KR100218099B1 - Subtitle signal format of viewer-selectable caption broadcasting - Google Patents

Abstract

A caption signal format of a viewer selectable caption broadcasting in which a caption signal is transmitted on one scanning line of each field of a television signal, wherein the caption signal maintains a level between at least 50 ± 5 IRE and 90 ± 5 IRE, A bit clock synchronizing signal of a sine wave signal of 6 to 7 cycles having a frequency obtained by dividing the color subcarrier of the signal by four, a word start signal of a sinusoidal wave of one cycle having a frequency of the bit clock synchronizing signal, And a digital modulated data signal composed of 16 bits or more and 18 bits or less to divide the frequency of color subcarriers by forming a caption signal so that phase synchronization can be performed to reduce the cost of the receiving apparatus. Format.

Description

Subtitle signal format of viewer-selectable caption broadcasting

The present invention relates to a caption signal format of a caption broadcasting, and more particularly, it relates to a caption signal format of a caption signal in a viewer-select type caption broadcasting which receives a caption and a control code in a television signal, Format.

In the television broadcasting, the closed caption broadcasting system is a system in which a caption signal is superimposed on an active section of a television signal so that an open caption system that displays urgent news or notifications by selection of a viewer without selecting a viewer, That is, a closed caption system in which a caption signal is transmitted in a vertical blanking interval, and then the television screen and the contents of the dialogue can be viewed as subtitles by a viewer's choice.

Closed Caption closed caption broadcasting has been implemented in the United States since 1978 for the hearing impaired who can not know the contents of the screen without sign language.

U.S. Patent No. 5,294,982, published March 1994, discloses a closed captioning method of roman and syllabic characters. In particular, the captioning method of Korean is described in great detail. In the invention of the US patent, in order to broadcast Korean in a closed caption system, an English character corresponding to each phoneme is divided into a first, a second, and a last phoneme, and the receiver decodes the ASCII code, , The neutral character and the last character are mapped to display a Korean character.

Since the conventional Hangul closed caption system uses at least 2 to 3 bytes to represent Korean characters, the transmission speed and the display speed are slow, and the position of one character must be found by combining 3 to 4 bytes in the decoding process. There is a problem that the processing is complicated. The complexity of the decoding process increases the cost of the decoder. This causes a problem that increases the cost of the decoder that millions of viewers have to pay in comparison with the encoder required only in the broadcasting station.

In addition, simultaneous display of Chinese characters, Korean, and Japanese, and simultaneous display of English, Russian, and Greek are impossible, and special symbols can not be displayed.

Further, since the control code is required in displaying the dialog information in the middle of displaying the additional information and again displaying the additional information, there is no independence between the dialog information and the additional information, and a control system for distinguishing the display modes of the dialog information If the display mode control code is not received at the time when the receiving apparatus starts to operate, it is impossible to display the metabolism information until the next control code is received.

In the above-mentioned invention, since the television broadcasting environment of the United States, that is, the flat ground is developed based on a geographical environment, it is pointed out that the reception quality of the receiving apparatus is poor and the quality of the subtitle display is deteriorated in the geographical environment of Korea where the mountain is more than 70% .

It is an object of the present invention to provide a caption signal format of a viewer selectable caption broadcasting which can effectively perform Korean caption broadcasting.

In order to achieve the above-mentioned object, a caption signal format of the present invention is a caption signal format of a viewer-type caption broadcasting in which caption signals are transmitted on one scanning line of every field of a television signal, A bit clock synchronizing signal of a sine wave signal of 6 to 7 periods having a frequency that is maintained at a level of 90 +/- 5 IRE from the IRE and frequency of the color subcarrier of the television signal divided by 4; A word start signal having a sinusoidal wave of one period having a frequency obtained by frequency-dividing the bit clock synchronizing signal; And a digitally modulated data signal composed of at least 16 bits and no more than 18 bits.

FIG. 1 is a block diagram showing the configuration of a television broadcasting system for viewer selectable type caption broadcasting according to the present invention,

FIG. 2 is a block diagram showing a configuration of a television receiver for receiving viewer-selectable caption broadcasting according to the present invention,

FIG. 3 is a signal configuration diagram showing a configuration of a caption signal according to the present invention,

FIG. 4 is a diagram showing a data packet structure of 18-bit subtitle data according to the present invention,

FIG. 5 is a diagram showing a packet structure of 16-bit subtitle data according to the present invention,

FIG. 6 is a diagram showing a packet structure of 17-bit subtitle data according to the present invention.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

Fig. 1 shows the structure of a television broadcasting apparatus having a viewer selectable caption broadcasting function. The audio signal inputted through the microphone 10 is mixed and amplified in the audio signal processing unit 30 and transmitted to the television signal modulating unit 50. [ The video signal input through the video camera 20 is amplified in the video signal processing unit 40, edited, and transmitted to the television signal modulating unit 50. The television signal modulating unit 50 FM-modulates the transmitted voice signal, AM-modulates the video signal in the residual sideband manner, frequency-multiplexes the AM modulated signal and the FM modulated signal, And the high-frequency output unit 60 amplifies the high-frequency signal and transmits the television signal to the air through the antenna.

In the subtitle encoding unit 70, the supplementary information such as the metabolic information related to the television screen or the urgent news or the delivery item is input through the character information input unit 71. [ And various control information for caption control are input through the control signal input unit 72. [ The character information input unit 71 includes a keyboard for inputting characters such as Hangul, English, Kanji, and Japanese, and special characters, and outputs the inputted character information as a 2-byte Hangul complete code (KSC5901). The control information input unit 72 includes keypads such as a mode selection key and a function selector, and outputs the input control information in a 7-bit binary code.

The character code generating unit 73 uses the MSB of each byte of the inputted 2-byte character code as the metadata subtitle / additional information flag, substitutes the MSB into '0' in case of additional information, adds a parity bit to each byte Thereby generating a data packet of a total of 18-bit character codes.

The control code generating unit 74 divides the input 7-bit binary number into upper 3 bits, upper 4 bits, parity bit for the upper 4 bits, control code identification bit for 2 bits, and metablock / addition flag to generate the upper byte A first parity bit, a second parity bit, a 2-bit control code identification bit, and a subtitle / additional information flag for the lower 3 bits are added to generate the lower byte. A parity bit is added to each generated byte to generate a data packet of a total of 18 bits of control code. The details of the data packet will be described later.

The data packet modulating section 75 modulates the data packet generated in the character code generating section 73 or the control code generating section 74 by a digital modulation method.

The sync counter unit 76 receives the sync signal supplied from the video signal processing unit 40 and is reset by the vertical sync signal and counts the horizontal sync signal to select the 262nd scan line in the odd field and the 525nd scan line in the even field, And counts the number of scanning lines. The window signal generator 77 receives the count value of the synchronization counter 76 and generates a window signal. The window signal is a driving signal for switching the switching means 78 to superimpose a caption signal on a predetermined specific line, e.g., 262 and 525 scanning lines, of the video signal output from the video signal processing unit 40.

Fig. 2 shows a configuration of a television receiver for receiving viewer selectable caption broadcasting.

The tuner unit 110 demodulates the television signal of the selected channel among the high-frequency signals received by the antenna and outputs a voice signal and a video signal. The audio signal is transmitted to the audio signal processing unit 120, and is then assimilated and amplified and output as a voice through the speaker 130. The video signal is transmitted to the video signal processing unit 140, subjected to luminance and color processing, and then output as an RGB signal.

The RGB signal is transmitted to the display driver 160 via the mixer 150 and the display driver 160 drives the CRT 170 in response to the RGB signal transmitted from the display driver 160 to display the television screen on the screen.

The subtitle decoding unit 200 converts the video signal through the A / D converter 210 and transmits the digital signal to the subtitle processing unit 230. The sync separator 220 separates the sync signal from the video signal and transmits the vertical and horizontal sync signals to the caption processor 230.

The caption processing unit 230 generates a clock signal synchronized with the color burst signal of the video signal processing unit 140 to extract a caption data packet from the digital signal. Decodes the extracted data packet, controls the caption processing in response to the decoded control code, reads the character data from the font ROM 240 in response to the decoded character code, and stores the read character data in the display wrap 250. Converts the character data stored in the display RAM into an RGB signal, and transmits the RGB signal to the mixer 150. The caption processing unit 230 exchanges control data with the system control unit 180 of the set. The system control unit 180 transmits a caption related command input through the command input unit 19 to the caption processing unit 180 and controls the system in response to the control data transmitted from the caption processing unit 180. [

The detailed configuration of the caption information to be used in the above-mentioned caption broadcasting transmission / reception system is as follows.

In Korea, M-NTSC TV signals of 525 lines and 60 fields / second are used as broadcast signals, and the vertical blanking period is defined from the scanning line 10 to the scanning line 20.

There are no standards established by the Ministry of Information and Communication for the use of signals in the vertical blanking period. For reference, there are ITU-R Rec 473-2 and FCC Report and Order 83-120 in the United States.

The caption signal can use any one of the scanning lines 10 to 20 in the vertical blanking period or the odd field or the even field or the scanning line 262 of the scanning line 21 for transmission of the caption data. You can also use more than one for other purposes, such as increasing data transfer. However, since all field data transmission is not meaningful in closed caption broadcasting, it is not considered.

The transmission bit rate of the subtitle data should be 447443.125 bps ± 125 bps and the maximum value of the long-term change rate should be within ± 196 (0.0125 bps), and the caption data signal must be used only for the transmission of the color TV signal, and the transmission bit rate shall be the color subcarrier frequency fsc ± 10 Hz) and must be frequency synchronized to the color burst. The color subcarrier preferably has a continuous phase between the scanning line and the scanning line. If the phase of the color subcarrier is discontinuous for screen editing or the like, the color burst of the corresponding scanning line must be phase-synchronized at least.

The data modulation method is represented by a sinusoidal wave of one period having a phase of 0 degrees and a frequency of fsc / 8 (447.443 kHz) corresponding to the logical value '1', and a phase corresponding to the logical value '0' (Binary Phase Shift Keying), NRZ (Non-Return-to-Zero) or PRK (Phase Reversal Keying), which is expressed by a sinusoidal wave having a frequency of fsc / 8 (447.443 kHz) Method. The maximum range of phase jitter is ± 10 degrees. The optimal signal waveform will be defined in the future as it may vary depending on the frequency spectrum characteristics of the TV channel. However, since the BPSK waveform may undergo severe distortion at a portion where a logical value transition occurs due to a fundamental band-limited frequency, a phase-corrected waveform may be used for broadcasting after passing through a secondary Butterworth filter having a cutoff frequency of 3.5 MHz . The impulse response of the Butterworth filter used is:

The test method and rationale are defined in Item I-7 (TV R / C) Item 4 (Multiplexed Broadcasting) term (overlapping position of data lines and amplitude of character signal) among the radio station inspection items. The waveform of the caption signal is not NRZ Since it is a pure sinusoidal wave, it is not necessary to apply the above criteria. However, in order to broaden the receivable area, the level of the sinusoidal wave should be kept within the range of 50 ± 5 IRE to 90 ± 5 IRE. Although the maximum amplitude of the normal data signal is defined, the maximum value of the overshoot may be 5 IRE since it may include the overshoot due to the filter passband characteristics.

Referring to FIG. 3, the data line of the caption signal is composed of six cycles of a bit clock synchronizing signal 302, a word start signal 304, and an 18-bit data string 306.

The bit clock synchronizing signal 302 is a sinusoidal signal of six periods, which can be used by the subtitle decoding unit to extract the signal and read the bit period of 18-bit data. The frequency is fsc / 4 (894.886 kHz). When the phase of the color subcarrier of the scanning line is 0 degrees, the phase of the color subcarrier of the scanning line starts at a position separated by 9.5 mu s (34 cycles of the color burst) from the falling edge intermediate point OH of the horizontal synchronizing signal, At 180 degrees, it starts from a point 9.64㎲ (34.5 cycles of color burst) from the falling edge intermediate point (OH) of the horizontal synchronizing signal. Since this signal is frequency synchronized with the color burst of the corresponding line, the bit clock synchronizing signal can be extracted from the color burst.

The word start signal 304 serves to indicate the start of an 18-bit data packet as one period of a sinusoidal signal having fsc / 16 (223.72 kHz) and a phase of 180 degrees. The data sequence of the word start signal is 01, 001, 010, 011 It can be one.

The data signal 306 is composed of 18 bits, and the bit rate is fsc / 8 (447.443 kHz) and modulated in the BPSK scheme.

Referring to FIG. 4, the data packet is composed of three parts: a parity (p) in words, a subtitle / additional information flag (C / T), and a code value (c). D0 to D8 shall be called lower word, and D9 to D17 shall be called upper word.

D17 represents an even parity for D0 to D16. This parity bit is intended to detect errors on the transmission first. D7 and D16 are the subtitle / additional information flags, 0 for the subtitle subtitle, 1 for the additional information, and the values of D7 and D16 must match. This flag is used to maintain the word-based priority. D0 to D6 and D9 to D15 together represent the code value. Code values are interpreted as control codes if D5, D6, D14, D15 are mode 0, otherwise they are interpreted as character codes.

The data signal may be composed of 16 bits as shown in FIG. In the 16-bit configuration, a caption / text bit defined in the 18-bit format is configured as a control code, thereby reducing the number of bits by 2 bits. For example, the caption / text control code can be set to 7 in the LSB byte and A in the MSB byte.

As shown in FIG. 6, in the case of 17 bits, parity is used for the LSB and the MSB in the above-mentioned 18 bits, but this is a format in which 1 bit is reduced by integrating it into one parity bit.

When the digital modulation system is NRZ, the data signal has a frequency 32 times the horizontal frequency.

Therefore, in the present invention, by using a sinusoidal wave in which the format of the subtitle signal is digitally modulated by the BPSK method and the color subcarrier of the television signal is divided, the receiving state of the receiving apparatus can be improved, It is possible to reduce the reception sensitivity and the error rate of the caption signal in the region where the reception condition of the radio wave is in a bad condition, thereby improving the quality of the caption signal. In addition, since the subtitle signal is formed by dividing the color subcarrier, the stability of the signal by the phase synchronization of the color subcarrier and the phase synchronization circuit can be easily obtained, and the cost burden on the receiving apparatus can be reduced.

Claims (5)

A subtitle signal format of a viewer-selectable subtitle broadcast in which a subtitle signal is transmitted on one scanning line of each field of a television signal, characterized in that the subtitle signal is a sinusoidal signal obtained by dividing a color subcarrier of the television signal Bit clock synchronization signal; A word start signal having a predetermined frequency of the bit clock synchronizing signal; And a digitally modulated data signal composed of a predetermined bit, and the subtitle signal format of the viewer selectable subtitle broadcast. 2. The method of claim 1, wherein the modulation scheme of the data signal is one of Binary Phase Shift Keying (BPSK), Non-Return-to-Zero (NRZ), and Phase Reversal Keying (PRK) Caption signal format of caption broadcasting. The method according to claim 1, wherein the word start signal is one of a frequency of the bit clock synchronizing signal divided by two or four, and the data string is one of 01,001,010,011. [2] The method of claim 1, wherein the data signal has a frequency obtained by dividing the frequency of the bit clock synchronizing signal by two when NRZ or BPSK modulation is performed. 3. The caption signal format of viewer selectable caption broadcasting according to claim 1 or 2, wherein the data signal has a frequency 32 times the horizontal frequency in NRZ modulation.