JPH0417593B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an enhancer for color video signals.

Prior Art In general, images on televisions, VTRs, etc. contain many harmonics in the video signal in parts where the image changes in a pulse-like manner, such as when the image suddenly falls from white to black or from black to white. In order to faithfully amplify such signals, it is necessary to widen the bandwidth of the video amplification circuit, but on the other hand, video amplification circuits for color televisions have a narrow band due to trap circuits, etc., and their high-frequency characteristics are particularly poor. It is declining. Therefore, the rising and falling parts of the video signal become rounded, and the green outline of the image becomes blurred.
Resolution decreases. Also, when dubbing using a VTR, this tendency becomes noticeable, and the playback screen becomes noticeably unnatural. For this reason, an image compensation circuit is used which contours the edges of the image and improves the sharpness of the image.

FIG. 2 is a block diagram showing a typical prior art configuration, and FIG. 3 is a diagram showing waveforms of various parts in FIG. 2. The video signal applied to the video signal input terminal 10 is input to the buffer 11,
It is branched into two at the output terminal a of the buffer 11, and one is connected to the first delay circuit 12 via the line l12a.
and the other is input to the first via line l12b.
is input to one input terminal of the adder 15. The video signal input to the first delay circuit 12 is delayed by a time Δt and output to the connection point b between the first delay circuit 12 and the second delay circuit 13, where it is branched into three parts, one of which is It is input to the buffer 20 via line l13a. The other signal is input to the second delay circuit 13 via line l13b. Furthermore, the other one is connected to the differential amplifier 1 via the line l13c.
It is input to the positive input terminal of No.6. The Δt-delayed video signal inputted to the second delay circuit 13 is then further delayed by Δt, and as a 2Δt-delayed signal is sent to the first adder 15 via the buffer 14 and the line l15.
is input to the other input terminal of the first adder 15.
As a result, 1/2 addition with the signal inputted from the output terminal a of the buffer 11 via the line l12b is performed. This added signal is on line l1
6 to the negative input terminal of the differential amplifier 16, and the difference signal between the signal delayed by Δt and input from the connection point b to the positive input terminal via line l13c is output, and this difference signal is Batsuhua 1
7. The signal is inputted to one input terminal of the second adder 19 via the noise suppression circuit 18 and the line l19. This difference signal is delayed by 2Δt. A signal delayed by Δt branched from the connection point b is input to the other input terminal of the second adder 19 via the line l13a, the buffer 20, and the line l20. Second
The adder 19 performs an addition operation on the two signals delayed by Δt and delayed by 2Δt, and outputs this added signal to the input terminal f of the amplifier 21, which outputs it to the video signal output terminal 22. Ru.

With reference to FIG. 3, the waveforms of each part in FIG. 2 described above will be explained. FIG. 31 shows the waveform of the image signal at the output terminal a of the buffer 11 shown in FIG. 2 is a waveform at connection point b in FIG. 2, which is delayed by a time Δt because it has passed through the first delay circuit 12.
FIG. 3 shows the waveform at the input terminal c of the buffer 14, which passes through the second delay circuit 13, so the time 2Δt
Only late. FIG. 3 shows the waveform of the output terminal d of the adder 15, and calculation 2-4 using the waveforms 2 and 4 above.
is performed, and a differential voltage is output. Figure 3 5
is the waveform of the output terminal f of the second adder 19.
Calculation 2+5 is performed using the waveforms 2 and 5,
Pre-shoot PS and overshoot OS are added to the signal waveform. In this way, by forming an output waveform in which overshoot and preshoot are added to the rising and falling parts of the waveform, an image with enhanced contours is obtained.

Problems to be Solved by the Invention In such prior art, the means for obtaining the pre-shoot waveform and overshoot waveform that outline the image are constructed of analog circuits, so that stable and sufficient accuracy can be achieved. It is difficult to do so. The width Δt of each of the preshoot and overshoot waveforms determines the width of the outline of the image, and if the two delay time widths Δt are not equal, the outline will be unnatural, but the accuracy of this Δt depends on the delay circuit. Depends on accuracy. Furthermore, the level of the preshoot and overshoot waveforms determines the shading of the contour, and this level depends on the operation of the analog adder circuit. When the level of the pre-cut waveform used to emphasize the outline is deepened, it reaches the synchronization signal level, and the synchronization circuit misidentifies this pre-cut waveform as a synchronization signal, causing synchronization disturbance and making it impossible to obtain a stable screen. In addition, noise components included in the video signal are also emphasized by contour enhancement, resulting in a grainy screen.To avoid this, a noise suppression circuit is provided, but the noise suppression circuit is If it passes, the contour emphasis signal with a low amplitude level will also be cut out. When the means for contour enhancement is constructed from an analog circuit as described above, there is a problem that the desired effect cannot be obtained even though the circuit becomes complicated.

OBJECTIVES Therefore, an object of the present invention is to solve the above-mentioned technical problems and provide an enhancer for color video signals that digitally processes edge enhancement of degraded images using a digital circuit.

Means for Solving the Problems The present invention provides (a) color signal conversion means 2 to 4 for converting a color video signal into analog color signals of red R, green G, and blue B;
(b) Each color R, G, B from color signal conversion means 2 to 4
Each color R is converted into a digital signal with multiple pits corresponding to the level of shading of each analog color signal.
A/D converter 5R, 5G, 5B for each G and B
and (c) contour enhancement circuits 6R, 6G, and 6B that receive digital signals for each color R, G, and B from A/D converters 5R, 5G, and 5B, respectively;
(c1) Shift registers 7R, 7G, 7B that delay the phase of digital signals from A/D converters 5R, 5G, 5B for each color R, G, B
(c2) Compare the digital signals from A/D converters 5R, 5G, 5B for each color R, G, B with the signals from shift registers 7R, 7G, 7B, and select from dark to light images. (c3) Comparators 8R, 8G, and 8B detect switching from light to dark, no change in shading of the image, and switching from light to dark; , when switching from dark to light, shift registers 7R, 7G,
Preshoot and then overshoot are added to the signal from 7B, and when there is no change in image density, shift registers 7R, 7G, 7 are added.
Adders 9R, 9G, 9B add overshoot and then polish to the signals from shift registers 7R, 7G, 7B when the image changes from light to dark without changing the signal from B. (c4) This is a color video signal enhancer characterized by including D/A converters 10R, 10G, and 10B that convert each output from the adders 9R, 9G, and 9B into analog color signals.

Function According to the present invention, after converting a color video signal into analog color signals of red R, green G, and blue B by the color signal conversion means 2 to 4, the A/D converter 5
R, 5G, and 5B convert the analog color signal into a multi-bit digital signal corresponding to the shading level, and then the edge enhancement circuits 6R, 6G, and 6B provided for each color R, G, and B convert the analog color signal into a multi-bit digital signal corresponding to the density level. In the shift registers 7R, 7G, 7B, the phase of the digital signal is delayed, and the undelayed digital signal from the A/D converter is thus compared with the signal delayed by the shift registers 7R, 7G, 7B. Detects the switching of the light and shade of the image, digitally processes the signal necessary for enhancing the outline of the image, and then converts the D/A converter 10R, 1
Analog color signals can be obtained by 0G and 10B. This makes it possible to achieve highly accurate and stable operation.

Embodiment FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention. A video signal from a television, VTR, etc. is input to the separation circuit 2 via line l1, and is separated into a luminance signal (Y signal) and a chroma signal (C signal). The chroma signal is input to the chroma demodulation circuit 2 via line l2, demodulated into two color difference signals of RY and BY, and then input to the RGB matrix circuit 4 via lines l3a and l3b. The other input terminal of the RGB matrix circuit 4 receives the luminance (Y) signal separated from the separation circuit 2 on line l4.
The R-Y, B-Y color difference signals are converted to red R, green G, and blue B RGB analog signals, and the red R analog signal is sent to line 15R, and the green G analog signal is sent to line 15G. The blue B analog signals are individually input to A/D converters 5R, 5G, 5B via lines 15B and converted into digital signals, and then sent to lines 16R, 16G, 1.
6B to the respective input terminals of contour emphasizing circuits 6R, 6G, and 6B. The operation of the contour emphasizing circuit 6R for the red R signal will be explained below.

The red R digital signal input to the red R contour enhancement circuit 6R via the line l6R is composed of A _p to _{A o} bits, and this signal is branched into two.
One of the signals is input to the shift register 7R via line l8, and its phase is delayed by one clock. The configuration of this phase-delayed signal is assumed to be B _p to _{B o} bits. The other branched original signal of A _p to _{A o} bits is applied to one input terminal of the comparator 8R via line l7, and the aforementioned phase delay signal B _p to B is applied to the other input terminal of the comparator 8R. _o bits are added via line 19. The comparator 8R compares the original signal (real-time information amount) of A _p to _{A o} bits with the phase-delayed signal of B _p to _{B o} bits (the amount of information one clock before the real-time information amount of A _p to _{A o} bits). ), and (A _p ~ A _o )>
If (B _p ~ _{B o} ), the image switches from dark to light, and if (A _p ~ A _o ) = (B _p ~ B _o ), there is no change in the shading of the image (A _p ~ _{A o} ) < If (B _p ~ _{B o} ), it is determined that the image has switched from light to dark, and the light of the image →
When switching from dark to dark or from dark to light, corresponding switching signals are delivered to one terminal of the adder 9R via line l10. The other input terminal of the adder 9R receives the phase delay signal (B _p ~B _o ).
is input via line l11.

The adder 9R sets all bits (B _p to B _o ) constituting the phase delay signal to "H" when an image switching signal from light to dark or dark to light is added, and switches the image from light to dark. When a switching signal is added, overshoot and preshoot are added,
When a switching signal from dark to light is added, a preshoot and then an overshoot are added and output as an image signal to the input terminal of the D/A converter 10R via a line 112. When the shading of the image does not change, the signal from the shift register 7R is directly derived without changing. The D/A converter 10R thereby derives an edge-enhanced red R analog signal from the line l13 when the image changes from light to dark or from dark to light.

Although the above explanation of the operation deals with the red R signal, it is clear from the configuration shown in FIG. 1 that other green G and blue B signals are processed in the same way.

Effects As described above, according to the present invention, the video signals of each color of red R, green B, and blue B are digitized, and high-precision edge enhancement using the clock is achieved through digital processing. It is possible to reproduce a screen of good image quality with sufficient overshoot and preshoot sharpness without being affected by noise components contained in the image. In particular, in the present invention,
Analog color signals are digitized using A/D converters 5R, 5G, and 5B, and contour enhancement circuits 6R, 6G, and 6B for each color R, G, and B perform digital calculation processing, resulting in highly accurate results. Stable operation can be achieved. Moreover, the problem of synchronization disturbance caused by misrecognizing the preshoot waveform as a synchronization signal is solved by the operation of the comparators 8R, 8G, and 8B, and a stable image can be obtained. Such comparators 8R, 8G, 8
It is possible to obtain preshoot and overshoot waveforms that match the amount of change from dark to light or light to dark in the image due to B, and therefore, it is possible to obtain preshoot and overshoot waveforms that match the amount of change from dark to light or light to dark in the image. There are no obstacles in the present invention. Such a configuration of the present invention is simple, highly reliable, and can achieve the excellent effects of being able to reduce costs.

[Brief explanation of drawings]

Fig. 1 is a block diagram showing the configuration of an embodiment of the present invention, Fig. 2 is a block diagram showing the prior art, and Fig. 3 is a block diagram showing the configuration of an embodiment of the present invention.
The figure is a waveform diagram of the contour enhancement operation. 1... Color video signal enhancer, 2... Signal separation circuit, 3... Chroma demodulation circuit, 4...
RGB matrix circuit, 5R, 5G, 5B...
A/D converter, 6R, 6G, 6B...contour emphasis circuit, 7R, 7G, 7B...shift register,
8R, 8G, 8B...Converter, 9R, 9G,
9B... Adder, 10R, 10G, 10B...
D/A converter, 11, 14, 17, 20...
Buffer, 12, 13...delay circuit, 16...differential amplifier, 18...noise suppression circuit.

Claims (1)

[Claims] 1. (a) Color signal conversion means 2 for converting a color video signal into analog color signals of red R, green G, and blue B.
4, and (b) each color R, G, B from color signal conversion means 2 to 4;
Each color R is converted into a digital signal with multiple pits corresponding to the level of shading of each analog color signal.
A/D converter 5R, 5G, 5B for each G and B
and (c) contour enhancement circuits 6R, 6G, and 6B that receive digital signals for each color R, G, and B from A/D converters 5R, 5G, and 5B, respectively;
(c1) Shift registers 7R, 7G, 7B that delay the phase of digital signals from A/D converters 5R, 5G, 5B for each color R, G, B
(c2) Compare the digital signals from A/D converters 5R, 5G, 5B for each color R, G, B with the signals from shift registers 7R, 7G, 7B, and select from dark to light images. (c3) Comparators 8R, 8G, and 8B detect switching from light to dark, no change in shading of the image, and switching from light to dark; , when switching from dark to light, shift registers 7R, 7G,
Preshoot and then overshoot are added to the signal from 7B, and when there is no change in image density, shift registers 7R, 7G, and 7
Adders 9R, 9G, and 9B add overshoot and then police to the signals from shift registers 7R, 7G, and 7B when the image changes from light to dark without changing the signal from B. (c4) A color video signal enhancer comprising: D/A converters 10R, 10G, and 10B that convert each output from the adders 9R, 9G, and 9B into analog color signals.