JPS6261197B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention receives still image signals such as characters and graphics that are superimposed separately from normal video signals during the vertical blanking period of a television signal, and processes the signals by a central processing unit such as a microprocessor. The purpose of this invention is to provide accurate operation for a device that processes data, stores it, reads it out, and displays a still image.

The still image signal superimposed on the video signal and sent out has, for example, the following format. That is, on the transmitting side, the pattern signal is decomposed into a matrix of pixels of 248 bits horizontally, 204 lines vertically, and a total number of pixels of 248 x 204 = 50592 bits, and the above pixels are 8 bits horizontally and 12 lines vertically, making a total of 96 bits. 31 horizontal blocks, 17 vertical levels of color signals, each of the above still image signals for one horizontal line (248 bits for pattern signals, 31 blocks for color signals) from the 10th H (273rd H) to the 21st H of the vertical blanking period. It is sent out with various control codes added during an arbitrary period of the 284th H.

Examples of the types of control codes to be added include:
There is a start signal CR, framing code FC, service identification/interrupt (SI/IN), and data identification DI.

At the same time, a still image is composed of multiple programs and pages, and the data packet PCP that controls the entire program/page is also sent out prior to the pattern signal and color signal packets. Signal CR), framing code CR, service identification/interrupt (SI/IN), and data identification DI are added.

On the other hand, on the television receiver side, for example, in the system shown in FIG. 1, the still image signal superimposed on the television signal is separated, demodulated, and displayed on the screen. That is, in FIG. 1, a television signal received by antenna 1 and superimposed with a still image signal is amplified by selecting a desired channel by tuner 2, converted to a video intermediate frequency, and further amplified by video intermediate frequency amplification circuit 3. After detection, it is converted into a video signal and guided to the video amplification circuit 4. The cathode ray tube 15 is then driven to display a normal television image.

On the other hand, the video signal on which the still image signal has been superimposed is supplied to a extraction circuit 6, where the still image signal is separated from the normal television signal and temporarily stored in a buffer memory 7.

This stored data is processed within one field period by a central processing unit (hereinafter abbreviated as CPu) 8 such as a microprocessor. If the program and page selected by the program selection device 11 are the same as the data stored in the buffer memory 7, the data is transferred to the pattern memory 12 and color memory 13 for display on the TV screen via the bus line 16. Transferred and stored. Bus line 9 is a data bus for transferring data. It consists of an address bus that determines address information for memory and input/output devices, and a control bus that controls these.

By repeating the above transfer and storage until one still image (for example, 204 lines) is stored, information for one selected still image is accumulated in the pattern memory 12 and color memory 13. Then, the readout control circuit 14 sequentially reads out the stored contents from the pattern memory 12 and color memory 13 in synchronization with the scanning of the color television, and supplies the stored contents to the cathode ray tube 15 via the output interface circuit 5, so that the contents are displayed on the television screen. A still image is obtained.

The ROM9 is a read-only memory that stores the processing procedures of the CPU8 for processing still image signals.The RAM10 is a read-only memory that stores the processing procedures of the CPU8 for processing still image signals.
Read/write memory for temporarily storing and storing data. Here buffer memory 7
Because the bit rate (for example, 5.73 bits/second) of the transmitted still image signal is much faster than the data processing speed of the CPU8, one packet of the still image signal is temporarily stored in the buffer memory 7, and then the next one is stored. This is to read and process the stored contents as necessary during one field period until a new still image signal arrives.

The present invention attempts to perform accurate operation even when a channel in which a still image signal is superimposed is changed to a channel in which it is not superimposed during a vertical blanking period, or when superimposition of a still image signal is stopped. It is. This will be explained in detail below.

Figure 2 shows the structure of a still image signal (data packet), including a page control packet PCP, a color code packet CCP, a pattern data packet PDP, a horizontal scroll packet HDP, and a program index packet.
There are six types in total: PIP and dummy packet DMP. Each of these packets has a control section (header section) at the beginning. For example, writing to the buffer memory 7 in FIG.
After synchronizing extraction using CR and framing code FC, subsequent data is written to buffer memory.

Here, if you change from the channel on which the still image signal is superimposed (of the tuner) to another channel on which the still image signal is not superimposed, the contents of the buffer memory in Figure 1 remain stored, and the still image Even if the channel is not superimposed, it will be incorrectly determined that it is superimposed, and accurate operation will not be possible.

In view of this situation, the present invention writes a code that is not included in the still image signal into the buffer memory 7 shown in FIG. 1, or writes a second code into the buffer memory 7.
It is characterized by performing accurate operations by writing code that is not affected by the process of assembling still images, such as the dummy packet DMP shown in the figure.

To process still image signals, for example, the method shown in Figure 1 is used.
The data in the buffer memory 7 is read by the CPU8 to assemble a still image, but once read from the buffer memory, the contents of the buffer memory are no longer needed.The contents of this unnecessary buffer memory are rewritten. This allows for more accurate movement. Here, the code that is not included in the still image signal mentioned above will be explained below.

For example, a check bit as shown in Fig. 3 is added to all control codes except for the clock run-in CR and framing code FC of the still image signal (data packet) shown in Fig. 2. When this check bit is added, 1 bit is added. Even a code with a 1-bit error can be corrected. Since a code with a 1-bit error can also be a still image signal, the number of combinations is
If even 1 bit error becomes true data for a ₁ in the figure, then for 9 combinations a ₁ to a ₁₆ , 9×
There are 16 = 144 combinations. However, the third
As shown in the figure, with 8 bits, ²⁸ = 256 combinations are possible, and 256-144 = 112 codes are impossible for a still image signal.

To control still image signals, write one of 112 codes that cannot be used as control codes for still image signals, and read and process the contents of the buffer memory using the processing sequence of CPU8 shown in Figure 1. If the code does not exist in the code, you can ensure accurate operation by not processing the entire packet.

[Brief explanation of the drawing]

Fig. 1 is a diagram of the still image receiving system of the present invention;
This figure is a diagram showing the configuration of a still image signal (data packet), and FIG. 3 is a diagram showing the bit configuration of the Hamming code of the present invention. 4 is video amplification, 5 is output interface, 6
is an extraction circuit, 7 is a buffer memory, 8 is a central processing unit CPu, and 9 is for program storage.
ROM, 10 is a work RAM, 11 is a still picture program selection device, 12 is a pattern memory, 13 is a color memory, and 16 is a bus line.

Claims (1)

[Claims] 1. A still image signal superimposed during the vertical blanking period of a television signal is temporarily stored in a buffer memory, and the stored still image signal is read out from this buffer memory and displayed on a display device. In a teletext receiver that performs assembly processing for displaying still images, each time stored data is read from the buffer memory, the read stored data in the buffer memory is rewritten to a special code that prevents the assembly processing described above from being performed. A teletext receiver characterized by: 2. The teletext receiver according to claim 1, wherein the special code is a code that is not included in the control code of the still image signal. 3. The teletext receiver according to claim 1, wherein the special code is a dummy packet.