Abstract:
A digital versatile disc (DVD) playback device capable of recognizing characters comprises a character recognition unit to converse subtitle pictures recorded in a DVD into character codes. Therefore, the DVD playback device may provide useful information by analyzing the conversed character codes by means of a post process unit thereof for a use in other applications.

Description:
[0001]     This application claims the benefit of the filing date of Taiwan Application Ser. No. 093106280, filed on Mar. 10, 2004, the content of which is incorporated herein by reference.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of Invention  
         [0003]     The present invention relates to a digital versatile disc (DVD) playback device, and particularly to a DVD playback device capable of recognizing characters in sub-pictures by converting sub-pictures into character codes.  
         [0004]     2. Related Art  
         [0005]     In general, digital versatile data stored on a DVD includes versatile data, such as video, audio and subtitle, and information for playing control. When a DVD playback device playbacks a DVD, it uses a video decoder, an audio decoder and a sub-picture decoder to decode the video data, audio data and subtitle, respectively.  FIG. 1  illustrates a schematic architecture of a general DVD playback device. As shown in  FIG. 1 , the DVD playback device  10  comprises a navigator  11 , a demultiplexer  12 , a decoder  13 , an audio post processing unit  14 , an audio output unit  15 , a video post processing unit  16 , a video output unit  17 , a user interface  18  and a control module  19 . The control module  19  outputs playing control signals to the navigator  11  in response to an input command, which is input by a user. In response to the playing control signals, the navigator  11  retrieves digital versatile data from a DVD  111  and transmits the digital versatile data into the demultiplexer  12 . The demultiplexer  12  sends the audio data, video data and sub-picture units to the decoder  13 . The decoder  13  includes an audio decoder  131 , a video decoder  132  and a sub-picture decoder  133  for receiving and decoding the audio data, video data and sub-picture units, respectively.  
         [0006]     Generally, the subtitle picture is recorded in the DVD in a bitmap format.  FIG. 2  depicts a data structure of a sub-picture unit (SPU) used in a DVD. The SPU contains a SPH (Sub-Picture Header)  21 , a PXD (Pixel Data)  22 , and a Sub-Picture display control sequence table (SP_DCSQT)  23 . The SPH  21  contains information associated with the dimension of a sub-picture and the displaying position of the control sequence table. The PXD  22  contains a top field data portion and a bottom field data portion and is composed of foreground color, background color, solid color  1  and solid color  2 . The PXD  22  are encoded by a run-length coding scheme. The SP_DCSQT  23  contains one to several control sequences, each of which is used to control a start, an end and an attribute of a subtitle. The sub-picture decoder  133  may decode the above information and generates subtitle pictures and displaying information associated therewith, such as time, position, color contrast and the like. The subtitle picture is displayed according to the displaying time. On the other hand, the audio decoder  131 , the video decoder  132  and the sub-picture decoder  133  have their outputting time sequence according to system timing.  
         [0007]     However, there is a disadvantage existed in the current DVD playback device. The playback device only displays the subtitle pictures corresponding to the sub-picture units but not provide further information associated with characters in the subtitle pictures.  
       SUMMARY OF THE INVENTION  
       [0008]     In view of the above, it is an object of the present invention to provide a DVD playback device capable of recognizing characters in the sub-picture units.  
         [0009]     To achieve the above object, the DVD playback device capable of recognizing characters in the sub-picture units according to the present invention comprises a control module for generating playing control signals and a character recognition control signal in response to an operation command, a navigator for retrieving versatile data, generating an output signal in response to the play control signals and generating a setting signal in response to navigation data in the sub-picture unit set as desired to be read, a demultiplexer for outputting audio data, video data and sub-picture units in response to the output signal from the navigator, an audio decoder for receiving the audio data and generating a decoded audio signal, a video decoder for receiving the video data and generating a decoded video signal, a sub-picture decoder for receiving and analyzing the sub-picture units and generating subtitle pictures and an enable signal, and a character recognition unit for recognizing characters in the subtitle pictures in response to the setting signal, character recognition control signal and the subtitle pictures.  
         [0010]     As thus constructed, the DVD playback device capable of recognizing characters according to the present invention may output character codes of characters in the subtitle pictures and may further provide an interactive operation accordingly. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]     The invention will become more fully understood from the detailed description given hereinbelow illustration only, and thus are not limitative of the present invention, and wherein:  
         [0012]      FIG. 1  depicts a schematic architecture of a prior DVD playback device.  
         [0013]      FIG. 2  is a schematic structure of a sub-picture unit used in a DVD.  
         [0014]      FIG. 3  is a flowchart of a method for character recognition.  
         [0015]      FIG. 4  illustrates a block diagram of a first embodiment of a DVD playback device capable of recognizing characters according to the present invention.  
         [0016]      FIG. 5  illustrates a block diagram of another embodiment of a DVD playback device capable of recognizing characters according to the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0017]     The DVD playback device capable of recognizing characters according to the present invention will be described in more detail with reference to the drawings.  
         [0018]     For a general DVD playback device, a user selects some desired functions and set some parameters to playback the DVD only according to his needs or control information provided by the playing digital versatile data in the DVD. However, the present invention provides an additional function of character recognition in a DVD playback device so that the DVD playback device may provide further information in the subtitle pictures by analyzing the subtitle pictures using the character recognition function.  
         [0019]      FIG. 3  shows an operation flow of a general optical character recognition. As shown in  FIG. 3 , a recognition system first scans an original document and then generates a raw image (Step  31 ). Then the recognition system pre-processes the raw image, such as inclination correctness, spot elimination and color processing, to generate a pre-processed image which is easy to be recognized (Step  32 ). Therefore, a succeeding character recognition operation may be smoothly performed without significant interferences according to the pre-processed image. Next, the recognition system analyzes the pre-processed image to extract character, table, picture sections and the like therein respectively and to generate an analyzed image (Step  33 ). Finally, the recognition system recognizes the characters in the analyzed image by use of a character library and outputting the recognized characters (Step  34 ), wherein a word library and a comparison of associated words are used to promote correctness of the character recognition. The character library can be selected according to different languages, fonts and forms of the characters. The word library and the associated words may also vary as the language corresponding to the recognized characters.  
         [0020]      FIG. 4  illustrates a schematic architecture of a first embodiment of the DVD playback device capable of recognizing characters. As shown, the DVD playback device  40  comprises a navigator  41 , a demultiplexer  42 , a decoder  43 , an audio post processing unit  44 , an audio output unit  45 , a video post processing unit  46 , a video output unit  47 , a user interface  48 , a control module  49  and a character recognition unit  51 . The decoder  43  includes an audio decoder  431 , a video decoder  432  and a sub-picture decoder  433 . As comparing to the prior DVD playback device schematically shown in  FIG. 1 , the DVD playback device  40  is additionally provided with a character recognition unit  51 . In operation, the character recognition unit  51  performs the character recognition operation after receiving a character recognition control signal from the control module  49 , a setting signal from the navigator  41 , subtitle pictures and an enable signal from the sub-picture decoder  433 . The navigator  41  not only retrieves general versatile data but also reads plug-in subtitle information. The reading operation and mechanism of the plug-in subtitle information are the same as the prior technologies associated therewith and the related description is omitted herein.  
         [0021]     As above mentioned, the sub-picture decoder  433  generates each subtitle picture displaying unit and displaying information corresponding thereto, including time, position, color contrast information and the like. Therefore, an enable signal is generated simultaneously when the subtitle picture displaying unit is sent or displayed from the sub-picture decoder  433 . In response to the subtitle picture displaying unit, the character recognition unit  51  may recognize the characters in the subtitle picture displaying unit.  
         [0022]     However, recognition of characters is influenced by different languages, words and fonts corresponding to the characters. In light of this, the character recognition unit  51 , as compared to the prior recognition technology, will load in different word libraries and character libraries after receiving the setting signal from the navigator  41 , in which the setting signal comprises navigation data such as language and dimension of the characters. Further, the adopted recognition mechanism is different from the prior one, e.g. only 26 letters are required to be recognized when the to-be-recognized characters are English but they need to be combined into words. However, Chinese characters are required to be recognized each word. Alternatively, the character recognition unit  51  may further process the recognized characters in response to the character recognition control signal.  
         [0023]     Generally, a character recognition operation may be divided into an image pre-processing step and an actual character recognition step. The image pre-processing step is performed to make the picture easy to be recognized and extract each character out of the characters in the image by analyzing them and the character recognition step is performed to recognize each of the characters and enhance correctness of the character recognition with an aid of the associated words stored in the word library. The character recognition operation is ordinary to a skilled person of the art and the description associated therewith will be omitted herein.  
         [0024]     The character recognition unit  51  enters a character recognition mode only after a character recognition control signal is enabled. In the character recognition mode, the character recognition unit  51  first set a language corresponding to the to-be-recognized characters according to the setting signal from the navigator  41 , such as Chinese, English, Japanese and the like. Also, a language library as required is loaded in, such as information corresponding to the language set. In addition, a corresponding algorithm used for character recognition may also be loaded in. As mentioned above, the character recognition unit  51  will detect the enable signal and recognize the characters in the subtitle picture outputted from the sub-picture decoder  433  when the enable signal is enabled. Then, the character recognition unit  51  outputs recognized character codes, such as ASCII codes when English is the language corresponding to the characters. In actual operation, the character recognition unit  51  may be incorporated or integrally formed in the sub-picture decoder  433 .  
         [0025]     Referring to  FIG. 5 , another embodiment of the DVD playback device capable of recognizing characters according to the present invention is illustrated therein. As shown, the DVD playback device  50  comprises a playing unit  52 , a character recognition unit  51 , a user interface  53  and a control module  54 . The playing unit  52  generates audio and video output signals after receiving audio and video data. In addition to the versatile data information, the playing unit  52  may also receive plug-in subtitle information. Besides the audio and video output signals, the playing unit  52  also outputs subtitle pictures corresponding to the subtitle information, an enable signal and a setting signal to the character recognition unit  51 . In addition to a playing control signal, the control module  54  also outputs a character recognition control signal to the character recognition unit  51 , such as controlling activating the character recognition function of the character recognition unit  51  and selecting a specific type of character codes corresponding to the characters.  
         [0026]     After receiving the subtitle pictures, the enable signal and the setting signal, the character recognition unit  51  recognizes the characters in the subtitle pictures and outputs the character codes corresponding thereto. The outputted character codes have different formats and definitions depending upon the language and the character recognition control signal. For examples, if the corresponding language is English, the character codes used are ASCII codes. If the corresponding language is traditional Chinese, the character codes used are BIG5 codes. The “enable signal” is thus named since when it is received, the character recognition unit  51  is triggered to recognize the characters in the subtitle pictures. The “setting signal” is thus named since the language corresponding to the characters to be recognized by the character recognition unit  51  is set by this signal, which is issued by the playing unit  52  according to navigation data corresponding to the to-be played subtitle pictures. With the language information from the setting signal, the character recognition unit  51  may use the corresponding library and algorithm in its character recognition task.  
         [0027]     While the preferred embodiments of the present invention have been set forth for the purpose of disclosure, modifications of the disclosed embodiments of the present invention as well as other embodiments thereof may occur to those skilled in the art. Accordingly, the appended claims are intended to cover all embodiments which do not depart from the spirit and scope of the present invention.