JPH0744696B2 - Video signal processing circuit - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to digital signal processing of video signals of TVs, VTRs and the like, and more particularly, to motion signals when performing three-dimensional signal processing using a frame memory or the like. The present invention relates to a motion detection circuit for detecting.

[Conventional technology]

Conventionally, a circuit as shown in FIG. 2 has been used as a circuit for detecting this kind of motion signal. Hereinafter, the conventional technique will be described with reference to FIG.

The input signal 201 is an NTSC video signal in which a luminance signal and a chrominance signal are mixed in an interleaved relationship, and is digitized by an A / D converter.

The frame memory 202 is a memory that delays the input signal by one frame.

By the subtracter 203, the difference between both ends of the frame memory,
That is, the frame difference signal is detected.

The output signal output from the subtractor 203 is as follows.

Input signal - frame delayed signal _{= (Y 1 + C 1)} - (Y 2 -C 2) = (Y 1 -Y 2) + (C 1 + C 2) = ΔY + (C 1 + C 2) The ΔY signal is a frame difference signal of the target luminance signal, and nothing is output in a completely stationary image.

On the other hand, C ₁ + C ₂ is a color signal, which is always output even in a completely stationary image.

Therefore, in order to extract only the ΔY signal which is the target frame luminance difference signal, the LPF 204 is used to extract the output signal 205.

[Problems to be Solved by the Invention]

In the conventional motion detecting circuit described above, the ΔY signal and the color signal are separated only by the LPF, so it is impossible to completely separate these two types of signals.

This is because when the hue changes significantly or when a color signal with a fast rise (a color signal created by computer graphics) is input, the waveform band with a peak at 3.58MHz widens and spreads to lower frequencies. Come on. On the other hand, the frame luminance difference signal ΔY signal, which is a luminance motion signal, is
It is not output for still images. However, in moving images, the band of this signal is widened, and may extend to near 3MHz.

Therefore, to extract only this spread ΔY signal, the LPF
It is difficult to completely remove the color signal with the wide band by using only the color signal. For example, in FIG. 3, the ΔY signal
301 and color signal 302 overlap, and this is LPF.
The band characteristic 303 cannot be extracted.

As a result, when the color signal is strong, the band is widened, and there is a drawback that an erroneous motion signal is detected despite the still image.

[Means for Solving the Problems]

The video signal processing circuit of the present invention includes a frame memory that delays an input signal by one frame, a subtracter that detects a difference between the input signal and both ends of the frame memory, and a motion signal and a color of the frame difference detected by the subtractor. A plurality of LPFs for removing a color signal from a signal and a plurality of coefficient units capable of externally controlling each output of the plurality of LPFs, an adder for adding the outputs of the coefficient units, and a color component only from the input signal It has a line-to-line YC separation circuit for extracting the signal, an absolute value circuit for obtaining the absolute value of this output, and a coefficient generation circuit for controlling the coefficient of the coefficient unit from this output.

As described above, the present invention includes a circuit that adaptively changes the band of the LPF according to the situation of the color signal in order to detect the ΔY signal, so that the ΔY signal can be completely removed without being disturbed by the color signal. It can be separated and output.

〔Example〕

 FIG. 1 is a block diagram of an embodiment of the present invention.

The input signal 101 is an NTSC video signal in which a luminance signal and a chrominance signal are mixed in an interleaved relationship, and is digitized by an A / D converter. The frame memory 102 is a memory that delays the input signal by one frame. Subtractor 10
Reference numeral 3 is a circuit for detecting a difference between both ends of the frame memory 102, that is, a frame difference signal.

LPF104, LPF105, and LPF106 are filters having the same band or a band narrower than that of the LPF connected in front. Coefficient multiplier 107,108,1
09 designates the output of the LPF (104, 105, 106) as a coefficient generation circuit 11
It is a circuit that controls the gain with the output of 3.

The adder 110 is a circuit that adds the outputs from the coefficient units 107, 108, and 109, thereby obtaining an output signal 114 that is a motion signal of luminance between frames.

The inter-line YC separation circuit 111 separates the color signal from the video signal of the input signal 101 by the inter-line fusi type filter. The absolute value circuit 112 is a circuit for converting the color signal separated by the line-to-line YC separation circuit 111 into an absolute value, and the output is a coefficient generator 107 for controlling the gain of the output of the LPF by a coefficient generation circuit 113. Controls a coefficient of ~ 109.

The operation of this circuit will be described with reference to FIG. 4. The difference signal at both ends of one frame delay is output by the subtractor 103, so that the subtractor 103 outputs twice the ΔY signal which is the frame difference luminance signal. Color signals (additional color signals of the current frame and one frame later) are output. The color signal is removed from this by the LPF and only the ΔY signal is taken out. At this time, three signals having different bands are taken out.

The first band has a band wider than fsc like 401.

(Note fsc means 3.58MHz) The second band has a band near 2MHz like 402.

The third band has a very narrow band of 1 MHz like 403.

The coefficient unit 107 controls the gain of the first band, and the coefficient unit 108 sets the gain of the second band to the coefficient unit 1
09 controls the gain in the third band. The control data of these coefficient units is determined by the amplitude of the color signal.

The color signal is separated by the line-to-line YC separation circuit 111, and the color signal is converted into an absolute value to be converted into a direct current. Therefore, an LPF may be added after this absolute value circuit 112. The magnitude of the output controls the gain of the coefficient unit. For example, when there is no color signal, the LPF band is widened to 401. That is, the gain of the coefficient unit 107 is set to “1”, and the gains of the coefficient units 108 and 109 are set to “0”. Conversely, when the color signal is strong, the LPF band is set to 403
, So that color signals are not mixed in. That is, the gains of the coefficient units 107 and 108 are set to “0”, and the gain of the coefficient unit 109 is set to “1”. The values of these coefficient units are adaptively switched depending on the size of the color signal. In this way, it is possible to detect a complete motion signal without malfunction due to color signals.

FIG. 5 is a block diagram of another embodiment of the present invention. The basic circuit configuration is the same as in FIG. 1, but the configuration of LPFs 504-506 is changed from cascade connection to parallel connection.

〔The invention's effect〕

As described above, according to the present invention, the level of the color signal is detected, and thereby the band of the LPF for extracting the luminance difference signal from the one frame difference signal is changed. As a result, a fast-moving motion signal can be accurately extracted when there is no color signal, and the color signal can be completely removed by narrowing the LPF band when the color signal is strong.

As a result, the motion detection using only one frame memory cannot completely detect a motion signal, and the one that had to use two frame memories can be configured with only one frame memory, which is a great effect. is there.

[Brief description of drawings]

FIG. 1 is a block diagram of a motion detecting circuit of the present invention, FIG. 2 is a block diagram of a conventional motion detecting circuit, and FIG. 3 is a conventional LPF.
FIG. 4 is a band characteristic diagram, FIG. 4 is a LPF band characteristic diagram of the present invention, and FIG. 5 is a block diagram of another embodiment of the present invention.

Claims (1)

[Claims] 1. A frame memory for delaying an input signal by one frame, a subtractor for detecting a difference between both ends of the input signal and the frame memory, and a motion signal and a color signal of the frame difference detected by the subtractor, A plurality of low-pass filters for detecting color signals, a plurality of coefficient units capable of externally controlling respective outputs of these low-pass filters, and a circuit for outputting a frame difference motion signal by an adder for adding the outputs of the coefficient units An inter-line YC separation circuit for extracting only color components from the input signal, an absolute value circuit, and a coefficient generation circuit for controlling the coefficients of the plurality of coefficient units by the output of the absolute value circuit. A video signal processing circuit characterized by changing the band characteristic of a low-pass filter depending on the magnitude of a color signal component.