JPS62157488A - Character picture display system for teletext - Google Patents

Abstract

PURPOSE:To shorten a display delay time by renewing a received character picture to a new picture, accommodating it to a data accommodating memory and reading and displaying the picture to exist in the data accommodating memory out of the designated character picture from the data accommodating memory. CONSTITUTION:For a data accommodating RAM 2, the updated receiving data are superscribed to the oldest written at the tip each time accommodating data come to be full. The control of such a writing is realized by circulating the writing address in the data accommodating RAM 2. A central processing unit 1, when a program displaying command is received, inspects whether or not the data control information of the program related to the displaying request exists at the data control table. The central processing device 1 detects that the equivalent data control information exists, and when fetching is completed, the character data of the equivalent program are read. By using a character generator 6, a character code is converted to a dot pattern and written into a bit map memory 3 for displaying.

Description

[Detailed description of the invention]

OBJECT OF THE INVENTION INDUSTRIAL APPLICATION FIELD OF THE INVENTION The present invention relates to a character screen display system used in a teletext receiver. Conventional technology Currently, large amounts of breaking information such as news, weather forecasts, and traffic information displayed in text and graphics are sent out as packets during the vertical retrace period of a television video signal.
Teletext multiplex broadcasting, in which this is extracted on the receiver side and displayed in place of all or part of a conventional television screen, is being put into practical use. Each character screen is specified by a combination of the number of a magazine containing a group of programs, the number of a program belonging to each magazine, and the number of the page composing the program. As stated in Mr. Yanagimachi's paper entitled "Overview of Coded Transmission Teletext Broadcasting System" published in the NHK Giken Monthly Report published in August 1985, each program is divided into repetitive/ Classified into non-repetitive, lumped/non-lumped, and independent/complementary. In a repetitive program, character data is repeatedly transmitted at a cycle of about the viewing time of one page (usually 20 to 30 seconds). In a batch program, text data is transmitted in batches, stored in the receiver's memory, and pages selected by the receiver are displayed. In complementary programs, text data related to the content of the TV program, such as subtitle information, is sent out as the TV program progresses.
For any program, after the viewer requests display while specifying the magazine number and program number, reception of character data starts from the beginning of the corresponding number, and display is performed after this reception is completed. Problems to be Solved by the Invention In the conventional display system described above, reception of the program starts after receiving a request from the viewer, so in the case of repetitive or batch programs, there is a delay until the next transmission starts. There is a problem that a considerable amount of waiting time occurs, and the display is delayed accordingly. In particular, for repetitive or batch programs, reception starts from the first transmission unit, so if the display of that program is requested immediately after the first transmission unit has finished transmitting, the next first transmission unit will be retransmitted. The problem is that it takes a long time to wait until the Means for Solving the Constituent Problems of the Invention The display system of the present invention which solves the problems of the above-mentioned prior art is as follows:
By updating the received character screen to the latest one and storing it in the data storage memory, and reading out the designated character screen existing in this data storage memory from this data storage memory and displaying it. It is configured to reduce display delay time. Hereinafter, the operation of the present invention will be explained in detail together with examples. FIG. 1 is a block diagram showing the configuration of the minimum portion necessary for explaining this embodiment of a teletext receiver to which a display method according to an embodiment of the present invention is applied. This receiver includes a central processing unit (CPU) 1, a data storage RAM 2, a display bitmap memory 3, a color look amplifier table 4, a system bus 5, a character generator 6, a CRT controller 7, a program ROM 8, It includes a data extraction circuit 9, a line buffer 10, and an A/D conversion circuit 11. The data extraction circuit 9 extracts character information appearing within the vertical blanking period of the television signal supplied from the receiver side in units of horizontal lines and stores it in the line buffer 10.
A reception end interrupt is issued to the central processing unit l. When the central processing unit 1 receives this reception end interrupt,
While creating a data management table for each transmission unit in a work area in the data storage RAM 2, received data is stored in the data storage area in the data storage RAM 2. The storage capacity of the data storage RAM 2 is large enough to store all pages of all programs. The data management information in the data management table created for each transmission unit in the data storage RAM Z is based on the horizontal line from which the data has been transmitted, as illustrated in Figure 2 (A) and (B). Line number, service index (
Consists of area I->1 for writing program data header (PRCI) or page data header (PACI), magazine number, program number and page number, data import address, import end flag, and re-import start address. has been done. One entry of data management information consisting of the above areas 1-XI is created for each transmission unit. Here, the unit of transmission is one page in the case of a non-batch data program, and one program in the case of batch data. Data for one program is transmitted using one horizontal scanning line (line) with the same line number within each vertical blanking line. The data transmission lines within the vertical blanking line range from the 10th line to the 21st line, and are expressed in hexadecimal numbers as [OA].
Line numbers from [15] to [15] are written. FIG. 3 shows an example of management information regarding data transmitted on line 21. There are four types of service indexes (SI) depending on the transmission mode [92],
There are [46], [2A], and (FE), two of which instruct the receiver to perform sequential reception processing of data packets, and the remaining two instruct the receiver to perform recording reception processing. In Figure 2 (B), the service index (Sl) is (
FE) is illustrated as management information of program data related to the service index identified by E). Program data header (PRCI) and page data header (PA)
CI) are [20] and [21] in hexadecimal notation, respectively.
FIG. 2(B) shows that it is management information related to PACI. Also, Figure 2 (B)
9N area■ is the magazine number

[0], program number (903
), is illustrated as management information regarding data with page number [4]. Also, according to the data import address consisting of areas ■, ■, and CF F F F) written in areas ■ and ■ in Figure 2 (B) indicates that the data import for the sending unit managed by this management information has been completed. This is an example. Furthermore, since the same program has been transmitted again according to the re-capturing start address written in areas X and XI, the re-capturing is started from address (41260). FIG. 3 is a flowchart showing the procedure of data management information registration processing by the central processing unit 1. The central processing unit 1 is activated by a reception end interrupt by the table sampling circuit 9 every time the data sampling circuit 9 finishes extracting data appearing on one horizontal scanning line within the vertical blanking line, and executes the procedure shown in FIG. The data management information registration process starts. In the first step 31, the central processing unit 1 checks whether the received data is the first data of the transmission unit,
If so, the process advances to step 32 to check whether data management information for this transmission unit already exists. If the data management information for this transmission unit does not yet exist in the data management table, the process advances to step 33 and the data management information is registered in the data management table. In other words, the line number and service index (SI
), program data header (PRCI)/page data header (
PACI), magazine number, program program, page program, and data import start address of the data storage RAM 2 are registered in the data management table, and the process proceeds to step 35. When the central processing unit 1 detects in step 32 that the data management information for the sending unit has been registered, the process proceeds to step 34, registers the re-fetching start address, and proceeds to step 35. The central processing unit 1 performs step 3
1, if it is detected that the received data is not the first data of the transmission unit, the process immediately proceeds to step 35. When the receiving central processing unit 1 detects in step 35 that the received data is the last of the transmission unit, the receiving central processing unit 1 proceeds to step 36,
The data capture end address and capture end flag are registered in the data management information, and the process proceeds to step 37. In step 37, the central processing unit l detects whether or not the acquisition of the first data for the sending unit has been completed;
If so, proceed to step 39. When the central processing unit 1 detects in step 37 that the first data acquisition has not been completed, the process proceeds to step 38, and after rewriting the data acquisition start address in the data management information with the re-intake start address, the process proceeds to step 39. . In step 39, the central processing unit 1 writes the received data to the data storage area in the data storage RAM 2, and
Ends data transfer processing for the line. Each time the data storage RAM 2 becomes full of stored data, the oldest data written first is overwritten with the latest received data. Such write control is realized by rotating write addresses in the data storage RAM 2. As mentioned above, the storage capacity of the data storage RAM 2 is large enough to store all programs, so by the time the data of a certain program starts to be erased as the oldest data, new acquisition of data for that program will start. Either there is, or this has already ended. Therefore, after a sufficiently long period of time has passed since the start of data capture, only the latest data for all programs will reside in the data storage RAM 2. FIG. 4 is a flowchart showing the procedure of program display processing performed by the central processing unit 1 in response to a program display request from a viewer. When the central processing unit 1 receives a program display command, in a first step 41 it checks whether data management information of the program related to the display request exists in the data management table. When the central processing unit 1 detects that the corresponding data management information exists, it proceeds to the next step 42, searches whether or not the capture of the program has been completed, and if the capture has been completed, the process proceeds to step 42. The program proceeds to step 43, where character data of the corresponding program is read and drawn. That is, the central processing unit 1 sequentially reads data whose line number and service index (SI) match from among the data written between the capture start address and the capture end address in the data storage RAM 2, and stores the characters. - Converting the character code into a dot pattern using the generator 6 and writing it into the display bitmap memory 3. When the central processing unit 1 detects in step 41 that the program related to the display request is not stored in the data storage RAM Z, it repeats the determination in step 41 until the program is completely stored. The same applies when it is detected in step 42 that the capture of the corresponding program has not been completed. The above example shows a configuration in which data is stored for programs of all received magazine numbers, but only programs belonging to a specific magazine that is frequently used on a daily basis, or only specific programs within that specific magazine can be selected. It is also possible to have a configuration in which the storage capacity of the data storage RAM is reduced by storing the data in the data storage RAM. Effects of the Invention As explained in detail above, the display method of the present invention stores the received character screen in the data storage memory, and also stores the specified character screen existing in the data storage memory in this data. Since the image is read from the storage memory and displayed, the display delay time can be significantly reduced.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing the configuration of the minimum portion necessary for explaining this embodiment of a teletext receiver to which a display method according to an embodiment of the present invention is applied, and FIG. 3 and 4 are conceptual diagrams showing the structure of data management information in the data management table created in the data storage RAM Z shown in FIG. 7 is a flowchart showing the procedure of display processing. 1...Central processing unit, 2...Data storage RAM, 3...
Display bitmap memo, 4. Color lookup table, 6. Character generator, 7. CRT controller, 9. Data extraction circuit, 10. Line buffer.

Claims (1)

[Claims] A text-based multiplex broadcasting system in which a character screen transmitted during a vertical retrace period of a television screen is extracted and a specified character screen is displayed in place of part or all of the television screen. In the screen display method, the received character screen is updated to the latest one and stored in the data storage memory, and the specified character screen that exists in this data storage memory is read from this data storage memory. A character screen display method for teletext broadcasting characterized by displaying.