Closed-caption broadcasting and receiving method and apparatus thereof suitable for syllable characters

• US 6,295,093 B1
• Filed: 05/05/1997
• Issued: 09/25/2001
• Est. Priority Date: 05/03/1996
• Status: Expired due to Term

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Park, Hyun-Jeong, Yang, Jin-Hwa, Bae, Jum-Han
• Primary Examiner(s): Peng, John K.
• Assistant Examiner(s): Natnael, Paulos M.
• Application Number:
  US08/851,296
• Time in Patent Office: 1,604 Days
• Field of Search: 348/484, 348/468, 348/473, 348/478, 348/476, 348/589, 348/596, 348/600, 434/307 A
• US Class Current: 348/473
• CPC Class Codes: H04N 21/4884 for displaying subtitles
• CPC Class Codes: H04N 5/278 Subtitling
• CPC Class Codes: H04N 7/0885 for the transmission of subtitles

Abstract

A closed-caption broadcasting and receiving method and apparatus. According to the closed-caption broadcasting method and apparatus, character information and control information are inputted, and a control code of 2 words and a character code of 2 words including a syllable character completion type code are produced. The control code is obtained by combining the control information with a mode control bit and a parity bit, and the character code is obtained by combining the character information with a mode control bit and a parity bit. A digital-modulated caption signal is produced by inputting the control code and the character code, and is coded on a scanning line which does not affect a television video signal to be transmitted.

Claims

1. A closed-caption broadcasting method comprising the steps of:

inputting character information and control information;

producing a control code of two words by combining said control information with a first mode control bit and a first parity bit, and a character code of two words including a syllable character completion type code by combining said character information with a second mode control bit and a second parity bit;

digitally-modulating said control code and said character code to generate a digital-modulated caption signal; and

coding said caption signal in at least one scanning line which does not affect a television image signal to transmit said caption signal.

2. A closed-caption broadcasting method as claimed in claim 1, wherein each of said 2 words includes 9 bits.

3. A closed-caption broadcasting method as claimed in claim 1, wherein said syllable character completion type code is a Hangul completion type KSC 5601 code.

4. A closed-caption broadcasting method as claimed in claim 1, wherein said at least one scanning line which does not affect said television image signal is one of a 262nd line of an odd field and a 525th line of an even field of the television signal.

5. A closed-caption broadcasting method as claimed in claim 1, wherein said caption signal comprises:

a bit clock sync signal which is a first sine wave of a predetermined period, and has a frequency obtained by dividing a chrominance subcarrier of said television signal at a predetermined rate;

a word start signal which is a second sine wave of one period, and has a frequency obtained by dividing said bit clock sync signal at a predetermined rate; and

an 18-bit data signal modulated to a third sine wave having a frequency lower than said frequency of said bit clock sync signal and higher than said frequency of said word start signal.

6. A closed-caption broadcasting method as claimed in claim 5, wherein said data signal is modulated by a binary phase shift keying (BPSK) method.

7. A closed-caption broadcasting method as claimed in claim 5, wherein said frequency of said bit clock sync signal is obtained by dividing said frequency of said chrominance subcarrier by 4.

8. A closed-caption broadcasting method as claimed in claim 5, wherein said frequency of said word start signal is obtained by dividing said frequency of said bit clock sync signal by 4.

9. A closed-caption broadcasting method as claimed in claim 5, wherein said sine wave frequency of said data signal is obtained by dividing said frequency of said bit clock sync signal by 2.

10. A closed-caption broadcasting method as claimed in claim 5, wherein said bit clock sync signal includes 6 periods.

11. A closed-caption broadcasting method as claimed in claim 5, wherein a maximum level of said caption signal is 90±

IRE.

12. A closed-caption broadcast receiving method comprising the steps of:

detecting horizontal and vertical sync signals of a received television signal;

extracting a caption signal encoded in a last scanning line of said television signal by counting said horizontal sync signal in response to said detected vertical sync signal;

restoring digital data from said extracted caption signal;

detecting an error of said restored data;

decoding a control code of said restored data and reading out character data corresponding to a character code from a font ROM (read only memory) in which said character data is stored and based on a syllable character completion type code, and storing said read-out character data in a display memory; and

converting said character data stored in said display memory into a video signal to display said video signal on a display screen.

13. A closed-caption broadcasting apparatus for superimposing closed-caption information in a video signal and modulating an audio signal and said video signal to a television signal to transmit said modulated television signal in the air as a high frequency signal, the apparatus comprising:

character information input means for inputting additional information related to at least one of a television scene, emergency news, and an announcement, as a 2-byte syllable character completion type code;

control information input means for inputting 7-bit control information for reception control of a closed-caption broadcast;

character code generating means for generating a data packet of an 18-bit character code by using an MSB (most significant bit) of each byte of said 2-byte syllable character completion type code as a caption word/additional information flag, replacing said MSB by a first value in case of said additional information, and adding a parity bit to each byte of said 2-byte syllable character completion type code;

control code generating means for generating a data packet of an 18-bit control code by dividing said 7-bit control information into an upper 4 bits and a lower 3 bits, creating an upper byte by adding to said upper 4 bits a parity bit, control code discriminating bits of 2 bits, and a word/addition flag, creating a lower byte by adding to said lower 3 bits a first parity bit, a second parity bit, control code discriminating bits of 2 bits, and a caption word/additional information flag, and adding another parity bit to each of said upper and lower bytes;

data packet modulating means for modulating said data packet generated by said character code generating means or said control code generating means by digital modulation to produce a caption signal;

synchronous counter means for receiving horizontal and vertical sync signals of said video signal and counting said horizontal sync signal, said synchronous counter means being reset by said vertical sync signal;

window signal generating means for receiving a counted value of said synchronous counter means and generating a window signal for selecting a predetermined line of each field; and

switching means for selectively switching said video signal and said caption signal in response to said window signal.

15. A closed-caption receiving apparatus as claimed in claim 13, further comprising:

a receiver to receive said television signal transmitted in the air, including

a data extractor to extract said caption signal from said video signal,

a sync separator to separate a sync signal from said video signal to produce vertical and horizontal sync signals,

a first memory to store character information corresponding to the syllable character completion type code,

a second memory to store address information of said first memory, and

caption processing means for analyzing said data extracted by said data extractor and detecting an existence of an error in said data, said caption processing means performing a corresponding control process if said data extracted by said data extractor is identified as a control code, while storing only a code using the syllable character completion type code in said second memory, and generating data read out from said first memory, which is addressed by a value stored in said second memory, as another video signal.

16. A closed-caption receiving apparatus as claimed in claim 13, wherein:

said first memory is a read only memory (ROM); and

said second memory is a random access memory (RAM).

14. A closed-caption receiving apparatus for receiving a caption signal from a received composite video signal, said apparatus comprising:

a data extractor for extracting said caption signal from said composite video signal;

a sync separator for separating a sync signal from said composite video signal to produce vertical and horizontal sync signals;

a font ROM (read only memory) for storing character information corresponding to a syllable character completion type code;

a RAM (random access memory) for storing address information of said font ROM; and

caption processing means for analyzing said data extracted by said data extractor and detecting an existence of an error in said data, said caption processing means performing a corresponding control process if said data is identified as a control code as a result of the data analysis, while storing in said RAM only a code using said syllable character completion type code, and producing data read out from said font ROM, which is addressed by a value stored in said RAM, as another composite video signal.

17. A broadcasting system for generating a television signal by encoding a caption signal in a video signal, comprising:

a video processor to process the video signal; and

a caption encoder for generating and encoding the caption signal into the video signal, said caption encoder including

a synchronous counter to receive sync signals from said video processor, to count a horizontal sync signal to select predetermined scanning lines of the video signal, and is reset by a vertical sync signal, and

a switching unit to alternately output the video signal and the caption signal based upon the counted value to superimpose the caption signal in specific lines of the video signal, to generate the television signal.

18. A broadcasting system as claimed in claim 17, wherein said switching unit comprises:

a window signal generator to generate a switching signal based upon the counted value of the synchronous counter; and

a switch to alternately output the video signal and the caption signal based upon the switching signal.

19. A broadcasting system as claimed in claim 17, wherein said caption encoder further comprises:

a character information unit to receive character data and, in response, generate caption character data in a plural byte format;

a character code generator which uses a most significant bit of each byte of the caption character data as a flag indicative as to whether the character data is caption word data related to the video signal being broadcast or additional information having no relation to the video signal being broadcast, said character code generator replacing each most significant bit with a first value if the character data is the caption word data and replacing each most significant bit with a second value different from the first value if the character data is the additional data, and adding a parity bit to each byte, to generate a first data packet as a character code;

a control information input unit to receive control information for caption control and generates caption control data in a plural bit format;

a control code generating section to divide the plural bits of the caption control data into an upper plural number of bits and a lower plural number of bits, to create an upper byte by adding a first parity bit, control code discriminating bits, and the flag to the upper plural number of bits, to create a lower byte by adding second and third parity bits, control code discriminating bits and the flag to the lower plural number of bits, and to add additional respective parity bits to each of said upper and lower bytes, to generate a second data packet indicative of a control code; and

a modulating section to modulate the character and control codes by digital modulation, to generate the caption signal.

20. A broadcasting system as claimed in claim 19, further comprising:

an audio processor to process an audio signal; and

a television signal modulator to frequency modulate the processed audio signal, amplitude modulate the processed video signal encoded with the caption signal, frequency multiplex and frequency transmit the amplitude modulated audio signal and the frequency modulated video signal encoded with the caption signal, to generate a high frequency signal.

21. A broadcasting system as claimed in claim 19, further comprising:

a transmission unit to transmit the television signal; and

a receiver to receive the television signal, said receiver including

a video signal processing unit to luminance and chrominance process the television signal received from said transmission unit,

a data extractor to convert the television signal received from said transmission unit into a digital signal,

a sync separator to separate vertical and horizontal sync signals from the television signal received from said transmission unit,

a storage device to store character information of a bit-map type,

a caption processing unit to extract the caption signal from the digital signal based upon the output from said sync separator, to discriminate the caption signal as being one of the character code and the control code based on designated values of selected bits of the character code and the control code, to read out the character information from the storage device based upon the discrimination of the character code, to alter an appearance of a caption on a display based upon the discrimination of the control code, and

a mixer to mix the luminance and chrominance processed television signal with the output of said caption processing unit.

22. A broadcasting system as claimed in claim 19, wherein the caption signal includes a bit clock signal beginning at a first point apart from a center point of a falling edge of a horizontal sync signal by a first predetermined amount if a phase of a chrominance subcarrier of a corresponding scanning line is 0 degrees, and beginning at a second point apart from the center point of a falling edge of the horizontal sync signal by a second predetermined amount if the phase of a chrominance subcarrier of the corresponding scanning line is 180 degrees, and a word start signal indicative of a start of one of the character code and the control code.

23. A broadcasting system as claimed in claim 21, wherein the caption signal includes a bit clock signal beginning at a first point apart from a center point of a falling edge of a horizontal sync signal by a first predetermined amount if a phase of a chrominance subcarrier of a corresponding scanning line is 0 degrees, and beginning at a second point apart from the center point of a falling edge of the horizontal sync signal by a second predetermined amount if the phase of a chrominance subcarrier of the corresponding scanning line is 180 degrees, and a word start signal indicative of a start of one of the character code and the control code.

24. A broadcasting system as claimed in claim 19, wherein each of the character code and the control code includes a parity in a unit of a word, the flag, and a code value, wherein values of particular bits of each of the character code and the control code are indicative as to whether a particular data packet is the character code or the control code.

25. A broadcasting system as claimed in claim 19, wherein ones of the lower plural number of bits designate a plurality of functions for displaying the character information, and ones of the upper plural number of bits designate a plurality of subfunctions for the functions for displaying the character information.

26. A broadcasting system as claimed in claim 19, wherein an odd field channel of the video signal is used to transmit the character data of a first language and an even field channel of the video signal is used to transmit the character data of a second language different from the first language.

27. A broadcasting system as claimed in claim 26, wherein the character code is transmitted through both the odd and even field channels of the video signal.