JPS61284875A - Waveform shaping circuit - Google Patents

Abstract

PURPOSE:To eliminate noise, and to improve the accuracy in case of a signal processing by converting a signal which is inputted as an analog signal, to a digital signal, and executing the signal processing. CONSTITUTION:A Y signal which is separated by a separating circuit 17 from a video input signal which is inputted from a line 16 is converted to a digital signal by an analog/digital converting circuit 18. This digital signal is inputted to a delaying circuit 19, for instance, it is delayed by one clock, and inputted to a comparing circuit 20. On the other hand, to the comparing circuit 20, a signal from the A/D converting circuit is also inputted. The comparing circuit 20 leads out a signal corresponding to a difference of levels of each input signal, and this signal is superposed onto a signal from said delaying circuit, and converted to an analog signal. At the time of the superposition, a variation of the signal from the delaying circuit is emphasized. Accordingly, the waveform shaping whose variation is emphasized can be executed to the digital signal, therefore, the signal processing accuracy of the waveform shaping can be improved remarkably.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a waveform shaping circuit for emphasizing the outline of a video in, for example, an apparatus for recording or reproducing video signals.

BACKGROUND ART FIG. 2 is a block diagram of a prior art so-called video enhancer. The video input signal is line! 1 to delay lines 2 and 3 connected in series. Delay line 2.3 is connected by line 4. The output end of the delay line 3 is connected via a line 5 to an adder 6,
Line 1 is connected via line 7 to adder 6.

The output of the adder 6 is given to the inverting input terminal of the differential amplifier 8, and the non-inverting input terminal of the differential amplifier 8 is connected to the delay line 2.
The output of is given. On the other hand, the output of delay line 2 is input to adder 10 via line 9. The output of the differential amplifier 8 is applied to the adder 10 . A video output signal with enhanced contours is obtained from the adder 10. Each delay line 2.degree. 3 has a common delay time .DELTA.t.

FIG. 3 is a waveform diagram illustrating the operation of the video enhancer shown in FIG. Referring to FIGS. 2 and 3, the video input signal given as shown in FIG. 3 (1) via line 1 is transmitted via delay lines 2 and 3 as shown in FIG. As shown in FIG. 3 (3), given a delay of Δt,
line! The adder 6 takes the arithmetic mean of the delayed video signal from line 5 and the new video signals from fins 1 and 7. Performs addition processing.

The output from the adder 6 as shown in FIG. 3 (4) and the third
The difference between the video signal given the delay Δt shown in FIG. 2 and the differential amplifier 8 is emphasized.

The output of the differential amplifier 8 shown in FIG.
given to. In the addition n10, the signal via the line 9 given the delay Δt and the signal from the differential amplifier 8 are added together.The output from the addition n10 is as shown in FIG.
As shown in 6), a 98% preshoot waveform and an overshoot waveform O3 are added, resulting in a video output signal with an enhanced outline.

Problems to be Solved by the Invention In such a video enhancer, the signals to be processed are analog signals, and when edge enhancement is attempted, noise increases, making the displayed image difficult to see. There were limits to the improvement of

Therefore, an object of the present invention is to solve the above-mentioned problems and provide a waveform shaping circuit with significantly improved accuracy in signal processing.

Means for Solving the Problems The present invention includes a circuit for converting an analog signal into a digital signal, and a digital signal from the analog/digital conversion circuit is predetermined! ! a comparison circuit that compares the signal from the analog/digital conversion circuit with the signal from the delay circuit and derives a signal corresponding to the difference in level of each signal; signal and
The waveform shaping circuit is characterized in that it includes a circuit that converts a signal on which a signal from a delay circuit is superimposed into an analog signal.

The working analog signal is converted into a digital signal by an analog/digital conversion circuit. This digital signal is applied to a delay circuit that is delayed in a predetermined manner, and the output from the delay circuit is applied to one input side of the comparison circuit. A new signal from the analog/digital conversion circuit is input to the other input side of the comparison circuit. The comparison circuit derives a signal corresponding to the difference in level of each input signal, and this signal and the signal from the delay circuit are superimposed and converted into an analog signal. At the time of the superimposition, the change in the signal from the delay circuit becomes stronger. Therefore, it is possible to perform waveform shaping that emphasizes changes in the digital signal, thereby significantly improving the signal processing accuracy of waveform shaping.

Embodiment FIG. 1 is a block diagram of a so-called video enhancer 15 which is a waveform shaping circuit according to an embodiment of the present invention. line 1
The video input signal input from 6 is a so-called brightness signal/
The color signal separation (Y/C separation) circuit 17 separates the signal into a luminance signal (hereinafter abbreviated as Y signal) and a color signal (hereinafter abbreviated as C signal). The obtained Y signal is an analog signal, and is converted into a digital signal by an analog/defal (hereinafter abbreviated as A/D) conversion circuit 18.

Assuming that the obtained digital signal is an n-bit signal, the digital signal at each point in time consists of bits A0 to An-1.

This digital signal is input to a delay circuit 19 implemented, for example, by a shift register, and is delayed by, for example, one clock. One clock here corresponds to, for example, one pixel (dot) in a displayed image.

The digital signal obtained after being delayed also has n bits, bits B0 to Bn-.

has. This delayed digital signal is sent to the comparator circuit 2.
It is input to 0. On the other hand, a signal from the A/D conversion circuit 18 is also input to the comparison circuit 20 .

In the comparator circuit 20, the most significant bit (MSB) of each input signal
), the bit contents are compared and the signal levels at each clock of each input signal are compared.Here, the overall level of the output from the A/Dgi conversion circuit 18 is
Assume that the overall level of the output from the delay circuit 19 is B. In the comparison circuit 20, A=B
...(1) means that there is no change in density in the video input signal.

When A>B, (2), the video input signal is switching from a dark video to a light video, and A<B...(3)
In this case, the video input signal is switched from a light video to a dark video.

The comparator circuit 20 outputs a preshoot pulse when detecting the state of the second equation, and outputs an openate pulse when detecting the state of the third equation.

Here, the preshoot pulse is a signal that causes the video signal to have a so-called preshoot waveform, and the overshoe pulse is a signal that causes the video signal to have an overshoot waveform. The output of such a comparison circuit 20 is applied to one input side of an addition circuit 21 implemented by, for example, OR dating.

A signal from the delay circuit 19 is applied to the other input side of the adder circuit 21 . The adder circuit 21 performs a logical sum on each bit of each input signal, and sets all bits B0 to Bn-1 of the signal from the delay circuit 19 to rHJ. When the second equation holds, the video signal first has an overshoot. Next, apply preshoot. When the third formula holds true, first a preshoot and then an overshoot are applied to the video signal.

The output from the adder circuit 21 is input to a digital/analog (hereinafter abbreviated as D/A) conversion circuit 22 . D/A
The output of the time changing circuit 22 becomes an analog Y signal. In the obtained Y signal, a preshoot is added followed by an overshoot when the signal rises, and a preshoot is added following the overshoot when the signal falls. In other words, the contour of the signal is strengthened 11f.

As described above, in this embodiment, digital circuits are used to perform signal processing that emphasizes the outline of a video signal. Therefore, accuracy in signal processing is significantly improved, and processing speed is also significantly improved.

Effects According to the present invention as described above, an input analog signal is converted into a digital signal, and the digital signal from this analog/digital conversion circuit is input to a delay circuit where it is delayed in a predetermined manner. . The signal from the analog/digital conversion circuit and the signal from the delay circuit are input to a comparison circuit, and the comparison circuit derives a signal corresponding to the difference in level of each input signal. The signal from the comparison circuit and the signal from the delay circuit are superimposed and converted into an analog signal. Since the signal input as an analog signal is converted into a digital signal and signal processing is performed in this way, noise and the like can be removed and accuracy in signal processing can be improved.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a video enhancer 15 according to an embodiment of the present invention, FIG. 2 is a block diagram of a prior art video enhancer, and FIG. 3 is a waveform diagram illustrating the operation of the video enhancer shown in FIG. .

Claims (1)

[Scope of Claims] A circuit that converts an analog signal into a digital signal, a delay circuit that delays the digital signal from the analog/digital conversion circuit in a predetermined manner, and a signal from the analog/digital conversion circuit. , a comparison circuit that compares the signal from the delay circuit and derives a signal corresponding to the difference in level of each signal, and the signal from the comparison circuit;
A waveform shaping circuit comprising: a circuit that converts a signal superimposed with a signal from a delay circuit into an analog signal.