JPH03258169A - Digital video signal processing device - Google Patents

Abstract

PURPOSE:To improve the accuracy of an analog video signal to be outputted by detecting noise from a frame difference of an input video signal and outputting switchingly a video signal subject to contour compensation and a through video signal by the control of the detection signal. CONSTITUTION:A switch circuit 13 receives an output signal of a contour compensation circuit 5 and a signal subject to time delay compensation for the circuit 5 from the output signal of a signal processing circuit 4 by means of a delay compensation circuit 12 and outputs them switchingly by using an output signal of a detection signal expansion circuit 11. When the output signal of the circuit 11 at L, the output signal of the circuit 5 is selected and when the output signal of the circuit 11 is at H, the output signal of the circuit 12 is selected. A still signal and a moving signal in a general picture are outputted from the switch circuit 13 as a video signal subject to contour compensation according to the operation and noise is outputted from the circuit 13 as a video signal not subject to contour compensation. Then a D/A converter circuit 6 applies D/A-converts the digital video signal outputted from the circuit 5 or 12 to obtain an analog video signal with high accuracy in which the emphasis of noise contour compensation is reduced.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a digital video signal processing device that digitally processes an input analog video signal and outputs it again as an analog video signal, and in particular, it relates to a digital video signal processing device that digitally processes an input analog video signal and outputs it again as an analog video signal. The present invention relates to a digital video signal processing device equipped with a contour compensation circuit.

[Conventional technology]

FIG. 4 is a block diagram showing the configuration of this type of conventional digital video signal processing device. In FIG. 4, 1 is a video signal input terminal for inputting an analog video signal; 2 is a video signal input terminal for inputting an analog video signal;
3 is an analog/digital conversion circuit (hereinafter referred to as A/D conversion circuit) that converts the analog video signal input from the video signal input terminal 1 into an analog/digital state, and 3 is the digital video signal that is the output signal of the A/D conversion circuit 2. A frame memory 4 stores and delays one frame, and inputs the output signal (input digital video signal) of the A/D conversion circuit 2 and the output signal (delayed digital video signal) of the frame memory 3, and performs predetermined digital signal processing. A signal processing circuit 5 inputs the output signal of the signal processing circuit 4 and performs contour compensation; 6 converts the output signal of the contour compensation circuit 5 into a digital/
A digital/analog conversion circuit for analog conversion (hereinafter referred to as a D/A conversion circuit), 7 is a video signal output terminal for outputting an analog video signal which is an output signal of the D/A conversion circuit 6.

Next, the operation of this conventional device will be explained. An analog video signal is input to the video signal input terminal 1. The analog video signal input from video signal input terminal 1 is A/D.
The conversion circuit 2 converts the signal into a digital video signal.

The frame memory 3 stores one frame of the signal output from the A/D conversion circuit 2, delays it, and outputs a signal delayed by one frame.

The signal processing circuit 4 performs predetermined digital signal processing on the signal output from the A/D conversion circuit 2 and the signal output from the frame memory 3. The digitally processed video signal is then input to the contour compensation circuit 5. The contour compensation circuit 5 performs contour compensation in the horizontal and vertical directions of the digital video signal. The D/A conversion circuit 6 performs D/A conversion on the digital video signal output from the contour compensation circuit 5 and outputs an analog video signal. Then, an analog video signal is output to the video signal output terminal 7.

[Problem to be solved by the invention]

Conventional digital video signal processing devices are configured as described above, so when a video signal containing noise is input, the noise is emphasized by the contour compensation circuit, and the accuracy of the output analog video signal is reduced. There was a problem with the decline.

This invention was made in order to solve the above-mentioned problems, and when a video signal mixed with noise is input, the noise is contour compensated and emphasized to reduce the output. An object of the present invention is to obtain a digital video signal processing device that can improve the precision of output analog video signals.

[Means to solve the problem]

The digital video signal processing device according to the present invention includes a subtraction circuit 8 that outputs a difference signal between an input digital video signal from an analog/digital conversion circuit 2 and a delayed digital video signal from a frame memory 3; a noise detection circuit 9 that detects noise from an output signal; a correlated signal removal circuit 10 that detects the correlation between a central sample point and its surrounding points from the output signal of the noise detection circuit 9 and removes correlated signals; A detection signal expansion circuit 11 that expands the output signal of the correlation signal removal circuit 10 in the horizontal and vertical directions, and a contour compensation circuit 5 that expands the output signal of the signal processing circuit 4.
a delay compensation circuit 12 that compensates for the time delay of , and a contour compensation circuit that converts the signal input to the digital/analog conversion circuit 6 when noise is detected by the noise detection circuit 9 and a detection signal is output from the detection signal expansion circuit 11. 13 to the output signal of the delay compensation circuit 12.

[Effect]

The subtraction circuit 8 outputs a difference signal between the input digital video signal from the analog/digital conversion circuit 2 and the delayed digital video signal from the frame memory 3. The noise detection circuit 9 detects noise from the output signal of the subtraction circuit 8. The correlated signal removal circuit 10 detects the correlation between the center sample point and the surrounding points from the output signal of the noise detection circuit 9, and removes the correlated signal. The detection signal expansion circuit 11 expands the output signal of the correlation signal removal circuit 10 in the horizontal and vertical directions. The delay compensation circuit 12 compensates the output signal of the signal processing circuit 4 for the time delay of the contour compensation circuit 5. The switch circuit 13 operates when the noise detection circuit 9 detects noise and the detection signal expansion circuit 11 outputs a detection signal.
The signal input to the digital/analog conversion circuit 6 is switched from the output signal of the contour compensation circuit 13 to the output signal of the delay compensation circuit 12.

[Embodiment] FIG. 1 is a block diagram showing the configuration of a digital video signal processing device according to an embodiment of the present invention.

In FIG. 1, components corresponding to those shown in FIG. 4 are designated by the same reference numerals, and their explanations will be omitted. In FIG. 1, 8 is a subtraction circuit that outputs a difference signal between the input digital video signal from the A/D conversion circuit 2 and the delayed digital video signal from the frame memory 3, and 9 is a subtraction circuit that removes noise from the output signal of the subtraction circuit 8. A noise detection circuit 10 detects the correlation between the central sample point and its surrounding points (for example, the correlation between the horizontal direction and the vertical direction) from the output signal of the noise detection circuit 9, and a correlation signal that removes correlated signals. Removal circuit, 11
2 is a detection signal expansion circuit that stretches the output signal of the correlation signal removal circuit 10 in the horizontal and vertical directions; 2 is a delay compensation circuit that compensates for the time delay of the contour compensation circuit 5 for the output signal of the signal processing circuit 4; Reference numeral 13 designates a signal input to the digital/analog conversion circuit 6 when noise is detected by the noise detection circuit 9 and a detection signal is output from the detection signal expansion circuit 11, from the output signal of the contour compensation circuit 13 to the delay compensation circuit 12.
This is a switch circuit that switches to the output signal.

Next, the operation of this embodiment will be explained. The A/D conversion circuit 2, frame memory 3, signal processing circuit 4, and contour compensation circuit 5 operate in the same manner as in the conventional example. The subtraction circuit 8 is A
The output signal of the frame memory 3 is subtracted from the output signal of the /D conversion circuit 2, and a frame difference signal is output. The noise detection circuit 9 detects noise from the frame difference signal. Generally, noise has no frame correlation, so when the frame difference of the signal is taken, the value is output as a frame difference signal together with the image motion signal. Further, the value of the frame difference signal of the still signal is near "0". Generally, the value of the noise frame difference signal is small. Therefore, the noise detection circuit 9 detects a noisy area as shown in FIG. 2, and outputs an "H" level signal as a detection signal. Next, the correlation signal removal circuit 10 extracts points a to d adjacent to the central sample point S in the horizontal and vertical directions as shown in FIG. It is removed that the sample point S outputs a signal. In a general image, when a moving object with a small level difference from the background exists on the screen, the noise detection circuit 9
Since the value of the frame difference signal is small, an "H" level signal is output as the detection signal. However, since the detection signals from the moving object have a correlation in the horizontal or vertical direction, the correlation signal removal circuit 10 removes the output.

On the other hand, since the detection signal due to noise has no correlation in the horizontal and vertical directions, the correlation signal removal circuit 10 outputs the detection signal. Next, the detection signal expansion circuit 11 expands the detection signal output from the correlation signal removal circuit 10 in the horizontal and vertical directions. This operation detects the noise position on the screen and the area to be contour compensated. The switch circuit 13 receives the output signal of the contour compensation circuit 5 and the signal processing circuit 4.
The output signal obtained by compensating for the time delay of the contour compensation circuit 5 by the delay compensation circuit 12 is inputted, and is switched and output according to the output signal of the detection signal expansion circuit 11. When the output signal of the detection signal expansion circuit 11 is "L" level, the output signal of the contour compensation circuit 5 is selected, and when it is "H" level, the output signal of the contour compensation circuit 5 is selected.
The output signal of the delay compensation circuit 12 is selected. Through the above operation, the still signal and motion signal in the general image are outputted from the switch circuit 13 as a contour-compensated video signal, and the noise is outputted from the switch circuit 13 as a video signal without contour compensation (through video signal). Then, the D/A conversion circuit 6 performs D/A conversion on the digital video signal output from the contour compensation circuit 5 or the delay compensation circuit 12, and outputs an analog video signal from the video signal output terminal 7.

In this way, according to the above embodiment, when there is no noise in the input video signal, the video signal contour-compensated by the contour compensation circuit 5 is selected by the switch circuit 13, and when the input video signal has noise, the video signal is delayed. Since the through video signal from the component compensation circuit 12 is selected by the switch circuit 13, it is possible to obtain a highly accurate analog video signal with reduced emphasis on noise contour compensation.

In the above embodiment, the correlation signal removal circuit 10 detects the correlation in the horizontal direction and the vertical direction with respect to the sample points, but this detection method may be extended to add correlation detection in the diagonal direction.

〔Effect of the invention〕

As described above, according to the present invention, noise is detected from the frame difference of the input video signal, and by controlling this detection signal, the contour-compensated video signal and the through video signal are switched and output. Even if there is noise in the video signal, the enhancement of the contour compensation of the noise is reduced, and therefore the accuracy of the output analog video signal is improved.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of a digital video signal processing device according to an embodiment of the present invention, FIG. 2 is a diagram for explaining input and output signals of a noise detection circuit in this embodiment, and FIG. A diagram showing the positional relationship of sampling points for explaining the operation of the correlation signal removal circuit in this embodiment,
FIG. 4 is a block diagram showing the configuration of a conventional digital video signal processing device. 2... Analog/digital conversion circuit, 3... Frame memory, 4... Signal processing circuit, 5... Contour compensation circuit, 6... Digital/analog conversion circuit, 8...
- Subtraction circuit, 9... Noise detection circuit, 10... Correlation signal removal circuit, 11... Detection signal expansion circuit, 12...
Delay compensation circuit, 13... switch circuit.

Claims (1)

[Claims] An analog/digital conversion circuit that inputs an analog video signal and converts it into a digital video signal, and a digital video signal converted by this analog/digital conversion circuit.
a frame memory that stores and delays frames; a signal processing circuit that receives the input digital video signal from the analog/digital conversion circuit and the delayed digital video signal from the frame memory and performs predetermined digital signal processing; A digital video signal processing device comprising a contour compensation circuit that performs contour compensation on the output signal of the circuit, and a digital/analog conversion circuit that converts the output signal of the contour compensation circuit into an analog video signal, wherein the input digital video signal and the A subtraction circuit that outputs a difference signal from the delayed digital video signal, a noise detection circuit that detects noise from the output signal of this subtraction circuit, and a correlation between the central sample point and its surrounding points from the output signal of this noise detection circuit. a correlated signal removal circuit that detects and removes correlated signals;
a detection signal expansion circuit that expands the output signal of the correlation signal removal circuit in the horizontal and vertical directions; a delay compensation circuit that compensates for the time delay of the contour compensation circuit; a switch for switching the signal input to the digital/analog conversion circuit from the output signal of the contour compensation circuit to the output signal of the delay compensation circuit when noise is detected by the detection circuit and a detection signal is output from the detection signal expansion circuit; A digital video signal processing device characterized by comprising a circuit.