JP2012085241A - Display device and display method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To display a high-definition image by reducing noise in a displayed image when displaying an image captured from an input image signal as a still image.SOLUTION: When displaying the image captured from the input image signal, an image quality adjustment unit 10 performs processing of holding in a frame memory 14 an image B extracted from the input image signal and displaying the image B as a still image on a display part 20, and increases the strength of a three-dimensional NR (noise reduction) part 11 to a predetermined level, and holds images C and D separated by two or more frames in the frame memory 14. Then, the images C and D are compared with each other to discriminate whether the input image signal is a still image without movement or a moving image with movement. When the input image signal is the still image without movement, an image C is output instead of the image B as a captured image.

Description

  The present invention relates to a display device and a display method, and more particularly to a display device having a function of displaying an image captured from an input video signal as a still image and a display method thereof.

  For example, some display devices such as a television device have a still image display function for displaying a displayed image in a stationary state while displaying a received television broadcast signal or an externally input video signal.

  On the other hand, in a display device such as a television device capable of receiving a television broadcast signal, if the reception state of the broadcast signal deteriorates due to factors such as the reception environment, and the electric field strength of the signal received by the antenna decreases, it is superimposed on the video signal. As a result, the ratio of the incoming noise increases, and a failure occurs in the output of the received broadcast signal. Even when the still image is displayed as described above, if the noise level of the input video signal is increased, the captured image becomes a low-quality image with much noise, and the image is displayed as a still image. .

  As a technique for improving image quality when the electrolytic strength of a received signal is low, for example, Patent Document 1 discloses an automatic contrast limiter (ACL) based on an IFAGC (Intermediate Frequency Automatic Brightness Limiter) voltage for adjusting the gain of an intermediate frequency amplifier circuit. ) A television receiver with an ACL voltage control circuit for controlling the voltage is disclosed. This television receiver reduces the contrast of the ACL voltage fed back to the signal processing circuit when the electric field strength of the video signal received by the antenna decreases and the IFAGC voltage exceeds a predetermined value determined by the breakdown voltage of the Zener diode. The beat that appears on the screen when the electric field is weak is made inconspicuous.

  Further, in Patent Document 2, in a television signal receiving apparatus having an AFT (Automatic Fine Tuning) function, the deterioration of the S / N of the detected video signal itself is minimized when the television signal is weak in electric field. Techniques for disclosing are disclosed. The television signal receiving device includes means for detecting the electric field state of the television signal, and when the television signal is in a weak electric field state, the tuning position of the tuner obtained by the normal AFT operation is predetermined so that the image quality becomes slightly sweet. The amount of setting is shifted.

  Patent Document 3 discloses a video signal processing circuit for a mobile TV for obtaining an easy-to-view video even in a weak electric field. This circuit can vary the frequency characteristic of the video signal detected by the video detection circuit in accordance with the signal level detected by the signal level detection circuit that detects the signal level from the audio detection circuit and generates a DC voltage. A frequency characteristic variable circuit is provided, and when the electric field is weak, a high frequency characteristic in the video signal detected by the video detection circuit is dropped by the frequency characteristic variable circuit. As a result, an easy-to-view image with little noise even in a weak electric field is being obtained.

JP 2004-328228 A Japanese Patent Laid-Open No. 2002-314381 JP 2000-341595 A

  For example, in a current television device which is an example of a display device, various types of video signal processing are generally performed on a received video signal. In the video signal processing, various image quality adjustment processes for improving video quality are performed. For example, three-dimensional noise reduction (three-dimensional NR) is used as an image quality adjustment process that makes video signal noise inconspicuous.

As a configuration of a general three-dimensional noise reduction processing unit, image data extracted from an input video signal is input, a difference amount between two consecutive images is obtained in units of pixels, and the obtained difference amount is determined according to the obtained difference amount. One that reduces noise in the time direction by feeding back the output data of the three-dimensional NR adaptively is used.
For example, as illustrated in FIG. 2, the three-dimensional NR unit 11 includes a difference extraction unit 111, a frame memory 112, and a mixing unit 113. The temporally previous frame image held in the frame memory 112 by the difference extraction unit 111. The difference between the input image data and the frame image of the input image data is extracted in units of pixels, and the mixing ratio is determined in units of pixels according to the value. Then, the mixing unit 113 mixes and outputs the temporally previous image and the current image held in the frame memory 112 according to the determined mixing ratio. In this way, three-dimensional noise reduction is to remove noise by mixing images based on the movement between images that are temporally different. It eliminates noise applied to the entire image, improves the texture, and increases the depth. An image is supposed to be realized.

Here, in the display device having the still image display function as described above, the image obtained by capturing the video signal can be continuously displayed as a still image. At this time, when a noisy image is captured and displayed, a still image with a lot of noise and low video quality is displayed.
In order to reduce the noise level, the above three-dimensional noise reduction can be used. The three-dimensional noise reduction is intended to reduce temporally generated noise by mixing temporally different images as described above, so that the image data does not change temporally, that is, an image having no motion. It is effective in the case of. However, in the case of an image with a lot of movement, when these images are mixed, a deterioration of so-called so-called tailing occurs. Therefore, it is not preferable to perform the process of enhancing the three-dimensional noise reduction particularly in the case of a moving image. If a still image is captured with a strong three-dimensional noise reduction during moving image display, a low-quality image is displayed as a still image.

  In such a case, it is possible to determine whether the input video signal is a still image without motion or a moving movie, and in the case of a still image, it is conceivable to apply the three-dimensional noise reduction and capture the image. However, it is difficult for the three-dimensional NR unit 11 to accurately determine a still image. For example, when the image A input to the three-dimensional NR unit 11 is image data having a high noise level, the difference from the image B held in the frame memory 112 becomes large. If noise is not taken into account, since the difference is small in the case of a still image, it can be easily determined that the image is a still image. However, if there is a lot of noise, the difference will increase even with a still image, so it will be erroneously determined as a moving image, and the still image cannot be reliably determined.

  Further, the time difference between the image B stored in the frame memory 112 and the input image A is only one frame, and even in the case of a moving image, if there is relatively little movement between the frames, it is ensured that it is a moving image or a still image. Cannot judge. Further, since the input image A data is not stored in the memory, software processing cannot be performed, and hardware for obtaining the sum of absolute differences between the image A and the image B is required.

  That is, when a captured image is displayed as a still image by the still image display function, if the noise level of the input video signal is large, the captured still image also becomes a low-quality image with much noise. Also, when the intensity of the three-dimensional noise reduction is increased to eliminate this, a noise reduction effect can be obtained if the input video signal is a still image with no motion, but the input video signal is a moving video with motion. If this is the case, a low-quality still image with tailing or the like will be generated. It is sufficient to determine whether the input video signal is a moving image or a still image and to use three-dimensional noise reduction properly. As described above, it was difficult to discriminate.

  The present invention has been made in view of the above circumstances, and when displaying an image captured from an input video signal as a still image, it is possible to reduce the noise of the display image and display a high-quality image. An object of the present invention is to provide a display device and a display method that are made possible.

  In order to solve the above-described problem, a first technical means of the present invention includes an image quality adjustment unit that adjusts an image quality of an input video signal, and a display unit that displays an image whose image quality has been adjusted by the image quality adjustment unit. In a display device having a still image display function for displaying an image captured from a video signal as a still image on the display unit, the image quality adjustment unit includes a three-dimensional noise reduction processing unit that performs a three-dimensional noise reduction process, and a three-dimensional noise A memory for storing a reduction-processed image, and when the image captured from the input video signal is displayed, the memory stores a plurality of images having different processing intensities by the noise reduction processing unit. Any one of the stored images is displayed on the display unit as the captured image.

  In the first technical means, when the captured image is displayed in the first technical means, the image quality adjustment unit holds the first image extracted from the input video signal in the memory, and the display unit And processing the image to be displayed as a still image, increasing the strength of the three-dimensional noise reduction processing unit to a predetermined level, and holding the second and third images having the increased strength in the memory, and 3 is compared to determine whether the input video signal is a still image without motion, and if it is determined that the input video signal is a still image without motion, the second image is replaced with the second image. This image is displayed as the captured image.

  According to a third technical means, in the second technical means, when the image quality adjustment unit determines that the input video signal is not the still image as a result of comparing the second and third images, the second technical means The process of displaying the first image as the captured image is continued without using the first image.

  According to a fourth technical means, in the second or third technical means, the second image and the third image are images separated by two frames or more in the time axis direction. .

  According to a fifth technical means, in any one of the second to fourth technical means, when the image quality adjustment unit compares the second image and the third image, the second image and the third image are compared. The pixel-by-pixel difference from the image is extracted, and the absolute value sum of the extracted differences is calculated for all the pixels of the screen or the partial pixel obtained by thinning out the pixels, and the calculated absolute value sum is calculated from a predetermined value. If it is smaller, it is determined that the input video signal is a still image without movement.

  The sixth technical means includes an image quality adjustment step for adjusting the image quality of the input video signal input to the display device by the image quality adjustment unit of the display device, and a display for displaying the image adjusted in the image quality adjustment step on the display unit. A display method for executing still image display in which an image captured from an input video signal is displayed on the display unit as a still image. In the display method, the image quality adjustment step performs a three-dimensional noise reduction process. A three-dimensional noise reduction process and a storage process for storing an image subjected to the three-dimensional noise reduction process in a memory, and when displaying an image captured from the input video signal, a plurality of noise reduction processes having different intensities An image is stored in the memory, and any image stored in the memory is used as the captured image. It is obtained and wherein the to be displayed on the serial display unit.

  According to the present invention, when an image captured from an input video signal is displayed as a still image, it is determined whether or not the input video signal is a still image, and noise reduction processing is appropriately performed according to the determination result. In addition, it is possible to provide a display device and a display method capable of displaying a high-quality image by reducing noise in the display image.

It is a block diagram for demonstrating one Embodiment of the display apparatus which concerns on this invention. It is a block diagram which shows the structural example of the three-dimensional NR part which performs a three-dimensional noise reduction process.

  The display device according to the present invention performs an image quality adjustment process by at least three-dimensional noise reduction on an input video signal. When an image captured from an input video signal by a still image display function is displayed as a still image, noise is displayed. A plurality of images having different reduction processing intensities are stored in a memory, and any one of the images stored in the memory is displayed as a captured image. In particular, the display device according to the present invention determines whether or not the input video signal is a still image without motion based on an image subjected to strong 3D noise reduction processing. An image with strong 3D noise reduction is displayed as a still image. As a result, in the case of a still image having the effect of three-dimensional noise reduction, it is possible to display an image from which noise has been removed by applying strong three-dimensional noise reduction as a still image.

FIG. 1 is a block diagram for explaining an embodiment of a display device according to the present invention. The display device includes an image quality adjustment unit 10 that adjusts image quality of image data, a display unit 20 that displays image data adjusted by the image quality adjustment unit 10, and image quality parameters for controlling image quality adjustment processing of the image quality adjustment unit 10. An image quality parameter setting unit 30 for setting is provided.
The display device of this embodiment can be implemented as a television device, for example. In this case, a video signal received by an antenna (not shown) is selected by the tuner, demodulated, and input to the image quality adjustment unit 10. In addition, a video signal output from a device externally connected to the television apparatus is input to the image quality adjustment unit 10.

The image quality adjustment unit 10 includes a three-dimensional NR unit 11 that performs three-dimensional noise reduction processing, an IP conversion unit 12 that performs IP conversion, and a scaler 13 that performs scaling processing. In addition, the scaler 13 includes a frame memory 14 that can be used. The image quality adjustment unit 10 is a functional block that adjusts the image quality of image data. In addition to the image quality adjustment processing shown here, for example, one-dimensional filter processing, two-dimensional NR (noise reduction) processing, contour correction processing, and enhancement processing are performed. Etc. can be included.
The image quality adjustment unit 10 performs image quality adjustment according to a parameter (image quality parameter) for controlling the image quality adjustment process output from the image quality parameter setting unit 30.

  The three-dimensional NR unit 11 performs noise reduction processing in the time direction on the image data. As the three-dimensional NR unit 11, a configuration as shown in FIG. 2 described above can be applied. That is, the three-dimensional NR unit 11 obtains a difference amount between continuously input image data in units of pixels and adaptively feeds back three-dimensional NR output data according to the obtained difference amount in the time direction. Reduce noise. Here, the difference between the temporally previous frame and the frame of the input image data is extracted in units of pixels, the mixing ratio is determined for each pixel according to the extracted difference, and the temporally previous frame is determined according to the mixing ratio. And the image data of the current frame are mixed and output. Accordingly, the three-dimensional NR unit 11 includes a frame memory (not shown). For example, a RAM externally connected to the three-dimensional NR unit 11 may be used as the frame memory.

  The intensity of the three-dimensional NR unit 11 can be controlled by an image quality parameter. For example, the intensity adjustment is performed by changing the coefficient for the difference value extracted by the difference extraction unit and changing the mixing ratio. In the case of increasing the intensity, if the difference value is amplified by increasing the coefficient, the mixing ratio of the past images increases. There is also a method of increasing the mixing ratio of past images by adding a constant as an offset to the difference value.

The image output from the three-dimensional NR unit 11 is converted into a progressive image by the IP conversion unit 12. The IP conversion unit 12 also includes a frame memory for image processing.
The scaler 13 performs resolution conversion of the IP-converted image in accordance with the resolution of the display unit 20. Here, the image input to the scaler 13 is held in the frame memory 14, subjected to resolution conversion processing, and output to the display unit 20. The frame memory 14 may be included in the scaler 13 itself. The stored image in the frame memory 14 and the state of noise will be described later.

  The display unit 20 can use display means such as a liquid crystal panel, but the display method is not limited. The scaler 13 converts the resolution of the image according to the resolution of the display screen used for the display unit 20 and outputs the result.

An example of processing when a still image is displayed as a captured image by the display device having the above-described configuration will be described.
When an image is displayed on the display device, an image input to the scaler 13 is usually written to the frame memory 14 as needed, and scaled by the scaler 13 and output to the display unit 20. When the captured image is displayed by the still image display function, the scaler 13 stops the new writing of the input image to the frame memory 14 and the image stored in the frame memory 14 is displayed on the display unit 20. By outputting, the same image is continuously displayed.

  Here, it is assumed that the noise level of an image (image A) input to the image quality adjustment unit 10 is relatively high. Then, it is assumed that the image A is subjected to a three-dimensional noise reduction process by the three-dimensional NR unit 11 and becomes an image B having a medium noise level. The scaler 13 stores the image B in the frame memory 14, stops writing a new image, and outputs an image obtained by converting the resolution of the image B to the display unit 20 as a still image.

  In addition to the above processing, the strength of the three-dimensional NR unit 11 is controlled by the control of the image quality parameter setting unit 30, and the three-dimensional noise reduction processing is performed with the strength increased. Strong intensity refers to processing at a predetermined high intensity level. The scaler 13 stores the image C for one frame obtained by increasing the intensity of the three-dimensional noise reduction in the frame memory. Here, the image C is stored in a different area from the image B without rewriting the image B already stored and held. It is assumed that the image C has a low level of noise due to the effect of noise reduction.

  Further, the image D for one frame for comparison with the image C is stored in the frame memory 14 in a state in which the three-dimensional noise reduction is strengthened as in the case of the image C. The image D is stored in a different area from the images B and C. At this time, the images C and D do not need to be images of frames that are temporally continuous, and can be images that are spaced by two frames or more in time. As an example, they are acquired with a time interval of about 0.5 seconds. As a result, if there is a moving image, there is a high probability that the amount of motion will be larger than when comparing consecutive frames by leaving a time interval of 2 frames or more. It becomes possible to discriminate. These images B, C, and D correspond to the first image, the second image, and the third image of the present invention, respectively.

  Here, the scaler 13 compares the image C and the image D by software processing, and determines whether or not the input video signal is a still image without motion. In this case, the difference for each pixel is extracted as described above, the difference absolute value sum is calculated, and if the difference absolute value sum is smaller than a predetermined level, it can be determined that the image is a still image. Here, since both the image C and the image D are stored and held in the frame memory 14, still image determination can be performed by processing by software. In addition, when it takes time to calculate the absolute difference sum by software processing, the calculation time may be shortened by stopping the difference calculation for all the pixels and calculating the difference between the thinned pixel positions. That is, when comparing the image C and the image D, the still image determination can be performed based on the absolute value sum of the differences extracted for all the pixels of the screen or the partial pixels obtained by thinning out the pixels.

  As a result of comparing the image C and the image D, when it is determined that the input video signal is a still image without motion, the image C is scaled and output instead of the image B output as the capture image. In the case where the input video signal is a still image without motion, the images C and D are high-quality images with a low noise level due to the effect of three-dimensional noise reduction. By replacing this with an image B having a medium noise level, the display image displayed as the captured image can be made high quality.

In addition, as a result of comparing the images C and D, if it is determined that the input video signal is not a still image, the image C and the image D are deteriorated by tailing or the like due to strong three-dimensional noise reduction. Is likely to have occurred. Therefore, in this case, the still image is displayed as it is without replacing the image C with the image B.
As described above, in the scaler 13, images that are separated by two frames or more in time and subjected to strong three-dimensional noise reduction are temporarily stored in the frame memory 14, and these images are compared with each other by software processing. It can be determined whether the signal is a still image without motion. If the determination result is a still image, an image with strong three-dimensional noise reduction is output as a captured image. Thereby, it is possible to reduce the noise of the captured image and display a high-quality video.

DESCRIPTION OF SYMBOLS 10 ... Image quality adjustment part, 11 ... Three-dimensional NR part, 12 ... IP conversion part, 13 ... Scaler, 14 ... Frame memory, 20 ... Display part, 30 ... Image quality parameter setting part, 111 ... Difference extraction part, 112 ... Frame memory 113 ... Mixing part.

Claims (6)

An image quality adjustment unit that adjusts the image quality of the input video signal and a display unit that displays an image whose image quality has been adjusted by the image quality adjustment unit, and a still image that displays an image captured from the input video signal as a still image on the display unit In a display device having an image display function,
The image quality adjustment unit includes a three-dimensional noise reduction processing unit that performs a three-dimensional noise reduction process, and a memory that stores an image subjected to the three-dimensional noise reduction process, and displays an image captured from the input video signal. A display device, wherein a plurality of images having different processing intensities by the noise reduction processing unit are stored in the memory, and any one of the images stored in the memory is displayed on the display unit as the captured image.   The display device according to claim 1, wherein when displaying the captured image, the image quality adjustment unit holds the first image extracted from the input video signal in the memory and stores the first image as a still image on the display unit. In addition to performing display processing, the intensity of the three-dimensional noise reduction processing unit is increased to a predetermined level, the second and third images having the increased intensity are held in the memory, and the second and third images are stored. In comparison, it is determined whether or not the input video signal is a still image without motion, and when it is determined that the input video signal is a still image without motion, the second image is replaced with the first image instead of the first image. A display device that displays as a captured image.   3. The display device according to claim 2, wherein the image quality adjustment unit uses the second image when the input video signal is determined not to be the still image as a result of comparing the second and third images. And a process of displaying the first image as the captured image without continuing.   4. The display device according to claim 2, wherein the second image and the third image are images separated by two frames or more in a time axis direction.   5. The display device according to claim 2, wherein the image quality adjustment unit compares pixels of the second image and the third image when comparing the second image and the third image. 6. The difference between each pixel is extracted, and the absolute value sum of the extracted differences is calculated for all the pixels of the screen or the partial pixels obtained by thinning out the pixels. If the calculated absolute value sum is smaller than a predetermined value, the input video A display device characterized in that a signal is determined to be a still image without movement. An image quality adjustment step for adjusting the image quality of the input video signal input to the display device by the image quality adjustment unit of the display device; and a display step for displaying the image adjusted in the image quality adjustment step on the display unit. In the display method for executing still image display in which an image captured from an input video signal is displayed on the display unit as a still image,
The image quality adjustment step performs a three-dimensional noise reduction process for performing a three-dimensional noise reduction process and a storage process for storing an image subjected to the three-dimensional noise reduction process in a memory, and displays an image captured from the input video signal. At the time, a plurality of images having different noise reduction processing intensities are stored in the memory, and any one of the images stored in the memory is displayed on the display unit as the captured image.

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