Abstract:
A method and apparatus is disclosed for presenting information to a user of an audiovisual appliance such as a television receiver, a set top box, or a DVD or a VCR player. The method includes extracting source text from a graphical representation of the source text in an associated audiovisual program; translating the extracted source text into a target text in a language different than a language of the source text; and presenting the target text in a human perceptible format in a synchronized manner with the associated audiovisual program. Translating the extracted source text may include an initial step of identifying the source language.

Description:
TECHNICAL FIELD 
   These teachings relate generally to method and apparatus for performing text translation from a source language to a target language and, more specifically, relate to a system wherein the source language information is received synchronized with a television broadcast or a pre-recorded audiovideo or audiovisual program (including but not limited to DVD or a VCR tape). 
   BACKGROUND 
   There are several means for communicating and displaying audiovisual programs of educational, commercial or entertainment value. These means include, but are not limited to, TV broadcasting and DVD or VCR playback. Any such program is made up of both audio and visual signals, or is made up of components that are coded together using analog or digital standard formats. The well known NTSC format, for example, is the standard for all analog audio and video TV broadcasting in the United States of America. In contrast, the DVD format uses a compressed digital representation of the video and audio signals. Frequently the audiovisual information is also coded together with textual information. A prominent example of this practice is that of the closed captioning (CC) of TV broadcasting in the United States. In order to allow the hearing impaired to participate in the enjoyment of TV programs, the Federal Communications Commission requires that all TV broadcasting in the United States include a coded signal of text that is representative of audio events and the speech content of the audio component of the TV program. In CC this textual information is embedded in the NTSC signal by representing text by binary codes corresponding to the letters of the alphabet, and using these codes to modulate portions of the NTSC signal. An EIA standard (EIA-608, Revision A, Recommended practice for Line  21  data service) describes the technical details of this process. A TV receiver capable of decoding and displaying closed captioned programs must extract these codes and then display the corresponding text as a subtitles on the TV screen. The process of displaying the text typically uses what is referred to as a font generator module; i.e., an electronic module that converts the binary codes into signals that drive the display of the text on the TV screen. All TV receivers presently sold in the United States are required to contain this type of font generator module. 
   Another, more conventional method to convey audio information in textual form is through graphical subtitles. As opposed to CC, where the alphanumeric characters that form displayable text are directly coded and transmitted, in graphical subtitling these characters are first converted into a graphical representation of same and then transmitted or coded in the graphical form. The advantage of the latter method over the former one is that no font generation is required to display the text, as the graphical representation as received can be directly overlaid on the TV screen. In addition to the simplicity in display electronics implementation, transmitting graphical representations of subtitles also allows the producer of the audiovisual content to have total control over the appearance of the subtitle text. That is, the producer can choose fonts, colors and other characteristics for the subtitle text in view of artistic and other criteria, such as having a least intrusive effect on the audiovisual content being displayed, and the producer can also dynamically change the appearance and aesthetics of the subtitle text as desired. 
   Graphical subtitles are commonly used to transmit textual information representative of the audio component of the TV program. One prominent example is found in the Digital Video Broadcast (DVB) standards for terrestrial, satellite and cable transmission of digital TV used in most of the world, including in satellite digital broadcasting in the United States. Another prominent example of so-called graphical subtitling can be found in the standards for pre-recorded content. 
   In the case of pre-recorded DVD programs, graphical subtitling is often used to support subtitles for more than one target language. However, the number of supported target languages is generally limited to but a few, which has been found to be insufficient for those countries with highly diverse ethnic populations. 
   The presence of closed captioning or graphical subtitling, however, provides an opportunity to implement language translation services and subtitles for an arbitrary number of target languages. To implement this service, the textual information in the source language must be extracted and translated to the target language of the viewer using text-to-text translation technology. Examples of this technology are found in several translation services that are available on the Internet. 
   As can be appreciated, extracting the textual information from the stream of binary codes used in closed captioning is relatively simple, however performing this same task with graphical subtitles is not simple nor intuitive. 
   With regard to solutions to the problems described above, Japanese patent 2000092460 (Mar. 31, 2000) describes a method for the automatic translation of CC text information from a source to a target language. This patent does not describe a method for the more common case of graphical subtitles and it does not describe the use of extensions for recognizing the source language automatically. 
   SUMMARY OF THE PREFERRED EMBODIMENTS 
   The foregoing and other problems are overcome, and other advantages are realized, in accordance with the presently preferred embodiments of these teachings. 
   In one of its aspects this invention provides a method and apparatus for extracting textual information received in a graphical subtitling format representative of a source language script, for translating the received source text into a target language text, and optionally displaying the translated text on a display screen. 
   In another one of its aspects this invention automatically recognizes the source language, and selects an appropriate translation process in accordance with the desired target language. 
   The teachings of this invention solve the foregoing problems related to displaying graphical subtitles. In one presently preferred embodiment of this invention text is extracted from the graphical representations using character recognition or another pattern matching technique. While similar methods are commonly used today in electronic scanners, where they are referred to as Optical Character Recognition (OCR), the use of simpler techniques is possible in a television application since the graphical representations are normally not contaminated by noise as is typically the case with electronic scanners. In certain cases, where the fonts used in generating the graphical subtitles are known to the decoding device, the process of extracting text may be reduced to simple look-up-table instructions. In any case, the resulting translated text may then be displayed as subtitles on the display screen by any of a number of methods, including using a font generator module. Optionally, the translated text could also be inputted into a text-to-speech synthesis unit to generate an audible signal representative of the subtitle information. A further embodiment of this invention may incorporate methods to automatically recognize the source language without requiring any prior viewer set up or interaction. This is of particular interest with currently available cable and satellite multilingual programming offerings. 
   Disclosed herein in accordance with the teachings of this invention are a real-time method and an apparatus for performing translation from a source language to a target language, and optionally displaying the results as subtitles on a display screen, such as a television screen. The source language information is assumed to be embedded in graphical form as part of displayable content, typically either broadcast or pre-recorded TV programs. The embedded graphical information is used to extract the corresponding textual information of the source language using either character recognition or another pattern matching technique. A text-to-text translation software program is then used to generate textual data for the target language. The textual data that results from the language conversion process are displayed on the TV screen, such as by displaying the textual data as subtitles or closed caption, and/or the textual data can be synthesized as speech. 
   In one presently preferred embodiment of this invention the method is practiced within and by a decoder of digitally transmitted or pre-recorded audiovisual programs of a type that include graphical subtitles. Examples of such decoders are digital Set Top Boxes and DVD players. In this embodiment the graphical subtitles are processed using at least one look-up table (LUT), or by character recognition or some other pattern matching technique. The textual information extracted in this manner is further processed in a text-to-text machine translation block. Optionally, a first function of this block is to automatically identify the language of the source. Text translated to the target language is then optionally displayed on the video screen by any of several possible and known techniques. For example, the translated text can be displayed by generating binary codes representative of CC data which are later passed to a font generation module, or alternately by overlaying a graphical representation of the text on the display memory buffer of a digital video decoder, such as an MPEG-2 decoder. Optionally, textual information may be converted to an audio format and presented as speech by a text-to-speech synthesis module or function. 
   In a further embodiment of this invention the method is used with analog video signals incorporating textual subtitles. Examples of such sources are analog TV and the output of VCR or DVD players. The video is digitized by means of an analog-to-digital converter, and the digitized video data is then processed to identify the location of blocks of text characters which are then processed as if they were graphical subtitles. After character recognition is performed by any suitable means the output text is processed further in a text-to-text machine translation block. Optionally, the first function of this block is to automatically identify the language of the source. Preferably the text is translated from the detected language to a language chosen by a viewer. The translated text and the audio and video data are multiplexed together whereby either subtitles or closed captions containing the translated text are generated. Optionally, the textual information may be presented in an audio format as speech by executing a text-to-speech synthesis function. The digital signal may then be converted back to the analog domain to be output from the device. 
   The methods and apparatus operate in substantially real time as the audiovisual program is received or played back. Suitable delays are provided for ensuring synchronicity between the generated translated textual information and the program content. 
   A method and apparatus are disclosed for presenting information to a user of an audiovisual appliance such as, but not limited to, a television receiver, a set top box, or a DVD or VCR player. The method includes extracting source text from a graphical representation of the source text in an associated audiovisual program; translating the extracted source text into a target text in a language different than a language of the source text; and presenting the target text in a human perceptible format in a synchronized manner with the associated audiovisual program. Translating the extracted source text may include an initial step of identifying the source language. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The foregoing and other aspects of these teachings are made more evident in the following Detailed Description of the Preferred Embodiments, when read in conjunction with the attached Drawing Figures, wherein: 
       FIG. 1  illustrates a block diagram of a first embodiment of apparatus in accordance with this invention for performing a subtitles translation from a language of origin (or source language) to a viewer language (or target language) during reception of a television program, or during DVD or VCR tape playback. 
       FIG. 2  is a block diagram of a second embodiment of apparatus for performing a subtitles translation according to the invention. 
       FIG. 3A  is a block diagram of the text extraction and character recognition block of  FIG. 1 . 
       FIG. 3B  is a block diagram of the text extraction and character recognition block of  FIG. 2 . 
       FIG. 4  is a block diagram of the text translation block shown in  FIGS. 1 and 2 . 
       FIG. 5  illustrates a block diagram of apparatus for practicing the teachings of this invention, the apparatus including circuits and logic blocks providing closed caption/subtitles generation, mixing with a video signal and digital-to-analog conversion as shown in  FIGS. 1 and 2 . 
       FIG. 6  is a block diagram of one exemplary embodiment of an audiovisual distribution system that incorporates the teachings in accordance with this invention. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Reference is made to  FIG. 1  for illustrating a block diagram of a first embodiment of a system  100  that is constructed and operated in accordance with this invention for performing a subtitles translation from a language of origin (or source language) to a viewer language (or target language) during reception of a transmitted audiovisual (e.g., television) program, or during DVD or VCR tape playback of an audiovisual program. In the system  100  certain input audio analog signals  100 A and video analog signals  100 B are digitized by an analog-to-digital converter  101 . The digitized audio data  101 A is recorded in an audio delay buffer  105  to enable full synchronization with the video signal and translated subtitles data at later stages. The digitized video data  101 B is processed in a character recognition block  102  having two outputs: output  102 A which is the digitized video itself, and an output  102 B which represents recognized textual information in the original (i.e., as-received) language. The digital video signal appearing at output  102 A is recorded in a video delay buffer  104  to enable full synchronization with the audio and translated subtitles data at later stages. The time delay provided by buffers  105  and  104  is preferably equal to the total required time to process and translate the subtitles or closed caption information, plus any system latencies and delays. 
   The character recognition block  102  recognizes the graphical representation of characters that are present in the digitized video signal  101 B by using any one of a number of suitable methods, such as by using a method based on pattern matching and/or OCR. 
   Referring to  FIG. 3A , the digital output  101 B of the ADC  101  represents luminance and chrominance signals, assuming a color television signal that is received from a cable or an antenna, or that is obtained from a DVD or VCR tape. By example, the color television signal may be compatible with the American NTSC (National Television Systems Committee) color television system, or with the European PAL (Phase Alternation Line rate) color television system, or with the French-Former Soviet Union SECAM (Sequential Couleur avec Memoire) color television system. The most significant difference between these three systems is the number of scan lines. NTSC uses 525 lines (interlaced,) while both the PAL and SECAM systems use 625 lines. NTSC frame rates are slightly less than ½ the 60 Hz power line frequency, while PAL and SECAM frame rates are exactly ½ the 50 Hz power line frequency. 
   Regardless of the color television system used the digitized signals are applied to a bit map constructor and processor  102 C that is bidirectionally coupled to a memory, referred to herein for convenience as a frame buffer  102 D. The processor  102 C constructs a video frame in the frame buffer  102 D so as to contain pixels and scan lines corresponding to a video image that would be viewed on a television receiver. In the preferred embodiment some number of frames are accumulated in the frame buffer  102 D and averaged or otherwise combined together when stored in the frame buffer  102 D. The exact number of frames to be accumulated to form the bit map is selected based on some criteria related to how rapidly the displayed alphanumeric information would be expected to change. One suitable but non-limiting value for the number of accumulated frames corresponds to a number of frames displayed in 0.5 second, or about 15 frames for a NTSC formatted television signal. The result is that the frame buffer  102 D contains memory locations corresponding to the alphanumeric symbols or textual characters that may be present in a subtitle or a closed caption, while the background video, assuming movement in the video image at the frame rate or near the frame rate, will appear as a noisy background signal. After some desired number of frames are accumulated (e.g., from one to about 15 for a NTSC formatted television signal), the content of the frame buffer  102 D is processed by an OCR block  102 E. The OCR block  102 E, or some other pattern recognizer, may operate in a manner similar to a conventional OCR function that is used to process a scanned and digitized page to locate and recognize individual alphanumeric characters. Optional feedback (FB) can be provided to the processor  102 C for indicating the status of the operation of the OCR block  102 E. For example, if the background becomes excessively noisy, making character recognition difficult, the FB signal may cause the processor  102 C, for example, to accumulate fewer video frames to form the bitmap, or to apply some type of filtering to the bitmap prior to the operation of the OCR block  102 E. The OCR block  102 E can also vary the size of the sampling window within which it examines the bitmap for potential characters. The end result is recognized alphanumeric characters or symbols that are output on line  102 B to the text-to-text translator  103  where the recognized textual information  102 B is processed further. 
   It should be noted that in most cases subtitles information is located in the bottom portion of the video screen image. As such, in order to decrease the amount of required frame buffer  102 D memory, while increasing processing speed, it may be preferred to only accumulate and process video frame information that corresponds to the bottom portion (e.g., the bottom third or bottom quarter) of the video image. 
   It should further be noted that it is not necessary that the target text be stationary in the image, and that scrolling or crawling text may also be recognized and translated. 
   A logical block diagram for text-to-text machine translation block  103  is shown in  FIG. 4 . A first function of text-to-text machine translation block  103  is to automatically identify the source language if requested by the viewer. For the first embodiment of this invention the automatic language detection is performed in block  401  of  FIG. 4 , and is based on the character set used in the source language and optionally also on any special features or characteristics of the language, or even on explicitly given language identifiers, all of which are referred to generally as control information  102 C. Upon completion of the operation of block  401  the text is translated from the original, and possibly automatically detected, language (the source language) to the language chosen by a viewer (the target language) in a text-to-text machine translation block  402 . Translation can be performed by any suitable technique for converting an alphanumeric string that represents a sentence in one language to a sentence in another language. The translated text is output on line  103 A to block  106  of  FIG. 1 . Either subtitles or closed captions with translated text are generated in block  106 . The translated text and video data from the video delay buffer  105  are then combined in block  106  and multiplexed with the delayed digitized audio data output from the audio buffer  105  before being directed to the video display (not shown in  FIG. 1 ). The end result is that the source text is presented to the viewer after translation to the target text, with the translation being to a language selected by the user (e.g., English to French, Swedish to Hebrew, etc.) 
     FIG. 5  illustrates a block diagram of the subtitles/closed caption generator, mixer and digital to analog converter (DAC) block  106 . The translated text  103 A is applied to both a closed caption generator  501  and a subtitles generator  503 . The outputs of blocks  501  and  503  are fed into multiplexer  502  that receives a control signal  106 A from the viewer by means of, for example, a remote control (e.g., IR) link. The output of block  502  is input to block  504  which mixes the delayed video digital signal  104 A with the selected one of closed caption or subtitles data output from the multiplexer  502 . The output of mixer block  504  is input to a digital-to-analog converter (DAC)  505  that produces an analog TV signal, for example an analog TV signal in the NTSC format. 
   Note in  FIG. 1  that the textual information may be presented to the viewer in an audio (speech) signal format by performing text-to-speech synthesis in block  107 . The choice of textual or audio (or both) is preferably made user-selectable. The output  207 A of the synthesizer  207  can be multiplexed into the audio signal  105 A. 
   With reference to the system  200  shown in  FIG. 2 , in a further embodiment of this invention an input MEG-2 or DVD (by example) bit stream  200 A is processed by a demultiplexer block  201  that extracts video, audio, subtitles and control data from their respective channels in the bit stream. The audio data  201 A is stored in an audio delay buffer  205  to enable full synchronization with video and translated subtitles data at a later stage, and the video data output on line  201 C from the demultiplexer  201  is recorded in a video delay buffer  204  to enable full synchronization with the audio and translated subtitles data at a later stage. The extracted subtitles data  201 B are processed in a character recognition block  202  that has as an output  202 A textual information in the original language. A block diagram of the character recognition block  202  is shown in  FIG. 3B . First, a run-length decoding of the graphical data is performed by block  301 , followed by a separation in block  302  of the background from the recognized characters. The characters can be recognized by any suitable means, preferably one based on correlation, and are output on line  202 A. 
   Returning to  FIG. 2 , the textual information output on line  202 A is processed further in a text-to-text machine translation block  203  which can be functionally identical to the corresponding block  103  shown in  FIGS. 1 and 4 . One function of block  203  is to automatically identify the language of the source if this feature is requested by the viewer. For the second embodiment of the invention now being described the automatic language detection performed in block  401  of  FIG. 4  is based on control information  201 D that is extracted in demultiplexer block  201  (such as a language code), or is based on the character set used in the source language and special features of languages. The text is then translated from the detected language to the language chosen by the viewer in block  402 , as described above. 
   Still referring to  FIG. 2 , the buffered video data  204 A and buffered audio data  205 A are decoded by dedicated MPEG-2 video and audio decoders  208  and  209 , respectively. The translated text  203 A as well as the decoded video data  208 A are multiplexed together in block  206 , where either subtitles or closed captions with translated text are generated as shown in  FIG. 5 . As in the analog embodiment of  FIG. 1 , it may be desirable present the textual information as a speech signal by performing text-to-speech synthesis in block  207 . 
   For the case where the second embodiment depicted in  FIG. 2  is embodied as a module or a subsystem of a further system or audiovisual appliance, such as a DVD player or a set-top-box, the functionality of at least blocks  204 ,  205 ,  206 ,  208  and  209  can be performed by the further system as a part of its operation such that the system  200  may need to contain only those blocks shown as  201 ,  202 ,  203  and  207 . That is, the functionality of the system  200 , as well as the system  100 , may be distributed over two or more systems. Further in this regard, and relevant also to  FIG. 1 , while the blocks shown in the Figures have been described as hardware blocks, a number of these blocks may be implemented by a suitably programmed data processor or data processors as algorithms and processes. Still further in this regard, the block diagrams of  FIGS. 1–5  maybe viewed as well as logic flow diagrams, wherein the individual blocks are implemented by hardware circuitry, by software instructions executed by a data processor and stored on or within a computer-readable media, or by a combination of hardware and software instructions. Still further in this regard, and also relevant to  FIG. 1 , the blocks shown in the Figures may be integrated within one or more integrated circuits. 
   Referring to  FIG. 6 , there is shown a non-limiting example of a video distribution system  600  that incorporates the teachings in accordance with this invention. An audiovisual program service provider  602  sends an audiovisual program to a viewer&#39;s audiovisual program receiver, such as a television  604 , via an interface such as a set-top-box (STB)  606 . The STB  606  may include the text recognition, translation and display system  608  in accordance with the embodiment of either  FIG. 1  or  FIG. 2 , or the text recognition, translation and display system  608  may be provided as a separate, stand-alone unit. Alternatively, the text recognition, translation and display system  608  could be built into the audiovisual program receiver, such as the television  604 . 
   The audiovisual program is sent to the STB  606  via any suitable transport media  603 , such as through wiring in a cable, or through a fiber optic cable, or through a terrestrial transmitter, or through a satellite transmitter. The signal conveying the audiovisual program can be a point-to-point signal sent specifically to the viewer, or it can be a point-to-multipoint signal that is sent to a number of viewers simultaneously. A back channel (not shown) for providing viewer interactivity may also be employed. 
   In one embodiment a business process can be realized in which the operation of the text recognition, translation and display system  608  is provided as a service (with or without a fee) by the video service provider  602  or by some other entity  610 . In this case the target language translation function may be selected to be activated by the viewer, and appropriate software is then enabled in the system  608  (and possibly also in the STB  606 ) or the software, if not already resident, may be downloaded to the system  608  (and possibly also to the STB  606 ) by the service provider  602  or by the other, third party entity  610 . 
   In another embodiment it may be the case that all of the functionality of the system  608  is merged into and executed by the STB  606 , and thus one inspecting the interface to the television  604  may not discern a specific component or module that could be readily identified as being associated only with the text recognition, translation and display system  608  of this invention. However, the presence of the text recognition, translation and display system  608  will be discernable by its functioning and the resultant visual and/or audio output. 
   In a further embodiment  FIG. 6  is modified to derive the source of the audiovisual program from a DVD or from a VCR tape or from some other audiovisual storage media. In this case the text recognition, translation and display system  608  may be separate from or integrated with the DVD or VCR player. 
   While described above in the context of certain presently preferred embodiments of this invention, these teachings are not intended to be limited to only the disclosed embodiments, as changes in form and detail thereof may become apparent to those skilled in the art when guided by the foregoing teachings.