JPH045312B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device that receives a still image signal sent using a part of a vertical retrace period of a television signal.

In recent years, a new form of broadcasting, so-called teletext, has been introduced, which multiplexes and transmits still image information signals such as text and graphics during the vertical retrace period of a television signal, thereby providing program services such as news and weather forecasts. Research on this method is active.

For example, Journal of the Institute of Electronics and Communication Engineers, 1980, Vol. 63, No.
1, pp. 38-45 describes several methods for this purpose.

By the way, among these teletext systems, 1.
In the second method, when a receiver selects a teletext program and selects the corresponding teletext channel, it sometimes takes a considerable amount of time before the still image of the program is displayed on the cathode ray tube of the television receiver. It is known that waiting time is required.

For example, in the teletext system known as the NHK-C system, this waiting time is related to the number of programs being transmitted; for example, if 10 programs are being transmitted, it can reach more than 30 seconds. . The reason for such a long waiting time is that teletext signals are transmitted only in a very small time span during the vertical retrace period of the television signal, so there are many teletext programs. This is because in some cases, a large amount of data cannot be transmitted in a sufficiently short time. This will be explained more specifically using drawings. Figure 1 shows the teletext signal format in the NHK-C system, where a is the signal multiplexing position,
b shows the general format of the signal, and c shows a more detailed explanatory diagram of the general format of the signal. In this system, teletext is broadcast during the 20th scanning period (odd field) and the 283rd scanning period (even field) of the television signal.
This is carried out using a short time width of one horizontal scanning period per field. Further, the number of programs to be transmitted is expressed in 2 bytes as shown in FIG. 1c, and up to 2 ¹⁶ =256 programs can be transmitted. However, it takes about 3.5 seconds to transmit one screen of one of these programs, so in order to avoid waiting time, normally only about 10 programs are transmitted sequentially. Even in this state, it takes 3.5 seconds x 10 = 35 seconds to transmit a certain program and then transmit the same program again. For this reason, when you select a channel that corresponds to a certain program, sometimes the characters and graphics of the program on that channel are played immediately, but sometimes there is a waiting time, and the waiting time is the maximum even when transmitting 10 programs. It will reach 35 seconds.

By the way, during this waiting time, naturally nothing is displayed on the image reproducing device such as a cathode ray tube. Therefore, even when a receiver selects a teletext channel, there is a low probability that the characters, graphics, etc. of that channel will be immediately played back. This had the drawback that no image was reproduced, which caused great discomfort to the recipient.

Furthermore, although there are as many as 256 programs that can be transmitted, only about 10 programs are actually transmitted, so if the program channel selected by the user belongs to a program that is not being transmitted, The waiting time was enormous, and there was also the drawback that it was difficult to tell whether it was a waiting time or an incorrect selection, causing even greater discomfort.

Furthermore, the user has no way of knowing what program number is actually being transmitted, resulting in poor operability.

SUMMARY OF THE INVENTION An object of the present invention is to provide a teletext receiving device which eliminates the drawbacks of the prior art described above and has a new function of notifying the receiver of waiting time or incorrect channel selection so as not to cause discomfort to the receiver. There is something to do.

Another object of the present invention is to provide a teletext receiving apparatus which has improved operability and has means for collectively informing users of program numbers being transmitted.

In order to achieve this object, the present invention provides a memory circuit that sequentially stores signals indicating program numbers in a transmitted teletext signal for a certain period of time, and stores signals in the memory circuit according to the channel selection of the receiver. The program number of the teletext signal that has arrived up to that point is compared with the selected program number, and if they match, a message indicating that there is a waiting period until the next signal arrives will be displayed. If the channel is selected incorrectly, a message is displayed to the effect that the channel has been selected incorrectly.

Furthermore, the program number of the teletext signal that has arrived up to that point, which is stored in the memory circuit, is
It is characterized by being able to be displayed all at once according to the user's instructions.

Hereinafter, the present invention will be explained in detail using the drawings.

FIG. 2 is a block diagram showing an embodiment of a teletext receiving device according to the present invention, in which 1 is a block diagram showing a teletext signal that is transmitted by being time-division multiplexed and superimposed during the vertical retrace period of a television signal. a buffer memory for storing the time within the field; 2 a sync separation circuit for separating and reproducing a sync signal from a television signal; 3 a signal superimposition period pulse generation circuit for generating a pulse indicating a period during which a teletext signal is being transmitted; 4 is a storage address generation circuit that generates an address for storing a character signal in buffer memory 1; 5 is a signal conversion circuit that converts a television signal to a signal level that can be stored in buffer memory 1;
6 is an address switching circuit, 7 is a read-only program memory (hereinafter abbreviated as program ROM), 8 is a read/write data memory (hereinafter abbreviated as data memory), and 9 is a central processing circuit such as a microcomputer (hereinafter abbreviated as CPU). ), 10 is an address switching circuit, 11 is a display memory in which signals such as characters and figures are stored, and the stored contents are displayed on a display device, and 12 is a display signal synthesizer for synthesizing signals for display on a cathode ray tube, etc. 13 is a display device typified by a cathode ray tube; 14 is a display address generation circuit that generates an address for display;
15 is a keyboard for selecting a teletext channel, and 16 is a keyboard interface circuit. Also, 17 is the address bus of CPU9, 18
1 is a data bus, 19 and 20 are transmission lines for transmitting interrupt signals to the CPU 9, and 21 is a transmission line for television signals.

Next, the operation of this teletext receiving apparatus will be explained. This device temporarily stores the sent teletext signal in the buffer memory 1, reads the teletext signal with the CPU 9, decodes and processes it, and displays the necessary information until the next teletext signal arrives. It has the function of transmitting data to the memory 11 for display. The detailed operation is as follows. The television signal input through the transmission path 21 is input to the signal conversion circuit 5, the storage address generation circuit 4, and the sync separation circuit 2. The synchronization separation circuit 2 separates the synchronization pulse from the television signal and supplies it to the signal superimposition period pulse generation circuit 3. The signal superimposition period pulse generation circuit 3 counts horizontal synchronization pulses using the vertical synchronization pulse as a reference, and generates pulses indicating the 20th horizontal scanning period in odd-numbered fields and the 283rd horizontal scanning period in even-numbered fields.
9 and the address switching circuit 6. Furthermore, the storage address generation circuit 4 generates an address to be stored in the buffer memory from the television signal and supplies it to the address switching circuit 6. The address of the CPU 9 is input to the other input of the address switching circuit 6, and the output signal of the storage address generation circuit 4 is output only during the period when the teletext signal is multiplexed, and the output signal from the CPU 9 is output during other periods. The address is directly output to the buffer memory 1 as an address signal. Therefore, buffer memory 1
An address signal is supplied to the address signal so as to store only the teletext signal portion of the signal input through the signal conversion circuit 5, and the contents are read out by the CPU 9 except during the signal superimposition period. When a teletext signal is stored in buffer memory 1, at the same time
The output signal from the signal superimposition period pulse generation circuit 3 is also transmitted to the CPU 9 via the interrupt signal transmission path 19, causing an interrupt to the CPU 9, and transmitting to the CPU 9 that the contents of the buffer memory have been updated. Therefore, the CPU 9 uses the program ROM 7
2-byte information indicating the program number in the teletext signal stored in the buffer memory 1 is successively stored in the data memory 8 in the order of arrival. This situation is shown in FIG.
By storing the program number information in the data memory 8 of a certain capacity in the order of arrival and discarding the oldest information at the time of storage, the data memory 8 can store only the program number information that has arrived a certain period of time from the present time. Become. Furthermore, in this case, the same program number information that has already been stored may also be discarded at the same time.

On the other hand, the user selects the desired teletext channel using the keyboard 15, and the program information is transmitted via the keyboard interface circuit 16.
It is transmitted to CPU9. Therefore, keyboard 15
If the channel is selected by
The operation of CPU 9 is as follows. First, the program numbers stored in the data memory 8 are read one after another, and it is checked whether a program number equal to the selected program number is stored. Next, when both program numbers match, the information in the form of characters or figures indicating that the waiting time is in progress, which was previously stored in the block diagram memory 7, is transferred and stored in the display memory 11. In addition, if the program numbers of both do not match at all, information in the form of characters or figures indicating that the program is a non-transmission program or an erroneous selection stored in the program memory 7 in advance is transferred to the display memory 11. Remember. The transferred and stored information is displayed by a circuit configuration (configuration of address switching circuit 10, display memory 11, display signal synthesis circuit 12, display device 13, and display address generation circuit 14) that is well known in general display devices. .

Next, if a display indicating that the waiting period is in progress is made, wait until the teletext signal stored in the buffer memory 1 is updated, read the teletext signal, and read the program number in the teletext signal. It is checked whether the program number and the selected channel match. Only when the program information on both sides matches,
Display memory 11 for information data of the teletext signal
The text and graphics information is transferred to and stored in and displayed. If an incorrect selection is displayed, the display continues until a new program channel is selected. Furthermore, in this case, it would be even more effective to use a dynamic display, for example, periodically flashing characters or figures, in order to call the recipient's attention. This can be easily achieved by periodically changing the information data transfer to the display memory.

The program number information in the data memory 8 is updated by interrupts even during the above processing, so the next time the receiver selects a new teletext channel, the program number information in the data memory 8 will be updated using the same process. It is possible to correctly display "waiting" or "incorrect selection" by processing the program number that is currently available. The flowchart of these processes is shown in FIG. 4. In this way, it memorizes the program number that has already arrived, determines whether it is being transmitted, and immediately starts displaying it, which eliminates the problem of waiting time, which was a drawback of conventional methods, and eliminates the problem of "waiting" or "incorrect selection". Information can be immediately communicated to the recipient.

Furthermore, when the user wishes to display the transmission program number using the keyboard 15, the instruction is sent to the CPU via the keyboard interface circuit 16.
9. Then, the CPU 9 reads out the program numbers stored in the data memory 8 one after another, and transfers and stores the character or graphic information corresponding to the number stored in the program memory 7 in advance in the display memory 11. As a result, the transferred and stored information is displayed as described above, so that the user can know the transmitted program number all at once.

In addition, in the above explanation, the teletext system is
Although the present invention has been described as an apparatus for processing character and graphic information transmitted in a pattern using the example of the NHK-C system, the present invention can also be applied to cases where encoded transmission is performed using other teletext broadcasting systems.

Furthermore, since each program requires only a few bytes of data memory capacity, in the case of 10 programs, the total data memory capacity can be as small as several tens of bytes.
Therefore, it is also possible to realize the functions of the present invention with an inexpensive configuration by using other memory, such as by using the surplus area of the display memory.

As described above, according to the present invention, it is possible to provide a new function that notifies the receiver of whether there is a waiting period or an incorrect channel selection when selecting a teletext channel. It becomes possible to provide a teletext receiving device with excellent operability. Furthermore, it becomes possible to display what program number the program is currently being transmitted, and it becomes possible to provide a teletext receiving device with even better operability.

[Brief explanation of drawings]

Figures 1a to 1c are one type of teletext broadcasting.
An explanatory diagram showing the signal format of the NHK-C system, FIG. 2 is a block diagram showing an embodiment of the present invention,
FIG. 3 is a model diagram showing the process of storing a teletext signal in the data RAM, and FIG. 4 is a flowchart showing the flow of the processing operation in the present invention. Explanation of symbols, 1: Buffer memory, 2: Synchronous separation circuit, 3: Signal superimposition period pulse generation circuit, 4: Storage address generation circuit, 5: Signal conversion circuit, 6: Address switching circuit, 7: Program ROM, 8: Data memory , 9: CPU, 10: Address switching circuit, 11: Display memory, 12: Display signal synthesis circuit, 13: Display device, 14: Display address generation circuit, 15: Keyboard, 16: Keyboard interface, 17: Address bus , 18: data bus, 19-21: transmission line.

Claims (1)

[Scope of Claims] 1. A teletext receiving device that receives a teletext signal transmitted superimposed on a television signal, reproduces a still image corresponding to a program selected by a user, and displays it on a display means, A program memory stores a plurality of program numbers of incoming teletext signals, and when a user selects and inputs a desired program number, the program number and a series of program numbers read from the program memory are stored. If a match is not found as a result of the comparison, specific characters or figures are displayed on the display means, and if a match is found, a still image corresponding to the selected program number is displayed. A teletext receiving apparatus characterized by comprising: a control means for causing the display means to display specific characters or graphics different from the characters or graphics until the characters or graphics become displayable. 2. The teletext receiving apparatus according to claim 1, further comprising a control means for reading out a plurality of program numbers stored in the program memory as desired, converting them into characters, and displaying the converted characters on the display means. A teletext receiving device characterized by: