Abstract:
A processing device for adding a subtitle to a three-dimensional (3D) image produced by left-eye and right-eye display patterns displayed on a display is disclosed. The processing device may include a video decoder configured to receive video content data representing content left-eye and content right-eye display patterns. The processing device may also include an audio decoder configured to receive sound data indicative of an audio volume level. Additionally, the processing device may include a subtitle decoder configured to receive subtitle data indicative of a subtitle display pattern, and modify the subtitle data based on the sound data. The processing device may also include a superimposition unit configured to combine the modified subtitle data with the video content data to create combined pattern data representing combined left-eye and combined right-eye display patterns.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority of Japanese Patent Application No. 2009-297546, filed on Dec. 28, 2009, the entire content of which is hereby incorporated by reference. 
       BACKGROUND 
       [0002]    1. Technical Field 
         [0003]    The present disclosure relates to an image processing device, an image processing method, and a program, and particularly relates to an image processing device, an image processing method, and a program that enable display of a sub-image such as a 3D subtitle with increased effect. 
         [0004]    2. Description of the Related Art 
         [0005]    While contents such as motion pictures mainly use 2D images, 3D images have been attracting attention in recent years. 
         [0006]    As a reproduction device that reproduces a 3D content, there has been a device that combines and displays a main image of a 3D motion picture or the like with a 3D subtitle image. Note that, herein, a subtitle image refers to an image having a rectangular region including an entire subtitle to be displayed in one screen. 
         [0007]    Such a reproduction device combines a main image for left eye with a subtitle image for left eye so as to be displayed on a screen for left eye, and combines a main image for right eye with a subtitle image for right eye so as to be displayed on a screen for right eye. 
         [0008]    Specifically, when left-eye subtitle data, including image data of the subtitle image for left eye and a display position (Lx, Ly) of an upper left corner of the subtitle image on an x-y coordinate system on a screen, and right-eye subtitle data, including image data of the subtitle image for right eye and a display position (Rx, Ry) of an upper left corner of the subtitle image on an x-y coordinate system on a screen, are inputted, the reproduction device generates a left-eye subtitle plane which is image data of a screen in which the subtitle image for left eye is arranged in the display position (Lx, Ly) based on the left-eye subtitle data and generates a right-eye subtitle plane which is image data of a screen in which the subtitle image for right eye is arranged in the display position (Rx, Ry) based on the right-eye subtitle data, as shown in  FIG. 1 . 
         [0009]    Then, as shown in  FIG. 1 , the reproduction device superimposes the left-eye subtitle plane on a left-eye video plane which is image data of a screen of the main image for left eye to generate a left-eye plane which is image data of the screen for left eye. Also, as shown in  FIG. 1 , the reproduction device superimposes the right-eye subtitle plane on a right-eye video plane which is image data of a screen of the main image for right eye to generate a right-eye plane which is image data of the screen for right eye. 
         [0010]    On the other hand, when 2D display subtitle data including image data of a subtitle image for 2D display and a display position (x, y) of an upper left corner of the subtitle image on an x-y coordinate system on a screen is inputted, the reproduction device first generates, as the left-eye subtitle plane, image data of a screen in which the upper left corner of the subtitle image for 2D display is arranged in a position (x+offset, y) shifted from the display position (x, y) in the positive direction of x-coordinate by an offset amount “offset”, as shown in  FIG. 2 . Then, the reproduction device superimposes the left-eye subtitle plane on the left-eye video plane to generate the left-eye plane. 
         [0011]    Also, the reproduction device generates, as the right-eye subtitle plane, image data of a screen in which the upper left corner of the subtitle image is arranged in a position (x−offset, y) shifted from the display position (x, y) in the negative direction of the x-coordinate by the offset amount “offset”. Then, the reproduction device superimposes the right-eye subtitle plane on the right-eye video plane to generate the right-eye plane. 
         [0012]    Note that an image is transparent in a region where the subtitle image is not arranged in the screen corresponding to the left-eye subtitle plane and in the screen corresponding to the right-eye subtitle plane in  FIGS. 1 and 2 , and that the main image is arranged in a corresponding region in the screen corresponding to the left-eye plane and the right-eye plane. 
         [0013]    When the left-eye plane and the right-eye plane are generated in a manner described above, the screen for left eye is displayed on a display device based on the left-eye plane so as to be shown to a left eye of a user, and the screen for right eye is displayed on the display device based on the right-eye plane so as to be shown to a right eye of the user. Accordingly, the user can view a 3D main image combined with a 3D subtitle. 
         [0014]    For example, as shown in  FIG. 3A , when the subtitle image for left eye is shifted in the right direction by the offset amount “offset” and the subtitle image for right eye is shifted in the left direction by the offset amount “offset”, a focal position is shifted frontward (user side) in relation to a display device surface, causing the subtitle image to appear to pop out. 
         [0015]    On the other hand, as shown in  FIG. 3B , when the subtitle image for left eye is shifted in the left direction by the offset amount “offset” and the subtitle image for right eye is shifted in the right direction by the offset amount “offset”, the focal position is shifted backward in relation to the display device surface, causing the subtitle image to appear to recede. Note that  FIGS. 3A and 3B  illustrate a user viewing the image displayed on the display device, when seen from above. 
         [0016]    As a reproduction device that reproduces a 3D content, there has also been a device that combines and displays a 3D main image with a telop (for example, see Japanese Unexamined Patent Application Publication No. 10-327430). 
       SUMMARY 
       [0017]    With the reproduction device described above, a display state of a subtitle image such as color, transparency, and position in the depth direction, which is a direction vertical to a screen, of a subtitle has not been changed in response to the volume of or change in sound corresponding to a main image which is combined with the subtitle image. 
         [0018]    Thus, it is desirable to display a subtitle with increased effect by changing, in response to the volume of or change in sound corresponding to a main image, a display state of a subtitle image with which the main image is combined. 
         [0019]    It is desirable to display a sub-image such as a 3D subtitle with increased effect. 
         [0020]    Accordingly, there is disclosed a processing device for adding a subtitle to a three-dimensional (3D) image produced by left-eye and right-eye display patterns displayed on a display. The processing device may include a video decoder configured to receive video content data representing content left-eye and content right-eye display patterns. The processing device may also include an audio decoder configured to receive sound data indicative of an audio volume level. Additionally, the processing device may include a subtitle decoder configured to receive subtitle data indicative of a subtitle display pattern, and modify the subtitle data based on the sound data. The processing device may also include a superimposition unit configured to combine the modified subtitle data with the video content data to create combined pattern data representing combined left-eye and combined right-eye display patterns. 
         [0021]    There is also disclosed a method for adding a subtitle to a three-dimensional (3D) image produced by left-eye and right-eye display patterns displayed on a display. The method may include receiving video content data representing content left-eye and content right-eye display patterns. The method may also include receiving sound data indicative of an audio volume level. Additionally, the method may include receiving subtitle data indicative of a subtitle display pattern. The method may also include modifying the subtitle data based on the sound data. In addition, the method may include combining the modified subtitle data with the video content data to create combined pattern data representing combined left-eye and combined right-eye display patterns. 
         [0022]    Consistent with an embodiment of the present invention, a sub-image such as a 3D subtitle can be displayed with increased effect. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]      FIG. 1  illustrates a method of generating a left-eye plane and a right-eye plane; 
           [0024]      FIG. 2  illustrates another method of generating a left-eye plane and a right-eye plane; 
           [0025]      FIGS. 3A and 3B  illustrate how a 3D subtitle image is viewed; 
           [0026]      FIG. 4  is a block diagram illustrating a configuration example of an image processing device according to an embodiment of the present invention; 
           [0027]      FIG. 5  is a flowchart illustrating a subtitle conversion process by the image processing device in  FIG. 4 ; 
           [0028]      FIG. 6  is a block diagram showing a configuration example of an image processing device according to another embodiment of the present invention; 
           [0029]      FIG. 7  is a flowchart illustrating a subtitle conversion process by the image processing device in  FIG. 6 ; and 
           [0030]      FIG. 8  illustrates a configuration example of a computer according to an embodiment. 
       
    
    
     DETAILED DESCRIPTION 
     Embodiment 
     [Configuration Example of an Image Processing Device According to an Embodiment] 
       [0031]      FIG. 4  is a block diagram illustrating a configuration example of an image processing device according to an embodiment of the present invention. 
         [0032]    An image processing device  10  in  FIG. 4  includes a video decoder  11 , a subtitle decoder  12 , a superimposition unit  13 , a display unit  14 , an audio decoder  15 , and a speaker  16 . 
         [0033]    Video data of a main image for 3D display, subtitle data for 3D display, and sound data which are read from a recording medium such as a Blu-ray® Disc (BD) or received from an external device via a network or the like are inputted as 3D content data to the image processing device  10 . The image processing device  10  uses the 3D content data to perform a 3D display of the main image combined with a subtitle image and to output sound corresponding to the main image. 
         [0034]    Specifically, the video decoder  11  of the image processing device  10  decodes video content data (i.e., the inputted video data of the main image for 3D display), and supplies a resulting left-eye display pattern (i.e., a left-eye video plane) and a resulting right-eye display pattern (i.e., a right-eye video plane) to the superimposition unit  13 . 
         [0035]    The subtitle decoder  12  performs a decoding process with respect to the inputted subtitle data for 3D display (i.e., subtitle data indicative of a subtitle display pattern). Note that the subtitle data for 3D display includes subtitle data for right eye and subtitle data for left eye, and the subtitle data for each eye includes image data (for example, bitmap image data) including a pixel value of each pixel of a subtitle image for each eye, a display position of the subtitle image for each eye on a screen, and an alpha blending value representing a combination ratio of the subtitle image for each eye to the main image. 
         [0036]    Note that the subtitle data for each eye may include a character string describing a character code of a subtitle for each eye and color information such as a palette number, instead of the image data of the subtitle image for each eye. In this case, the subtitle decoder  12  also performs a process of generating image data of the subtitle image for each eye from the character string for each eye and the color information. 
         [0037]    Based on sound information which is information supplied from the audio decoder  15  and representing the audio volume level (i.e., the volume of sound) corresponding to the inputted sound data, the subtitle decoder  12  changes the subtitle data for 3D display obtained as a result of the decoding process. Then, based on the resulting subtitle data for 3D display, the subtitle decoder  12  generates a left-eye subtitle display pattern (i.e., a left-eye subtitle plane) and a right-eye subtitle display pattern (i.e., a right-eye subtitle plane) and supplies the planes to the superimposition unit  13 . Further, the subtitle decoder  12  supplies to the superimposition unit  13  the alpha blending value for left eye included in the subtitle data for left eye and the alpha blending value for right eye included in the subtitle data for right eye. 
         [0038]    The superimposition unit  13  superimposes the left-eye subtitle plane supplied from the subtitle decoder  12  on the left-eye video plane supplied from the video decoder  11  with the alpha blending value for left eye to generate a combined left-eye display pattern (i.e., a left-eye plane). Also, the superimposition unit  13  superimposes the right-eye subtitle plane supplied from the subtitle decoder  12  on the right-eye video plane supplied from the video decoder  11  with the alpha blending value for right eye to generate a combined right-eye display pattern (i.e., a right-eye plane). Then, the superimposition unit  13  supplies the left-eye plane and the right-eye plane to the display unit  14 . 
         [0039]    The display unit  14  displays, for example, a screen for left eye and a screen for right eye in a time-sharing manner based on the left-eye plane and the right-eye plane supplied from the superimposition unit  13 . At this time, for example, a user puts on shutter glasses synchronized with the switching of the screen for left eye and the screen for right eye to view the screen for left eye with only a left eye and view the screen for right eye with only a right eye. Accordingly, the user can view a 3D main image combined with a 3D subtitle. 
         [0040]    The audio decoder  15  performs a decoding process with respect to the inputted sound data, and supplies the resulting number of bits of the sound data to the subtitle decoder  12  as the sound information. Also, the audio decoder  15  supplies the sound data obtained as a result of the decoding process to the speaker  16 . 
         [0041]    The speaker  16  outputs the sound corresponding to the sound data supplied from the audio decoder  15 . Accordingly, the user can hear the sound corresponding to the image displayed by the display unit  14 . 
       [Description of a Process of the Image Processing Device] 
       [0042]      FIG. 5  is a flowchart illustrating a subtitle conversion process by the image processing device  10  in  FIG. 4 . The subtitle conversion process starts, for example, when the 3D content data is inputted to the image processing device  10 . 
         [0043]    In step S 11 , the audio decoder  15  performs the decoding process with respect to the inputted sound data, measures the resulting number of bits of the sound data as sound information V, and supplies the sound information V to the subtitle decoder  12 . 
         [0044]    In step S 12 , the subtitle decoder  12  determines whether the sound information V supplied from the audio decoder  15  is greater than a volume threshold (e.g., threshold value Vth). The threshold value Vth is included in, for example, the subtitle data. The subtitle decoder  12  performs the decoding process with respect to the subtitle data for 3D display, and acquires the threshold value Vth from the resulting subtitle data for left eye or subtitle data for right eye. 
         [0045]    When it is determined that the sound information V is greater than the threshold value Vth in step S 12 , process proceeds to step S 13 . In step S 13 , the subtitle decoder  12  changes image data of subtitle in the image data of the subtitle image included in the subtitle data for left eye and the subtitle data for right eye obtained as the result of the decoding process to image data in red color. Specifically, the subtitle decoder  12  changes the palette number, an RGB value, a YCbCr value, or a YPbPr value as the image data of subtitle to a value for red color. Note that the palette number is an 8-bit value when the number of colors that can be displayed is 256. The RGB value, the YCbCr value, and the YPbPr value are, for example, values of 24 (i.e., eight times three) bits. 
         [0046]    Since the color of the subtitle is changed to red color in step S 13  in this manner, a visual impression of the subtitle is strengthened. 
         [0047]    In step S 14 , the subtitle decoder  12  increases the alpha blending values included in the subtitle data for left eye and the subtitle data for right eye obtained as the result of the decoding process. 
         [0048]    Note that the alpha blending value is a value from 0 to 1; a greater alpha blending value indicates less transparency and a smaller alpha blending value indicates greater transparency. For example, when the alpha blending value is 1, image data corresponding to the alpha blending value is combined to be completely opaque. When the alpha blending value is 0, image data corresponding to the alpha blending value is combined to be completely transparent. 
         [0049]    Thus, as a result of a process in step S 14 , the transparency of the left-eye subtitle plane and the right-eye subtitle plane decreases. Accordingly, the subtitle can be seen more clearly than the main image, thus strengthening the visual impression. 
         [0050]    In step S 15 , the subtitle decoder  12  shifts a display position (Lx, Ly) included in the subtitle data for left eye obtained as the result of the decoding process in the horizontal direction by a shift amount “shift” corresponding to the sound information V to a display position (Lx+shift, Ly), and shifts a display position (Rx, Ry) included in the subtitle data for right eye in the horizontal direction by a shift amount “−shift” to a display position (Rx−shift, Ry). That is, the subtitle decoder  12  causes the display position of the subtitle image for left eye and the display position of the subtitle image for right eye to be further apart. Accordingly, the user can view the 3D subtitle popping out further toward the user side. After a process of step S 15 , the process proceeds to step S 16 . 
         [0051]    On the other hand, when it is determined that the sound information V is not greater than the threshold value Vth in step S 12 , the process proceeds to step S 16 . That is, in this case, processes of steps S 13  to S 15  are not performed, and the subtitle data for left eye and the subtitle data for right eye obtained as the result of the decoding process are not changed. 
         [0052]    In step S 16 , the subtitle decoder  12  generates the left-eye subtitle plane based on the subtitle data for left eye changed in steps S 13  to S 15  or the subtitle data obtained as the result of the decoding process, and generates the right-eye subtitle plane based on the subtitle data for right eye changed in steps S 13  to S 15  or the subtitle data obtained as the result of the decoding process. 
         [0053]    In step S 17 , the audio decoder  15  determines whether input of the 3D content data has ended, e.g., whether the sound data is no longer inputted. When it is determined that the input of the 3D content data has not ended in step S 17 , the process returns to step S 11  and subsequent processes are performed. 
         [0054]    On the other hand, when it is determined that the input of the 3D content data has ended in step S 17 , the process is terminated. 
         [0055]    The subtitle conversion process illustrated in  FIG. 5  is performed in a manner described above. Accordingly, when the volume of sound is great, the color of a subtitle to be displayed simultaneously with the sound is changed to red with decreased transparency and displayed to pop out toward the user side. That is, when the volume of the sound increases, the subtitle is highlighted. Thus, the user can further enjoy a change in sound. Thus, the image processing device  10  can display a 3D subtitle with increased effect. 
       Another Embodiment 
     [Configuration Example of an Image Processing Device According to Another Embodiment] 
       [0056]      FIG. 6  is a block diagram showing a configuration example of an image processing device according to another embodiment of the present invention. 
         [0057]    In  FIG. 6 , components identical to those in  FIG. 4  are denoted by the same reference numerals. Redundant description is omitted accordingly. 
         [0058]    The configuration of an image processing device  50  in  FIG. 6  differs from that in  FIG. 4  mainly in that a subtitle decoder  51  is provided instead of the subtitle decoder  12  and that a buffer  52  and a 3D subtitle generation unit  53  are newly provided. 
         [0059]    Instead of the subtitle data for 3D display, subtitle data for 2D display to which an offset amount “offset” and offset directions for left eye and right eye are added as offset information is inputted to the image processing device  50  in  FIG. 6 . Note that an offset direction refers to one horizontal (left or right) direction, and the offset direction for left eye and the offset direction for right eye are opposite directions. The subtitle data for 2D display includes image data of a subtitle image for 2D display, a display position of the subtitle image for 2D display on a screen, and an alpha blending value for the subtitle image for 2D display. 
         [0060]    The subtitle decoder  51  performs a decoding process with respect to the inputted subtitle data for 2D display. Based on sound information supplied from the audio decoder  15 , the subtitle decoder  51  changes the subtitle data for 2D display obtained as a result of the decoding process and the offset information which is added to the subtitle data for 2D display. Then, the subtitle decoder  51  associates the subtitle data for 2D display and the offset information after change and supplies the data and information to the buffer  52 . The buffer  52  associates and temporarily holds the subtitle data for 2D display and the offset information supplied from the subtitle decoder  51 . 
         [0061]    The 3D subtitle generation unit  53  reads the subtitle data for 2D display and the offset information from the buffer  52 . The 3D subtitle generation unit  53  shifts the display position included in the read subtitle data for 2D display in the offset direction for left eye and the offset direction for right eye included in the offset information each by the offset amount. The 3D subtitle generation unit  53  generates image data of screens in which the subtitle image for 2D display is arranged in resulting display positions as a left-eye subtitle display pattern (i.e., a left-eye subtitle plane) and a right-eye subtitle display pattern (i.e., a right-eye subtitle plane). Then, the 3D subtitle generation unit  53  supplies the left-eye subtitle plane and the right-eye subtitle plane to the superimposition unit  13 . Further, the 3D subtitle generation unit  53  supplies the alpha blending value included in the subtitle data for 2D display to the superimposition unit  13  as the alpha blending value for left eye and right eye. 
         [0062]    Since the image processing device  50  performs a 3D display of a subtitle using subtitle data for 2D display in a manner described above, there is compatibility with a related-art device that does not support 3D display of a subtitle. 
         [0063]    Note that the buffer  52  may not be provided in the image processing device  50 . 
       [Description of a Process of the Image Processing Device] 
       [0064]      FIG. 7  is a flowchart illustrating a subtitle conversion process by the image processing device  50  in  FIG. 6 . The subtitle conversion process starts, for example, when 3D content data is inputted to the image processing device  50 . 
         [0065]    Since processes of steps S 31  and S 32  in  FIG. 7  are similar to those of steps S 11  and S 12  in  FIG. 5 , description thereof is omitted. 
         [0066]    When it is determined that the sound information V is greater than the threshold value Vth in step S 32 , the subtitle decoder  51  changes image data of subtitle in the image data of the subtitle image included in the subtitle data for 2D display obtained as the result of the decoding process to image data in red color in step S 33 . 
         [0067]    In step S 34 , the subtitle decoder  51  increases the alpha blending value included in the subtitle data for 2D display obtained as the result of the decoding process. 
         [0068]    In step S 35 , the subtitle decoder  51  adds the shift amount “shift” corresponding to the sound information V to the offset amount “offset” included in the offset information added to the subtitle data for 2D display to obtain an offset amount “offset+shift”. That is, the subtitle decoder  51  shifts the display position of a subtitle image for left eye and the display position of a subtitle image for right eye in the offset direction for each eye by the shift amount “shift”. Then, the subtitle decoder  51  supplies the subtitle data for 2D display changed in steps S 33  and S 34  and the offset information in which the offset amount “offset” is changed to the offset amount “offset+shift” to the buffer  52  so as to be held. 
         [0069]    In step S 36 , the 3D subtitle generation unit  53  reads the subtitle data for 2D display and the offset information from the buffer  52 , and generates, as the left-eye subtitle plane, image data of a screen in which the subtitle image is arranged in a display position (x+(offset+shift), y) shifted in the offset direction by the offset amount “offset+shift” included in the offset information from a display position (x, y) included in the subtitle data for 2D display. 
         [0070]    Also, the 3D subtitle generation unit  53  generates, as the right-eye subtitle plane, image data of a screen in which the subtitle image is arranged in a display position (x−(offset+shift), y) shifted in the offset direction by the offset amount “offset+shift” included in the offset information from the display position (x, y). Then, the 3D subtitle generation unit  53  supplies the left-eye subtitle plane and the right-eye subtitle plane to the superimposition unit  13 , and supplies the alpha blending value included in the subtitle data for 2D display and changed in step S 34  to the superimposition unit  13  as the alpha blending values for left eye and right eye. 
         [0071]    On the other hand, when it is determined that the sound information V is not greater than the threshold value Vth in step S 32 , the 3D subtitle generation unit  53  reads the subtitle data for 2D display and the offset information from the buffer  52  and generates, as the left-eye subtitle plane, image data of a screen in which the subtitle image is arranged in a display position (x+offset, y) shifted in the offset direction by the offset amount “offset” included in the offset information from the display position (x, y) included in the subtitle data for 2D display in step S 37 . 
         [0072]    Also, the 3D subtitle generation unit  53  generates, as the right-eye subtitle plane, image data of a screen in which the subtitle image is arranged in a display position (x−offset, y) shifted in the offset direction by the offset amount “offset” included in the offset information from the display position (x, y). Then, the 3D subtitle generation unit  53  supplies the left-eye subtitle plane and the right-eye subtitle plane to the superimposition unit  13 , and supplies the alpha blending value included in the subtitle data for 2D display to the superimposition unit  13  as the alpha blending values for left eye and right eye. 
         [0073]    After a process of step S 36 , or after a process of step  37  when it is determined that the sound information V is not greater than the threshold value Vth in step S 32 , the process proceeds to step S 38 . Since a process of step S 38  is similar to that of step S 17  in  FIG. 5 , description thereof is omitted. 
         [0074]    The subtitle conversion process in  FIG. 7  is performed in a manner described above. Accordingly, when the volume of sound is great, the color of a subtitle to be displayed simultaneously with the sound is changed to red with decreased transparency and displayed to pop out toward the user side. That is, when the volume of the sound increases, the subtitle is highlighted. Thus, a user can further enjoy a change in sound. Therefore, the image processing device  50  can display a 3D subtitle with increased effect. 
         [0075]    Note that, all of the color, transparency, and position in the depth direction of the subtitle are changed when the volume of the sound is great in the subtitle conversion processes illustrated in  FIG. 5  or  7  described above. However, at least one of the color, transparency, and position in the depth direction of the subtitle may be changed. Further, the resultant color, transparency, and position in the depth direction of the subtitle after change are not limited to what is described above. 
         [0076]    Further, a display state of a subtitle image to be changed when the volume of sound is great is not limited to color, transparency, and position in the depth direction of a subtitle. For example, the position of a 3D subtitle in the horizontal direction may be changed when the volume of sound is great. 
         [0077]    Although only one threshold value for the sound information V is provided in the subtitle conversion process illustrated in  FIG. 5  or  7  described above, a plurality of threshold values may be provided. In such case, the degree of change in color or transparency of a subtitle after a change may be varied according to a value of the sound information V. For example, the color or transparency of a subtitle after the change may be changed in a stepwise manner according to a value of the sound information V. Note that the shift amount “shift” may be fixed to a constant amount instead of being set corresponding to the sound information V. 
         [0078]    Further, although the display state of the subtitle image is changed in response to a value of the sound information V in the description above, a display state of a subtitle image may be changed in response to a change in the value of the sound information V. For example, a display state of a subtitle image is changed when an increase or decrease in volume is extreme (i.e., when a difference between a first volume level and a second volume level exceeds a volume change threshold). 
         [0079]    A subtitle image may be an image of a subtitle in a unit of single character instead of being an image having a rectangular region including an entire subtitle to be displayed in one screen. 
         [0080]    Further, although the offset information is added to the subtitle data for 2D display and supplied in the description above, the offset information may be stored in advance in a storage unit (not illustrated) in the image processing device  10  ( 50 ). In this case, the position of a 3D subtitle in the depth direction is fixed to be constant. 
         [0081]    The embodiments of the present invention described above can be applied not only to a case where a main image is combined with a subtitle image but also to a case where a main image is combined with a sub-image (for example, a menu image) other than a subtitle image. 
       [Description of a Computer According to an Embodiment of the Present Invention] 
       [0082]    A sequence of processes described above can be performed with hardware or can be performed with software. When the sequence of processes is performed with software, a program included in the software is installed in a general-purpose computer or the like. 
         [0083]      FIG. 8  shows a configuration example of a computer according to an embodiment in which a program to execute the sequence of processes described above is to be installed. 
         [0084]    The program can be recorded in advance in a storage unit  208  as a recording medium built in the computer or a read only memory (ROM)  202 . 
         [0085]    Alternatively, the program can be stored (recorded) in a removable medium  211 . The removable medium  211  can be provided as a so-called software package. Examples of the removable medium  211  include a flexible disk, a compact disc read only memory (CD-ROM), a magneto optical (MO) disk, a digital versatile disc (DVD), a magnetic disk, and a semiconductor memory. 
         [0086]    Note that the program can be downloaded to the computer via a communication network or broadcast network and installed in the built-in storage unit  208  instead of being installed in the computer from the removable medium  211  described above via a drive  210 . That is, for example, the program can be transferred through wireless communication to the computer from a download site via a satellite for digital satellite broadcasting or can be transferred through wired communication to the computer via a network such as a local area network (LAN) or the Internet. 
         [0087]    The computer includes a central processing unit (CPU)  201 . The CPU  201  is connected to an input-output interface  205  via a bus  204 . 
         [0088]    When a user inputs an instruction via the input-output interface  205  by operating an input unit  206  or the like, the CPU  201  accordingly executes the program stored in the ROM  202 . Alternatively, the CPU  201  loads a program stored in the storage unit  208  to a random access memory (RAM)  203  and executes the program. 
         [0089]    Accordingly, the CPU  201  performs processes according to the flowcharts described above or performs processes to be executed with configurations illustrated in the above block diagrams. The CPU  201  causes the result of a process to be, for example, outputted from an output unit  207 , transmitted from a communication unit  209 , or stored in the storage unit  208  as necessary via the input-output interface  205 . 
         [0090]    The input unit  206  includes a keyboard, a mouse, and a microphone. The output unit  207  includes a liquid crystal display (LCD) and a speaker. 
         [0091]    In this specification, processes to be performed by the computer according to the program may or may not be performed chronologically in the order stated in the flowchart. That is, the processes to be performed by the computer according to the program may include a process executed in parallel or individually (for example, process using parallel processing or an object). 
         [0092]    The program may be executed by one computer (processor) or may be executed by distributed processing using a plurality of computers. Further, the program may be transferred to and executed by a remote computer. 
         [0093]    Further, embodiments of the present invention are not limited to those described above, and various modifications are possible within the scope of the present invention.