KR20040084390A - Scan converter of video signal - Google Patents

Abstract

PURPOSE: A scan converter for a video signal is provided to process an input analog signal as the video signal with high image quality of a DVD(Digital Versatile Disk) level. CONSTITUTION: A power supply unit(600) supplies a driving power to each system. A signal converting and dividing unit(200) synthesizes an external analog video signal from a video/audio input unit(100) with a timing clock by the driving voltage obtained from the power supply unit, receives the first digital video signal, and corrects the received digital video signal. The signal converting and dividing unit divides the corrected first digital video signal into a color signal and a luminance signal, and outputs the color signal and the luminance signal. A clock generating unit(700) receives vertical and horizontal synchronous signals of the corrected first digital video signal, generates the timing clock, a system clock and an output pixel clock, and provides the timing clock to the signal converting and dividing unit. A signal reinforcing unit(300) reinforces the color signal and the luminance signal of the signal converting and dividing unit according to the timing clock of the clock generating unit. A multi-data output unit(400) corrects damaged data from the color signal and the luminance signal of the first digital video signal inputted from the signal reinforcing unit according to the output pixel clock, and outputs the first digital video signal with certain bits. The multi-data output unit outputs the first digital video signal and the second digital video signal as the first and second analog video signal with high image quality. A system control unit(500) receives the second video signal of a computer and the first digital video signal corrected in the multi-data output unit, and controls the multi-data output unit to output the first analog video signal or the second analog video signal.

Description

Scan Converter of Video Signals {SCAN CONVERTER OF VIDEO SIGNAL}

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scan converter for a video signal capable of obtaining a high quality output video signal for an external input video signal. More particularly, the present invention relates to damaged data from an analog video signal or various low quality video input signals. Scanning converters for video signals that make it possible to select, output, and display high-definition digital or analog video signals of various standards on various video output devices with different specifications by correcting them. It is about.

With the recent development of multimedia, NTSC or PAL type of video cassette recorder (VCR), digital video disc (DVD), video game machine or video camera which is used for home video output device displaying image of personal computer or workstation There is an increasing demand for displaying natural images or further displaying high quality television signals or image information signals in personal computers.

However, the horizontal scanning frequency of the video signal of a personal computer or the like is mostly 24 KHz or more, whereas the horizontal scanning frequency of the NTSC or PAL method is 15.75 KHz. If the video output device side of the personal computer attempts to correspond to the horizontal scanning frequency of 15.75 KHz, the burden on the horizontal deflection circuit becomes large, resulting in deterioration of image quality such as increase of picture distortion. Therefore, the INTERLACED SCANNING signal is converted into a PROGRESSIVE SCANNING signal and displayed on the video output device of the personal computer, or conversely, the sequential scan signal of the personal computer is converted into an interlaced signal to output the image of the television receiver. Scan converters having a video decoder to display on the device are each considered.

In addition, in the scan converter, the video decoder converts an external analog video signal into a digital signal through an analog / digital converter, separates the converted digital signal into a luminance signal and a color signal, and converts the digital video data into digital image data. The image is displayed on the device side.

However, one scan converter having a video decoder according to the related art described above converts an interlaced signal into a sequential scan type signal and displays it on the image output device of a computer. It converts a sequential scan signal into an interlaced signal and displays it on a video output device of a television. Thus, a single scan converter can be used for a computer video output device, a television, or a very large home video system (S-VHS). Display only on the image output device of projection), and the economic burden of having to provide the respective scan converters to apply to all the image output devices such as a video camera, a video game machine, a color cathode ray tube, a TFT-LCD, a PDP, etc. There is a problem.

In addition, since various functions such as gamma correction are not built into the scan converter, image quality is extremely degraded due to gamma characteristic correction and various types of analog video signals cannot be output for the input video signal.

Therefore, while recovering from the above problems, various kinds of computers, televisions, projection TVs, TFT-LCDs, color cathode ray tubes, It is desirable to provide a scan converter for video signals that makes it possible to display video signals of various standards on all video output devices having different specifications such as video game machines and video cameras.

Accordingly, an object of the present invention is to correct the damaged data from an external analog signal such as a video camera, a TV, a VCR and a video game machine or an input analog video signal of low image quality to a high definition digital signal of DVD level to all video output devices having different specifications. It provides a scan converter of a video signal that can be displayed, which corrects corrupted data from an external input analog video signal, enhances the corrected digital video signal more clearly, and then sequentially scans the digital video output format. Correspondingly, this is achieved by converting and outputting an analog video signal of various types of high definition with the best resolution.

Another object of the present invention is to provide a scan converter for a video signal provided with the convenience of using an input power source without a separate adapter, and the scan converter uses a universal serial bus (USB) port of a personal computer. , Is achieved.

It is still another object of the present invention to provide a scan converter for a video signal which can be used for both input and output of a video signal through a single cable, and can simultaneously operate a video game machine and a computer.

Other objects of the present invention will become more apparent from the following detailed description and the accompanying drawings.

1 is a block diagram schematically illustrating an embodiment of a scan converter of a video signal according to the present invention;

FIG. 2 is a block diagram illustrating in detail the scan converter of the video signal of FIG. 1.

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

100: video / audio input unit 200: signal conversion separation unit

210: input selector / clamping unit 220: analogue / digital converter

230: gamma correction unit 250: color signal separation unit

260: luminance signal separation unit 300: signal reinforcement unit

310: color demodulation control unit 320: color correction

330: luminance correction 340: data ratio conversion unit

400: multiple data output unit 420: data output format unit

According to a scan converter of a video signal according to the present invention for achieving the above objects, in a scan converter having a video decoder connected to an external video output device to obtain an output video signal different from the input video signal:

Power supply means selectively connected to a universal serial bus (USB) port of a computer to supply operating power to each system;

The external analog video signal is inputted from the video / audio input unit as the first digital video signal in synchronization with the timing clock by the operating voltage obtained by the power supply means, and is corrected by separating the corrected first digital video signal. Signal conversion separating means for outputting a signal;

Clock generation means for receiving the corrected vertical and horizontal synchronization signals of the first digital video signal and generating a timing clock, a system clock, and an output pixel clock, respectively, to provide the timing clock to the signal conversion separation means;

Signal reinforcing means for reinforcing the color signal and the luminance signal of the signal conversion separating means more clearly in accordance with the timing clock of the clock generating means;

First, high-definition, high-quality images and a second digital video signal inputted in the progressive scan mode from the computer by correcting the damaged data from the color signal and the luminance signal of the first digital video signal input from the signal reinforcing means according to the output pixel clock; Multiple data output means for converting and outputting a second analog video signal;

A system control for controlling the multi data output means to receive the second digital video signal of the computer and the first digital video signal corrected by the multi data output means and output the first digital video signal or the second analog video signal; Means;

In this way, the digital video signal is divided into a video signal (R, G, B) or a composite video signal (CVBS), a super video signal (S-VHS), etc., which are separated into luminance and color signals from the outside. Enhances color, saturation and brightness, corrects corrupted data, and outputs the highest quality analog video signal with the highest resolution corresponding to the progressive scan digital video output format, and the progressive scan mode input from an external computer. It can be seen that the digital video signal can be displayed on the image output apparatus according to the user's intention.

As a result, analog video signals of various modes are input and processed into analog video signals of high-definition sequential scanning mode, thereby outputting not only televisions or projection TVs but also video cameras, color cathode ray tubes (CPT), and thin film transistor liquid crystal monitors (TFT-). It can be connected to all video output devices with different specifications such as LCD, Plasma Display Panel (PDP), etc., and can be operated by power supplied from an external computer without an adapter. There is an advantage that the signal can also be input.

And, there may be a plurality of embodiments of the present invention, the following most preferred embodiments will be described in detail.

Through this preferred embodiment, it is possible to better understand the objects, features and advantages of the present invention.

Hereinafter, exemplary embodiments of a scan converter for video signals according to the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram schematically illustrating an embodiment of a scan converter of a video signal according to the present invention, and FIG. 2 is a block diagram illustrating the scan converter of the video signal of FIG. 1 in more detail.

In the scan converter of a video signal according to the present embodiment, as shown in FIG. 1, the first input terminal IN2 is connected to a universal serial bus (USB) port provided in an external computer and is input from the 5V. Down the DC voltage to 3.3V and supply the operating voltage to each system of the scan coverter, the external smooth video signal (S-VHS), the composite video signal (CVBS), the luminance signal and the color signal. The video / audio input unit 100 receives the analog video signal VS and the audio signal AS, such as the video signals R, G, and B, and the operating voltage supplied from the power supply unit 600. The analog video signal VS is input from the video / audio input unit 100 as a first digital video signal in synchronization with a timing clock and corrected, and the color signal and the luminance signal are output by separating the corrected first digital video signal. The timing converter, the system clock CLK1, and the output pixel clock CLK2 are inputted by receiving the signal conversion separator 200 and the vertical and horizontal synchronization signals of the first digital video signal corrected by the signal conversion separator 200. Each of the clock generator 700 generates the timing clock to the signal conversion separator 200 and the color signal and the luminance signal input from the signal conversion separator 200 to the timing clock of the clock generator 700. The signal reinforcement unit 300 for synchronizing and outputting the signal reinforcement to display more clearly, and the data damaged from the color signal and the luminance signal of the first digital video signal inputted from the signal reinforcement unit 300 according to the output pixel clock CLK2. The correction is performed by converting the first and second analog video signals of high quality together with the second digital video signal of the computer inputted in the progressive scan mode from the input terminal IN1 and outputting them through the output terminals OUT1 and OUT2. A multi-data output unit 400 for displaying on different image output devices, a second digital video signal of the computer inputted from an input terminal IN1, and a first digital video signal corrected by the multi-data output unit 400; The system controller 500 controls the multiple data output unit 400 to be input and output as a first analog video signal or a second analog video signal in sequential scan mode.

As shown in FIG. 2, the signal conversion separation unit 200 includes an analog video signal VS input from the video / audio input unit 100, a composite video signal CVBS, a super video signal S-VHS, An input selection / clamping unit 210 for automatically detecting whether an R, G, B (Y, Pb, Pr) signal or an NTSC / PAL method is clamped at a corresponding level and size, and the clamped analog video signal Automatic gain control and analog / digital having an automatic gain control circuit for converting the gain-controlled analog video signal to the first digital video signal according to the timing clock of the clock generator 700 to remove unnecessary noise mixed in the input. A converter 220, a gamma correction unit 230 that receives the first digital video signal and corrects a gamma characteristic generated by nonlinearity, and a small signal adjacent to the gamma corrected first digital video signal. A color signal separation unit 250 for deriving a correlation between scan lines to separate a color signal, and a brightness signal separation unit for deriving a mutual relationship between adjacent scan lines from the gamma corrected first digital video signal to separate luminance signals 260 and gain / feedback feedback to the input selection / clamping unit 210 and the analog / digital conversion unit 220 by adjusting the gain and the residual deviation of the first digital video signal input from the gamma correction unit 230. The offset adjuster 240 is configured.

In addition, the signal reinforcement unit 300 includes a color demodulation control unit 310 for adjusting the saturation and color of the color signal input from the color signal separation unit 250 in synchronization with the timing clock of the timing synchronization control unit 710, and color demodulation. The color correction unit 320 sharply reinforces the color signal input from the controller 310 and removes noise to output the color signal, and the brightness and the brightness of the black and white signal input from the luminance signal separator 260 are more clearly adjusted and output. The luminance correction unit 330 and the data ratio converter 340 convert the ratio of the luminance signal whose brightness is adjusted from the luminance correction unit 330 at regular intervals and output the converted ratio.

In addition, the clock generator 700 adjusts the timing clock according to the vertical synchronization and the horizontal synchronization of the first digital video signal input from the gamma correction unit 230, thereby adjusting the analog / digital converter 220 and the color demodulation controller ( A clock synthesizing unit 720 for synthesizing the timing synchronization control unit 710 and the timing clock input from the timing synchronization adjusting unit 710 to generate a system clock CLK1 and an output pixel clock CLK2. It consists of.

In addition, the system controller 500 operates by the voltage supplied from the power supply unit 600 to control the overall operation of the scan converter, such as controlling the screen correction and sequential scanning output, and the microprocessor ( The switching unit 520 selects and outputs a first digital video signal input from the multi-data output unit 400 and a second digital video signal of a computer input from the input terminal IN1 under the control of 510. .

In addition, the multi-data output unit 400 receives the color signal input from the color compensator 320 of the signal reinforcement unit 300 and the luminance data formatted corresponding to the luminance signal of the data ratio converter 340. The on-screen display unit 410 for synthesizing and outputting the sequential scanning digital video data of a predetermined bit formatted according to a predetermined data format using the synthesized color signal, the caption data and the luminance signal of the data ratio converter 340. A data output format unit 420 for synchronizing to the output pixel clock CLK2 and outputting the first digital video signal to the switching unit 520 and the data output format unit 420 under the control of the microprocessor 510. A first digital / analog converter 430 for converting the first digital video signal of the sequential scan mode inputted from the digital signal into the first analog video signal and outputting the same to the output terminal OUT1; The second digital / analog converter 440 converts the first digital video signal or the second digital video signal of the sequential scan mode selected by the unit 520 into the second analog video signal and outputs the output to the output terminal OUT2. It is composed.

The scan converter of the video signal according to the present invention thus made will be described in more detail with reference to FIGS. 1 and 2.

First, when a 5V DC voltage is supplied through a universal serial bus (USB) port of an externally provided computer and an input terminal (IN2) connected thereto, the power supply unit 600 drops the input voltage to 3.3V. To operate the system.

In this state, the super video signal (S-VHS) such as a DVD or a video camera, or the composite video signal (CVBS) such as a TV or a VCR, or an X-BOX or PS-2 is connected through the video / audio input unit 100 from the outside. When the analog video signal VS such as R, G, B signals, etc., which are separated into a luminance video signal and a color signal, are input, the input selection / clamping unit 210 of the signal conversion separation unit 200 is input. Is automatically detected whether the input analog video signal VS is a composite video signal CVBS, a super video signal, R, G, B (Y, Pb, Pr) or NTSC / PAL. It is clamped to a size and input to an analog / digital converter 220 having an automatic gain control circuit.

The analog-to-digital converter 220 controls the gain of the analog video signal, which is clamped and input, and according to the timing clock input from the timing synchronization controller 710 of the clock generator 700 to be described later. Converts to a digital video signal to remove unwanted noise mixed into the input. The gamma correction unit 230 corrects the gamma characteristic of the first digital video signal input by removing noise, thereby adjusting the gain / offset adjusting unit 250, the color signal separating unit 250, the luminance signal separating unit 260, and the timing. It is provided to the synchronization controller 710, respectively. In this case, the gamma characteristic is a phenomenon caused by the nonlinearity of the phosphor that is used in an image output apparatus such as a television, a computer monitor, etc., and refers to a numerical expression of the nonlinearity that occurs during the reproduction of the contrast. The characteristic must be compensated for the gamma before input to the image output device in order to obtain the best resolution. In order to get the best image quality, the gamma correction function that distinguishes 256 × 10 color tables by software is adopted.

Subsequently, the gain / offset adjusting unit 240 adjusts the gain and the residual deviation of the first digital video signal input by being gamma-corrected so that the input selecting / clamping unit 210 and the analog / digital converting unit 220 can adjust the gain. The level and magnitude of the analog video signal are clamped appropriately and feedback is adjusted to appropriately adjust the gain of the first digital video signal.

The color signal separator 250 and the luminance signal separator 260 described above have an adaptive comb filter. Accordingly, the color signal separation unit 250 separates only the chromaticity component from which the luminance component is removed from the first digital video signal having the gamma correction corrected by the gamma correction unit 230, and outputs it as a color signal. Only the luminance component from which the chromaticity component is removed is separated from the first digital video signal whose gamma characteristic is corrected, and output as a luminance signal.

In addition, the timing synchronization controller 710 of the clock generator 700 receives the vertical synchronization signal and the horizontal synchronization signal of the first digital video signal whose gamma characteristic is corrected by the operation voltage supplied from the power supply unit 600. The clock is adjusted and the timing clock is provided to the analog / digital converter 220 and the color demodulation controller 310 to be described later. The clock synthesizer 720 receives the timing clock to generate a system clock CLK1 and an output pixel clock CLK2.

Meanwhile, the color signal and the luminance signal separated by the signal conversion separation unit 200 are corrected so that the color, saturation, and brightness are more clearly reinforced by the signal reinforcement unit 300 to be displayed on the image output device. ) Is adjusted to the saturation and color set by the user with respect to the color signal of the first digital video signal input from the color signal separation unit 250, and the adjusted color signal is again adjusted to the color correction unit 320. After the signal is more sharply enhanced and noise is removed, the on-screen display unit 410 of the multiple data output unit 400 is provided.

The brightness compensator 330 of the signal enhancer 300 properly adjusts the brightness and the black and white signal of the first digital video signal input from the brightness signal separator 260, that is, the brightness and contrast ratio set by the user. To the data ratio converter 340 by reinforcing more clearly, and the data ratio converter 340 converts the ratio of the input luminance signal at regular intervals, thereby converting the data output format unit of the multiple data output unit 400 ( 420.

The multi-data output unit 400 synchronizes data damaged from the color signal and the luminance signal of the first digital video signal input from the signal reinforcement unit 300 with the output pixel clock CLK2 input from the timing synchronization controller 710. The first digital video signal and the second digital video signal of the computer inputted in the progressive scan mode from the system controller 500 are converted into high quality first and second analog video signals and output. In other words, the on-screen display unit 410 of the multi-data output unit 400 receives the luminance data formatted in correspondence with the luminance signal and the color signal of the color compensator 320 from the data output format unit 420 to be described later. The caption data is synthesized so that the caption is displayed on the screen and input to the data output format unit 420.

In the data output format unit 420, 8-bit error correction data is mixed with the color signal input from the on-screen display unit 410 and the luminance signal input from the RGB signal or the data ratio converter 340 to correct corrupted data. Then, the corrected data are sequentially scanned first digital video signal of 24 bits or 18 bits or 16 bits or 15 bits corresponding to the CCIR601 data format according to the output pixel clock CLK2 provided from the clock synthesizing unit 720. The first digital / analog converter 430 and the switching unit 520 of the system controller 500 are provided.

On the other hand, the switching unit 520 of the above-described system control unit 500 of the computer that is input in the sequential scan mode from the first digital video signal and the input terminal IN1 input in the sequential scan mode from the data output format unit 420 The second digital video signal is selected under the control of the microprocessor 510 and provided to the second digital / analog converter 440 of the multidata output unit 400. The first digital-to-analog converter 430 is a 10-bit three-channel converter that sequentially scans the first digital video signal input from the data output format unit 420 under the control of the microprocessor 510 with the highest resolution. The first analog video signal (RGB, YPbPr, super video signal, composite video signal) of the mode is converted into a serial output through the output terminal (OUT1), and the second digital / analog converter 440 ) Converts the second digital video signal or the first digital video signal input from the switching unit 520 into a second analog video signal and outputs the same to the image output apparatus through the output terminal OUT2 in parallel. Output terminal with different specification such as projection TV, video camera, color cathode ray tube, thin film transistor liquid crystal monitor, plasma display panel, etc. By connecting to (OUT1) (OUT2), you can watch in the highest resolution.

In addition, the video and audio input unit 100 and the switching unit 520 receives the video signal (YUV) of the video game machine and the second digital video signal of the computer, respectively, and then process the first and second digital / analog converters ( By outputting and displaying each video output device through 430 and 440, computer work and video games can be operated simultaneously, and computer work can be performed by simple one-touch operation immediately after using a video game machine. In the drawing, reference numeral AS denotes an audio signal, which is processed as a stereo signal by a separate audio processor (not shown) provided in a scan converter of a video signal and output to a speaker.

On the other hand, as a comparative example, unlike the prior art, that is, only a composite video signal (TV) or a super video signal (projection) is output to one scan converter and cannot be displayed on an image output device, the present invention provides an RGB signal. It can output various video signals with the highest resolution for various input analog video signals such as composite video signal, super video signal, etc., and display digital video signal input from computer to video output device according to user's intention. It can be seen that.

As a result, according to the present invention, the input analog video signal of various modes is processed and output as a high definition video signal having the highest resolution, thereby providing a video camera, a color cathode ray tube, a TFT-LCD, a PDP and a television or a projection TV. Not only is it possible to use all video output devices having different specifications, such as a video game machine, but also has the advantage of being able to operate a computer or operate simultaneously with a simple one-touch operation after using a video game machine.

In addition, although specific embodiments of the present invention have been described and illustrated above, it is obvious that the present invention may be variously modified and implemented by those skilled in the art.

Such modified embodiments should not be individually understood from the technical spirit or the prospect of the present invention, and such modified embodiments should fall within the appended claims of the present invention.

According to the scan converter of the video signal of the present invention, which is clear from the above description, it is not only convenient to use the power supply without an adapter, but also the input analog video signal is processed into a DVD-quality high-definition video signal, thereby providing television, projection TV, video camera, and color. All video output devices with different specifications such as cathode ray tube, TFT-LCD, PDP, etc. can be used to view the resolution of the best video quality. Not only can it feel lively, but it is also possible to create a computer with simple one-touch operation immediately after using a video game machine.

Claims (8)

A scan converter having a video decoder connected to an external video output device to obtain an output video signal different from an input video signal: (1) power supply means for selectively connecting to a universal serial bus (USB) port of a computer to supply operating power to each system; (2) Receiving and correcting an external analog video signal from a video / audio input unit as a first digital video signal in synchronization with a timing clock by an operating voltage obtained by the power supply means, and separating the corrected first digital video signal. Signal conversion separating means for outputting a color signal and a luminance signal; (3) clock generation means for receiving the corrected vertical and horizontal synchronization signals of the first digital video signal and generating a timing clock, a system clock, and an output pixel clock, respectively, and providing the timing clock to the signal conversion separation means; (4) signal reinforcing means for reinforcing the color signal and the luminance signal of said signal conversion separating means more sharply corresponding to the timing clock of said clock generating means; (5) The damaged data from the color signal and the luminance signal of the first digital video signal inputted from the signal reinforcing means is corrected according to the output pixel clock and output as a first digital video signal having a predetermined bit, and the first digital video signal and the Multiple data output means for outputting a second digital video signal input from a computer in progressive scanning mode as first and second analog video signals having high quality; And (6) controlling the multiple data output means to receive the second digital video signal of the computer and the first digital video signal corrected by the multiple data output means and output the first analog video signal or the second analog video signal; And a system control means for scanning the video signal. The method according to claim 1, The signal conversion separating means, Input selection / clamping means for automatically detecting a mode of an analog video signal inputted from the video / audio input unit and clamping at a level and magnitude corresponding thereto; An analog / digital conversion means for automatically gain-adjusting the clamped analog video signal and converting the gain-adjusted signal into the first digital video signal according to a timing clock of the clock generation means to remove noise; Gamma correction means for correcting a gamma characteristic by receiving the converted first digital video signal; Color signal separation means and luminance signal separation means for deriving a mutual relationship between adjacent scan lines from the gamma-corrected first digital video signal to separate chromaticity and luminance components and output the chroma and luminance components as the color and luminance signals, respectively; And And gain / offset adjusting means for adjusting the gain and residual deviation of the gamma corrected first digital video signal and inputting the input / clamping means and the analog / digital converting means. The method according to claim 2, And the input analog video signal is a video signal separated into a luminance signal and a color signal, a composite video signal, a composite video standard signal, or a super video signal. The method according to claim 1, wherein the signal reinforcing means, Color demodulation adjusting means for adjusting the saturation and color of the color signal obtained by the color signal separating means in synchronization with the timing clock of the clock generating means; Color correction means for sharply reinforcing the color signal obtained by the color demodulation adjusting means and removing noise; Brightness correction means for more clearly controlling the brightness inputted from the brightness signal separation means and the brightness of the monochrome signal; And And a data ratio converting means for converting the ratio of the luminance signal of which the brightness is adjusted at a predetermined interval and outputting the converted ratio. The method according to claim 1, wherein the system control means, A microprocessor that controls the overall operation of the scan converter of the video signal, such as controlling screen correction and sequential scan output; And And switching means for selecting and outputting the first digital video signal and the second digital video signal under the control of the microprocessor. The method of claim 1, wherein the multiple data output means, On-screen display means for receiving the color signal with enhanced hue and saturation from the color correction means and the luminance data formatted according to the luminance signal of the data ratio converting means and combining the subtitle data with the subtitle data; Switching the color signal inputted from the on-screen display means, the luminance signal inputted from the data ratio converting means, and data formatted according to a predetermined data format into a first digital video signal having a predetermined bit corresponding to the timing clock. Data output formatting means provided to the means; First digital / analog conversion means for converting the first digital video signal input from the data output format means into a first analog video signal in sequential scan mode under the control of the microprocessor; And And second digital / analog converting means for converting and outputting the first digital video signal and the second digital video signal selected by the switching means to the second analog video signal. The method according to claim 1 or 6, And the first digital video signal of the predetermined bit is a 24-bit, 18-bit, 16-bit or 15-bit digital video signal. The method according to claim 1 or 6, And the first analog video signal is an RGB signal, a YPbPr signal, a composite video signal, or a super video signal in sequential scan mode.