JPS61167289A - Processing device of video signals - Google Patents

Abstract

PURPOSE:To efficiently remove noise components near the start edge of the horizontal synchronizing signals among the signals by so arranging that a recursive comb-line filter is caused to act at only near the horizontal synchronizing signals among input video signals. CONSTITUTION:The video signals inputted from a terminal 11 are passed through a delay circuit 13 to be video signals delayed by time TD. The delayed video signals are inputted to one input of a switch SW21 and to the recursive comb-line filter 14. The filter 14 has a unit time delay quantity having an integral number of times of a horizontal scanning period and its output is outputted to the other SW21. The start edge of the horizontal synch signals in the input video signals is detected by a pulse generator 12 which then produces the control pulse of a time interval TC(>TD) beginning with the edge to control SW21. This SW21 selects the output of the filter 14 during the control pulse period and selects the delayed video signals during the periods other than the pulse period. In such a manner, noise components free from vertical correlation in the vicinity of the horizontal synchronizing signal can be efficiently removed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is effective for improving the S/N of a horizontal synchronizing signal of a video signal, and is particularly effective for improving the S/N of a horizontal synchronizing signal of a video signal, and is particularly effective for improving the S/N of a horizontal synchronizing signal of a video signal.
The present invention relates to a video signal processing device that can be applied to a video recorder and has great effects.

Conventional technology Conventionally, a video signal processing device for improving the S/N of a video signal processes an input video signal and a signal delayed by one horizontal scanning period at an equal level of 2 bases.

A comb-shaped filter for adding up has been known, but it causes degradation of resolution in the vertical direction. A conventional video signal processing device that solves this problem is disclosed in, for example, Japanese Patent Laid-Open No. 55-80966.

FIG. 6 shows a block diagram of this conventional video signal processing device, in which 1 is a video signal input terminal, and 2 is a video signal input to the input terminal 1 for one horizontal scanning period (this Represented by TH, t2)) is a delay circuit that delays the video signal input from input terminal 1 and delay circuit 3.
The first subtractor 4, which extracts the difference component from the output signal of 6 is a second subtracter that subtracts the output signal of the amplitude limiting circuit 4 from the video signal input from terminal 1; 6 is a subtracter 5;
This is the output terminal for the video signal that is the output of the .

Conventional video signal processing configured as above 3...
− The operation of the equipment shall be explained below.

The video signal input through terminal 1 and this 1H delayed signal (
Generally, there is a strong vertical correlation with the output signal of the delay circuit 2), so the output of the subtraction circuit 3 has a noise component with no vertical correlation (the amplitude is usually small, for example, 1 of the maximum amplitude of the video signal).
It is 0% or less. ) and vertically uncorrelated video signals (
For example, the difference component of the image with an edge in the horizontal direction on the screen can be obtained. The amplitude limiting level of the amplitude limiting circuit 4 is set to be as small as, for example, 10% of the maximum amplitude of the video signal, so when the two signals are input to the amplitude limiting circuit 4, the amplitude of the noise component without vertical correlation is reduced. The signal passes through without being limited, and the large difference components of the video signal without vertical correlation are output with limited amplitude. Therefore, the video signal obtained by subtracting these output signals of the amplitude limiting circuit 4 from the video signal input from the terminal 1 (the output signal of the subtracter 5, which is output from the terminal 6) has no vertical correlation. The noise component is almost completely canceled, and the difference component of the video signal with no vertical correlation whose amplitude is larger than the amplitude limit level (i.e., the noise level) is
Although this is slightly reduced by the amplitude limit level, it is not canceled out. In other words, there is virtually no degradation in resolution in the vertical direction on the screen, and the noise reduction effect is almost the same as that of the conventional comb filter.

In particular, in many home VTRs, the main components of noise, such as cross-modulation components with color signals that occur in the luminance signal during playback and leakage components from adjacent tracks, have a phase inversion between adjacent horizontal sections (this is ), which means that there is no correlation,' means that these noise components are visually inconspicuous, and these noise components can be effectively removed.

Problems to be Solved by the Invention In the long-time recording mode due to narrower tracks in home VTRs, video signals with poor S/N ratio may be played back, and in this case, the phase of the horizontal synchronizing signal may be changed due to noise components. The camera was shaken, causing horizontal fluctuations in the image on the screen, which was more visually unpleasant than the noise.

However, in the above configuration, by increasing the amplitude limiting level of the amplitude limiting circuit 4, the S/N
There are ways to deal with bad video signals, but increasing the amplitude limit level will cause a decrease in vertical resolution and unnatural images, so it is difficult to improve the S/N of the video signal by increasing the noise component. had practical limits.

In view of the above, the present invention provides a video signal that can improve the S/N of the horizontal synchronization signal without causing vertical resolution deterioration or image unnaturalness even if the video signal has large amplitude noise. The purpose is to provide processing equipment.

Means for Solving the Problem The present invention provides a recursive comb filter whose unit time delay is an integral multiple of one horizontal scanning period, and the above-described structure near the start edge of a horizontal synchronizing signal in a video signal. In this case, by applying the recursive comb filter only to the vicinity of the horizontal synchronization signal in the inputted pyro-veinthio signal, the recursive comb filter often causes deterioration of image quality. Noise components with no vertical correlation distributed near a strong horizontal synchronizing signal, particularly near the start edge of the horizontal synchronizing signal, can be efficiently removed by the recursive comb filter regardless of its amplitude.

Embodiment FIG. 1 shows a block diagram of a video signal processing apparatus in a first embodiment of the present invention.

In FIG. 1, 11 is an input terminal for a video signal, 12 is a pulse generation circuit that generates a control pulse, 13 is a delay circuit that delays the input video signal, and 14 is a delay circuit 1.
Recursive comb filter that takes the output of 3 as input, 21
is a switch whose inputs are the two outputs of the delay circuit 13 and the recursive comb filter 14, and which is controlled by the control pulse;
22 is a video signal output terminal. Within the recursive comb filter 14, 16 is the input 7 of this filter.
16 is an adder, 17 is one horizontal scanning period (
18 is a delay circuit 1 which causes a time delay of TH).
7 is a multiplier that inputs the output and multiplies it by a predetermined value k, 19 is an adder, 20 is a multiplier that multiplies by a constant %, and adder 1
6 inputs the outputs of the multipliers 15 and 16, an adder 19 inputs the outputs of the adder 16 and the delay circuit 17, and outputs the output of the multiplier 20 as a filter output.

The operation of the video signal processing apparatus of this embodiment configured as described above will be described below with reference to FIG. FIG. 2 is an operational waveform diagram of each part in FIG. 1, and the shaded areas in the diagram represent noise components.

The video signal inputted from the terminal 11 (FIG. 2a) passes through the delay circuit 13 and becomes a delayed video signal delayed by a time TD (FIG. 2C). The output of the filter 14 (FIG. 2d) becomes the other input of the switch 21. On the other hand, the pulse generating circuit 12 detects the start edge (second edge) of the horizontal synchronizing signal in the video signal input to the terminal 11. In the figure, the falling edge) is detected, and the time width Tc starting from the edge of
A control pulse (>To) (FIG. 2b) is generated. The switch 21 is controlled by this control pulse, and selectively outputs the output of the recursive comb filter 14 during the control pulse period, and selectively outputs the delayed video signal during the period other than the control pulse. From this, the terminal 22 receives the video signal input from the terminal 11 delayed by the time TD,
and around the horizontal synchronization signal in the video signal (here, -T with the start edge of the horizontal synchronization signal as the time reference)
A video signal (FIG. 2e) in which the recursive comb filter 14 acts only on the period from D to (Tc-TD) is obtained.

By the way, the transmission of the recursive comb filter 14 2 1
−to−exp(−TH3) 9 Heno (where S is a complex angular frequency) It is expressed as follows. From this, the gain-frequency characteristic is determined, which is shown in FIG. In this way, the recursive comb filter 14 filters the frequency (%10n) fH (n: an integer greater than or equal to 0, fH: horizontal scanning frequency) and its neighboring frequency components, that is, signals with no vertical correlation or weak vertical correlation. (including noise components). Therefore, when the video signal passes through the recursive comb filter 14, the image quality is significantly degraded. However, the horizontal blanking period including the horizontal synchronization signal is the same for all lines except for the vicinity of the vertical synchronization signal. In other words, the vertical correlation is strong.
In particular, near the start edge of the horizontal synchronization signal, the waveform near the vertical synchronization signal is the same and the vertical correlation is very strong, so all components with no vertical correlation near the horizontal synchronization signal can be regarded as noise components, and the recursive comb filter 14 As a result, noise components during the horizontal blanking period, particularly near the start edge of the horizontal synchronizing signal, are efficiently removed regardless of their amplitude values.

As in the case of 10 vanes or more, according to this embodiment, a recursive comb filter is provided and the recursive comb filter acts only on the vicinity of the start edge of the horizontal synchronization signal, thereby eliminating image quality deterioration. The noise component near the start edge of the horizontal synchronization signal is determined depending on its amplitude.
It can be removed efficiently.

FIG. 4 is a block diagram of a video signal processing device showing a second embodiment of the present invention. Blocks having the same functions as the blocks of the conventional example shown in FIG. 6 and the blocks of the first embodiment of the present invention shown in FIG. In FIG. 4, 31 has a video signal input terminal, 32 has a dropout detection signal input terminal, 33 has two inputs A and B, and the delay circuit 1
A switch 34 has two inputs, C and D, and the output of the adder 16 is the B input, and the switch 34 has two inputs, C and D, and the output of the adder 16 is the B input. 36 is a subtracter that subtracts the output of delay circuit 17 from the output of switch 34; 36 is two inputs E and F; a switch which takes the output of the amplitude limiting circuit 4 as the E input and the output of the multiplier 20 as the F input, and is controlled by the control pulse; 37 is a subtracter that subtracts the output of the switch 36 from the output of the switch 34; 38 is a terminal for outputting the video signal from the subtracter 37.

The operation of the video signal processing device of the second embodiment configured as described above will be described below. The operation can be roughly divided into two cases. One is when the video signal is input normally, and the other is when there is a dropout state, that is, when the input of the video signal is interrupted.

First, we will discuss the operation when a video signal is normally input. In this case, the switch 34 always selects and outputs the C input. During almost the horizontal synchronizing signal period of the video signal input from the terminal 31, the pulse generating circuit outputs a control pulse, and under the control of this control pulse, the switch 33 selects and outputs the B input, and the switch 36 selects the F input. Output. The operation during this control pulse period is ultimately the same as the operation during the control pulse period in the first embodiment of the invention (FIG. 1). That is, multiplier 2 in FIG.
Since the output of subtracter 37 in FIG. 4 is equal to the output of subtracter 37 in FIG. 4, noise components near the horizontal synchronizing signal can be efficiently removed regardless of their amplitude. Next, during a period in which the control pulse is not output, the switch 33 selects and outputs the eight-man power, and the switch 36 selects the five-man power. Therefore, the operation during this period is the same as the operation in the conventional example shown in FIG. 6, and the same S/N improvement effect as in the configuration shown in the conventional example can be obtained.

The operation in the dropout state will be described. During a period when dropout occurs, the switch 34 selects and outputs the C input in response to a dropout detection signal input from the terminal 32. Since the input and output of the delay circuit 17 are connected, the video signal of one horizontal scanning period immediately before dropout occurs can be repeatedly obtained. Since the two manpowers of the subtractor 17 are equal to page 13, the output is zero, and the two manpowers of the switch 36 are both zero, so the switch 3 is output regardless of the control pulse.
6 outputs zero. Therefore, the repeatedly obtained video signal passes through the subtracter 37 and a video signal without dropouts due to dropouts is obtained at the terminal 38.

As described above, according to the present invention, the recursive comb filter operates near the horizontal synchronizing signal, and the switch is added so that the same operation as in the conventional example can be performed in other periods. , without adding an expensive delay circuit (the delay time of the delay circuit 13 can be, for example, several tens of ns to about 100 ns, which can be realized at low cost), and noise components near the horizontal synchronization signal can be removed as efficiently as in the conventional case. Therefore, noise components can be removed in the same way as in the conventional example for periods other than the vicinity of the horizontal synchronizing signal.

In addition, 1. In the second embodiment, the delay time of the delay circuit 17 is set to one horizontal scanning period, but it is clear that the delay time of the portion where the signal circulates may be set to an integral number of 14 pages times the horizontal scanning period.

As described in detail, according to the present invention, noise components near the start end of a horizontal synchronizing signal in a video signal can be efficiently removed, and its practical effects are significant.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a video signal processing device according to an embodiment of the present invention, FIG. 2 is an operation waveform diagram of the embodiment, and FIG.
The figure shows the gain-frequency characteristic diagram of a recursive comb filter.
FIG. 4 is a block diagram of a video signal processing device according to a second embodiment of the present invention, and FIG. 5 is a block diagram of a conventional video signal processing device. 11.31... Video signal input terminal, 12.
. . . Pulse generation circuit, 13 . . . Delay circuit, 14 . . . Recursive comb filter, 15.
18.20... Multiplier, 16.19...
- Adder, 17...Delay circuit having a time delay of one horizontal scanning period, 21゜33.34.36...
- Switch, 22.38...16 page video signal output terminal, 32...dropout detection signal input terminal.

Claims (1)

[Claims] A recursive comb filter whose unit time delay is an integral multiple of one horizontal scanning period, and means for causing the recursive comb filter to act only on the vicinity of the start edge of a horizontal synchronizing signal in a video signal that is an input signal. A video signal processing device comprising: