KR20050012960A - Apparatus and method for processing subtitles - Google Patents

Abstract

PURPOSE: A caption processing apparatus and a method thereof are provided to enlarge an image signal without distorting the quality of image and to display the enlarged image signal to a screen when receiving a letter box signal including a caption signal. CONSTITUTION: An image signal processing member(130) detects the first signal included to an image region of a letter box signal when an input image signal is a letter box signal, performs a scaling of the first signal with a predetermined scaling rate and then outputs a real image signal. A caption signal processing member(140) detects the second signal included to a black region of the letter box signal, extracts a signal having a luminance level more than a reference luminance level among the second signal and sets the extracted signal as a final caption signal. A mixing member(150) mixes the real image signal with the final caption signal and produces a mixed signal. A control member(195) controls the image signal processing member, caption signal processing member and mixing member.

Description

Apparatus and method for processing subtitles}

The present invention relates to a caption processing apparatus and method, and more particularly, to a caption processing apparatus and method capable of displaying an image and a caption without distortion of the image when receiving a letter box signal containing a caption signal. It is about.

Recently, with the development of image capturing technology and editing technology, a wide screen image (hereinafter referred to as a 'wide image') such as a 16: 9 aspect ratio has been provided. Devices having a wide aspect ratio have been studied. However, since most display devices in use have a 4: 3 aspect ratio, various methods for reproducing a wide image on a display device having a general 4: 3 aspect ratio have been proposed, and one of them is a broadcast signal. This is a method of transmitting in a box format.

In order to display a broadcast signal other than 4: 3 aspect ratio on a 4: 3 aspect display device, the letterbox format is used to reduce the number of original video signals to be displayed on the screen and to black-process the upper and lower regions of the remaining screen. Format. As a result, the display device having an aspect ratio of 4: 3 provides a wide image without distortion of the screen as a viewable signal.

Meanwhile, when displaying an image transmitted in a letterbox format on a wide display device such as 16: 9, the wide display device extracts and extracts only an image signal of a transmitted letterbox format signal so that black areas above and below the screen are not displayed. Zoom in and display full screen.

However, when the received letterbox signal includes a caption signal, a viewer who views an image on the wide display device may not be able to view the caption broadcast. This is because, when the broadcast signal is transmitted in the letterbox format, most of the caption signals are located in the black region of the screen, whereas the viewer enlarges and displays only the video signal as described above so that the black region is not displayed.

Accordingly, in order to display closed captions, a conventional wide display apparatus has proposed a method of vertically reducing the size of an image in a vertical direction or shifting the image in up, down, left, and right directions. However, when the size of the image is reduced, distortion such as distortion occurs in the image displayed on the conventional wide display device, and when moving the image so that the subtitles are visible, a part of the image is not displayed on the display device as much as it is moved. This happens.

An object of the present invention is to provide a caption processing apparatus and method capable of displaying an image and a caption without distortion of the image when receiving a letterbox signal including the caption signal.

1 is a block diagram schematically showing a caption processing apparatus according to a preferred embodiment of the present invention;

FIG. 2 is a diagram illustrating an example in which regions of a letterbox signal determined by the image signal processor and the caption signal processor of FIG. 1 are displayed on a display device; FIG.

FIG. 3 is a diagram illustrating an example in which a final letter box signal generated by the synthesizer of FIG. 1 is displayed on a display device.

FIG. 4 is a flowchart schematically illustrating a caption processing method by the caption processing apparatus shown in FIG. 1.

Description of the main parts of the drawing

100: caption processing device 120: first storage unit

130: image signal processing unit 132: image determination unit

134: image processing unit 136: scaler

140: caption signal processing unit 142: caption determination unit

144: candidate subtitle detection unit 146: the final subtitle detection unit

148: subtitle storage unit 150: synthesis unit

In order to solve the above technical problem, the frequent film processing apparatus according to the present invention detects a first signal included in an image region of the letterbox signal when the input image signal is a letterbox signal, and detects the first signal. A video signal processor for outputting an actual video signal by scaling one signal at a set scaling ratio, and detecting a second signal included in a black region of the letter box signal, wherein the luminance level is greater than a predetermined reference luminance level among the second signals. A caption signal processing unit for extracting a signal having a signal and setting it as a final subtitle signal; It includes a control unit for controlling the wealth.

In more detail, the image signal processor determines whether the input image signal is the letterbox signal, and if the result corresponds to the letterbox signal, an image start address at which scanning of the first signal is started; An image determination unit for calculating an image termination address at which the scanning of the first signal is terminated, a signal included in the image region located between the image start address and the end address in the letter box signal, and detecting the scaling ratio And a scaler configured to scale the detected image signal according to the scaling ratio.

The image determining unit determines the input calculation signal as the letterbox signal when the average luminance value of the signal included between the initial scan line of the input video signal and the predetermined reference scan line is smaller than a predetermined threshold value.

Preferably, the caption signal processor determines that the second signal includes the final subtitle signal when the signal having the luminance level equal to or greater than a predetermined threshold exists in the second signal, and the luminance level equal to or greater than the threshold value. A caption determination unit for setting the reference luminance level for detecting the candidate subtitle signal by checking the first confirmed subtitle start address and the finally confirmed subtitle end address, and a signal having a luminance level equal to or greater than the reference luminance level among the letterbox signals. A candidate subtitle detection unit for detecting and setting the candidate subtitle signal to the candidate subtitle signal, a final subtitle detection unit detecting a signal located between the subtitle start address and the subtitle end address from the set candidate subtitle signal and processing the final subtitle signal; Subtitle storage unit for storing the final subtitle signal.

The caption judging unit may extract a signal having a luminance level equal to or greater than a relative intermediate luminance level among signals located between the caption start address and the caption end address, and then, the luminance level having the highest frequency among the luminance levels of the extracted signal. Is set to the reference luminance level.

The synthesizing unit processes the final subtitle signal to overlap the predetermined region where the actual video signal is displayed.

On the other hand, in order to solve the above technical problem, the caption processing method according to the present invention, when the input video signal is a letter box signal, detects the first signal included in the video area of the letter box signal, A video signal processing step of outputting an actual video signal scaled by the first signal at a set scaling ratio, detecting a second signal included in a black region of the letter box signal, and out of a predetermined reference luminance level among the second signals. A subtitle signal processing step of extracting a signal having a high luminance level and setting it as a final subtitle signal, and a synthesis step of generating a synthesized signal obtained by combining the real video signal and the final subtitle signal.

In more detail, the video signal processing may include determining whether the input video signal is the letterbox signal, and when the result corresponds to the letterbox signal, scanning of the first signal starts. Calculating an image termination address at which a scanning of a first address and a first signal is ended, detecting a signal included in the image region located between the image starting address and an ending address in the letter box signal, and the scaling ratio And setting the detected video signal according to the scaling ratio.

In the determining of whether the letter box signal is the letter box signal, if the average luminance value of the signal included between the initial scan line of the input video signal and a predetermined reference scan line is smaller than a predetermined threshold value, the input operation signal is converted into the input box signal. Judging by the letter box signal.

Preferably, the caption signal processing step includes determining that the second signal includes the final subtitle signal when a signal having a luminance level equal to or greater than a predetermined threshold exists in the second signal; Confirming a subtitle start address and a finally confirmed subtitle end address of which level is first confirmed, setting a reference luminance level for detecting a candidate subtitle signal from a luminance level of a signal located between the subtitle start and end addresses; Detecting a signal having a luminance level equal to or greater than the reference luminance level among the letterbox signals and setting the candidate subtitle signal; detecting a signal located between the start and end caption addresses from the set candidate subtitle signal and setting the final subtitle; Processing the signal, and storing the final subtitle signal.

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

FIG. 1 is a block diagram schematically illustrating a caption processing apparatus according to an exemplary embodiment of the present invention. FIG. 2 is a view illustrating a display area of each letterbox signal determined by the image signal processor and the caption signal processor of FIG. A diagram for explaining an example.

First, FIG. 1 is a view showing only blocks related to letterbox signal processing according to the present invention among display devices such as a TV, and the illustration of blocks related to other signal (for example, voice signal) processing is omitted for convenience of description. do.

Referring to FIG. 1, the caption processing apparatus 100 according to the present invention includes an analog / digital converter (hereinafter, referred to as “ADC”) 110, a first storage unit 120, and an image signal processor. 130, the caption signal processor 140, the synthesizer 150, the screen converter 160, the second storage unit 170, the digital / analog converter (hereinafter referred to as "DAC") 180, a key manipulation unit 190, and a control unit 195.

A video signal among analog broadcast signals provided from a video signal generation source source (not shown) is provided to the ADC 110. The ADC 110 converts an analog video signal into a digital video signal.

In the present invention, the video signal refers to a signal composed of at least one of an actual video signal and a subtitle signal. In addition, the letter box signal refers to a signal that is divided into an image region IMAGE and first and second black regions B1 and B2 on the screen as shown in FIG. 2. In FIG. 2, the image area IMAGE is an area where an actual image is implemented, and the first and second black areas B1 and B2 are areas where a black image or a subtitle is implemented. The first and second black areas B1 and B2 and the image area IMAGE have different sizes depending on the aspect ratio of the transmitted digital broadcast signal and the aspect ratio of the display device (not shown) for displaying an image.

The first storage unit 120 stores the digital video signal converted and output from the ADC 110 and stores the stored digital video signal in the image determination unit 132, the image processing unit 134, the subtitle determination unit 142, and the candidate subtitles. The detection unit 144 is provided.

When the digital video signal stored in the first storage unit 120 is a letter box signal, the image signal processor 130 detects the first signal included in the image area IMAGE of the letter box signal, and then detects the first signal. The actual video signal is output by scaling the signal according to the set scale ratio. To this end, the image signal processor 130 includes an image determiner 132, an image processor 134, and a scaler 136.

The image determining unit 132 determines whether the received digital video signal is a letter box signal. That is, the image determining unit 132 calculates the average luminance value of the signal included between the initial scan line of the digital video signal and the set reference scan line, and if the calculated average luminance value is smaller than the set threshold value, the provided digital video signal. Determines that is a letterbox signal. The reference scan line set here is (72 +/- alpha) in the case of the PAL system (where α is a positive number).

Also, the area from the detected initial scan line to the predetermined scan line is located in the first or second black areas B1 and B2 of the screen in the letterbox format. In the present invention, the upper part of the screen, that is, the first black area B1. It is assumed to be located at). Preferably, the first or second black regions B1 and B2 have the same size, but may be implemented differently.

In addition, when it is determined that the received signal is a letter box signal, the image determining unit 132 determines that the first signal detected after the first black region B1 is an image signal included in the letter box signal. That is, the image determining unit 132 determines that the first signal is an image signal when the image start address of the scan line where the scanning of the first signal starts is greater than a predetermined reference value. Here, the predetermined reference value is the address of the scan line where the first black region B1 ends, and differs according to the broadcast signal and the aspect ratio of the display device (not shown), and the determined image signal is determined in the image region IMAGE of the screen. Located.

The image determining unit 132 checks the address of the scanning line where the scanning of the image starts and the scanning line which ends, and provides the identified scanning line address to the image processing unit 134.

The image processor 134 detects an image signal based on an address provided from the image determining unit 132 among the letter box signals provided from the first storage unit 120. In other words, the image processor 134 detects from the letter box signal an image signal located between the image start scan line and the image end scan line.

In addition, the image processor 134 determines the scale ratio of the detected image signal.

In the present invention The scale ratio is determined by. Here, the number of standard scan lines is the number of effective scan lines of a broadcast signal initially transmitted from an image signal generation source source (not shown), for example, 576 scan lines in the PAL scheme and 480 scan lines in the NTSC scheme. The number of actual image scan lines is the number of scan lines in the image area IMAGE except for the first and second black areas B1 and B2 among the letterbox signals. This scale ratio may be stored in the form of a lookup table or separately calculated by the image processor 134.

The scaler 136 scales the image signal detected by the image processor 134 by the scale ratio determined by the image processor 134. In the present invention, the scaler 136 scales the video signal at a determined scale ratio but scales in the vertical direction.

The caption signal processing unit 140 detects the final subtitle signal among the digital video signals stored in the first storage unit 120. In detail, the caption signal processing unit 140 detects the second signal included in the second black region B2 and the address of the second signal, and then outputs a signal corresponding to the detected address to the second black region B2. The subtitle signal is extracted from a signal having a luminance level greater than a predetermined reference luminance level among the second signals included in the second signal. To this end, the caption signal processor 140 includes a caption determination unit 142, a candidate caption detection unit 144, a final caption detection unit 146, and a caption storage unit 148.

The caption determination unit 142 determines whether the caption signal is included in the digital video signal provided from the first storage unit 120. In detail, the caption determination unit 142 may determine whether the subtitle determination unit 142 has a luminance level equal to or greater than a predetermined threshold value among the second signals existing in the second black areas B1 and B2 determined by the image determination unit 132. The signal is determined to include the final subtitle signal. The caption judging unit 142 sets the scan line at which the luminance level of the predetermined threshold or more is first read as the caption start scan line, and the last read scan line as the caption end scan line.

In addition, the caption determination unit 142 sets a reference luminance level for detecting the candidate subtitle signal by checking the caption start scan line address and the caption end scan line address. In detail, the caption determination unit 142 extracts a signal having a luminance level equal to or greater than a relative intermediate luminance level among all signals existing between the caption start scan line and the caption end scan line, and then selects the signal having the highest frequency among the extracted signals. Set the luminance level to the reference luminance level. Here, the relative intermediate luminance level refers to a luminance level having 127 or 128 when the luminance level is 0 to 255, for example. The set reference luminance level is used as a reference for filtering an actual video signal, noise, and the like and detecting only the final subtitle signal.

The set reference luminance level is provided to the candidate subtitle detection unit 144, and addresses of the subtitle start and end scan lines are provided to the final subtitle detection unit 146.

The candidate candidate subtitle detection unit 144 detects the candidate subtitle signal by filtering the digital video signal provided from the first storage unit 120 using the reference luminance level determined by the subtitle determination unit 142.

In detail, the candidate subtitle detecting unit 144 detects only a signal having a bright high luminance level without considering a signal having a low luminance level darker than a reference luminance level among the digital video signals. Since the brightness of the caption signal generally has a brightness level brighter than that of the video signal, the candidate subtitle detection unit 144 determines that the signal having a brightness level brighter than the reference brightness level is determined as the candidate subtitle signal. As a result, the video signal or noise included in the second black region B2 is removed.

The final subtitle detection unit 146 detects the final subtitle signal located between the addresses of the subtitle start and end scanning lines provided from the subtitle determination unit 142 from the candidate subtitle signal detected by the candidate subtitle detection unit 144. In the detection, since the candidate subtitle signal detected by the candidate subtitle detection unit 144 also has an address corresponding to each subtitle signal, by matching or comparing the address of the detected candidate subtitle signal with the address provided from the subtitle determination unit 142. It is possible to detect the final subtitle signal. The detected final subtitle signal is stored in the subtitle storage unit 148.

Also, the final subtitle detector 146 reads the final subtitle signal stored in the subtitle storage unit 148 and provides the final subtitle signal to the synthesis unit 150.

The synthesizing unit 150 generates a final letter box signal by synthesizing the scaled image signal provided by the scaler 136 and the final subtitle signal read out from the subtitle storage unit 148. In particular, the synthesizer 150 confirms the address information of the final subtitle signal included in the final subtitle signal and synthesizes the actual video signal and the final subtitle signal. In this case, since the predetermined video signal included in the second black region B2 is erased through the filtering process by the candidate subtitle detection unit 144, only the final subtitle signal is generally included in the actual video signal having a lower luminance level than the subtitle signal. Overlap. As a result, a final letterbox signal capable of clearly displaying the final subtitle signal is generated, and the generated final letterbox signal is implemented in a display apparatus (not shown) in a form as shown in FIG. 3.

The generated final letter box signal is stored in the second storage unit 170 through the screen conversion unit 160.

The screen converting unit 160 converts the final letter box signal stored in the second storage unit 170 to correspond to a predetermined screen mode and provides the converted letter box to the DAC 190. In detail, when a predetermined screen mode is selected from a key operation unit 190 such as a remote controller (not shown), the screen conversion unit 160 converts the final letter box signal to be suitable for the format of the selected screen mode. Here, examples of the screen mode include a normal mode displaying one screen, a picture in picture (PIP) mode, a double window mode, and an interaced to progressive convert (IPC) mode, but are not limited thereto. desirable.

In addition, when receiving a PAL broadcast signal, the screen conversion unit 160 converts the broadcast signal of 50Hz to a broadcast signal of 100Hz. This is because outputting a PAL broadcast signal at 50 Hz causes a degradation in image quality such as flicker.

The DAC 180 converts the final letter box signal converted from the screen converter 160 into an analog signal.

The key operation unit 190 includes a plurality of operation keys (not shown) for outputting a signal for selecting or setting a function supported by a display apparatus (not shown) equipped with the caption processing apparatus 100 to the control unit 195. do.

In the present invention, the key operation unit 190 is provided with a mode selection unit 190a for selecting a predetermined screen mode. The predetermined screen modes include the above-described general mode, PIP mode, double window mode, IPC mode, and the like. Here, the normal mode is a mode for displaying one image on one screen, and the PIP mode is a mode in which at least one sub-screen overlaps on one main screen, and the double window mode displays two screens independently. The IPC mode is a mode for converting interlaced scanning to progressive scanning.

The controller 195 controls the overall operation of the display apparatus (not shown) equipped with the caption processing apparatus 100 according to various stored control programs and key manipulation signals corresponding to the key manipulation unit 190.

In the present invention, the control unit 195 detects the actual video signal and the final subtitle signal from the video signal determined as the letter box signal to generate a composite signal, the image signal processor 130, the caption signal processor 140 and the synthesizer Control 150.

In addition, when the selection signal for the predetermined screen mode is received by the mode selection unit 190a, the controller 195 controls the screen conversion unit 160 to convert the generated final letter box signal according to the selected screen mode. do. For example, when the normal screen mode is selected by the mode selection unit 190a, the converted letterbox signal is implemented by overlapping a caption such as 'the weather is today.' As shown in FIG.

FIG. 4 is a flowchart schematically illustrating a caption processing method by the caption processing apparatus shown in FIG. 1.

1 to 4, first, a video signal converted into a digital signal among received broadcast signals is stored in the first storage unit 120 (S405). The image determining unit 132 determines whether the digital video signal stored in the first storage unit 120 is a letter box signal (S410).

In step S410, whether or not the letter box signal is calculated is an average luminance value from the initial scan line of the digital video signal to the set reference scan line, and if the calculated average luminance value is smaller than the set threshold value, the provided digital video signal is letterbox May be determined to be a signal. In addition, since the area from the initial scan line to the set reference scan line includes the first black area B1, the image determining unit 132 detects the signal detected after the first black area B1 in step S410. It is determined that the video signal included.

If it is determined in step S410 that the received digital video signal is a letterbox signal including an image signal, the image determining unit 134 may determine an address of an image start scan line at which scanning of the image signal starts and an image end scan line at which scanning is terminated. The address is checked to detect an image signal located between the image start and end addresses from the letter box signal (S415).

After operation S415, the scaler 136 scales the detected video signal according to a set scaling ratio in operation S420.

On the other hand, the caption determination unit 142 determines whether the caption signal is included in the digital video signal (S425). That is, the subtitle determining unit 142 may include the final subtitle signal when a signal having a luminance level equal to or greater than a predetermined threshold value exists among the second signals existing between the image end scan line and the last scan line of the digital video signal. To judge.

If it is determined in step S425 that the caption signal is included, the caption determination unit 142 checks the address of the caption start scan line from which the luminance level of the predetermined threshold value or more is first read and the caption end scan line last read (S430).

When the operation S430 is performed, the caption determination unit 142 sets a reference luminance level for detecting the candidate subtitle signal by checking the caption start scan line address and the caption end scan line address (S435). In step S435, after extracting a signal having a luminance level equal to or greater than a relative intermediate luminance level among all signals existing between the subtitle start scan line and the subtitle end scan line, the luminance level of the signal having the highest frequency among the extracted signals is set as the reference luminance level. do.

After step S435, the candidate subtitle detection unit 144 filters the digital video signal provided from the first storage unit 120 using the reference luminance level set in step S435, whereby the candidate subtitle signal is detected (S440).

When the operation S440 is performed, the final subtitle detection unit 146 detects a signal located between the addresses of the subtitle start and end scan lines provided from the subtitle determination unit 142 from the candidate subtitle signal detected by the candidate subtitle detection unit 144 ( S445). The signal detected in step S445 is the final subtitle signal.

When the final subtitle signal is detected in step S445, the synthesis unit 150 generates the final letter box signal by combining the scaled final image signal and the final subtitle signal (S450). The screen converting unit 160 converts the final letter box signal, which is a composite signal, corresponding to the screen mode selected by the mode selection unit 190a (S455).

On the other hand, if it is determined in step S410 that the letter box signal is not, under the control of the controller 195, the synthesis unit 150 is a digital video signal stored in the first storage unit 120 by the mode selection unit 190a. The conversion corresponds to the selected screen mode (S460).

In addition, if it is determined in step S425 that the subtitle signal is not included, under the control of the controller 195, the synthesis unit 150 selects the final video signal scaled by a predetermined ratio by the mode selection unit 190a. The conversion corresponds to the mode (S465).

The caption processing apparatus 100 and the method described above have been described in consideration of a case in which a letter box signal transmitted at a 4: 3 aspect ratio is displayed on a display device (not shown) having a wide aspect ratio such as 16: 9. The ratio is not limited to this.

Although the present invention has been described in detail through the representative embodiments, those skilled in the art to which the present invention pertains can make various modifications without departing from the scope of the present invention with respect to the embodiments described above. Will understand. Therefore, the scope of the present invention should not be limited to the described embodiments, but should be defined by the claims below and equivalents thereof.

As described above, according to the caption processing apparatus and method according to the present invention, when receiving a letterbox signal including a caption signal, it is possible to enlarge the video signal and display it on the screen without distortion of image quality. In particular, when the received letterbox signal includes the caption signal, the caption signal can be displayed by overlapping the caption signal at a predetermined position of the enlarged video signal.

Claims (12)

A video signal processor for detecting a first signal included in an image area of the letterbox signal, outputting an actual video signal by scaling the detected first signal at a set scaling ratio; A caption signal processor configured to detect a second signal included in the black region of the letterbox signal, extract a signal having a luminance level greater than a predetermined reference luminance level from the second signal, and set the final subtitle signal; A synthesizer configured to generate a synthesized signal obtained by combining the real video signal and the final subtitle signal; And And a controller for controlling the image signal processor, the caption signal processor, and the synthesizer. The method of claim 1, The video signal processor, It is determined whether the input image signal is the letter box signal. If the result corresponds to the letter box signal, the image start address at which the scanning of the first signal is started and the image ending at which the scanning of the first signal is terminated are determined. An image determining unit calculating an address; An image processor configured to detect a signal included in the image area positioned between the image start address and the end address in the letter box signal and to set the scaling ratio; And And a scaler for scaling the detected video signal according to the scaling ratio. The method of claim 2, The image determining unit determines that the input box signal is the letter box signal when an average luminance value of a signal included between the initial scan line of the input video signal and a predetermined reference scan line is smaller than a predetermined threshold value. Subtitle processing device. The method of claim 1, The caption signal processing unit, If a signal having a luminance level equal to or greater than a predetermined threshold exists in the second signal, it is determined that the second signal includes the final subtitle signal, and the subtitle start address and final confirmation in which the luminance level equal to or greater than the threshold is first confirmed are present. A caption judging unit which checks the closed caption end address and sets the reference luminance level for detecting a candidate subtitle signal; A candidate subtitle detection unit configured to detect a signal having a luminance level equal to or greater than the reference luminance level among the letterbox signals and set the candidate subtitle signal; A final subtitle detection unit which detects a signal located between the subtitle start address and the subtitle end address from the set candidate subtitle signal and processes the final subtitle signal; And And a caption storage unit for storing the final subtitle signal. The method of claim 4, wherein The subtitle judging unit extracts a signal having a luminance level equal to or greater than a relative intermediate luminance level among the signals positioned between the subtitle start address and the subtitle end address, and then selects the luminance level having the highest frequency among the luminance levels of the extracted signal. A caption processing apparatus characterized by setting a reference luminance level. The method of claim 1, And the synthesizing unit processes the final subtitle signal to overlap the predetermined region where the actual video signal is displayed. A video signal processing step of detecting a first signal included in an image area of the letterbox signal and outputting an actual video signal scaled by the set scaling ratio if the input video signal is a letterbox signal; ; A caption signal processing step of detecting a second signal included in a black region of the letterbox signal, extracting a signal having a luminance level greater than a predetermined reference luminance level from the second signal, and setting the final subtitle signal; And a synthesizing step of synthesizing the actual video signal with the final subtitle signal. The method of claim 6, The video signal processing step, Determining whether the input image signal is the letterbox signal; Calculating an image start address at which scanning of the first signal starts and an image ending address at which scanning of the first signal ends when the letterbox signal corresponds to the letterbox signal; Detecting a signal included in the image region located between the image start address and the end address in the letterbox signal and setting the scaling ratio; And And scaling the detected video signal according to the scaling ratio. The method of claim 8, In the determining of whether the letter box signal is the letter box signal, if the average luminance value of the signal included between the initial scan line of the input image signal and a predetermined reference scan line is smaller than a predetermined threshold value, the input operation signal is converted into the letter. Caption processing method characterized in that determined by the box signal. The method of claim 7, wherein The caption signal processing step, Determining that the second signal includes the final subtitle signal when a signal having a luminance level equal to or greater than a predetermined threshold exists in the second signal; Confirming a caption start address at which the luminance level equal to or greater than the threshold is first confirmed and a finally confirmed caption end address; Setting a reference luminance level for detecting a candidate subtitle signal from a luminance level of a signal positioned between the subtitle start and end addresses; Detecting a signal having a luminance level equal to or greater than the reference luminance level among the letterbox signals and setting the candidate subtitle signal; Detecting a signal located between the subtitle start and end addresses from the set candidate subtitle signal and processing the final subtitle signal; And And storing the final subtitle signal. The method of claim 10, The reference luminance level setting step extracts a signal having a luminance level equal to or greater than a relative intermediate luminance level among the signals located between the subtitle start and end addresses, and then refers to the luminance level having the highest frequency among the luminance levels of the extracted signal. A subtitle processing method characterized by setting to a luminance level. The method of claim 7, wherein And the synthesizing step processes the final subtitle signal to overlap the predetermined region where the actual video signal is displayed.