JPH07222147A - Interpolation processing circuit for sub-sampled video signal - Google Patents

Abstract

PURPOSE:To provide video signals without the foldover distortion of a spatial frequency band regardless of the kind of a low-pass filter provided in a sub- sampling circuit on a video signal transmission side in an interpolation processing circuit on a video signal reception side. CONSTITUTION:The video signals vertically or horizontally filtered, band-limited and sub-sampled in a state where inter-frame offsetting is performed in a zigzag stripe shape in the sub-sampling circuit are passed through a transmission system 4 and transmitted to the reception side. The received video signals are zero- interpolated in a zero interpolation part 12. A selector 15 selects the video signals interpolated by a vertical filter 13 when the sub-sampling circuit uses the vertical filter and selects the video signals interpolated by the vertical and horizontal filters 13 and 14 when the sub-sampling circuit uses a two-dimensional filter corresponding to the changeover of a changeover switch by an operator watching a cathode-ray tube for picture reproduction. Thus, improved pictures for which the horizontal straight line of reproducing pictures is not a broken line are reproduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an interpolating circuit for a sub-sampled video signal, that is, a first video signal which is originally sampled in a square lattice form, is band-limited by a pre-filter, and is then staggered. The present invention relates to an improvement of an interpolation processing circuit in a moving area of a second video signal obtained by sub-sampling in a lattice-shaped offset between frames.

[0002]

2. Description of the Related Art Conventionally, as a band compression technique for video signals,
There is sub-sample technology. This sub-sampling technology is a technology for band-compressing by reducing the amount of information by repeating sampling processing of the original sampled digital video signal, and the video signal band-compressed by this sub-sampling technology is transmitted narrowly. In the band, it is transmitted from the transmission side such as a television broadcasting station to the television receiver side through the transmission system.

FIG. 13 shows the structure of the transmitting side of a television broadcasting station or the like.

In FIG. 1, reference numeral 70 denotes an A / D for analog / digital converting a video signal from a television camera or the like.
The conversion circuits 71 and 72 are the A / D conversion circuits 70, respectively.
A static area pre-filter and a moving area pre-filter for pre-filtering the digital video signal from the sub-field, and 73 is an inter-field offset sub-sampling circuit for inter-field offset sub-sampling the video signal from the static area pre-filter 71.

Further, 74 is a moving area detecting circuit for detecting whether or not it is a moving area based on the video signal from the moving area pre-filter 72, and 75 is a moving area pre-detector according to the detection result of the moving area detecting circuit 74. A mixer that selects the output of the filter 72 or the output of the inter-field offset sub-sampling circuit 73, or mixes both outputs of both circuits 72, 73 at a predetermined mixing ratio, and 76 is a video signal output from the mixer 75 Is an inter-frame offset sub-sampling circuit that compresses the band of a video signal by performing inter-frame offset sub-sampling.

In the still region, the video signal is prefiltered by the still region prefilter 71, then subjected to interfield offset subsampling and interframe offset subsampling to compress information. On the other hand, in the moving area, the video signal is the moving area pre-filter 72.
After being pre-filtered by, the information is compressed by performing inter-frame offset sub-sampling.

Further, reference numeral 77 is a D / A conversion circuit for digital / analog converting the video signal from the inter-frame offset sub-sampling circuit 76, and 78 is an output circuit for externally outputting the video signal from the D / A conversion circuit 77. Is.

When the television receiver or the like receives the video signal sub-sampled on the transmitting side as described above, the television receiver or the like interpolates the video signal as a circuit for reproducing an image from the received signal. It has a circuit.

In this video signal interpolation processing circuit, "MUSE
-Hi-vision transmission method "(Yuichi Ninomiya, The Institute of Electronics, Information and Communication Engineers, 1990), there is a method to reproduce an image depending on whether the original image is still or moving. different. In the still region of the image, the original image is reproduced by interpolating between the frames using a plurality of frames. On the other hand, in the moving area, the zero interpolation processing is performed on the signal of one frame, and then the interpolation processing by the low-pass filter is performed to reproduce the image from the video signal of only one frame.

FIG. 14 shows the above-mentioned configuration of a television receiver or the like.

In the figure, reference numeral 80 is an A / D conversion circuit for analog / digital converting the received video signal, and 81 is an interframe interpolation circuit for interpolating the digital video signal from the A / D conversion circuit 80 between frames. Reference numeral 82 denotes an inter-field interpolation circuit for inter-field interpolating the video signal interpolated by the inter-frame interpolation circuit 81, and 83 a field for inter-field interpolating the digital video signal from the A / D conversion circuit 80. It is an interpolation circuit.

Reference numeral 84 is a moving area detecting circuit for detecting whether or not it is a moving area based on the video signal from the A / D conversion circuit 80, and 85 is a field according to the detection result of the moving area detecting circuit 84. A mixer for selecting the video signal from the interpolating circuit 82 or the video signal from the field interpolating circuit 83, or mixing both video signals of the two circuits 82 and 83 at a predetermined mixing ratio, and 86 is a mixer It is an output circuit for externally outputting the video signal output from 85 to a television receiver or the like.

When the image is a moving image, the aliasing distortion of the signal is prevented by applying a pre-filter which passes only the transmittable amount region of the sub-sampling circuit to limit the band. Therefore, in the still image, the image is transmitted without decreasing the information amount, whereas in the moving image, the information amount is reduced due to the band limitation, but from the human visual characteristics that the moving image has lower sensitivity than the still image, The lower resolution in the video is hard to see, so there is no problem.

An example of a conventional video signal interpolation processing circuit for processing a moving image as described above will be described below with reference to the drawings.

First, generation and transmission of a video signal received by the interpolation processing circuit will be described in advance. On the transmission side of a video signal, for example, in a television broadcasting station, etc., after inputting the original sampling signal at the signal input unit, the original sampling signal is included in the original sampling signal by limiting the band with a pre-filter consisting of a low-pass filter unit. After removing the high frequency component, the sampling process is performed in the sub-sampling unit.

As shown in FIG. 5, the original sampling signal is a video signal which is sampled in a square lattice form with h (Hz) in the horizontal direction and v (TV lines) in the vertical direction. As shown in Fig. 6, the horizontal transmission frequency is h /
At 2 (Hz), the vertical spatial frequency is v / 2 (TV lines).

Here, the case where the original sampling signal is band-compressed to 1/2 by the sub-sampling will be described. In the sub-sampling section, the sampling points 51 of the original sampling signal shown in FIG. As shown in (b), sampling points 52 are selected in a zigzag pattern in even frames, sampling points 53 are selected in odd frames, and the original sampling signal is band-compressed to 1/2 and transmitted. To do.

Next, a block diagram of a conventional interpolation processing circuit is shown in FIG.

In the figure, reference numeral 90 denotes a transmission system for transmitting the band-compressed video signal from a television broadcasting station or the like. Reference numeral 91 is a zero interpolation unit that inserts a zero value into the interpolation point of the video signal received from the transmission system 90. Further, 92 is a low-pass filter section for performing interpolation processing of the video signal from the zero interpolation section 91, 93 is a signal output section for outputting the video signal from the low-pass filter section 92, and 94 is from the signal output section 93. It is a cathode ray tube that receives a video signal and displays an image.

In such an interpolation processing circuit, the transmission system 90
After receiving the band-compressed video signal, in the zero interpolation unit 91, in the even-numbered frame of the video signal, points other than the sampling points 52 of the staggered even-numbered frame shown in FIG. Zero points are added with the points corresponding to the sample points 53 ... Of the odd frame in (b) as interpolation points, and the zero value is added to the sample points 53 ... In the odd frame of FIG. 7B in the odd frame. Reverse the even frame,
The sampling frequency of the video signal is returned to the original value, then the signal zero-interpolated by the low-pass filter unit 92 is low-pass filtered to perform interpolation processing, and the video signal after the interpolation processing is output from the signal output unit 93. Then, it is reproduced by the external cathode ray tube 94.

Here, the pre-filter used for the sub-sample is "Study on color-difference signal processing of MUSE system" (IEICE Transactions B-1, vol.j76-B-1, N).
O.3, pp.290-298, March 1993), the filter coefficient is changed to improve the image quality of the reproduced image in order to improve the image quality. In this case, the low-pass filter used for the interpolation also has its filter coefficient changed in accordance with the change of the filter coefficient of the pre-filter used for the sub-sample.

[0022]

The signal band that can be transmitted by the transmission system depends on the sub-sampling circuit on the television broadcasting station side and the low-pass filter on the interpolation processing circuit on the video signal receiving side. It is what is done. For example, in FIG.
When a vertical filter is used in the sub-sampling circuit 76 of No. 3, the vertical spatial frequency is limited to half v / 4 (TV lines) as shown in FIG. 8 as compared with the original sampling signal. When a two-dimensional low-pass filter is used, the transmission band becomes triangular as shown in FIG. Here, it is desirable that the spatial frequency characteristic of the low-pass filter unit 92 of the interpolation processing circuit accurately matches or approximates to the spatial frequency characteristic of the low-pass filter unit 2 of the sub-sampling circuit on the television broadcasting station side.

However, due to improvements and advances in technology for television receivers and the like, there arises a situation in which the transmittable bandwidth on the television receiver side does not exactly match or approximate to the transmittable bandwidth on the television broadcast station. As a result, for example, in the situation where the two-dimensional low-pass filter of the triangular transmission possible band shown in FIG. 9 is used as the sub-sampling circuit 76 on the video signal transmitting side, the interpolation processing circuit of the video signal receiving side is used. A case where a vertical low-pass filter having a rectangular transmittable band shown in FIG. 8 is used as the low-pass filter 92,
In this case, on the receiving side of the video signal, the band A1 shown in FIG. 10 is folded back to the band A2 portion, and there arises a drawback that, for example, the horizontal straight line of the reproduced image becomes a broken line.

In view of the above problems, the present invention has the following object.
Provided is an interpolation processing circuit capable of suppressing interference in image reproduction due to band folding distortion on the video signal receiving side, regardless of the video signal transmittable band of the video signal transmitting side sub-sampling circuit. To do.

[0025]

In order to solve the above-mentioned problems, in the present invention, a plurality of low-pass filters having different transmittable bands of video signals are previously provided in an interpolation processing circuit for sub-sampled video signals. The filter is provided so that a filter corresponding to the transmittable band of the low-pass filter of the sub-sampling circuit on the video signal transmission side can be selected.

According to another aspect of the invention, in the interpolation processing circuit for the sub-sampled video signal, the transmittable bands of the video signals of the plurality of types of low-pass filters adopted by the sub-sampling circuit on the video signal transmitting side mutually overlap. A low-pass unit that sets the available transmission band to the available transmission band is provided.

That is, in the sub-sampled video signal interpolation processing circuit according to the first aspect of the present invention, as the pre-filter for removing the high frequency component of the first video signal originally sampled in the square lattice form, the first filter is used. Low-pass filter and the first low-pass filter, a transmission-side low-pass filter unit using either one of a second low-pass filter having a transmittable band different from that of the first low-pass filter, and the transmission-side low-pass filter for the first video signal. A second video signal obtained by sub-sampling by the sub-sampling unit from a transmission side having a sub-sampling unit that performs sub-sampling in a zigzag inter-frame offset state after band limiting by the sub-sampling unit. And a second sub-sampled video signal interpolation processing circuit for performing interpolation processing on the second video signal, wherein A zero interpolation unit that generates a third video signal by inserting zero into the video signal, and a transmission of the third video signal from the zero interpolation unit that corresponds to the transmittable band of the first low-pass filter in advance. The fourth video signal is generated by interpolating with a low-pass filter of the possible band, and the third video signal from the zero interpolation unit is converted into a transmittable band corresponding to the transmittable band of the second low-pass filter in advance. A low-pass unit that interpolates with a low-pass filter to generate a fifth video signal; a selection control unit that outputs a command signal to select the fourth video signal or the fifth video signal from the low-pass unit; The fourth video signal and the fifth video signal from the low-pass unit are output according to the content of the command signal from the selection control means.
And a signal selection unit that selects and outputs any one of the video signals.

Further, in the invention of claim 2, in the interpolation processing device of the sub-sampled video signal according to claim 1, the fourth video signal or the fifth video signal output from the signal selecting section. Is provided on the screen, and the selection control means is a changeover switch manually operated by an operator who is viewing the screen of the CRT according to the image quality of the screen.

Further, in the invention according to claim 3, in the interpolation processing device of the subsampled video signal according to claim 1, the selection control means is a second subsampled by the subsample part. Is generated, and the command signal is generated based on the fourth video signal and the fifth video signal generated by the low-pass unit.

In addition, in the invention described in claim 4, in the interpolation processing circuit for the sub-sampled video signal according to claim 1, claim 2 or claim 3, the first low-pass filter section of the transmission side is provided. The low-pass filter is a vertical low-pass filter, the second low-pass filter of the transmitting side low-pass filter unit is a two-dimensional low-pass filter, and the low-pass unit interpolates the third video signal from the zero interpolation unit by the vertical low-pass filter. A vertical low-pass unit for generating a fourth video signal and a two-dimensional low-pass unit for interpolating the third video signal from the zero interpolation unit with a two-dimensional low-pass filter to generate a fifth video signal. It is characterized by

In addition, in the invention described in claim 5, in the interpolation processing circuit for the sub-sampled video signal according to claim 1 or 2, the first low-pass filter of the transmission-side low-pass filter section is It is a vertical low-pass filter, the second low-pass filter of the transmitting-side low-pass filter unit is a two-dimensional low-pass filter, and the low-pass unit is
A vertical low-pass unit that interpolates the third video signal from the zero interpolation unit with a vertical low-pass filter to generate a fourth video signal, and a fourth video signal from the vertical low-pass unit is interpolated with a horizontal low-pass filter. And a horizontal low-pass section for generating a fifth video signal.

According to the invention of claim 6, in the interpolation processing circuit of the subsampled video signal according to claim 3, the first low-pass filter is a vertical low-pass filter, and the second low-pass filter is A two-dimensional low-pass filter, wherein the selection control means interpolates the Nth frame of the third video signal of the zero interpolator with a vertical low-pass filter to generate a first interpolation point; A two-dimensional interpolation unit that interpolates the Nth frame of the third video signal of the zero interpolation unit with a two-dimensional low-pass filter to generate a second interpolation point, and an N + 1th frame of the third video signal. A first difference unit that generates a difference between a sample point and the first interpolation point;
A second difference unit that generates a difference between the sample point of the (N + 1) th frame of the third video signal and the second interpolation point; a difference between the first difference unit and the second difference unit; If the difference of the first difference part is less than the difference of the second difference part, the fourth difference
And a comparison unit that outputs a command signal to select the fifth video signal when the difference between the first difference unit and the difference between the first difference units is greater than or equal to the difference between the second difference units. And

Further, in the invention according to claim 7, in the interpolation processing circuit for the sub-sampled video signal according to claim 6, the low-pass portion is a vertical low-pass signal for the third video signal from the zero interpolation portion. A vertical low-pass unit that interpolates with a filter to generate a fourth video signal, and a third video signal from the zero interpolating unit is interpolated with a two-dimensional low-pass filter to obtain a fifth video signal.
And a two-dimensional low-pass portion of the selection control means, the vertical interpolating portion and the two-dimensional interpolating portion of the selection control means are shared by the vertical low-pass portion and the two-dimensional low-pass portion, respectively. Characterize.

In addition, in the invention described in claim 8, in the interpolation processing circuit for the sub-sampled video signal according to claim 6 or 7, the selection control means outputs the output of the first difference part. A first accumulator that accumulates a plurality of frames to generate a first accumulated value and a second accumulator that accumulates the output of the second difference unit for a plurality of frames to generate a second accumulated value. The comparison unit is characterized in that the outputs of the first and second accumulators are compared with each other.

In addition, in the invention described in claim 9, in the interpolation processing circuit for the sub-sampled video signal according to claim 6 or 7, the signal selection section includes a fourth video signal and a fourth video signal. 5 has an average value generation section for generating an average value with the video signal, and the selection control means has a difference between the first difference section and the second difference section.
When both of the differences of the difference units are larger than the specified values, the command signal is output so as to output the average value of the average value generation unit.

In the sub-sampled video signal interpolation processing circuit according to the tenth aspect of the present invention, as a pre-filter for removing high frequency components of the first video signal originally sampled in the square lattice form, 1 low-pass filter and a transmission-side low-pass filter section in which any one of a second low-pass filter having a transmittable band different from that of the first low-pass filter is used; A second sub-sample obtained by sub-sampling by the sub-sampling unit from a transmission side, which comprises a sub-sampling unit that performs sub-sampling in a zigzag inter-frame offset state after band limiting by the filter unit.
A sub-sampled video signal interpolation processing circuit for receiving the second video signal and performing an interpolation process on the second video signal. And a third video signal from the zero interpolation unit overlaps the transmittable band of the first low-pass filter and the transmittable band of the second low-pass filter. And a low-pass unit that interpolates with a low-pass filter in a transmittable band corresponding to the transmission band in advance to generate a fourth video signal.

Further, in the invention according to claim 11, in the interpolation processing circuit for the sub-sampled video signal according to claim 10, the low-pass part is the first video signal from the zero interpolation part. A low-pass filter having a transmission band that corresponds to the transmission band of the low-pass filter in advance, and a signal that has been interpolated by the first low-pass filter unit, and then the second low-pass filter. And a second low-pass filter section which is interpolated by a low-pass filter in the transmittable band corresponding to the transmittable band in advance.

In addition, in the invention described in claim 12, in the interpolation processing circuit for the sub-sampled video signal according to claim 11, the first low-pass filter of the transmission-side low-pass filter section is a vertical low-pass filter. , The second low-pass filter of the transmission-side low-pass filter unit is a two-dimensional low-pass filter, and the first low-pass filter unit of the low-pass unit interpolates the third video signal from the zero interpolation unit with a vertical low-pass filter. The second low-pass filter section of the low-pass section is characterized in that the signal interpolated by the first low-pass filter section is further interpolated by a two-dimensional low-pass filter.

In addition, according to the invention of claim 13,
12. The sub-sampled video signal interpolation processing circuit according to claim 11, wherein the first low-pass filter section of the transmission side is provided.
Is a vertical low-pass filter, and the second low-pass filter of the transmitting-side low-pass filter unit is 2
The first low-pass filter unit of the low-pass unit interpolates the third video signal from the zero interpolation unit by the vertical low-pass filter, and the second low-pass filter unit of the low-pass unit is a three-dimensional low-pass filter. The signal interpolated by the first low pass filter section is further interpolated by a horizontal low pass filter.

[0040]

With the above construction, in the video signal interpolation processing circuit according to the first and fourth aspects of the present invention, when the first low-pass filter is adopted in the transmitting low-pass filter section, the low-pass section is adopted. Then, the fourth video signal interpolated by the low-pass filter in the transmittable band corresponding to the transmittable band of the first low-pass filter in advance is generated, and there is no aliasing distortion in the fourth video signal. on the other hand,
When the second low-pass filter is adopted in the transmission-side low-pass filter section, the fifth low-pass filter interpolated by the low-pass filter in the transmittable band corresponding to the transmittable band of the second low-pass filter in advance is adopted in the low-pass section. The video signal is generated, and the fifth video signal has no aliasing distortion. Therefore, by selectively switching the video signal output from the signal selection section by the selection control means, the video signal interpolated in a band approximate to or in agreement with the signal transmission possible band of the sub-sampling circuit on the video signal transmission side. Can be output from the signal selection unit, and aliasing distortion can be prevented.

Here, in particular, in the invention described in claim 2,
The operator operates the change-over switch while watching the image display on the cathode ray tube, so that the fourth or the fourth image on the side of good image quality (that is, no aliasing distortion) on the reproduced image without interference such that the horizontal straight line becomes a broken line. 5 video signals can be selected.

According to the third aspect of the invention, the selection control means is based on the fourth video signal and the fifth video signal generated by the low-pass section, that is, the signals with and without the aliasing distortion. Since a command signal for selecting which video signal is selected, the video signal on the side free from aliasing distortion is accurately and automatically selected.

According to the fifth aspect of the invention, when the transmitting low-pass filter section employs a two-dimensional low-pass filter, the fourth video signal interpolated by the vertical low-pass section is output as the output of the signal selecting section. Further, the fifth video signal interpolated by the horizontal low-pass section is selected. Here, the signal transmissible band of the two-dimensional low-pass filter of the transmission side low-pass filter unit is a predetermined triangular region, while the overlapping region of both the signal transmissible bands of the vertical low-pass unit and the horizontal low-pass unit is the triangular region. Although the rectangular area included in the area becomes narrow and the information amount of the signal decreases, there is no problem because human visual characteristics have low sensitivity to a moving image. In addition, the horizontal low-pass unit has a simpler structure than the two-dimensional low-pass filter, so that the circuit scale is small and the size can be reduced.

According to the sixth aspect of the invention, in the automatic selection of the video signal by the selection control means, the difference between the first difference portion and the difference between the second difference portions are compared with each other, and the difference of the first difference portion is compared. When the difference is smaller, that is, when the transmission side low-pass filter section includes a vertical low-pass filter, the fourth video signal interpolated by the vertical low-pass filter having the same transmission band as the vertical low-pass filter by the comparison section. When the difference of the second difference section is smaller, that is, when the transmission side low-pass filter section has a two-dimensional low-pass filter, the comparison section outputs the two-dimensional low-pass filter. A command signal is output so as to select the fifth video signal interpolated by the two-dimensional low-pass filter having the same transmission band as the low-pass filter.

Further, in the invention according to the seventh aspect, the vertical interpolation section and the two-dimensional interpolation section of the selection control means are respectively used by the vertical low-pass section and the two-dimensional low-pass section of the low-pass section. Therefore, the circuit configuration is simple.

In addition, in the invention according to claim 8, in the selection control means, the cumulative value of the output of the first difference part and the second value
Since the cumulative value of the output of the difference part of is compared by the comparison part,
The video signal having no aliasing distortion is accurately selected.

Further, in the invention according to claim 9, in the selection control means, both the cumulative value of the output of the first difference part and the cumulative value of the output of the second difference part are both larger than the specified value. In this case, that is, when the movement of the image is large between consecutive screens (frames), the average value of the fourth video signal and the fifth video signal generated by the average value generation unit, that is, the fourth video signal As compared with the case where the video signal or the fifth video signal is selected, a video signal with less aliasing distortion and a smaller signal strength of the interfering signal is selected and output. Therefore, in this case as well, the horizontal straight line of the reproduced image is A good image without broken lines is reproduced.

According to the tenth to thirteenth aspects of the present invention, the transmittable band of the lowpass filter provided in the lowpass section is the overlap of the transmittable bands of a plurality of types of lowpass filters that can be adopted in the transmitting lowpass filter section. Since it is set in the area, even if any one low-pass filter is adopted in the transmission-side low-pass filter unit, the video signal output from the low-pass unit is always free from interference due to aliasing distortion and a good image is obtained. Is played.

In particular, according to the thirteenth aspect of the present invention, since the vertical low-pass filter section and the horizontal low-pass filter section are used in the low-pass section, the configuration is simple as compared with the case of using the two-dimensional low-pass filter. The circuit scale is small and miniaturization is possible.

[0050]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a sub-sampled video signal interpolation processing circuit of the present invention will be described below with reference to the drawings.

(First Embodiment) FIG. 1 is a block diagram of a sub-sampling circuit arranged on the transmission side of a video signal.
In the figure, 1 is a signal input section for inputting a primitive sampling signal as a first video signal as shown in FIG.
Is a low-pass filter unit (transmission-side low-pass filter unit) that operates as a pre-filter for limiting the transmission band of the original sampling signal from the signal input unit 1, and 3 is the original sampling signal that has passed through the low-pass filter unit 2. This is a sub-sampling unit that performs sampling processing.

Reference numeral 4 is a transmission system for transmitting the sub-sampled video signal sampled by the sub-sampler 3 to the receiving side thereof.

The low-pass filter section 2 uses either a vertical low-pass filter (first low-pass filter) or a two-dimensional low-pass filter (second low-pass filter) as a pre-filter. When the vertical low-pass filter is used, the sub-sampled signal can be transmitted at a vertical spatial frequency of v / 4 as shown in FIG.
(TV line) and a rectangular area with a horizontal spatial frequency of h / 2 (Hz). The transmittable band of the sub-sampled signal when the two-dimensional low-pass filter 14 is used is shown in FIG.
As shown in, the triangular region has a maximum vertical spatial frequency of v / 2 (TV lines) and a maximum horizontal spatial frequency of h / 2 (Hz).

Further, from the sub-sampling unit 3 to the transmission system 4
As shown in FIGS. 7 (a) and 7 (b), the sub-sampling signal as the second video signal output to the It is a signal (second video signal) obtained by sub-sampling. In the figure, 52 is a sample point of an even frame, and 53 is a sample point of an odd frame.

FIG. 2 shows a sub-sampled video signal interpolation processing circuit which is the object of the present invention, and which performs interpolation processing on the video signal received from the transmission system 4 shown in FIG. There is.

In FIG. 2, reference numeral 4 is a transmission system for transmitting a video signal from the sub-sampling circuit shown in FIG.

Reference numeral 12 is a zero interpolation unit for generating a third video signal in which a zero value is inserted at the interpolation point of the video signal received from the transmission system 4.

Further, in the figure, reference numeral 8 is a low-pass section, inside which a vertical low-pass filter (vertical low-pass section) 13 and a two-dimensional low-pass filter (two-dimensional low-pass section) 14 are provided. The vertical low-pass filter 13 has a cutoff frequency of v / 4 (TV lines), and the low-pass filter unit 2 of the sub-sampling circuit shown in FIG.
Is a vertical low-pass filter, the third video signal from the zero interpolation unit 12 is interpolated in the transmissible band corresponding to the transmissible band of the video signal in advance, and the video signal S1 is obtained as the fourth video signal. To generate. Further, the two-dimensional low-pass filter 14 has a transmissible band that corresponds to the transmissible band of the video signal in advance when the low-pass filter unit 2 of the sub-sampling circuit shown in FIG. 1 is a two-dimensional low-pass filter. That is, the maximum vertical spatial frequency
It is a triangular band limited by v / 2 (TV lines) and the maximum horizontal spatial frequency h / 2 (Hz), and the third video signal from the zero interpolation unit 12 is transmitted in this transmittable band. By interpolating, a video signal S2 is generated as a fifth video signal.

Further, 15 is the vertical low-pass filter 1
A selector (signal selection unit) as a signal selection unit for switching the video signal S1 of 3 and the video signal S2 of the two-dimensional low-pass filter 14, a signal output unit 16 for externally outputting the video signal selected by the selector 15. Is a manually operated changeover switch (selection control means), and this changeover switch 17 is manually changed over by an operator who is watching a CRT having an image display screen, and the changeover signal is the selector. It is output to 15. The selector 15 is
Upon receiving the switching signal, the video signal S1 from the vertical low-pass filter 13 or the video signal S2 from the two-dimensional low-pass filter 14 is selected according to the content of the switching signal.

A cathode ray tube 19 receives the video signal from the signal output unit 16 and displays a moving image.

The operation of the interpolation processing circuit according to the first embodiment of the present invention constructed as above will be described below.

In the interpolation processing circuit shown in FIG. 2, after receiving the video signal band-compressed by the sub-sampling circuit shown in FIG. 1 from the transmission system 4, the zero interpolation unit 12 receives the video signal shown in FIG.
A point other than the sampling points 52 of the even-numbered frame of (a), that is, a point corresponding to the sampling point 53 of the odd-numbered frame is added as an interpolation point, and a zero value is added.
A zero value is added with points other than the sampling points 53 in the odd numbered frame of FIG. 7B as interpolation points to restore the sampling frequency of the video signal to the original value.

Further, the vertical low-pass filter 13 of the low-pass section 8 generates a video signal S1 which is vertically interpolated from the zero-interpolated signal. Therefore, the generated video signal S1 has a vertical band of v / 4 (TV lines).
And the transmittable band matches the transmittable band when the vertical low-pass filter is used in the low-pass filter unit 32 of the sub-sampling circuit shown in FIG.

The two-dimensional low-pass filter 14 of the low-pass section 8 generates a video signal S2 which is interpolated in the vertical and horizontal two-dimensional directions from the zero-interpolated signal. Therefore, the transmittable band of the generated video signal S2 is a triangular band limited by the maximum vertical spatial frequency v / 2 (TV lines) and the maximum horizontal spatial frequency h / 2 (Hz), When the low-pass filter unit 2 of the sub-sampling circuit shown in FIG. 1 is a two-dimensional low-pass filter, they match in correspondence with the transmittable band of the video signal.

The selector 15 selects the video signal S1 and the video signal S according to the contents of the selection command signal from the changeover switch 17.
2 is selectively switched, and the signal output unit 16 externally outputs the selected video signal S1 or S2,
1 or the video signal S2 is reproduced.

That is, initially, the operator alternately switches the changeover switch 17. As a result, the vertical low pass filter 1
The video signal S1 from 3 and the video signal S2 from the two-dimensional low-pass filter 14 are alternately selected by the selector 15,
The selected video signal S1 or S2 is reproduced on the image display screen of the cathode ray tube.

When a vertical low-pass filter is used as the low-pass filter 2 of the sub-sampling circuit, the transmittable band of the video signal transmitted by the transmission system 4 is the vertical spatial frequency v shown in FIG. Since this is a rectangular area limited by / 4 (TV lines) and the horizontal spatial frequency h / 2 (Hz) and matches the transmittable band of the video signal S1 from the vertical low-pass filter 13, this video signal transmission side The video signal from the sub-sampling circuit is transmitted as the video signal S1 without loss, and the horizontal straight line is not a broken line on the display screen on which the video signal S1 is reproduced on the cathode ray tube.

On the other hand, when a two-dimensional low-pass filter is used as the low-pass filter 2 of the sub-sampling circuit of FIG. 1, the transmittable band of the video signal transmitted by the transmission system 4 is shown in FIG. Maximum vertical spatial frequency v /
Since it is a triangular area limited by 2 (TV lines) and the maximum horizontal spatial frequency h / 2 (Hz), the transmittable band of the video signal S1 is the vertical spatial frequency v / 4 (TV lines) shown in FIG. ) And the horizontal spatial frequency h / 2, the rectangular area is limited by
The spatial frequency band A1 surrounded by diagonally shaded 0 is folded back to the band A2 and becomes a signal in a rectangular area including interference, but since it matches the transmittable band of the video signal S2 from the two-dimensional low-pass filter 14, this The video signal from the sub-sampling circuit on the video signal transmitting side is transmitted as the video signal S2 without loss, and the display screen on the cathode ray tube which reproduces the video signal S2 is a good screen without broken horizontal lines.

Therefore, the operator looks at the image display of the cathode ray tube and switches the switch 1 so that the screen on the favorable side is fixed.
If 7 is switched and then fixed, the vertical or 2 of the transmittable band that corresponds well to the transmittable band of the lowpass filter adopted by the lowpass filter 2 of the sub-sampling circuit of FIG.
Since the video signal or S2 interpolated by the dimensional low-pass filter is selected and output, a good moving image without a broken horizontal straight line is reproduced on the cathode ray tube.

As described above, in the present embodiment, the spatial frequency band folded when the sub-sampling circuit and the interpolation processing circuit have different transmittable areas can be removed by the low-pass filter of the interpolation processing circuit. For example, it is possible to remove a disturbance in which a horizontal straight line of a reproduced image becomes a broken line.

(Second Embodiment) FIG. 3 shows a second embodiment of the present invention. In the first embodiment, the low pass unit 8 includes a vertical low pass filter 13 and a two-dimensional low pass filter 14.
Instead of providing the and, a vertical low-pass filter and a horizontal low-pass filter are provided.

That is, in FIG. 3, reference numeral 8 is a low-pass portion, and inside thereof, a vertical low-pass filter (vertical low-pass portion) 13 and a horizontal low-pass filter (horizontal low-pass portion) 18 are provided. Like the first embodiment, the vertical low-pass filter 13 has a cutoff frequency of v / 4 (TV lines) and the low-pass filter unit 2 of the sub-sampling circuit of FIG. 1 is a vertical low-pass filter. In the transmittable band corresponding to the transmittable band of the video signal in advance, the third video signal from the zero interpolation unit 12 is interpolated to generate the video signal S1 as the fourth video signal.

Further, the horizontal low-pass filter 18 is
The cutoff frequency is h / 4 (Hz) and the video signal S1 from the vertical low pass filter 13 is interpolated to generate a video signal S3 as a fifth video signal.

The selector (signal selection section) 15 selectively switches between the video signal S1 of the vertical low pass filter 13 and the video signal S3 of the horizontal low pass filter 18,
Output.

Since the other structure is the same as that of the first embodiment, the same reference numerals are given to the same portions and the description thereof will be omitted.

Therefore, in this embodiment, the video signal S1 generated by the vertical low-pass filter 13 in the low-pass section 8 is further passed through the horizontal low-pass filter 18 and the horizontal spatial frequency is limited to h / 4 (Hz). As a result, a video signal S3 is generated in which the vertical band is limited to v / 4 (TV lines) and the horizontal band is limited to h / 4 (Hz).

As a result of the alternate switching operation of the selector switch 17 by the operator, the selector 15 is a good image side video signal in which the horizontal straight line of the reproduced image does not become a broken line, that is, the low-pass filter section 2 of the sub-sampling section in FIG. When the vertical low-pass filter is adopted as, the video signal S1 from the vertical low-pass filter 13 is selected, and when the two-dimensional low-pass filter is adopted as the low-pass filter unit 2 of the sub-sample part in FIG. , The video signal S3 from the horizontal low-pass filter 18 is selected.

Here, the transmittable band of the video signal S3 from the horizontal low-pass filter 18 is the vertical spatial frequency v / 4 (TV
Book) and the horizontal spatial frequency h / 4 (Hz), the rectangular area is limited, so that the triangular bands A1 and A shown in FIG.
Although the resolution is reduced by the amount corresponding to 3, the human visual characteristics have low sensitivity to moving images, and the lowered resolution is difficult to see, so there is no problem.

Moreover, comparing the circuit scale with the low-pass unit 8 of the first embodiment, the two-dimensional low-pass filter 14 is provided in the first embodiment as a part of the filters necessary for the interpolation processing. In this embodiment, a horizontal low pass filter 18 is provided. 2D low-pass filter 3 × 3
When a two-dimensional filter with taps is used, eight delay elements, eight adders, and eight multipliers are required.
A three-tap horizontal (one-dimensional) filter can be composed of two delay elements, two adders, and two multipliers, and has the effect of reducing the circuit scale as compared with the case where a two-dimensional low-pass filter is used for interpolation processing.

(Third Embodiment) FIG. 4 is a block diagram of an interpolation processing circuit according to the third embodiment of the present invention. In each of the first and second embodiments, the configuration in which the video signal is selectively switched by the manual operation of the changeover switch 17 by the operator is adopted, whereas in the present embodiment, the configuration in which the video signal is automatically switched is adopted. To do.

In FIG. 4, 4 is a transmission system, and 12 is a zero interpolation unit for inserting a zero value at an interpolation point.

Reference numeral 8 is a low-pass section, in which a vertical low-pass filter 13 with a cut-off frequency of v / 4 (TV lines) and a maximum vertical spatial frequency v / 2 with a transmittable band are provided.
A two-dimensional low-pass filter 21, which is a triangular band limited by (TV lines) and the maximum horizontal spatial frequency h / 2 (Hz), is provided. 15 is the vertical low-pass filter 13
16 is a signal output unit, which internally includes a selector 28 as a signal selection unit that switches between the video signal P2 from P.sub.2 and the video signal P3 from the two-dimensional low-pass filter 21.

Further, 29 is a control section (selection control means), in which a frame memory for accumulating a predetermined one frame (Nth frame) of video signal P1 from the zero interpolation section 12 is stored. 20, a first difference unit 22, a second difference unit 23, a first accumulator 25 that accumulates the output from the first difference unit 22, and an output from the second difference unit 23. A second accumulator 26 for accumulating and a comparing section 24 are provided. Further, the vertical low-pass filter 13 is also provided as a vertical interpolating section, and the two-dimensional low-pass filter 21 is also provided as a two-dimensional interpolating section, so that the video signal from the frame memory 20 is provided in the vertical low-pass section. It is output to the filter 13 and the two-dimensional low-pass filter 21.

The first difference section 22 of the control section 29 includes the video signal from the zero interpolation section 12 and the vertical low pass filter 1.
3 from the video signal, that is, an arbitrary one frame (Nth frame) sample point and an interpolation point at the position of the sample point in a frame (N + 1th frame) one frame after the frame. Is calculated and the calculation result is output, and the second difference unit 23 similarly calculates the difference between the video signal from the zero interpolation unit 12 and the video signal from the two-dimensional low-pass filter 21. The difference is calculated and the calculation result is output.

Further, the comparison section 24 outputs the output of the first accumulator 25, that is, the accumulated value of the difference result from the first difference section 22 in a plurality of frames, and the output of the second accumulator 26.
That is, the difference value from the second difference unit 23 and the cumulative value in a plurality of frames are first compared with the specified value, respectively, and the accumulated values of both differences are compared only when both are less than the specified value.
The video signal having the smaller difference cumulative value is the video signal P2 or P2.
A signal indicating that the value is 3 is output to the selector 28. Further, when the accumulated values of both differences are both equal to or greater than the specified value, it has a function of outputting to the selector 15 a signal indicating that neither of the video signals P2 and P3 can be selected.

Further, the signal selection section 15 is provided with an average value generation section 27 together with the selector 28. The average value generation unit 27 has a function of generating an average value of the video signal P2 from the vertical low pass filter 13 of the low pass unit 8 and the video signal P3 from the two-dimensional low pass filter 21.

The operation of the interpolation processing circuit according to the third embodiment of the present invention constructed as above will be described below.

In the interpolation processing circuit, after the video signal band-compressed by the sub-sampling circuit is received from the transmission system 4, the zero interpolation unit 12 makes an even-numbered zigzag pattern of FIG. Zero values are added by using points other than the sample points 52 of the frame as interpolation points, and zero values are set by using points other than the sample points 53 of the staggered odd-numbered frame of FIG. In addition, the sampling frequency is returned to the original value, and the video signal P1 having the restored sampling frequency is added.
Is output.

Next, in the control unit 29, the frame memory 20 delays the video signal P1 by one frame and sends it to the vertical low-pass filter 13 and the two-dimensional low-pass filter 21. The vertical low-pass filter 13 of the low-pass unit 8 generates the video signal P2 interpolated in the vertical direction, and the two-dimensional low-pass filter 21 generates the video signal P2 interpolated in the two-dimensional direction.
3 is generated.

Furthermore, the first difference unit 22 and the second difference unit 2
3 outputs the respective differences between the video signal P1 and the video signal P2, and the video signal P1 and the video signal P3, and the respective differences are accumulated for a plurality of frames by the first accumulator 25 and the second accumulator 26. To be done.

After that, in the comparison section 24, the first accumulator 25 and the second accumulator 26 corresponding to the sampling points of the video signal P1.
The cumulative values of the respective differences are compared and the signal indicating the video signal having the smaller cumulative value of the differences is output to the selector 28. The selector 28 receives the output from the comparison unit 24 and switches and selects the video signal P2 or P3 having the smaller cumulative value of the difference, and the selected video signal P2 or P3 is output from the signal output unit 16. , Reproduced by an external cathode ray tube 19.

Here, the first and second difference units 22 and 23
In calculating the difference in the video signal P1 and the video signal P2,
Since the video signal P1 and the video signal P3 are shifted from each other by one frame, the positional relationship between the sampling point and the interpolation point is opposite. For example, the sampling points of the video signal P1 correspond to the interpolation points of the video signal P2 and the video signal P3. Therefore, the signal indicating the video signal having the smaller cumulative value of the difference output from the comparison unit 24 is the signal indicating the video signal having no aliasing distortion.

That is, when the vertical low-pass filter is used as the low-pass filter unit 2 of the sub-sampling circuit of FIG. 1 on the video signal transmitting side and the band is limited, the selector 28 causes the video signal from the vertical low-pass filter 13 to be selected. P
Select 2. Here, the transmittable area of the video signal transmitted by the transmission system 4 is the vertical spatial frequency v / 4 shown in FIG.
It is a rectangular area limited by (TV lines) and the horizontal spatial frequency h / 2 (Hz), and coincides with the transmittable area of the video signal P2.

When the two-dimensional low-pass filter is used as the low-pass filter unit 2 of the sub-sampling circuit of FIG. 1 and the band is limited, the selector 28 selects the video signal P3 from the two-dimensional low-pass filter 21. To do. Here, the transmittable area of the video signal transmitted by the transmission system 4 is the maximum vertical spatial frequency v / 2 (TV lines) shown in FIG.
And a maximum horizontal spatial frequency h / 2 (Hz) in a triangular band, which coincides with the transmittable area of the video signal P3. Therefore, it is possible to prevent the aliasing of the spatial and spatial frequency band, to transmit the video signal from the sub-sampling circuit on the video signal transmitting side without loss, and to reproduce the video signal well on the receiving side.

Further, the differences for a plurality of frames are accumulated by the first accumulator 25 and the second accumulator 26, and the accumulated results of the differences are compared by the comparator 24, so that the sub-sampling circuit of FIG. It is possible to accurately select the video signal interpolated by the low-pass filter having the transmission available band that corresponds favorably to the signal transmission available band of the low-pass filter adopted by the low-pass filter unit 2.

Furthermore, the first accumulator 25 and the second accumulator 2
When the difference cumulative value with 6 is greater than or equal to the specified value, that is,
When the movement of the image is rapid between consecutive screens (frames), the video signal output from the average value generation unit 27 with a small aliasing distortion (that is, the video signal obtained by averaging the video signals P2 and P3) is generated. Since it is selected by the selector 28, the signal strength of the interfering signal can be reduced, and a good image in which the horizontal straight line of the reproduced image does not become a broken line is reproduced.

As described above, according to this embodiment,
The video signal on the side interpolated by the low-pass filter of the transmissible band that corresponds well to the signal transmissible band of the vertical low-pass filter or the two-dimensional low-pass filter adopted by the low-pass filter unit 2 of the sub-sampling circuit of FIG. 1 is appropriately selected. It is possible to prevent the aliasing of the spatial frequency band caused by the difference between the sub-sampling circuit and the interpolation processing circuit and the transmission possible bands of the sub-sample circuit and the interpolation processing circuit. There is an effect that it is possible to effectively suppress the occurrence of interference such as a broken line.

(Fourth Embodiment) FIG. 11 shows a fourth embodiment of the present invention. In all of the first to third embodiments, a configuration is adopted in which one of the two types of low-pass filters included in the low-pass unit 8 is selected, but in the present embodiment,
The low-pass filter unit 2 of the sub-sampling unit in FIG. 1 has a configuration in which a vertical low-pass filter and a two-dimensional filter are provided with a low-pass filter in which only the transmission bands in which the signal transmission bands overlap each other are used. .

That is, in the interpolation processing circuit of FIG. 11, the low-pass unit 8 has a vertical low-pass filter (first low-pass filter unit) 13 and a two-dimensional low-pass filter (second low-pass filter) as in the second embodiment. The low-pass filter unit) 14 is connected in series. The selector 15 of the first embodiment is unnecessary and not provided in this embodiment.

Therefore, in the present embodiment, the signal transmittable band of the low-pass section 8 is the vertical spatial frequency v /
The area is a combination of a rectangular area limited by 4 (TV lines) and the horizontal spatial frequency h / 4 (Hz) and a triangular area indicated by symbol A3 in the figure.

Therefore, regardless of which of the vertical low-pass filter and the two-dimensional low-pass filter the low-pass filter unit 2 of the sub-sampling unit of FIG. 1 adopts, the vertical low-pass filter 13 and the two-dimensional low-pass filter 14 of the low-pass unit 8 are used. The video signal interpolated in (1) becomes a signal that does not include the aliasing distortion component of the band, and a good image in which the horizontal straight line does not become a broken line is obtained as a reproduced moving image in a cathode ray tube or the like.

Here, although the resolution of the transmittable band of the video signal from the low-pass section 8 is reduced by the areas indicated by the symbols A1 and A2 in FIG. 10, the human visual characteristics have low sensitivity to moving images and the resolution is low. The lowering of is difficult to see, so there is no problem.

Although the two-dimensional low-pass filter 14 is arranged after the vertical low-pass filter 13 in this embodiment, it is needless to say that the two-dimensional low-pass filter 14 may be arranged first in the opposite configuration. is there.

(Fifth Embodiment) FIG. 12 shows a fifth embodiment of the present invention. Instead of the two-dimensional low-pass filter 14 of the low-pass section 8 of the fourth embodiment, a horizontal low-pass filter (second embodiment) is used. A low-pass filter section 18 is provided. The other structure is similar to that of the fourth embodiment shown in FIG. 11, and therefore its explanation is omitted.

Therefore, in the present embodiment, the signal transmittable band of the low-pass section 8 is the vertical spatial frequency v /
It is a rectangular area limited by 4 (TV lines) and horizontal spatial frequency h / 4 (Hz). Therefore, as in the fourth embodiment, as shown in FIG.
Regardless of which of the vertical low-pass filter and the two-dimensional low-pass filter is used for the low-pass filter unit 2 of the sub-sample unit, the video signal interpolated by the vertical low-pass filter 13 and the horizontal low-pass filter 18 of the low-pass unit 8 is The signal does not include the aliasing distortion component of the band, and a good image in which the horizontal line does not become a broken line can be obtained as a reproduced moving image on a cathode ray tube or the like.

Here, the transmittable band of the video signal from the low-pass section 8 is the area indicated by the symbols A1, A2 and A3 in FIG. The lower resolution is hard to see, so there is no problem.

In addition, as for the circuit scale of the horizontal low-pass filter 18, as compared with the two-dimensional low-pass filter 14 of the low-pass section 8 of the fourth embodiment, 8 delay elements, 2 adders, and 2 multipliers are provided respectively. The number of individual circuits can be reduced to a simple structure, and the circuit scale can be reduced as compared with the case where a two-dimensional low-pass filter is used for interpolation processing.

[0108]

As described above, according to the sub-sampled video signal interpolation processing circuit of the first and fourth aspects of the present invention, the low-pass filter employed in the transmission-side low-pass filter section is used. Since a video signal generated by interpolating with a low pass filter in the transmittable band that corresponds to the transmittable band in advance can be selected and output, it is necessary to reproduce a moving image using a good video signal with no band aliasing distortion. Therefore, it is possible to remove a disturbance such that the horizontal line of the reproduced moving image becomes a broken line, and obtain a good and beautiful moving image.

Particularly, according to the second aspect of the present invention, the operator can select a good moving image in which the horizontal straight line of the reproduced image does not become a broken line by operating the changeover switch while looking at the screen of the cathode ray tube. it can.

According to the third aspect of the present invention, which one of the video signals is generated based on the two kinds of video signals generated by the low-pass section (that is, the video signal with aliasing distortion and the video signal with no aliasing distortion). Since the command signal for selecting is generated, the video signal on the side without aliasing can be automatically and accurately selected.

Further, according to the invention of claim 5, since the low-pass section is provided with the vertical low-pass section and the horizontal low-pass section, even when the transmitting-side low-pass filter section adopts the two-dimensional low-pass filter, Although the amount of information in the signal is reduced, it is possible to reduce the circuit size and size by simplifying the configuration while providing a good and beautiful moving image for human visual characteristics.

In addition, according to the invention described in claim 6, in the selection control means, the sampling point of an arbitrary frame and the interpolation at the position of the sampling point in the frame one frame before or after that frame are interpolated. Since the difference between the point and the point is calculated and the command signal is generated to select the video signal with the smaller difference, it is possible to perform transmission that corresponds well to the transmission range of the low-pass filter adopted by the transmission-side low-pass filter section. The video signal on the side interpolated by the low-pass filter of the band can be automatically and surely selected and output, and a good and beautiful moving image can be reproduced.

In addition, in the invention described in claim 7, since the vertical interpolating portion and the two-dimensional interpolating portion of the selection control means are respectively used as the vertical lowpass portion and the two-dimensional lowpass portion of the lowpass portion, respectively. Therefore, the circuit configuration can be simplified.

According to the present invention, the difference between the sampling point of an arbitrary frame and the interpolation point at the position of the sampling point in the frame immediately before or after that frame is accumulated, Since the command signal is generated to select the video signal having the smaller cumulative value, the video signal having no aliasing distortion can be accurately selected.

Further, in the invention according to claim 9, when the motion of the image is large between consecutive moving screens, the average of the fourth video signal and the fifth video signal generated by the average value generating section is calculated. Since the video signal is output, the video signal with less aliasing distortion and signal intensity of the interfering signal can be selected, and a good image in which the horizontal straight line of the reproduced image is not a broken line is reproduced.

In addition, claims 10 to 13 are further provided.
In the invention described, since the transmittable band of the lowpass filter provided in the lowpass unit is set to the overlapping region of each transmittable band of the plurality of types of lowpass filters that can be adopted in the transmitting lowpass filter unit, the transmitting side lowpass filter unit Regardless of which low-pass filter is adopted, there is no aliasing of the band, and the low-pass section can always output a video signal without interference due to aliasing distortion, and a good image can be reproduced.

In particular, according to the thirteenth aspect of the invention, since the vertical low-pass filter section and the horizontal low-pass filter section are used in the low-pass section, the structure can be simplified as compared with the case of using the two-dimensional low-pass filter. The circuit scale can be reduced and the size can be reduced.

[Brief description of drawings]

FIG. 1 is a block diagram of a sub-sampling circuit.

FIG. 2 is a block diagram of an interpolation processing circuit according to the first embodiment of the present invention.

FIG. 3 is a block diagram of an interpolation processing circuit according to a second embodiment of the present invention.

FIG. 4 is a block diagram of an interpolation processing circuit according to a third embodiment of the present invention.

FIG. 5 is a diagram showing a primitive sampling signal.

FIG. 6 is a diagram showing a transmittable band of a primitive sampling signal.

FIG. 7 is a diagram showing sub-sampled signals in an even frame and an odd frame.

FIG. 8 is a diagram showing a transmittable band of a sub-sampled signal by a vertical low pass filter.

FIG. 9 is a diagram showing a transmittable band of a sub-sampled signal by a two-dimensional low-pass filter.

FIG. 10 is a diagram showing a spatial frequency band of an interference signal.

FIG. 11 is a block diagram of an interpolation processing circuit according to a fourth embodiment of the present invention.

FIG. 12 is a block diagram of an interpolation processing circuit according to a fifth embodiment of the present invention.

FIG. 13 is a block diagram showing an overall schematic configuration of a video signal transmitting side.

FIG. 14 is a block diagram showing an overall schematic configuration of a television receiver side.

FIG. 15 is a block diagram of a conventional interpolation processing circuit.

[Explanation of symbols]

2 low-pass filter 3 sub-sampling unit 4 transmission system 8 low-pass unit 12 zero interpolation unit 13 vertical low-pass filter (vertical low-pass unit) 14 two-dimensional low-pass filter (two-dimensional low-pass unit) 15 signal selection unit 17 changeover switch (selection control means) 18 horizontal low-pass filter (horizontal low-pass unit) 20 frame memory 21 two-dimensional low-pass filter 22 first difference unit 23 second difference unit 24 comparison unit 25 first accumulator 26 second accumulator 28 selector 29 control unit ( Selection control means)

Claims (13)

[Claims] 1. A first low-pass filter and a second low-pass filter having a transmittable band different from that of the first low-pass filter as a pre-filter for removing high-frequency components of a first video signal originally sampled in a square lattice form. A transmission-side low-pass filter unit in which one of the low-pass filters is used, and the first video signal is band-limited by the transmission-side low-pass filter unit and then sub-sampled in a zigzag inter-frame offset state. A second video signal obtained by sub-sampling by the sub-sampling unit is received from a transmission side having a sub-sampling unit, and interpolation processing is performed on the second video signal. A video signal interpolation processing circuit, wherein a zero interpolation unit that generates a third video signal by interpolating zeros into the second video signal; The third video signal from the inserting section is interpolated by a low-pass filter having a transmissible band corresponding to the transmissible band of the first low-pass filter in advance to generate a fourth video signal, and the zero interpolating section is used. A third low-pass filter for interpolating the third video signal of the second low-pass filter with a low-pass filter having a transmission possible band corresponding to the transmission possible band of the second low-pass filter in advance to generate a fifth video signal; Selection control means for outputting a command signal so as to select the video signal or the fifth video signal, and a fourth video signal and a fourth video signal from the low-pass section according to the content of the command signal from the selection control means. 5. A sub-sampled video signal interpolation processing circuit, comprising: a signal selection unit that selects and outputs any one of the video signals of 5. 2. A cathode ray tube for displaying a fourth video signal or a fifth video signal output from a signal selection section on a screen, wherein the selection control means is operated by an operator who is watching the screen of the cathode ray tube. 2. An interpolation processing device for a sub-sampled video signal according to claim 1, wherein the switch is a changeover switch which is manually operated according to the image quality of the screen. 3. The selection control means issues a command based on the second video signal obtained by sub-sampling by the sub-sampling unit, and the fourth video signal and the fifth video signal generated by the low-pass unit. The sub-sampled video signal interpolation processing circuit according to claim 1, which is for generating a signal. 4. The first low-pass filter of the transmitting-side low-pass filter unit is a vertical low-pass filter, the second low-pass filter of the transmitting-side low-pass filter unit is a two-dimensional low-pass filter, and the low-pass unit is a zero interpolation unit. A vertical low-pass unit for interpolating the third video signal from the above with a vertical low-pass filter to generate a fourth video signal, and a third low-pass filter for interpolating the third video signal from the zero interpolation unit into a first low-pass filter. 5. A sub-sampled video signal interpolation processing circuit according to claim 1, 2 or 3, further comprising a two-dimensional low-pass unit for generating the video signal of FIG. 5. The first low-pass filter of the transmitting-side low-pass filter unit is a vertical low-pass filter, the second low-pass filter of the transmitting-side low-pass filter unit is a two-dimensional low-pass filter, and the low-pass unit is a zero interpolation unit. From the vertical low-pass filter and a horizontal low-pass filter to interpolate the third video signal from the vertical low-pass filter to generate a fourth video signal. The sub-sampled video signal interpolation processing circuit according to claim 1 or 2, further comprising a horizontal low-pass section for generating a video signal. 6. The first low-pass filter is a vertical low-pass filter, the second low-pass filter is a two-dimensional low-pass filter, and the selection control means selects the N-th frame of the third video signal of the zero interpolation unit. A vertical interpolation unit that interpolates with a vertical low-pass filter to generate a first interpolation point; and an N-th frame of the third video signal of the zero interpolation unit is interpolated with a two-dimensional low-pass filter to obtain a second interpolation. A two-dimensional interpolation unit that generates an interpolation point; a first difference unit that generates a difference between the sample point of the (N + 1) th frame of the third video signal and the first interpolation point; A second difference unit that generates a difference between the sample point of the (N + 1) th frame of the video signal and the second interpolation point is compared with a difference between the first difference unit and a difference between the second difference units. If the difference of the first difference portion is less than the difference of the second difference portion, the fourth video signal And a comparison unit that outputs a command signal to select each of the fifth video signals when the difference between the first difference units is greater than or equal to the difference between the second difference units. Item 3. A sub-sampled video signal interpolation processing circuit according to item 3. 7. The vertical low-pass unit, which interpolates the third video signal from the zero interpolation unit with a vertical low-pass filter to generate a fourth video signal, and the third low-pass unit from the zero interpolation unit. And a two-dimensional low-pass section for interpolating the image signal of (1) with a two-dimensional low-pass filter to generate a fifth image signal, and the vertical interpolation section and the two-dimensional interpolation section of the selection control means are respectively:
7. The sub-sampled video signal interpolation processing circuit according to claim 6, wherein the vertical low-pass portion and the two-dimensional low-pass portion of the low-pass portion are used in common. 8. The selection control means comprises a first accumulator for accumulating the output of the first difference section for a plurality of frames to generate a first accumulated value, and an output of the second difference section for a plurality of frames. 7. A second accumulator for accumulating to generate a second accumulative value, wherein the comparator compares the outputs of the first and second accumulators. Item 7. An interpolation processing circuit for sub-sampled video signals according to Item 7. 9. The signal selection section has an average value generation section for generating an average value of the fourth video signal and the fifth video signal, and the selection control means sets the difference between the first difference section and the first difference section. 7. If both of the differences of the two difference units are larger than the specified values, the command signal is output so as to output the average value of the average value generation unit. 7. An interpolation processing circuit for sub-sampled video signals according to 7. 10. A first low-pass filter and a second low-pass filter having a transmittable band different from that of the first low-pass filter as a pre-filter for removing high frequency components of the first video signal which is initially sampled in a square lattice form. A transmission-side low-pass filter unit in which one of the low-pass filters is used, and the first video signal is band-limited by the transmission-side low-pass filter unit and then sub-sampled in a zigzag inter-frame offset state. A second video signal obtained by sub-sampling by the sub-sampling unit is received from a transmission side having a sub-sampling unit, and interpolation processing is performed on the second video signal. A video signal interpolation processing circuit, wherein a zero interpolation unit that generates a third video signal by inserting zero into the second video signal; The third video signal from the interpolator is processed by a low pass filter having a transmittable band corresponding in advance to a transmit band in which the transmittable band of the first lowpass filter and the transmittable band of the second lowpass filter overlap. A sub-sampled video signal interpolation processing circuit, comprising: a low-pass unit that interpolates to generate a fourth video signal. 11. The first low-pass filter section, wherein the low-pass section interpolates the third video signal from the zero interpolation section with a low-pass filter having a transmittable band corresponding to the transmittable band of the first low-pass filter in advance. And a second low-pass filter section for interpolating the signal interpolated by the first low-pass filter section by a low-pass filter having a transmissible band corresponding in advance to a transmissible band of the second low-pass filter. 11. The method according to claim 10,
An interpolation processing circuit for the subsampled video signal described. 12. The first low-pass filter of the transmission-side low-pass filter unit is a vertical low-pass filter, the second low-pass filter of the transmission-side low-pass filter unit is a two-dimensional low-pass filter, and the first low-pass filter of the low-pass unit. The section is for interpolating the third video signal from the zero interpolation section by a vertical low-pass filter, and the second low-pass filter section of the low-pass section is the signal interpolated by the first low-pass filter section. Is further interpolated by a two-dimensional low-pass filter, and the sub-sampled video signal interpolation processing circuit according to claim 11. 13. The first low-pass filter of the transmitting-side low-pass filter unit is a vertical low-pass filter, the second low-pass filter of the transmitting-side low-pass filter unit is a two-dimensional low-pass filter, and the first low-pass filter of the low-pass unit. The section is for interpolating the third video signal from the zero interpolation section by a vertical low-pass filter, and the second low-pass filter section of the low-pass section is the signal interpolated by the first low-pass filter section. 12. The sub-sampled video signal interpolation processing circuit according to claim 11, further comprising: a horizontal low-pass filter.