JPH0416080A - Television receiver - Google Patents

Abstract

PURPOSE:To decrease a level change when the state changes from a still state to a moving state (or vice vesa) by forming a frame sum signal from a high frequency signal outputted from a frequency difference extraction circuit, using a changeover switch so as to select either the frame sum signal or the high frequency signal and adding the selected signal to a low frequency signal of the video signal. CONSTITUTION:A frequency difference extraction circuit 11 executes the extraction processing of a high frequency component and its output is fed to a frame difference and sum component signal generating circuit 30. The frame difference signal is subject to absolute value processing by an absolute value processing circuit 20 and compared with a reference level at a comparator 21. Thus, a high level switching control signal is obtained for only a large state change of the video signal thereby operating a changeover switch 15. Since a frame sum signal being a correction signal is fed to a reduction signal as a result, a steep level change in the output video signal is corrected.

Description

[Detailed Description of the Invention] ``Industrial Application Field'' φ0 related to a television receiver suitable for application to a system ``Prior Art'' Used as a receiving terminal for a broadcasting system called a high-definition television system. In television receivers,
For still images, temporal interpolation is performed to improve the spatial resolution, and for moving images, intra-field interpolation is applied and signal processing is performed separately, and these are mixed appropriately using the motion detection signal. An output l1ii image signal (output video signal) is obtained.

``B HJ Invention or Solution This signal processing improves the spatial resolution of still images, which creates a difference in resolution from that of moving images.In other words, the frequency bands to be reproduced are different. It ends up.

In general, dynamic Ii! It is said that humans' visual characteristics for ii@ are low, but when something with a high frequency component, such as the detailed 6th part, suddenly starts moving from a stationary state, it still feels visually blurry. .

One reason why the image of something with a high frequency component changes from a stationary state to a moving state feels blurred is because the sense of brightness decreases due to a change in the image amplitude.

As shown in Figure 5, a signal that is outside the recirculation band of a moving image has amplitude in a stationary state as shown in Figure A, but as soon as it enters a moving state, the amplitude disappears, as shown in Figure B. This is the average level (DC value) of the amplitude in a stationary state.

This kind of change in state makes you feel blurry.

Also, if you think about the above in terms of high amplitude parts, you will notice that something that shines brightly when it is stationary loses its shine as soon as it starts moving.

Humans are visually sensitive to changes in brightness level, so they perceive the image as blurry in response to this state change phenomenon. Therefore, when signal processing such as aperture correction is performed to lift the high range of the signal band for contour correction, the difference in amplitude changes becomes larger, and in this case, blurring occurs. The phenomenon becomes more and more noticeable.

The present invention solves the above-mentioned problems and proposes a television receiver that performs image processing that makes the image appear blurry.

"Means for Solving the Problems" In order to solve the above-mentioned problems, the present invention provides a silent image signal processing system, a moving image signal processing system, and a mixing system that mixes the outputs of these to obtain a predetermined video signal. a frequency difference extraction circuit to which the video signal fully output from the mixer is supplied; a frame difference signal and frame summation signal forming circuit formed based on the high frequency signal of the frequency difference extraction circuit; The present invention is characterized in that the level of the frame sum signal that can be added to the low frequency signal of the frequency difference extraction circuit is controlled by the frame difference signal.

``Function'' Focusing on the fact that the human eye recognizes blurry images when it reacts to sudden changes in the brightness level, this invention has developed a system that changes from a stationary state to a moving state (or vice versa). Efforts have been made to reduce level changes when moving.

Therefore, in the first example, a frame sum signal is formed from the high frequency signal output from the frequency difference extraction circuit 11, and either this frame sum signal or the high frequency signal No. 48 is selected by the changeover switch 15. , its output is added to the low-frequency signal of the video signal.

Whether to select the frame sum signal or the high-frequency signal itself can be selected depending on the magnitude of the frame difference signal.

In the second example, the frame sum signal is added to the high frequency signal from the beginning, and the rate of addition can be controlled, for example, linearly, depending on the magnitude of the frame difference signal.

"Example" Next, an example of a television receiver according to the present invention will be described in detail with reference to the drawings.

In this invention, blurred images and AE! Focusing on this, the level change when moving from a stationary state to a moving state is controlled so that it does not become extreme.

That is, if it is in a stationary state one frame before and becomes a moving state in the current frame, the brightness level will change between J frames as in the second section. The greater this level change, the more likely it is to feel blurred.

As shown in FIG. 3, a correction value (level indicated by a broken line) is added to the current frame to reduce the level change or to slow down the level change. This will make the blur less noticeable.

As a correction value, a frame sum signal formed based on a high frequency signal of a still image system is used.

Since still image systems normally perform temporal interpolation, a moving image portion becomes a double image, so it is not possible to always add this correction value.

Therefore, a change from a still state to a moving state is detected using a frame difference signal of a high frequency signal extracted from a video signal, and a correction value component is added only when there is a large change.

Next, contrary to the above, if there is a change from a moving state to a stationary state, or in this case, the correction value is subtracted conversely. Since the frame difference signal has positive or negative polarity depending on the input level of the video signal, in this case as well, it is sufficient to simply add the frame difference signal to the high frequency signal.

The configuration shown in FIG. 1 is a concrete example based on the above correction concept.

In the high-definition television receiver shown in the figure, a temporal interpolation circuit 1 of a still image processing system is applied to an input video signal.
and a video processing system field interpolation circuit 2,
The respective outputs are appropriately mixed in the mixer 3 according to the motion detection signal.

The output of the mixer 3 is supplied to a frequency difference extraction circuit 1, where it is divided into a low frequency signal and a high frequency signal.

The high-frequency signal is the difference in recharging frequency between still image processing and video processing.

Therefore, this frequency difference extraction circuit 11 has a two-dimensional or one-dimensional low-pass filter 12 whose passband is a band corresponding to the reproduction frequency band of the video processing system, and its output and the output from the mixer 3 are The resulting video signal is supplied to the subtracter 13, where high frequency component extraction processing is executed.

The low-pass signal of the video signal that is the output of the low-pass filter 12 is supplied to the adder 14, where it is added to the high-pass signal or frame sum signal (described later) to produce a motion-compensated output video. Signaled.

Therefore, the output of the frequency difference extraction circuit 13 is supplied to the frame difference and sum signal forming circuit 30. This forming circuit 30 is composed of a frame memory 18, an adder 17, and a subtracter 19. Then, the adder 17 outputs a frame sum signal of the high frequency signal, which is attenuated by the multiplication W16. Here, the reason why the multiplier 16 is used as an attenuator is to lower the original level. Therefore, it is also possible to use a low-pass filter instead of the multiplier 116.

The frame sum signal (correction signal) whose level has been lowered is supplied to the changeover switch 15 together with the high frequency signal.

The switching control a<= for the changeover switch 15 is
This uses a signal related to the frame difference signal outputted from the unit 19, and is formed as follows.

That is, the frame difference signal is converted into an absolute value by the absolute value conversion circuit 20, and then compared with a reference level by the comparator 21.

When an image changes from a still image state to a moving image state, or vice versa, the frame difference value increases.

Therefore, the value of the reference level is selected so that when the video signal undergoes a large state change, a switching control signal, which is a comparison output, can be obtained.

As a result, a high-level switching control all signal is obtained only when there is a sudden change in the state of the video signal, and the changeover switch 15 is thereby switched to the illustrated state. As a result, the frame summation signal, which is a correction signal, is added to the low-frequency signal, so that sudden level changes in the output video signal can be corrected.

When the state change of the video@signal is small, the high frequency signal itself or the correction signal can be added to the low frequency signal, so in this case the input video signal becomes the same and there is no level change.

FIG. 4 shows another specific example of this invention.

In this example, a multiplier 16 is connected between an adder 17 provided in a forming circuit 30 and a frame memory 18, and the frame sum signal output from the adder 17 is supplied to the adder 14 as its correction signal. This is the case when the system is configured to do so.

In this case, the frame difference signal output from the subtracter 19 is supplied to the absolute value conversion circuit 20, and the absolute value output thereof is supplied as the coefficient control signal of the multiplier 16. Therefore, the level of the frame sum signal is controlled, for example, linearly by the level of the frame difference signal, and in that state is added to the low frequency signal.

In this way, the level of the output video signal can be corrected in immediate response to state changes.

It is also possible to use an integer number of the frame memories 18 described above, and it goes without saying that when such an integer number is used, changes in the state of the video signal can be detected more accurately.

"Effects of the Invention" As described above, according to the present invention, the change in brightness level when a video signal changes from a static state to a moving state, and vice versa, is controlled to be relatively slow. .

According to this, visual blur that is easily recognized in areas where conditions change rapidly is reduced, and more natural images can be reproduced.

FIG. 3 is an explanatory diagram showing a state of change in brightness level, and FIG. 5 is a diagram showing a reproduction signal obtained by still image processing and moving image processing of a video signal outside the video reproduction band.

１　・・ 2・・・ ３　・・ 11　・・ 12・・ Engineering 5・・ 16・・ 18　・・ 20・・ 21　・・ ・Temporal interpolation circuit ・Field interpolation circuit ・Mixer ・Frequency difference extraction circuit ・Two-dimensional or one-dimensional low-pass filter ・Choice switch ・Multiplier ・Frame memory ・Absolute value circuit fun comparator

[Brief explanation of drawings]

Claims (1)

[Claims] (1) A still image signal processing system, a video signal processing system, a mixer that mixes the outputs of these to obtain a predetermined video signal, and a frequency difference extraction circuit to which the video signal output from this mixer is supplied. A circuit for forming a frame difference signal and a frame sum signal based on the high frequency signal of the frequency difference extraction circuit, and a level of the frame sum signal added to the low frequency signal of the frequency difference extraction circuit. is controlled by the frame difference signal.