JP2627365B2 - Closed caption broadcast receiver - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for receiving closed caption broadcasting in the United States, and more particularly to an improvement in a method of displaying characters on a television screen by closed caption broadcasting.

[0002]

2. Description of the Related Art For those who are deaf,
Display conversations and announcements as subtitles on the TV screen
Closed Caption Broadcast (CLOSED CAP)
TION) is taking place in the United States. This is Japan
It is similar to teletext multiplexing, where data is sent to a video signal.
Is transmitted while being superimposed on the vertical retrace period. Of the data
Transmission is by code and when displaying characters, the receiver
Prepare a character generator (character generator) inside
Prepare the letters. This allows the broadcaster to code
It is possible to display instantly just by sending (sign)
You. There are two types of display modes.
Mode (TEXT MODE) and caption mode
(CAPTION MODE). Text mode
In the center of the TV screen, a maximum of
Can be displayed.
Upper and lower sides of the box, ie, between rows 1 to 4 and 12 to 1
Display is possible only for five columns. Closed caption
The broadcast data is in the vertical blanking period 21H (H is
(Horizontal scanning period).
As shown in FIG. The 21H duplicate shown in FIG.
The combined signal is 3.58 MH _ZColor burst signal and 5
03KH_ZRun-in clock and caption data
And the caption data is shown in FIG.
As shown in (b), a 3-bit start bit and a 7-bit data
Data, parity bit of the data, 7-bit data,
And a parity bit of the data. 503
KH_ZRun-in clock is the same as the caption data.
And extract caption data based on this.
8-bit data including the parity bit shown in FIG.
(1 byte) as one unit, in addition to the above-mentioned character code,
Command to determine the position (row and column) and color of the character
(Instruction) is transmitted.

[0003] As a receiver of this closed caption broadcast, one as shown in FIG. 3 is conceivable. The television broadcast signal on which the data of the closed caption broadcast is superimposed is received by the antenna (101) of FIG. 3, is tuned by the tuner (102), and is then amplified by the IF (intermediate frequency) amplifier circuit (103). It is detected. The detected video signal is processed by a Y / C (luminance / chroma) processing circuit (104), and an RGB primary color signal is applied to an RGB switching circuit (105).

[0004] From the video signal from the IF amplifier circuit (103), only the caption data is extracted by the extraction circuit (106) and applied to the decode microcomputer (107). The decoding microcomputer (107) performs parity check, display determination, decoding, and the like of caption data. The decoded caption data is applied to a character generator (108) and processed so that a desired character can be displayed at a desired position. Then, according to the processing, the R, G, B primary color signals are generated from the character generator (108), and the R, G, B switching circuit (1) is output via the output control circuit (109).
05), and caption characters are projected on the original television screen.

[0005] The decoding microcomputer (107) detects that the incoming caption data is abnormal multiple times.
Is determined, a command to inhibit caption display is applied to the character generator (108). Then, control for inhibiting generation of an output signal is performed from the character generator (108) to the output control circuit (109).

[0006]

However, when the reproduction video signal from the video equipment (111) such as a VTR is displayed on a television screen by switching the switch (110) using the apparatus shown in FIG. Is performed, since the caption data is not superimposed on the vertical synchronization signal (pseudo vertical synchronization signal), the decoding of the data is not performed.
There has been a problem that the output control circuit (109) is disabled and no caption characters are left on the screen.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has been made so as to decode caption data multiplexed into a television signal and display character information on a television screen. In a closed caption broadcast receiving apparatus, a display determining means for determining whether or not caption data is abnormal continuously for a predetermined period, and for prohibiting screen display when abnormal, and for setting a television screen to a special reproduction state. Prohibition means for prohibiting the operation of the display determination means in response to a special image display command from a video device is provided, and caption data immediately before the command is continuously displayed on a television screen in response to the special image display command. It is characterized by the following.

[0008]

According to the present invention, it is determined whether or not the caption data is abnormal continuously. If the caption data is abnormal, display off operation of the display determining means for automatically turning off the screen display is performed by an external device. It is prohibited according to the control signal. Further, according to the present invention, a regular character code which becomes a transparent space on the television screen is preset in the shift register for latching the caption data, and the character code is continuously supplied to the subsequent circuit, and the display determining means is displayed. In addition to the determination of the ON state, the write operation to the new RAM is substantially prohibited by utilizing the characteristics of the address counter of the RAM. Therefore, the character code immediately before is stored in the RAM and is displayed on the television screen. Furthermore, according to the present invention,
The display determination means determines that the data is normal data to be displayed, and the decoder presets data determined to be meaningless data in the shift register.

[0009]

FIG. 1 is a circuit diagram showing an embodiment of the present invention.
Description will be given according to FIG. The television broadcast signal on which the data of the closed caption broadcast is superimposed is received by the antenna (1) of FIG. 1, is tuned by the tuner (2), and then amplified and processed by the IF (intermediate frequency) amplifier circuit (3). It is detected. The detected video signal is Y / C (luminance / chroma)
The processing is performed by the processing circuit (4). Then, horizontal and vertical synchronizing signals are applied to the deflection circuit (5) from the Y / C processing circuit (4) to drive the deflection coil of the cathode ray tube (6).
The primary color signals of G and B are supplied to the cathode ray tube (6) via the RGB switching circuit (7).

The video signal from the IF amplifier circuit (3) is applied to a separation circuit (8), where a horizontal synchronization signal and a vertical synchronization signal are separated and applied to a PLL circuit (9) and a counter (10). At the same time, a video signal is applied to the slice circuit (11). The PLL circuit (9) locks to the horizontal synchronizing signal, and a signal of a frequency f _H (horizontal synchronizing signal frequency) is applied to the counter (10) as a clock signal. The counter (10) is reset by the vertical synchronizing signal, generates a gate pulse for extracting the caption data of the 21H, and applies the gate pulse to the slice circuit (11). The slice circuit (11) converts the caption data of the 21H in the video signal from the separation circuit (8) to 50.
Sliced extracted based on the run in clock of 3KH _Z, applied serially 2 decode microcomputer (12) the data of 2 bytes, such as (b). In the decoding microcomputer (12), the incoming data is first input to the input means (30).
After storing the data, the parity check of the data is performed by the parity check means (13), and the data for which the check result is normal is a command indicating whether the data is valid data or a character code by the determination means (14). A determination is made as to whether or not. Then, the data from the determining means (14) is decoded by the decoding means (15). The determination means (14) also determines whether or not display on the screen is to be prohibited. Display ON / OFF is determined according to the determination result.
The switching means (16) operates the decoding means (15) and performs an operation for inhibiting display. On the other hand, the decoding by the decoding means (15) is to demodulate the data into a code corresponding to a character generator ( 17 ) at the subsequent stage.
Data such as character type, character position (row and column), and character color are demodulated.

The demodulated data is supplied to a character generator ( 17 ).
Is temporarily fetched into the shift register (18), and when the fetched data is a character code, 15 columns × 32
It is applied to the RAM (19) having the address corresponding to the character, and if it is a command, it is further applied to the decoder (20) and decoded so that the character generator ( 17 ) can be controlled.

The output signal of the decode microcomputer (12) is
A combination of the command and the data is taken as a set into the shift register (18) in the character generator ( 17 ), the command is decoded by the decoder (20), and the decoded output is stored in the RAM (19). It controls a row address counter (21) and a digit address counter (22). Further, of the data taken into the shift register (18), the character code is applied to the RAM (19), and the address data is applied to the row address counter (21) and the digit address counter (22). Therefore, RAM (1
In 9), the designated character code is written at the designated position. On the other hand, horizontal and vertical synchronization pulses from the deflection circuit (5) are applied to the timing setting circuit (23),
A timing signal (readout signal) displayed at a position on a television screen defined by the standard is stored in a RAM.
(19). The character code read from the RAM (19) is serially stored in the character ROM.
(24), and the dot pattern of the corresponding character is read out serially. The read dot pattern is subjected to color adjustment and the like by an output control circuit (25) and then applied to an RGB switching circuit (7). The output control circuit (25) also performs an operation of inhibiting display.
Specifically, when the display ON / OFF switching means (16) is switched to display OFF, a command for inhibiting display is generated, and the decoder (20) is switched via the shift register (18).
And the display inhibit instruction is output by the output control circuit (25).
Is applied to Then, the output control circuit (25)
The GB switching circuit (7) switches so as to select the signal from the Y / C processing circuit (4), and nothing is displayed on the television screen. When displaying, the output control circuit (2
The switching signal is generated at the same time as the generation of the RGB signal from 5), and the RGB switching circuit (7) responds to the switching signal by the RGB signal from the output control circuit (25). Select
The switching circuit (26) issues a caption ON / OFF instruction and a text / caption mode switching instruction to the decode microcomputer (12). The first control terminal (2
7), a still image command (pause signal) from the VTR is applied, and the second control terminal (28) applies a direct command (when a caption character displayed on the television screen is desired to be left) from the viewer. Is done. The OR gate (29) applies the logical sum output of the control signals from the first and second control terminals (27) and (28) to the control terminal (31) of the decode microcomputer (12). The preset means (32)
Specific data is preset in the input means (30) in accordance with a control signal from the control terminal (31).

The decoding microcomputer (12) shown in FIG.
FIG. 5 is a detailed flowchart of the parity check (step 1) of FIG. The decoding operation will be described with reference to the flowcharts of FIGS. First, the caption data applied to the input means (30) in the decode microcomputer (12) is subjected to the parity check shown in FIG. 4 (step 1).
Is performed. Specifically, first, as shown in FIG. 5, it is determined in step 12 whether the control terminal (31) of the decode microcomputer (12) is "H" or "L".
At this time, if the output of the OR gate (29) in FIG. 1 is at the "L" level, the process proceeds to step 13 for determining whether or not the data is abnormal. If so, the process proceeds to step 14 for executing the adding operation of the error counter. Then, it is determined in step 15 whether or not the count value of the error counter has reached 45 times, and if it has reached 45 times, the display-off request flag is set in step 17. Then, the data with the flag set proceeds to step 2 in FIG. Further, in accordance with the setting of the flag, the error counter is cleared in step 18 to return to the initial state.

If it is determined in step 12 that the control terminal is at the "H" level or that the data is correct in step 13, the display off request flag is reset in step 16 and the data whose flag has been reset is Go to step 2 in FIG. Also in this case, the frame counter is set to step 1
Cleared at 8. The data to which the display-off request flag has been added in this way is applied to step 2. In step 2, the character data and the command are discriminated, and the command other than the character data is regarded as a command. For example, if a legitimate command has arrived correctly, it is first determined in step 3 whether the command matches the previous command. This is based on the fact that a command is sent twice according to the broadcasting standard. Then, it is determined in step 4 whether or not data is continuously missing 45 times, and it is determined that the data is ON. Then, it is determined in step 5 whether or not the command is present in the command list in the mode designated by the switching circuit (26) in FIG. If they do not match in steps 3 and 5, the process proceeds to step 10 to fetch new data, executes step 11, and repeats the same processing until the matching data arrives. If it is determined in step 5 that the command is valid, it is determined in step 6 whether or not a display-off request flag exists. If the command is correct, the flag is in the reset state, and the process proceeds to step 7 where the flag is decoded and output to the character generator in step 9.

Next, assuming that correct character data corresponding to the command has arrived, the process proceeds to step 2 in FIG. 4 with the display off request flag reset in the flowchart of FIG. Then, the process proceeds to step 6, wherein the determination is NO, and the processing is performed in the same manner as the command. The command thus generated and the character code corresponding to the command are applied to the shift register (18) in the character generator ( 17 ) of FIG. 1, and the address of the RAM (19) is designated by the command, and the designation is performed. The character code is written to the specified address.

Next, a case will be described in which caption data is lost 45 times or more consecutively and caption characters on a television screen are erased as in the past. In this case, FIG.
Since the output of the OR gate (29) should be at the “L” level, steps 12 to 13, 14, 15,
Proceeding to 17, the missing data for which the display-off request flag has been set proceeds to step 2 in FIG. Then, in response to the two arrivals of the missing data, the process proceeds to step 4, further proceeds to step 5,
It is determined that the command is invalid. Then, after waiting for 45 times of missing data, “YES” is determined in step 4 and the process proceeds to step 6. Then, YES is determined in the step 6, and a display off command is generated in a step 8 in accordance with the determination, and is output to a character generator in a step 9. The display off command is decoded by the decoder (20) via the shift register (18) in FIG. 1, and a display inhibit command is generated. The display inhibit command is applied to the output control circuit (25).

Therefore, the caption characters on the screen can be erased. Next, when playing back a VTR still image,
Alternatively, a case where a caption character is desired to be temporarily left on the screen and the output of the OR gate (29) in FIG. 1 becomes “H” will be described. At this time, FIG.
The process proceeds from step 12 to step 16 and proceeds to step 2 in FIG. In this case, the display-off request flag is the missing data reset, and the process proceeds to steps 3, 4, 6, and 7. If data that cannot be decoded by the decoding in step 7 is applied, no output is generated. Therefore, the RAM (19) of the character generator ( 17 ) in FIG. 1 is not rewritten at all. Since the reading of the RAM (19) is independently performed by the timing setting circuit (23), the immediately preceding caption character is continuously displayed on the television screen.

Next, another embodiment will be described. In this case, when the output of the OR gate (29) in FIG. 1 becomes "H", the input means (30) is caused to preset a special command by the preset means (32). The special command is a command which becomes a transparent space for the character generator ( 17 ) in FIG. This case will be described with reference to FIGS. 4 and 5. First, in FIG. 5, the process proceeds to steps 12, 13, and 16, and further proceeds to steps 2, 3, 4, 5, 6, 7, and 9 in FIG. And FIG.
A transparent space is written in a certain column of a certain row of the RAM (19). Then, the input circuit (30) is read again and the same processing is performed, and then the next digit of the transparent space becomes a transparent space. This is because the digit address counter (22) automatically increments in response to the arrival of a command. When this process is repeated until the last digit of the same line is reached, a command to change the line does not arrive, so that a transparent space is repeatedly written at the same position. Therefore, RAM (1
The data of 9) retains the previous value as it is, and in this case, the previous caption character is displayed on the television screen.

Next, still another embodiment will be described. this is,
Instead of the special command described above, the data is normal, that is, the parity is correct but a meaningless command is input by the input means (3
This is a method of presetting to 0). In this case, FIG.
, The process proceeds to steps 12, 13, and 16, and further proceeds to steps 2, 3, 4, 5, and 10 in FIG. Then, it waits for the next executable command to arrive, but since only the above-mentioned meaningless command arrives, it has no effect on the character generator ( 17 ). Therefore, RA
The data of M (19) retains the previous value.

Therefore, also in this case, the immediately preceding caption character can be displayed on the television screen. FIG.
In the embodiment, the input means (30) and the preset means (32) are provided inside the decode microcomputer (12), but may be provided outside the decode microcomputer (12).

[0021]

As described above, according to the present invention, the VTR
Even when caption data does not arrive during reproduction of a still image, caption characters on the television screen can be left as they are. Also, it can be left in the same manner as desired by the viewer. Further, according to the present invention, the operation of the display determination means for automatically turning off the screen display operation is prohibited, so that the present invention can be implemented only by providing the control signal and the determination means, and the configuration is simple. It has the advantage that.
Further, according to the present invention, it can be carried out by presetting a specific command in the input means for latching caption data, so that it can be easily implemented.

[Brief description of the drawings]

FIG. 1 is a closed caption broadcast receiving apparatus of the present invention.

FIG. 2 is a waveform chart for explaining closed caption broadcasting.

FIG. 3 is a conventional closed caption broadcast receiving device.

FIG. 4 is a flowchart for explaining FIG. 1;

FIG. 5 is a flowchart for explaining FIG. 4;

[Explanation of symbols]

(11) Slice circuit (13) Parity check means (14) Judgment means (15) Decoding means (16) Display ON / OFF switching means ( 17 ) Character generator (24) Character ROM (29) OR gate

Claims (2)

(57) [Claims] 1. When reproducing a still image, the caption data is
In a closed caption broadcast receiver that decodes caption data multiplexed into a television signal from a video device that does not generate and displays character information on the TV screen, the caption data is abnormal for a predetermined period of time. Is determined, and if abnormal, caption data is
Display determining means for prohibiting display on a video screen, and still image display for causing the video device to reproduce a still image
The display determination means performs the prohibition operation in response to a command.
And inhibiting means for inhibiting the providing, the static on the television screen in response to the still image display instruction
A closed caption broadcast receiving device, wherein caption data at the time of a still image display command is kept displayed . 2. When reproducing a still image, the caption data
A caption multiplexed with a television signal in a closed caption broadcast receiving device that decodes caption data multiplexed into a television signal from a video device that does not generate the text and displays character information on a television screen. A sampling circuit for sampling data, a shift register for latching caption data from the sampling circuit, a decoder for decoding caption data from the shift register, and a RAM for storing a character code demodulated by the decoder
And the RAM according to a command demodulated by the decoder.
An address counter that specifies the address of a character, a character ROM that generates a dot pattern of characters corresponding to the character code read from the RAM , and caption data from the extraction circuit for a predetermined period.
It is continuously determined whether or not an error has occurred.
Prohibition of displaying caption data on TV screen
Display judging means for causing the video device to reproduce a still image
The display determination means performs the prohibition operation in response to a command.
And inhibiting means for inhibiting the providing, the static on the television screen in response to the still image display instruction
A closed caption broadcast receiving device, wherein caption data at the time of a still image display command is kept displayed .