JPS6070884A - Edge noise suppression circuit - Google Patents

Abstract

PURPOSE:To reproduce a picture without edge noise by extracting only a high frequency component of an edge part and transmitting it to a limiter to reduce noise of the edge part and adding the result to a low frequency component. CONSTITUTION:The edge suppression circuit is provided between a main deemphasis circuit 20 and a video equalizer circuit 32 in a reproducing circuit of a video tape recorder. The edge noise suppression circuit consists of an LPF28, an HPF29, a limiter 30 and an adder 31. The HPF29 extracts a component including a high frequency noise from an inputted luminance signal, while the LPF28 extracts a low frequency component. The high frequency component is subject to limit by the limiter 30 and added with the low frequency component at the adder circuit 31. Thus, a luminance signal without edge noise is obtained at an output terminal.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a magnetic recording/reproducing device, and particularly to an edge noise suppression circuit optimal for reducing noise generated at the edges of a signal.

[Background of the invention]

FIG. 1 shows a playback block diagram of a video tape recorder (hereinafter abbreviated as VTR). In FIG. 1, l is a magnetic tape, 2 is a magnetic head, 3 is a rotary transformer, 4 is a preamplifier, 5 is a switching amplifier that switches the head channel, 6 is an input terminal for head switching pulses,
7 is a buffer amplifier, 8 is a bypass filter (hereinafter abbreviated as HP P) for extracting the luminance signal, and 9 is a lever that lifts the FM white gear area and improves the frequency characteristics, since the output of the playback head decreases as the frequency increases. Raw FM bekink 1g circuit, 10 is two head output signals (YFM)
AGC amplifier 11 is A to adjust each to a constant value.
12 is a level detection circuit for operating the G C, and 12 is a dropout [lj output 1 white path, 1
3 is the playback FM B Tonk circuit 9 Takagi, Hachito Vy'
A phase compensation circuit for improving the high-frequency phase delay caused by
14 is an inversion prevention circuit that prevents the levels of the carrier and lower side hand from being reversed when the reproduction output decreases mainly due to subbasing cross, etc.; 15 is an IH circuit that prevents the signal loss period from being reversed;
Dropout compensation circuit for interpolating delayed signal C, 16
is the IHMrA circuit, ■7 is the limiter, 18 is the demodulation circuit, 1
9 is a low-pass filter (hereinafter abbreviated as LPF), 20 is a main de-emphasis that returns the main emphasis characteristic in recording to its original state. 21 is a dynamic de-emphasis that returns the main emphasis characteristic to the original, Noise cancellation circuit that removes noise components in the area, 23
is a video amplifier, 24 is a luminance signal output terminal, 25 is a bandpass filter (below) for extracting a chroma signal,
PI' (!, :qsu), 26 is an AGC amplifier for capturing the level of the color burst signal outputted from the two heads, each having a fixed value of 1, and 27 is an AGC amplifier output for color printing raw processing 1 package. This is a terminal for leading to.

All conventional V'♂ are 7. The output of the raw head decreases as the frequency increases. Therefore, the reproduction FM peaking circuit 9
The frequency characteristics are improved by raising the area around the FN1 white carrier. However, due to peaking, the amount of delay in the high frequency band increases, resulting in a delay difference 5 between the high frequency band and the low frequency band. In order to compensate for this, a phase compensation circuit 13 is provided to reduce the delay difference to k
t. I'm making sure I can watch it. However, it is difficult to make the delay amount flat between high and low frequencies, and a delay difference of 8 degrees occurs, which appears as edge noise, especially at the edges of the image.

Furthermore, in a high-density recording VTR that does not have a card band between tracks on a magnetic tape, signals from adjacent tracks become an interference, which appears as edge noise, especially at the edge portions.

Conventionally, flat area noise can be reduced by processing such as the noise canceling circuit 22, but edge noise cannot be reduced and significantly deteriorates the reproduced image. Reducing edge noise greatly contributes to improving image quality.

[Purpose of the invention]

SUMMARY OF THE INVENTION An object of the present invention is to provide an edge noise suppression circuit that suppresses noise generated at edges, which has been a problem in the past, and realizes high-quality images.

[Summary of the invention]

In order to solve this problem, the present invention extracts only the high-frequency components at the edges, reduces the noise at the edges by limiting them, and then adds them to the low-frequency components to create an image without edge noise. be.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIGS. 2 and 3.

In Fig. 2, 28 is LPF, 29 is HP Ii'
.

30 is a limiter, 3 is a brightness (addition circuit that adds the low frequency component and high frequency component of No. 8), 32 is a video equalizer circuit that generates oversheet and oversheet equal to the contour of the image, and 33 is an edge circuit. The other components are the same as those shown in FIG. 1, except for the clip compensation circuit for improving the waveform distortion occurring in the section.

The feature of FIG. 2 is that it has an edge noise suppression circuit composed of 28, 29, 30, and 31.

FIG. 3 shows a block diagram of the edge noise suppression circuit of the present invention, and will be explained using waveforms of each part.

In FIG. 3, 34 is an input terminal for the main de-emphasized luminance signal, and 35 is an output terminal for the luminance signal with reduced edge noise.

The luminance signal input from the input terminal 34 includes high-frequency noise as shown in (a). Signal (al to HPF
29 extracts a high frequency component (b) containing a noise component, and LPF'28 extracts a low frequency component (C). The high-frequency component (bl) is limited by the limiter 30 and added to the low-frequency component (C) by the adder circuit 31.In the end, the luminance signal that has passed through the noise suppression circuit is affected by edge part noise as shown in (d). be removed.

As described above, by using the present invention, edge noise, which has been a problem in the past, can be removed and high-quality images can be reproduced. Incidentally, the flat part noise of the signal (d) can be sufficiently reduced by processing by the noise canceling circuit 22, etc., as in the conventional case.

FIG. 4 shows another embodiment of the invention. In Figure 4,
34 is an IJ miter, 35 is a demodulation circuit, 36 is an LPF, 3
7 is the main de-emphasis, 38 is the IH delay circuit 16
The delayed luminance signal (hereinafter abbreviated as YD) delayed and demodulated by
39 is a switching circuit for a luminance signal (hereinafter abbreviated as Y) and Yr, 40 is a shunsho route, and 41 is an input terminal for A (JC-applied reproduced FM signal). , 42 is a pulse extension circuit for extending the dropout pulse.

The feature of Figure 4 is that HPF29 in Figures 2 and 3 is replaced by LPF.
28. The fact that it is composed of a switching circuit 39 and a subtracting circuit 40, and that the switching circuit 38 is installed in the YL multiplied signal path causes a problem when performing dropout compensation and CCII-L in a video signal using the demodulated YD multiplied signal. The present invention is configured to correct vertical deviation of the chroma signal.

During normal playback, the switches 38 and 39 are in the positions shown.1. The signal is dedicated to the YL multiplied signal reduction circuit 40 and the addition circuit 31 taken out by the PF 28. A Y signal is introduced to another input terminal of the subtraction circuit 40, and the output of the subtraction circuit 40 is Y-YL, which is a signal multiplied by YH.

It is limited by the YH double signal limiter 30, and the adder circuit 3
1, the YL signal is added, resulting in a signal with edge noise suppressed as shown in FIG.

At the time of dropout, the switches 38 and 39 are in opposite positions to those shown. The output of the IH delay circuit 16 is input to the dropout compensation circuit 15 and at the same time to the limiter 34, and via the demodulation circuit 35, LPF 36, and main de-emphasis 37, a YD times signal delayed by IH from the raw signal is derived. Here, the pulse expansion circuit reduces the dropout switching noise by expanding the dropout pulse by at least the sum of the delay times generated by the limiter 34, demodulation (b)% 35, LPF 36, and main emphasis 37. It's suppressed. Subtraction circuit 4
Both inputs of 0 become Y@, and the output becomes 0. On the other hand, the output of the switch 38 is a YD times signal, and as a result, the signal output from the adder circuit 32 at the time of dropout becomes a Y'D signal.

During CCIR, the vertical information of the chroma signal is delayed compared to the luminance signal due to the chroma comb. To solve this problem, the N degree signal may also be delayed. If the switching circuit 38 is set in the opposite position to that shown and outputs the YD multiplied signal, and the switching circuit 39 is set to the shown position and outputs the YH multiplied signal, the output of the adder circuit 31 becomes the YD+YH signal, which is limited by the delay line. It is possible to compensate the YD-fold signal band for the YH-fold signal, eliminate the delay difference with the chroma signal, and obtain a luminance signal with a sufficient band.

As described above, according to the present invention, the filter link is
By realizing an edge noise suppression circuit that requires only one P k', it is possible to perform video dropout compensation and chroma vertical shift correction at CCI 14 by providing a switching circuit in the LPF path, which reduces the cost significantly. It becomes an edge noise suppression circuit with good performance.

FIG. 5 shows a specific circuit of an embodiment of the present invention.

FIG. 5 shows an edge noise suppression circuit composed of one LPF. 51 is an input terminal, and 52 is an output terminal. C
and L P with lx]”, Ql~Q4 and C, J-J with R1
PF, (+Q) +Q8+Q9 and R2 constitute a limiter, and Q3Q5 and RL constitute an adder circuit.

That is, the luminance signal Y inputted from the terminal 51 is guided to Q2, and at the same time only the low frequency component Yr is taken out by the LPF composed of C and 1 and guided to Q3 and Q6. Q
2 and Q3 form a differential amplifier, and only the local component YH is taken out as an output.

However, the current of the current source of the differential amplifier can be adjusted with JO'L2, and if the current is reduced and the point at which the differential amplifier operates as a limiter is determined, the YH acid Acts as a component limiter. The limited YH is collector added to YL by R1- and guided to the terminal 52.

By using the edge noise suppression circuit according to the present invention, edge noise, which has been a problem in the past, can be reduced. However, as shown in Figure 3 ((1)), the edges will become slightly dull. Normally, the reproduced waveform of a VTR is a waveform that is slightly oversheet, so the dullness is hardly a problem.
In the embodiments of the present invention shown in FIGS. 2 and 4, a video equalizer circuit 32 and a clip compensation circuit 33 are provided to compensate for the dullness of the edges. Of course, it is effective to provide the above circuit after the edge noise is suppressed by an edge noise suppression circuit.

FIG. 6 shows a block diagram of the clip compensation circuit 33. 6
1 is an input terminal, 62 is an HPF, 63 is a base clip circuit that extracts only the large amplitude portion of the open castle component, 64 is an attenuator, 65 is an LPF', 66 is a booster circuit, and 67 is an output terminal. The formation of valleys will be explained along the flow of signals.

From No. 100 input from the terminal 61, the iiP F 62 extracts the high frequency component, and the LPF 65 extracts the low frequency component. As for the high-frequency components, only the large-width signal is extracted by base clipping, which is passed through the attenuator 64 and guided to the double-width circuit 66. An adder circuit 66 calculates the low frequency component and the limited large amplitude high frequency component, thereby correcting the dullness of the edge portion.

FIG. 7 shows the A-body side of the video equalizer circuit. 71 is an input terminal, and 72 is a blade terminal. The signal input from terminal 71 force 1 is 1411;, 71! As shown in i and j, a fillet and a barshot are added to the edges to correct the distortion. The sheet amount varies depending on the CR.

〔Effect of the invention〕

According to the present invention, it is possible to suppress errors and noise occurring in the reproduced image 6, reproduce high quality f2, and realize a positive pressure circuit with excellent cost performance.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a conventional Niu circuit, Fig. 2 is a block diagram showing an embodiment of the present invention, Fig. 3 is a trough waveform diagram of the present invention, and Fig. 4 is another embodiment of the present invention. A flock diagram showing,
Fig. 5 is a specific circuit diagram of the present invention, Fig. 6 is a block diagram of the IT clip circuit 481rii, and Fig. 7 is a specific circuit diagram of the Hideman-R Cora 1 circuit. ■...@Ki tape 2...Magnetic head 4...Preamplifier 9...G) Raw P' M peaking 10...A
, GC13...Phase compensation circuit 16...IH delay circuit
18...Value adjustment time 20...Main de-emphasis 21...Dynamic de-emphasis 22...Noise cancel 28...L P F 29...) (P F2O...
Limiter 31... Sword Il arithmetic circuit 32...
Video equalizer 33...Clips 1, 5, Figure 2, Figure 7

Claims (1)

[Claims] 1. A circuit that extracts only the low frequency components of the video signal, a circuit that extracts only the high frequency components, and an amplitude limiter N that suppresses large amplitude signals.
In a magnetic recording and reproducing device consisting of a
An edge noise suppression circuit characterized in that it is provided with an X-adding circuit that adds waveformed signals.