JP2009282556A - Signal processor and image display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a signal processor for enhancing the sharpness with a configuration simpler than a conventional one. <P>SOLUTION: A determination unit 12 determines whether the region is a flat region or a texture region for each macro block of a video signal Din by utilizing a space frequency distribution (DCT coefficient information DCTout) in encoding. Based on the determination result (determination map Mout), an enhancer 13 applies emphasis processing of a signal to a decoded video signal D3. Thereby, appropriate emphasis processing based on the determination result is achieved in a way easier than a conventional one. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a signal discrimination device that performs enhancement processing on an input video signal, and an image display device including such a signal processing device.

  2. Description of the Related Art Conventionally, an image display device using a video signal has been subjected to various image processing on an input video signal (input video signal) to improve image quality. Among them, signal enhancement processing (enhancement processing) is to enhance the sharpness of an image by enhancing contours (edges) and the like.

  Here, when such enhancement processing is performed, if enhancement processing is uniformly performed on the entire image, noise components included in the image are also emphasized. In particular, the noise component becomes particularly noticeable when the noise component included in the region where the change in luminance and color of the image is small is enhanced. On the other hand, it is possible to prevent the enhanced noise component from conspicuous by suppressing the enhancement amount during the enhancement process. However, in this case, the effect of the enhancement process is reduced as a whole image.

  Therefore, the entire image is a textured part (hereinafter referred to as “texture region”), which is a part where the luminance and color of the image are largely changed, and a flat part where the luminance and color of the image is little changed. There has been proposed a method of performing enhancement processing for each area divided into (Flat) portions (hereinafter referred to as “flat areas”) (see, for example, Patent Documents 1 and 2). Specifically, strong enhancement processing is applied to the texture region, and weak enhancement processing is applied to the flat region so as not to emphasize too much noise components.

Japanese Patent Laid-Open No. 11-316843 JP 2007-65916 A

  By the way, in the conventional enhancement processing proposed in the above-mentioned Patent Documents 1 and 2, etc., after decoding the encoded video signal, the flat region and the texture region are discriminated. In that case, since the decoded video signal includes noise and the like, it is not possible to simply determine an area where the change in luminance or color is small as a flat area. Therefore, in order to make a more appropriate discrimination, it is necessary to estimate the noise level in the decoded video signal and make a decision, or take measures if the noise level is estimated incorrectly. It is done.

  However, if such processing is required, the determination processing becomes complicated. Therefore, it has been desired that the encoded video signal be realized more easily than in the past when discriminating between a flat area and a texture area.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a signal processing device capable of increasing the sharpness of an image with a simpler configuration than before, and an image including such a signal processing device. It is to provide a display device.

  The signal processing apparatus according to the present invention uses the spatial frequency distribution of the macroblock at the time of encoding in the encoded input video signal to determine whether the area is a flat area or a texture area. A discriminating unit for each macroblock of the video signal; and an enhancement processing unit for performing signal enhancement processing on the decoded input video signal based on a discrimination result by the discriminating unit. .

  An image display apparatus according to the present invention includes the determination unit, the enhancement processing unit, and a display unit that displays an image based on a video signal after the enhancement processing by the enhancement processing unit.

  In the signal processing device and the image display device of the present invention, the region of the flat region or the texture region is determined using the spatial frequency distribution of the macroblock at the time of encoding in the encoded input video signal. The determination is performed for each macro block of the input video signal. Based on the determination result, signal enhancement processing is performed on the decoded input video signal. As a result, since discrimination is performed using information at the time of encoding, appropriate enhancement processing based on discrimination results can be easily performed compared to conventional methods that require noise level estimation or misclassification handling processing. Realized.

  According to the signal processing device or the image display device of the present invention, the macro frequency of the input video signal is determined using the spatial frequency distribution of the macro block at the time of encoding to determine which region is a flat region or a texture region. Since it is performed for each block and the signal enhancement processing is performed on the decoded input video signal based on the determination result, appropriate enhancement processing based on the determination result is easier than before. Can be realized. Therefore, it is possible to increase the sharpness of the image with a simpler configuration than in the past.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  FIG. 1 shows the overall configuration of an image display apparatus (image display apparatus 1) according to an embodiment of the present invention. The image display device 1 includes a decoder 11 (encoding processing unit), a determination unit 12, an enhancer 13 (enhancement processing unit), an image processing unit 14, and a display unit 15. The decoder 11, the determination unit 12, and the enhancer 13 correspond to the signal processing device according to an embodiment of the present invention.

  The decoder 11 performs a predetermined decoding process (for example, MPEG (Moving) on an encoded video signal Din (for example, a digital video signal input from a tuner (not shown) or a digital video signal input from a recording medium (not shown)). Decoding processing such as (Picture Experts Group) decoding processing) is performed to generate a decoded video signal Dout (luminance signal) and output it to the enhancer 13. As will be described in detail later, the decoder 11 generates a spatial frequency distribution of macroblocks at the time of encoding in the video signal Din during decoding processing, and outputs it to the determination unit 12. The decoder 11 includes an inverse quantization processing unit 111, an inverse DCT (Discrete Cosine Transform) processing unit 112, and a motion compensation processing unit 113.

  The inverse quantization processing unit 111 performs an inverse quantization process on the encoded video signal Din, thereby generating a video signal D1 and outputting the video signal D1 to the inverse DCT processing unit 112.

  The inverse DCT processing unit 112 performs inverse DCT processing on the video signal D <b> 1 supplied from the inverse quantization processing unit 111 to generate a video signal D <b> 2 and outputs the video signal D <b> 2 to the motion compensation processing unit 113. The inverse DCT processing unit 112 also extracts DCT coefficient information DCTout, which is a spatial frequency distribution of the macroblock at the time of encoding in the video signal Din, and outputs the DCT coefficient information DCTout to the determination unit 12. This DCT coefficient information DCTout is generated at the time of image compression such as MPEG, and is composed of a DCT coefficient matrix composed of 8 × 8 = 64 macroblocks, for example, as shown in FIG. . More specifically, this DCT coefficient matrix is converted into an upper left low frequency region (lower left high frequency region (zigzag scan from the upper left macro block to the lower right macro block) in the order shown in the figure). This is a spatial frequency distribution leading to a higher frequency region than the low frequency region.

  The motion compensation processing unit 113 generates a decoded video signal D3 based on the video signal D2 supplied from the inverse DCT processing unit 112 by performing inter-frame prediction using the motion vector, and supplies the decoded video signal D3 to the enhancer 13. Output.

  The determination unit 12 uses the spatial frequency distribution (DCT coefficient information DCTout) supplied from the inverse DCT processing unit 112 in the decoder 11 to determine which region is a flat region or a texture region. This is performed for each macroblock of Din. Then, such a discrimination result is output to the enhancer 13 as a discrimination map Mout for each macroblock (which is expressed as binarized data for each macroblock which is a flat area or a texture area). It has come to be.

  Specifically, in such DCT coefficient information DCTout, for example, as shown by the reference symbol P1 in FIG. 3A, there are many distributions in the low frequency region, or distributions in the low frequency region. When the value is larger than a predetermined threshold (first distribution threshold), it is determined that the macroblock to be determined is a flat area. Conversely, for example, as indicated by reference numeral P2 in FIG. 3B, the distribution in the high frequency region is large, or the distribution value in the high frequency region is larger than a predetermined threshold (second distribution threshold). In such a case, it is determined that the macroblock to be determined is a texture region. The first distribution threshold and the second distribution threshold are, for example, about 10 to 30 in the case of digital broadcasting, and about 5 or less in the case of package media, for example. .

More specifically, for example, the following methods (1) to (4) can be used as a criterion for discrimination.
(1) When the sum of distribution values in a high frequency region (for example, the frequency region “15” to “63” in FIG. 2) is larger than a predetermined threshold (third distribution threshold), It is determined that the macroblock is a texture region.
(2) The sum of the values obtained by multiplying the distribution values in the high frequency region (for example, the frequency region “15” to “63” in FIG. 2) by the quantization coefficient at the time of encoding is a predetermined threshold value. If larger than (fourth distribution threshold), it is determined that the macroblock to be determined is a texture region.
(3) When the dispersion value in the high frequency region (for example, the frequency region of “15” to “63” in FIG. 2) is larger than a predetermined threshold (first dispersion threshold), white noise is present. It is determined that the macro block to be determined is a flat region regardless of the size of the distribution in the high frequency region.
(4) When the distribution is biased in a specific frequency region (for example, when the dispersion value in the specific frequency region is smaller than a predetermined threshold (second dispersion threshold)), the distribution in the frequency region Regardless of the size, it is determined that the macroblock to be determined is a texture region.

  The enhancer 13 performs a signal enhancement process (enhancement process) on the decoded video signal D3 supplied from the decoder 11 based on the determination result (discrimination map Mout) by the determination unit 12, thereby performing the video signal D4. Is output to the image processing unit 14. Specifically, based on the discrimination map Mout, the macroblock that is determined to be a flat region weakens the enhancement process (a weaker enhancement process is performed), and the macro is determined to be a texture region. In the block, the enhancement process is further strengthened (a stronger enhancement process is performed).

  As described above, since the discrimination result (discrimination map Mout) by the discrimination unit 12 is composed of binarized data, the enhancer 13 performs leveling processing (specifically on the binarized data of the discrimination map Mout). Specifically, it is preferable to perform the enhancement process after performing a filter process using LPF (low-pass filter). This is because the boundary between the macro block in the flat area and the macro block in the texture area becomes inconspicuous.

  The image processing unit 14 performs predetermined image processing (for example, day interlace processing, resolution conversion processing, overdrive processing, etc.) on the video signal D4 after the enhancement processing supplied from the enhancer 13, thereby generating an image. The processed video signal is generated.

  The display unit 15 performs image display based on the video signal after image processing supplied from the image processing unit 14. The display unit 15 includes, for example, an OLED (Organic Light-emitting Diode), an LCD (Liquid Crystal Display), a PDP (Plasma Display Panel), or the like.

  Next, the operation of the image display device 1 of the present embodiment will be described in detail while comparing with the comparative example. FIG. 4 is a block diagram showing the overall configuration of the image display apparatus (image display apparatus 101) according to the comparative example.

  In the image display device 1 according to the present embodiment, the decoder 11 performs a decoding process on the encoded video signal Din, thereby generating a decoded video signal D3 and outputting the decoded video signal D3 to the enhancer 13. The video signal D3 is subjected to signal enhancement processing (enhancement processing) in the enhancer 13, and is output to the image processing unit 14 as the video signal D4. The image processing unit 14 performs predetermined image processing on the video signal D4, and generates a video signal after the image processing. The display unit 15 displays an image based on the video signal after the image processing by the image processing unit 14.

  Here, in the image display apparatus 101 according to the comparative example shown in FIG. 4, after the encoded video signal Din is decoded (decoded) by the decoder 11, the decoded video signal D <b> 3 is decoded by the determination unit 102. Discrimination between a flat area and a texture area is performed. The enhancer 13 performs enhancement processing based on the determination result. Specifically, first, the noise level estimation unit 102A in the determination unit 102 estimates the noise level of the entire screen, and determines the threshold for determination. Next, the area discriminating unit 102B discriminates which area is a flat area or a texture area for each pixel. Then, the entire countermeasure unit 102C takes a countermeasure when the noise level is erroneously estimated (performs processing at the time of erroneous determination), and outputs the determination result (discrimination map Mout101) to the enhancer 13. The reason why the determination unit 102 performs such processing is that the decoded video signal D3 includes noise of the original signal and the like. This is because it cannot be determined.

  However, as described above, if a noise level estimation process in the decoded video signal D3 or a countermeasure process when the noise level estimation is incorrect is required, the determination process by the determination unit 102 becomes complicated.

  On the other hand, in the image display device 1 according to the present embodiment, the determination unit 12 uses the spatial frequency distribution (DCT coefficient information DCTout) of the macroblock at the time of encoding in the encoded video signal Din, Whether the region is a flat region or a texture region is determined for each macroblock of the video signal Din. That is, discrimination processing is performed using information before decoding processing by the decoder 11 (DCT coefficient information DCTout at the time of encoding), not information based on the decoded video signal D3 as in the comparative example. . Based on the discrimination result (discrimination map Mout), the enhancer 13 performs signal enhancement processing on the decoded video signal D3. Specifically, based on the discrimination map Mout, the macroblock that has been determined to be a flat region is further weakened (is subjected to weaker emphasis processing) and is determined to be a texture region. The enhanced macroblock is further enhanced (a stronger enhancement is performed).

  As a result, since discrimination is performed using the information at the time of encoding in the determination unit 12, appropriate enhancement based on the determination result is possible compared to a comparative example that requires noise level estimation or misclassification handling processing. Processing is easily realized.

  As described above, in the present embodiment, the determination unit 12 uses the spatial frequency distribution (DCT coefficient information DCTout) of the macroblock at the time of encoding to determine which region is a flat region or a texture region. Since the discrimination is performed for each macroblock of the video signal Din, and the enhancer 13 performs signal enhancement processing on the decoded video signal D3 based on the discrimination result (discrimination map Mout). Appropriate enhancement processing based on the determination result can be realized more easily than in the past. Therefore, it is possible to increase the sharpness of the image with a simpler configuration than in the past.

  Specifically, when the distribution in the low frequency region is larger than the predetermined first distribution threshold in the DCT coefficient information DCTout, the determination unit 12 determines that the macroblock to be determined is a flat region, When the distribution in the high frequency region is larger than the predetermined second distribution threshold, it is determined that the macroblock to be determined is the texture region, and thus the above-described effects can be obtained. .

  Further, the enhancer 13 determines that the macroblock determined to be a flat region is weakened (applies weaker enhancement processing) and is a texture region based on the determination map Mout. In the macroblock, since the enhancement process is further strengthened (a stronger enhancement process is performed), an appropriate enhancement process based on the determination result (the determination map Mout) can be performed.

  In addition, since the determination is performed in units of macroblocks, in this case, the number of processes is reduced to 1/64 as compared to the case of performing determination in units of pixels as in the comparative example. Therefore, it is possible to perform discrimination processing with less memory than in the comparative example, and it is possible to reduce costs.

  Further, since a circuit such as a noise level measurement of a screen as in the comparative example is not necessary and information before decoding is required, new processing such as conversion to a frequency domain can be eliminated.

  Further, unlike the comparative example, it is not necessary to consider the distortion of the noise distribution, so that it is possible not to be affected by the compression / decompression.

  While the present invention has been described with reference to the embodiment, the present invention is not limited to this embodiment, and various modifications can be made.

  For example, in the discrimination map Mout corresponding to the discrimination result by the discrimination unit 12, for example, as shown in FIG. 5A, when an isolated region of a flat region and a texture region exists, a method such as erosion is used. After such an isolated region is removed by using (see, for example, FIG. 5B; the isolated region is removed and only a large structure region is left), the enhancer 13 performs an enhancement process. Is preferred. As such an isolated point removal method, specifically, for example, “morphological operation” which is an image processing method based on a set theory focusing on the shape is used. Then, erosion (erosion) is performed by a structural element larger than the size of the isolated point to be deleted, and then dilation is performed (in the morphological operation, called opening), so that the isolated point is removed. do it.

  In addition, the boundary between the low frequency region and the high frequency region in the discrimination process described in the above embodiment may be arbitrarily adjustable. Specifically, for example, in the discrimination map shown in FIG. 6A, for example, the frequency region of “54” to “63” in FIG. 2 is used as the high frequency region. In addition, the black part in a figure is a macroblock discriminate | determined from the texture area | region, and the white part in a figure is a macroblock discriminate | determined from the flat area | region. The input image is obtained by applying white noise to an image in which the central portion P3 is a texture region. In FIG. 6A, there are few misidentifications in the noise portion (region other than the central portion P3), but the portion misidentified as a flat region in the central portion P3 that should be originally identified as the texture region. Exists. On the other hand, for example, in the discrimination map shown in FIG. 6B, for example, the frequency region of “21” to “63” in FIG. 2 is used as the high frequency region. That is, even a lower frequency region than that in FIG. 6A is used as a high frequency region. In FIG. 6B, there is no erroneous determination in the central portion P3 that should be determined as a texture region, but there are many erroneous determinations in the noise portion (region other than the central portion P3). In this way, it can be said that the erroneous discrimination due to noise is less when the discrimination is performed in a higher frequency region. Further, it is considered that an appropriate discrimination can be performed for such a small amount of erroneous discrimination area due to noise by performing the above-described removal of isolated points. On the other hand, if the image has less noise, it is better to prioritize the accuracy of texture discrimination and use even lower frequency regions.

  Further, the threshold values (for example, the first to fourth distribution threshold values, the first and second distribution threshold values, etc.) at the time of the discrimination processing described in the above embodiment can be arbitrarily adjusted. Also good. Specifically, in the input image described with reference to FIGS. 6A and 6B, for example, the discrimination map shown in FIG. 7A has a case where the first and second distribution thresholds are large (for example, 100). For example, the discrimination map shown in FIG. 7B is for the case where the first and second distribution thresholds are small (for example, 5). With these discrimination maps, if the same frequency region is used for discrimination, it will be easier to discriminate that it is a flat region if the distribution threshold is increased, and it will be easier to discriminate that it is a texture region if the distribution threshold is increased. I understand.

  Further, for example, when the video signal Din is a P picture (Predictive-coded picture) or a B picture (Bidirectionally predictive-coded picture), a high frequency region (for example, in FIG. 2) in an I picture (Intra-coded picture). In other words, the flat region and the texture region may be discriminated using the sum of the distribution values in the frequency regions of “15” to “63”.

  In the above-described embodiment, the case where the determination map Mout corresponding to the determination result by the determination unit 12 is configured by binarized data has been described. For example, such a determination map is expressed by multi-level data. It may be configured.

  In the above embodiment, the decoded video signal D3 is generated by performing a predetermined decoding process on the encoded video signal Din, and the spatial frequency distribution (DCT coefficient information) is generated at the time of decoding. Although the decoder 11 for extracting (DCTout) is described in the configuration provided in the image display device 1, for example, such a decoder may be provided outside the image display device.

  Furthermore, in the above embodiment, the image processing apparatus has been described as an application example of the signal processing apparatus of the present invention, but the signal processing apparatus of the present invention can be applied to other apparatuses. Specifically, for example, a recording / reproducing apparatus for recording and reproducing a video signal on a recording / reproducing medium such as a DVD (Digital Versatile Disc), a reproducing apparatus for reproducing a video signal recorded on a recording medium such as a DVD, The present invention can also be applied to a receiving device (set top box device) that receives a video signal transmitted from the outside.

1 is a block diagram illustrating an overall configuration of an image display device according to an embodiment of the present invention. It is a schematic diagram showing an example of the production | generation process of DCT coefficient information. It is a schematic diagram showing an example of the produced | generated DCT coefficient information. It is a block diagram showing the whole structure of the image display apparatus which concerns on a comparative example. It is a photograph for demonstrating the removal process of an isolated point. It is a photograph figure for demonstrating the effect at the time of changing the area | region in the case of discrimination | determination. It is a photograph figure for demonstrating the effect at the time of changing the threshold value in the case of determination.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Image display apparatus, 11 ... Decoder, 111 ... Inverse quantization process part, 112 ... Inverse DCT process part, 113 ... Motion compensation process part, 12 ... Discrimination part, 13 ... Enhancer, 14 ... Image process part, 15 ... Display Part, Din, D1 to D4... Video signal, DCTout... DCT coefficient information (spatial frequency distribution), Mout.

Claims (12)

Using the spatial frequency distribution of the macroblock at the time of encoding in the encoded input video signal, it is determined for each macroblock of the input video signal whether the area is a flat area or a texture area. A discriminator to perform,
A signal processing apparatus comprising: an enhancement processing unit that performs signal enhancement processing on the decoded input video signal based on a determination result by the determination unit. The discriminating unit discriminates that the macroblock to be discriminated is a flat region when the distribution in the low frequency region is larger than a predetermined first distribution threshold in the spatial frequency distribution, and the low frequency region The signal processing device according to claim 1, wherein when the distribution in a high frequency region having a higher frequency is larger than a predetermined second distribution threshold, the macroblock to be determined is determined to be a texture region. When the variance value in the high frequency region is larger than a predetermined first variance threshold, the discrimination unit determines that the macroblock to be discriminated is a flat region regardless of the size of the distribution in the high frequency region. The signal processing device according to claim 2, wherein the signal processing device is determined to be present. The signal processing device according to claim 2, wherein a boundary between the low frequency region and the high frequency region can be arbitrarily adjusted. The signal processing device according to claim 2, wherein each of the first distribution threshold and the second distribution threshold can be arbitrarily adjusted. In the spatial frequency distribution, when the dispersion value in a specific frequency region is smaller than a predetermined second dispersion threshold, the determination unit is configured to determine a macro to be determined regardless of the distribution size in the frequency region. The signal processing device according to claim 1, wherein the block is determined to be a texture region. The signal processing device according to claim 1, wherein the enhancement processing unit performs the enhancement processing after removing an isolated region of a flat region and a texture region in a discrimination map corresponding to a discrimination result by the discrimination unit. A discrimination map corresponding to the discrimination result by the discrimination unit is composed of binarized data,
The signal processing apparatus according to claim 1, wherein the enhancement processing unit performs the enhancement process after performing a leveling process on the binarized data of the discrimination map. The decoding processing unit for decoding the encoded input video signal to generate the decoded input video signal and extracting the spatial frequency distribution at the time of decoding. Signal processing equipment. The signal processing apparatus according to claim 1, wherein the spatial frequency distribution is configured by DCT (discrete cosine transform) coefficients. The enhancement processing unit further weakens the enhancement processing for a macroblock determined to be a flat region, and further enhances the enhancement processing for a macroblock determined to be a texture region. The signal processing device according to claim 10. Using the spatial frequency distribution of the macroblock at the time of encoding in the encoded input video signal, it is determined for each macroblock of the input video signal whether the area is a flat area or a texture area. A discriminator to perform,
An enhancement processing unit that performs signal enhancement processing on the decoded input video signal based on a result of the discrimination processing by the discrimination unit;
An image display device comprising: a display unit configured to display an image based on the video signal after the enhancement processing by the enhancement processing unit.

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