JPS63139487A - Video signal processing circuit - Google Patents

Abstract

PURPOSE:To change a reproduced picture quality characteristic and to improve the picture quality of the entirely of reproduced picture by detecting a noise component from a signal in a noise reduction circuit and changing the quantity of the detail of a non-linear detail circuit. CONSTITUTION:A noise detection circuit 200, when the picture having much noise component is reproduced, detects the noise of 800KHz-1.5MHz component visually unseemly by a band pass filter 30 and an 'L' signal is impressed to the control terminal CON of the non-linear detail circuit 33. Accordingly, a switching transistor 338 is conductive and a luminance signal (d) passes a path which is not non-linear detail processed. When the noise component is a little, an 'H' signal is impressed to the control terminal CON of the non-linear detail circuit 16. Accordingly, the switching transistor 338 is not conductive and the luminance signal (d) is non-linear detail processed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application] The present invention relates to a video signal processing circuit applied to a magnetic recording/reproducing device such as a video tape recorder (hereinafter referred to as VTR).

[Traditional witchcraft]

FIG. 4 is a block diagram showing the video No. 1g processing (Y signal only) applied to a conventional VTR. In the same figure, % (la) and (lb) are video heads installed on the rotating drum (1'' not shown), (2) is a rotary transformer, (3a) and (8b) are head amplifiers, (
4) is Head Ang (8a).

This is a head switch circuit that switches (3b) to 60Hz. (5) is pre-peaking circuit, (6) is FM-AG
Circuit C (7) is a double limiter circuit in which the signal that has passed through the bypass filter and limiter circuit and the signal that has passed through the low-pass filter are mixed in a mixing circuit and then passed through a limiter circuit. 8) is a demodulation circuit that succeeds the FM signal, (9) is a de-emphasis circuit, (
10) is a low-pass filter circuit, (11) is a non-linear de-emphasis circuit, (12) is a picture control circuit, and (18) is a Y/C that mixes the Y signal and C signal.
The mixing circuit Th (14) is an RF equalizer path.

Next, the operation will be explained.

Magnetic data and tape signals are sent to two video heads (LA).

(lb) and is applied to each head amplifier (8a) and (8b) via a rotary transformer (2).

The reproduced signals amplified by the head amplifiers (3a) and (8b) are converted into a continuous signal by a head switch circuit (4), outputted, and supplied to a pre-peaking circuit (5). The reproduction signal whose high frequency has been compensated by the pre-peaking circuit (5) is supplied to the FM-AGC circuit (6) and subjected to AGC. This eliminates the need for channel tuning and provides the optimum FM level. The reproduced signal subjected to FM-AGC is supplied to an RF equalizer circuit (14), and the RF equalizer circuit (14) adjusts the reproduced signal to a predetermined band and removes chroma signals. R
The reproduced signal that has passed through the F-shaped twister circuit (14) is supplied to a double limiter circuit (7).

By the way, if you apply a lot of pre-emphasis.

Although the S/N ratio is improved, the FM signal becomes more susceptible to AM fluctuations during playback, so the negative limiter generates a missing portion of the FM signal, which becomes black and white inversion. Therefore, in this double limiter circuit (7), after extracting high-frequency components that lead to inversion using a high-pan filter (
AM fluctuations are removed), the first limiter is applied, the low-frequency component is extracted with a low-pass filter, mixed with the previously limited high-frequency component, and the mixed signal is applied to the second limiter. , is supplied to the FM demodulation circuit (8). This limiter removes amplitude fluctuations and reproduces high-frequency sidebands lost in the main recording/reproducing system.

The FM demodulated luminance signal is sent to a de-emphasis circuit (9)
is supplied to The de-emphasis circuit (9) uses pre-emphasis to emphasize high-frequency components during recording, so
During playback, high-frequency noise is reduced by attenuating temperature-range components with almost the opposite characteristics.

The luminance signal that has passed through the de-emphasis circuit (9) has cylindrical frequency noise removed by a low-pass filter (10) and is supplied to a non-linear de-emphasis circuit (11).

During recording, the non-linear de-emphasis circuit (11) emphasizes the high-frequency components of the input signal as the level μ becomes lower.
We are currently working on improvements. Nonlinear de-emphasis (1
The luminance signal passed through 1) is supplied to a picture control circuit (12). Picture control circuit (
12] uses a second-order differential method to apply a pre-shot overshoot to the luminance signal (Y signal) to change the outline of the image from sharp to soft. Picture control/VI] luminance signal (Y signal) passing through path (12)
is supplied to a Y/C mixing circuit (13), where it is superimposed with a chroma signal supplied from the other side and output as a video signal.

[Total points that the invention attempts to solve]

Although the video signal processing circuit of a conventional VTR is configured as described above and can reproduce normal playback images, there are measures to further improve the image quality, especially the S/N of the screen.
There were limits to the reform measures that could be taken.

Suitably, S can be used to determine the type of screen, such as bright or dark scenes, or by using a type of magnetic tape for recording and reproducing.
Problems arose, such as when the /N was different and it was difficult to produce the best screen.

This invention was made to solve the above problems, and it detects screen noise depending on the type of screen and tape type, changes the playback image quality characteristics, and improves the overall image quality of the playback screen. An object of the present invention is to provide a video signal processing circuit that can perform the following steps.

[Means for solving intervening points]

A video signal processing circuit according to the present invention includes a noise reduction circuit that includes a cyclic comb filter and outputs a signal with reduced noise components from an input video signal;
Only the noise components are detected from the non-linear detail circuit to which the output signal from the noise reduction circuit is applied and No. 18 in the noise reduction circuit, and the amount of dechie IV of the non-linear detail circuit is adjusted according to the magnitude of input No. 11. The invention is characterized in that it is provided with a noise detection circuit that controls the noise.

Here, the noise has a cyclic comb filter.

A method for improving image quality using a reduction circuit (100) focuses on the emotions contained in the image command signal, and attempts to collect them and use them to improve image quality.

Since television signals have a large vertical correlation, it is possible to add or subtract these signals by considering their polarity, phase, etc. However, on the contrary, the polarity and phase of noise are not constant but random, so addition and subtraction cannot be performed simply, and when these noises are added together, the sum is the square root of the square of - of each noise. It can be expressed as In other words, luminance No. 46 has an amplitude of 2
Although it is twice as large, the noise is four times as large.

[Effect]

In the video signal processing circuit of the present invention, when there are many noise components in the video signal, the frequency characteristics of the video signal are degraded and the noise components are difficult to see, and conversely, when there are few noise components, the frequency characteristics of the video signal are It extends to the temperature range and works to see even the smallest details.

[Example of invention]

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

FIG. 1 shows an example of a video signal processing circuit according to the present invention, and the same parts as those in the conventional circuit are denoted by the same reference numerals and the explanation thereof will be omitted.

In the figure, (21) is an adder connected to the nonlinear de-emphasis circuit (11), and (22) is an adder (
This IH delay circuit is connected to 21) and delays the signal of one scanning line of bll, and is composed of a sieve width CCDIH delay line element. This LH:ji extension circuit (22) has a luminance signal of 0 to 3MHz, so as a ccD purple,
I am using a U680 with a transmission frequency of i10.7MH2.

(23) is a low-pass filter connected to the IH delay circuit (22) to remove noise components, and (24) is a feedback coefficient (
(25) is a first i-multiplier, (26) is a 1, 1 multiplier connected to the first subtractor (25) and amplifies the low frequency component; (27) is an amplifier (26)
The limiter connected to (28) is the limiter rep/L/
A second wave reducer determines (X), and (29) is determined by a second subtracter. These 1H delay circuit (22), Rauban filter (23), limiter (27), etc. constitute a noise reduction circuit (100) having a recursive comb filter.

(30) is a bandpass filter that is connected to the amplifier (26) to detect noise components, (31) is an amplitude detector that detects the amplitude of the noise component, and (32) is a DC amplifier. These bandpass filters (80) and amplitude detector (
81) etc., a noise detection circuit (200) is constructed.

A non-linear detail circuit (83) is connected to the output terminal of the second subtracter (29), and this non-linear detail circuit (83) is connected to the output terminal of the second subtracter (29).
) is controlled by the output of A concrete configuration of this non-linear detail circuit (83) is shown in FIG.

In Figure 2, <88L) is a low-pass filter connected to the input terminal IN, (832) is an emitter follower composed of a PNP transistor, (88i11) is a transistor amplifier with a common base, and (884) is a NPN
Emitter follower made of 14 transistors (8
85) is a bypass filter, and (386) is a circuit of non-linear elements that expands the signal that has passed through the bypass filter (835) by a voltage i;i6, and is made up of a pair of diodes and a capacitor color.

(387) is an emitter follower formed by a PNP transistor (:+), (888) is a bypass filter (8
85) and a nonlinear element circuit (886), and is configured as an analog switch. In the figure, IN is an input terminal, OU
T is an output terminal and %CON is a control terminal.

Next, the operation will be explained.

The demodulated brightness 1.1 (a is the de-emphasis circuit (9)
), a low-pass filter (10) and a non-linear de-emphasis circuit (11) before being applied to an adder (21). The luminance signal a containing this noise component is first filtered through a cyclic low-pass filter formed by 44 adders (21) → IH delay circuit (22) → low-pass filter (28) → first reducer (24). is supplied to Here, the signal from which noise has been removed is obtained as the output of the adder (21).

The IH-delayed luminance signal from the CCD element is applied to a low-pass filter (23), where the COD clock frequency component is removed. The delay amount is LH (63,
5μ5ec). This IH-delayed luminance signal is sent to a first attenuator (24) where a feedback coefficient is determined and an adder (24) is used to determine the feedback coefficient.
1). That is, a recursive low-pass filter is configured as a whole, and a signal waveform is output.

This signal is added to the first subtractor (25) to perform subtraction with the original input signal a, and a bypass signal C containing noise is obtained as an output.The bypass signal C, which is the difference signal, is obtained as the output. is amplified by an amplifier (26) and applied to a second subtracter (29) via a limiter (27).Here, this noise component is subtracted from the original input signal to obtain a noise-reduced reproduction. A signal d is obtained and this signal d is applied to the non-linear detail circuit (88).

On the other hand, only the noise component is extracted from the signal obtained by increasing the bypass signal C using a bandpass filter (aO), and a noise component such as waveform e is detected.

This noise signal ef is detected by an amplitude detector (31).

Furthermore, the DC amplification +9;ji device (32) increases the width by -hJ to control the non-linear detail circuit (33).

As described above, noise components are removed by the vertical noise reduction circuit (100) using a recursive comb filter, and the S/N of the vertical component is improved.

Further, some noise components in this noise reduction circuit (100) are detected, and this noise detection circuit (200) is detected.
) operates a non-linear detail circuit (83) which is a horizontal noise reduction circuit.

In other words, the noise detection circuit (2'OO) produces a visually unsightly 800 K when a screen with many noise components is displayed.
Bypass signal μ (
30), and the output of the DC stage 1 terminal device (32) is 'L'.
', therefore, the 1L' signal is similarly applied to the control terminal CON of the nonlinear detail circuit (33). Therefore, the switching transistor (aaS) conducts,
The luminance signal d of the main floor (the signal that has passed through the cyclic comb-shaped filter) is processed and passed through as indicated by dotted arrow A in the second figure. This arrow A is drawn on a path that has not been subjected to non-linear detail processing.

Next, the noise reduction circuit (100) in the acoustic direction
and when the noise detection circuit (200) detects that the noise component is small.

The bandpass filter (80) generates less mW noise, and the output of the DC'JVi amplifier (32) becomes 1H'. At this time, the control of the nonlinear detail circuit (16) is y, 1
The ``H'' signal is also applied to the ``child CON''. Therefore, the switching transistor (aaS) is non-transparent. be done.

Here, FIG. 3 shows an example of the characteristics of a nonlinear detail section formed by 14 bypass filters (835) and nonlinear element circuits (836).

As shown in Figure 3, the emphasis changes depending on the input level μ of the input signal, and the smaller the input signal, the more (
-5oaa) The amount of emphasis on high frequency components is large, and the detail portion of the video signal is strongly enhanced. In other words, when the directional noise reduction circuit (100) is reproducing a video signal with few noise components, the non-linear detail circuit (3B) provided at the next stage of the noise reduction circuit (100) is operated. Well, the small details of the Irukai J issue are really strong...
It is possible to reproduce a good image in which fine details with a high IL%S/N are emphasized. Also, as mentioned above, S/N
When the image quality is poor and there are many noise components, by bypassing this non-linear detail circuit (33), an image with a high S/N ratio can be reproduced without emphasizing the details.

In addition, the noise reduction circuit (100) having the above-mentioned recursive comb filter, the noise detector (200) i-
and the valley configuration of the nonlinear detail circuit (38) are just examples), and are not limited to these examples.

Further, in the above embodiment, the luminance signal was explained as an example, but the structure of No. 77716 can be similarly configured. In other words, to the extent that this invention was applied to a VH8 system VTR, the effect was greater on the luminance signal than on the chroma signal, but it is possible to apply the invention to both the luminance signal and the chroma signal. It is.

〔Effect of the invention〕

As described above, according to the present invention, the noise detection circuit detects the noise component from No. 46 in the noise reduction circuit, and thereby
Since m is changed depending on the magnitude of the input signal, when reproducing a video signal with few noise components, it is possible to emphasize the details and obtain a reproduced signal with good S/N quality, and when there are many noise components, This has the effect of bypassing the non-linear dechi/l/ circuit and only improving the S/N ratio.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an example in which the video signal processing circuit according to the present invention is applied to a VTR, FIG. 2 is an electric circuit diagram showing a specific example of a non-linear delay circuit in the video signal processing circuit, and FIG. Figure 3 shows the same nonlinear Dichi μ circuit! FIG. 4 is a block diagram showing an example of a video signal processing circuit in a conventional VTR. (83)...Nonlinear detail times m, (100)
... Noise reduction circuit, (200) ... Noise detection circuit. In addition, in the figures, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] (1) A noise reduction circuit that has a cyclic comb filter and outputs a signal with reduced noise components from the input video signal, and a nonlinear detail circuit that receives the output signal from the noise reduction circuit. and a noise detection circuit that detects only noise components from the signal in the noise reduction circuit and controls the amount of detail in the nonlinear detail circuit according to the magnitude of the input signal. .