Contour correction processing device and contour correction processing method

Description

[Technical field]

[0001] The present invention relates to an apparatus and method for correcting contours of video images captured by a television camera or the like. [Background technology]

[0002] In recent years, 4K television cameras with four times the number of pixels (3840 x 2160) of conventional HD (High Definition: 1920 x 1080) have become widespread, and the resolution of images has improved. On the other hand, depending on the situation, parts of the image that are incompatible with high definition, such as wrinkles and blemishes on a person's skin, are also emphasized more. Therefore, a contour correction technology called Skin Tone Detail, which blurs the contours of only specific color components such as skin color, is becoming important.

[0003] Regarding this contour correction technology, for example, Patent Document 1 discloses a contour correction circuit that uses a volume to continuously switch between a circuit that extracts contours from an input video signal and adds them to the video signal to emphasize the contours, and a circuit that adds a signal of the opposite polarity to the extracted contours to the video signal to soften the contours.

[0004] The contour correction circuit disclosed in Patent Document 1 is an analog circuit, but FIG. 8 is a block diagram showing an equivalent configuration of the contour correction circuit as a digital circuit. In Fig. 8, a contour extraction circuit consisting of a delay line, operational amplifiers, etc. is represented by a high-pass filter (HPF) 1, and the extracted contour components are increased or decreased according to the detail gain by a multiplier 2. Then, when the detail gain is a positive number, in other words, contours are emphasized, the + side is selected by a selector (SEL) 4, and when the detail gain is a negative number, in other words, contours are softened, the - side is selected by the selector (SEL) 4 via a polarity inverter 3. Finally, the output of the selector (SEL) 4 is added to the video signal by an adder 5, completing the contour correction process. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Publication No. 8-294020 Summary of the Invention [Problem to be solved by the invention]

[0006] In the contour correction circuit shown in Fig. 8, contour emphasis and softening are performed in one contour extraction circuit, so when contour extraction is performed in the vicinity of several tens of MHz, which is the frequency band for normal contour emphasis, the softening is insufficient. For example, when taking a zoomed-in photograph of a person, the spacing between wrinkles on the skin widens and the size of spots increases, resulting in issues such as wrinkles and spots not being sufficiently faded.

[0007] An object of the present invention is to provide a contour correction technique that can sufficiently soften wrinkles and blemishes on the skin even during zoom-in photography. [Means for solving the problem]

[0008] Therefore, one of the contour correction processing devices according to the present invention is provided with a first high-pass filter having a function of emphasizing the contour parts of a video signal, and one or more second high-pass filters having a function of weakening the contour parts of the video signal, and switches between the first high-pass filter and the second high-pass filter for an input video signal. When the correction gain for the video signal is zero or positive, a first high-pass filter is connected, and when the correction gain is negative, a second high-pass filter is connected. By connecting this, the contour portion of a specific color component of the input video signal is corrected. Effect of the Invention

[0009] As described above, according to the present invention, a sufficient softening effect can be obtained when the detail gain is negative, and further, the shock when the detail gain switches from a positive number to a negative number can be mitigated, and the effect of gradually softening contours can be obtained according to the absolute value of the negative detail gain. Problems, configurations and effects other than those described above will become apparent from the following description of the preferred embodiment of the invention. [Brief description of the drawings]

[0010] [Figure 1] 1 is a diagram showing an example of a block configuration of a contour correction processing device according to the present invention; [Diagram 2] 1 is a diagram illustrating the frequency characteristics and square wave response characteristics of five high-pass filters HPF and HPF_A to HPF_D used in the contour correction processing device. [Diagram 3] 4A and 4B are diagrams illustrating the frequency characteristics and square wave response characteristics of a high-pass filter HPF. [Figure 4] 4A and 4B are diagrams illustrating the frequency characteristics and square wave response characteristics of a high-pass filter HPF_A. [Diagram 5] 11A and 11B are diagrams illustrating the frequency characteristics and square wave response characteristics of a high-pass filter HPF_B. [Figure 6] 4A and 4B are diagrams illustrating the frequency characteristics and square wave response characteristics of the high-pass filter HPF_C. [Figure 7] 11A and 11B are diagrams illustrating the frequency characteristics and square wave response characteristics of a high-pass filter HPF_D. [Figure 8] FIG. 1 is a diagram showing an example of a block configuration of a contour correction processing device in the prior art. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] Hereinafter, examples of the present invention will be described with reference to the drawings as modes for carrying out the present invention, however, the present invention is not limited to these examples. EXAMPLES

[0012] FIG. 1 is a block diagram showing an example of the configuration of a contour correction processing device according to the present invention. The contour correction processing device according to the present invention can be applied as an input signal to both a video signal during recording and a video signal during playback.

[0013] 1 extracts contours from an input video signal using high-pass filters HPF1 and HPF_A to D (6-1 to 6-4). The number of high-pass filters HPF (hereinafter simply referred to as "HPF") used here is an appropriate combination of two or more filters, and is not limited to five.

[0014] First, the frequency characteristics and square wave response characteristics of each of the above-mentioned five HPFs will be described. 2 to 7 are diagrams showing the frequency characteristics and square wave response characteristics of HPF1 and HPF_A to D (6-1 to 6-4). Among them, FIG. 2 shows the frequency characteristics and square wave response characteristics of HPF1 and HPF_A to D (6-1 to 6-4) together for comparison. In addition, for the square wave response characteristics shown in FIG. 2 to FIG. 7, the input is indicated by a dashed line (all square wave inputs) and the output is indicated by a solid line.

[0015] Here, HPF1 and HPF_A to D (6-1 to 6-4) are set in order of lowest filter cutoff frequency (fc), i.e., in order of greatest softening effect (effect of blurring edges), as follows: HPF_D (6-4)>HPF_C (6-3)>HPF_B (6-2)>HPF_A (6-1)>HPF1.

[0016] FIG. 3 is a diagram showing the frequency characteristics and square wave response characteristics of the HPF1. In terms of frequency characteristics, HPF1 has the highest cutoff frequency (fc) of the five, and in its square wave response characteristics (detail gain set to maximum value), it produces an output with a steep change response (strengthening the contours).

[0017] 4 to 7 are diagrams showing the frequency characteristics and square wave response characteristics of each of HPF_A (6-1) to HPF_D (6-4). In terms of frequency characteristics, the cutoff frequencies (fc_A to fc_D) decrease in the order of HPF_A (6-1) to HPF_D (6-4). In addition, in the square wave response characteristics, the change response becomes more gradual in the order of HPF_A (6-1) to HPF_D (6-4) (detail gains are set to the minimum values ​​of the corresponding gain ranges), and the soft effect (effect of blurring edges) becomes greater.

[0018] Returning to the block configuration shown in FIG. 1, one of the outputs of HPF1 or HPF_A to D (6-1 to 4) is selected according to the detail gain. For example, the variable range of the detail gain is set to -128 to +127. However, the variable range is not limited to this range and can be set appropriately.

[0019] Next, the selectors (SEL) 4 and 7 are operated according to the value of the detail gain, for example, as follows to select HPF1 and HPF_A to D (6-1 to 4). Here, the following selection examples based on the value of the detail gain (the interval width of the detail gain) are merely examples, and the present invention is not limited to these.

[0020] (1) When Detail Gain is 0 to +127 The output of HPF 1 is multiplied by the detail gain in multiplier 2, and since the detail gain is a positive value greater than or equal to 0, the selector (SEL) 4 selects the + side. As a result, the output from the selector (SEL) 4 is the product of the output from the HPF 1 and the detail gain.

[0021] (2) When detail gain is -32 to -1 Depending on the value and sign of the detail gain, the selector (SEL) 7 selects the output of HPF_A (6-1), and the selector (SEL) 4 selects the negative side. As a result, the output of HPF_A (6-1) is multiplied by the detail gain in the multiplier 8 and output from the selector (SEL) 4 via the polarity inverter 3.

[0022] (3) When detail gain is -64 to -33 Depending on the value and sign of the detail gain, the selector (SEL) 7 selects the output of HPF_B (6-2), and the selector (SEL) 4 selects the negative side. As a result, the output of the HPF_B ( 6 - 2 ) is multiplied by the detail gain in the multiplier 8 , and is output from the selector (SEL) 4 via the polarity inverter 3 .

[0023] (4) When detail gain is -96 to -65 Depending on the value and sign of the detail gain, the selector (SEL) 7 selects the output of HPF_C (6-3), and the selector (SEL) 4 selects the negative side. As a result, the output of the HPF_C ( 6 - 3 ) is multiplied by the detail gain in the multiplier 8 , and is output from the selector (SEL) 4 via the polarity inverter 3 .

[0024] (5) When detail gain is -128 to -97 Depending on the value and sign of the detail gain, the selector (SEL) 7 selects the output of HPF_D (6-4), and the selector (SEL) 4 selects the negative side. As a result, the output of the HPF_D ( 6 - 4 ) is multiplied by the detail gain in the multiplier 8 , and is output from the selector (SEL) 4 via the polarity inverter 3 .

[0025] Finally, the output of the selector (SEL) 4 is added to the original video signal by the adder 5, thereby completing the contour correction process.

[0026] In the contour correction process of the present invention, in order to prevent the image from suddenly becoming too soft and creating an unnatural feeling when the detail gain switches from a positive number to a negative number, multiple HPFs with different frequency characteristics and square wave response characteristics are provided, and the frequency band is gradually switched from high frequencies to low frequencies as the absolute value of the negative number of the detail gain becomes larger.

[0027] By carrying out the above-mentioned contour correction process, for example, it is possible to effectively weaken contours such as wrinkles and blemishes on a person's skin, and it is also possible to lighten dark colors themselves. Conversely, by making a correction so as to emphasize the contour portion, it is possible to apply the correction to, for example, emphasize wrinkles corresponding to an aged character.

[0028] As described above, for example, by using a television camera equipped with the contour correction processing device of the present invention, it is possible to transmit the image captured by the camera as processed image that has been subjected to contour correction processing, even during real-time broadcasting such as live broadcasting.

[0029] Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications are possible without departing from the gist of the present invention. [Explanation of symbols]

[0030] 1, 6-1, 6-2, 6-3, 6-4: High-pass filter (HPF), 2, 8: Multiplier, 3: Polarity inverter, 4, 7: Selector (SEL), 5: Adder

Claims

1. a first high-pass filter having a function of emphasizing contour portions of a video signal; one or more second high-pass filters having a function of weakening contour portions of the video signal; Established The first high-pass filter and the second high-pass filter are switched for an input video signal, and when a correction gain for the video signal is zero or positive, the first high-pass filter is connected, and when the correction gain is negative, the second high-pass filter is connected, thereby correcting a contour portion of a specific color component of the input video signal.

4. A contour correction processing device comprising:

2. 2. The contour correction processing device according to claim 1, The second high-pass filter is a plurality of filters, each having a different cutoff frequency, When the correction gain is negative and has a large absolute value, the second high-pass filter is switched to a filter having a lower cutoff frequency in order to further weaken the contour portion.

4. A contour correction processing device comprising:

3. 3. The contour correction processing device according to claim 1, The specific color component is a component that indicates the skin color of a person.

4. A contour correction processing device comprising:

4. When a correction gain for a video signal is zero or positive, the input video signal is output through a high-pass filter having a function of emphasizing contour portions of the video signal; When the correction gain is negative, the input video signal is output through one of a plurality of second high-pass filters having a function of weakening contour portions of the video signal, the second high-pass filter being selected in accordance with the magnitude of the absolute value of the correction gain. A contour correction processing method comprising the steps of: correcting a contour portion of a specific color component of the input video signal.

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