JPH06141291A - Scanning line number converter for picture signal - Google Patents

Abstract

(57) [Abstract] [Purpose] To improve the conversion image quality for moving images in a scanning line number conversion device. A motion vector generation circuit 3 that outputs a motion amount of an image in an input image signal of interlaced scanning as a motion vector, and motion compensation memories 10 to 12 that perform motion compensation of a delay amount of the input image signal according to the motion vector, 1H delays 13 to 15 for delaying an input image signal, a weighted averaging circuit 16 for weighted averaging the output signals of the 1H delays 13 to 15 and the output signals of the motion compensation memories 10 to 12, and a delay amount according to a motion vector. An interpolation selection determination circuit 9 that determines the weight in the weighted average circuit based on the motion-compensated inter-frame difference signal that has been motion-compensated, and a buffer memory 17 that converts the number of scanning lines from the weighted average circuit 16 and extracts an image signal. Get

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scanning line number converter for image signals.

[0002]

SUMMARY OF THE INVENTION The present invention provides virtual motion compensation in a scanning line number conversion device which scan-converts a television image signal of 2: 1 interlaced scanning and outputs a television image signal having a different number of scanning lines. By performing the sequential scanning conversion of the mold and then converting the number of scanning lines, unnecessary folding interference in the moving image is removed, and the conversion image quality of the moving image is improved.

[0003]

2. Description of the Related Art As a conventional scanning line number converting device, there are, for example, the following (1) and (2) in which the device of (1) is a motion adaptive type.

(1) "Scanning line number conversion system" Japanese Patent Application No. 58
No. 174325 (Applicant: Japan Broadcasting Corporation, Inventor: Tanaka, Nishizawa) (2) “Number of scanning lines / sequential scanning conversion method” Japanese Patent Application No. 61-
No. 71225 (Applicant: Japan Broadcasting Corporation, inventors: Tanaka, Omura, Kurita,
Ninomiya, Nishizawa)

[0005]

Although the conventional scanning line number conversion device has a sufficient conversion image quality for a still image, it is based on the 2: 1 interlaced scanning of the input signal, as will be described later in detail. Due to the folding back, an unnatural folding signal component is generated for a moving image.
Therefore, the conversion image quality for moving images is not always sufficient.

That is, the principle of the conventional scanning line number conversion method will be described with reference to FIG. FIG. 2 shows a situation of scanning an image in a time (t) -vertical (y) coordinate system. White circles in FIG. 2 indicate positions where scanning lines exist. The numbers 1, 2, 3, ... Attached to the scanning lines are the scanning line numbers in the input signal, and the numbers 1 ', 2', 3 ', ... Are the scanning line numbers in the output signal. In addition, D. C. (= Don't C
are) indicates that the signal content of the scan line is invalid. The conversion ratio of the number of scanning lines is 5: 3 (for example, conversion from 1125 lines to 675 lines).

The scanning line number conversion is performed as follows. First, scanning lines are interpolated from an input signal on the left side of FIG. 2 by an interpolation filter in the vertical direction, and scanning lines (1 ', 2', 3 ', 4') for output signals are created. At this time, the filters for forming the scanning lines 1 ', 2', 3'are filters having the same frequency characteristics but different sampling phases,
A circuit for realizing it is a conventional example (1) and (2).
In detail. In FIG. 2, scanning lines 1 ', 2', 3 ', and 4'for output signals still have the same scanning as the input signals. Therefore, thinning of scanning lines and conversion of vertical scanning are performed by a buffer memory or the like. Done and create the output signal. At this time, as is clear from Document (2), there is no great change in the above operation regardless of whether the output signal is 2: 1 interlaced scanning or sequential scanning.

In the conventional scanning line number conversion, when performing the above-mentioned interpolation, the moving image is scanned from the scanning line in the field (in FIG. 2, the scanning line in the field at t = 0 on the left side of the drawing). However, the input signal is 2: 1 interlaced scanning, and the vertical information is only half of the frame image,
Therefore, this intra-field interpolation cannot perform interpolation with a high vertical resolution, and only in a still image, the field memory is used to virtually convert to sequential scanning using the scanning lines of the previous field as shown by the dotted line in FIG. Since, the interpolation for the number of scanning lines was performed. However, this was limited to still images.

Therefore, an object of the present invention is to improve this point and to provide a scanning line number conversion apparatus for an image signal which can obtain a sufficiently converted image quality even for a moving image.

[0010]

In order to achieve the above object, the present invention provides a motion vector generating circuit for outputting a motion amount of an image in an input image signal of interlaced scanning as a motion vector, and a delay amount of the input image signal. , A motion compensation field delay circuit that has been motion-compensated according to the motion vector, a delay circuit that delays the input image signal, and a weighting that performs weighted averaging on the output signal of the delay circuit and the output signal of the motion compensation field delay circuit. An averaging circuit, and a circuit that determines a weight in the weighted averaging circuit based on a motion-compensated inter-frame difference signal in which a delay amount is motion-compensated according to the motion vector;
A circuit for converting the number of scanning lines from the weighted average circuit to extract an image signal is provided.

[0011]

According to the present invention, the number of scanning lines is converted after virtually performing motion compensation type progressive scanning conversion on an input image of interlaced scanning. As a result, it is possible to remove unnecessary aliasing interference in the moving image and improve the conversion image quality of the moving image.

[0012]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 shows the configuration of a scanning line number conversion apparatus according to an embodiment of the present invention.

In FIG. 1, an input signal of the present apparatus is an image signal having 1125 scanning lines / field frequency 60 Hz / interlace ratio 2: 1, and an output signal is 525 lines / field frequency 60 Hz / interlace ratio 2: 1 image signal. That is, this device converts only the number of scanning lines among the basic scanning parameters of the image signal, and the conversion ratio is 1125: 525 = 15: 7.

The input signal of this apparatus is first input to the motion vector detection circuit 1. The motion vector detection circuit 1 detects the motion amount of the image of the input signal as the motion vector V ₀ . For this detection, various motion vector detection techniques already proposed can be used as they are. If the motion vector is given from the outside, it may be received. V ₀ is input to the motion vector value correction circuit 2 and its value is slightly modified so that the motion vector V (V
_x , V _y ). The content and meaning of the modification will be described later. Here, V is actually 2 of V _x and V _y .
It consists of two signals. V _x represents the horizontal component of the motion, and the unit is (pixel / field). V _y represents the vertical component of the motion, and the unit is ((in frame) scan line / field). This device can operate even if the value of V is updated in each pixel, in each pixel block of a certain size, or in each field. These circuits 1 and 2 constitute the motion vector generating circuit 3 as a whole.

The input signals are also (565H + V), respectively.
It is input to the motion compensation memories 10, 11 and 12 having delay amounts of (564H + V) and (563H + V). Here, H represents one line in the field. V is the motion vector. For example, the delay amount of (563H + V) is expressed as follows in terms of the number of pixels. The number of pixels on one line is N

[0017]

[Equation 1]

[0018] The other delay amounts are similarly obtained. Here, the polarities of V _x and V _y are V _x > 0 and V _y > 0 when the image moves to the upper right with time. The output of the memory 10 is a signal x _-2 , the output of the memory 11 is x ₀ , and the output of the memory 12 is x ₂ . These are input to the weighted average circuit 16.

The input signal is also a 1H delay 13,1
It is input to the cascade connection circuits of 4, 15. Here, it is assumed that the input signal of the device is x _-3 , the output of the delay 13 is x _-1 , the output of the delay 14 is x ₁ , and the output of the delay 15 is x ₃ . These are also input to the weighted average circuit 16.

In the apparatus of FIG. 1, the image quality deterioration in the moving image at the time of virtual progressive scan conversion is solved by motion-compensating the field delay amount in the memories 10 to 12 according to the motion vector V. For example, when the vertical motion of the image is V _y = 2, the scanning lines of a, b, and c of FIG. 3 are delayed by the motion compensation memories 10 to 12 of FIG. 1 to delay x ₂ , x ₀ , and x _−. Outputs ₂ and weighted average circuit 1
Sequential scanning signals x _{3 to} x _-3 are input to 6. The display method of FIG. 3 is the same as that of FIG. 2, and the operation after interpolation is the same as the conventional method (details will be described later). As described above, in the apparatus of FIG. 1, even if an image moves, it can be converted into progressive scanning without using a vertical filter, so that the converted image quality of a moving image is good. That is, high resolution and high image quality can be obtained. This situation also applies to the horizontal motion component. In addition,
Since V _x = V _y = 0 in a still image, inter-field interpolation for a conventional still image is also included in the motion compensation interpolation operation.

By the way, FIG. 3 shows only when V _y is an even number, but when V _y is an odd number, there is no scanning line corresponding to sequential scanning one field before, so that motion compensation interpolation cannot be performed. . Therefore, the motion vector value correction circuit 2 of FIG. 1 corrects the motion vector value in the vertical direction by the following algorithm. If the vertical and horizontal motion vectors detected by the motion vector detection circuit are V _y0 and V _x0 , respectively,

[0022]

[Equation 2]

[0023]

Equation 3] _{V x = V x0 ... (3} ) i.e., for V _y0 are if V _y0 is odd are rounded to a small even number of more absolute value V _y0. This is because the image quality is generally better in the under-compensated state than in the over-compensated state when the motion compensation is not accurate. With respect to the horizontal motion component, it is not necessary to modify V _x0 because there is no special situation based on the interlaced scanning as described above.

The weighted average circuit 16 constitutes a seventh-order interpolation filter, and has the above-mentioned x _i (i is an integer and -3≤i≤
3) is multiplied by a weight (coefficient) α _i , then added and output. Ie

[0025]

[Outer 1]

At this time, the value of the coefficient α _i changes depending on the signal K described later and the scanning line number within the frame or within the field. The output of the weighted average circuit 16 is input to the buffer memory 17. Here, by reading / writing a signal according to the scanning line number in FIG.
Converts the vertical scan in the image to 525/60 /
Create a 2: 1 output signal of the device.

The input signal of this device is also (525H + 2
V) is input to the motion compensation memory 4 having the delay amount. The operation of No. 4 is the same as that of the memories 10 to 12 except that the motion compensation amount is twice the motion vector V, and the delay amount thereof is obtained in the same manner as the equation (1). The subtracter 5 takes the difference between the input signal of this device and the output of the memory 4 and outputs it. The output of the subtractor 5 is the motion compensation interframe difference signal. The absolute value circuit 6 outputs the absolute value of the output of the subtractor 5. The K decision circuit 7 decides the signal K based on the output of the absolute value circuit 6. Here, the value of K is, for example, 0 ≦ K ≦ 1. The number of values that K can take within this range depends on the condition of the weighted average circuit 16. For example, the coefficient α _i
However, if three types can be changed with respect to K, the value that K can take is three types, for example, K is 0, 0.5, or 1. The content of the K decision circuit 7 may be a quantizer which simply makes K a large value if the output value of the absolute value circuit 6 is large, or various methods found in conventional image motion detection methods. May be included. The output of the K determination circuit 7 is input to the weighted average circuit 16 as a signal K through a 1H delay 8 for phase matching with x _i . The phase of the signal K is aligned with the signal x _-1 . Each of these configurations 4 to 8 constitutes the interpolation selection determination circuit 9 as a whole.

The scanning line number conversion according to this embodiment uses the memories 10 to 12, the 1H delays 13 to 15, the motion vector generation circuit 3, the interpolation selection determination circuit 9, the weighted average circuit 16, and the buffer memory 17 as described above. Since a 2: 1 interlaced scanning signal is virtually subjected to motion compensation type progressive scanning conversion and then interpolation for conversion of the number of scanning lines is performed, high resolution and It is possible to perform image quality conversion.

Scan line number conversion time including the embodiment of FIG.
Vertical spectra are shown in FIGS. 4 and 5. 4 and 5, the horizontal axis represents the time frequency f (Hz), and the vertical axis represents the vertical spatial frequency ν (cph). FIG. 4 (a) is the spectrum of the image considered below,

[0030]

[Outside 2]

[0031]

[Outside 3]

A carrier for spatiotemporal sampling by interlaced scanning. In the figure, the original spectrum and the folding spectrum of time sampling by the field are shown by solid lines, and the folding by interlaced scanning is shown by dotted lines. Further, FIG. 6B shows a signal spectrum when the same image is picked up by the camera of the system having 525 scanning lines. In the figure (a), V _y = 2 (1125 scanning lines / field), but in the figure (b),

[0033]

[Equation 4]

Can be considered as

FIG. 3C shows the interpolation characteristic of the conventional still image interpolation described in FIG. The shaded area in FIG. 6C is the stop band of the interpolation filter, and the signal spectrum in this area is cut. Scanning conversion of the signal remaining in the pass band to 525/2: 1 yields the spectrum of FIG. As shown in FIG. 6D, in addition to the original spectrum (solid line) of which the length is shortened (resolution is reduced) and the spectrum from the interlaced carrier X (dotted line), −60 ≦
It can be seen that an unnatural spectrum is generated in the region of f ≦ −30 and 0 ≦ f ≦ 30. This is caused by the folded spectrum of the interlace remaining in the pass band of FIG. Also, this spectrum is ν of the original image
Is caused by the mid-range component of. Due to this spectrum, in the conventional conversion, in addition to the reduction in the vertical resolution of the image, unnatural image quality disturbance, for example, an unnatural and noticeable interline flicker at a horizontal edge of the image or the like occurs.

Similarly, the conventional interpolation characteristic for a moving image is shown in FIG. 6E, and the scanning line number conversion result is shown in FIG. Also in this case, in addition to the resolution of the original spectrum being lowered, an unnatural folded spectrum is also generated. However, in this case, this unnatural spectrum is caused by the ν high frequency component of the original image. That is, the ν high frequency component of the original image is output after the value of ν is converted. However, with regard to image quality, unnatural interlace interference also occurs as the resolution decreases, and image quality also deteriorates.

On the other hand, according to the apparatus of FIG.
It is possible to realize the interpolation characteristic as shown in (g), and it is possible to obtain an output signal spectrum equivalent to that shown in FIG. 4B directly imaged by the scanning line 525 system as shown in FIG. is there. Further, when interlace interference is noticeable in the images of FIGS. 4B and 5H, the interpolation characteristic is consciously set to a narrow band with respect to ν as shown in FIG. As shown in (j), it is possible to obtain an image that does not interfere with the ν low range that is visually noticeable. in this way,
According to the present apparatus, in addition to being able to obtain a scan conversion output with high image quality without unnatural interference, depending on the selection of characteristics, an image with extremely high image quality with less interference than an ordinary camera with 525 scanning lines can be obtained. It is also possible to obtain

The control of the coefficient α _i by the signal K in the apparatus of FIG. 1 is for coping with the case where motion compensation causes an error due to erroneous detection of a motion vector or the like. = 1, the characteristics of FIG. 5 (g), K = 0, the characteristics of FIG. 4 (e), K = 0.5.
In the case of, the characteristic may be an intermediate value between the characteristic of FIG. 5 (g) and the characteristic of FIG. 4 (e (for example, the average characteristic of both).

Another embodiment of the present invention is shown in FIG. Input / output signals are the same as in FIG. The circuit configuration differs from that of FIG. 1 in that instead of the motion compensation memories 10, 11 and 12 of FIG. 1, a 547H delay 20 and motion compensation memories 21 and 1H of FIG.
That is, the delays 22 and 23 are used. The other parts of the circuit are the same in contents and operation as in FIG.

The input signal goes through a 547H delay 20 and
Motion compensation memory 21 having a delay amount of (16H + V)
Motion compensated by. If | V | ≦ 16H, the operation including the 547H delay 20 and the motion compensation memory 21 is equivalent to the operation of the motion compensation memory 12 of FIG. Since this is usually | V | ≦ 16H in a normal image, the motion compensation memory 12 is replaced with the 547H delay 20 and the motion compensation memory 21.
It is intended to reduce the delay size of the expensive motion compensation memory by dividing into two and to realize the device economically. The output of the motion compensation memory 21 is 1H delay 2
Input to 2,23 cascade connection. Motion compensation memory 2
The outputs of the 1 and 1H delays 22 and 23 are x _-2 , x ₀ , and
the x _2. That is, each of the configurations 20 to 22 substitutes the motion compensation memory 11 of FIG. 1, and each of the configurations 20 to 23 substitutes the motion compensation memory 12. This is another way to save expensive motion compensation memory.

FIG. 7 shows an operation example of the apparatus shown in FIG. The notation of FIG. 7 is the same as that of FIG. 7 is different from FIG. 3 in that x ₀ and x ₂ are not created from the scanning lines b and c but are created from x ₋₂ . This is equivalent to the operation of the apparatus of FIG. 1 when the motion vectors for interpolating x ₋₂ , x ₀ , x ₂ are equal as shown in FIG. However, when the motion vector for a certain scan line and the scan line adjacent thereto are different, the operation of the apparatus of FIG. 6 is different from that of FIG. 1, and there is a possibility that the image quality may be deteriorated due to a motion compensation error. However, depending on the method of generating a motion vector and the type of image, there is a high possibility that the apparatus of FIG. 6 will be sufficient in terms of image quality. In such a case, the device can be economically realized by the configuration of FIG.

The present invention can be applied to a system having a scanning line number different from that of the embodiment for both input and output, in addition to the examples described above.
Further, it can be used not only for down conversion like 1125 → 525 in this embodiment but also for up conversion like 525 → 1125. Further, the output signal may be progressive scanning. Furthermore, the motion compensation may be performed by a signal before and after one field of the signal of interest, and it is also possible to increase the number of motion vectors capable of motion compensation such as interpolated signals in the motion compensation interpolation.

[0043]

According to the present invention, the motion-compensated progressive scanning conversion is virtually performed on the input image signal of the interlaced scanning and then the number of scanning lines is converted, so that unnatural aliasing of interference in a moving image is prevented. Can be prevented and the conversion image quality for moving images can be improved.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a diagram showing an operation of a conventional scanning line number conversion device.

FIG. 3 is a diagram showing an operation example of the apparatus of FIG.

4 shows a time-vertical spectrum illustrating the operation of the device of FIG.

FIG. 5 is a diagram similarly showing a time-vertical spectrum.

FIG. 6 is a block diagram showing another embodiment of the present invention.

FIG. 7 is a diagram showing an operation example of the apparatus of FIG.

[Explanation of symbols]

 3 Motion Vector Generation Circuit 9 Interpolation Selection Judgment Circuit 10, 11, 12 Motion Compensation Memory 13, 14, 15 1H Delay 16 Weighted Average Circuit 17 Buffer Memory

Claims (1)

[Claims] 1. A motion vector generation circuit for outputting a motion amount of an image in an interlaced scanning input image signal as a motion vector, and a motion compensation field delay circuit for motion compensation of a delay amount of the input image signal according to the motion vector. A delay circuit for delaying the input image signal, a weighted average circuit for performing a weighted average on the output signal of the delay circuit and the output signal of the motion compensation field delay circuit, and motion compensation of the delay amount according to the motion vector. An image comprising a circuit for determining a weight in the weighted average circuit based on the motion-compensated inter-frame difference signal, and a circuit for converting the number of scanning lines from the weighted average circuit to extract an image signal. Signal scanning line number converter.