Method and apparatus for providing dual language captioning of a television program
First Claim
1. In decoder apparatus for decoding data encoded on particular horizontal lines of a vertical blanking interval of a composite video signal, a method for decoding the encoded data characterized by the steps ofreceiving the encoded data as a serial data stream of data frames, each data frame comprising a synchronization field and two data bytes.retrieving data packets from the data frames,decoding the data packets, each data packet comprising a plurality of data bytes, the data packets indicated by particular bit indications appearing in one of the plurality of bytes of each data packet,storing a plurality of letter components in memory for at least two languages, a first language having the Roman alphabet and a second language having a syllabic alphabet,determining if the data packet represents a non-printable character, andmapping remaining bit positions of the data packet for a printable character into a number of letter component pointer bytes less than or equal to the number of bytes comprising the data packets, the letter component pointer bytes for pointing to one of a Roman alphabet letter or a syllabic alphabet letter component in memory for display.
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Abstract
A method of decoding data for a language having the Roman alphabet or a language having a syllabic alphabet from a composite video signal comprises the steps of receiving the data in the form of data packets and determining from bit values stored at particular bit positions whether the data is control data or represents printable character data comprising a head code or a tail code. Once it is determined that the data represents either a head code or a tail code of a printable character, the data bytes are valued for parity and, from that determination, a letter component is generated which points to a letter component or complete character for one or the other alphabet. Because characters of a syllabic language may be quite complex, the step of displaying the syllabic language character includes the steps of overlaying two or more letter components to form the syllabic character image. Furthermore, the syllabic language character is displayed having a height of approximately three quarters inch on a standard resolution NTSC signal television screen.
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Citations
28 Claims
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1. In decoder apparatus for decoding data encoded on particular horizontal lines of a vertical blanking interval of a composite video signal, a method for decoding the encoded data characterized by the steps of
receiving the encoded data as a serial data stream of data frames, each data frame comprising a synchronization field and two data bytes. retrieving data packets from the data frames, decoding the data packets, each data packet comprising a plurality of data bytes, the data packets indicated by particular bit indications appearing in one of the plurality of bytes of each data packet, storing a plurality of letter components in memory for at least two languages, a first language having the Roman alphabet and a second language having a syllabic alphabet, determining if the data packet represents a non-printable character, and mapping remaining bit positions of the data packet for a printable character into a number of letter component pointer bytes less than or equal to the number of bytes comprising the data packets, the letter component pointer bytes for pointing to one of a Roman alphabet letter or a syllabic alphabet letter component in memory for display.
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8. In decoder apparatus for decoding encoded data received on particular horizontal lines of a vertical blanking interval of a composite video signal, a method for decoding the encoded data characterized by the steps of
decoding data packets, each data packet comprising one head code and three tail codes, the data packets indicated by particular bit indications appearing in the head code of each data packet, storing a plurality of letter components in memory for at least two languages, a first language having the Roman alphabet and a second language having a syllabic alphabet, determining if the data packet represents a non-printable character, and mapping remaining bit positions of the data packet for a printable character into a number of letter component pointer bytes less than or equal to the number of bytes comprising the data packets, the letter component pointer bytes for pointing to a Roman alphabet letter or a syllabic alphabet letter component in memory for display.
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9. In decoder apparatus for decoding encoded data received on particular horizontal lines of a vertical blanking interval of a composite video signal, a method for decoding the encoded data characterized by the steps of
decoding data packets, each data packet comprising four bytes, the data packets indicated by particular bit indications appearing in one of the four bytes of each data packet, storing a plurality of letter components in memory for at least two languages, a first language having the Roman alphabet and a second language having a syllabic alphabet, determining if the data packet represents a non-printable character, and mapping remaining bit positions of the data packet for a printable character into a number of letter component pointer bytes less than or equal to the four bytes, the letter component pointer bytes for pointing to a Roman alphabet letter or a syllabic alphabet letter component in memory for display.
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14. Apparatus for decoding encoded data received on particular horizontal lines of a vertical blanking interval of a composite video signal, the apparatus comprising
a data extractor for extracting the encoded data from the particular horizontal lines of the vertical blanking interval and outputing the extracted data, a closed caption data controller, responsive to the data extractor, for stripping parity from the received data, for determining if the data comprises a printable character, and for outputing pointer data, a display random access memory having a plurality of pointer registers responsive to the closed caption data controller, and a character memory, responsive to the display random access memory, for outputing selected character data, the apparatus characterized in that the closed caption data processor further determines the identity of a head code or a tail code of printable character data from predetermined bit positions of the received printable character data, the printable character data representing a syllabic character or a Roman alphabet character and comprising a first plurality of bytes, the first plurality of bytes of printable character data being translated into a lesser number of letter component pointer bytes and the display random access memory stores letter component pointer data for uniquely pointing to a syllabic character letter component in the character memory.
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22. In decoder apparatus for decoding data encoded on particular horizontal lines of a vertical blanking interval of a composite video signal, a method for decoding the encoded data characterized by the steps of
receiving the encoded data as a serial data stream of data frames, each data frame comprising a synchronization field and two data bytes, retrieving data packets from the data frames, decodeing the data packets, each data packet comprising a plurality of data bytes, the data packets indicated by particular bit indications appearing in one of the plurality of bytes of each data packet, storing a plurality of letter components in memory for a first language having a syllabic alphabet, mapping remaining bit positions of each data packet into a number of letter component pointer bytes less than or equal to the number of bytes comprising each data packet, the letter component pointer bytes for pointing to two or more letter components in memory for display, retrieving the two or more letter components corresponding to the letter component pointer bytes from the memory, and creating a letter block by overlaying the two or more retrieved letter components.
Specification