JPH0691629B2 - Color video signal processing circuit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color video signal processing circuit, and more particularly to a color video signal processing circuit for reducing noise of a video signal such as VTR or television.

[Prior Art] FIG. 3 is a block diagram showing a color video signal processing circuit disclosed in Japanese Patent Laid-Open No. 54-130835. First, the configuration of this circuit will be described. In the figure, input terminal 100
Is connected to the adder circuit 12 and is also connected to the adder circuit 12 via the 1H delay line 4. The adder circuit 12 is an amplitude limiting circuit
14, connected to the phase inversion circuit 17 via the level adjustment circuit 16. The input terminal 100 and the phase inversion circuit 17 are addition circuits 20.
And the adder circuit 20 is connected to the output terminal 200.

Next, the operation of this circuit will be described. The input chroma signal 1 from the input terminal 100 is delayed by 1H by the 1H delay line 4 to become the delay line output 5, and a comb filter is formed by adding the input chroma signal 1 and the delay line output 5 by the adder circuit 12. , Vertical high frequency components in the vertical spatial frequency band 13
Is obtained. This vertical high frequency component 13 is an amplitude limiting circuit.
The high-level signal component is cut by the amplitude limitation by 14 and becomes only the low-level noise component, and the vertical noise signal 15 is obtained. The vertical noise signal 15 is adjusted by the next level adjusting circuit 6 to have substantially the same level as the level of the noise signal contained in the input chroma signal 1, and then the phase inversion circuit 17 inverts the phase. This phase-inverted signal is added to the input chroma signal 1 by the adder circuit 20, the noise component is removed from the input chroma signal 1, and the signal is output from the output terminal 200.

[Problems to be Solved by the Invention] By the way, it is known that the comb-shaped filter portion of this example is composed of a recursive comb-shaped filter and that the same operation and effect as described above can be obtained. However, in such a case, when the circuit is put in an APC (automatic phase control) loop, the responsiveness of the APC loop is disturbed, and
Had a problem of malfunctioning.

The present invention has been made to solve the above problems, and an object of the present invention is to obtain a color video signal processing circuit in which at least the color burst period APC does not malfunction even if it is placed in the APC loop.

[Means for Solving Problems] A color video signal processing circuit according to the present invention includes a recursive comb filter means for extracting a high frequency component in a vertical spatial frequency band of an input color video signal, and a recursive type. Amplitude control means for limiting the amplitude of the high frequency component output from the comb filter means, addition means connected to receive the amplitude limit signal from the amplitude control means and the input color video signal, and in the color burst period , And prohibiting means for prohibiting the supply of the amplitude limiting signal from the amplitude limiting means to the adding means.

[Operation] In the color video signal processing circuit according to the present invention, due to the operation of the prohibiting means, the adding means outputs the input color video signal in the color burst period. A signal may be output. Therefore, even if the color video signal processing circuit is inserted in the APC loop, the APC loop does not malfunction during the color burst period.

Embodiment An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a block diagram showing a color video signal processing circuit which is an embodiment of the present invention. First, the configuration of this circuit will be described. Output terminal 100 is 1 via adder circuit 2
Connected to H delay line 4. The 1H delay line 4 is connected to the adder circuit 2 via a level adjusting circuit (which adjusts the feedback amount K) 6 and a phase inverting circuit 7, and also has a level adjusting circuit (coefficient 1-K for level normalization). It is connected to an adder circuit 12 via a phase inversion circuit 10. Also input terminal 10
0 is connected to the adder circuit 12. The adder circuit 12 is connected to the phase inverting circuit 17 via the amplitude limiting circuit 14 and the level adjusting circuit 16. The phase inversion circuit 17 includes an adder circuit 20 and a switch 18
The second terminal 1 of the switch 18 connected to the first terminal 181 of
82 is grounded. This switch may be an analog switch or a transistor switch circuit. Reference numeral 19 is a control signal synchronized with the position of the color burst signal. Further, the input terminal 100 is connected to the adder circuit 20,
0 is connected to the output terminal 200.

Next, the operation of this circuit will be described. The input chroma signal 1 from the input terminal 100 is input to the adder circuit 2, and the adder circuit output 3 is obtained and input to the 1H delay line 4. The delay line output 5 delayed by 1H is fed back (K) by the level adjusting circuit 6.
After being adjusted, the phase is inverted by the phase inversion circuit 7, and the feedback signal 8 is input to the adder circuit 2 and becomes a cyclic comb filter. The delay line output 5 which is this output is the level adjusting circuit 9
Is normalized to the level of the input chroma signal 1 by ((1-
K) times), the phase is inverted by the phase inverting circuit 10 to become the cyclic comb filter output 11, which is added to the input chroma signal 1 in the adding circuit 12 to obtain the vertical high frequency component 13. A high level signal of the vertical high frequency component 13 is cut by the amplitude limiting circuit 14. Here, since the high level signal is considered to be a signal component and the low level signal is considered to be a noise component, the output of the amplitude limiting circuit 14 becomes the vertical noise signal 15. The vertical noise signal 15 is adjusted to a level almost equal to the noise component in the input chroma signal 1 by the level adjusting circuit 16, and the phase is inverted by the phase inverting circuit 17. This phase-inverted signal is input to the first terminal 181 of the switch 18 and the addition circuit 20. On the other hand, the second terminal 182 of the switch 18 is grounded, and when the switch 18 is in the OFF state by the control signal 19 synchronized with the color burst signal position, the processed noise signal is input to the adding circuit 20 and The input chroma signal 1 which is the input is arithmetically processed, and the output chroma signal 21 from which the noise signal is removed is obtained at the output terminal 200. On the other hand, when the switch 18 is in the ON state by the control signal 19, the first terminal 181 of the switch 18 is in the ground state and the adder circuit 2
The input of the noise signal to 0 is stopped, and as a result, the addition circuit 2
The input chroma signal 1 which is one of the input signals of 0 becomes the output chroma signal 21 as it is, the signal processing is not performed during the color burst period, and the APC operation is normally performed.

Although the second terminal 182 of the switch 18 is used in the grounded state in the above embodiment, the same effect as in the above embodiment can be obtained with the configuration shown in FIG. In this case, when the switch 18 is ON, the noise-reduced output chroma signal can be obtained, and when the switch 18 is OFF, the input chroma signal becomes the output chroma signal as it is.

Further, although the case where the input signal is the chroma signal has been described in the above embodiment, the input signal may be a luminance signal.

In the above embodiment, the position of the switch 18 is set to the phase inversion circuit.
Although it is after 17, the position may be any position between the adder circuit 12 and the adder circuit 20.

[Effects of the Invention] As described above, according to the present invention, since the prohibiting means is provided so that the adding means outputs the input color video signal during the color burst period, it is possible to insert the prohibiting means into the APC loop. A color video signal processing circuit that does not malfunction during the color burst period was obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing a color video signal processing circuit which is an embodiment of the present invention. FIG. 2 is a block diagram showing a color video signal processing circuit which is another embodiment of the present invention. FIG. 3 is a block diagram showing a conventional color video signal processing circuit. In the figure, 1 is an input chroma signal, 2, 12 and 20 are adder circuits, 3 is an adder circuit output, 4 is a 1H delay line, 5 is a delay line output, 6, 9 and 16 are level adjusting circuits, 7, 10 and 17 is a phase inversion circuit, 8 is a feedback signal, 11 is a cyclic comb filter output, 13
Is a vertical high frequency component, 14 is an amplitude limiting circuit, 15 is a vertical noise signal, 18 is a switch, 19 is a control signal, and 21 is an output chroma signal. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A recursive comb filter means for extracting a high frequency component in a vertical spatial frequency band of an input color video signal, and an amplitude limitation of the high frequency component output from the recursive comb filter means. A color video signal processing circuit comprising: an amplitude limiting means; and an adding means connected to receive the amplitude limiting signal from the amplitude limiting means and the input color video signal, wherein the amplitude limiting is performed during a color burst period. A color video signal processing circuit including a prohibiting means for prohibiting the supply of the amplitude limiting signal from the means to the adding means.