JPH0646390A - Signal conversion device - Google Patents

Abstract

(57) [Abstract] [Purpose] An object of the present invention is to provide a signal conversion device capable of converting a signal conforming to, for example, the NTSC system without degrading the image quality of high-definition broadcasting. An interpolator is provided between a pixel of a current image signal and a first interpolation means for interpolating a current image signal and an image signal of a frame before by a MUSE image signal. The second interpolating means for performing field interpolation, the motion detecting means for detecting a moving area of the image, and the outputs of the first and second interpolating means are mixed based on the output of the motion detecting means. Then, a mixing means for generating a mixed image and a scanning line converting means for converting the number of scanning lines of the mixed image into a number smaller than that of the MUSE method are provided.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a signal converter, and more particularly to a signal converter for converting a MUSE signal into a signal conforming to the NTSC system, for example. As a next-generation television, HDTV (high definition television) so-called high-definition television is being developed. The center of HDTV technology is MUSE (MultipleSub-Nyquist Sampling Encod).
ing) system, which is a band compression technology that enables satellite broadcasting. This technology converts RG, B3 channel signals with 1125 scanning lines, a field frequency of 60 Hz, and a band of 22 MHz into a band of 8.1 MHz, 1 It is to be compressed into a channel signal.

[0002]

2. Description of the Related Art FIG. 11 is a block diagram of a MUSE encoder 1 on the transmitting side and a MUSE decoder 2 on the receiving side in high-definition broadcasting. The encoder 1 includes a still image compression processing circuit 3 that performs still image compression processing, a moving image compression processing circuit 4 that performs moving image compression processing, a motion detection circuit 5 that detects a moving area of an image, and a motion detection circuit 5. It is composed of a mixer 6 that mixes a still image and a moving image based on the output (movement amount). The motion detection is performed based on the temporal change amount of the image, that is, the difference for each image.

In the MUSE system, the band compression method is different between a still image and a moving image. The still image is band-compressed by utilizing the fact that there is no change with time and dividing one picture into four fields for transmission as shown in FIG. On the other hand, in a moving image, since the picture is moving, it is necessary to complete the picture within one field. For this reason, the band compression is performed by slightly lowering the resolution of the picture. Since the human visual characteristics are low sensitivity to moving images, the decrease in resolution is not noticeable.

The MUSE decoder 2 includes a still picture reproduction processing circuit 7 for reproducing a still picture from a MUSE signal, a moving picture reproduction processing circuit 8 for reproducing a moving picture, and a motion detection circuit 9 for detecting a moving area of an image. , And motion detection circuit 9
The mixer 10 is configured to mix a still image and a moving image based on the output (movement amount). That is, in the MUSE decoder 2, by performing the reverse process of the encoder 1,
A high-definition signal having 1125 scanning lines and a field frequency of 60 Hz is reproduced.

By the way, in order to record a high-definition broadcast, a dedicated recording device corresponding to the number of scanning lines of the MUSE system is required, but this is large and extremely expensive, so it is not easily available. . Therefore, there is no choice but to use a recording device (hereinafter, VTR) compatible with a normal television broadcasting system (NTSC system in Japan).

In FIG. 11, reference numeral 11 denotes a scan conversion circuit, which scans the MUSE signal to NTSC.
The signal is converted into a signal which can be recorded in the VTR of the method.
Here, the number of scanning lines and the aspect ratio are different between the MUSE system and the NTSC system, but the aspect ratio is the aspect ratio of the screen and does not affect the image quality. , The number of scanning lines may be converted.

That is, the scanning line conversion unit 11 thins out the number of scanning lines from 1125 to 525 to obtain N
A signal compliant with the TSC system (hereinafter, referred to as NTSC compliant signal for convenience) is generated.

[0008]

However, in such a conventional signal converter, the NUSE based on the MUSE signal is used.
Since the configuration is such that a TSC-compliant signal is generated, there is a problem that the image quality is impaired when the ratio of still images is large. This is because in the MUSE method, one still image (picture) is divided into four fields for transmission, and if the MUSE signal is directly converted into a scan line, an NTSC-compliant signal is generated for each divided field. is there. [Object] Therefore, an object of the present invention is to provide a signal converter capable of converting to a signal conforming to, for example, the NTSC system without deteriorating the image quality of high-definition broadcasting.

[0009]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention interpolates an image signal of the MUSE system between frames of a current image signal and an image signal one frame before. 1 and second interpolation means for performing field interpolation for interpolating between pixels of the current image signal,
Motion detecting means for detecting a moving area of the image; mixing means for mixing the outputs of the first and second interpolation means based on the output of the motion detecting means to generate a mixed image; And a scanning line conversion means for converting the number of scanning lines into a number smaller than that of the MUSE method.

[0010]

In the present invention, the still image is reproduced by the first interpolating means and the moving image is reproduced by the second interpolating means, and the still image and the moving image are output (movement amount) of the motion detecting means. Are mixed by the mixing means based on the above. Then, the mixed image after being mixed is subjected to scan line conversion by the scan line conversion means, and if the number of converted scan lines is, for example, 525 or close thereto, a signal conforming to the NTSC system is reproduced.

That is, since the mixed image after the processing reverse to that of the encoder is subjected to the scanning line conversion, a signal conforming to, for example, the NTSC system can be obtained without deteriorating the image quality of high-definition broadcasting.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a first embodiment of a signal conversion device according to the present invention. In FIG. 1, reference numerals 20 and 21 denote frame memories (one unit has a capacity of 2 fields), 22 denotes a subtractor,
23 is an interframe interpolating section, 24 is a field interpolating section,
Reference numeral 25 is a motion detection unit, 26 is a mixing processing unit, and 27 is a scan conversion unit. Here, the inter-frame interpolating unit 23 uses the MUSE
A still image is reproduced by interpolating a current image signal and a signal of one frame (two fields) before, which is extracted from the frame memory 20, with respect to an image signal of a system (hereinafter, MUSE signal). It functions as the first interpolation means described in the gist of the above. The field interpolating unit 24 reproduces a moving image by interpolating between pixels of the current image signal by a moving image filter, and functions as a second interpolating unit described in the gist of the invention. . Further, the motion detecting unit 25 detects the interval between four fields (two frames) based on the current image signal, the image signal of two fields before extracted from the frame memory 20, and the image signal of four fields before extracted from the frame memory 21. The difference between the pixels is calculated, and this difference is detected as the amount of motion of the image, which functions as the amount-of-motion detecting means described in the gist of the invention. It should be noted that in the motion amount detection unit 25, 2
Approximately calculate the difference between fields (1 frame),
This is sometimes used to detect the amount of movement. The mixing processing unit 26 outputs the output of the inter-frame interpolation unit 23 (still image) and the output of the field interpolation unit 24 (moving image) to the motion detection unit 25.
On the basis of the output (movement amount), and a mixed image (that is, a luminance signal) is reproduced. The mixed image is given, for example, according to the following equation (1).

Mixed image = still image × (1-movement amount) + moving image × movement amount (1) However, the movement amount is a number in the range of 0 or more and 1 or less according to the above equation (1). A mixed image is obtained in which the ratio of moving images is large when the value of the amount is large, and the ratio of still images is large when the value of the amount of movement is small. Scan converter 27
Is to generate a signal conforming to the NTSC system (NTSC conforming signal) by converting the number of scanning lines (1152) of the mixed image into the same as the number of scanning lines of the NTSC system (525). It functions as the described scanning line conversion means. Although thinning processing is easy in the scanning line conversion, if the conversion accuracy is required, for example, a vertical low-pass filter (interpolation filter) including a line memory is used, which is the least common multiple of 1125 and 525.
The number of scanning lines may be increased to 5, and 525 of them may be used.

With the above arrangement, the NTSC-compliant signal is generated from a mixed image of a still image reproduced by interpolating between frames and a moving image generated by field interpolation. Therefore, since such a mixed image includes not only a moving image completed within one field but also a still image divided into four fields is correctly reproduced and included,
Normal VT without compromising the image quality of high-definition broadcasting
A simple NTSC compliant signal applicable to R can be generated.

In this embodiment, only the scanning lines are converted in consideration of the simplification of the configuration, but the aspect ratio may be further converted. In addition, the field frequency is 50 Hz as in the PAL system and SECAM system.
(MUSE method is 60Hz)
For example, it can be dealt with by using the conversion processing by the motion-correction type frame number conversion method together. Therefore, the present invention
The conversion from the USE system to the NTSC system is not the only option.

FIG. 2 is a diagram showing a second embodiment of the signal converting apparatus according to the present invention. A vertical filter 30 is interposed between the mixing processing unit 26 and the scanning line converting unit 27 of the first embodiment. It is an example. The same components as those in the first embodiment are designated by the same reference numerals. The vertical filter 30 is shown in FIG.
As shown in (1), the mixed image from the mixing processing unit 26 is delayed by one line, and the mixed image of one line before extracted from the line memory 30a and the current mixed image are added and halved. It is composed of a computing unit 30b. Therefore, the vertical filter 30 functions as "averaging means for averaging image signals of a plurality of adjacent lines (for example, two lines)" described in the gist of the invention.

According to this embodiment, it is possible to solve the problem of the discontinuity of the oblique lines which occurs with the thinning process of the scanning lines.
That is, in FIG. 4, in a screen in which a plurality of pixels arranged in the order of scanning lines a, b, c, ... Represent an oblique line, continuity of the oblique line is lost if the scanning lines are simply thinned out. However, as shown in FIG. 5, the problem of such discontinuity can be solved by taking the pixel average of two adjacent lines.

The configuration of the vertical filter 30 may be as shown in FIG. That is, the vertical filter 40 is
A first line memory 40a that delays the mixed image from the mixing processing unit 26 by one line, and a second line that delays the mixed image one line before extracted from the first line memory 30a by one line (conveniently two lines). Line memory 40
b, a first arithmetic unit 40c that adds the mixed image of one line before and the current mixed image extracted from the first line memory 40a to 1/2, and 2 extracted from the second line memory 40b The second arithmetic unit 40d that adds the mixed image before the line and the current mixed image to ½, and the mixed image before the one line extracted from the first line memory 40a and the second arithmetic unit 40d The third arithmetic unit 40e that adds the output and halves it and the selector 40f that selects the output of the first arithmetic unit 40c and the output of the third arithmetic unit 40e according to the field signal. However, selector 4
0f selects the output of the first arithmetic unit 40c when the field signal displays an even field, and the third arithmetic unit 40c when the same signal displays a radix field.
The output of e is selected.

The first line memory 40a and the first arithmetic unit 40c function as a first averaging means for averaging the image signals of two adjacent lines, and the first line memory 40a and the second line memory 40c. Line memory 40b, second arithmetic unit 40d and third arithmetic unit 40e function as a second averaging means for averaging image signals of three adjacent lines,
Further, the selector 40f functions as a selection unit that selects the output of the first and second averaging units for each field.

According to the vertical filter 40 having such a configuration, it is possible to solve a problem in performing thinning processing by interlaced scanning, that is, a nonuniform scanning line interval problem (so-called pairing). FIG. 7 is an explanatory diagram of pairing. In the interlaced scanning, the scanning lines constituting one screen are divided into an even field and an odd field to
Scan every second. That is, the scanning lines are changed from a → b → c → d.
After scanning in the order of → e → f ..., The scanning lines between them are scanned in the order of A → B → C → D → E → F. Therefore,
If the thinning-out process is simply performed for the interlaced scanning, for example, b, d, f and A, D, F are generated for each field.
...... is thinned out, so in a single screen, the scan line a
And A, c and C, and e and E are lined up, resulting in non-uniform scanning line intervals.

FIG. 8 is a diagram when the above vertical filter 40 is applied. According to this, the scanning lines a, b, c of the even field after the thinning-out process are the average values of the scanning lines of two adjacent lines, and the scanning lines d of the odd field,
Since e and f are the average values of three adjacent lines, the intervals between the scanning lines can be made uniform and the pairing can be solved. FIG. 9 is a diagram showing a third embodiment of the signal converter according to the present invention,
This is an example applied to the "luminance signal reproduction processing device" described in Japanese Patent Laid-Open No. 3-292077.

In FIG. 9, reference numeral 50 is a luminance signal reproduction processing device described in the publication. This device 50 includes frame memories 51 and 52, a subtractor 53, an interframe interpolating circuit 54, a still image filter 55, a moving image filter 56, and a motion detecting circuit 5.
7, field memory 58, motion vector correction circuit 5
9, mixers 60, 61 and interpolation & clock conversion circuit 6
By including 2, the three clock converters (converters from a low clock rate of 32 MHz to a high clock rate of 48 MHz) that were conventionally required for still images, moving images, and motion detection are interpolated and clocked. Conversion circuit 6
In this configuration, the configuration is simplified, and most of the processing including the mixing processing can be performed at a low clock rate to improve the circuit stability and reduce the circuit scale.

Therefore, the device 50 having the above-mentioned various advantages is provided in the scan conversion unit 63 (the scan conversion unit 2 of the first embodiment).
(Corresponding to 7) is added, the advantage that an NTSC compliant signal can be obtained without degrading the image quality of high-definition broadcasting is added, and thus a more preferable luminance signal reproduction processing device can be obtained. The present invention can also be applied to a type in which a still image filter (low-pass filter) 70 is connected after the interframe interpolating section 23, as shown in the fourth embodiment in FIG. Since the still image whose image quality has been improved by the still image filter 70 is mixed and thinned, the image quality after scanning line conversion can be further improved.

[0024]

As described above, according to the present invention, it is possible to provide a signal converter capable of converting into a signal conforming to, for example, the NTSC system without deteriorating the image quality of high-definition broadcasting because of the above-mentioned configuration.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a first embodiment.

FIG. 2 is a configuration diagram of a second embodiment.

FIG. 3 is a configuration diagram of a vertical filter.

FIG. 4 is a conceptual diagram of a discontinuity problem.

FIG. 5 is a conceptual diagram for solving a discontinuity problem.

FIG. 6 is another configuration diagram of a vertical filter.

FIG. 7 is a conceptual diagram of pairing.

FIG. 8 is a conceptual diagram of a pairing solution.

FIG. 9 is a configuration diagram of a third embodiment.

FIG. 10 is a configuration diagram of a fourth embodiment.

FIG. 11 is a configuration diagram of a conventional example.

FIG. 12 is a conceptual diagram of a MUSE pixel transmission method.

[Explanation of Codes] 23: Interframe Interpolation Unit (First Interpolation Means) 24: Field Interpolation Unit (Second Interpolation Means) 25: Motion Detection Unit (Motion Detection Means) 26: Mixing Processing Unit (Mixing means) 27: Scan converter (scan line converter) 30: Vertical filter (averaging means) 40a: First line memory (first averaging means, second averaging means)
Averaging means) 40b: second line memory (second averaging means) 40c: first calculator (first averaging means) 40d: second calculator (second averaging means) 40e: Third computing unit (second averaging means) 40f: Selector (selecting means)

Claims (3)

[Claims] 1. A first interpolating means for interpolating a current image signal and an image signal of one frame before with respect to an image signal of the MUSE system, and a pixel of the current image signal. Second interpolating means for interpolating field interpolation, motion detecting means for detecting a moving area of an image, and outputs of the first and second interpolating means based on the output of the motion detecting means. And a scanning line converting unit for converting the number of scanning lines of the mixed image into a number smaller than that of the MUSE method. 2. The signal conversion apparatus according to claim 1, further comprising: averaging means for averaging image signals of a plurality of adjacent lines between the mixing means and the scanning line converting means. 3. A first averaging means for averaging image signals of a plurality of adjacent lines, and an averaging method different from the first averaging means between the mixing means and the scanning line converting means. 2. The signal conversion device according to claim 1, further comprising a second averaging means and a selecting means for selecting the output of the first and second averaging means for each field.