3, motion degree signals M1 to M4 are obtained by quantizing the magnitude of |△Y| into four stages by a combination of binary outputs α, β, and γ of three comparators 51 to 53. is supplied to the signal processing circuit 40.

The signal processing circuit 40 is a motion detection/control circuit 33
According to the motion degree signal supplied from the camera, signal processing is performed to achieve optimal image quality. For details of the signal processing contents, please refer to the specification of the above-mentioned earlier application.

As described above, for color signals, unlike the luminance signals, coefficient addition is not performed, but the color signals CL and CF are simply switched, which perform Y/C separation based on the correlation between scanning lines and frames, depending on the presence or absence of movement. An example of simplifying the configuration has been explained. This is because color signals generally do not require as much precision as luminance signals in order to prevent image quality deterioration. However, in general, as in the case of the luminance signal, the two are added so as to satisfy the relationship C=K'・CL+(1-K')CF, and the coefficient K' is calculated according to the output of the maximum other detection circuit 45. may be configured to be variable. That is, the configuration illustrated in FIG. 2 is a configuration in which the coefficient K' is set to either 0 or 1 depending on whether the output of the maximum value detection circuit 45 exceeds a predetermined value (reference value REF1).
This corresponds to a special example of the above formula.

Effects of the invention As explained in detail above, the Y/C separation circuit of the invention can perform
Since it is configured to shift the weighting of coefficient addition from the correlation between scanning lines to the Y/C separated color signal,
In such a case, it is possible to effectively prevent deterioration in image quality due to dot interference that occurs in conventional circuits.

In addition, the existing frame memory in the second Y/C separator can be used as is as a delay means for detecting inter-frame changes in color signals.
The above effects can be achieved by adding a few circuit elements.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a television signal processing circuit including a Y/C separation circuit according to an embodiment of the present invention, and FIG. 2 shows a motion detection circuit in the Y/C separation circuit of FIG. A block diagram showing an example of the configuration,
FIG. 3 is a conceptual diagram for explaining the operation of FIG. 2. 30...Y/C separation circuits 30, 31...First Y/C separator that utilizes correlation between scanning lines, 32...
...Second Y/C separator that utilizes correlation between frames, 33...Motion detection/control circuit, 34...Switch, 35...Coefficient addition circuit, 41...Low pass filter, 42, 44 ... Absolute value circuit, 43 ... Bandpass filter, 45 ... Maximum value detection circuit, 46 ...
... Coefficient unit, 49 to 50 ... Reference value setting circuit, 5
1 to 54... Comparators.

Claims (1)

[Claims for Utility Model Registration] A first Y/C separator that performs Y/C separation based on the correlation between scanning lines of a television signal and outputs a separated first luminance signal and a second color signal. and a second Y/C separator that performs Y/C separation based on the correlation between frames of the television signal and outputs a separated second luminance signal and a second color signal; An absolute value circuit that generates the absolute value of the inter-frame difference regarding the luminance signal and the inter-frame difference regarding the chrominance signal, and outputs an amount proportional to the absolute value of the inter-frame difference regarding the generated luminance signal as the magnitude of movement regarding the luminance signal. and a motion detection means for outputting the larger of an amount proportional to the absolute value of the inter-frame difference regarding the luminance signal and an amount proportional to the absolute value of the inter-frame difference regarding the value color signal as the magnitude of movement regarding the color signal. a control circuit; and a control circuit that increases the weighting of the first and second luminance signals in the range from 0 to 1 as the motion increases in the luminance signals output from the motion detection and control circuit; Luminance signal addition means for adding and outputting luminance signals; and increasing the weighting of the first color signal over a range from 0 to 1 as the motion regarding the color signal output from the motion detection/control circuit increases. A Y/C separation circuit for a television signal, comprising color signal adding means for adding and outputting the first and second color signals while adding the first and second color signals.