JPS59103491A - Processor of video signal - Google Patents

Abstract

PURPOSE:To compensate signal missing in a color video signal, i.e., so-called dropout, by replacing an output from a chroma processing means of a noise reducer into an input video signal in response to the detection of dropout. CONSTITUTION:A changeover selecting switch 13 is selected and connected to the position (b) at dropout detection and the input color video signal is replaced into a one-frame delay signal from a chroma processing circuit 19. That is, a video signal before one frame subject to chroma processing to take the frame difference in a noise eliminating or noise reducing circuit (noise reducer) is replaced into a dropout part of the input video signal at the changeover selecting switch 13. Since the color video signal whose chroma phase only is inverted before one frame is outputted from the chroma processing circuit 19 at all times in this way, the changeover selecting switch 13 is selected to the terminal (b) and even if the signal is replaced into the dropout part of the input color video signal, the phase continuity of the chrominance carrier signal is kept and no adverse effect is given on the picture quality.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a video signal processing device for compensating for signal loss, so-called dropout, in a color video signal.

[Background technology and its problems]

When transmitting, recording, or reproducing color video signals, so-called dropouts, in which part of the video signal is dropped, may occur.This dropout can be compensated for to create a continuous color video signal without any signal dropouts. Various signal processing devices have been proposed for obtaining the following.

For example, in order to compensate for dropouts in NTSC color video signals, a video signal processing device as shown in FIG. 1 is known. In this Figure 1, input terminal 1
The analog color video signal supplied via the analog-to-digital conversion circuit 2 is converted into a digital color video signal, and the analog color video signal is converted into a digital color video signal via the gate circuit 3.
The frame memory 4 stores data for a vertical period). The one frame delayed digital color video signal read from the frame memory 4 is sent to the digital-to-analog converter 6 via the chroma processing circuit 5, where it is converted into an analog color video signal and taken out from the output terminal 7. When the dropout occurs, a dropout detection pulse is supplied to the control terminal 8 of the gate circuit 3 to control the gate circuit 3 to a cut-off state, and the writing of the digital color video signal to the frame memory 4 is stopped. . Therefore, in the portion of the digital video signal stored in the frame memory 4 that corresponds to the above dropout, ■the signal before the frame is that "i!"
, ``i!'' Since there is a strong autocorrelation between frames of general television video, dropout compensation is performed by replacing the dropout portion with a signal from one frame before.

By the way, in the NTSC system, since the phase of the color subcarrier of the color video signal one frame before is inverted,
The carrier color signal of the digital color video signal read out from the frame memory 4 becomes discontinuous at the dropout compensation portion. The chroma processing circuit 5 is for compensating the continuity of such a carrier color signal, and for example, controls to invert the phase of the carrier color signal in accordance with the polarity detection signal of the color subcarrier supplied to the control terminal 10. This ensures continuity. Further, in association with the chroma processing circuit 5, a color subcarrier memory 9 is provided.

In such a conventional video signal processing device, the carrier chrominance signal suddenly becomes discontinuous at the dropout portion of the video signal from the frame memory 4, so that the transient response in the chroma processing circuit 5 causes a transient response in the final image. remains in the interior, causing visual deterioration of the signal.

[Purpose of the invention]

The present invention has been made in view of the above-mentioned circumstances, and provides a video signal processing device that can perform dropout compensation without causing adverse effects such as transient growth on the final image, and has a simple circuit configuration. With the goal.

[Summary of the invention]

That is, the video signal processing device according to the present invention has first and second selected terminals that are switched and selected in response to a dropout detection signal that detects a dropout of an input color video signal. a switching selection means supplied to the first selected terminal; a frame delaying means for delaying the output video signal from the switching selection means by two vertical periods; and a video signal of the previous frame obtained from the frame delaying means. and chroma processing means such as a chroma inverter for matching the phase of the carrier color signal of the input video signal with the phase of the carrier color signal of the input video signal, and the output signal from the chroma processing means is transmitted to the second switch selection means. Normally, the first selected terminal of the switching selection means is selected, and the input video signal is supplied to the selected terminal based on the output signal from the switching selection means and the output signal from the chroma processing means. 4- In order to reduce the noise component of the input video signal, the second selected terminal of the switching selection means is switched and selected when the omission of the input video signal is detected,
The present invention is characterized in that the signal from the chroma processing means is outputted from the switching selection means.

〔Example〕

FIG. 2 shows a video signal processing device as an embodiment of the present invention. In FIG. 2, the input terminal 11 has a signal dropout portion, such as a reproduced video signal from a video tape recorder.
A TSC color video signal is supplied. For example, a drop in the level of this input color video signal is detected by a dropout detection circuit (not shown) to obtain a dropout detection pulse. The analog color video signal from the input terminal 11 is sent to an analog-to-digital converter (A-D).
The signal is converted into a digital color video signal by a converter (converter) 12, and is supplied to one selected terminal a of the changeover selection switch 13. This changeover selection switch 13 is controlled in response to the dropout detection pulse supplied to the control terminal 14, and is connected to the selected terminal a when no dropout or dropout occurs.

The output signal from the selection switch 13 is supplied to a frame memory 16 via a subtracter 15.

The frame memory 16 stores one digital color video signal.
It is a memory circuit that can store frames (2 vertical periods),
It is essentially used as a frame delay means for delaying the input video signal by one frame. However, compared to a simple frame delay line, etc., the frame memory 1 of this embodiment
6 has two output terminals 17 and 18, from one output terminal 17 a frame delayed output that is delayed by one frame with respect to the input is obtained, and from the other output terminal 18, for example, a readout signal is obtained. The clock is synchronized with a reference synchronization signal on the output side to obtain a video signal output that has been subjected to so-called time base correction processing.

1 from the above one output terminal 17 of the frame memory 16
The frame-delayed digital color video signal is supplied to a chroma processing circuit 19 such as a chroma inverter, and the phase of the carrier color signal component is inverted. That is, in the NTSC system, since the phase of the chroma signal differs by 180 degrees for each frame, that is, the phase is reversed, the output signal from the chroma processing circuit 19 is delayed by one frame with respect to the input color video signal. The result is a signal with the same chroma phase. The output signal from the ROMA processing circuit 19 is supplied to the subtracter 20 as a subtraction input, and also to the other selected terminal of the changeover selection switch 13. The subtracter 20 subtracts the output signal of the chroma processing circuit 19 from the output signal of the changeover selection switch 13 and supplies this subtracted output signal to the noise extraction circuit 21 .

The noise extraction circuit 21 is for extracting the noise component of the video signal, and this extracted noise component is used in the subtracter 1.
5 as a subtraction input, and is subtracted from the output signal of the changeover selection switch 13.

That is, when the selection switch 13 is connected to the selected terminal a7-, the noise component is removed from the input color video signal in the subtracter 15.

Next, when the dropout is detected, the changeover selection switch 13 is switched to the terminal side, and the input color video signal is replaced with the one-frame delayed signal from the chroma processing circuit 19. That is, the chroma-processed video signal of the previous frame for taking a frame difference in a noise removal or noise reduction circuit (noise reducer) is replaced by a dropout portion of the input video signal at the changeover selection switch 13.

According to such an embodiment of the present invention, the chroma processing circuit 1
9 always outputs a color video signal with only the chroma phase inverted one frame before, so even if you switch the selection switch 13 to the terminal side and replace it with the dropout part of the input color video signal, the carrier color will not change. The phase continuity of the signal is maintained and image quality is not adversely affected. Furthermore, since dropout compensation is performed on the color video signal before it is written into the frame memory 16,
It is possible to prevent disturbances from the dropout portion from entering the noise reducer loose.

In other words, in conventional dropout and dropout compensation, writing to the frame memory is prohibited when a dropout is detected, so the signal from the previous frame remains in the dropout portion of the read video signal. ,
The chroma phase is discontinuous. Even if such a signal is corrected by a chroma processing circuit, etc., the boundary of the discontinuous portion becomes transient due to the circuit response, etc., which appears as impulse-like noise in the final image, causing image quality deterioration. Become.

In contrast, according to the embodiment of the present invention, at the stage of writing to the frame memory 16, the signal is replaced with the signal of the previous frame with the same chroma phase9, and this signal of the previous frame is used for noise reduction in the noise reducer. Since this signal is constantly output as a signal for taking the frame difference, there is no occurrence of transients or the like, and there is no adverse effect on the final image. Further, the chroma processing circuit 19
Since it is used for both noise reduction and dropout compensation, there is no need to perform independent chroma processing for each operation, and the circuit configuration is simplified.

Next, FIG. 3 shows another embodiment of the present invention, so-called 1
This figure shows an example in which a selector switch for dropout compensation is provided on each noise rib of a second-order recursive filter structure.

In FIG. 3, the input color video signal supplied to the input terminal 31 is given a weight of 1 by the coefficient unit 32, and is taken out from the 1-frame delay circuit 33 via the chroma inversion circuit 34. The coefficient unit 35 is applied to the color video signal that has been subjected to chroma phase compensation one frame before.
A noise reducer having a first-order recursive filter structure is constructed by giving a weight of K and adding the outputs from these coefficient multipliers 32 and 35 in an adder 36.

Further, a changeover selection switch 38 whose dropout detection pulse described above is supplied to the changeover control terminal 37 is inserted and connected between the adder 36 and the 1-frame delay circuit 33, and the output from the adder 36 is connected to the changeover control terminal 37. The output from the chroma inversion circuit 34 is connected to the first selected terminal a, and the output from the chroma inversion circuit 34 is connected to the second selected terminal a.
They supply each. Further, the output terminal 39 is connected to the input side of the one frame delay circuit 38.

Note that the changeover selection switch 38 is connected to the input terminal 31 and the coefficient unit 3.
It may be inserted and connected between 2 and 2.

In such another embodiment of the present invention, first, the noise reducer is a recursive filter that temporally averages the input video signal for each frame period, and the frequency transfer characteristic is
As shown in the figure, it appears as a comb-shaped characteristic curve that repeats in units of frame frequency (301 Tz). This characteristic allows general NTSC television video signals to pass through, but
When there is movement in the image, a configuration is added to reduce the above value according to the movement, and afterimages in moving image parts are reduced as a characteristic shown by the broken line in FIG. 4. Further, the chroma inversion circuit 34 inverts the phase of the chroma signal of the color video signal (=11-), and makes the chroma phase, which is inverted every frame in the NTSC system, match between frames. When detecting dropout, the chroma inversion circuit 34
Since the color video signal whose chroma phase has been compensated with a delay of one frame from Out compensation can be performed.

It should be noted that the present invention is not limited to the above-mentioned embodiments. For example, the present invention is not limited to the above-mentioned embodiments. By using the ROMA processing circuit, application to the PAL system can be easily realized, and application to the SECAM system can also be easily realized.

〔Effect of the invention〕

As is clear from the above description, according to the video signal processing device according to the present invention, the noise ribs constituted by the frame delaying means such as a frame memory and the ratio processing means such as a quadrature inverter, etc. Since the output from the chroma processing means is replaced with the input video signal according to dropout detection, it is possible to prevent the occurrence of transients when compensating for the dropout part in conventional dropout compensation circuits, which adversely affects the final image quality. Not only can dropout compensation be performed without leaving any traces, but the chroma processing means that constitutes the noise reducer is also used for dropout compensation, so noise reduction and Dropout compensation can be performed effectively.

[Brief explanation of drawings]

Fig. 1 is a block circuit diagram showing a conventional example, Fig. 2 is a block circuit diagram showing an embodiment of the present invention, Fig. 3 is a block circuit diagram showing another embodiment of the invention, and Fig. 4 is a block circuit diagram showing an embodiment of the present invention. FIG. 4 is a frequency characteristic diagram for explaining the operation of the circuit shown in FIG. 3; 11.31 Input terminal 13.38...Switch selection switch 16...Frame memory 18...Output terminal 19 Chroma processing circuit 33...1 frame delay circuit 34 Chroma inversion circuit patent applicant Sony Corporation agent Patent Attorney Akira Koike - Same
1) Sakae Mura -15-

Claims (1)

[Scope of Claims] Switching selection means having first and second terminals to be selected, an input color video signal being supplied to the first terminal to be selected, and an output video signal output from the switching selection means. a frame delay means for delaying the video signal by two vertical periods; and a chroma processing means for matching the phase of the carrier color signal of the video signal one frame before, obtained from the frame delay means, with the phase of the carrier color signal of the input video signal. The output signal from the chroma processing means is supplied to the second selected terminal of the switching selection means, and normally the first selected terminal of the switching selection means is selected, and the switching selection means The noise component of the input video signal is reduced based on the output signal from the chroma processing means and the output signal from the chroma processing means.
A video signal processing device characterized in that the signal from the chroma processing means is outputted from the switching selection means by switching the selected terminal of the chroma processing means.