JP2006229616A - Circuit for processing video signals - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize a circuit for processing video signals for gain-adjusting an original signal independently for every RGB according to luminance, saturation level and hue range. <P>SOLUTION: This circuit for processing video signals is provided with an RGB converting circuit 11 for generating a primary color signal to be displayed at a display device based on an inputted luminance signal and a color difference signal, a saturation/hue detecting circuit 12 for detecting a saturation level and a hue range from a color difference signal, and for outputting them as saturation level data and hue range data, gain coefficient generating circuits 13 to 15 for generating gain coefficients for correcting the primary color signals based on the luminance signals, the saturation level data and hue range data and an RGB gain control circuit 16 for correcting the primary color signal by using the gain coefficients, and for outputting it to a display device. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a video signal processing circuit in a color television receiver.

  Conventionally, in order to improve the image quality of a color television receiver, a white peak blue circuit or a drive gain adjustment circuit (for example, Patent Document 1) that corrects a primary color signal (also referred to as “RGB signal”) that directly drives a display device. ) Etc. were used. The white peak blue circuit produces a bright white by increasing the gain of only the B axis of RGB and increasing the color temperature during high luminance video with low saturation. The drive gain adjustment circuit adjusts the white balance by increasing the overall color temperature.

  However, the conventional white peak blue circuit, as shown in FIG. 8, increases the gain of the B axis during high luminance video (when the input luminance level is equal to or higher than the white peak blue start point shown in FIG. 8). Therefore, there is a problem that the output level becomes brighter than the original brightness of the input signal. Further, as shown in FIG. 9, the conventional white peak blue circuit causes blooming due to excessive transfer (when the output level exceeds the limit level shown in FIG. 9) in a display device such as a CRT. In a fixed pixel type display device driven by a digital signal such as liquid crystal, PDP, or FED, there is a problem that white balance is lost when an input signal level is input beyond the input dynamic range.

Also, as shown in FIG. 10, the conventional drive gain adjustment circuit increases the overall color temperature regardless of the image, and the face of a person who is lit up by white balance adjustment becomes pale and unhealthy. There was a problem of being visible.
JP 2001-128192 A

  The present invention provides a video signal processing circuit capable of adjusting gains of primary color signals independently for each of RGB in accordance with luminance, saturation level, and hue range.

  According to one aspect of the present invention, RGB conversion means for generating a primary color signal for display on a display device based on an input luminance signal and a color difference signal, and a saturation level and a hue range are detected from the color difference signal. A saturation hue detection means for outputting these as saturation level data and hue range data, and a gain for correcting the primary color signal based on the luminance signal, the saturation level data, and the hue range data. There is provided a video signal processing circuit comprising gain coefficient creating means for generating a coefficient, and gain control means for correcting the primary color signal using the gain coefficient and outputting it to the display device.

  According to another aspect of the present invention, RGB conversion means for generating a primary color signal to be displayed on a display device based on an input luminance signal and color difference signal, and a saturation level is detected from the color difference signal. A saturation detection means for outputting this as saturation level data; a gain coefficient creation means for generating a gain coefficient for correcting the primary color signal based on the luminance signal and the saturation level data; and the gain There is provided a video signal processing circuit comprising gain control means for correcting the primary color signal using a coefficient and outputting the corrected signal to the display device.

  According to the present invention, it is possible to independently adjust the gains of the primary color signals for each of RGB in accordance with the luminance, the saturation level, and the hue range.

  Embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 is a circuit block diagram showing a video signal processing circuit according to Embodiment 1 of the present invention. Here, a portion mainly related to correction of three primary color signals (also referred to as RGB signals) is shown.

  The video signal processing circuit according to the first embodiment of the present invention includes an RGB conversion circuit 11, a saturation hue detection circuit 12, three gain coefficient generation circuits 13 to 15 (hereinafter referred to as “R gain coefficient generation circuit 13”, “ G gain coefficient creating circuit 14 ”and“ B gain coefficient creating circuit 15 ”), and an RGB gain control circuit 16.

  A luminance signal from the Y input is input to the first input of the RGB conversion circuit 11, a color difference signal from the Cb input is input to the second input, and a color difference signal from the Cr input is input to the third input. Have been entered. The first output of the RGB conversion circuit 11 is supplied as a first primary color signal (hereinafter referred to as “R signal”) to the first input of the RGB gain control circuit 16, and the second output is the second primary color signal. (Hereinafter referred to as “G signal”) to the second input of the RGB gain control circuit 16, and the third output as the third primary color signal (hereinafter referred to as “B signal”). 16 to the third input.

  A color difference signal from the Cb input is input to the first input of the saturation hue detection circuit 12, and a color difference signal from the Cr input is input to the second input. The first output of the saturation hue detection circuit 12 is supplied as saturation level data to the first inputs of the R gain coefficient generation circuit 13, the G gain coefficient generation circuit 14, and the B gain coefficient generation circuit 15, respectively. Are supplied as hue range data to the second input of each of the R gain coefficient creating circuit 13, the G gain coefficient creating circuit 14, and the B gain coefficient creating circuit 15.

  The luminance signal from the Y input is input to the third input of the R gain coefficient generation circuit 13, and the output of the R gain coefficient generation circuit 13 is supplied as the R gain coefficient to the fourth input of the RGB gain control circuit 16. Yes.

  The luminance signal from the Y input is input to the third input of the G gain coefficient generation circuit 14, and the output of the G gain coefficient generation circuit 14 is supplied as the G gain coefficient to the fifth input of the RGB gain control circuit 16. Yes.

  The luminance signal from the Y input is input to the third input of the B gain coefficient generation circuit 15, and the output of the B gain coefficient generation circuit 15 is supplied as the B gain coefficient to the sixth input of the RGB gain control circuit 16. Yes.

  The first output of the RGB gain control circuit 16 is supplied as a corrected R signal to a display device (not shown) via an R output, and the second output is supplied as a corrected G signal via a G output. The third output is supplied as a corrected B signal to the display device via the B output.

  The RGB conversion circuit 11 converts the input luminance signal (Y input) and two color difference signals (Cb input, Cr input) into three primary color signals (R signal, G signal, and B signal). The R signal is a signal for driving a red light emitting unit of the display device. Similarly, the G signal drives a green light emitting unit, and the B signal drives a blue light emitting unit.

  The saturation hue detection circuit 12 detects a saturation level and a hue range from two input color difference signals (Cb input, Cr input), and uses these as saturation level data and hue range data as gain coefficient generation circuits 13 to 13. 15 is output.

  The R gain coefficient creation circuit 13 is constant with respect to the R signal output from the RGB conversion circuit 11 based on the luminance signal from the Y input and the saturation level data and hue range data from the saturation hue detection circuit 12. An R gain coefficient for correcting input / output characteristics is generated for each range.

  The configurations, functions, and operations of the G gain coefficient generation circuit 14 and the B gain coefficient generation circuit 15 are the same as those of the R gain coefficient generation circuit 13. The difference from the R gain coefficient generation circuit 13 is that the G gain coefficient generation circuit 14 generates a G gain coefficient for correcting the G signal from the RGB conversion circuit 11, and the B gain coefficient generation circuit 15 from the RGB conversion circuit 11. The B gain coefficient for correcting the B signal is generated.

  The RGB gain control circuit 16 multiplies the R signal by the R gain coefficient, generates a desired corrected R signal, and outputs it to the display device. Further, the RGB gain control circuit 16 generates a desired corrected G signal by multiplying the G signal by the G gain coefficient, and generates a desired corrected B signal by multiplying the B signal by the B gain coefficient. To the display device.

  FIG. 2 is an input / output characteristic diagram showing correction in the video signal processing circuit according to the first embodiment of the present invention. The horizontal axis in FIG. 2 indicates the input level, and the vertical axis indicates the output level. The thin broken line shows the input / output characteristics of the B axis when the conventional white peak blue circuit is used, and the thick solid line shows the input / output characteristics of the B axis corrected by the video signal processing circuit according to the first embodiment of the present invention. ing. The thin two-dot chain line indicates the input / output characteristics of the R axis and the G axis when the conventional white peak blue circuit is used, and the thick one-dot chain line is corrected by the video signal processing circuit according to the first embodiment of the present invention. The input / output characteristics of the R axis and G axis are shown. The point S shown in FIG. 2 represents the input level at which the conventional white peak blue circuit starts to operate.

  In the correction in the video signal processing circuit according to the first embodiment of the present invention, the R signal, the G signal, and the B signal are adjusted independently. For this reason, for example, as shown in FIG. 2, the input / output characteristics are set to a desired shape so as to enhance white without changing the overall brightness or to prevent the white balance from being lost due to the limit level. Can do.

  (A) and (B) shown in FIG. 2 represent regions having different gain coefficients. That is, at the higher input level (B), the gain coefficient is gradually lowered as compared with (A) to suppress the white balance from being lost due to the limit level.

  Next, specific examples of the three gain coefficients (R / G / B) will be described. FIG. 3 is an image diagram showing gain coefficients of the video signal processing circuit according to the first embodiment of the present invention. The horizontal axis in FIG. 3 indicates the input luminance level, and the vertical axis indicates the gain coefficient for correcting them. A thick solid line indicates a B gain coefficient for correcting the B axis, and a thick one-dot chain line indicates a G gain coefficient and an R gain coefficient for correcting the G axis and the R axis. Also, the point S shown in FIG. 3 represents the input luminance level at which the conventional white peak blue circuit starts to operate.

  As for the gain coefficient of the video signal processing circuit according to the first embodiment of the present invention, for example, as shown in FIG. 3, the B gain coefficient is increased above the S point and the R gain coefficient and the G gain coefficient are simultaneously decreased. This emphasizes white while maintaining the overall brightness.

  Further, in the region (B) where the input luminance level is high, the above-described white balance problem is improved by gradually lowering each gain coefficient from (A).

  Next, a gain coefficient when displaying skin color will be described as another specific example. FIG. 4 is another image diagram showing the gain coefficient of the video signal processing circuit according to the first embodiment of the present invention. The horizontal axis in FIG. 4 indicates the input hue, and the vertical axis indicates the gain coefficient for correcting them. A thick solid line indicates an R gain coefficient for correcting the R axis, a thick broken line indicates a G gain coefficient for correcting the G axis, and a thick dotted line indicates a B gain coefficient for correcting the B axis.

  As shown in FIG. 4, the gain coefficient in the video signal processing circuit according to the first embodiment of the present invention for displaying skin color is increased by increasing the R gain coefficient in the hue range near the skin color and simultaneously decreasing the B gain coefficient. Yes. In this way, even when the white balance is adjusted, the human face is prevented from appearing pale and unhealthy.

  Next, as an example of the gain coefficient creation circuits 13 to 15, a case where desired template data is stored in the RAM and read out to create a gain coefficient will be described. FIG. 5 is a conceptual diagram showing details of the gain coefficient generation circuit in the video signal processing circuit according to the first embodiment of the present invention.

  The gain coefficient generation circuit in the video signal processing circuit according to the first embodiment of the present invention includes a RAM 51 in which template data is stored. The template data stored in the RAM 51 is table data in which desired R gain coefficient, G gain coefficient, and B gain coefficient are arranged for each luminance level, hue range, and saturation level.

  In the RAM 51, template data is stored with its brightness level, hue range, and saturation level as address data. Therefore, by accessing the RAM 51 based on the luminance level, the hue range, and the saturation level, the gain coefficient creation circuits 13 to 15 can easily generate a desired gain coefficient.

  Further, since the template data can be easily rewritten, the gain coefficient creation circuits 13 to 15 can be configured to generate a gain coefficient suitable for the image quality mode (for example, a movie mode).

  FIG. 6 is a circuit block diagram showing template data creation in the video signal processing circuit according to the first embodiment of the present invention. Here, the part of extracting the histogram of the image signal in one frame period and creating the template data based on this is shown.

  Template data creation in the video signal processing circuit according to the first embodiment of the present invention includes a frame memory 61, a histogram detection circuit 62, a CPU 63, and an RGB correction circuit 64.

  The luminance signal from the Y input is input to the first input of the frame memory 61, the color difference signal from the Cb input is input to the second input, and the color difference signal from the Cr input is input to the third input. Has been. The first output of the frame memory 61 is supplied as a delayed luminance signal to the first input of the RGB correction circuit 64, and the second output is the second output of the RGB correction circuit 64 as the delayed first color difference signal. The third output is supplied to the input of the RGB correction circuit 64 as a delayed second color difference signal.

  The luminance signal from the Y input is input to the first input of the histogram detection circuit 62, the color difference signal from the Cb input is input to the second input, and the color difference signal from the Cr input is input to the third input. The input and the output are supplied to the CPU 63.

  The output of the CPU 63 is supplied as template data to the fourth input of the RGB correction circuit 64.

  The first output of the RGB correction circuit 64 is supplied as a corrected R signal to a display device (not shown) via an R output, and the second output is supplied as a corrected G signal via a G output. The third output is supplied to the display device via the B output as a corrected B signal.

  The frame memory 61 temporarily stores input image data for one frame (luminance signal and two color difference signals). The histogram detection circuit 62 detects a histogram such as a luminance signal level for each frame from the input image data, and outputs this to the CPU 63 as histogram data. The CUP 63 computes histogram data and generates template data that is optimal for the frame. The generated template data is supplied to the RGB correction circuit 64. The RGB correction circuit 64 has the configuration shown in FIG. 1, and the gain coefficient creation circuits 13 to 15 have the RAM 51 shown in FIG. Template data from the CPU 63 is stored in the RAM 51 and used as a gain coefficient of the frame.

  Thus, by generating histogram data for each frame, the video signal processing circuit according to the first embodiment of the present invention performs optimal RGB correction for each frame.

  According to the first embodiment, the primary color signal is gain-adjusted independently for each of RGB in accordance with the luminance, saturation level, and hue range, so that a video signal processing circuit having desired input / output characteristics can be realized. .

  Therefore, according to the first embodiment, when the input signal is brighter than the original brightness of the input signal, which is a problem in the conventional white peak blue circuit or white balance adjustment circuit, the input signal exceeds the limit level. It is easy to improve things such as crumbles and people's faces appear unhealthy.

  Further, according to the first embodiment, since the gain coefficient is performed for each frame based on the detection of the histogram of the image data, appropriate RGB correction suitable for the image data can be performed. Furthermore, according to the first embodiment, since the gain coefficient can be easily rewritten as template data, RGB correction with a high degree of freedom suitable for the image quality mode can be performed.

  FIG. 7 is a circuit block diagram showing a video signal processing circuit according to Embodiment 2 of the present invention. Here, the part mainly related to the correction of the three primary color signals is shown.

  The video signal processing circuit according to the second embodiment of the present invention includes an RGB conversion circuit 71, a saturation detection circuit 72, three gain coefficient creation circuits 73 to 75 (hereinafter referred to as “R gain coefficient creation circuit 73”, “G Gain coefficient generation circuit 74 "and" B gain coefficient generation circuit 75 "), and an RGB gain control circuit 76.

  A luminance signal from the Y input is input to the first input of the RGB conversion circuit 71, a color difference signal from the Cb input is input to the second input, and a color difference signal from the Cr input is input to the third input. The first output of the RGB conversion circuit 71 is supplied to the first input of the RGB gain control circuit 76 as the first primary color signal (hereinafter referred to as “R signal”), and the second output is the second output. Are supplied to the second input of the RGB gain control circuit 76 as a primary color signal (hereinafter referred to as “G signal”), and the third output is RGB as a third primary color signal (hereinafter referred to as “B signal”). This is supplied to the third input of the gain control circuit 76.

  The color difference signal from the Cb input is input to the first input of the saturation detection circuit 72, the color difference signal from the Cr input is input to the second input, and the output of the saturation detection circuit 72 is the saturation level data. Are respectively supplied to the first input of the R gain coefficient generating circuit 73, the G gain coefficient generating circuit 74, and the B gain coefficient generating circuit 75.

  The luminance signal from the Y input is input to the second input of the R gain coefficient generation circuit 73, and the output of the R gain coefficient generation circuit 73 is supplied as the R gain coefficient to the fourth input of the RGB gain control circuit 76. Yes.

  The luminance signal from the Y input is input to the second input of the G gain coefficient generation circuit 74, and the output of the G gain coefficient generation circuit 74 is supplied as the G gain coefficient to the fifth input of the RGB gain control circuit 76. Yes.

  The luminance signal from the Y input is input to the second input of the B gain coefficient generation circuit 75, and the output of the B gain coefficient generation circuit 75 is supplied to the sixth input of the RGB gain control circuit 76 as the B gain coefficient. Yes.

  A first output of the RGB gain control circuit 76 is supplied as a corrected R signal to a display device (not shown) via an R output, and a second output is supplied as a corrected G signal via a G output. The third output is supplied as a corrected B signal to the display device via the B output.

  The configurations, functions, and operations of the RGB conversion circuit 71 and the RGB gain control circuit 76 are the same as those in the first embodiment, and a description thereof will be omitted.

  The saturation detection circuit 72 detects a saturation level from two input color difference signals (Cb input and Cr input), and outputs this to the gain coefficient creation circuits 73 to 75 as saturation level data.

  The R gain coefficient creation circuit 73 is configured to input / output characteristics for each fixed range with respect to the R signal output from the RGB conversion circuit 71 based on the luminance signal from the Y input and the saturation level data from the saturation detection circuit 72. An R gain coefficient for correcting is generated.

  The configurations, functions, and operations of the G gain coefficient generation circuit 74 and the B gain coefficient generation circuit 75 are the same as those of the R gain coefficient generation circuit 73. The difference from the R gain coefficient generation circuit 73 is that the G gain coefficient generation circuit 74 generates a G gain coefficient for correcting the G signal from the RGB conversion circuit 71, and the B gain coefficient generation circuit 75 from the RGB conversion circuit 71. The B gain coefficient for correcting the B signal is generated.

  In the second embodiment, as described above, since the hue range data is not used for generating the gain coefficient, it is impossible to perform RGB correction with a high degree of freedom as in the first embodiment. However, the configuration of the gain coefficient circuit, the RGB gain control circuit 76, and the like can be simplified accordingly.

  According to the second embodiment, the primary color signal is gain-adjusted independently for each of RGB in accordance with the luminance and saturation level, so that a video signal processing circuit having desired input / output characteristics can be realized with a simple circuit configuration. Can do.

  Therefore, according to the second embodiment, when the input signal is brighter than the original brightness of the input signal, which is a problem in the conventional white peak blue circuit or white balance adjustment circuit, the input signal exceeds the limit level. Can be easily improved.

1 is a circuit block diagram showing a video signal processing circuit according to Embodiment 1 of the present invention. FIG. 3 is an input / output characteristic diagram illustrating correction in the video signal processing circuit according to the first embodiment of the invention. FIG. 3 is an image diagram showing a gain coefficient of the video signal processing circuit according to the first embodiment of the invention. FIG. 6 is another image diagram showing a gain coefficient of the video signal processing circuit according to the first embodiment of the present invention. FIG. 3 is an image diagram illustrating details of a gain coefficient generation circuit in the video signal processing circuit according to the first embodiment of the present invention. FIG. 3 is a circuit block diagram showing template data creation in the video signal processing circuit according to the first embodiment of the present invention. FIG. 6 is a circuit block diagram showing a video signal processing circuit according to Embodiment 2 of the present invention. The luminance characteristic figure which shows the conventional white peak blue correction | amendment. The input-output characteristic figure which shows the conventional white peak blue correction | amendment. The input / output characteristic diagram showing a conventional white balance adjustment method.

Explanation of symbols

11, 71 RGB conversion circuit 12 Saturation hue detection circuit 13, 73 R gain coefficient creation circuit 14, 74 G gain coefficient creation circuit 15, 75 B gain coefficient creation circuit 16, 76 RGB gain control circuit 72 Saturation detection circuit

Claims (5)

RGB conversion means for generating a primary color signal to be displayed on the display device based on the input luminance signal and color difference signal;
Saturation hue detection means for detecting a saturation level and a hue range from the color difference signal and outputting them as saturation level data and hue range data;
Gain coefficient creating means for generating a gain coefficient for correcting the primary color signal based on the luminance signal, the saturation level data, and the hue range data;
A video signal processing circuit comprising: gain control means for correcting the primary color signal using the gain coefficient and outputting the signal to the display device. RGB conversion means for generating a primary color signal to be displayed on the display device based on the input luminance signal and color difference signal;
Saturation detection means for detecting a saturation level from the color difference signal and outputting it as saturation level data;
Gain coefficient creating means for generating a gain coefficient for correcting the primary color signal based on the luminance signal and the saturation level data;
A video signal processing circuit comprising: gain control means for correcting the primary color signal using the gain coefficient and outputting the signal to the display device. The RGB conversion means generates the three primary color signals corresponding to red (R), green (G), and blue (B),
3. The video signal processing according to claim 1, wherein the gain coefficient creating unit generates the three gain coefficients corresponding to the three primary color signals in order to independently correct the three primary color signals. 4. circuit.   The gain coefficient creating means includes storage means for storing the gain coefficient at the input level at an address specified based on the luminance signal, the saturation level data, and the hue range data. The video signal processing circuit according to claim 1. In order to evaluate the image quality of the input video signal, histogram detection means for generating a histogram relating to the input level of the luminance signal and the color difference signal at a predetermined time;
In order to correct the primary color signal in accordance with the image quality evaluation of the video signal in the histogram detection means, the gain coefficient stored in the storage means is calculated for each input level based on the histogram, and these are calculated. 5. The video signal processing circuit according to claim 4, further comprising arithmetic means for storing in the storage means.

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