JP2001218170A - Scan conversion circuit - Google Patents

Abstract

(57) [Problem] To prevent an oblique line from appearing unnatural when a moving image is displayed by a video signal after scan conversion processing. SOLUTION: In a scan conversion circuit for interpolating a video signal of an interpolation scanning line from an input video signal Vi and outputting a video signal Vp of twice the scanning line, a scanning conversion circuit centering on an interpolation point of the interpolation scanning line based on the signal Vi. A directionality detection unit 50 for detecting a direction having the highest correlation from a plurality of (for example, three) directions including a vertical direction and an oblique direction, and a detection direction among a plurality of sample points of an upper scanning line and a lower scanning line. And an average value calculating unit 56 for calculating an average value of the video signals of the two sample points corresponding to.
Calculates the brightness level difference of the video signal between the sample points of the upper scan line and the lower scan line located in multiple directions with the interpolation point of the interpolation scan line as the center, obtains the absolute value, compares the absolute value, and compares the correlation. Detect the strongest direction.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to scanning by interpolating video signals of interpolation scanning lines from input video signals (for example, video signals for interlaced scanning) of scanning lines adjacent above and below the interpolation scanning lines. The present invention relates to a scan conversion circuit that outputs a video signal whose line is doubled (for example, a video signal for progressive scanning). For example, in a digital video signal processing in a display device using a PDP (plasma display panel) or an LCD (liquid crystal display) panel as a display panel, when a video signal for interlaced scanning is converted into a video signal for progressive scanning, Used.

[0002]

2. Description of the Related Art Conventionally, this type of scan conversion circuit has a 262H delay unit 12, a 1H delay unit 14,
The 62H delay unit 16, adders 18, 20, coefficient unit 22, variable coefficient units 24, 26, motion detection unit 28, and double speed conversion unit 36 were included.

[0003] The motion detecting section 28 receives a video signal Vi (for example, NTSC) for interlaced scanning input to the input terminal 10.
Video signal Vi), and the video signal Vi is supplied to the 262H delay unit 12, the 1H delay unit 14, and the 262H delay unit 16 for 52
The motion of the image is detected based on the signal delayed by 5H (1H represents one line, and the delay of 525H is equivalent to the delay of one frame). Specifically, a motion detection signal (1-K) and K are output, where K = 0 for a moving image and K = 1 for a still image.

The adder 18 adds the output signals of the 262H delay unit 12 and the 1H delay unit 14, and the coefficient unit 22 adds
Is multiplied by a factor of 1/2. Therefore, the coefficient unit 2
Reference numeral 2 outputs a video signal (a video signal of a field interpolation process) obtained by averaging the video signals of the vertically adjacent scanning lines.
One coefficient unit 24 multiplies the detection signal K of the motion detection unit 28 by the video signal (video signal of the field interpolation processing) delayed by one field in the 262H delay unit 16 and adjusted in timing by the D delay unit 35. Output and the other coefficient unit 26
Multiplies the output signal of the coefficient unit 22 by the detection signal (1-K) of the motion detection unit 28 and outputs the result. The adder 20 has a coefficient unit 2
4 and the output signal of the coefficient unit 26 are added to obtain an interpolated scanning line video signal.

For this reason, in the case of a moving image, K = 0, so that the coefficients of the coefficient units 24 and 26 become 0 and 1, and only the video signal obtained by averaging the video signals of the vertically adjacent scanning lines is output from the adder 20. However, since K = 1 when the image is a still image, the coefficients of the coefficient units 24 and 26 become 1 and 0, which are the opposite, and only the video signal one field before is output from the adder 20. For example, in the case of a moving image, the video signal at the interpolation point Np of the interpolation scanning line is, as shown by the solid line in FIG. 8, sample points Sp and Sp located vertically in the scanning line adjacent above and below the current field (n). In the case of a still image, the video signal of the corresponding sample point Sp in the field (n) one field before is obtained as shown by a dotted line in FIG.

The double speed converter 36 converts the video signal Vi into 262
The signal delayed by 263H by the H delay unit 12 and the 1H delay unit 14 and the output signal of the adder 20 are output after being subjected to double-speed conversion processing for reading out with a clock twice as fast as writing to the memory. The terminal 38 outputs a video signal Vp for progressive scanning. The double-speed conversion unit 36 includes, but is not limited to, a first memory (for example, a line memory) capable of storing the video signal output from the 1H delay unit 14, and an image of the interpolation scanning line output from the adder 20. A second memory (for example, a line memory) capable of storing signals, and alternately reading out each line with a clock twice as fast as writing to the first and second memories,
From the output terminal 38, the video signal Vp for progressive scanning
Is output.

[0007]

However, the conventional scan conversion circuit shown in FIG. 7 has a problem that oblique lines in a moving image look unnatural. For example, when a diagonal line 40 having a line width of 2 dots is displayed in a moving image as shown in FIG. 9, two interpolation points Np1 and Np2 included in the diagonal line 40 of the interpolation scanning line are set to the upper side. Scan line sample point S
pb, Spc and sample points Spe, Spf of the lower scanning line
Is a signal obtained by averaging the video signals of the above, so that the lighting state (white) is desirable, but the half-lighting state (gray between white and black) is obtained, and the two interpolation points Np3 and Np4 on both sides are the same. However, although a non-lighting state (black) is desirable, a half-lighting state is obtained, and there is a problem that the image looks unnatural.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-described problems, and when a moving image is displayed using a video signal after a scan conversion process (eg, a video signal for progressive scanning), vertical lines and oblique lines in the moving image are displayed. An object of the present invention is to provide a scan conversion circuit capable of preventing a line from looking unnatural and reproducing a high-quality image.

[0009]

According to a first aspect of the present invention, a video signal of an interpolation scanning line is interpolated from an input video signal of a scanning line adjacent above and below the interpolation scanning line to double the scanning line. In a scan conversion circuit that outputs a video signal, based on input video signals of a plurality of sample points of an upper scan line and a lower scan line, a plurality of scan conversion circuits including a vertical direction and an oblique direction centered on an interpolation point of an interpolation scan line. A direction detection unit for detecting a direction having the highest correlation from the directions, and two sample points corresponding to the detection direction of the direction detection unit among a plurality of sample points of the upper scanning line and the lower scanning line. An average value calculator for calculating an average value of the video signals of the plurality of sample points of the upper scanning line and the lower scanning line. Based on the vertical direction around the interpolation point of the interpolation scanning line and Subtraction unit for calculating a luminance level difference between sample points of an upper scanning line and a lower scanning line in a plurality of directions including a first direction, and a first absolute value calculation for calculating an absolute value of the luminance level difference obtained by the first subtraction unit And a first comparison and detection unit that compares a plurality of absolute values obtained by the first absolute value calculation unit and detects a direction having the strongest correlation. In such a configuration, in the direction detection unit, the first subtraction unit obtains a luminance level difference between sample points of the upper scanning line and the lower scanning line in a plurality of directions around the interpolation point of the interpolation scanning line, The absolute value is obtained by the first absolute value calculation unit, and the direction having the strongest correlation is detected by comparing the plurality of absolute values by the first comparison detection unit. If the direction detection unit determines that the correlation in the oblique direction is the strongest, the average value calculation unit determines two corresponding sample points in the oblique direction among the plurality of sample points of the upper scan line and the lower scan line. Since the average value of the video signals is calculated and processed as the video signal of the interpolation scanning line, it is possible to perform the optimal interpolation processing on the oblique lines in the moving image. Further, when the direction detection unit determines that the correlation in the vertical direction is the strongest, the average value calculation unit determines the corresponding two out of a plurality of sample points of the upper scanning line and the lower scanning line.
Since the average value of the video signals at the sample points is calculated and processed as the video signal of the interpolated scanning line, it is possible to perform the optimal interpolation processing on the vertical line in the moving image.

A second aspect of the present invention is the first aspect of the present invention, wherein the first interpolation is performed so that the right and left diagonal lines around the vertical line in the moving image can be appropriately interpolated. Based on the video signals of the upper scanning line and the lower scanning line, the subtracting unit performs a (2n + 1) direction (n is an integer of 1 or more) including a vertical direction centering on the interpolation point of the interpolation scanning line and a left and right diagonal direction. ) Is composed of (2n + 1) subtractors for calculating the luminance level difference between the sample points of the upper scanning line and the lower scanning line, and the first absolute value calculating section calculates the luminance obtained by each of the (2n + 1) subtractors. Find the absolute value of the level difference (2n +
1) It is composed of absolute value calculators, and the first comparison and detection unit is (2)
(2n +) calculated by each of the (n + 1) absolute value calculators.
1) The absolute values are compared to detect the direction having the strongest correlation, and the average value calculation unit calculates (2n +) of the upper scanning line and the lower scanning line.
1) The average value of the video signals of two sample points corresponding to the detection direction of the first comparison detection unit among the sample points is configured to be calculated.

According to a third aspect of the present invention, in the second aspect of the present invention, the difference in luminance level between the sample points of the upper scan line and the lower scan line in the (2n + 1) direction centering on the interpolation point of the interpolation scan line is small. In order to prevent sometimes inappropriate interpolation processing from being performed, each absolute value calculator determines between the (2n + 1) absolute value calculators of the first absolute value calculator and the first comparison detector. The absolute value is multiplied by a factor of 1 / m (m is an integer equal to or greater than 1), and a first coefficient unit to be output to the first comparison and detection unit is inserted.

According to a fourth aspect of the present invention, in the third aspect of the invention, when the absolute value of the luminance level difference between the sample points of the upper scanning line and the lower scanning line in the (2n + 1) direction is substantially the same, In order to give priority to the interpolation processing by the sample points, the vertical axis which subtracts the set value from the output signal corresponding to the vertical direction among the (2n + 1) output signals of the first coefficient section and outputs the result to the first comparison detection section A subtractor for priority is provided.

According to a fifth aspect of the present invention, in the second, third or fourth aspect of the present invention, a minimum value exists in the absolute value of the luminance level difference between the sample points of the upper scanning line and the lower scanning line in the (2n + 1) direction. If not, the first comparison / detection unit compares the (2n + 1) absolute values obtained by the first absolute value calculation unit in order to give priority to the vertical interpolation processing. The detection signal in one direction is output, and when there is no minimum value, the detection signal in the vertical direction is output.

According to a sixth aspect of the present invention, in the second, third or fourth aspect of the present invention, even when the absolute value of the luminance level difference between the sample points of the upper scanning line and the lower scanning line in the (2n + 1) direction is equal, In order to be able to perform
The first comparison detection unit calculates the (2n +
1) comparing the absolute values, outputting a detection signal in a corresponding one of the (2n + 1) directions when the minimum value is present, outputting a gate signal when the absolute values are equal,
At other times, a vertical detection signal is output, and a second subtraction unit for calculating 2n luminance level differences between adjacent sample points of (2n + 1) sample points of the upper scanning line, and a lower scanning line A third subtraction unit for calculating 2n luminance level differences between adjacent sample points of the (2n + 1) sample points and a second absolute value calculation unit for calculating the absolute value of the luminance level difference obtained by the second subtraction unit Comparing the absolute value of the brightness level difference calculated by the third subtraction unit with the 2n absolute values calculated by the second absolute value calculation unit and determining whether a minimum value exists A second comparison / detection unit for detecting the minimum value, a third comparison / detection unit for comparing the 2n absolute values obtained by the third absolute value calculation unit to determine whether a minimum value exists, and a first comparison / detection unit. The opening and closing are controlled by the gate signal output from the section, and the detection signal from the second and third comparison and detection sections is controlled. Providing a gate circuit for outputting the direction of the detection signal.

According to a seventh aspect of the present invention, in the invention of the sixth aspect, when the difference in luminance level between the sample points of the upper scanning line and the lower scanning line in the (2n + 1) direction is small, inappropriate interpolation processing is performed. In order to prevent this, between the second absolute value calculation unit and the second comparison detection unit, each of the 2n absolute values obtained by the second absolute value calculation unit is divided by 2 to the power of v (where v is A second coefficient part which is multiplied by a coefficient of (1 or more integer) and output to the second comparison and detection part is inserted, and the third absolute value calculation part obtains between the third absolute value calculation part and the third comparison and detection part. A 3rd coefficient part which multiplies each of the 2n absolute values by a coefficient of 1 / v and outputs the result to the third comparison / detection unit is inserted.

The invention of claim 8, 9 or 10 is the invention of claim 2, 3, 4, 5, 6 or 7 in order to simplify the circuit configuration (especially the configuration of the direction detection unit). Is set to 1. For example, the direction detection unit that detects the direction with the highest correlation among the (2n + 1) directions is set to the direction with the highest correlation among the three directions of the vertical direction, the 45 ° left diagonal direction, and the 45 ° right diagonal direction. (N = 1)
Case).

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a scan conversion circuit according to the present invention will be described below with reference to the drawings. FIG. 1 shows a first embodiment of the present invention, and the same parts as those in FIG. For convenience of explanation, input terminal 1
The case where the video signal Vi input to 0 is an NTSC video signal will be described. In FIG. 1, 42, 44, 4
6, 48 are D delay units, 50 is a direction detection unit, and 52 is a first delay unit.
The selection unit 54 is a second selection unit, and the first and second selection units 52,
54, the adder 18 and the coefficient unit 22 constitute an average value calculation unit 56.

The D delay units 42 and 44 are constituted by, for example, D-type flip-flop circuits, and sequentially delay the output signal of the 1H delay unit 14 by one dot and output. The D delay units 46 and 48 are constituted by, for example, D-type flip-flop circuits, and sequentially delay the output signal of the 262H delay unit 12 by one dot and output it.

The direction detection unit 50 outputs the output signals C, B, and A of the 1H delay unit 14 and the D delay units 42 and 44, respectively.
Based on the output signals F, E, D of the 262H delay unit 12 and the D delay units 46, 48, interpolation of the interpolation scanning line is performed for sample points on the scanning lines adjacent to the upper and lower sides of the interpolation scanning line. The direction having the strongest correlation among the three directions of the vertical direction centered on the point, the 45 ° left diagonal direction, and the 45 ° right diagonal direction is detected.

The direction detecting section 50 is specifically shown in FIG.
It is configured as shown in FIG. In FIG.
113, three first subtractors constituting a first subtraction unit, 13
1 and 132 are two second subtractors constituting a second subtraction unit,
151 and 152 are two third subtractors that constitute a third subtraction unit. Reference numerals 171 to 173 denote three first absolute value calculators forming a first absolute value calculating unit, 191 and 192 denote two second absolute value calculators forming a second absolute value calculating unit, 211,
Reference numeral 212 denotes two third absolute value calculators forming a third absolute value calculator. Reference numerals 231 to 233 denote three first coefficient units forming a first coefficient unit, 251 and 252 denote two second coefficient units forming a second coefficient unit, and 271 and 272 denote a second coefficient unit constituting a third coefficient unit. Third coefficient units. 29 is a subtractor for vertical priority, 31, 33, and 37 are first, second, and third comparison / detection sections, and 39 and 41 are first and second gate circuits.

The first subtractors 111, 112, 113
Calculates the difference between the output signals A, B, and C of the D delay units 44 and 42 and the 1H delay unit 14 and the output signals F, E and D of the 262H delay unit 12 and D delay units 46 and 48. And a 45 ° diagonally left direction about the interpolation point (hereinafter simply referred to as (−45)
°) direction), vertical direction (hereinafter simply (+90)
(°) direction) and the brightness level difference between the sample points of the upper scanning line and the lower scanning line in the 45 ° right diagonal direction (hereinafter simply referred to as the (+ 45 °) direction). The second subtractors 131 and 132 output signals D and E and output signals E and F, respectively.
Is calculated, and the luminance level difference at the sample point of the lower scanning line is obtained. The third subtractors 151 and 152 calculate the difference between the output signals A and B and the output signals B and C, and obtain the difference in luminance level between the sample points on the upper scanning line.

The first absolute value calculators 171, 172, 1
73 calculates the absolute value of the difference obtained by the first subtractors 111, 112, 113, and calculates the second absolute value calculators 191, 1
92 calculates the absolute value of the difference calculated by the second subtractors 131 and 132, and the third absolute value calculators 211 and 212 calculate the absolute value of the difference calculated by the third subtractors 151 and 152. .

The first coefficient units 231, 232, 233
Is obtained by multiplying the absolute value obtained by the first absolute value calculators 171, 172, 173 by a coefficient “1 / m 2” to obtain a signal a,
b0 and c, and the second coefficient units 251 and 252 output
The signals d and e are output by multiplying the absolute values calculated by the second absolute value calculators 191 and 192 by a coefficient “1 / v”.
The third coefficient units 271 and 272 multiply the absolute values calculated by the third absolute value calculators 211 and 212 by a coefficient “1 / v” to output signals f and g. The first coefficient unit 2
31, 232, and 233 are configured with, for example, m-stage shift registers, and the second coefficient units 251 and 252 and the third coefficient units 271 and 272 are configured with, for example, v-stage shift registers. The subtractor 29 is provided in the first coefficient unit 2
A signal b obtained by subtracting a preset set value S from the 32 output signals b0 is output.

The first comparison and detection section 31 outputs the output signals a,
b and c are compared, and when a is the minimum value (a <b, a <c)
In the (-45 °) direction, and when b is the minimum value (b <a,
When (b <c), the (+ 90 °) direction is detected as the direction having the strongest correlation, and when c is the minimum value (when c <a, c <b), the (+ 45 °) direction is detected as the direction having the strongest correlation. , A = b =
At the time of c, a gate signal (H, L level signal) is output, and at other times (for example, when a = b <c),
The (+ 90 °) direction is detected as the direction having the strongest correlation.

The second comparison and detection section 33 outputs the output signal d,
e, and when d <e, the signal (−45 °) 1 is
When e <d, the signal (+ 45 °) 1 is output, and at other times, the signal (+ 90 °) 1 is output as a signal indicating the correlation between adjacent sample points on the lower scanning line. The third comparison and detection unit 37 compares the output signals f and g, and f <
The signal (+ 45 °) 2 when g, the signal (−45 °) 2 when g <f, and the signal (+90
°) 2 is output as a signal indicating the correlation between adjacent sample points on the upper scanning line.

The first gate circuit 39 operates when the gate signal of the first comparison / detection section 31 is at H level (a = b = c
AND gates 43, 45, and 4 which are closed when L level (corresponding to cases other than a = b = c)
7. The AND gate 43 outputs a signal (−45) from the second and third comparison / detection units 33 and 37 when the gate signal from the first comparison / detection unit 31 is at the H level.
(°) 1 and (−45 °) 2 output (−45
°) Output a signal with the direction having the strongest correlation. The AND gate 45 is connected to the first comparison and detection unit 31.
Is high, and the signals (+ 45 °) 1 and (+45) are output from the second and third comparison / detection units 33 and 37.
°) 2 and outputs a signal with the (+ 45 °) direction as the direction with the strongest correlation. The AND gate 47 is configured such that the gate signal from the first comparison and detection unit 31 is at H level and the second and third comparison and detection units 33 and 37
When the signals (+ 90 °) 1 and (+ 90 °) 2 are output from, a signal with the (+ 90 °) direction having the strongest correlation is output.

The second gate circuit 41 has an OR gate 4
9, 51, and 53. The OR gate 49
Outputs a logical sum signal of signals having the (-45 °) direction output from each of the first comparison detection unit 31 and the AND gate 43 as the direction having the strongest correlation. The OR gate 51 is connected to the first comparison / detection unit 31 and the AND gate 47.
, And outputs a logical sum signal of signals having the (+ 90 °) direction as the direction having the strongest correlation. The OR gate 53 outputs a logical sum signal of signals having the (+ 45 °) direction output from each of the first comparison detection unit 31 and the AND gate 45 as the direction having the strongest correlation.

The first selecting section 52, based on the direction detection signal of the direction detecting section 50, includes a 1H delay unit 14 and a D delay unit 42 corresponding to three sample points (pixel points) of the upper scanning line. , 44, a video signal of a corresponding one sample point is selected. The second selector 54
Is based on a direction detection signal of the direction detection unit 50,
From among the output signals of the 262H delay unit 12 and the D delay units 46 and 48 corresponding to the three sample points of the lower scanning line, the video signal of the corresponding one sample point is selected. The adder 18 adds the output signal of the first selection unit 52 and the output signal of the second selection unit 54, and the coefficient unit 22 multiplies the output signal of the adder 18 by a coefficient 、 to perform a field interpolation process. As a video signal.

Next, the operation of FIG. 1 will be described with reference to FIGS. 2, 3 and 4.
Will be described together. (1) The NTSC video signal Vi input to the input terminal 10 is a 262H delay unit 12, a 1H delay unit 14, 262
The signal is delayed by (1 frame + 1 dot) by the H delay unit 16 and the D delay unit 35, and is input to the coefficient unit 24 as a video signal for inter-field interpolation. For example, as shown by the arrow in FIG. 3B, the interpolation point Np of the interpolation scanning line of the field (n) is used.
For the field (n-
The video signal of the sample point Sp at a predetermined position on the corresponding scanning line in 1) is input to the coefficient unit 24 as a video signal of the field interpolation processing.

(2) A signal C obtained by delaying the input video signal Vi by 263H by the 262H delay unit 12 and the 1H delay unit 14.
And the signal B delayed by one dot by the D delay unit 42
And the signal A delayed by one dot by the D delay unit 44
262H by the 262H delay unit 12
When the signal F delayed by one minute, the signal E further delayed by one dot by the D delay unit 46, and the signal D further delayed by one dot by the D delay unit 48 are input to the direction detection unit 50, The direction detection unit 50 calculates the interpolation point Np of the interpolation scanning line.
Vertical centered on the center, 45 ° diagonally left and 4 diagonally right
In three directions of 5 °, corresponding sample points Spb, Spa, Spc and Spe of the upper scanning line and the lower scanning line,
The luminance level difference between Spf and Spd is obtained and compared, and the smallest value (that is, the direction with the strongest correlation) is detected.

Next, the operation of the direction detection unit 50 of the above (2) will be described with reference to FIG.
Details will be described up to 7). (2-1) The signals A, B, C, D, E, and F are converted by the first subtractor 1
11, 112 and 113, the first subtractor 1
Signals A, B, and C and signals F, E,
D is obtained, and then the first absolute value calculators 171 and 1
At 72 and 173, the absolute value is obtained. The absolute values obtained by the first absolute value calculators 171 and 173 are converted by the corresponding first coefficient units 231 and 233 into the coefficient “1 / m” (for example, １ ／ (for m = 2)). , The influence of the noise component on the detection result is suppressed, and the signals are input to the first comparison and detection unit 31 as signals a and c. The absolute value obtained by the first absolute value calculator 172 is converted into a coefficient “2” by the corresponding first coefficient unit 232.
Is multiplied by 1 / m "to obtain a signal b0 in which the influence of the noise component on the detection result is suppressed, and further, the set value S is subtracted by the subtractor 29 to give priority to the signal b in the vertical direction.
Is input to the first comparison detection unit 31.

(2-2) The first comparison / detection section 31 compares the input signals a, b, and c. When a is the minimum value, the signal is in the (-45 °) direction, and when b is the minimum value, the signal is (+90).
°) direction is detected as the direction having the strongest correlation when c is the minimum value, and the (+ 45 °) direction is detected as the direction having the strongest correlation.
In the case of c, a gate signal (H level signal) is output, and in other cases, a signal in which the (+ 90 °) direction has the strongest correlation is output. At this time, the above (2-1)
As is clear from FIG. 3, the set value S is subtracted only for the signal b having the (+ 90 °) direction having the strongest correlation among the three input signals a, b, and c, and the (−45 °) direction is obtained. , (+ 45 °) direction is given priority over the (+ 90 °) direction.

(2-3) The signals D, E and F are supplied to the second subtractor 1
31 and 132, the second subtracters 131 and 1
At 32, the difference between the signals D and E and the signals E and F is obtained, and then the absolute values are obtained at the second absolute value calculators 191 and 192. When the signals A, B, and C are input to the third subtractors 151 and 152, the differences between the signals A and B and the signals B and C are obtained by the third subtractors 151 and 152.
At steps 11 and 212, the absolute value is obtained. The absolute values calculated by the second absolute value calculators 191 and 192 are multiplied by the coefficients “one of 2 to the power of v” by the corresponding second coefficient units 251 and 252, and the second comparison and detection are performed as signals d and e. The absolute value input to the unit 33 and obtained by the third absolute value calculators 211 and 212 is
Corresponding third coefficient units 271 and 272 multiply the coefficient by “one of 2 to the power of v”, and as signals f and g, the third comparison and detection unit 3
Enter 7

(2-4) The second comparison and detection section 33 compares the input signals d and e, and when d <e, the signal (-4)
5 °) 1 and when e <d, the signal (+ 45 °) 1 is
At other times, the signal (+ 90 °) 1 is output as a signal indicating the correlation between adjacent sample points on the lower scanning line. In the third comparison and detection section 37, the input signal f,
g are compared, and when f <g, the signal (+ 45 °) 2
However, the signal (−45 °) 2 is output when g <f, and the signal (+ 90 °) 2 is output otherwise.

(2-5) The gate signal output from the first comparison and detection section 31 is at the H level, and the signals (−45 °) 1 and (−45 °) from the second and third comparison and detection sections 33 and 37 are output. 2 is output, a signal is output to the output side of the AND gate 43 of the first gate circuit 39, with the (−45 °) direction having the strongest correlation. When the gate signal is at the H level, the signal (+45) is output from the second and third comparison / detection sections 33 and 37.
When (°) 1 and (+ 45 °) 2 are output, similarly, a signal having the (+ 45 °) direction as the direction having the strongest correlation is output to the output side of the AND gate 45. Similarly, when the gate signal is at the H level and the signals (+ 90 °) 1 and (+ 90 °) 2 are output from the second and third comparison / detection sections 33 and 37, the output side of the AND gate 47 is set to ( + 90 °), and outputs a signal with the direction having the strongest correlation.

(2-6) Therefore, the first comparison and detection unit 3
No. 1 gives priority to the (+ 90 °) direction (vertical direction) over the 45 ° left oblique direction and the 45 ° right oblique direction centered on the interpolation point of the interpolation scanning line.
When a is the minimum value (a <b, a <c), (-45 °)
The direction is (+ 90 °) when b is the minimum value (when b <a, b <c), and when c is the minimum value (c <a, c
In the case of <b), the (+ 45 °) direction is detected as the direction having the strongest correlation. Otherwise, and a
Even when = b = c does not hold, the (+ 90 °) direction is detected as the direction having the strongest correlation.

(2-7) When a = b = c,
The gate signal output from the first comparison and detection unit 31 becomes H level, and the AND gates 43 and 4 of the first gate circuit 39 are output.
5 and 47 are opened, and the influence of the output of the second and third comparison detection sections 33 and 37 appears. That is, the sample point Spd,
The brightness level difference between Spe is smaller than the brightness level difference between sample points Spe and Spf, and sample points Spb and S
When the brightness level difference between pc is smaller than the brightness level difference between sample points Spa and Spb (d <e and g <f), a signal (−45) is output to the output side of the second comparison and detection unit 33.
1), a signal (−45 °) 2 appears on the output side of the third comparison / detection unit 37, and a signal with the (−45 °) direction having the strongest correlation is output on the output side of the AND gate 43. Output. When the brightness level difference between the sample points Spe and Spf is smaller than the brightness level difference between the sample points Spd and Spe, and the brightness level difference between the sample points Spa and Spb is smaller than the brightness level difference between the sample points Spb and Spc ( When e <d and f <g), a signal having the (+ 45 °) direction as the direction having the strongest correlation is output to the output side of the AND gate 45 in the same manner. At other times,
A signal (+ 90 °) 1 appears on the output side of the second comparison / detection unit 33, and the signal (+ 90 °) appears on the output side of the third comparison / detection unit 37.
2 appears, and a signal having the (+ 90 °) direction having the strongest correlation is output to the output side of the AND gate 47 in the same manner.

(3) Returning to FIG. 1, when the direction detection signal of the direction detection section 50 is input to the first selection section 52, the first selection section 52 inputs the input signals C and C based on the direction detection signal.
A corresponding signal (for example, signal C) of B and A is selected and output. For example, assuming that the direction detection signal of the direction detection unit 50 is in the 45 ° right diagonal direction, the interpolation point Np among the three sample points Spa, Spb, and Spc of the upper scanning line in FIG. On the other hand, the video signal C at the sample point Spc located in the 45 ° diagonal right direction is selected. Further, assuming that the direction detection signal is in the vertical direction or the 45 ° diagonally left direction, similarly, the video signal B at the sample point Spb or the video signal A at the sample point Spa in FIG. .

(4) When the direction detection signal of the direction detection unit 50 is input to the second selection unit 54, the second selection unit 54
Based on the direction detection signal, a corresponding signal (for example, signal D) among the input signals F, E, and D is selected and output. For example, the direction detection signal of the direction detection unit 50 is 45 ° diagonally right.
3A, the interpolation point Np among the three sample points Spd, Spe, Spf of the lower scanning line in FIG.
Sample point Spd located at an angle of 45 ° to the right with respect to
And outputs the selected video signal D. Further, assuming that the direction detection signal is in the vertical direction or the 45 ° left diagonal direction, similarly, the video signal E of the sample point Spe or the video signal F of the sample point Spf in FIG. .

(5) The adder 18 adds the output signal of the first selector 52 and the output signal of the second selector 54, and
Multiplies the output signal of the adder 18 by a coefficient １ ／ and outputs the resulting signal to the coefficient unit 26 as a video signal for field interpolation processing.
For example, if the direction detection signal of the direction detection unit 50 is
If the angle is in the ° direction, the video signal C of the sample point Spc of the upper scanning line and the sample point S of the lower scanning line in FIG.
The video signal D of pd is added, the video signal is averaged by multiplying by １ ／ and output to the coefficient unit 26 as the video signal of the field interpolation processing. If the direction detection signal is in the vertical direction, the sample point Sp on the upper scanning line in FIG.
b, and the video signal E at the sampling point Spe of the lower scanning line is added, and the video signal is averaged by 倍.
The signal is output to the coefficient unit 26 as a video signal for the field interpolation processing.

(6) The input video signal Vi and the input video signal Vi are transmitted to the 262H delay unit 12, the 1H delay units 14 and 2
When the signal delayed by one frame by the 62H delay unit 16 is input to the motion detecting unit 28, the motion detecting unit 28 compares the corresponding video signals between frames to detect the motion of the image. K = 0, K = 1 for a still image
Then, a motion detection signal (1-K), K, is output.

(7) In the case of a moving image, the motion detection signal (1-K) of the motion detector 28, K is 1, 0 (when K = 0)
Therefore, only the video signal of the field interpolation processing output from the coefficient unit 22 passes through the coefficient unit 26 and is input to the double-speed conversion unit 36 via the adder 20. For this reason, the double-speed conversion unit 36 delays the video signal Vi by (263H + 1D) by the 262H delay unit 12, the 1H delay unit 14, and the D delay unit 34, and performs the field interpolation processing output from the adder 20. A double speed conversion process with the video signal is performed, and the output terminal 38
Outputs a video signal Vp for progressive scanning.

(8) Therefore, when the oblique line 40 having a line width of 2 dots and a diagonally right angle of 45 ° as shown in FIG. 4 appears in the moving image, the direction detection unit 50 sets the diagonally right direction of 45 °. The direction is detected as the direction having the strongest correlation, and the first and second selecting units 52 and 54 use this detection signal to determine the interpolation point N of the interpolation scanning line.
The video signals C and D of the sample points Spc and Spd in the lighting state of the upper scanning line and the lower scanning line which are positioned at an angle of 45 ° to the right with respect to p1 are selected, and averaged by the adder 18 and the coefficient unit 22. It is assumed that the video signal is at the interpolation point Np1. Similarly,
The video signal of the interpolation point Np2 is also a signal obtained by averaging the video signal of the lighting sample point. Therefore, the interpolation point Np
1, Np2 is in a desirable lighting state, and the interpolation points Np3, Np4 on both sides are in a desirable non-lighting state, so that the oblique line 40 can be prevented from looking unnatural.

(9) For a still image, the motion detection unit 28
Motion detection signal (1-K), K becomes 0, 1 (K = 1
Therefore, only the video signal of the field interpolation processing (that is, the video signal one field before) output from the D delay unit 35 passes through the coefficient unit 24 and is input to the double-speed conversion unit 36 via the adder 20. . For this reason, the double-speed conversion unit 36 delays the video signal Vi by (263H + 1D) by the 262H delay unit 12, the 1H delay unit 14, and the D delay unit 34, and performs the field interpolation processing output from the D delay unit 35. , And outputs a progressive scanning video signal Vp to an output terminal 38.

In the embodiment shown in FIG. 1, the case where the average value calculating section is composed of the first and second selecting sections, the adder and the coefficient unit has been described. However, the present invention is not limited to this.
As shown in the figure, the average value calculation unit 56a is
0, 62, 64 and three coefficient units 66, 68, 70,
It can also be used in the case where it is configured with the selection unit 72.

In FIG. 5, an adder 60 adds the signal A and the signal F, and a coefficient unit 66 multiplies the output signal of the adder 60 by a coefficient 出力 and outputs the result. For this reason, from the output side of the coefficient unit 66, the sample point Spa of the upper scanning line and the lower scanning line which are located at an angle of 45 ° to the left with respect to the interpolation point Np of the interpolation scanning line of FIG. A video signal obtained by averaging the signal A and the signal F at the sample point Spf is output. Further, the addition unit 62
Adds the signal B and the signal E, and the coefficient unit 68
Is multiplied by a factor of 1/2 and output. For this reason,
From the output side of the coefficient unit 68, the signal B of the sample point Spb of the upper scan line and the sample point Spe of the lower scan line located in the vertical direction with respect to the interpolation point Np of the interpolation scan line in FIG. And a video signal obtained by averaging the signal E. The adder 64 adds the signal C and the signal D, and the coefficient unit 70 multiplies the output signal of the adder 64 by a coefficient 係数 and outputs the result. For this reason, from the output side of the coefficient unit 70, the sample point Spc of the upper scanning line and the lower scanning line which are located at an angle of 45 ° to the right with respect to the interpolation point Np of the interpolation scanning line of FIG. A video signal obtained by averaging the signal C and the signal D at the sample point Spd is output.

When the direction detection signal of the direction detection unit 50 is input to the selection unit 72, the selection unit 72 outputs one of the output signals of the three coefficient units 66, 68, 70 based on the direction detection signal. Select and output as a video signal for field interpolation. For example, the output signal of the coefficient unit 66 is selected when the direction detection signal of the direction detection unit 50 is in the 45 ° left diagonal direction, and when the direction detection signal is in the vertical direction, the coefficient unit 6 is selected.
8 is selected, and the output signal of the coefficient unit 70 is selected when the direction detection signal is in the 45 ° right diagonal direction.

In the case of a moving image, the motion detection signal (1-K) of the motion detection section 28, K becomes 1, 0 (when K = 0)
Therefore, only the field interpolation video signal output from the selection unit 72 passes through the coefficient unit 26 and is input to the double speed conversion unit 36 via the adder 20. For this reason, the double speed conversion unit 36
Performs a double-speed conversion process on a signal obtained by delaying the video signal Vi by (263H + 1D) and a video signal output from the adder 20, and outputs a video signal Vp for progressive scanning to the output terminal 38. Therefore, when a line width of 2 dots as shown in FIG. 4 and an oblique line 40 in the right oblique direction at 45 ° appear in the moving image, the oblique line 40 looks unnatural as in the case of FIG. Can be prevented.

In the embodiment shown in FIGS. 1 and 5, in order to simplify the circuit configuration (particularly the configuration of the direction detection unit), the direction detection unit scans the upper side with respect to the interpolation point of the interpolation scanning line. Vertical direction of line and lower scanning line, 45 ° left diagonal direction and 4 right diagonal direction
Although the case where the direction having the strongest correlation is detected in three directions of 5 ° has been described, the present invention is not limited to this, and the upper scanning line and the lower scanning The present invention can be used in a case where a direction that has the strongest correlation is detected in the (2n + 1) direction including the vertical direction and the oblique direction of the line or in the 2n direction.
For example, it is also possible to use the case where n in the (2n + 1) direction is set to 2. That is, the direction detection unit is
It is also used in the case of detecting a direction having the strongest correlation among five directions of a vertical direction, a 45 ° left diagonal direction, a 45 ° right diagonal direction, a 30 ° left diagonal direction, and a 30 ° right diagonal direction. be able to. In this case, it is possible to prevent more oblique lines in the moving image from looking unnatural without making the configuration of the directionality detection unit so complicated.

In the embodiment shown in FIGS. 1 and 5, in order to simplify the structure of the average value calculating section, the average value calculating section
The case where the second selector, the adder and the coefficient unit are configured, or the case where the second selector is configured with the (2n + 1) adder, the coefficient unit and the selector are described. However, the present invention is not limited to this. Lines and (2n + 1) or 2n lower scan lines
The average value of the video signals of two sample points corresponding to the detection direction of the directionality detection unit out of the sample points may be calculated and used as the video signal for the field interpolation processing.

In the embodiment shown in FIGS. 1 and 5, the motion detection signal (1-K) and K of the motion detection unit 28 become 0 and 1 for a still image, and the motion detection signal of the motion detection unit 28 for a moving image. (1-K), the case where K is 1, 0 has been described, but the present invention is not limited to this, and the motion detection unit 2
Eight motion detection signals (1−K) can also be used in cases where K of K is other than 2 types of 1 and 0 (for example, in the case of 3 types of K, 1 1/2 and 0). For example, when the image is completely still, the motion detection signal (1-K) of the motion detection unit 28, K is 0, 1 (when K = 1),
When the image is slightly moving, the motion detection signal (1-K) of the motion detecting unit 28 is 、, （(when K = １ ／). The motion detection signal (1-K) of the detection unit 28, where K is 1, 0 (K
= 0) can also be used.

In the above embodiment, the input video signal is NT
Although the case of the video signal of the SC system has been described, the present invention is not limited to this, and the present invention can also be used for the video signal of the PAL system, the SECAM system, and the HDTV system. For example, if the input video signal is PAL or S
In the case of the ECAM system video signal, 262 in FIGS.
By replacing the H delay units 12 and 16 with 312H delay units, the 262H delay units 12 and 16 shown in FIGS. 1 and 4 are replaced by 562H when the input video signal is an HDTV video signal.
It can be used by replacing it with a delay unit.

In the above embodiment, the motion of the image is detected based on the input video signal for interlaced scanning, and the video signal for the field interpolation processing and the video signal for the field interpolation processing are detected in accordance with the motion detection signal. The case where the present invention is applied to a scan conversion circuit that outputs a video signal for progressive scanning in the double-speed conversion processing of the interpolation point video signal and the input video signal by obtaining the interpolation point video signal by combining the video signals has been described. However, the present invention is not limited to this. A video signal obtained by interpolating a video signal of an interpolation scanning line from an input video signal of a scanning line adjacent above and below the interpolation scanning line and doubling the scanning line is obtained. The present invention can be used for an output scan conversion circuit. For example, as shown in FIG.
Delay units 12 and 16, motion detection unit 28, coefficient units 24 and 2
6, omitting the D delay units 30, 32, and 35 and the adder 20, and averaging the signal obtained by delaying the interlace scanning video signal Vi input to the input terminal 10 by the 1H delay unit 14 and the D delay unit 34. The video signal of the interpolated scanning line obtained by the value calculation unit 56 is input to the double speed conversion unit 36, and the double speed conversion unit 36
It can also be used in the case where the video signal Vp for progressive scanning is output to the output terminal 38 in the double speed conversion processing of.

[0054]

According to the first aspect of the present invention, there is provided a scan conversion circuit for interpolating a video signal of an interpolated scan line from an input video signal of an upper scan line and a lower scan line and outputting a video signal having a doubled scan line. , A direction detection unit and an average value calculation unit, and the direction detection unit includes a first subtraction unit, a first absolute value calculation unit, and a first comparison detection unit. The brightness level difference between the sample points of the upper scanning line and the lower scanning line in a plurality of directions including the vertical direction and the oblique direction centered on the insertion point is obtained, the absolute value is obtained by the first absolute value calculation unit, and the first comparison is performed. The direction of the strongest correlation is detected by comparing a plurality of absolute values by the detection unit, and the average value of the video signals of two sample points corresponding to the detection direction is calculated by the average value calculation unit, and the image of the interpolation scanning line is calculated. Signal, so when displaying a moving image with the video signal after scan conversion processing, It can reproduce an image of high quality to prevent the straight and the oblique lines look unnatural.

According to a second aspect of the present invention, in the first aspect of the present invention, the first subtraction unit sets the upper scanning line in the vertical direction centering on the interpolation point of the interpolation scanning line and in the (2n + 1) direction including the left and right diagonal directions. And (2n + 1) subtractors for calculating the luminance level difference between the sample point of the lower scanning line and the lower scanning line. The first absolute value calculator is composed of (2n + 1) absolute value calculators. Compares the (2n + 1) absolute values obtained by the absolute value calculator, detects the direction with the strongest correlation, and calculates the average value from the (2n + 1) sample points of the upper scanning line and the lower scanning line. 2 corresponding to the detection direction of the first comparison detection unit.
Since the average value of the video signals at the sample points is calculated, appropriate interpolation processing can also be performed on the left and right diagonal lines around the vertical line in the moving image.

According to a third aspect of the present invention, in the second aspect of the present invention, each absolute value calculator determines between the (2n + 1) absolute value calculators of the first absolute value calculator and the first comparison detector. Since the absolute value obtained by multiplying the absolute value by a factor of 1 / m (m is an integer of 1 or more) and inserting the first coefficient portion to be output to the first comparison and detection section is inserted, the interpolation point of the interpolation scanning line is centered. In the (2n + 1) direction, when the brightness level difference between the sample points of the upper scanning line and the lower scanning line is small, inappropriate interpolation processing can be prevented.

According to a fourth aspect of the present invention, in the third aspect of the present invention, the set value is subtracted from the output signal corresponding to the vertical direction among the (2n + 1) output signals of the first coefficient section to perform the first comparison detection. Since a subtractor for vertical priority output to the section is provided,
When the absolute value of the luminance level difference between the sample points of the upper scanning line and the lower scanning line in the (2n + 1) direction is substantially equal,
It is possible to prioritize the interpolation processing by the video signal of the sample point in the vertical direction.

According to a fifth aspect of the present invention, in the second, third or fourth aspect of the present invention, the first comparison and detection section compares (2n + 1) absolute values obtained by the first absolute value calculation section, If the minimum value does not exist, the detection signal indicating the vertical direction is output when there exists the detection signal indicating the vertical direction. Therefore, the upper scanning line and the lower scanning line in the (2n + 1) direction are output. When the minimum value does not exist in the absolute value of the luminance level difference of the sample point, the vertical interpolation processing can be prioritized.

According to a sixth aspect of the present invention, in the second, third or fourth aspect of the present invention, the first comparison and detection section compares (2n + 1) absolute values obtained by the first absolute value calculation section, When it exists, it outputs a corresponding one-way detection signal,
When the absolute values are equal to each other, a gate signal is output. Otherwise, a vertical detection signal is output. The second and third subtraction units adjoin the (2n + 1) sample points of the upper scanning line and the lower scanning line. The 2n number of brightness level differences from the sample point are obtained, the absolute value of the brightness level difference is obtained by the second and third absolute value calculation sections, and the 2n and 3n comparison detection sections are used to obtain the absolute value of the brightness level difference.
The first and second comparison circuits detect the presence or absence of the minimum value by comparing the absolute values of the first and second detection signals, and respond to the detection signals of the second and third comparison and detection sections by a gate circuit whose opening and closing are controlled by the gate signal of the first comparison and detection section. (2)
Optimal interpolation can be performed even when the absolute values of the luminance level differences between the sample points of the upper scanning line and the lower scanning line in the (n + 1) direction are substantially equal.

According to a seventh aspect of the present invention, in the invention of the sixth aspect, each of the 2n absolute values obtained by the second absolute value calculating section is provided between the second absolute value calculating section and the second comparison detecting section. 2v
The second value multiplied by a factor of the power of 1 and output to the second comparison detection unit
A coefficient part is inserted, and between the third absolute value calculating part and the third comparison detecting part, each of the 2n absolute values obtained by the third absolute value calculating part is multiplied by a coefficient of 1/2 power. Since the third coefficient portion to be output to the third comparison and detection unit is inserted, an inappropriate interpolation process is performed when the brightness level difference between the sample points of the upper scanning line and the lower scanning line in the (2n + 1) direction is small. You can choose not to do it.

According to the eighth, ninth or tenth aspect of the present invention, n is set to 1 in the second, third, fourth, fifth, sixth or seventh aspect of the invention, so that the circuit configuration (particularly, the configuration of the direction detection unit) is simplified. Can be For example, the direction detection unit that detects the direction with the highest correlation among the (2n + 1) directions is set to the direction with the highest correlation among the three directions of the vertical direction, the 45 ° left diagonal direction, and the 45 ° right diagonal direction. (In the case of n = 1), the vertical line, the diagonal line in the left diagonal direction of 45 ° and the diagonal line in the diagonal right direction of 45 ° are formed with a simple circuit configuration. It can be prevented from looking unnatural.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a first embodiment of a scan conversion circuit according to the present invention.

FIG. 2 is a block diagram illustrating a specific example of a direction detection unit in FIG. 1;

3A and 3B are diagrams for explaining the operation of FIGS. 1 and 2, wherein FIG. 3A is an explanatory diagram of a field interpolation process, and FIG. 3B is an explanatory diagram of an inter-field interpolation process.

FIG. 4 is a diagram for explaining the operation of FIGS. 1 and 2, and is an explanatory diagram of a field interpolation process for an oblique line in a moving image.

FIG. 5 is a block diagram showing a second embodiment of the scan conversion circuit according to the present invention.

FIG. 6 is a block diagram showing a third embodiment of the scan conversion circuit according to the present invention.

FIG. 7 is a block diagram showing a conventional example.

8 is a diagram for explaining the operation of FIG. 7, and is an explanatory diagram of a field interpolation process and an inter-field interpolation process.

FIG. 9 is a diagram for explaining the operation of FIG. 7, and is an explanatory diagram of a field interpolation process for oblique lines in a moving image.

[Explanation of symbols]

10: input terminal, 111 to 113: first subtractor (first
.., 262H delay unit, 131, 132... Second subtractor (component example of second subtraction unit),... 1H delay unit, 151, 152... Third subtractor ( Example of components of third subtraction unit), 171 to 17
3, a first absolute value calculator (a component example of a first absolute value calculating unit), 18, 20, 60, 62, 64 ... an adder, 1
91, 192... Second absolute value calculators (examples of components of the second absolute value calculator), 211, 212... Third absolute value calculators (examples of components of the third absolute value calculator), 22, 66, 6
8, 70 ... coefficient units, 231 to 233 ... first coefficient units (examples of components of the first coefficient unit), 24, 26 ... coefficient units with variable coefficients, 251 and 252 ... second coefficient units (second coefficient unit) 271, 272... Third coefficient unit (third coefficient unit)
Component elements of the coefficient section), 28: motion detector, 29: subtractor for vertical priority, 30, 32, 34, 35, 42,
44, 46, 48: D delay unit, 31: first comparison and detection unit, 33: second comparison and detection unit, 36: double speed conversion unit,
37: third comparison / detection section, 38: output terminal, 39: first
Gate circuit, 40: diagonal line, 41: second gate circuit, 43, 45, 47: AND gate, 49, 5
1, 53: OR gate, 50: Directivity detector, 52
... First selection unit, 54 ... Second selection unit, 56, 56a ...
Average value calculation unit, 72: selection unit, (−45 °): detection signal in the 45 ° left diagonal direction, (+ 45 °): 45 right tilt
° detection signal, (+ 90 °): detection signal in the vertical direction, A, B, C: sample points Spa to S on the upper scanning line
pc, video signal D, E, F... video signal of lower scanning line sampling points Spd-Spf, Np, Np1-Np4
... interpolation points, Sp, Spa-Spf ... sample points,
K, 1-K: a pair of motion detection signals output from the motion detection unit 28; Vi: a video signal for interlaced scanning;
p: a video signal for progressive scanning.

Continued on the front page (72) Inventor Makoto Ikeda 1116 Suenaga, Takatsu-ku, Kawasaki-shi, Kanagawa F-term in Fujitsu General Limited (reference) 5C063 AA02 AA03 AA04 AA11 AC01 BA04 BA09 BA12 CA01 CA07 CA38 CA40

Claims (10)

[Claims] 1. A scan conversion circuit for interpolating a video signal of an interpolated scanning line from an input video signal of a scanning line adjacent to an upper side and a lower side of an interpolated scanning line and outputting a doubled scanning line video signal. Based on input video signals of a plurality of sample points of the upper scanning line and the lower scanning line, the strongest correlation is obtained from among a plurality of directions including a vertical direction and an oblique direction centered on the interpolation point of the interpolation scanning line. A direction detection unit that detects a direction, and an average value of video signal values of two sample points corresponding to a detection direction of the direction detection unit among a plurality of sample points of the upper scanning line and the lower scanning line. An average value calculating unit that calculates and outputs a video signal of an interpolation scanning line, wherein the directionality detection unit performs the interpolation based on video signals of a plurality of sample points of the upper scanning line and the lower scanning line. Vertical and diagonal directions around the interpolation point of the scanning line First obtaining the luminance level differences of the sampling points of the upper scanning line and the lower scanning lines for a plurality of directions including
A subtraction unit, a first absolute value calculation unit for calculating an absolute value of the luminance level difference obtained by the first subtraction unit, and a plurality of absolute values obtained by the first absolute value calculation unit are compared. A scan conversion circuit comprising: a first comparison detection unit that detects a strong direction. 2. A first subtraction section, based on video signals of an upper scanning line and a lower scanning line, a (2n + 1) direction including a vertical direction centered on an interpolation point of an interpolation scanning line and a left and right diagonal direction. (N is an integer greater than or equal to 1), and comprises (2n + 1) subtracters for calculating the brightness level difference between the sample points of the upper scanning line and the lower scanning line.
1) It is composed of (2n + 1) absolute value calculators for obtaining the absolute value of the luminance level difference obtained by each of the subtracters, and the first comparison / detection unit is configured by each of the (2n + 1) absolute value calculators. 2. The scan conversion circuit according to claim 1, wherein the determined (2n + 1) absolute values are compared to detect a direction having the strongest correlation. 3. An absolute value obtained by each first absolute value calculator between the (2n + 1) absolute value calculators of the first absolute value calculator and the first comparison and detection unit, which is 2 m times larger. 1 (m is an integer of 1 or more)
3. The scan conversion circuit according to claim 2, wherein a first coefficient section which is multiplied by the coefficient and output to the first comparison / detection section is inserted. 4. A vertical priority subtracter for subtracting a set value from an output signal corresponding to a vertical direction among (2n + 1) output signals of the first coefficient unit and outputting the result to a first comparison / detection unit is provided. 4. The scan conversion circuit according to claim 3, wherein: 5. The first comparison / detection unit compares (2n + 1) absolute values obtained by the first absolute value calculation unit, and when a minimum value exists, a corresponding one of (2n + 1) directions is selected. 5. The scan conversion circuit according to claim 2, wherein a detection signal is output and a vertical detection signal is output when there is no minimum value. 6. A first comparison / detection section compares (2n + 1) absolute values obtained by a first absolute value calculation section, and, when a minimum value exists, a corresponding one of (2n + 1) directions. A detection signal is output, a gate signal is output when the absolute values are equal, and a detection signal in the vertical direction is output when the absolute value is other than that, and 2n of the (2n + 1) sample points on the upper scanning line with the adjacent sample points are output. A second subtraction unit for calculating two brightness level differences, a third subtraction unit for calculating 2n brightness level differences between adjacent sample points of (2n + 1) sample points on the lower scanning line, and the second subtraction unit A second absolute value calculating unit for obtaining an absolute value of the luminance level difference obtained by the above, a third absolute value calculating unit for obtaining an absolute value of the luminance level difference obtained by the third subtracting unit, and the second absolute value calculating unit The minimum value exists by comparing the 2n absolute values obtained in A second comparison / detection unit for detecting whether or not a minimum value is present by comparing the 2n absolute values obtained by the third absolute value calculation unit; And a gate circuit that is opened and closed by a gate signal output from the first comparison and detection section and outputs a detection signal indicating a direction corresponding to the detection signal from the second and third comparison and detection sections. 5. The scan conversion circuit according to 2, 3, or 4. 7. A method according to claim 7, wherein each of the 2n absolute values calculated by said second absolute value calculating section is divided by 2 to the power of v (where v is 1) between the second absolute value calculating section and the second comparison detecting section. A second coefficient part which is multiplied by a coefficient of the above (integer) and output to the second comparison / detection section is inserted between the third absolute value calculation section and the third comparison / detection section. Each of the 2n absolute values obtained is 2
7. The scan conversion circuit according to claim 6, wherein a third coefficient part which is multiplied by a coefficient of 1 / v and output to said third comparison and detection unit is inserted. 8. The method according to claim 2, wherein n = 1.
The scan conversion circuit as described in the above. 9. The scan conversion circuit according to claim 5, wherein n = 1. 10. The scan conversion circuit according to claim 6, wherein n = 1.