JP3168660B2 - Scan conversion method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for scan conversion of an image signal.

[0002]

2. Description of the Related Art At present, conversion from interlaced scanning to progressive scanning is realized by a clear vision receiver. The progressive scanning signal obtained by detecting the amount of motion and performing the following signal processing corresponding to a moving image or a still image. Is switching.

[0005] First, conversion to sequential scanning corresponding to a moving image is realized by the configuration shown in FIG. That is, the input image signal 65 of the interlaced scanning is subjected to a one-dimensional filter in the vertical direction in the filter circuit 14 so that the image signal 6
The pixel values of the phases between the five scanning lines are interpolated and output as a signal 66. As a configuration of the filter circuit 14, for example, signals of two scanning lines are input and an average value in the vertical direction is output. The signal 65 and the signal 66 are input to the double speed conversion circuits 15 and 16, respectively, and converted into double speed signals 67 and 68, respectively. A selection signal 69 that is switched in the selection circuit 17 for each scanning line of the sequential scanning.
Switches between the signal 67 and the signal 68 to output the sequential scanning signal 70. The signal 70 has the value of the signal 65 itself at the phase coincident with the scanning line position of the signal 65, and has the output value of the filter circuit 14 at the phase between the scanning lines of the signal 65. Assuming that the vertical signal band that can be expressed by the progressive scanning signal is f1, the filter characteristic of the scan conversion formed by the above processing is, for example, f1 / 2 as shown in FIG.
Becomes a cutoff value.

In many cases, conversion to sequential scanning corresponding to a still image is performed by changing only the function of the filter circuit 14 in the configuration of FIG. 8 to outputting the pixel value one field before as a signal 66. Has become.

[0005]

In the above-mentioned prior art, the sharpness at the time of switching between a still image and a moving image greatly changes because the difference between the image quality at the time of a moving image and the image quality at the time of a still image becomes large. There are drawbacks. Further, if the switching from the still image processing to the moving image processing or from the moving image processing to the still processing frequently occurs, there is a disadvantage that the image is deteriorated due to flickering.

An object of the present invention is to provide a scan conversion method capable of alleviating such disadvantages of the conventional system and improving the image quality of an image signal converted into a progressive scan.

[0007]

SUMMARY OF THE INVENTION The first scan conversion of the present invention
The method is a scan conversion method for converting an interlaced original image signal into a sequential scan. When a vertical signal band that can be represented by the scan line interval of the progressive scan is f1, a signal between the original image signals is provided. Is generated and added to the original image signal .
The gain is 0.8 or more and less than 1.0, and the frequency f2 (f
By applying a vertical reduction pass type filter having a gain of 0.5 at 1/2 <f2 <f1), the signal is converted into a progressively scanned image signal.

[0008] The second scan conversion method of the present invention, interlaced be the original image signal of the scanning a scan conversion method for converting sequential scanning signal generated by the original image signal to between the original image signal
By adding the signal to the signal, the sequentially scanned signal is separated into a horizontal low-frequency component and a horizontal high-frequency component, and the latter has a wider pass band in the vertical / time domain than the former. The signal is converted into a progressively scanned image signal by applying a band-pass filter.

A third scan conversion method of the present invention is a scan conversion method for converting the sequential scanning of the original image signal of interlaced scanning, prior to detecting the motion amount of the image from the original image signal
A motion determination of the original image signal is performed.
A progressive scan signal obtained by performing the scan conversion method according to claim 1 or 2 is used as a progressive scan signal for a moving image as a signal after scan conversion from the original image portion .

[0010]

According to the first scan conversion method of the present invention, a signal obtained by performing zero interpolation on a signal of interlaced scanning and sequentially scanning is applied to a scanning line of progressive scanning as shown in FIG. By applying a vertical reduction pass filter having a pass band (f2) wider than 垂直 of the vertical signal band (f1) that can be expressed by an interval, the signal is converted into a progressively scanned image signal. The vertical signal band that can be expressed in the field by the original signal of the interlaced scanning is f1 / 2, and it is desirable to effectively use the signal band up to f1 / 2. However, in the filter of the related art, the roll-off value is set to 0. Therefore, it is inevitable that a part where the gain becomes 1 or less appears even in the signal band of f1 / 2 or less. In the present invention, by making the pass band of the filter wider than f1 / 2, many distortion components of f1 / 2 or more are included, but the gain of the signal band of f1 / 2 or less is effectively reduced without greatly attenuating. It can be used. Further, since this distortion component visually works in the direction of improving the sharpness, it is possible to select the pass band of the filter so as not to cause large image quality deterioration. Therefore, according to the present invention, the image quality of a moving image is improved as compared with the conventional method.

In the second scan conversion method of the present invention, a signal component having a higher frequency in the horizontal direction is applied to a signal obtained by performing zero interpolation on a signal of interlaced scanning and sequentially scanning the signal. Is applied to a low pass filter having a wide pass band to convert the image signal into a progressively scanned image signal. In general, the distortion component of f1 / 2 or more is more visually conspicuous as the horizontal low frequency component is. Therefore, by setting the pass band of the filter narrower for low-frequency components in the horizontal direction to remove visually degraded components, and by setting the pass band of the filter wider for higher-frequency components in the horizontal direction, comparison is made with conventional moving images. As a result, the image quality can be improved.

A third scan conversion method according to the present invention detects a motion amount of an image from an original image signal of the interlaced scan, and converts a sequential scan signal obtained by the first or second scan conversion method into a moving image. Used as a progressive scanning signal. As described above, the progressive scan signal obtained by the first or second scan conversion method of the present invention has an improved image quality as compared with that of a conventional moving image, and therefore, the image quality of the progressive scan signal with a still image progressive scan signal is improved. The difference is smaller. Therefore, as compared with the related art, it is possible to reduce deterioration in image quality due to switching from still image processing to moving image processing or from moving image processing to still image processing.

[0013]

Next, an embodiment of the present invention will be described with reference to FIGS.

First, an embodiment of the first scan conversion method of the present invention will be described. FIG. 5 is a block diagram showing a basic configuration of a circuit for implementing the scan conversion method . The image signal 80 of the interlaced scanning is input to the double speed conversion circuit 18 and
The signal is converted to twice as fast and output as a signal 81 at intervals of every other scanning line in the sequential scanning. In the selection circuit 19,
The signal 81 and the zero signal are switched by a selection signal 84 that is switched for each scanning line of the sequential scanning, and a zero interpolation signal 82 is obtained. The zero interpolation signal 82 is a sequential scanning signal in which a zero signal and a 2 × speed input image signal are alternated for each scanning line.
As an example, a filter having the characteristics shown in FIG. 7 is applied to the zero interpolation signal 82 in the vertical direction to perform interpolation processing, and a sequential scanning signal 83 is output. In the characteristic of FIG. 7, f1 /
The gain of No. 2 is 0.8 or more, and the degree of attenuation is smaller than the characteristic of the conventional method shown in FIG.

FIG. 6 shows an example of the double speed conversion circuit 18. The input signal 71 is input to the storage circuits 11 and 12. The write control signals 72 and 74 are input to the storage circuits 11 and 12, respectively. For each scanning line of the interlaced scanning, for example, the signal of the odd-numbered scanning line is sent to the storage circuit 11, and the signal of the even-numbered scanning line is sent to the storage circuit 12 Is stored. The storage circuits 11 and 12
When one of them is in the write state, control is performed by the write control signals 72 and 74 and the read control signals 73 and 75 so that the other is in the read state. The double speed conversion is realized by processing the read operation at twice the speed of the write operation. The signals 76 and 77 read at double speed from the storage circuits 11 and 12 are sequentially scanned by the selection circuit 13 for one time.
A double speed signal 79 is obtained by switching and outputting a selection signal 78 which is switched for each scanning line.

FIG. 4 shows an example of the filter circuit 20. The input signal 63 is input to the multiplier g1 and the storage circuit d2.
The output of the storage circuit dj is input to the multiplier gj and the storage circuit dj + 1. (J = 2, 3,..., N). Here, it is assumed that the storage circuit dj has a FIFO configuration for one scanning line. The output of the multipliers g1, g2,..., Gn is added by the adder 10 to become the filter output 64. Each multiplier outputs a product obtained by multiplying the input signal by a fixed constant (filter coefficient). The configuration in FIG. 4 forms an n-tap vertical filter.

The above is the description of the embodiment shown in FIG.
FIG. 5 shows a configuration in which the filter is applied after actually performing the zero interpolation processing, but the first scan conversion method can also be realized by the scan conversion circuit 100 shown in FIG. That is, in the configuration of FIG. 1, a filter circuit 1 for obtaining an output having a phase coincident with the scanning line position of the interlaced scanning and a filter circuit 2 for obtaining an output of a phase between the scanning lines are operated in parallel. First, the image signal 50 of the interlaced scanning is input to the filter circuits 1 and 2. The filter circuit 1 obtains an output of a phase that matches the scanning line position of the image signal 50, and the filter circuit 2 obtains an output of a phase between the scanning lines. Next, the filter output signal 51,
52 is double-speed converted in double-speed conversion circuits 3 and 4 to obtain double-speed signals 53 and 54. The double speed signals 53 and 54 are switched by the selection circuit 5 by a selection signal 55 which is switched for each scanning line of the sequential scanning to obtain an image signal 56 of the sequential scanning.
However, the vertical signal band that can be expressed by the progressive scanning signal is f1
In this case, the overall characteristics of the filter circuits 1 and 2, that is, the characteristics of the interpolation filter in the scan conversion circuit 100, are set so that the pass band is wider than f1 / 2, for example, as shown in FIG.

Next, an embodiment of the second scan conversion method of the present invention will be described. Here, for example, 2 in the horizontal direction
A description will be given of the case of dividing into a plurality of bands. Figure 2 shows the scan conversion method
FIG. 2 is a block diagram illustrating a basic configuration of a circuit that performs the method .
The image signal 57 of the interlaced scanning is first divided by the band dividing circuit 6 into two bands in the horizontal direction. Band division may be performed by a known conventional technique. The horizontal low-frequency component is defined as a signal 58 and the high-frequency component is defined as a signal 59. The signals are input to the scan conversion circuits 7 and 8, respectively, and are sequentially converted to scan. The configuration of the scan conversion circuits 7 and 8 may be the same as the configuration of the scan conversion circuit 100 in FIG. However, only the filter characteristics are set so that the pass band of the filter of the scan conversion circuit 7 is narrower than the pass band of the filter of the scan conversion circuit 8. By doing so, it is possible to remove the distortion component in the horizontal low-frequency component where interference is conspicuous, and to improve the sharpness in the horizontal high-frequency component.

The scan conversion circuit 7 which handles horizontal low frequency components
May be realized by the configuration shown in FIG. Further, the scan conversion circuits 7 and 8 may be realized by a two-dimensional filter in a vertical / time space.

Next, an embodiment of the third scan conversion method of the present invention will be described. Here, as an example, a case will be described in which the sequential scan conversion at the time of moving image is realized by the first scan conversion method described with reference to FIG. 1, but it may be realized by the second scan conversion method . FIG. 3 is a block diagram showing a basic configuration of a circuit for implementing the scan conversion method . The image signal 89 of the interlaced scanning is input to the scan conversion circuits 21 and 22 and the motion detection circuit 23. In the scan conversion circuit 21,
The moving image time sequential scanning signal 85 is generated in exactly the same configuration as the scanning conversion circuit 100 of FIG. The scan conversion circuit 22 has exactly the same circuit configuration as that of the prior art described with reference to FIG. 8 except for the filter circuit 14, and the function of the filter circuit 14 is changed to a function of sequentially scanning by inserting a pixel value one field before. Then, a still image time sequential scanning signal 86 is generated. The motion detection circuit 23 calculates the absolute value of the one-frame difference
7 is output. In the mixing circuit 24, the moving image time sequential scanning signal 85 and the still image time sequential scanning signal 86 are mixed by the motion amount signal 87 to output a sequential scanning signal 88. By doing so, the image quality of a still image is improved as compared with the first or second scan conversion method . However, the difference in image quality between a still image and a moving image is small as compared with the related art.

[0021]

As described above, according to the present invention,
It is possible to improve the image quality at the time of moving images, and to further reduce deterioration in image quality due to switching from still image processing to moving image processing or from moving image processing to still image processing.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a basic configuration of one embodiment of a first scan conversion method of the present invention.

FIG. 2 is a block diagram showing a basic configuration of one embodiment of a second scan conversion method of the present invention.

FIG. 3 is a block diagram showing a basic configuration of one embodiment of a third scan conversion method of the present invention.

FIG. 4 is a diagram showing a configuration example of a filter circuit in one embodiment of the present invention.

FIG. 5 is a block diagram showing a basic configuration of one embodiment of the first scan conversion method of the present invention.

FIG. 6 is a diagram illustrating a configuration example of a double speed conversion circuit according to an embodiment of the present invention.

FIG. 7 is a diagram illustrating filter characteristics of a scan conversion circuit according to an embodiment of the present invention.

FIG. 8 is a block diagram showing a basic configuration of a conventional scan conversion method .

FIG. 9 is a diagram illustrating an example of a filter characteristic in a conventional scan conversion circuit.

[Explanation of symbols]

 1, 2, 14, 20 Filter circuit 3, 4, 15, 16, 18 Double speed conversion circuit 5, 13, 17, 19 Selection circuit 6 Band division circuit 7, 8, 21, 22, 100 Scan conversion circuit 9, 10 Addition Unit 23 motion detection circuit 24 mixing circuit 11, 12, d2, ..., dn storage circuit g1, g2, ..., gn multiplier

Claims (3)

(57) [Claims] 1. A scanning conversion method for converting an original image signal of interlaced scanning into sequential scanning, wherein when a vertical signal band that can be expressed by a scanning line interval of the sequential scanning is f1, the interval between the original image signals is reduced. Is generated at the frequency f1 / 2, the gain is 0.8 or more and less than 1.0, and the frequency f2
A scan conversion method characterized by applying a vertical reduction pass filter having a gain of 0.5 at (f1 / 2 <f2 <f1) to convert the signal into a progressively scanned image signal. 2. A scanning conversion method for converting an original image signal of interlaced scanning into sequential scanning, wherein a signal between the original image signals is converted.
A signal that is sequentially scanned by generating a signal and adding it to the original image signal is separated into a low-frequency component in the horizontal direction and a high-frequency component in the horizontal direction.
A scan conversion method characterized by applying a low-pass filter having a wider pass band in the time domain to convert the image signal into a progressively scanned image signal. 3. A scan conversion method for converting an interlaced original image signal into a sequential scan, wherein a motion amount of an image is detected from the original image signal to determine whether the original image signal is still or not.
After the scan conversion from the original image part determined to be the moving part
The scan conversion method according to claim 1 or 2 is implemented as
A motion-adaptive scan conversion method characterized in that a progressive scan signal obtained by performing the process is used as a progressive scan signal for a moving image.
Law .