JPH0232680A - Perpendicular ring contour correction circuit - Google Patents

Abstract

PURPOSE:To perform perpendicular ring contour correction with fine shoot and without enhancing the mis-interpolation of a scanning line by applying control so that a quadratic differential component for perpendicular ring contour correction obtained at a quadratic differential circuit can go to 0 only in the neighborhood of a peaking frequency based on detected output from a maximum peaking frequency detection circuit. CONSTITUTION:The control is applied so that the quadratic differential component from the quadratic deferential circuit 6 can go to 0 only in the neighborhood of the peaking frequency based on the detected output supplied to a multiplier 9 and obtained by detecting by the maximum peaking frequency detection circuit. After that, the component is supplied to an adder 11 via an amplifier 10, and is added on a signal via a 1H delay line 2, and is outputted as the signal in which the perpendicular ring contour correction appropriate for sequential scan is applied from an output terminal T2. In such a way, it is possible to reduce the enhancement of the mis-interpolation of the scanning line and to perform the perpendicular ring contour correction with the fine shoot left.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a vertical contour correction circuit for images obtained by progressive scan conversion processing to improve definition accompanying high image quality, and in particular to a circuit for correcting interpolation errors caused by field interpolation. This invention relates to a vertical contour correction circuit that reduces disturbances to images based on .

[Technical Background of the Invention and Problems to be Solved] Conventionally, interlaced scanning has been adopted as a scanning method for video signals in TV receivers, VTRs, etc. in order to reduce screen flickering. There is.

As shown in FIG. 4(a), this is a method in which the field frequency is doubled instead of scanning every other scanning line to lower the pixel density in the vertical direction.

In this interlaced scanning, one complete picture (frame) is scanned by the first field and the second field. Therefore, in the case of NTSC, the number of scanning lines in one field is 262.5, and the number of screens is 30 frames per second.

As mentioned above, in interlaced scanning, the vertical pixel density (number of scanning lines) per screen light is lowered, so the scanning becomes coarse.1. The gaps between the scanning lines become noticeable, and the larger the screen, the more noticeable the gaps become, making the screen difficult to see.

Therefore, in order to eliminate the deterioration of pixel density in the vertical direction due to the above-mentioned interlaced scanning, IDT V (Improved Definition) was developed to significantly improve image quality.
tionTV), etc., a method is used in which the signal in units of one scanning line is compressed twice.

That is, the field frequency (vertical frequency) is kept unchanged, the horizontal frequency is doubled, and the number of scanning lines per field is doubled to 525. As a result, interlaced scanning is converted to progressive scanning (non-incremental scanning) shown in FIG. 4 (bl), and the pixel density in the vertical direction can be increased.

Note that the above-mentioned conversion from interlaced scanning to progressive scanning is realized by writing a signal into the memory for each scanning line and reading it out at twice the writing speed.

FIG. 5 schematically depicts the conversion from the above-described interlaced scanning to progressive scanning, and shows the scanning lines of each field screen viewed from the side on the time axis. As shown in the figure, by inserting interpolated scanning lines (indicated by *) between the original scanning lines (indicated by O), the number of scanning lines per field can be doubled to 525. , it is possible to achieve higher definition than in the case of interlaced scanning. That is, it is possible to pseudo-convert to sequential scanning of 525 lines per field.

In this case, as a method of creating a scanning line signal to be interpolated (an interpolation signal), for example, as shown in the figure, a field interpolation method is used in which an interpolation signal is created from adjacent fields. In this field interpolation, a temporally shifted signal is used as an interpolation signal.

Therefore, in the case of a still image, the interpolated signal described above is exactly the same as the original signal, so there is no problem with the image quality. However, in the case of a moving image, since interpolation is performed using interpolation signals temporally shifted by 1/60 seconds, it appears as if an afterimage or a double image has occurred, degrading the image quality.

Therefore, when an image with the above-mentioned interlaced scanning configuration is sequentially scan-converted by scanning line interpolation from adjacent fields,
Due to a mistake in static and motion discrimination, which distinguishes between still and moving parts of an image, when interpolation is performed on a moving image part using information from adjacent fields as an interpolation signal, stripes with different patterns are generated on every other scanning line. image, which obstructs image quality improvement.

Furthermore, the image affected by the above interference is calculated by peaking frequency = total number of scanning lines / 2 (525 / 2 in the case of NTSC system).
2) When the signal is passed through a 1ine/high vertical contour correction circuit, the frequency of the interference portion matches the peaking frequency of the vertical contour correction circuit, which causes the problem that the interference is further emphasized.

In addition, in the video signal output from a video camera, etc.,
Almost no frequency components corresponding to the above-mentioned interference frequencies are included.

[Purpose of the invention]

The present invention was made in order to solve the above-mentioned problems in the conventional art. An object of the present invention is to provide a vertical contour correction circuit that reduces the emphasis on scanning line interpolation errors caused by the vertical contour correction circuit.

[Summary of the invention]

A maximum peaking frequency detection circuit that detects a peaking frequency portion based on a plurality of scanning lines including a scanning line used for vertical contour enhancement after progressive scan conversion of a video signal, and a second-order differential for contour components for vertical contour enhancement. Based on the detection output from the maximum peaking frequency detection circuit, the second-order differential component from the second-order differentiation circuit becomes 0 only in the vicinity of the peaking frequency, and performs progressive scan conversion. This reduces the emphasis on scanning line interpolation errors.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a block diagram showing an embodiment of a vertical contour correction circuit according to the present invention.

In the figure, 1 is a delay line, which is constructed by cascading IH delay lines 2°3.4, and the output from the IH delay line 2 is supplied to a maximum peaking frequency detection circuit 5, a subtracter 8, and an adder 11. The output from the IH delay line 3 is supplied to the maximum peaking frequency detection circuit 5 and the adder 7, and the output from the IH delay line 4 is supplied to the maximum peaking frequency detection circuit 5. Note that IH here means IH after progressive scan conversion, and the signal after progressive scan conversion is sequentially supplied to the input of the delay line 1 through the input terminal T1.

Reference numeral 5 denotes a maximum peaking frequency detection circuit, which receives as input a plurality of scanning lines including the scanning line used for vertical contour enhancement, and detects the degree of change between lines based on arithmetic processing on the plurality of scanning lines. By this, the peaking frequency portion is detected, and based on this output, the vertical contour correction amount is controlled so as not to affect the impulse, step response, etc.

Reference numeral 6 denotes a second-order differentiation circuit that performs second-order differentiation on contour components for vertical contour enhancement, and an addition circuit that takes the summation output of the signal from the input terminal T and the signal via the IH delay line 2.3. The subtracter 8 is composed of a subtracter 7 and a subtracter 8 which obtains an output by subtracting the signal from the adder 7 and the signal via the IH delay line 2.

9 is a multiplier that controls the vertical contour emphasis output from the second-order differentiation circuit 6 based on the output from the maximum peaking frequency detection circuit 5; 10 is a multiplier that controls the vertical contour emphasis output from the second-order differentiation circuit 6 to an appropriate level; 11 is an amplifier that amplifies and shapes I.
The signal via the H delay line 2 and the vertical contour enhancement output via the amplifier 10 described above are summed together, and a signal that has been properly corrected for vertical contours for sequential scanning is output to the output terminal T2. It is an adder.

FIG. 2 is an example of the maximum peaking frequency detection circuit 5 shown in FIG. 1 described above.

For convenience of explanation, a plurality of signals after sequential scan conversion input to the maximum peaking frequency detection circuit 5 will be described here as a,
b, c, and d, the C signal corresponds to the scanning line input to the input terminal T+, and the b signal corresponds to the IH
The C signal is the output of delay line 2 and corresponds to a scanning line shifted by IH from the C signal, the C signal is the output of IH delay line 3 and corresponds to a scanning line shifted by 2H from C signal, and the C signal is This signal corresponds to a scanning line that is output from the IH delay line 4 and is shifted by 3H from the C signal, and is a signal that corresponds to a plurality of scanning lines including the scanning line used for vertical contour enhancement in the quadratic differentiation circuit 6. .

The maximum peaking frequency detection circuit 5 uses an adder 21 to add the C signal and a C signal shifted by 2H from the C signal based on the above-mentioned input signal after the progressive scan conversion, and the output of the adder 21 and the C signal are added. By subtracting the signal and the b signal that is shifted by IH in the subtracter 22, the output of the subtracter 22 becomes b.
Obtain the second derivative output for the signal.

Further, the subtracter 23 subtracts the b signal which is shifted by IH from the C signal and the C signal which is shifted by 2H from the C signal,
At the output of the subtracter 23, a first-order differential output with respect to the b signal and the C signal is obtained. Further, the adder 24 adds the b signal which is shifted by IH from the C signal and the C signal which is shifted by 3H from the C signal, and the output of the adder 24 and the C signal are subtracted by the subtracter 25. As a result, a second-order differential output with respect to the C signal is obtained as the output of the subtracter 25.

A second differential output for the b signal from the output of the subtracter 22, a first differential output for the b signal and C signal from the output of the subtracter 23, and a second differential output for the C signal from the output of the subtracter 25. are absolute value circuits 26 and 27, respectively.
．． After being converted into an absolute value by 28, it is input to the arithmetic processing section 29.

Then, in the arithmetic processing section 29, a process of detecting the peaking frequency portion is performed based on the above input. In the case of the above specific example, a.

The degree of change between lines based on the input of four scanning lines b, c, and d is detected, and if the repetition frequency between the lines is the highest, that is, the degree of change of the four scanning lines is digital. Considering <1.0.1. O
), when the peaking frequency changes from line to line, it is considered to be the maximum, and at this time, the detection output is 6.
0" is output. In cases other than the above, "1" is output as the detection output.

The signal after sequential scan conversion is supplied to the input terminal T1, and the above-mentioned signals a to d are input to the maximum peaking frequency detection circuit 5, and the peaking frequency is determined based on the degree of change between these lines. When the peaking frequency part is detected, "0" is output as the detection output, and in other cases, "1" is output as the detection output, and the detection output is used as the secondary The signal is supplied to a multiplier 9 interposed between a differentiating circuit 6 and an amplifier 10.

On the other hand, from the output of the second-order differentiation circuit 6, a signal for vertical contour correction is obtained by performing second-order differentiation on the contour component for vertical contour enhancement. Based on the detection output from the maximum peaking frequency detection circuit 5, the vertical contour correction signal obtained by the second-order differentiation circuit 6 is controlled.

That is, the second-order differential component for vertical contour correction from the second-order differentiation circuit 6 is controlled to become 0 only near the peaking frequency detected by the maximum peaking frequency detection circuit 5. Incidentally, FIG. 3 shows the output characteristics of the second-order differential component from the above-mentioned second-order differential circuit 6.

As described above, based on the detection output obtained by detection by the maximum peaking frequency detection circuit 5 supplied to the multiplier 9, the second-order differential component from the second-order differentiation circuit 6 becomes 0 only near the peaking frequency. After being controlled so that the amplifier 10
The signal is supplied to the adder 11 via the IH delay line 2, where it is added to the signal via the IH delay line 2, and the signal is outputted from the output terminal T2 as a signal that has undergone appropriate vertical contour correction for sequential scanning.

In the above embodiment, the detection output from the maximum peaking frequency detection circuit 5 is supplied to the multiplier 9 provided on the output side of the second-order differentiation circuit 6. For example, the amplifier 10 is configured with a voltage-controlled amplifier (VCA) without using a voltage-controlled amplifier, and the detection output from the maximum peaking frequency detection circuit 5 is supplied to the voltage-controlled amplifier, and the output from the second-order differentiator circuit 6 is supplied to the voltage-controlled amplifier. Even with a configuration in which control is performed by the voltage control amplifier based on the output, the same effect as described above can be obtained.

〔effect〕

According to the present invention described above, the peaking frequency portion is detected by a plurality of scanning lines including the scanning line used for vertical contour enhancement by the maximum peaking frequency detection circuit, and based on the detection output from the maximum peaking frequency detection circuit, 2
The configuration is such that the second-order differential component for vertical contour correction obtained by the second-order differentiation circuit is controlled to become 0 only near the peaking frequency, so it does not have any effect on impulse and step responses, etc. , it is possible to perform vertical contour correction while keeping the chute thin without emphasizing interpolation errors of scanning lines in progressive scan conversion.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the vertical contour correction circuit according to the present invention, FIG. 2 is a block diagram showing a specific example of the maximum peaking frequency detection circuit in the embodiment, and FIG. 3 is a block diagram showing a specific example of the maximum peaking frequency detection circuit in the embodiment. FIG. 4 is a diagram showing the output characteristics of the second-order differential circuit; FIG. 4 is a diagram for explaining interlaced scanning and progressive scanning; FIG. 5 is a diagram for explaining the conversion from interlaced scanning to progressive scanning. 5... Maximum peaking frequency detection circuit, 6... Second order differential circuit. Patent Applicant: Pioneer Co., Ltd. ) (a) 7 races tS> ~ Hayaso-111

Claims (1)

[Scope of Claims] A maximum peaking frequency detection circuit for detecting a peaking frequency portion based on a plurality of scanning lines including a scanning line used for vertical contour enhancement after progressive scan conversion of a video signal; and a second-order differential circuit that performs second-order differentiation on the contour component, and the second-order differential component for vertical contour correction output from the second-order differential circuit is peaked based on the detection output from the maximum peaking frequency detection circuit. A vertical contour correction circuit characterized in that the value becomes 0 only near the frequency.