JPH09289628A - Acquisition method and decoding apparatus for digital signal multiplexed with video signal - Google Patents

Abstract

(57) A method and a decoding device for obtaining a digital signal multiplexed with a video signal from digital video data generated based on the video signal. A receiving device for receiving a video signal, a video decoding device for converting the received video signal into digital video data, a storage device for storing the digital video data, and a central processing unit. The central processing unit has a sampling unit that extracts a caption signal from digital video data stored in a storage device, and a code analysis unit that analyzes the sampled data and generates a character code or a control code. The sampling unit sets the 21st pixel interval for each frame at a pixel interval substantially corresponding to the 1-bit width of the caption signal.
Digital video data of pixels forming a horizontal scanning line is extracted and binarized with a predetermined threshold value.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and a decoding device for acquiring character information such as a digital signal multiplexed with a video signal such as a television signal or a video signal, particularly a closed caption signal.

[0002]

2. Description of the Related Art As a broadcasting system for displaying subtitles by multiplexing character information on a television signal, there are, for example, closed captions broadcast in the United States and text broadcasts in Japan. In these broadcasting systems, character information including a sync signal and characters and / or control codes is multiplexed on a predetermined horizontal scanning line of a television signal.

Here, the closed caption is a broadcasting system in which characters synchronized with voice are displayed on a television screen, and conventionally, a dedicated LSI or a decoder unit is required to display the closed caption on a television receiver. there were. For example, “Nikkei Electronics 1991
No. 537 (Nikkei BP) issued September 30, 2013, introduces a chipset in which this decoder function is integrated into three chips. In addition, “Nikkei Electronics 1993
June 582, No. 582 (Nikkei BP) ", a microcomputer built-in type LSI that incorporates a caption display function into a TV receiver channel selection microcomputer, and a decoder function on the TV receiver printed wiring board. The added add-on type LSI is introduced. These chipsets and L
In SI, a caption signal (character information) multiplexed on an analog television signal is synchronously separated at the frequency of the caption signal by a dedicated synchronous separation circuit and decoded.

[0004]

By the way, conventionally,
In order to display an image obtained by an analog video signal such as a television signal or a video signal on a monitor connected to a digital information processing device such as a personal computer or a word processor, the received analog video signal is a YUV pixel unit of the monitor screen. Alternatively, a method of converting into RGB digital video data (hereinafter, simply referred to as digital video data) is known.

However, the conventional chipset or LSI for decoding the caption signal is for directly acquiring the caption signal by synchronously separating it from the analog video signal, and a method and apparatus for acquiring the caption signal from digital video data. Was not previously clear. Particularly in a personal computer, since the horizontal scanning frequency of the monitor display is different, the frequency of the caption signal also changes accordingly. For this reason, in the conventional method of directly separating the analog signal from the analog signal and directly obtaining the caption signal, or of converting the received analog video into YUV or RGB digital video data of one pixel unit of the monitor screen, At the same time, it may not be possible to acquire the caption signal.

The present invention has been made based on the above circumstances, and a method for obtaining a digital signal such as character information multiplexed on an analog video signal from digital video data generated based on the analog video signal, and An object of the present invention is to provide a decoding device so that a caption signal can be acquired at the same time as a video signal of television or video.

[0007]

In order to solve the above-mentioned problems, the present invention is a method for obtaining a digital signal multiplexed on a predetermined horizontal scanning line of a video signal, wherein the video signal is pixel by pixel. Of the multi-valued digital video data, and, for each frame, of the pixels forming the frame, the predetermined number of pixels forming the horizontal scanning line is used as a reference to set the bit width of the digital signal to 1 bit. An extraction process for extracting digital video data of pixels forming the horizontal scanning line at substantially corresponding pixel intervals, and a digital process for binarizing the extracted digital video data with a predetermined threshold value to obtain the digital signal. And a signal acquisition step.

Also, the decoding device of the present invention is a decoding device for a digital signal multiplexed on a predetermined horizontal scanning line of a video signal, the video signal being converted into multi-value digital video data in pixel units. A converting means for storing, for each frame, digital video data of pixels forming the horizontal scanning line among pixels forming the frame in a storage medium; and a predetermined pixel forming the horizontal scanning line. With reference to the extraction means for extracting the digital video data of the pixels stored in the storage means at a pixel interval substantially corresponding to the 1-bit width of the digital signal, and the digital video data extracted by the extraction means to a predetermined threshold. A digital signal acquisition unit that binarizes the value to acquire the digital signal, and decodes the digital signal acquired by the digital signal acquisition unit Characterized in that it comprises a coding means.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION A decoding device to which the first embodiment of the present invention is applied will be described below. The decoding device of the present embodiment is compatible with closed captions broadcast in the United States. As described above, the closed caption is a broadcasting system in which characters synchronized with voice are displayed on a television screen, and a caption signal is multiplexed as a luminance signal over the entire 21st horizontal scanning line of an NTSC television signal. There is. FIG. 5 shows an example of the waveform of the caption signal multiplexed as the luminance signal on the 21st horizontal scanning line.

The caption signal, as shown in FIG.
It consists of a clock run-in signal 504 of 7 cycles, a start code 505 and a data code 506 synchronized with the clock run-in signal. Clock run
The IN signal 504 is a synchronizing signal for decoding the data code, and its frequency is 503 kHz. The data code 506 is a 2-byte NRZ (non return t) in which a 1-bit parity code is assigned for each byte.
o zero) signal. As a data code, a character code to which two ASCII characters are assigned is sent, and a control code to which various commands (designation of character display position, color, typeface, etc.) are sent. There are cases where it comes. In order to distinguish between the control code and the character code, the ASCII code indicating the character is not assigned to the data of the first byte of the control code. The start code 505 is for specifying the start position of the data code 506, and is composed of a 2-bit logical value “0” and a 1-bit logical value “1” following the clock run-in signal. Become.

First, the hardware configuration of the decoding apparatus of this embodiment will be described with reference to FIG. FIG. 1 is a hardware configuration diagram of a decoding device to which this embodiment is applied.

As shown in FIG. 1, the hardware of the decoding device according to the present embodiment comprises a central processing unit 1 and a receiving device 2.
A main memory 3, an auxiliary storage device 4, a display device 5,
It comprises an NTSC decoding device 6 and a bus 7 for transmitting necessary information between the devices.

The receiver 2 receives an NTSC television signal or a video signal.

The NTSC decoding device 6 converts the television signal or the video signal received by the receiving device 2 into YUV digital image data and transfers this information to the main memory 3 or the auxiliary storage device 4. Further, the NTSC decoding device 6 has a register indicating whether or not one frame of digital video data of the display device 5 has been transferred to the main memory 3 or the auxiliary storage device 4, and stores one frame of digital video data. When the transfer to the main memory 3 or the auxiliary storage device 4 is completed, 1 is set in a predetermined bit (hereinafter referred to as a transfer end bit) of this register.

The main memory 3 stores a program that functions as a work area, defines a processing procedure of the central processing unit 1, and data to be processed by the central processing unit 1. The main memory 3 also stores digital video data transferred from the NTSC decoding device 6. For the main memory 3, for example, a random access memory or the like is used.

The auxiliary storage device 4 stores a program or the like for controlling the operation of the decoding device, and digital video data transferred from the NTSC decoding device 6.
As the auxiliary storage device 4, for example, a floppy disk, a hard disk, a memory card or the like is used.

The central processing unit 1 is mainly composed of a microprocessor, and according to a program previously stored in the main memory 3 or the auxiliary storage device 4, a digital image stored in the main memory 3 or the auxiliary storage device 4 is used. A caption signal is acquired from the data, decoded, and the decoding result is displayed on the display device 5, and a television image or a video image is displayed on the display device 5 based on the digital image data.

The display device 5 displays the television image, the video image, and the characters of the decoded caption signal according to the instruction of the central processing unit 1. For the display device 5, for example, a CRT, an EL display, a liquid crystal display or the like is used.

The input device 8 is for inputting a user command or information. The user can instruct activation and termination of the decoding device via the input device 8. Also, when the user inputs a threshold value described later, it can be performed via the input device 5. Input device 8
For example, a pointing device such as a keyboard or a mouse is used.

Next, the functional configuration of the central processing unit 1 shown in FIG. 1 will be described with reference to FIG. FIG. 2 is a functional block diagram of the central processing unit 1 shown in FIG.

As shown in FIG. 2, the central processing unit 1 has a control unit 21, a sampling unit 22, and a code analysis unit 23.
And a display control unit 24 and an error detection unit 25. These functional blocks include the main memory 3 or the auxiliary storage device 4.
It is realized by executing the program stored in.

The sampling section 22 is a 21st section in which a caption signal is superimposed from one frame of digital video data stored in the main memory 3 or the auxiliary storage device 4.
Get the data of horizontal scan line. Then, based on the luminance information, the data code of the caption signal is sampled from the acquired data.

The error detection unit 25 checks whether or not the data code of the caption signal sampled by the sampling unit 22 has an error. Code analysis unit 23
Analyzes the character code and the control code from the data code sampled by the sampling unit 22.

The display control unit 24 causes the display device 5 to display characters according to the character code and control code analyzed by the code analysis unit 23, and causes the display device 5 to display an image obtained from digital image data. Control unit 21
Controls the sampling unit 22, the code analysis unit 23, the error detection unit 25, and the display control unit 24.

Next, a processing procedure in each part of the central processing unit 1 shown in FIG. 2 will be described with reference to the drawings.

First, the processing procedure of the control unit 21 will be described with reference to FIG.
This will be described with reference to FIG.

FIG. 3 is a flow chart for explaining the processing procedure of the control unit 21. The processing procedure shown in FIG. 3 is started when a program stored in the main memory 3 or the auxiliary storage device 4 is executed by a user command input to the input device 8.

First, the control unit 21 activates the receiving device 2 to receive an NTSC television signal and / or a video signal (step 301). In the NTSC system,
Video is transmitted at a frame rate of 30 frames per second.

Next, the control unit 21 activates the NTSC decoding device 6 (step 302). This allows NT
The SC decoding device 6 converts the television signal and / or the video signal received by the receiving device 2 into YUV digital image data for each frame forming an image, and the main memory 3
Alternatively, it is transmitted to the auxiliary storage device 4. As a result, the main memory 3 or the auxiliary storage device 4 stores the digital video data sent from the NTSC decoding device 6.

FIG. 15 shows digital video data for one frame converted by the NTSC decoding device 6. In FIG. 15, the received television signal and video signal are YUV4:
An example when converted to 2: 2 digital video data is shown. Here, Y data 1601 and U data 160
2 and V data 1604 represent the first pixel forming the image on the screen. In addition, Y data 1603 and U data 16
02 and V data 1604 represent the next (second) pixel forming the image on the screen. That is, YUV 4: 2: 2
In the digital video data of, Y is assigned to each one pixel, and U and V are assigned to every two pixels.
In the following description, it is assumed that each of Y, U and V data is composed of 8 bits.

Next, the control unit 21 controls the NTSC decoding device 6 to output digital video data for one frame to the main memory 3.
Alternatively, it is determined whether the transfer to the auxiliary storage device 4 is completed (step 303). This judgment is made by judging whether or not 1 is set in the transfer end bit of the register of the NTSC decoding device 6. When 1 is not set in the transfer end bit, that is, when one frame of digital video data has not been transferred to the main memory 3 or the auxiliary storage device 4, one frame of digital video data is stored in the main memory 3. Alternatively, it is transferred to the auxiliary storage device 4 and waits until 1 is set in the transfer end bit. On the other hand, the transfer end bit is 1
Is set, that is, when one frame of digital video data has been transferred to the main memory 3 or the auxiliary storage device 4, the transfer end bit is cleared to 0 (step 304), and then the sampling unit 22 is activated (step 305). As a result, the sampling unit 22
Samples a data code of a caption signal from one frame of digital video data stored in the main memory 3 or the auxiliary storage device 4. The processing procedure of the sampling unit 22 will be described in detail later.

Next, the control unit 21 activates the code analysis unit 23 (step 306). As a result, the code analysis unit 23 analyzes the character code and the control code from the data code sampled by the sampling unit 22.
The processing procedure of the code analysis unit 23 will be described later.

Next, the control unit 21 activates the display control unit 24 (step 307). As a result, the display control unit 2
4 causes the display device 5 to display the character code analyzed by the code analysis unit 23 according to the control code. The processing procedure of the display control unit 24 will be described in detail later.

Next, the control unit 21 determines whether or not the end of the decoding device is instructed by the user command input to the input device 8 (step 308). When the end is instructed, the NTSC decoding device 6 is stopped (step 309), the receiving device 2 is stopped (step 310), the processing in the control unit 21 is ended, and the operation of the decoding device is ended. To do. On the other hand, if the end is not instructed, the process returns to step 303, and the processes of steps 303 to 308 are repeated for the television signal and / or the video signal of the next frame.

In this way, the caption signal superimposed on the television signal and the video signal of each frame that is sequentially received is decoded and characters are displayed until the user instructs the end of the operation of the decoding device.

Next, the processing procedure of the sampling section 22 will be described with reference to FIG. FIG. 4 is a flow chart for explaining the processing procedure in the sampling section. FIG.
The processing procedure indicated by is started by executing a program stored in the main memory 3 or the auxiliary storage device 4 based on a command from the control unit 21.

First of all, the sampling section 22 includes the main memory 3
Alternatively, by designating an address where the digital video data of the 21st horizontal scanning line of the auxiliary storage device 4 is stored, one frame of digital video data 1600 as shown in FIG.
17 to obtain digital video data 1800 of the 21st horizontal scanning line as shown in FIG. 17 (step 401).

Next, as shown in FIG. 18, the sampling section 22 acquires luminance (Y) data 1900 of each pixel forming the 21st horizontal scanning line from the acquired digital video data of the 21st horizontal scanning line. , In the array D provided in the main memory 3 or the auxiliary storage device 4 (step 40).
2).

Next, the sampling section 22 sets a threshold value S for dividing the Y data of each pixel stored in the array D into "0" or "1" to a predetermined value (step 403). . The threshold value S is preferably an intermediate value between the maximum luminance value and the minimum luminance value of the Y data. In the present embodiment, since the Y data is composed of 8 bits (256 gradations), the threshold value S is set to 128 as shown in FIG.

The sampling section 22 sets a sampling interval T for sampling the Y data of each pixel stored in the array D to a predetermined interval. As shown in FIG. 5, this interval is set to a pixel interval substantially corresponding to the bit width (wavelength) of the caption signal (step 404). As mentioned above, the caption signal is the second
It is multiplexed as a luminance signal over one horizontal scanning line.
Therefore, the pixel interval substantially corresponding to the bit width (wavelength) of the caption signal can be obtained by dividing the number of pixels per horizontal scanning line by the total number of bits (26 bits) of the caption signal. For example, when the number of pixels per horizontal scanning line is 320, the pixel interval corresponding to the bit width of the caption signal is 12 pixels. When the number of pixels per horizontal scanning line is 640,
The pixel interval corresponding to the bit width of the caption signal is 2
There are 4 pixels.

Next, the sampling unit 22 uses the main memory 3
Alternatively, the arrays B [0] and B [1] for storing 1-byte character data provided in the auxiliary storage device 4 are initialized to 0 (step 405), and then the Y data from the array D is sampled. Position (i) is set to 0 (step 406). Thus, the Y data is sampled from the first pixel forming the 21st horizontal scanning line.

Next, the sampling section 22 detects a start code that specifies the start position of the data code of the caption signal.

First, 3 with reference to the sampling position i
Array Y of Y data of one pixel at sampling interval T
Sampling from That is, of the pixels forming the 21st horizontal scanning line, the Y data D [i] of the i-th pixel
, Y data D [i + T] of the i + Tth pixel, and i +
The Y data D [i + 2T] of the 2Tth pixel is arranged in the array D
Sampling from Then, Y data D [i], D [i + T], D [i + 2 of the three sampled pixels are obtained.
T] is divided into “0” or “1” by the threshold value S set in step 403, and D [i], D [i + T], D [i
It is determined whether + 2T] is in the order of "0", "0", "1" (step 407).

As shown in FIG. 5, the start code is composed of 3 bits having logical values "0", "0" and "1". Therefore, D [i], D [i + T], D [i + 2
The result of dividing T] by the threshold value (S) is “0”,
In the case of “0” and “1”, it can be determined that the sampled Y data of the three pixels represent the start code. In this case, the process proceeds to step 409.

On the other hand, D [i], D [i + T], D [i +
2T] is distributed by the threshold value (S), and the result is “0”,
If it is not "0" or "1", it can be determined that the Y data of the three sampled pixels does not represent the start code. In this case, the value of the sampling position i is incremented by 1 (step 408), and the step 407 is executed.
Return to In this way, the results obtained by distributing the sampled Y data D [i], D [i + T], and D [i + 2T] of the three pixels by the threshold value (S) are “0”, “0”,
The sampling position i is shifted one by one until it becomes “1”.

In step 409, from the Y data D [i] of the pixel forming the first bit of the start code,
Set the Y data of the pixel located after 7T / 2 sampling interval (or the Y data D [i + 2T] of the pixel forming the last bit of the start code to the pixel located after 3T / 2 sampling interval) to the sampling position i (Step 409). That is, i = i + 3T + T /
Set to 2. As a result, by sampling the Y data of the pixel at every sampling interval T based on the sampling position i (= i + 3T + T / 2) set in step 409, the portion corresponding to the peak or valley of the data code shown in FIG. Y data of the pixel located at is acquired.

Next, the sampling section 22 outputs a 2-byte data code to the array B [j] (where j is 1 or 2).
To be stored.

First, the Y of the pixels that make up the data code
The value j for determining the data storage destination is set to 0 (step 410). When j = 0, the Y data is stored in the array B [0], and when j = 1, the Y data is stored in the array B [1]. Next, Y stored in the array B [j]
The value k for counting the number of data is set to 0 (step 411).

Next, the Y data D [i] of the pixel at the sampling position i set in step 409 is sampled from the array D, and the threshold value S set in step 403 is set.
Is assigned to "0" or "1" (step 413).
When the result of distributing D [i] by the threshold value S is "1", "1" is stored in the most significant bit of the array B [j] (step 414) and then the process proceeds to step 415. On the other hand, when the result of distributing D [i] by the threshold value S is “0”, each bit of the array B [j] becomes 0 in step 405.
Since it has been initialized to 0, the process proceeds to step 415 without storing “0” in the most significant bit of the array B [j].

In step 415, since the Y data of the pixel located after the sampling interval T of the Y data of the pixel sampled in step 413 is sampled from the array D, the sampling position i is set to i = i + T, and then step 416. Move to.

In step 416, it is determined whether k is smaller than 8. Array k if k is less than 8
This means that 8-bit data is not stored in [j], so k is incremented by 1 (step 417), and array B [j] is shifted right by 1 bit (step 41).
2) and returns to step 413.

On the other hand, when k is 8, 8 is added to the array B [j].
Since this means that the data for one bit has been stored, the process proceeds to step 418, and it is determined whether j is 0 or not.
If j is 0, the 8-bit data stored in the array B [j] is the first byte of the data code, so j is incremented by 1 (step 419), and step 41
Return to 1. When j is 1, the 8-bit data stored in the array B [j] is the second byte data of the data code, and thus this flow is ended.

In step 406, the sampling position i is set to 0 so that the Y data of the first pixel forming the 21st horizontal scanning line is sampled. However, the sampling position i may be set near the predicted start position of the start code. As a result, the start code can be detected at high speed.

Further, in step 407, Y data of three pixels are sampled at sampling intervals T with reference to the sampling position i, and these Y data are "0" or "1" at the threshold value S. I examined the results of sorting. However, the Y data of the pixels located in the vicinity of each sampled pixel may also be sampled at the same time, and the result obtained by dividing the Y data by “0” or “1” by the threshold value S may be examined. For example, D [i-1], D [i], D
The result of dividing [i + 1] by the threshold value S is “0”,
"0", "0", D [i + T-1], D [i + T], D
The result of dividing [i + 1] by the threshold value S is “0”,
"0", "0", and D [i + 2T-1], D [i
It may be determined whether or not the result of sorting + 2T] and D [i + 2T + 1] by the threshold value S is "1", "1", "1". By doing so, the start code can be detected more accurately.

Next, the processing procedure of the code analysis unit 23 will be described with reference to FIG. FIG. 6 is a flowchart for explaining the processing procedure in the code analysis unit. It should be noted that the processing procedure shown in FIG.
It is started by executing a program stored in or the auxiliary storage device 4.

First, the code analysis unit 23 sets j to 0 (step 601) and sets the data code stored in the array B [j] of the main memory 3 or the auxiliary storage device 4 according to the flow shown in FIG. It is acquired (step 602). Here, since j = 0, the array [0] in which the data of the first byte of the data code is stored is acquired.

Next, the code analysis unit 23 uses the error detection unit 2
5 is activated (step 603). Accordingly, the error detection unit 25 performs a parity check on the error of the data stored in the array B [j]. Then, when an error is detected, "1" is assigned to a flag (hereinafter, referred to as an error detection flag E) indicating whether or not the error is detected, and when no error is detected, the error detection flag E is set. Substitute "0" for.
The processing contents of the error detection unit 25 will be described later in detail.

Next, the code analysis unit 23 determines whether or not an error has been detected by determining whether or not "1" is assigned to the error detection flag E (step 604). When "0" is substituted in the error detection flag E, that is, when there is no error, the data stored in the array B [j] is right-shifted, and then the most significant bit is set to "0". Then, a character code or control code is generated according to the closed caption standard (step 6).
05). The method of generating the character code and the control code is the same as the method used in the conventional closed caption decoding device. Then, step 605
After the processing in (3) is completed, the process proceeds to step 606.

On the other hand, if "1" is assigned to the error detection flag E, that is, if there is an error, the data stored in the array B [j] is replaced with a special character code (step 614). ). Here, the special characters are
For example, it is a figure or symbol that is visually easy to understand, such as a black square. The code analysis unit 23
This special character code is stored in the non-display memory (step 610). Here, the non-display memory is the main memory 3
Alternatively, it means an area provided in the auxiliary storage device 4. Next, after the processing in step 610 is completed, the process proceeds to step 611.

In step 606, it is determined whether the code generated in step 605 is an ASCII code indicating a character (step 606). As described above, in closed captioning, in order to distinguish whether the data code is a character code or a control code, the ASCII code indicating a character can be assigned to the first byte of the control code. Not not. Therefore, step 606
As a result of the judgment in step 3, if it is not an ASCII code indicating a character, the process shifts to step 613 to judge whether or not j = 0. If j = 0, the code generated in step 605 is the first byte of data stored in the array B [0], so the data stored in the arrays B [0] and B [1] is the control code. It turns out that In this case, j is set to 1 (step 612) and the process returns to step 602. On the other hand, when j = 0 is not satisfied, that is, when j = 1, the code generated in step 605 is the second byte of data stored in the array B [1], and therefore the code is invalid data. I can judge. In this case, step 61
Then, the code is replaced with a special character code.

If the result of determination in step 606 is that the code is an ASCII code indicating a character, the flow shifts to step 607 to determine whether j = 1. When j = 1 is not satisfied, that is, when j = 0, the code generated in step 605 is the first byte of data stored in the array B [0], and therefore the arrays B [0] and B [1] are stored. It can be seen that the stored data is a character code. in this case,
Control goes to step 609. On the other hand, when j = 1, since the code generated in step 605 is the second byte of data stored in the array B [1], it is merely determined whether the code is an ASCII code indicating a character. Then
It cannot be determined whether the code is a character code or a control code. In this case, the process proceeds to step 608.

In step 608, it is determined whether the first byte of data stored in the array B [0] is an ASCII code indicating a character (step 608). If the data of the first byte is an ASCII code indicating a character, it is known that the data of the second byte is a character code. Therefore, the process proceeds to step 609, and the data at the first byte is an ASCII code indicating a character. If not, it is found that the data in the first byte and the data in the second byte are the control code, and the process proceeds to step 615.

In step 609, whether the character code generated in step 605 is valid, that is, step 6
It is determined whether a character is assigned to the character code generated in 05. If the character code is valid, this character code is stored in the non-display memory (step 61).
0). On the other hand, if the character code is not valid, step 6
Then, the processing shifts to 14, the character code is replaced with a special character code, and the special character code is stored in the non-display memory (step 610). Then, after the processing in step 610 is completed, the process proceeds to step 611.

In step 615, it is determined whether the control code generated in step 605 is valid, that is, step 6
It is determined whether or not a command is assigned to the control code generated in 05. If the control code is valid,
The command assigned to this control code is processed (step 616) and the process proceeds to step 611. On the other hand, if the control code is not valid, the control code is ignored (step 617) and the process proceeds to step 611.

In step 611, it is determined whether j = 1. If j is not 1, it means that the code analysis of the second byte of data stored in the array B [1] is not completed yet, so j is incremented by 1 (step 612) and the process returns to step 602. . On the other hand, if j = 1, it means that the code analysis of the data of the second byte stored in the array B [1] is completed, and this flow is ended.

The data code of the caption signal superposed on the television signal and the video signal of one frame received by the above processing can be decoded.

Next, the processing procedure of the error detector 25 will be described with reference to FIG. FIG. 7 is a flow chart for explaining the processing procedure in the error detection unit. The processing procedure shown in FIG. 7 starts when the program stored in the main memory 3 or the auxiliary storage device 4 is executed based on a command from the control unit 21.

First, the error detection unit 25 stores 1 in the array B [j] acquired in step 602 shown in FIG.
Byte data is acquired (step 701), and the number N of bits having a logical value of "1" among the bits forming this data is counted (step 702).

Next, the error detector 25 proceeds to step 702.
It is determined whether or not the number of bits N obtained in step 4 is an odd number (step 703). If it is determined that the number of bits N is an odd number, there is no error, so "0" is assigned to the error detection flag E (step 704). ), And ends this flow.

On the other hand, if it is determined that the number of bits N is not an odd number, it can be determined that there is an error, so "1" is assigned to the error detection flag E (step 705), and this flow is ended.

Next, the processing procedure of the display controller 24 will be described with reference to FIG. FIG. 8 is a flowchart for explaining the processing procedure in the display control unit. The processing procedure shown in FIG. 8 is started by executing a program stored in the main memory 3 or the auxiliary storage device 4 based on a command from the control unit 21.

First, the display control section 24 determines whether or not the control code is decoded in step 616 shown in FIG. 6 (step 801). When it is determined that the control code is decoded, the character string stored in the non-display memory is displayed on the display device 5 based on the command of the decoded control code (step 802), and this flow is ended. On the other hand, when it is determined that the control code is not decoded, this flow is immediately ended.

The display control section 24 also displays the television image and the video image, which are received by the receiving device 2 and converted into digital image data by the NTSC decoding device 6, on the display device 5, which has already been described. Since the conventional technique used can be used, the description is omitted here.

FIG. 16 is a timing chart for explaining the overall operation of the decoding apparatus of this embodiment. As described above, when the decoding device of this embodiment is activated,
The control unit 21 activates the receiving device 2 and the NTSC decoding device 6. As a result, the receiving device 2 receives the television signal and / or the video signal, as shown in FIG.

Further, the NTSC decoding device 6 is shown in FIG.
As shown in (b), the vertical synchronizing signal of the video signal received by the receiving device is used as a trigger to convert the video signal of one frame into digital video data and transfer the digital video data to the main memory 3 or the auxiliary storage device 4. As shown in FIG. 16 (c),
When the transfer of one frame of digital video data to the main memory 3 or the auxiliary storage device 4 is completed, "1" is set in the transfer end bit of the register. At this time, a buffer is provided so that the digital video data of the next frame is not overwritten on the digital video data of the previous frame, or the digital video data of the previous frame and the digital video data of the next frame are combined. Are preferably stored in different areas of the main memory 3 or the auxiliary storage device 4.

When the receiving device 2 and the NTSC decoding device 6 are activated, the control section 21 operates as shown in FIGS.
As shown in (f), the sampling section 22, the code analysis section 23, and the display control section 24 are activated at a predetermined timing each time "1" is set in the transfer end bit. As a result, the data code of the caption signal superimposed on each frame of the received video signal is decoded and displayed. In FIG. 16 (f), the execution time of the display control unit 24 is different because here the character is transmitted in the first frame and the control code indicating the display is transmitted in the second frame. It shows that the decoded character of the first frame is displayed at the stage of decoding the control code of. That is, the display control section 24 indicates that the control code for instructing the display is decoded and the decoded characters of the previous frame are displayed for the first time.

In the present embodiment, first, an analog video signal in which a caption signal is multiplexed is converted into digital video data, and a horizontal frame in which the caption signal is superposed from the digital video data forming the frame for each frame. The digital image data of the pixels forming the scan line is extracted. Next, the digital video data of the pixels forming the horizontal scanning line on which the caption signal is superimposed is sampled at pixel intervals substantially corresponding to the bit width (wavelength) of the caption signal, and the digital video data of the sampled pixels is set as a threshold value. The operation of allocating to "0" or "1" is performed by changing the sampling start position until the start code is detected. Then, the digital video data of the pixels forming the data code subsequent to the detected start code is detected by sampling at a pixel interval substantially corresponding to the bit width of the caption signal. Therefore, according to this embodiment, the caption signal multiplexed with the analog video signal can be obtained from the digital video data generated based on the analog video signal.

Further, in the present embodiment, since the start code and the data code of the caption signal are detected by the central processing unit 1 executing the program stored in the main memory 3 or the auxiliary storage device 4, the television It is possible to effectively use resources provided in advance in an information processing device such as a personal computer or a word processor capable of displaying a video image or a video image. Therefore, it is possible to inexpensively construct an information processing device that displays the caption data multiplexed with the video image at the same time as the television image or the video image. Further, in an information processing apparatus equipped with an NSP (native signal processor) or the like, all signal processing tends to be processed by software, so that the present embodiment is particularly effective for such an apparatus.

Further, in the present embodiment, the digital image data of the pixels forming the horizontal scanning line on which the caption signal is superimposed is sampled at the pixel intervals substantially corresponding to the bit width (wavelength) of the caption signal, thereby obtaining the caption signal. The start code and data code of are detected. Since the caption signal has 26 bits, for example, when the number of pixels per horizontal scanning line is 320, sampling is performed at a pixel interval of 12 pixels which substantially corresponds to the bit width of the caption signal. Further, when the number of pixels per horizontal scanning line is 640, sampling is performed at a pixel interval of 24 pixels, which approximately corresponds to the bit width of the caption signal. As described above, in the present embodiment, since the digital video data is sampled at the sampling interval determined by the number of bits of the caption signal and the number of pixels per horizontal scanning line, the horizontal scanning frequency of the display device changes and the caption changes. The caption signal can be acquired even when the frequency of the synchronization signal included in the signal changes.

In addition, in this embodiment, when the decoded character code is not a valid code, a predetermined special character is displayed on the display device 5. As a result, even when the caption signal cannot be accurately decoded because the received television signal and video signal are unstable, the user can be notified of that fact, and the decoding device of this embodiment can be used. Can be prevented from performing unstable operation. If this special character continues, it may be displayed that reception is impossible or the like, and the decoding device of the present embodiment may be terminated.

In this embodiment, the sampling unit 22
As described above, the Y data of one pixel is sampled at every sampling interval T and the Y data is distributed to “0” or “1” by the threshold value S.
However, as shown in FIGS. 9A and 9B, the sampling unit samples the Y data of the pixel at the sampling position and the pixels in the vicinity of the pixel, takes the average thereof, and sets this average value as the threshold value. The logical value of the sampled data code may be distributed to "0" or "1" by allocating it to "0" or "1" in S. Also, Y of the pixel at the sampling position and the pixel in the vicinity thereof
Logical value of the sampled data code depending on whether each data is distributed to "0" or "1" by the threshold value S and all the distributed results of each Y data are "0" or "1". May be distributed to “0” or “1.” This makes it possible to accurately sample the data of the caption signal even when the received television signal and video signal are unstable. When sampling Y data of a pixel and its neighboring pixels, the Y data of each sampled pixel is checked, and the pixel with the largest Y data value or the smallest pixel is located at the center of the sampled pixel. The sampling position may be corrected so that the sampling position is located at the peak or valley of the data code shown in FIG. It can be corrected.

In this embodiment, the threshold value S is set to a predetermined value in step 404 shown in FIG. 4, but this value does not have to be fixed. For example, in the code analysis unit 23, when an invalid code is confirmed, the value of the threshold S is automatically increased or decreased, and even if the received TV signal and video signal are unstable, The data of the caption signal may be accurately sampled and decoded. Further, the threshold value S may be input by the user via the input device 8. As a result, as shown in FIG. 10, even when the amplitudes of the luminance signals of the received television signal and video signal are reduced due to noise or the like, the user reduces the threshold value via the input device 8, The data of the caption signal can be accurately sampled and decoded.

Further, in step 402 shown in FIG. 4, the Y data of each pixel forming the 21st horizontal scanning line may be multiplied by an integer and stored in the array D. Figure 11 shows the data
It is a figure which shows an example of the waveform of the brightness | luminance data of each pixel which comprises a code. In particular, it shows that the waveform is broken due to the influence of noise or the like. In such a case, if the threshold value S is made too small, the portion A, which originally has a theoretical value of "0", is determined to be "1". On the other hand, if the threshold value S is made too large, the portion B, which originally has a theoretical value of "1", is determined to be "0". That is, the effective range of the threshold value becomes narrow. On the other hand, when the Y data of each pixel is multiplied by an integer and stored in the array D, the effective range of the threshold value S is widened as shown in FIG. 12, so that the threshold value can be easily set.

Next, a decoding device to which the second embodiment of the present invention is applied will be described.

In the first embodiment, the pixel interval corresponding to the bit width of the caption signal, which is the sampling interval T, is divided by the number of pixels per horizontal scanning line by the total number of bits (26 bits) of the caption signal. I explained what I asked for. On the other hand, in the present embodiment, a case will be described in which the sampling interval T is determined by examining the clock run-in signal of the caption signal. Since the hardware configuration of this embodiment is the same as that of the first embodiment, its drawing is omitted.

The functional configuration of the central processing unit used in this embodiment is different from the functional configuration of the central processing unit used in the first embodiment shown in FIG. 2, as shown in FIG. The point is that a cycle determining unit 1306 is provided for checking the run-in signal and determining the sampling interval T. Since the other points are the same as the functional configuration of the central processing unit shown in FIG. 2, those having the same functions are designated by the same reference numerals, and detailed description thereof will be omitted.

Further, in this embodiment, in step 404 of the processing procedure of the sampling section 22 shown in FIG. 4, a value obtained by dividing the number of pixels per horizontal scanning line by the total number of bits of the caption signal is set as the sampling interval T. Instead, the cycle determining unit 1306 is activated to determine the sampling interval T. Other processes are the same as those in the first embodiment.

Next, the processing procedure of the cycle determining unit 1306 will be described with reference to FIG. FIG. 14 is a flowchart for explaining the processing procedure in the cycle determining unit. FIG.
The processing procedure shown in FIG. 4 starts when a program stored in the main memory 3 or the auxiliary storage device 4 is executed based on a command from the control unit 21.

First, the cycle determining unit 1306 substitutes 1 into the counter k indicating how many cycles of the clock run-in signal have been investigated (step 1501).

Next, the cycle determining unit 1306 determines the Y data of the pixels forming the 21st horizontal scanning line stored in the array D in step 402 shown in FIG. The position where is stored is detected (step 1502).

Next, the cycle determining unit 1306 determines the step 1
While shifting the position one by one from the position detected in 502, the data of the array D is sequentially examined, and the number C1 of Y data continuing to be equal to or more than the threshold value S is counted (step 1503).
Next, the number C2 of Y data that is equal to or less than the threshold value S is counted (step 1504). And C1 and C2
, That is, the pixel interval corresponding to one cycle of the clock run-in signal is stored in the array C [k] provided in the main memory 3 or the auxiliary storage device 4 (step 150).
5).

Next, the cycle determining unit 1306 determines whether k is 6 or more (step 1506), and k is 6
If it is smaller, the value of k is set to 1 because the investigation of clock run-in signals for 6 cycles has not been completed.
Increases by one (step 1507) and returns to step 1502. On the other hand, when k is 6 or more, the investigation of the clock run-in signal for 6 cycles is completed, and therefore the average value of the data stored in the arrays C [1] to C [6] is calculated. , This value is determined as the sampling interval T (step 1508) and this flow ends.

As described above, in the first embodiment, by dividing the number of pixels per horizontal scanning line by the total number of bits of the caption signal, the pixel interval substantially corresponding to the bit width of the caption signal, that is, the sampling interval T Are seeking. This is based on the assumption that the caption signal is superimposed on the luminance signal over the entire 21st horizontal scanning line. However, if the received TV or video signal is unstable, the caption signal
It is also conceivable that the overlapping area on the horizontal scanning line may be slightly shifted depending on the frame. Even in such a case, according to the present embodiment, the sampling interval T is set by investigating the cycle of the clock run-in signal of the caption signal superimposed on the luminance information of the 21st horizontal scanning line, and therefore, the sampling interval T is accurately set. The data of the caption signal can be sampled. Other effects are similar to those of the first embodiment.

In this embodiment, i = 0 is set in step 406 shown in FIG. 4, and sampling for start code detection is performed by the first data D stored in the array D.
It starts from [0]. However, the pixel position of the last examined data may be substituted for i when k is determined to be 6 or more in step 1506 shown in FIG. Thereby, the data of the caption signal can be sampled at a higher speed.

Further, in this embodiment, in step 1508 of FIG. 14, the data stored in the arrays C [1] to C [6] (that is, the number of pixels corresponding to 6 cycles of the clock run-in signal). ) Average value of sampling interval T
However, the value that appears most frequently among the data stored in the arrays C [1] to C [6] may be set as the sampling interval T. For example, when the data of the arrays C [1] to C [6] are 5, 4, 6, 5, 5, and 6, respectively, the data “5” that appears most often may be determined as the sampling interval T. Further, one data may be dynamically selected from the data stored in the arrays C [1] to C [6] to set the sampling interval T. For example, arrays C [1] to C [6]
Of the data of 5, 4, 6, 5, 5, and 6, respectively, the sampling interval T is arrayed at the data “5” stored in the array C [1] at the first sampling, and the sampling interval T is arrayed at the next sampling. The sampling interval T is sequentially set to C [1], C [2], C [3], C [4], C [5], such as data “4” stored in C [2].
Sampling may be performed by replacing C [6] and C [1].

Further, in this embodiment, the cycle determining unit 13
06 determines the sampling interval T by examining the clock run-in signal for 6 cycles, but it is not always necessary to examine the clock run-in signal for 6 cycles,
For example, the sampling interval T may be determined by examining the clock run-in signal for three cycles.

The present embodiment is not limited to the above-described embodiments, but various modifications can be made within the scope of the gist thereof. For example, in each of the above embodiments, the television image and the video image received by the receiving device 2 are N
It was supposed that it was converted into YUV digital image data by the TSC decoding device 6, but RG
When converted to B digital image data, R obtained using the RGB / YUV conversion formula already known
This can be handled by converting GB data into YUV data.

Further, in each of the above-mentioned embodiments, an example in which the closed caption broadcast in the United States is applied has been described, but the present invention is also applicable to a text broadcast or the like broadcast in Japan.

[0099]

As described above, according to the present invention, based on the video signal converted into digital video data,
It is possible to acquire digital character information multiplexed with the video signal. Further, in the present invention, by sampling the digital video data at pixel intervals substantially corresponding to the 1-bit width (1 wavelength) of the character information, the horizontal scanning frequency of the display device changes, and the frequency of the character information accordingly. It is possible to acquire the character information even when is changed.

Further, in the information processing apparatus capable of displaying the television image or the video image, it is possible to inexpensively provide the function of displaying the caption data multiplexed with the image at the same time as the television image or the video image.

[Brief description of drawings]

FIG. 1 is a diagram showing a hardware configuration of a decoding device to which a first embodiment of the present invention is applied.

FIG. 2 is a diagram showing a functional configuration of a central processing unit shown in FIG.

3 is a flowchart showing a processing procedure of a control unit shown in FIG.

4 is a flowchart showing a processing procedure of a sampling section shown in FIG.

FIG. 5 is a diagram showing a part of a waveform of luminance data of a 21st horizontal scanning line on which a caption signal is superimposed.

6 is a flowchart showing a processing procedure of a code analysis unit shown in FIG.

FIG. 7 is a flowchart showing the processing procedure of the error detection unit shown in FIG.

8 is a flowchart showing an in-process procedure of the display control section shown in FIG.

9A and 9B are diagrams for explaining a sampling method of luminance data, FIG. 9A is a diagram showing a luminance data waveform of a portion having a 21st horizontal scanning line on which a caption signal is superimposed, and FIG. 9B is a diagram showing FIG. FIG. 7B is an enlarged view of a part of the waveform shown in FIG.

FIG. 10 is a diagram showing a part of a waveform of luminance data of a 21st horizontal scanning line on which a caption signal is superimposed, and particularly a diagram showing a case where the waveform is distorted due to the influence of noise or the like.

FIG. 11 is a diagram showing a luminance data waveform in a portion of a 21st horizontal scanning line on which a caption signal is superimposed,
In particular, it is a diagram showing a case where the waveform is distorted due to the influence of noise or the like.

FIG. 12 is a diagram for explaining a case where the luminance data shown in FIG. 11 is amplified by an integral multiple.

FIG. 13 is a diagram showing a functional configuration of a central processing unit used in a decoding device to which a second embodiment of the present invention is applied.

FIG. 14 is a flowchart showing a processing procedure of a cycle determining unit shown in FIG.

FIG. 15 shows that the received television signal and video signal are YU
It is a figure which shows the example of a data structure at the time of being converted into V4: 2: 2 digital video data.

16 is a timing diagram for explaining an overall operation of the decoding device shown in FIG.

FIG. 17 is a second diagram acquired by the sampling unit shown in FIG.
It is a figure which shows the data structure example of the digital video data of 1 horizontal scanning line.

18 is a second diagram acquired by the sampling unit shown in FIG.
It is a figure which shows the data structure at the time of storing the brightness | luminance data of each pixel of 1 horizontal scanning line in the array D.

[Explanation of symbols]

 1 central processing unit 2 receiving device 3 main memory 4 auxiliary storage device 5 display device 6 NTSC decoding device 7 bus 8 input device 21 control unit 22 sampling unit 23 code analysis unit 24 display unit 25 error detection unit 504 clock run-in signal 505 Start code 506 Data code 1306 Cycle determining unit

Claims (13)

[Claims] 1. A method for obtaining a digital signal multiplexed on a predetermined horizontal scanning line of a video signal, comprising: a conversion step for converting the video signal into multivalued digital video data in units of pixels; Among the pixels forming the frame, with reference to a predetermined pixel forming the horizontal scanning line,
An extraction step of extracting digital video data of pixels forming the horizontal scanning line at a pixel interval substantially corresponding to a 1-bit width of the digital signal, and the extracted digital video data is set to 2 at a predetermined threshold value.
A digital signal acquiring step of converting the value into a digital signal and acquiring the digital signal, and a method of acquiring a digital signal multiplexed with a video signal. 2. The horizontal scanning line according to claim 1, wherein the digital signal is multiplexed over the entire horizontal scanning line, and a pixel interval substantially corresponding to a 1-bit width of the digital signal forms the horizontal scanning line. A method for obtaining a digital signal multiplexed with a video signal, characterized in that the number of pixels is divided by the number of bits of the digital signal. 3. The digital signal according to claim 1, wherein the digital signal includes a synchronization signal and a data signal, and prior to the extraction process, digital video data of pixels forming the horizontal scanning line is sequentially set to a predetermined threshold value. And binarizes the digital video data to detect a pixel row composed of a first pixel row whose logical value is 1 and a second pixel row which is continuous with the first pixel row and whose logical value is 0. A method of acquiring a digital signal multiplexed with a video signal, comprising a pixel interval setting step of setting the number of pixels as a pixel interval substantially corresponding to the 1-bit width of the digital signal. 4. The synchronizing signal according to claim 3, wherein the synchronizing signal is a repetitive signal, and the pixel interval setting step detects the pixel columns two or more times consecutively within a repeating number of the synchronizing signal, A method for acquiring a digital signal multiplexed with a video signal, wherein an average value of the number of pixels of the detected pixel row is set as a pixel interval substantially corresponding to a 1-bit width of the digital signal. 5. The synchronizing signal according to claim 3, wherein the synchronizing signal is a repetitive signal, and the pixel interval setting step detects the pixel row two or more times consecutively within a repeating number of the synchronizing signal, A method for acquiring a digital signal multiplexed with a video signal, characterized in that the number of the most appearing pixels among the number of pixels in the detected pixel row is set as a pixel interval substantially corresponding to a 1-bit width of the digital signal. 6. The synchronizing signal according to claim 3, wherein the synchronizing signal is a repetitive signal, and the pixel interval setting step detects the pixel row two or more times consecutively within a range of the repeating number of the synchronizing signal, A digital signal multiplexed with a video signal, wherein the number of pixels in the detected pixel row is dynamically selected and the selected number of pixels is set as a pixel interval substantially corresponding to a 1-bit width of the digital signal. How to get. 7. The digital signal according to claim 1, wherein the digital signal includes a data signal and a start signal composed of a plurality of bits for specifying a start position of the data signal, and the horizontal scanning line is scanned before the extraction step. It is said that the digital video data of the constituent pixels is extracted by the number of bits of the start signal at pixel intervals substantially corresponding to the 1-bit width of the digital signal, and the extracted digital video data is binarized by a predetermined threshold value. A start signal detection step of performing the operation by changing the extraction start position until the binarized result matches the value of the bit string of the start signal, and a value of the bit string of the start signal detected in the start signal detection step. An extraction start pixel setting step of setting the predetermined pixel on the basis of the pixel position of the coincident digital video data, Multiplexed method for obtaining the digital signal to the video signal that. 8. The extracting process according to claim 1, wherein the extracting step extracts the digital video data of the pixels forming the horizontal scanning line at a pixel interval substantially corresponding to a 1-bit width of the digital signal. The digital video data of the pixel located near the pixel of the video data is also extracted, and the digital signal acquisition step includes the digital video data of the pixel extracted at a pixel interval substantially corresponding to the 1-bit width of the digital signal and the vicinity of the pixel. A method of acquiring a digital signal multiplexed with a video signal, comprising: binarizing an average value of digital video data of a pixel located at the threshold value with the threshold value to acquire the digital signal. 9. The extracting process according to claim 1, wherein the extracting step extracts digital video data of pixels forming the horizontal scanning line at a pixel interval substantially corresponding to a 1-bit width of the digital signal. The digital video data of the pixel located near the pixel of the video data is also extracted. When each of the extracted digital video data of the plurality of pixels is equal to or more than the threshold value, the pixel having the largest digital video data is extracted. The extraction position is corrected to be the center position, and when each of the extracted digital video data of a plurality of pixels is equal to or less than the threshold value, the pixel having the smallest digital video data is set to the extraction center position. A method for obtaining a digital signal multiplexed with a video signal, characterized by having an extraction position correction process for correcting the extraction position. 10. A decoding device for a digital signal multiplexed on a predetermined horizontal scanning line of a video signal, comprising: a converting means for converting the video signal into multivalued digital video data in units of pixels; A storage unit that stores digital video data of pixels that form the horizontal scanning line among the pixels that form the frame in a storage medium; and the storage unit based on a predetermined number of pixels that form the horizontal scanning line. Extracting means for extracting the digital video data of the pixel stored in the pixel at a pixel interval substantially corresponding to the 1-bit width of the digital signal; A digital signal acquiring unit that acquires a digital signal; and a decoding unit that decodes the digital signal acquired by the digital signal acquiring unit. DOO decoding apparatus of the multiplexed digital signal into a video signal characterized by. 11. A decoding device for a digital signal multiplexed with a video signal according to claim 10, further comprising threshold setting means for setting the threshold based on a command from a user. 12. The error detecting means for detecting an error in a digital signal acquired by the digital signal acquiring means, and the threshold value is changed when the error is detected by the error detecting means. A decoding device for a digital signal multiplexed with a video signal, comprising: a threshold changing means. 13. The video decoding means according to claim 10, 11 or 12, wherein video decoding means for decoding digital video data of pixels constituting the frame, and video decoded by the video decoding means are displayed on a display medium. And a display means for displaying the result decoded by the decoding means on the display medium, and a decoding device for a digital signal multiplexed with a video signal.