JP2010213008A - Signal processing apparatus, video display device and signal processing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a signal processing apparatus capable of achieving more excellent image quality by preventing color saturation effectively relative to a signal processing apparatus that takes into account only a luminance signal. <P>SOLUTION: The signal processing apparatus 1, which inputs a luminance signal Y and color difference signals Cr, Cb of one video image and changes a signal level of the color difference signals Cr, Cb based on the inputted luminance signal Y, comprises: a saturation converter 11 for converting the inputted color difference signal Cr, Cb into a saturation signal S; a luminance/saturation histogram generator 12 for generating a two-dimensional frequency distribution of saturation and luminance based on the luminance signal Y and the color difference signals Cr, Cb; and a color gain calculator 13 for calculating a color gain based on the two-dimensional frequency distribution of luminance and saturation. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a signal processing device that receives a luminance signal and a color difference signal and changes the signal level of the color difference signal based on the input luminance signal, a video display device including the signal processing device, and a signal processing method.

In a video display device, a signal processing device that adjusts a color gain based on a video signal in order to realize good image quality has been proposed (for example, Patent Document 1).
In addition, a signal processing device has been proposed that adjusts color gain according to gradation characteristics, contrast gain, and brightness settings that are optimally changed based on a video signal (for example, Patent Document 2).

Japanese Utility Model Publication No. 1-162883 JP-A-4-229788

However, in the conventional signal processing apparatus, the color gain is adjusted based only on the luminance signal, and the signal level of the color difference signal is not taken into consideration. For this reason, there is a possibility that the color is saturated by adjusting the color gain and the image quality is deteriorated.
As shown in Patent Document 1, in a bright video with a high average luminance, setting a high signal level of the color difference signal tends to be favored as a good image quality. Therefore, as the number of pixels with a high luminance signal increases, the color gain increases. Must be set larger. However, when a pixel having a high luminance signal is included in a pixel having a high luminance signal and a large color gain is set, color saturation occurs.

  The present invention has been made in view of such circumstances, and is configured to determine the signal level change amount of the color difference signal by using not only the information of the luminance signal but also the information of the color difference signal. Compared with a signal processing device that considers only the signal, color saturation can be effectively prevented, and a better image quality can be realized, a video display device including the signal processing device, and An object is to provide a signal processing method.

  The signal processing apparatus according to the present invention receives a luminance signal and a color difference signal of one video, and changes the signal level of the color difference signal based on the input luminance signal. A color difference signal change amount determining means for determining a signal level change amount of the color difference signal based on each signal is provided.

  In the signal processing device according to the present invention, the luminance signal and the color difference signal indicate the luminance and the color of each of the plurality of pixels, and the saturation signal conversion means for converting the input color difference signal into a saturation signal; Saturation histogram generation means for generating a saturation frequency distribution based on the saturation signal converted by the saturation signal conversion means, and the color difference signal change amount determination means is the saturation histogram generation means. Means is provided for determining a signal level change amount of the color difference signal based on the generated frequency distribution.

  The signal processing apparatus according to the present invention includes storage means that is associated with saturation and stores a weighting factor having a larger / smaller value as the saturation value is smaller / larger, and the color difference signal change amount The determination unit multiplies each frequency in the frequency distribution generated by the saturation histogram generation unit by a corresponding weighting factor, and the color difference increases as the addition value of each multiplication value obtained by the multiplication increases / decreases. The signal level change amount is determined so that the signal level of the signal is changed to a higher / lower signal level.

  In the signal processing device according to the present invention, the color difference signal change amount determination unit adds the frequencies equal to or higher than a predetermined saturation in the frequency distribution generated by the saturation histogram generation unit, and an addition value obtained by the addition It is characterized by comprising means for determining the signal level change amount so that the signal level of the color difference signal is changed to a higher / lower signal level as the value is smaller / larger.

  The signal processing apparatus according to the present invention includes a luminance histogram generation unit that generates a luminance frequency distribution based on the input luminance signal, and the color difference signal change amount determination unit is generated by the luminance histogram generation unit. The signal level change amount of the color difference signal is determined based on the frequency distribution.

  In the signal processing device according to the present invention, the luminance signal and the chrominance signal indicate the luminance and color of each of the plurality of pixels, and the chrominance signal converting means for converting the input chrominance signal into a chrominance signal is input. A luminance saturation histogram generating means for generating a two-dimensional frequency distribution of luminance and saturation based on the luminance signal and the saturation signal converted by the saturation signal conversion means, and correspondence to the luminance and saturation The higher the luminance value or the smaller the saturation value, the higher the weighting coefficient, and the storage means for storing the weighting coefficient having a larger value, and the frequency distribution in the frequency distribution generated by the luminance saturation histogram generating means. The signal level change amount so that the signal level of the chrominance signal is changed to a higher / lower signal level as the addition value of each multiplication value obtained by multiplying the corresponding weighting factor is larger / smaller. Determine the color Characterized in that it comprises a signal change amount determining means.

  The signal processing apparatus according to the present invention is configured such that a luminance signal and a color difference signal corresponding to each of a plurality of videos are input, and each video signal determined by the color difference signal change amount determination means A change means for changing the signal level change amount is provided so that the difference between the level change amounts becomes less than a predetermined value.

  The signal processing apparatus according to the present invention is configured such that a luminance signal and a color difference signal corresponding to each of a plurality of videos are input, and each video signal determined by the color difference signal change amount determination means A change means is provided for changing the signal level change amount so that the level change amount is less than a predetermined value.

  The signal processing apparatus according to the present invention includes scene change detection means for detecting a change in a scene related to a video based on a luminance signal or a color difference signal of each of a plurality of videos, and the change means includes the scene change detection means. When a change in scene is detected, the change process is stopped.

  A video display device according to the present invention includes any one of the signal processing devices described above, and a display unit that displays a video based on a luminance signal and a color difference signal processed by the signal processing device. To do.

  The signal processing method according to the present invention is a signal processing method for inputting a luminance signal and a color difference signal of one video and changing a signal level of the color difference signal based on the input luminance signal. The signal level change amount of the color difference signal is determined based on each signal.

  In the present invention, the signal level change amount of the color difference signal is determined based on each of the luminance signal and the color difference signal. That is, the signal level of the color difference signal is changed in consideration of the signal level of the color difference signal. Therefore, it is possible to prevent color saturation due to the change of the color difference signal.

  In the present invention, the color difference signal is converted into a saturation signal to generate a saturation frequency distribution. Then, a signal level change amount of the color difference signal is determined based on the generated saturation frequency distribution. That is, the signal level of the color difference signal of each pixel is changed in consideration of the saturation of the entire video.

  In the present invention, each frequency in the saturation frequency distribution is multiplied by a weighting coefficient corresponding to the saturation of the frequency, and an addition value of each multiplication value obtained by multiplication is calculated. The weighting coefficient is associated with the saturation, and has a larger value as the saturation value is smaller. Then, the signal level change amount is determined so that the signal level of the color difference signal is changed to a higher signal level as the calculated addition value is larger. In other words, the signal level change amount is determined so that the signal level of the color difference signal is changed to a lower signal level as the calculated addition value is smaller. Therefore, when the signal level of the color difference signal in the entire video is high, the signal level change amount can be suppressed.

  In the present invention, the frequencies equal to or higher than the predetermined saturation in the saturation frequency distribution are added. Then, the signal level change amount is determined such that the smaller the added value obtained by the addition, the higher the signal level of the color difference signal is changed. In other words, the signal level change amount is determined so that the signal level of the color difference signal is changed to a lower signal level as the added value obtained by the addition is larger. Therefore, when the signal level of the color difference signal in the entire video is high, the signal level change amount can be suppressed.

  In the present invention, a frequency distribution of luminance is generated based on the input luminance signal. Then, the signal level change amount of the color difference signal is determined based on the generated luminance frequency distribution.

In the present invention, the color difference signal is converted into a saturation signal, and a two-dimensional frequency distribution of luminance and saturation is generated. Next, each frequency in the frequency distribution of luminance and saturation is multiplied by a weighting factor corresponding to the luminance and saturation of the frequency, and an addition value of each multiplication value obtained by multiplication is calculated. The weighting coefficient is associated with luminance and saturation, and has a larger value as the luminance value is larger or the saturation value is smaller. Then, the signal level change amount is determined so that the signal level of the color difference signal is changed to a higher signal level as the calculated addition value is larger. In other words, the signal level change amount is determined so that the signal level of the color difference signal is changed to a lower signal level as the calculated addition value is smaller. Therefore, when the signal level of the color difference signal in the entire video is high, the signal level change amount can be suppressed.
In addition, when the signal level of the luminance signal in the entire video is high, the signal level of the color difference signal is changed to a higher signal level. Therefore, even if the luminance of the entire video is high, a colorful video can be realized. Can do. Further, since the signal level change amount can be suppressed when the signal level of the luminance signal in the entire video is low, color noise can be suppressed even when the luminance of the entire video is low.

  In the present invention, it is possible to prevent a sudden color change by changing the signal level change amount so that the signal level change amount does not change abruptly.

  In the present invention, it is possible to prevent the color of the video from changing unnaturally by suppressing the signal level change amount to less than a predetermined value.

  In the present invention, when there is a scene change related to an image, the color difference signal is changed based on the signal level change amount regardless of the change or value of the signal level change amount.

  According to the present invention, color saturation can be prevented, and a better image quality can be realized as compared with a signal processing device that considers only a luminance signal.

It is a block diagram which shows the video display apparatus which concerns on embodiment of this invention. It is explanatory drawing which shows notionally the two-dimensional frequency distribution of a brightness | luminance and saturation. It is explanatory drawing which shows notionally the weighting coefficient which weighting factor LUT memorize | stores. It is explanatory drawing which shows a gain table notionally. It is a block diagram which shows the video display apparatus concerning the modification 1. It is explanatory drawing which shows notionally the frequency distribution of saturation. It is explanatory drawing which shows notionally the weighting coefficient which weighting factor LUT memorize | stores. It is explanatory drawing which shows a gain table notionally. It is a block diagram which shows the video display apparatus which concerns on the modification 2. It is explanatory drawing which shows notionally the frequency distribution of saturation, and the processing content of a color gain calculation part. It is explanatory drawing which shows a gain table notionally. It is a block diagram which shows the video display apparatus concerning the modification 3. It is explanatory drawing which shows a gain table notionally. It is a block diagram which shows the video display apparatus which concerns on the modification 4. It is explanatory drawing which shows a gain table notionally. It is a block diagram which shows the video display apparatus which concerns on the modification 5. It is a flowchart which shows the process sequence of CPU which concerns on the signal processing method of this invention.

Hereinafter, the present invention will be described in detail with reference to the drawings illustrating embodiments thereof.
FIG. 1 is a block diagram showing a video display apparatus according to an embodiment of the present invention. The video display apparatus according to the present embodiment includes a signal processing apparatus 1 and a signal processing apparatus 1 that perform correction of the luminance signal Y and the color difference signals Cr and Cb indicating the luminance and color of each of a plurality of pixels constituting the video. A display unit 2 is provided that displays an image based on the signal-processed luminance signal Yout and color difference signals Crout and Cbout. The video display apparatus according to the present embodiment adjusts the color gain using a two-dimensional histogram of luminance and saturation, and makes it possible to obtain good image quality.

  The video display device receives a video signal with a tuner (not shown), extracts a luminance signal Y and color difference signals Cr and Cb from the received video signal, and outputs the extracted luminance signal Y and color difference signals Cr and Cb. This is given to the processing apparatus 1. The luminance signal Y and the color difference signals Cr and Cb include information on the luminance and color of the pixels constituting each of a plurality of videos that are continuous in time series, that is, a plurality of frames. In the following, in the present embodiment, for the sake of simplicity of explanation, processing performed mainly on one frame of video will be described. However, similar processing is also performed on video of each frame consecutive in time series. To do.

  The signal processing apparatus 1 includes a saturation conversion unit (saturation signal S conversion unit) 11, a luminance / saturation histogram generation unit (luminance / saturation histogram generation unit) 12, and a color gain calculation unit (color difference signals Cr and Cb change amount determination unit). ) 13, a color gain changing unit (changing unit) 14, a color difference signal changing unit 15, a scene change detecting unit (scene change detecting unit) 16, and a luminance signal changing unit 17.

  The saturation conversion unit 11 receives the color difference signals Cr and Cb and converts the input color difference signals Cr and Cb into a saturation signal S. The saturation signal S indicates the saturation of each of the plurality of pixels. Then, the saturation conversion unit 11 outputs the saturation signal S obtained by the conversion to the luminance saturation histogram generation unit 12. The signal level of the saturation signal S is expressed by the following formula (1). Here, s is the signal level of the saturation signal S, and Cb and Cr are the signal levels of the color difference signals Cr and Cb.

  The luminance / saturation histogram generation unit 12 receives the luminance signal Y and the saturation signal S output from the saturation conversion unit 11, and based on the input luminance signal Y and saturation signal S of each pixel, Then, a two-dimensional frequency distribution of saturation is generated (see FIG. 2).

FIG. 2 is an explanatory diagram conceptually showing a two-dimensional frequency distribution of luminance and saturation. In the two-dimensional frequency distribution, the signal levels of the luminance signal Y and the saturation signal S are each divided into a plurality of luminance categories and saturation categories. The first axis in the three-dimensional orthogonal coordinate system indicates the signal level of the saturation signal S belonging to each saturation section (hereinafter referred to as saturation level i), and the second axis indicates the luminance signal Y belonging to each brightness section. The signal level (hereinafter referred to as luminance level j) is shown. The third axis in the three-dimensional orthogonal coordinate system is a pixel having a frequency bin _ij in each luminance section and saturation section, that is, a pixel having a luminance signal Y and a saturation signal S at signal levels belonging to the brightness section and saturation section. Indicates the number of
The luminance saturation histogram generation unit 12 outputs the generated two-dimensional frequency distribution, that is, the frequency bin _ij of each luminance division and saturation division to the color gain calculation unit 13.

The color gain calculation unit 13 is provided with a weighting factor LUT (Look up Table) 13b (storage means). The color gain calculation unit 13 includes each luminance classification and chroma output from the luminance saturation histogram generation unit 12. The frequency bin _ij of the frequency division is input and the weight coefficient is read from the weight coefficient LUT 13b.

FIG. 3 is an explanatory diagram conceptually showing the weighting factor stored in the weighting factor LUT 13b. The first axis in the three-dimensional orthogonal coordinate system indicates the saturation level i similar to the two-dimensional frequency distribution, and the second axis indicates the luminance level j. In addition, the third axis in the three-dimensional orthogonal coordinate system indicates the magnitude of the weighting coefficient W _ij associated with each luminance category and saturation category. The weight coefficient W _ij is associated with each luminance category and saturation category, and has a larger value as the saturation level i is smaller or the luminance level j is larger.
The weighting factor W _ij is set so that the higher the luminance level j is, the higher the luminance level j is, that is, the brighter the scene, the larger the color gain G is desired. ing. On the other hand, in order to prevent color saturation, it is desired that the value becomes smaller as the saturation level i is higher, so a smaller value is set for the weighting coefficient _Wij .

  In this embodiment, the weight coefficient LUT 13b as shown in FIG. 3 is provided. However, the weight coefficient may be calculated using an arbitrary function instead of the weight coefficient LUT 13b.

The color gain calculation unit 13 multiplies the input frequency bin _ij of each luminance section and saturation section by the corresponding weight coefficient W _ij read from the weight coefficient LUT 13b, and multiplies each multiplication value W obtained by multiplication. Add _ij x bin _ij . The added value is represented by the following formula (2). Here, n indicates the number of saturation sections, and m indicates the number of luminance sections.

  The color gain calculation unit 13 includes a gain table 13a in which the added value and the color gain g are associated with each other.

  FIG. 4 is an explanatory diagram conceptually showing the gain table 13a. The horizontal axis represents the added value, and the vertical axis represents the color gain g. As shown in FIG. 4, the color gain g has a larger value as the added value is larger. The method for calculating the color gain g is an example, and the color gain g can be calculated using an arbitrary expression, a lookup table, or the like.

  The color gain calculation unit 13 determines a color gain g corresponding to the addition value based on the addition value obtained by addition and the gain table 13a illustrated in FIG. 4, and determines the determined color gain g. Output to the color gain changing unit 14. As will be described later, the color gain g indicates the signal level change amount of the color difference signals Cr and Cb, specifically, the amplification factor of the signal level.

  The color gain changing unit 14 limits the upper limit of the color gain g so that the color gain G finally output to the color difference signal changing unit is less than the predetermined upper limit value, and the color gain G of each frame. A low-pass filter 14b for smoothing fluctuations. The limiter 14a and the low-pass filter 14b are connected in series, for example. In addition, you may comprise so that either one of the limiter 14a or the low-pass filter 14b may be provided.

The limiter 14a compares the color gain g input to the color gain changing unit 14 with a predetermined upper limit value, and if the color gain g is less than the predetermined upper limit value, the color gain g is changed without changing the signal level of the color gain g. When the gain G is output to the color difference signal changing unit 15 and the color gain g is greater than or equal to the predetermined upper limit value, the input color gain g is changed so that the value becomes the predetermined upper limit value. Is output to the color difference signal changing unit 15.
If the color gain g calculated by the color gain calculating unit 13 is output to the color difference signal changing unit 15 as it is, the user may feel uncomfortable with the saturation of the video. However, by providing the limiter 14a, the saturation of the original video is provided. The degree can be prevented from changing greatly, and a natural image can be displayed.

The low-pass filter 14b changes the value of the input color gain g so that the difference in color gain G between adjacent frames in time series order is less than a predetermined value, and uses the changed color gain G as a color difference signal. This is a circuit for outputting to the changing unit 15.
When the color gain g calculated by the color gain calculation unit 13 is directly output to the color difference signal changing unit 15 as the color gain G, the color gain G changes abruptly in units of frames, and the user may feel uncomfortable with the video. However, when the low-pass filter 14b is provided, it is possible to prevent the color gain G from abruptly changing in units of frames, so that a natural image can be displayed.

  The scene change detection unit 16 detects a scene change, that is, a so-called scene change based on the luminance signal Y of each frame adjacent in time series order, and a detection result signal indicating the detection result is used as a color gain change unit. 14 to output. The scene change detection method is not particularly limited, and a scene change may be detected from changes in the luminance signal Y or the color difference signals Cr and Cb. Further, a change in scene may be detected in consideration of a change in sound. In addition, when the video signal includes information indicating a scene change, the scene change may be detected based on the information.

  The color gain changing unit 14 inputs the detection result signal output from the scene change detecting unit 16. When a change in scene is detected, the color gain changing unit 14 stops the operation of the limiter 14a and the low-pass filter 14b, and the color gain g output from the color gain calculating unit 13 is used as the color gain G as it is. 15 is output. Further, the color gain changing unit 14 operates the limiter 14a and the low-pass filter 14b when a change in scene is not detected.

  The color difference signal changing unit 15 receives the color difference signals Cr and Cb and the color gain G output from the color gain changing unit 14. Then, the color difference signal changing unit 15 amplifies the input color difference signals Cr and Cb with an amplification factor indicated by the color gain G, and outputs the amplified color difference signals Crout and Cbout to the display unit 2.

  On the other hand, the luminance signal changing unit 17 inputs the luminance signal Y, changes the signal level of the inputted luminance signal Y by any known adjustment method, and outputs the changed luminance signal Yout to the display unit 2. To do.

  The display unit 2 is, for example, a liquid crystal display panel, a plasma display, or an organic EL (Electro-Luminescence) display, and displays an image based on the luminance signal Yout and the color difference signals Crout and Cbout output from the signal processing device 1.

  In the signal processing device 1 and the video display device configured as described above, color saturation can be prevented, and a better image quality can be realized as compared with the signal processing device 1 considering only the luminance signal Y. can do.

(Modification 1)
FIG. 5 is a block diagram showing a video display apparatus according to the first modification.
The video display apparatus according to the modification 1 adjusts the color gain g using the saturation histogram, and makes it possible to obtain good image quality. The video display device according to the first modification has the same configuration as the signal processing device 1 and the display unit 2 according to the first embodiment. However, the difference is that a saturation histogram generation unit 112 and an APL (APL: Average. Picture Level) calculation unit 118 are provided instead of the luminance saturation histogram generation unit 12. Further, the processing contents and configurations of the color gain calculation unit 13 and the weighting coefficient LUT 113b are different. Below, the said difference is mainly demonstrated.

  The saturation histogram generation unit 112 receives the saturation signal S output from the saturation conversion unit 11, and generates a saturation frequency distribution based on the input saturation signal S of each pixel (FIG. 6). reference).

FIG. 6 is an explanatory diagram conceptually showing the frequency distribution of saturation. In the saturation frequency distribution, the signal level of the saturation signal S is divided into a plurality of saturation sections. The horizontal axis indicates the saturation level i, and the vertical axis indicates the frequency bin _i in each saturation section, that is, the number of pixels having the saturation signal S of the signal level belonging to the saturation section.
The saturation histogram generation unit 112 outputs the generated saturation frequency distribution, that is, the frequency bin _i of each saturation section to the color gain calculation unit 13.

  The APL calculation unit 118 receives the luminance signal Y and calculates an average image level based on the input luminance signal Y. The average image level is an average luminance value of one frame of video. Hereinafter, the average image level is referred to as APL. Then, the APL calculation unit 118 outputs the calculated APL to the color gain calculation unit 13.

The color gain calculation unit 13 is provided with a weighting factor LUT 113b (storage means), and the color gain calculation unit 13 performs the frequency of each saturation section output from the saturation histogram generation unit 112 and the APL calculation unit 118, respectively. While bin _i and APL are input, the weight coefficient W _i is read from the weight coefficient LUT 113b.

Figure 7 is an explanatory view conceptually showing a weighting factor W _i weighting factor LUT113b stores. The horizontal axis represents the same saturation level i and the frequency distribution of saturation, and the vertical axis shows the magnitude of the weighting factor W _i associated with each saturation section. The weight coefficient W _i is associated with each saturation section, and has a larger value as the saturation level i is smaller. This is because, in order to prevent color saturation, it is desired to decrease the value as the saturation level i increases. Although the modification 1 includes the weighting coefficient LUT 113b as shown in FIG. 7, the weighting coefficient is calculated using an arbitrary function instead of the weighting coefficient LUT 113b as in the embodiment. May be.
The color gain calculation unit 13 multiplies the input frequency bin _i of each saturation section by the corresponding weight coefficient W _i read from the weight coefficient LUT 113b, and multiplies each multiplication value W _i × bin obtained by multiplication. Add _i . The added value is represented by the following formula (3).

  In addition, the color gain calculation unit 13 includes a plurality of different gain tables 113a associated with a plurality of APL sections in order to change the color gain g according to the APL of the luminance signal Y. Each gain table 113a stores the added value and the color gain g in association with each other. Even if each gain table 113a is an addition value of the same value, the gain table 113a associated with a large APL section has a larger color gain g than the gain table 113a associated with a small APL section. Are associated with each other.

  FIG. 8 is an explanatory diagram conceptually showing the gain table 113a. The horizontal axis represents the added value, and the vertical axis represents the color gain g. As shown in FIG. 8, the color gain g has a smaller value as the added value is larger. Further, the color gain calculation unit 13 can select a gain table 113a corresponding to APL so that the larger the APL is, the larger the color gain g is calculated.

  The method for calculating the color gain g is an example, and the color gain g can be calculated using an arbitrary expression, a lookup table, or the like. Alternatively, a single gain table 113a may be provided so that the color gain g corresponding to the added value is calculated based on the gain table 113a, and the calculated color gain g is increased or decreased according to APL. good. That is, the color gain g may be increased as the APL increases.

  Moreover, although the example which increases / decreases the color gain g based on APL was demonstrated, the color gain g is based on various statistics which can evaluate the brightness | luminance of the maximum value of a brightness | luminance, an average value, and other images. You may comprise so that it may change.

The signal processing apparatus 101 and the video display apparatus according to the first modification are configured to generate a saturation frequency distribution and adjust the color gain g based on the frequency distribution and the APL. Therefore, it is possible to obtain a good image quality with lighter processing content compared to the embodiment.
Compared with the case of generating a two-dimensional frequency distribution of luminance and saturation, the memory capacity necessary for storing the frequency distribution can be suppressed, and the signal processing apparatus 101 and the video display apparatus are configured at low cost. be able to.

(Modification 2)
FIG. 9 is a block diagram illustrating a video display apparatus according to the second modification.
The video display apparatus according to the modified example 2 can adjust the color gain g using the saturation histogram without using the weighting factor LUT 13b, and obtain a good image quality. The video display device according to the second modification has the same configuration as the signal processing device 101 and the display unit 2 according to the first modification. However, the difference is that the weighting factor LUT is not provided. Further, the processing contents of the color gain calculation unit 213 are different. Below, the said difference is mainly demonstrated. The configurations of the saturation histogram generation unit 212 and the APL calculation unit 218 are the same as those of the saturation histogram generation unit 112 and the APL calculation unit 118 according to the first modification.

FIG. 10 is an explanatory diagram conceptually showing the frequency distribution of saturation and the processing contents of the color gain calculation unit 213. In the saturation frequency distribution, the signal level of the saturation signal S is divided into a plurality of saturation sections. The horizontal axis indicates the saturation level i, and the vertical axis indicates the frequency bin _i in each saturation section, that is, the number of pixels having the saturation signal S of the signal level belonging to the saturation section.

The color gain calculation unit 213 inputs the frequency bin _i of each saturation section output from the saturation histogram generation unit and the APL calculation unit 218 and the APL. Then, the color gain calculation unit 213 adds the frequency bin _i of the saturation sections that are equal to or greater than a predetermined threshold among the input saturation sections. That is, the sum of the saturation classifications equal to or greater than a predetermined threshold is calculated. The added value is represented by the following formula (4). Here, k indicates the saturation classification corresponding to the threshold value.

  In addition, the color gain calculation unit 213 includes a plurality of different gain tables 213a associated with a plurality of APL sections, as in the first modification.

  FIG. 11 is an explanatory diagram conceptually showing the gain table 213a. The horizontal axis represents the added value, and the vertical axis represents the color gain g. As shown in FIG. 11, the color gain g has a smaller value as the added value is larger. In addition, the color gain calculation unit 213 selects one gain table 213a from among a plurality of gain tables 213a corresponding to APL so that a larger color gain g is calculated as APL is larger. Can do.

  Needless to say, the method for calculating the color gain g is merely an example, as in the first modification.

  In the signal processing device 201 and the video display device according to the modified example 2, it is possible to adjust the color gain G and prevent color saturation without providing the weighting factor LUT, and obtain a good image quality.

(Modification 3)
FIG. 12 is a block diagram illustrating a video display apparatus according to the third modification. The video display device according to the modified example 3 uses the luminance signal Y as basic information for calculating the color gain g, and uses the color gain g calculated using the information of the luminance signal Y using the frequency distribution of saturation. It is comprised so that it may correct. The video display device according to the third modification has the same configuration as the signal processing device 101 and the display unit 2 according to the first modification. However, the configuration of the color gain calculation unit 313 is different. Below, the said difference is mainly demonstrated. The configuration of the saturation histogram generation unit 312 and the APL calculation unit 318 is the same as that of the saturation histogram generation unit 212 and the APL calculation unit 218 according to the second modification.

  The color gain calculation unit 313 includes a plurality of gain tables 313a in which APL and color gain g are associated with each other. The plurality of gain tables 313a are associated with each of a plurality of different added values represented by, for example, the above formula (3) or (4) in order to change the color gain g according to the saturation. When the addition value is calculated using the above equation (3), the color gain calculation unit 313 may be provided with a weighting coefficient LUT. In addition, although the addition value calculated by the said Formula (3) or (4) was illustrated as a statistic regarding the saturation which correct | amends the color gain g, it is various statistics which can evaluate the saturation of an image | video. Based on this, the color gain g may be adjusted.

  FIG. 13 is an explanatory diagram conceptually showing the gain table 313a. The horizontal axis indicates APL, and the vertical axis indicates color gain g. As shown in FIG. 13, the color gain g has a larger value as the APL is larger. In addition, the color gain calculation unit 313 calculates a larger color gain g as the saturation of the image increases by selecting the gain table 313a corresponding to the addition value represented by the above formula (3) or (4). The color gain g can be changed as described above. Needless to say, the method for calculating the color gain g is merely an example, as in the first and second modifications.

  In the signal processing device 301 and the video display device according to the modified example 3, as the basic information, the color gain g is adjusted using the luminance signal Y, and the color gain g is corrected by the saturation, thereby correcting the color gain. It is possible to adjust g and prevent color saturation and obtain good image quality.

(Modification 4)
FIG. 14 is a block diagram illustrating a video display apparatus according to Modification 4.
The video display device according to the modified example 4 can adjust the color gain g using the saturation frequency distribution and the luminance frequency distribution to obtain a good image quality. The video display device according to the modified example 4 has the same configuration as the signal processing device 1 and the display unit 2 according to the first embodiment. However, the difference is that a saturation histogram generation unit 412 and a luminance histogram generation unit 419 are provided instead of the luminance saturation histogram generation unit 12. Further, the processing contents and configuration of the color gain calculation unit 413 are different. Below, the said difference is mainly demonstrated. Note that the saturation histogram generation unit 412 has the same configuration as that of the first modification, and thus detailed description thereof is omitted.

The luminance histogram generation unit 419 receives the luminance signal Y and generates a luminance frequency distribution based on the input luminance signal Y of each pixel. In the luminance frequency distribution, the signal level of the luminance signal Y is divided into a plurality of luminance categories. Luminance histogram generation unit 419 outputs the frequency distribution of the generated luminance, i.e. the frequency bin _j of each luminance segment to the color gain calculator 413.

The color gain calculation unit 413 is provided with a weighting factor LUT 413b. The color gain calculation unit 413 includes the frequency bin _i of each saturation section output from the saturation histogram generation unit 412 and the luminance histogram generation unit 419, respectively. The frequency bin _j of each luminance section is input, and the weight coefficients W _i and W _j are read from the weight coefficient LUT 413b. Further, the weight coefficient _Wi is associated with each saturation section, and has a larger value as the saturation level i is smaller. Further, the weight coefficient W _j is associated with each luminance category, and has a larger value as the luminance level j is larger. This is because, in a bright video with a high average luminance, setting the signal levels of the color difference signals Cr and Cb high tends to be favored as a good image quality. Although the modification 4 includes the weighting factor LUT 413b, the weighting factor may be calculated using an arbitrary function instead of the weighting factor LUT 413b.
The color gain calculation unit 413 multiplies the input frequency bin _j of each luminance section by the corresponding weight coefficient W _j read from the weight coefficient LUT 413b, and multiplies each multiplication value W _j × bin _j obtained by multiplication. Is added. The added value is represented by the following formula (5).

  Further, the color gain calculation unit 413 may be configured to calculate an addition value represented by the following equation (6) instead of the above equation (5).

  The color gain calculation unit 413 includes a plurality of gain tables 413a in which the addition value expressed by the above formula (5) or (6) and the color gain g are associated with each other. The plurality of gain tables 413a are associated with each of a plurality of different added values represented by, for example, the above formula (3) or (4) in order to change the color gain g according to the saturation. In addition, although the addition value calculated by said Formula (3) or (4) was illustrated as a statistic regarding the saturation which correct | amends the color gain g, it is various statistics which can evaluate the saturation of a video | video. Based on this, the color gain g may be adjusted.

  FIG. 15 is an explanatory diagram conceptually showing the gain table 413a. The horizontal axis represents the added value represented by the above formula (5) or (6), and the vertical axis represents the color gain g. As shown in FIG. 15, the color gain g has a larger value as the added value represented by the above formula (5) or (6) is larger. Further, the color gain calculation unit 413 calculates a larger color gain g as the saturation of the video increases by selecting the gain table 413a corresponding to the addition value represented by the above formula (3) or (4). Can be done. Needless to say, the method for calculating the color gain g is merely an example, as in the first and second modifications.

  In the signal processing device 401 and the video display device according to the modified example 4, the saturation frequency distribution and the luminance frequency distribution are generated, and the color gain g is adjusted based on each frequency distribution, whereby the color Can be prevented, and good image quality can be obtained.

(Modification 5)
FIG. 16 is a block diagram illustrating a video display apparatus according to Modification 5. The video display apparatus according to the modified example 5 is realized by causing the computer 3 to execute the computer program 4a according to the present invention.

  The computer 3 includes a CPU (Central Processing Unit) 31 that controls the entire apparatus. The CPU 31 includes a ROM (Read Only Memory) 32, a RAM (Random Access Memory) 33 that stores temporary information generated in accordance with the calculation, and a recording medium that records the computer program 4a according to the embodiment of the present invention. 4. For example, an external storage device 34 that reads a computer program 4a from a CD-ROM and an internal storage device 35 such as a hard disk that records the computer program 4a read by the external storage device 34 are connected. The CPU 31 implements the signal processing method according to the present invention by reading the computer program 4a from the internal storage device 35 into the RAM 33 and executing various arithmetic processes. In addition, the computer 3 includes an input unit 36 to which the luminance signal Y and the color difference signals Cr and Cb are input, and an output unit 37 that outputs the luminance signal Yout and the color difference signals Crout and Cbout after the signal processing.

  FIG. 17 is a flowchart showing the processing procedure of the CPU 31 according to the signal processing method of the present invention. The CPU 31 inputs the analog luminance signal Y and the color difference signals Cr and Cb at the input unit 36 (step S11), and AD converts the input luminance signal Y and the color difference signals Cr and Cb into digital luminance data and color difference data. (Step S12).

  Then, the CPU 31 calculates saturation data based on the color difference data (step S13). The saturation data calculation method is the same as the saturation signal S calculation method. Then, a color gain is calculated based on the luminance data and the saturation data (step S14). The color gain may be calculated by a method similar to the method described in the embodiment and the first to fourth modifications.

Next, the CPU 31 limits the upper limit so that the color gain is less than the predetermined upper limit value, and changes the color gain calculated in step S14 so that the variation of the color gain related to each frame becomes smooth (step S14). S15). The color gain can be changed by a processing method similar to that of the color gain changing unit in the embodiment.
Next, the CPU 31 changes the value of the color difference data based on the color gain changed in step S15 (step S16). The CPU 31 DA converts the luminance signal Y and the changed color difference data into analog luminance signals Y and color difference signals Cr and Cb (step S17), and outputs the DA converted luminance data and color difference data to the output unit 37. Output to the outside (step S18), and the process ends.

  In the fifth modification, the computer 3 can be used to achieve the same effects as those in the embodiment and the first to fourth modifications.

In the embodiment and the modification, an example in which the color gain is adjusted using the input original luminance signal Y and the color difference signals Cr and Cb that are not subjected to various correction processes has been described. The signal processing according to the present invention may be executed using the luminance signal Y and the color difference signals Cr and Cb after the above. Further, the signal processing according to the present invention may be executed using the luminance signal Y and the primary color difference signals Cr and Cb after arbitrary signal processing is performed. Furthermore, the signal processing according to the present invention may be executed using the original luminance signal Y and the color difference signals Cr and Cb after arbitrary signal processing is performed.
Furthermore, in this embodiment, the example in which the color gain is adjusted using the two-dimensional frequency distribution of luminance and saturation and the frequency distribution of luminance or saturation has been described. However, the luminance, the color difference signal Cr, and the color difference signal Cb A frequency distribution may be generated, and the color gain may be calculated using the frequency distribution.

  Furthermore, the video display device has been described as an application example of the signal processing circuit. However, the video playback device such as a DVD (Digital Versatile Disc) recorder or BD (Blu-ray) recorder that outputs a video signal, a mobile phone, or a car navigation device. The signal processing circuit according to the present invention may be applied to various portable devices such as PDA (Personal Data Assistance), satellite broadcasting tuners, and the like.

  The embodiment disclosed this time is to be considered as illustrative in all points and not restrictive. The scope of the present invention is defined by the terms of the claims, rather than the meanings described above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.

DESCRIPTION OF SYMBOLS 1 Signal processing apparatus 2 Display part 3 Computer 4 Recording medium 4a Computer program 11 Saturation conversion part 12 Luminance saturation histogram generation part 13 Color gain calculation part 13a Gain table 13b Weight coefficient LUT
14 Color gain changing unit 14a Limiter 14b Low pass filter 15 Color difference signal changing unit 16 Scene change detecting unit 17 Luminance signal changing unit Y Luminance signal Cr, Cb Color difference signal S Saturation signal

Claims (11)

In a signal processing apparatus for inputting a luminance signal and a color difference signal of one video and changing a signal level of the color difference signal based on the input luminance signal,
A signal processing apparatus comprising: color difference signal change amount determining means for determining a signal level change amount of a color difference signal based on each of the input luminance signal and color difference signal. The luminance signal and the color difference signal indicate the luminance and color of each of the plurality of pixels.
Saturation signal conversion means for converting the input color difference signal into a saturation signal;
Saturation histogram generation means for generating a frequency distribution of saturation based on the saturation signal converted by the saturation signal conversion means,
The color difference signal change amount determining means includes
The signal processing apparatus according to claim 1, further comprising means for determining a signal level change amount of the color difference signal based on the frequency distribution generated by the saturation histogram generation means. Storage means for storing a weighting factor that is associated with saturation and has a larger / smaller value as the saturation value is smaller / larger,
The color difference signal change amount determining means includes
Each frequency in the frequency distribution generated by the saturation histogram generating means is multiplied by a corresponding weighting coefficient, and the signal level of the color difference signal increases as the added value of each multiplied value obtained by the multiplication increases / decreases. The signal processing apparatus according to claim 2, further comprising means for determining a signal level change amount so that the signal level is changed to a higher / lower signal level. The color difference signal change amount determining means includes
By adding the frequencies equal to or higher than the predetermined saturation in the frequency distribution generated by the saturation histogram generation means, the signal level of the color difference signal is higher / lower as the added value obtained by the addition is smaller / larger. The signal processing apparatus according to claim 2, further comprising means for determining a signal level change amount so as to be changed to A luminance histogram generating means for generating a luminance frequency distribution based on the input luminance signal;
The color difference signal change amount determining means includes
5. The signal level change amount of the color difference signal is determined based on the frequency distribution generated by the luminance histogram generation unit. 5. Signal processing equipment. The luminance signal and the color difference signal indicate the luminance and color of each of the plurality of pixels.
Saturation signal conversion means for converting the input color difference signal into a saturation signal;
A luminance saturation histogram generating means for generating a luminance and saturation two-dimensional frequency distribution based on the input luminance signal and the saturation signal converted by the saturation signal conversion means;
Storage means that is associated with the luminance and the saturation, and stores a weighting factor having a larger value as the luminance value is larger or the saturation value is smaller;
Each frequency in the frequency distribution generated by the luminance / saturation histogram generation means is multiplied by a corresponding weighting coefficient, and the added value of each multiplication value obtained by multiplication is larger / smaller as the signal of the color difference signal. The signal processing apparatus according to claim 1, further comprising: a color difference signal change amount determining unit that determines a signal level change amount so that the level is changed to a higher / lower signal level. A luminance signal and a color difference signal corresponding to each of a plurality of images are input,
The image processing apparatus further comprises changing means for changing the signal level change amount so that the difference in the signal level change amount of each video determined by the color difference signal change amount determining means is less than a predetermined value. The signal processing device according to any one of claims 1 to 6. A luminance signal and a color difference signal corresponding to each of a plurality of images are input,
The apparatus further comprises changing means for changing the signal level change amount so that the signal level change amount of each video determined by the color difference signal change amount determining means is less than a predetermined value. The signal processing device according to claim 6. A scene change detecting means for detecting a change in a scene related to the video based on a luminance signal or a color difference signal of each of the plurality of videos,
The changing means is
The signal processing apparatus according to claim 7 or 8, wherein when the scene change detection unit detects a change in a scene, the change process is stopped. A signal processing device according to any one of claims 1 to 9,
A video display device comprising: a display unit that displays video based on the luminance signal and the color difference signal processed by the signal processing device. In a signal processing method of inputting a luminance signal and a color difference signal of one video and changing a signal level of the color difference signal based on the input luminance signal,
A signal processing method, comprising: determining a signal level change amount of the color difference signal based on each of the input luminance signal and color difference signal.

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