KR20020016688A - Down sampling method for video signal - Google Patents

Abstract

PURPOSE: A method of down-sampling a video signal is provided to minimize deterioration in a signal due to down sampling. CONSTITUTION: It is judged if the first pixel of a video signal corresponding to a sampling point according to a sampling rate determined for down sampling is a minimum unit. It is judged if the second pixel adjacent to the first pixel is a minimum unit. When it is judged that the first and second pixels are the minimum units, data of the first pixel is processed to be assigned as a down sampling result of the sampling point. When it is judged that one of the first and second pixels is not the minimum unit or both of the first and second pixels are not minimum units, a low pass filtering result with respect to the video signal within a low pass filtering set on the basis of the sampling point is processed to be allocated as the down sampled result of the sampling point.

Description

Down sampling method for video signal

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of down-sampling video signals, and more particularly, to a video signal generated from a device such as a personal computer (hereinafter referred to as a PC), such as a television (hereinafter referred to as TV). A method of downsampling a video signal to convert it to a display format.

In general, a PC video signal has a resolution of 640 × 480 pixels in the case of VGA (Video Graphic Array), a resolution of 800 × 600 pixel in the case of Super VGA (SVGA), and an eXtended Graphic Array (XGA). Has a resolution of 1024 x 768 pixels. On the other hand, NTSC-type SD-TV (Standard Definition-TV) has a resolution of 720x480i (i; interlace) pixels and HD-TV (High definition-TV) generally has a resolution of 1920x1080i pixels. Has Accordingly, in order to display a video signal of a PC through a display device mounted on a TV, format conversion of the video signal is required.

One of the methods used for such a format conversion is a sampling rate conversion method. The sampling rate conversion method up-samples or downsamples a PC video signal according to a sampling rate determined in consideration of the number of pixels of a video signal of a PC applied and the number of pixels of a display format of a corresponding TV. (Down-sampling) to convert to a TV signal. The above-mentioned upsampling is used when the number of pixels of the display format of the TV is larger than the video signal of the PC, and downsampling is used when the number of pixels of the display format of the TV is smaller than the video signal of the PC.

1 is a functional block diagram of a down sampling apparatus for converting a video signal of a conventional PC into a TV format, and includes a minimum unit detection unit 101, a minimum unit determination unit 103, a minimum unit allocation processing unit 105, and low pass filtering. It consists of a part 107.

The minimum unit detector 101 detects the minimum unit when the PC video signal converted from the RGB color signal into the luminance signal and the two color difference signals is applied. The minimum unit is a pixel having a significant difference from the luminance level of pixels adjacent to the left and right or up and down. Therefore, the minimum unit detector 101 compares the luminance levels with pixels adjacent to the left, right, or top and bottom in the pixel unit with respect to the PC video signal sequentially applied, and indicates the minimum unit in the case of a pixel having a difference greater than or equal to a predetermined threshold. Is set and a value indicating that the pixel does not have a difference equal to or greater than a predetermined threshold is not the minimum unit and is output. For example, if the corresponding pixel is the minimum unit, '1' is set, and if the pixel is not the minimum unit, '0' is output.

The minimum unit determination unit 103 refers to a value indicating whether the minimum unit of the pixel unit transmitted from the minimum unit detection unit 101 determines whether the sampling point determined according to the sampling rate according to the PC video signal and the TV display format is the minimum unit. To judge.

That is, referring to an operation flowchart of the minimum unit determination unit 103 shown in FIG. 2 and an exemplary diagram between the sampling point and the PC video signal shown in FIG. 3, the minimum unit determination unit 103 When the sampling point according to the sampling rate corresponds to the position of the hatched X pixel, the value representing the minimum unit of the X-1 point adjacent to the X point among the values transmitted from the minimum unit detector 101 is determined. An algorithm as shown in FIG. 2 is performed using a value representing a minimum unit.

That is, in step 201, it is checked whether X-1 and X + 1 have the same value. As a result of the check, if it has the same value, it is checked in step 202 whether it has a value different from X-1. As a result of the check, if it has a different value, it is checked in step 203 whether the X + 1 and the X value have different values. As a result of the check, if it has a different value, it is determined that the point x is the minimum unit, and the minimum unit determination unit 103 generates a signal for requesting the minimum unit allocation processing. On the other hand, if at least one of the above-described check conditions in steps 201, 202, and 203 is not satisfied, it is determined that the corresponding point is not the minimum unit, and in step 205, the minimum unit determination unit 103 requests the low pass filtering process. Generates a signal.

The minimum unit allocation processing unit 105, when processing is required from the minimum unit determination unit 103 at the sampling point corresponding to the X point in FIG. 3, results of downsampling the video signal of the PC at the X point of the corresponding sampling point. Will output The low pass filtering unit 107 performs low pass filtering on a video signal of a PC that falls within the filtering range set based on the X point when processing is required from the minimum unit determination unit 103 at the sampling point corresponding to the X point of FIG. 3. Outputs one result as the down sampling result of the corresponding sampling point.

Although the above example has been described only in the case of downsampling in the horizontal direction, downsampling may also be performed in the vertical direction. Downsampling in the vertical direction is the same as the downsampling method described above in the horizontal direction except that the pixels of the video signal of the PC which are located above and below the pixel of the PC video signal corresponding to the sampling point are used. It is done.

However, this conventional down sampling method does not obtain a normal down sampling result when the minimum unit is continuously present. That is, when X point of FIG. 3 is the minimum unit and X + 1 is also the minimum unit, in the case of determining whether the minimum unit for the corresponding sampling point is determined by considering only the pixels located at the left and right in the same manner as in FIG. Since a condition of X-1 ≠ X + 1 and X = X + 1 is obtained, although the down sampling result of the corresponding sampling point should be a PC video signal of the X point, the low pass filtered result is output.

4A is an example of an original PC video signal, and FIG. 4B is an example of a result screen obtained when downsampling as shown in FIGS. 1 and 2. As can be seen from the comparison of FIG. 4A and FIG. 4B, according to the conventional down sampling method, the screen of FIG. 4B obtained by cutting a part of the letter 'b' of FIG. 4A is obtained. As described above, the conventional down sampling method does not properly express the signal of the minimum unit when the minimum unit is continuously generated, resulting in signal degradation.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problem. In order to downsample a video signal, such as a PC video signal, the reference range in the video signal is determined when determining whether or not the sampling point of the video signal is the minimum unit. It is an object of the present invention to provide a method for downsampling a video signal to minimize deterioration of the signal due to downsampling.

1 is a functional block diagram of a down sampling apparatus for a conventional PC video signal.

FIG. 2 is a flowchart illustrating an operation of the minimum unit determination unit illustrated in FIG. 1.

FIG. 3 is an exemplary diagram between a video signal and a sampling point of a PC for explaining the operation of the minimum unit determination unit shown in FIG. 1.

4A is an example of an applied PC video signal, and FIG. 4B is an example of a down sampling result obtained through the down sampling apparatus shown in FIG. 1 with respect to an applied PC video signal as shown in FIG. 4A.

5 is an operation flowchart of a down sampling method of a video signal according to the present invention.

6A and 6B are exemplary diagrams between a PC video signal and a sampling point for explaining a down sampling method according to the present invention.

7 is a down sampling result of the PC video signal shown in FIG. 4A when operated in the down sampling method according to the present invention.

<Description of the symbols for the main parts of the drawings>

101: minimum unit detection unit 103: minimum unit determination unit

105: minimum unit allocation processing unit 107: low pass filtering unit

In order to achieve the object of the present invention, the method according to the present invention, in the down-sampling method of the video signal, (a) of the video signal corresponding to the sampling point according to the sampling rate (sampling rate) determined for down sampling Determining whether the first pixel is the minimum unit using a value indicating whether the first pixel is the minimum unit for the plurality of pixels adjacent to the first pixel and the first pixel; (b) a second pixel and a second pixel adjacent to the first pixel; Determining whether the second pixel is the minimum unit using a value indicating whether the minimum unit is a plurality of pixels adjacent to the pixel; (c) if the first pixel is the minimum unit and the second pixel is determined to be the minimum unit, Processing the data of the first pixel to be allocated as a down sampling result of the sampling point; (d) either one of the first pixel and the second pixel is not the minimum unit or both are the minimum; If it is determined that not the above, it is desirable to low-pass filtering result for the pixel data of the video signals fall within the range of low-pass filtering is set based on the sampling points including the step of processing to be assigned to the down-sampling results of the sampling points.

Hereinafter, with reference to the accompanying drawings will be described in detail the present invention.

5 is an operation flowchart of a down sampling method of a video signal according to the present invention, and in particular, an operation flowchart of a minimum unit determination function centered on a sampling point according to a sampling rate.

6A and 6B are exemplary diagrams between a PC video signal and a sampling point for explaining a down sampling method according to the present invention.

A description with reference to FIGS. 5 and 6A and 6B is as follows.

That is, the sampling point determined according to the down sampling rate according to the applied PC video signal and the desired video format (for example, TV display format) is applied to the x point of the PC video signal to which the applied PC video signal is applied. In the case where the minimum unit is detected in pixel units as in the minimum unit detector 101 shown in FIG. 1 with respect to the corresponding PC video signal, the PC video signal at the point X-1 of FIG. 6A in FIG. The result of detecting the minimum unit of the pixel of the pixel and the PC video signal of the X + 1 point of Fig. 6A is compared.

As a result of the comparison, if the two values are the same, a result of detecting whether the pixel of the PC video signal of the PC video signal of point X-1 of FIG. 6A and the pixel of the PC video signal of X point of FIG. 6A is detected in step 502.

As a result of the comparison, if the two values are not the same, the result of detecting whether the pixel of the PC video signal at the X + 1 point in FIG. 6A and the pixel of the PC video signal at the point X in FIG. 6A is detected in step 503 is compared. .

As a result of the comparison, if the two values are not the same, the result of detecting whether the pixel of the PC video signal at the point X of FIG. 6A and the pixel of the PC video signal at the point X + 2 of FIG. 6A is detected in step 504.

As a result of comparison, in step 505, the result of detecting whether the pixel of the PC video signal at the point X of FIG. 6A and the pixel of the PC video signal at the point X + 1 of FIG. 6A is detected is compared. As a result of the comparison, if it is not the same, a result of detecting whether the pixel of the PC video signal at the X + 1 point of FIG. 6A and the pixel of the PC video signal at the X + 2 point of FIG. 6A is detected in step 506. If the comparison result is the same, the minimum unit allocation processing is required so that the down sampling result for the corresponding sampling point in step 507 is the result of the minimum unit allocation processing. Accordingly, the operation result of the minimum unit allocation processing unit 105 shown in FIG. 1 is output as the down sampling result of the corresponding sampling point.

On the other hand, if the result of checking in steps 501 to 506 does not satisfy at least one condition, the low pass filtering process is required so that the low pass filtered result in step 508 can be provided as a down sampling result of the corresponding sampling point. . Accordingly, the low pass filtering unit 107 shown in FIG. 1 outputs the filtering result for the video signal belonging to the filtering range set for the applied PC video signal as the down sampling result of the corresponding sampling point.

As described above, when down-sampling in the horizontal direction, the PC video signal corresponding to the corresponding sampling point is referred to the X and the PC video signal corresponding to the pixels X-1 and X + 1 adjacent to the left and right are referenced. The minimum unit for the corresponding sampling point is determined by using pixels X and X + 2 adjacent to the left and right based on the pixel X + 1 corresponding to +1 pixel in the horizontal direction.

Meanwhile, even when downsampling in the vertical direction, a reference range for determining the minimum unit for the corresponding sampling point is set and operated as in the horizontal direction.

That is, as can be seen from the exemplary diagram between the sampling point shown in FIG. 6B and the applied PC video signal, when the PC video signal corresponding to the corresponding sampling point is a pixel at the Y point, the reference range is Y−. Pixels of one point to pixels of Y + 2 and each pixel present in the vertical direction are subjected to check conditions as shown in the flowchart of FIG. 5 to obtain a down sampling result for the sampling point. In FIG. 6B, Y-1 corresponds to X-1 in FIG. 6A, Y in FIG. 6B corresponds to X in FIG. 6A, Y + 1 in FIG. 6B corresponds to X + 1 in FIG. 6A, and FIG. Y + 2 corresponds to X + 2 of FIG. 6A.

By performing down sampling according to the result of performing the minimum unit determination on the sampling point in the horizontal and vertical directions as described above, the down sampling result for the PC video signal shown in FIG. 4A is obtained as shown in FIG. 7. .

As described above, according to the present invention, the minimum unit determination result for the pixels of the PC video signal corresponding to the sampling point according to the sampling rate and the minimum unit determination result for the pixels of the PC video signal adjacent to the sampling point are considered. Accordingly, by implementing the minimum unit allocation process and the low pass filtering process for the corresponding sampling point, it is possible to minimize the deterioration of the signal due to the down sampling.

Claims (2)

In the down sampling method of a video signal, (a) using a value indicating whether the first unit of the video signal corresponding to a sampling point according to a sampling rate determined for the down sampling and the minimum unit of a plurality of pixels adjacent to the first pixel is used; Determining whether the first pixel is a minimum unit; (b) determining whether the second pixel is the minimum unit by using a value indicating whether the second pixel adjacent to the first pixel and the plurality of pixels adjacent to the second pixel is the minimum unit; (c) if the first pixel is the smallest unit and the second pixel is the smallest unit, processing the data of the first pixel to be allocated as a down sampling result of the sampling point; (d) if it is determined that either one of the first pixel and the second pixel is not the minimum unit or not the minimum unit, the pixel data of the video signal within the low pass filtering range set based on the sampling point is determined. And processing the low pass filtering result to be assigned to the down sampling result of the sampling point. The pixel of claim 1, wherein when the down sampling is performed in a horizontal direction, pixels adjacent to the first pixel and the second pixel become pixels adjacent to left and right of the corresponding pixel, and the second pixel includes the first pixel. And a pixel of the video signal at a position shifted by +1 pixel in the horizontal direction with respect to the reference. When the down sampling is performed in the vertical direction, pixels adjacent to the first pixel and the second pixel are corresponding pixels. And a second pixel is a pixel of the video signal at a position shifted by +1 pixel in the vertical direction with respect to the first pixel.