KR101029466B1 - System of transmitting-receiving with dual video signal and operating method thereof - Google Patents

Abstract

According to an embodiment of the present invention, two video signals photographed and synthesized are respectively transmitted from a received signal and separated from the received signals. The present invention recovers and outputs an interpolation method. Image transmission and transmission means for converting, filtering, synthesizing, and compressing and encrypting digital video signals and transmitting them through the PII communication path, decompressing and decoding the received digital video signals, separating them into first and second video signals, Receiving display means for restoring and outputting an analog video signal, and a communication path for connecting the image pickup transmitting means and the receiving display means to any one selected from a wireless LAN and a wired LAN of the POE method, the two video signals at once Reduces the load on the communication line and transmits the received video signal. Since the video signal is separated into each video signal and interpolated, the video signal is restored to the original video signal.

Image, filtering, sampling, synthesis, compression, encryption, decryption, interpolation

Description

Multiple video signal transmission and reception system and its operation method {SYSTEM OF TRANSMITTING-RECEIVING WITH DUAL VIDEO SIGNAL AND OPERATING METHOD THEREOF}

The present invention synthesizes video signals taken by two cameras, transmits them by one path, receives and separates them, and outputs them. Particularly, two video signals photographed by each camera are combined with sampling and transmitted. The present invention relates to a plurality of video signal transmission / reception systems and a method for operating the same.

The general camera CAMERA includes one lens (LENS) means and an image pickup device means, and photographs one image, and transmits the signal of the photographed image through one communication line. Therefore, two transmission lines or two communication lines are used to transmit two video signals captured by two cameras.

In addition, the lens means of the camera is different depending on the characteristics, but the maximum angle of view (angle) that can be taken at one time is generally not more than 180 degrees even when using a fisheye lens, about 60 degrees angle range is standard to be. Therefore, at least two cameras should be provided to shoot a wide range.

In the case of monitoring a wide range by the example of the prior art, it is common to have two cameras, one camera to photograph the left region and the other camera to photograph the right region, respectively. Therefore, there is a problem that the purchase cost and installation cost of the camera is approximately doubled.

As a solution to some of the problems of the prior art, there is a panoramic camera that photographs a wide range of angles with one camera. However, since the panoramic camera is a special purpose camera, the price is relatively expensive, maintenance costs are high, and there are still problems such as how to use the camera.

In addition, to solve some of the problems of the prior art, there is a speed dome camera that uses a general-purpose general-purpose camera and shoots a certain distance over time.

The improved speed dome camera of the prior art has the advantage of using a general-purpose camera, but there are problems such as relatively expensive, bulky, noise and heat generated by driving the motor.

In addition, because the format of the continuous shooting while moving the camera, instead of capturing a large area of video at the same time, the power consumption is large, there is a lot of causes of failure, there is a problem in use to shoot a number of scenes while moving if necessary.

In addition, the video signal photographed by the prior art, for example, has a problem that twice the transmission time is required even when photographing a designated large area twice and processing it digitally.

Therefore, it is necessary to develop a technique for photographing video signals in different directions with one camera, synthesizing and transmitting them into one video signal, and demodulating each video on the receiving side.

In order to solve the problems and necessity of the prior art as described above, the present invention provides a plurality of video signal transmission and reception system and operation method comprising two imaging means in one camera and synthesizing and transmitting the video signal photographed in each frame. The purpose is to.

Another object of the present invention is to provide a multiple video signal transmission / reception system and an operation method for separating and synthesizing the synthesized video signal and outputting each one selected from among linear interpolation, bilinear interpolation, and six tap interpolation.

In order to achieve the above object, the present invention converts the first and second analog video signals photographed at different positions designated by the first and second imaging units, respectively, into digital video signals, filters and synthesizes them, and compresses and encrypts them. Decompressing and decoding the digital video signal received through the POE communication path from the imaging transmission means, decompressing and decoding the first and second video signals, and restoring each by interpolation. A video signal transmission / reception system having a plurality of image pickup means including a reception display means for outputting an analog video signal, and a communication path connecting the image pickup transmission means and the reception display means to any one selected from a POE-type wireless LAN and a wired LAN.

Preferably, the image pickup transmitting means comprises: a first image pickup unit for shooting an object as an analog image signal at a designated position, a first AD unit for converting the analog image signal captured by the first image pickup unit into a digital image signal, and a first image pickup unit A second imaging unit for photographing an object specified at a position different from the second image unit, a second AD unit for converting the analog image signal captured by the second imaging unit into a digital image signal, a first AD unit and a second AD unit A filter synthesizer which removes noise components from each of the digital video signals applied from the filter and filters them to a size of 1/2, and a transmission control unit and a transmission control unit which receive, compress, and encrypt the digital video signal synthesized from the filter synthesis unit. Connects the digital video signal to any one selected from POE-type wired LAN and wireless LAN and transmits in matched state Doedoe is configured to include a transmission, the transmission control unit controls and monitors the first image capturing unit, a first eyidi bitter, and the second imaging unit, a second eyidi bitter, the filter combining unit and operation of the transmission.

The first imaging unit and the second imaging unit are configured to select one of the same objects as the other objects and to photograph each of them.

Here, compression and encryption of the transmission control unit include the MPEG-4 (MPEG-4) system.

On the other hand, the reception display means is a receiving unit for receiving a digital video signal in a matched state by any one selected from the image pickup transmitting means of the POE type wired LAN and wireless LAN, and a receiving control unit for decompressing and decoding the digital video signal applied from the receiving unit And a separate interpolation unit which separates the digital video signal applied from the reception control unit into first and second video signals, and processes the signal by interpolation to restore the original size, and receives the digital first video signal from the separation interpolation unit. A first deciding unit converting the analog image signal, a first display unit receiving the first image signal from the first deciding unit, and displaying the first image signal as a visual image signal, and receiving a digital second image signal from the separation interpolation unit. Applying the second video signal from the second deciphering unit and the second deciding unit converting to a signal And a second display unit for receiving and displaying a visual image signal, wherein the reception controller controls and monitors an operation of the receiver, the separation interpolator, the first decision unit, the first display unit, the second decision unit, and the second display unit.

The first display unit and the second display unit include at least one selected from an LCD monitor, an LED monitor, and a projection device.

The interpolation method is any one selected from linear interpolation, bilinear interpolation, and six tap interpolation.

In order to achieve the above object, the present invention provides a method for operating a video signal transmission / reception system including an image pickup means, a reception display means, and a communication path, wherein two objects each of which are designated by the image pickup means are different. A second step of simultaneously capturing, converting, filtering, and synthesizing the digital video signal at the same time; and compressing and encrypting the synthesized video signal, transmitting the received video signal to one of the PII-type wired and wireless LANs, and receiving at the destination. And a third step of decompressing and decoding the video signal received through the PII communication path, separating the first and second video signals, and restoring the interpolation method, respectively. And a plurality of imaging means comprising a fourth step of converting the video signal into a display portion and outputting it to the display unit. It proposes a method of operating a video signal transmission system.

Preferably, the synthesis is performed in the state of filtering by specifying the frame unit pixels of the first and the second video signal respectively alternately, and the separation is the first and second video signal by sequentially specifying each pixel of the synthesized video signal The video signal is recovered by interpolation.

On the other hand, the interpolation method is any one selected from linear interpolation, bilinear interpolation, and six tap interpolation.

According to the present invention having the above-described configuration, since each image pickup means selects one frame unit pixel of the image signal photographed one by one and synthesizes it in a filtered state at 1/2 size, it transmits two image signals at once. There is an industrial effect of reducing the load on the track.

In addition, the present invention having the above-described configuration separates the received video signal into the respective video signal in the state where the two are synthesized, and the interpolation process has an effect that is convenient in use to recover the video signal by the original frame.

The terms or words used in this specification and claims are not to be construed as limiting in their usual or dictionary meanings, and the inventors may properly define the concept of terms in order to best explain their invention in the best way possible. It should be interpreted as meaning and concept corresponding to the technical idea of the present invention. In addition, detailed description of well-known functions and configurations that are determined to unnecessarily obscure the subject matter of the present invention will be omitted.

POE (POE: POWER OVER ETHERNET), also known as Active Ethernet, is a method of not supplying power separately through a CAT 5 Ethernet cable to an AP (ACCESS POINT) constituting a wireless LAN and a network device constituting a wired LAN. In other words, the POE method provides a data and direct current power supply to a CAT 5 Ethernet cable at the same time, which provides flexibility in network configuration and greatly reduces installation and maintenance costs. DC voltage supplied varies from 12V, 6V and 5V, and the IEEE sets 48V as the standard voltage. The use of a high voltage has the advantage of reducing the amount of current. Generally, RJ-45 jack is composed of 8 lines, uses 4 lines for transmission and reception, and supplies DC power using 4 unused lines. Therefore, equipment using RJ-45 jack is POE compatible or It is called an active Ethernet compatible device. The communication equipment using the PII communication path is characterized in that it must have a fault protection circuit function to immediately cut off the supply of DC voltage to the cable when a failure occurs. Even when a failure occurs, there is a method of monitoring the failure status and automatically recovering when the failure is removed and manually pressing the recovery button.

Interpolation (INTERPOLATION) is a method of determining or estimating a desired value from a known value by SMOOTH or CONTINUOUS. For example, when X1 <X <Xn, it is called interpolation or interpolation to obtain the value of X using the X1 value and the Xn value. On the other hand, obtaining X value when X1> X or X> Xn is called extrapolation or extrapolation. In the present invention, since the interpolation method is used, only the interpolation method will be described. In the present invention, any one selected from a linear interpolation method, a bi-linear interpolation method, and a six tap (SIX-TAB) interpolation method is used. Linear interpolation, also called linear interpolation, is a method of estimating the value between two points of a given linear at equal intervals or an unequal interval using a triangular shape. . Bi-linear interpolation is the most common interpolation method. The values are calculated by multiplying four adjacent values by weight, and calculating the sum by using a linear method. At this time, the weight value is applied differently according to the adjacent size value. Since six-tap interpolation is a method that adds the values calculated by applying weights to six adjacent values and calculates them by linear method, it has the advantage of estimating or determining the value of SMOOTH or CONTINUOUS. Adopted by .264 / AVC, high reliability but long operation time. In the present invention, since one of the linear interpolation method, the bilinear interpolation method, and the six tap interpolation method is selected and applied, the computation speed is relatively flexible.

MPEG-4 compresses digital signals at very high compression rates and transmits them at very low bit rates. It is an asymmetric method that takes relatively long time to compress and relatively little time to decompress or decompress. Therefore, it is relatively difficult to apply when concurrency or real time is required. MPEG-4 compression in video signals uses similarities between adjacent frames, i.e., it uses prediction and interpolation to compensate for motion or motion in an image. The MPEG 4 regularly includes I frames, P frames to be predicted, and B frames to be interpolated into a clean image including all video signals.

1 is a functional configuration diagram of a video signal transmission / reception system having a plurality of imaging means, according to an example of the present invention.

Hereinafter, the attached drawings will be described in detail and includes an image pickup and transmission means 100, a reception display means 200, and a communication path 300.

The image transmitting means 100 is configured to convert the first and second analog image signals captured by the first image capturing unit 110 and the second image capturing unit 130 at different positions into a digital image signal. Converted, filtered, and sampled (hereinafter, referred to as "filtering"), synthesized, compressed, encrypted, and transmitted through a POE (POE) communication path, the first imaging unit 110, the first AD (ADC) It comprises a ANALOG TO DIGITAL CONVERT unit 120, a second imaging unit 130, a second AD unit 140, a filter synthesis unit 150, a transmission control unit 160, and a transmission unit 170.

The first image capturing unit 110 and the second image capturing unit 130 capture images by designating different positions on the same line. At this time, the first image capturing unit 110 and the second image capturing unit 130 are fixed at right angles on the same line, while being spaced apart by any one value selected from a range of 5 to 10 centimeters, and photographing the same object at the same time. In this case, stereoscopic images can be taken.

The first AD unit 120 converts the analog image signal photographed by the first imaging unit 110 into a digital image signal, and the second AD unit 140 converts the analog image signal photographed by the second imaging unit 130. Is converted into a digital video signal.

The filter synthesis unit 150 removes noise components from the digital image signals applied from the first AD unit 120 and the second AD unit 140 and samples the samples to 1/2 size to synthesize them. COMPOSITION). In the sampling of the digital video signal, each pixel (PIXEL, pixel) in the frame (FRAME) unit constituting the video signal is sequentially selected and selected so that the number of sampled pixels is 1/2. In synthesizing, each pixel of the first and second video signals sampled at the size of 1/2 is sequentially selected so that the video signal is one completed size. That is, the video signal synthesized in units of frames is transmitted through one communication line or communication path.

The transmission control unit 160 compresses, compresses, and transmits the video signal applied from the filter synthesis unit 150, and simultaneously controls and monitors the operation of each functional unit constituting the imaging transmission means 100. The compression and encryption can be applied to the MPEG4 scheme, and alternatively or additionally applied.

The transmitter 170 connects and transmits the digital video signal applied from the transmitter controller 160 to any one selected from a wireless LAN and a wired LAN, which are PIO communication paths, in a matching state.

The PIO method is a method of supplying DC operating power together through a digital signal transmission cable, so if a short circuit occurs in the cable or a fault occurs in either the transmitting or receiving side. A fault protection circuit is provided to protect the equipment, power supply and data transmission / reception circuits. That is, the fault protection circuit always monitors the power supply line state and cuts off the supply of the operating power immediately when an abnormal voltage is detected, and continuously monitors the line even in the interruption state to confirm whether the fault has been recovered. Automatically restart the supply of the operating power or generate a corresponding message so that the user manually operates the button so that the supply of the operating power is resumed. In the present invention, any one function is provided by selection. At this time, CAT 5 cable is generally used and RJ-45 connector can be used. In the present invention, it is preferable to use an RJ-45 connector.

The reception display means 200 decompresses, decodes, and decompresses a digital video signal received through a PII communication path, and separates the synthesized video signal into a first video signal and a second video signal. The receiver 210, the reception controller 220, the separation interpolator 230, the first DIACTAL TO ANALOG CONVERT (DAC) unit 240, and the first display unit are restored by the interpolation method. The configuration includes a 250, a second die unit 260, and a second display unit 270.

Receiving unit 210 is connected to any one selected from the wireless LAN and the wired LAN, which is the POE-type communication path, and inputs the received digital video signal in the matching (MATCHING) state, and the remaining functions are the same as the description of the transmitting unit 170 to omit Shall be.

The reception control unit 220 decompresses the digital video signal received by the reception unit 210 in the matching state, releases the encryption state through decryption, and simultaneously controls and monitors the operation of each functional unit of the reception display means 200. To control and monitor the operation. The MPEG4 scheme is applied to the decompression and decoding, and the same applies when the other scheme is alternately applied or additionally applied at the transmitter.

The separation interpolator 230 separates the digital video signal applied from the reception controller 220 into a first video signal and a second video signal. In this case, the separating method is determined by a method in which the first and second video signals are synthesized by the filter synthesizing unit 150, that is, the video signals are separated according to the video signal synthesizing method of the filter synthesizing unit 150. The method is determined. Since the separated first video signal and the second video signal are each composed of sequentially selected pixels, the pixels of the empty part are interpolated. Here, the method used for interpolation is interpolated by any one method selected from linear interpolation method, bilinear interpolation method, and six tap interpolation method.

The selection of interpolation method can be applied differently depending on the area of the vector value or the color change due to the movement of adjacent pixels, the appropriate area, or the area that is changed severely. Apply. This reference value is preferably determined by repeated experiments and can be recorded and managed in a table in the corresponding memory area and updated with new values. That is, an appropriate interpolation method is selected and applied according to a corresponding region of the video signal among the three interpolation methods, or any one interpolation method is applied to the entire video signal for each frame unit, or one selected interpolation method is applied to all frames of the video signal. Applicable to This application method is preferably applied to the method that is considered appropriate by repeated experiments. Since the processing method of each interpolation method has been described above in detail, repeated descriptions are avoided.

The first decision unit 240 receives the first interpolated first digital video signal separated from the separation interpolation unit 230 and converts the first digital video signal into an analog video signal. The second decision unit 260 is separated from the separation interpolation unit 230. The separated and interpolated second digital video signal is applied and converted into an analog video signal.

The first display unit 250 displays the image signal applied from the first deciding unit 240 as a visual image signal, and the second display unit 270 displays the image signal applied from the second deciding unit 260. It is displayed as an image signal, and is made of any one selected from an LCD (Liquid Crystal Display) monitor, an LED (Light Emitting Display) monitor, and a projection apparatus. The same applies to other types of projection devices that are not described. Meanwhile, the first and second display units 250 and 270 may be separated, and may be combined into one.

2 is an explanatory diagram of a method of synthesizing the first and second video signals according to an example of the present invention.

Hereinafter, with reference to the accompanying drawings, the first digital video signal frame, which is an image signal photographing a state of holding a flower, is, for example, a total of 20 pixels by 4 pixels and 5 pixels. Is done. At this time, a total of 10 pixels remain in units of frames through filtering to select pixels in the odd number.

On the other hand, the digital second image signal frame for capturing a silhouette image of a human is composed of a total of 20 pixels by 4 pixels horizontally, 5 pixels vertically. In this case, a total of 10 pixels remain in units of frames through filtering to select pixels in even-numbered positions.

Ten pixels of the odd positions where the first video signal is filtered and ten pixels of the even positions where the second video signal is filtered are respectively filled in the empty positions and synthesized into the video signals by one frame. The synthesized video signal is compressed and encrypted in an MPEG 4 scheme and transmitted through a wireless LAN or a wired LAN, which is a POE communication route.

3 is an explanatory diagram of a method of recovering the first and second video signals synthesized and compressed according to an example of the present invention.

Hereinafter, with reference to the accompanying drawings, the synthesized and compressed video signals are decompressed and decoded by the MPEG 4 method, and the odd numbered video signals are removed from the pixels constituting the video signal in units of frames. The video signal is separated into one video signal, and the even-numbered video signal is separated into a second video signal. Since the separated first video signal and the second video signal are each restored by the selected interpolation method, the number of pixels according to the original frame size is obtained. The first video signal separated and signal-processed according to the interpolation method is a video signal with a flower in the hand, and the second video signal is a human silhouette video signal and is output through a designated channel or path.

4 is a flowchart illustrating a method of operating a video signal transmission / reception system having a plurality of imaging means, according to an example of the present invention.

Hereinafter, with reference to the accompanying drawings in detail, by means of the image transmitting and receiving means of the video signal transmission and reception system to photograph the other object specified for the first video signal and the second video signal, respectively, and converts to a digital video signal of the frame unit and noise The first video signal and the second video signal, which have been converted into a video signal having a unit size of 1/2, are synthesized through filtering processing to remove the signal and sequentially select alternately to form a video signal by one frame (S110). .

The synthesized frame-based video signal is compressed and encrypted in an MPEG 4 scheme and transmitted to a destination through a wireless LAN or a wired LAN of a POE-type communication path, and received by the reception display means of the corresponding destination (S120).

The reception display means decompresses and decodes the received video signal using the MPEG 4 method, and separates the received video signal into a first video signal and a second video signal (S130).

The separated first image signal and the second image signal are respectively restored to the corresponding interpolation method selected from linear interpolation, bilinear interpolation, and six tap interpolation (S140).

The digital first video signal and the second video signal restored as described above are converted into analog video signals and output to the display unit so as to be visually confirmed (S150).

Therefore, by filtering the first and second video signals photographed at different locations, the size of the pixel is reduced to 1/2, combined, and transmitted at once in one path, and the receiving side is separated into the first and second video signals. Since the signal is processed by interpolation, the pixel is restored to its original size.

Although the present invention has been described in detail only with respect to the described embodiments, it will be apparent to those skilled in the art that various changes and modifications can be made within the technical scope of the present invention, and such modifications and modifications belong to the appended claims.

1 is a functional configuration diagram of a video signal transmission / reception system having a plurality of imaging means, according to an example of the present invention;

2 is an explanatory diagram of a method of synthesizing the first and second video signals according to an example of the present invention;

3 is an explanatory diagram of a method of recovering the first and second video signals synthesized and compressed according to an example of the present invention;

And

4 is a flowchart illustrating a method of operating a video signal transmission / reception system having a plurality of imaging means, according to an example of the present invention.

          ** Explanation of symbols on the main parts of the drawing **

100: image pickup unit 110: first image pickup unit

120: first ADC unit 130: second imaging unit

140: second ADC unit 150: filter synthesis unit

160: transmission control unit 170: transmission unit

200: receiving display means 210: receiving unit

220: reception control unit 230: separation interpolation unit

240: first ADC unit 250: first display unit

260: second ADC unit 270: second display unit

300: communication path

Claims (10)

Imaging transmission means for converting, filtering, synthesizing, compressing, and encrypting the first and second analog video signals photographed at different positions designated by the first and second imaging units, respectively, and compressing and encrypting the signals, and transmitting them through a PII communication path; Receiving display means for decompressing and decoding the digital video signal received from the image pickup transmitting means in the PII communication path, separating the first video signal into first and second video signals, and restoring the interpolation method to output the analog video signal; And A communication path connecting the image pickup means and the receiving display means to any one selected from a POE-type wireless LAN and a wired LAN; Video signal transmission and reception system having a plurality of imaging means comprising a. The method of claim 1, wherein the image pickup means, A first imaging unit which photographs an object with an analog image signal at a designated position; A first AD unit which converts the analog image signal photographed by the first imaging unit into a digital image signal; A second imaging unit which captures a designated object at a position different from the first imaging unit as an analog image signal; A second AD unit which converts the analog image signal photographed by the second imaging unit into a digital image signal; A filter synthesizing unit for removing noise components from the digital image signals applied from the first AD unit and the second AD unit, and filtering them to a size of 1/2; A transmission controller which receives, compresses and encrypts the digital video signal synthesized from the filter synthesis unit; And A transmitter for connecting the digital video signal applied from the transmission controller to any one selected from a POE-type wired LAN and a wireless LAN and transmitting in a matched state; Consists of including The transmission control unit controls and monitors operations of the first imaging unit, the first AD unit, the second imaging unit, the second AD unit, the filter synthesizing unit, and the transmitter. Video signal transmission and reception system provided. The method of claim 2, wherein the first imaging unit and the second imaging unit, A video signal transmission and reception system having a plurality of imaging means, characterized in that it is configured to select one of the same object and the other object and to photograph each. The method of claim 2, wherein the compression and encryption of the transmission control unit, An image signal transmission / reception system provided with a plurality of imaging means, characterized in that the MPEG-4 (MPEG-4) system is included. The method of claim 1, wherein the reception display means, A receiving unit for receiving a digital video signal in a matching state by any one selected from a POE-type wired LAN and a wireless LAN from the image pickup transmitting means; A reception controller which decompresses and decodes the digital video signal applied from the receiver; A separation interpolation unit for dividing the digital video signal applied from the reception control unit into first and second video signals, and performing signal processing by interpolation to restore the original size; A first die unit which receives the digital first image signal from the separation interpolation unit and converts the digital first image signal into an analog image signal; A first display unit receiving a first image signal from the first die unit and displaying the first image signal as a visual image signal; A second die unit which receives the digital second video signal from the separation interpolation unit and converts the second video signal into an analog video signal; And A second display unit receiving a second video signal from the second die unit and displaying the second video signal as a visual video signal; Consists of including And the reception control section controls and monitors the operation of the reception section, the separation interpolation section, the first decision section, the first display section, the second decision section, and the second display section. Video signal transmission and reception system. The display apparatus of claim 5, wherein the first display portion and the second display portion An image signal transmission / reception system having a plurality of imaging means, characterized in that the configuration consisting of at least one selected from the LCD monitor, the LED monitor and the projection apparatus. The method of claim 5, wherein the interpolation method, A video signal transmission / reception system having a plurality of imaging means, characterized in that any one selected from linear interpolation method, bilinear interpolation method, six tap interpolation method. In the operating method of the video signal transmission and reception system comprising image pickup transmitting means, receiving display means, communication path, A first step of photographing the objects designated by the image pickup means at two different positions, converting them into digital video signals, filtering and synthesizing them; A second step of compressing and encrypting the synthesized video signal, transmitting the received video signal to any one selected from a PIO-type wired LAN and a wireless LAN; A third step of decompressing and decoding the video signal received by the PIO method, separating the first and second video signals into interpolation methods, respectively; And A fourth step of converting the first and second video signals respectively restored by the interpolation method into analog video signals and outputting the analog video signals to the display unit; Operating method of a video signal transmission system having a plurality of imaging means comprising a. The method of claim 8, The synthesizing is performed by alternately designating and filtering frame unit pixels of the first and second video signals, respectively, and the separation is sequentially designating each pixel of the synthesized video signal by alternately designating the first and second video signals. And a plurality of image pickup means for recovering the separated video signals by interpolation. The method of claim 9, wherein the interpolation method, A method of operating a video signal transmission system having a plurality of imaging means, characterized in that any one selected from linear interpolation, bilinear interpolation, six tap interpolation.

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