KR100194226B1 - Viewer selectable multi-screen and caption display circuit - Google Patents

Abstract

The disclosed multi-screen and caption display circuit divides the screen according to the viewer's choice in the television receiver, receives the character code and the control code transmitted by different broadcasting signals from the broadcasting station, and displays them on the left and right divided screens. At the same time, the additional information of the multi-channel is selectively displayed.

The present invention includes a system control unit for controlling the display of the video signal, the subtitles and additional information in accordance with the command input unit and the output signal according to the viewer's operation; First and second tuners configured to receive and demodulate a television broadcast signal of a selected channel among the high frequency signals received by the antenna and to output a video signal; First and second image signal processing units which output an RGB signal and output a signal of a vertical blanking period after luminance and color processing the image signals output by the first and second tuner units; First and second decoding units for detecting and outputting the subtitles and additional information from the signals of the vertical blanking period output by the first and second image signal processing units, and outputting a control signal; First and second mixing units for mixing the subtitle captions output from the first and second subtitle decoding units and the image signals output from the first and second image signal processing units, respectively; First and second switching units configured to select signals output from the first and second mixing units and additional information output from the first and second subtitle decoding units according to control signals; A first and a second display driver and a television signal processor for outputting a signal output from the first and second switching units to a cathode ray tube, the first and second decoding units; An analog / digital converter for converting a signal of the vertical blanking period output by the first and second image signal processing units into a digital signal; A sync separator for separating and outputting the vertical sync signal and the horizontal sync signal from the signals of the vertical blanking period output by the first and second video signal processors; Under the control of the system controller, a clock signal synchronized with the color burst signal is generated, and a caption signal is generated according to the output signal of the analog / digital converter, and output to the first and second mixing units, and additional information is first and second. A caption control unit outputting to the switching unit and generating first and second control signals; Font ROMs for storing and outputting fonts such as characters such as Korean, English, Chinese and Japanese, and special characters in advance; And first and second RAMs for alternately storing and outputting fonts read from the font ROM under the control of the caption controller.

Description

Viewer selectable multi-screen and caption display circuit

The present invention relates to a viewer-selectable multi-screen and caption display circuit.

More specifically, a character code and a control code are transmitted to different television broadcast signals by a broadcasting station, the screen is divided into two according to a viewer's choice by a television receiver, and the character code transmitted by different broadcasting signals by the broadcasting station is transmitted. And a viewer-selectable multi-screen and caption display circuit for receiving a control code with two tuners and displaying different images and dialogues on two divided left and right screens, and selectively displaying additional information of multi-channels.

In the television broadcasting method, the caption broadcasting method is not selected by the viewer, and the caption signal such as urgent news or notifications is superimposed on the active section of the television broadcast signal, that is, the video signal section, according to the broadcaster's selection. The open caption method to display on the screen, the content of the screen and the predetermined additional information are displayed on the non-active section of the television broadcast signal, that is, the character code and control code in the horizontal blocking section. Closed caption system that transmits as a caption signal, receives a television broadcast signal loaded with the caption signal from a television receiver, and displays the caption signal on the screen of the television receiver according to the viewer's selection for viewing by the viewer. There is this.

Among closed captioning methods, closed captioning closed captioning was developed for the hearing impaired without the sign language, and has been implemented since 1978 in the United States. .

US Pat. No. 5,294,982, published in March 1994, discloses a closed caption method of Roman and syllable characters, and specifically describes the closed caption method of Korean.

In US Pat. No. 5,294,982, in order to broadcast Korean in a closed caption method, each Hangul character is divided into respective phonemes of the initial, neutral, and final characters, and an ASCII code corresponding to each phoneme is transmitted. After decoding the mapping of the initial, neutral, and final characters, the Hangul characters of the initial, neutral, and final maps are displayed.

This conventional Hangul close caption method should use at least 2 to 3 bytes to represent a single Hangul character.

That is, 2 bytes are used to display only Korean and neutral, and 3 characters are used to display Korean, which has no initiality and neutrality.

Therefore, the decoding process was very complicated because the transmission speed and display speed of the subtitle signal were slow, and the position of one Korean character was found after converting the two to three bytes of data received during the decoding process into three to four bytes. .

The complexity of the decoding process is to increase the production cost of the decoder, which increases the price of the decoder in the television receiver used by many viewers as compared to the encoder required only by the broadcasting station, thereby putting a lot of economic burden on the user.

In addition, simultaneous display of Chinese characters, Korean, and Japanese, and simultaneous display of English, Russian, and Greek were impossible, and display of special symbols was impossible.

In addition, since the control code is required to display the dialogue information in the middle of displaying the supplementary information and display the supplementary information again, there is no independence between the dialogue information and the supplementary information, and a control system for distinguishing the display mode of the dialogue information. Is very complicated in transmission efficiency of the whole system, and if the display mode control code is not received at the time when the receiver starts to operate, the metabolic information cannot be displayed until the next control code is received.

In addition, the above-described US Patent US Pat. No. 5,294,982 was developed based on the transmission environment of the US television broadcasting, that is, the geographical environment with a lot of flat land. The quality was poor, and one screen was divided into two to display different video signals, multiple characters, and additional information according to the viewer's choice.

Accordingly, an object of the present invention is to provide a viewer-selected multi-screen for selectively displaying additional information and multi-characters while simultaneously displaying different images on the left and right screens by dividing one screen into two according to the viewer's selection; It is to provide a caption display circuit.

According to the viewer-selectable multi-screen and caption display circuit of the present invention for achieving the above object, a system control unit for controlling the display of the video signal and the subtitles and additional information according to the output signal of the command input unit according to the viewer's operation; First and second tuners configured to receive and demodulate a television broadcast signal of a selected channel under the control of the system controller among the high frequency signals received by the antenna and output an image signal; First and second image signal processing units which output an RGB signal and output a signal of a vertical blanking period after luminance and color processing the image signals output by the first and second tuner units; First and second decoders for detecting and outputting the subtitles and additional information from the signals of the vertical blanking period output by the first and second image signal processing units and outputting a control signal; First and second mixing units for mixing the subtitle captions output from the first and second subtitle decoding units and the image signals output from the first and second image signal processing units, respectively; First and second switching units configured to select signals output from the first and second mixing units and additional information output from the first and second subtitle decoding units according to control signals; And first and second display drivers and a television signal processor for processing signals output from the first and second switching units and outputting the signals to the cathode ray tube.

And the first and second decoding units; An analog / digital converter for converting signals of vertical blanking periods output by the first and second image signal processing units into digital signals; A sync separator for separating and outputting a vertical sync signal and a horizontal sync signal from the signals of the vertical blanking period output by the first and second video signal processors; Under the control of the system controller, a clock signal synchronized with the color burst signal is generated, a caption signal is generated according to the output signal of the analog / digital converter, and outputted to the first and second mixing units, and the additional information is displayed. A caption control unit outputting to the first and second switching units and generating first and second control signals; Font ROMs for storing and outputting fonts such as characters such as Korean, English, Chinese and Japanese, and special characters in advance; And a RAM configured to store and output a font read from the font ROM under the control of the subtitle controller, wherein the RAM includes a first RAM and a second RAM to read the font read from the font ROM. Under the control of the subtitle control unit, they are alternately stored and output.

1 is a block diagram showing the configuration of a television broadcasting system for viewer-selective closed caption broadcasting of the present invention.

2 is a view showing a viewer-selectable multi-screen and caption display circuit according to the present invention.

3 is a diagram showing the configuration of a caption signal according to the present invention;

4 is a diagram showing the configuration of a data packet of caption data according to the present invention;

FIG. 5 is a diagram showing a screen display state of an optical television receiver employing the viewer-selectable multi-screen and caption display circuit shown in FIG.

* Explanation of symbols for main parts of the drawings

100 antenna 100,115 first and second tuner parts

140,145: first and second image signal processing unit

150, 155: first and second mixing section 152, 157: first and second switching section

160,165: first and second display driver 168: television signal processing unit

170: cathode ray tube 180: system control unit

190: Command input unit 200,200A: First and second subtitle decoding units

210: analog-to-digital converter 220: synchronous separator

230: subtitle control unit 240: font ROM

245,250: first and second RAM

Hereinafter, a viewer-selectable multi-screen and caption display circuit of the present invention will be described in detail with reference to the accompanying drawings.

1 is a block diagram showing the configuration of a television broadcasting system for viewer-selective closed caption broadcasting according to the present invention.

Here, reference numeral 10 denotes a microphone for inputting an audio signal, and reference numeral 20 denotes a video camera that photographs a predetermined subject and outputs an image signal.

The audio signal input through the microphone 10 is mixed and amplified by the audio signal processor 30 and input to the television signal modulator 50. The video signal output from the video camera 20 is a video signal processor ( 40 is amplified and edited and then input to the television signal modulator 50 through the switching means 78 of the subtitle encoding section 70 described later.

The output signal of the television signal modulator 50 is transmitted to the air wirelessly through the high frequency output unit 60 and through the antenna 80.

Reference numeral 70 denotes a caption encoding unit for mixing predetermined additional information and control information with the output signal of the video signal processor 40 in a closed captioning manner.

The caption encoding unit 70 may include a text information input unit 71 for inputting additional information such as dialogue information, emergency news, and delivery items related to a television screen, and various control information for caption control according to a broadcaster's manipulation. To a control signal input unit 72 for inputting, a character code generation unit 73 for generating a data packet of a character code with respect to an output signal of the character information input unit 71, and an output signal of the control signal input unit 72; A control code generator 74 for generating a data packet of a control code, a data packet modulator 75 for modulating a data packet generated by the character code generator 73 and the control code generator 74; And a window signal generated according to the count value of the sync counter 76 which is reset according to the vertical sync signal output from the video signal generator 40 and counts a horizontal sync signal. According to the output signal of the window signal generator 77 and the window signal generator 77, the output signals of the video signal processor 40 and the data packet modulator 75 are switched to display the television signal defender ( And switching means 78 for inputting to 60.

The character information input unit 71 includes a keyboard (not shown) for inputting characters or special characters such as Korean, English, Chinese, and Japanese, and converts the input character information into a 2-byte Hangul completion code. Output to (KSC5901).

The control information input unit 72 includes a keypad (not shown) including a mode selection key, a function selection key, and the like. The control information input unit 72 converts the control information according to the input key signal of the keypad into 7-bit binary. Output to code

In the television broadcasting system for the viewer-selective caption broadcasting configured as described above, the predetermined audio signal input through the microphone 10 is mixed and amplified with another predetermined audio signal by the audio signal processing unit 30, and thus the television signal modulation unit 50 is used. Is entered.

The video signal of a predetermined subject photographed and output by the video camera 20 is amplified and edited by the video signal processor 40, and then is switched by the switching means 78 of the caption encoding unit 70. ) Is entered.

Then, the television signal modulator 50 FM-modulates the audio signal input from the audio signal processor 30, and modulates the video signal input from the video signal processor 40 by AM modulation in a residual sideband manner. A signal and an AM modulated signal are frequency-multiplexed and frequency shifted to output a high frequency signal.

As described above, the high frequency signal output from the image signal processor 40 is amplified by the high frequency output unit 60 and then transmitted to the air as a television broadcast signal through the antenna 80.

When the broadcaster manipulates a keyboard provided in the character information input unit 71 of the subtitle encoding unit 70, and inputs character information such as predetermined characters such as Korean, English, Chinese characters, and Japanese or special characters, the character information input unit 71 ) Converts the predetermined character information into a 2-byte Hangul completion code and outputs it.

When the broadcaster operates the keypad of the control information input unit 72 to input control information such as a mode selection key and a function selector, the control information input unit 72 converts the predetermined control information into a 7-bit binary code. To print.

In this way, the two-byte Hangul completion code according to the predetermined character information output by the character information input unit 71 is inputted to the character code generator 73 and converted into a data packet. By using the Most Signification Bit (MSB) of each byte of the byte Hangul completion code as the subtitle / additional information flag, replace the MSB with '0' for the subtitle and add '1' for the additional information. After replacement, a parity bit is added to each byte to generate a data packet having a total of 18 bits of character code.

The 7-bit binary code output by the control information input unit 72 is input to the control code generator 74 and converted into a data packet of the control code. The control code generator 74 inputs the input 7-bit binary code. Is divided into upper 4 bits and lower 3 bits, and then, for the upper 4 bits, 1 bit of parity bit for the upper 4 bits, 2 bits of control code identification bit, and 1 bit of the subtitle subtitle / additional information flag are added. An upper byte is generated, and for the lower three bits, one bit of the first parity bit, one bit of the second parity bit, two bits of control code identification bit, and one bit of the subtitle subtitle / additional information flag are added. The lower byte is generated, and a parity bit is added to the generated upper byte and lower byte to generate a data packet having a total of 18 bits of control code.

Detailed description of the data packet of the character code and the data packet of the control code will be described later.

In this way, the data packet of the total 18 bits of the character code generated by the character code generator 73 and the data packet of the total 18 bits of the control code generated by the control code generator 74 are digitally modulated by the data packet modulator 75. Modulated in such a manner that it is output to the switching unit 78.

The vertical sync signal and the horizontal sync signal output from the video signal processor 40 are input to the sync counter 76. The sync counter 76 resets the horizontal sync signal according to the input vertical sync signal. A count and a scanning player are counted and output, and the window signal generator 77 generates a window signal in accordance with the count value of the horizontal sync signal output from the sync counter 76.

In this way, the switching signal generated by the window signal generator 77 is applied to the switching means 78 as a control signal to control the switching operation of the switching means 78. The switching means 78 is the image signal processor 40. Superimposing a data packet of a character code and a control code according to a caption signal outputted by the data packet modulator 75 on a predetermined specific line of an output signal of the signal; And is transmitted through the high frequency output unit 60 and the antenna 80.

2 is a view showing a viewer-selectable multi-screen and caption display circuit according to the present invention.

As shown therein, first and second tuner units 110 and 115 for receiving, demodulating and outputting a television broadcast signal of a channel selected from the high frequency signals received through the antenna 100, and the first and second ones. First and second image signal processing units 140 and 145 for outputting an RGB signal and outputting a signal of a vertical blanking period after luminance and color processing of an image signal output by the tuner units 110 and 115. And detecting and outputting a caption signal and additional information from the signals of the vertical blanking period output by the first and second video signal processing units 140 and 145, and generating a control signal to display the additional information. The first and second subtitle decoding units 200 and 200A, and the first and second subtitle decoding units 200 and 200A to the RGB signals output by the first and second image signal processing units 140 and 145. First and second mixing units 150 and 155 for mixing and outputting subtitle signals output by the first and second mixing units 150 and 155. First and second switching units 152 for selectively outputting an output signal of the first and second subtitle decoding units 200 and 200A or an output signal of 150 and 155 according to the control signal. 157 and first and second display drivers 160 and 165 for processing the output signals of the first and second switching units 152 and 157 as signals to be displayed on the cathode ray tube. A television signal processor 168 for processing the output signals of the second display drivers 160 and 165 and displaying them on the cathode ray tube 170; a command input unit 190 for inputting an operation command according to a user's operation; The system control unit 180 controls the overall operation of the television receiver according to the operation command input by the command input unit 190 and controls the first and second subtitle decoding units 200 and 200A.

The first and second subtitle decoding units 200 and 200A convert analog and digital signals of the vertical blanking period output by the first and second image signal processing units 140 and 145 into digital signals. A sync separator 220 for separating and outputting a vertical sync signal and a horizontal sync signal from the vertical blanking period signal output by the converter 210 and the first and second video signal processing units 140 and 145, Under the control of the system controller 180, a clock signal is generated according to the output signal of the synchronous separator 220, and a caption signal is generated according to the output signal of the analog / digital converter 210. And a caption controller for outputting to the second mixing unit 150 and 155 and outputting the additional information to the first and second switching units 152 and 157 and generating first and second control signals. 230) and fonts such as Korean, English, Chinese and Japanese characters, and special characters. The first and second RAMs 245 and 250 for alternately storing and outputting the font ROM 240 for storing and outputting the font ROM 240 and the font read from the font ROM 24 under the control of the subtitle controller 230. It is composed of

Here, the configuration of the caption information used in the television system for transmitting and receiving the caption broadcast will be described in detail.

In Korea, the NTSC-M system of 525 lines and 60 fields / sec is used as a television broadcast signal, and the vertical blanking period is specified from scan line 10 to scan line 20.

There is no standard set by the Ministry of Information and Communication on the use of signals during the vertical blanking period, and reference is made to ITU-R Recommendation Rec 473-2 and to the US FCC Report and Order 83-120.

The caption signal may be any one of the scan lines 10 to 20, the scan lines 21, or the scan lines 262 among the scan lines in the vertical blanking period for the transmission of the caption data. Can also be used.

However, in caption broadcasting, data transmission of the entire field is meaningless and is not considered.

The transmission bit rate of the caption data should be 447,443.125 ± 125 bps and the maximum change rate of the transmission bit rate should be within ± 196 (± 0.0125 bps).

The caption data signal is used only for transmission of the color television broadcast signal, and the transmission bit rate is set to 1/8 of the color carrier frequency fsc (357,9545 ± 10 Hz), and must be frequency synchronized with the color burst signal.

It is preferable that the color carriers have a continuous phase between the scan line and the scan line, and if the phase of the color carriers is discontinuous due to screen editing or the like, at least phase synchronization should be performed on the color burst of the main line.

In the data modulation method, the one corresponding to the logic value '1' is expressed as a sine wave of one cycle having a phase of 0 degrees and having a frequency of fsc / 8 (447.443 KHz), and the one corresponding to the logic value '0' is a phase. Is 180 degrees and uses a digital modulation scheme called Binary Phase Shift Keying (BPSK) or Phase Reversal Keying (PRK), which is represented by a period of sinusoids with a frequency of fsc / 8. The maximum range of phase jitter is ± 10 Do it.

The optimal signal waveform will be defined in the future as it may vary depending on the frequency spectral characteristics of the number of television channels. However, due to the fundamental band-limiting frequency, the BPSK waveform can be severely distorted in the area where the logic value transition occurs. Therefore, the phase-corrected waveform is passed after passing through a second Butterworth filter with a cutoff frequency of 3.5 MHz. We will use it for broadcasting.

Here, the impulse response of the Butterworth filter used is as shown in Equation 1 below.

Where f _c is 3.5 MHz.

Among the inspection items of radio stations, the inspection method and basis are defined in No. I-7 (TV broadcasting station), item 4 (text broadcasting) or item (superposition of data line and amplitude of text signal), and the waveform of subtitle signal is NRZ ( None is not a return to zero, but a pure sine wave, so it is not necessary to apply the above criteria.

However, in the region where more than 70% of the mountains are produced in Korea, the maximum sine wave is 90 ± 51RE in order to widen the receiving area.

Although the maximum amplitude of the normal data signal is defined, the overshoot may be included due to the filter passband characteristic, so that the absolute value of the overshoot is 51RE.

As shown in FIG. 3, the data line of the subtitle signal is a 6-bit bit clock synchronizing signal 302, and is composed of a word start signal 304 and an 18-bit data string 306. As shown in FIG.

The bit clock synchronizing signal 302 is a 6-period sinusoidal signal that can be used to extract the sinusoidal signal from the subtitle decoding unit to read a bit period of 18-bit data. The frequency of the bit clock synchronizing signal 302 is fsc / 4 (894.886 KHz).

The bit clock synchronizing signal 302 is separated by 9.50 µsec (34 color bursts) from the midpoint OH of the falling edge of the horizontal synchronizing signal when the phase of the color carrier of the scan line is 0 degrees. If the phase of the color carrier of the scan line is 180 degrees, it starts at a point separated by 9.64 secsec (color burst 34.5 cycles) from the midpoint OH of the falling edge of the horizontal synchronization signal.

Since the bit clock synchronizing signal 302 is in frequency synchronization with the color burst of the corresponding line, the bit clock synchronizing signal 302 may be extracted from the color burst.

The word start signal 304 is a sinusoidal signal of one cycle of fsc / 16 (223.722 KHz) and having a phase of 180 degrees, which serves to indicate the start of an 18-bit data packet.

The data string 306 is composed of 18 bits and has a bit rate of fsc / 8 (447.443 KHz) and is modulated by the BPSK method.

As shown in FIG. 4, the data packet is composed of three parts: parity (p) in word units, dialogue subtitle / additional information flag (C / T), and code value (c).

Here, D0 to D8 are abbreviated as lower words, and D9 to D17 are abbreviated as upper words.

D17 represents even parity for D0 to D16. The parity bit p of this D17 is for first detecting an error in transmission.

D7 and D16 are the metabolism subtitle / additional information flags as 0 for the metabolism subtitle and 1 for the additional information, and the values of D7 and D16 must match. In addition, the subtitle caption / additional information flag is used to maintain the priority in word units.

D0 to D6 and D9 to D15 together represent a code value. Code values are interpreted as control codes if D5, D6, D14 and D15 are all 0, otherwise they are interpreted as character codes.

In the viewer-selectable multi-screen and caption display circuit of the present invention displaying such subtitles and additional information on the screen, the first and second tuner units 110 and 115 select a high frequency signal received from the antenna 100 by the viewer. The television broadcast signal of the channel is tuned and demodulated to output a video signal.

The image signals output by the first and second tuner units 110 and 115 are input to the first and second image signal processing units 140 and 145, and then processed as luminance and color, and then the RGB signals are output. A signal of the blanking period is output.

The RGB signals output by the first and second image signal processing units 140 and 145 are input to the first and second mixing units 150 and 155, and thus the first and second subtitle decoding units 200 and 200A. And the first and second switching units 152 and 157 and the first and second display drivers 160 and 165 under the control of the first and second control signals. It is input to the television signal processing unit 168 and displayed on the screen of the cathode ray tube 170.

In addition, the signals of the vertical blanking period output by the first and second image signal processing units 140 and 145 are digitally converted by the analog / digital converter 210 of the first and second subtitle decoding units 200 and 200A. The signal is converted into a signal and input to the caption controller 230, and the vertical and horizontal sync signals are separated from the sync separator 220 and input to the caption controller 230.

In this state, when the viewer manipulates the command input unit 190 to display the multi-screen and the multi-character caption on the screen of the cathode ray tube 170, the system controller 180 inputs this command to enter the television receiver operation mode. Switch to the multi-character caption display mode of the multi screen.

When the operation mode of the television receiver is switched to the multi-character caption display mode as described above, the subtitle processing unit 230 generates a clock signal synchronized with the color burst signal, and receives the digital signal from the analog / digital converter 210. A caption data packet is extracted from the signal, and the extracted caption data packet is decoded.

Subtitle processing is controlled in response to the control code decoded the caption data packet, and the character data is read from the font ROM 24 in response to the decoded character code to be alternated with the first and second RAMs 245 and 250. Write and read out.

Character data alternately stored in the first and second RAMs 245 and 250 are converted into an RGB signal and outputted, and the decoded caption signal is output to the first and second mixing units 150 and 155. The first and second video signal processing units 140 and 145 are mixed with the video signals respectively output and then output to the first and second switching units 152 and 157, and the decoded additional information is first and second. Output to the switching unit 152,157.

In this way, the viewer operates the command input unit 190 while the output signals and the additional information of the first and second mixing units 150 and 155 are input to the first and second switching units 152 and 157. When data for displaying the subtitles is input, predetermined first and second control signals are output from the first and second subtitle decoding units 200 and 200A, so that the first and second switching units 152 ( The first and second switching units 152 and 157 select a mixed signal of the video signal and the metabolizer subtitles output from the first and second mixing units 150 and 155 and apply the selected video signal. And the mixed signal of the metabolic subtitles is output to the cathode ray tube 170 through the first and second display drivers 160 and 165 and the television signal processor 168, and is shown in FIG. 5A on the screen of the cathode ray tube 170. FIG. As described above, the subtitles are displayed on the multi-screen in the video signals received by the first and second tuner units 110 and 115.

When the viewer manipulates the command input unit 190 to input data for displaying additional information, the first and second subtitle decoding units 200 and 210 output predetermined first and second control signals. Since the first and second switching units 152 and 157 are applied to the first and second switching units 152 and 157, the first and second switching units 152 and 157 select additional information output from the first and second decoding units 200 and 200A. The first and second display drivers 160 and 165 and the television signal processing unit 168 are output to the cathode ray tube 170, and the first and second display drivers 160 and 165 are displayed on the screen of the cathode ray tube 170 as shown in FIG. 5B. The additional information received by the second tuners 110 and 115 is displayed on a multi screen.

As described in detail above, according to the viewer-selectable multi-screen and caption display circuit of the present invention, the screen of the cathode ray tube is divided into two to display different images and subtitles on the left and right screens according to the viewer's selection, or to add the multi-channel. Display information.

Claims (3)

A system controller which controls the display of the video signal, the subtitle caption, and additional information according to the output signal of the command input unit according to the viewer's operation; First and second tuners configured to receive and demodulate a television broadcast signal of a selected channel under the control of the system controller among the high frequency signals received by the antenna and output an image signal; First and second image signal processing units for outputting an RGB signal and outputting a signal of a vertical blanking period after luminance and color processing the image signals output by the first and second tuner units; First and second decoders for detecting and outputting the subtitles and additional information from the signals of the vertical blanking period output by the first and second image signal processing units and outputting a control signal; First and second mixing units for mixing the subtitle captions output from the first and second subtitle decoding units and the image signals output from the first and second image signal processing units, respectively; First and second switching units configured to select signals output from the first and second mixing units and additional information output from the first and second subtitle decoding units according to control signals; And a first and second display driver and a television signal processor for processing the signals output from the first and second switching units and outputting the signals to the cathode ray tube. 2. The apparatus of claim 1, wherein the first and second decoding units; An analog / digital converter for converting signals of vertical blanking periods output by the first and second image signal processing units into digital signals; A sync separator for separating and outputting a vertical sync signal and a horizontal sync signal from the signals of the vertical blanking period output by the first and second video signal processors; Under the control of the system controller, a clock signal synchronized with the color burst signal is generated, a caption signal is generated according to the output signal of the analog / digital converter, and is output to the first and second mixing units, and the additional information is output. A caption control unit outputting to the first and second switching units and generating first and second control signals; Font ROMs for storing and outputting fonts such as characters such as Korean, English, Chinese and Japanese, and special characters in advance; And a RAM for storing and outputting the font read out from the font ROM under the control of the subtitle control unit. The method of claim 2, wherein the RAM of the subtitle decoding unit; And first and second RAMs, and alternately storing and outputting fonts read from the font ROM under the control of the caption controller.