JPS58168392A - Device for receiving multiple broadcasting of character - Google Patents

Abstract

PURPOSE:To prevent display from difficult to see containing many errors with low quality, by inhibiting display of a received signal having an error ratio higher than a prescribed value. CONSTITUTION:An added picture information signal superposed to a television signal received by a clock from a clock generating circuit 9 is sampled and the sampled signal corresponding to one picture is stored in a main memory 12. An output read out from the main memory 12 and an output from a croma video processing circuit 4 are applied to a cathode ray tube 14 through a mixing/ switching circuit 13. An R/W processing circuit 10 detects the number of errors of an encoding signal having an error correcting function included in the received added picture information signal, and when the number of errors within a fixed period exceeds the prescribed value, inhibits the display of picture information in receiving.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention receives so-called teletext broadcasting in which additional image information signals such as characters and graphics are superimposed on a television signal, and stores the additional image information signals in a memory. In addition, regarding a teletext receiving device that reads out and displays image information, the additional image information signal may be received in a state where the received television signal is of a weak electric field and contains a lot of noise or a lot of ghost signals. If the image cannot be received accurately, this is detected by detecting the error rate of the encoded signal with an error correction function in the additional image signal, and if the error rate is above a certain level, the error rate is detected. It is an object of the present invention to provide a device that prevents display of image information based on received signals, thereby preventing erroneous and difficult-to-see displays on the screen.

2. Description of the Related Art So-called teletext broadcasting has been proposed as a means of multiplexing and transmitting separate new image information using a television broadcast signal. As shown in FIG. 1A, this can be done by using the vertical blanking period of a normal television broadcast signal, and then
The additional image information signal, in which additional image information such as characters or figures is decomposed and transmitted during the horizontal scanning period, is superimposed with a binary digital signal and transmitted. This image information packet is composed of a header section and an information data section. Depending on the content of the information contained in the data portion, there are different types of packets, such as page control packets (PCP), color code packets (CCP), and pattern data packets (FDP).

page control paken) (PCP) is additional image information 1
It is transmitted prior to the transmission of a screen, and the data part includes page control code signals such as a program number (PR), page number (PA), and a code (, ED) indicating that the screen should be erased or updated. There is. color code bucket) (CC
P) is transmitted following the page control packet (PCP), and a color code (CC) indicating the color in which each character or unit division of the additional image information should be displayed is transmitted. Furthermore, the pattern data packet (FDP) is then transmitted continuously for one screen at a time (other packets may be inserted in the middle), and the data section contains additional image information to be displayed in the horizontal direction. The pattern data for each line when scanning is transmitted. Note that there are several other types of data packets, but their explanation will be omitted here.

In addition, the header section of every data packet contains a clock line signal (CR) for synchronizing the data sampling clock on the receiving side, and a clock line signal (CR) for synchronizing the data sampling clock on the receiving side.
A ramming code signal (FC), a service identification/interrupt control signal (SI/IN), and a data identification signal DI indicating which type of data packet the data packet is.

DI is being transmitted. Here, the FC signal is a signal capable of correcting a 1-bit error, and the FC signal is SI/IN.

Each signal of Dll, 1) I2 has one bit of error correction and two bits of error correction.
A Hamming code is used that can eliminate bit errors.

Therefore, the receiving device receives the transmitted television signal on which such an additional image information signal is superimposed, and
Take out the additional image information signal, select only the signal of the desired program using the page control packet (PCP), and select the color code data (CC) and pattern data in the color code packet (CCP) of that program. The pattern data in a packet (FDP) is stored in memory for one screen, and the image information is displayed on the screen by reading it out in synchronization with the screen scanning of the cathode ray tube and converting it into an image signal for display. You will be able to do so. Generally, a normal television receiver is also used to receive additional image information, and a circuit for processing the additional image information signal is added, and when displaying the received image information, a cathode ray Image information such as character information is displayed on the tube screen by superimposing the received image (moving image) of a normal television broadcast program, or by erasing the received image.

However, when receiving such binary-coded additional image information signals, processing the signals, storing them in memory, and reading them out from this memory to display the image information, the received television signals are subject to weak electric fields. If the image contains many noise signals or ghost signals, large waveform distortion will naturally occur in the superimposed additional image information signal. This makes it impossible to accurately receive and display the image information. For example, when transmitting image information using a pattern transmission method, the practical limit is an error rate of about 5x10' in bit units, and if the error rate is higher than this, erroneous display will become noticeable in the displayed image. It becomes very difficult to see and is not practical. However, since the pattern data signal is simply a scan of a pattern of image information, its own error rate cannot be easily detected.

Therefore, the present invention is capable of easily detecting whether the receiving condition of the additional image information signal is good or not, and is capable of detecting low-quality signals that often cause false indications when the error rate of the received signal is low under the above-mentioned bad reception condition. It is an object of the present invention to provide an additional image information receiving device that does not display image information.

Therefore, in the present invention, various control signals (for example, FC, SI/I
By focusing on the fact that signals that themselves have an error correction function (parity check function), such as encoded signals such as N, Dll, and DI2, are included, the number of errors within a certain period of time is counted. The present invention is characterized in that it detects the weight of the vehicle and prohibits display of the image information based on the received additional image information signal when the weight of the vehicle is above a predetermined erroneous weight.

EMBODIMENT OF THE INVENTION Hereinafter, the present invention will be described in detail with reference to the drawings showing one embodiment thereof. ,・ First, FIG. 2 is a block diagram showing the overall configuration of an embodiment of the present invention.

In the figure, 1 is a tuner, 2 is a VIP circuit, 3 is a video detection circuit, 4 is a chroma signal and video signal processing circuit, 5 is a synchronization separation circuit, 6 is a horizontal oscillation circuit, and 7 is a color subcarrier (fS
C) It is a reproducing circuit, and these 1 to 7 are similar to the circuit of a color television receiver. 8 is a circuit for waveform-shaping the video detection output signal and converting it into a binary code; 9 is a clock generation circuit for sampling the additional image information signal superimposed from the received television signal; 10 is a main memory 12 A microprocessor can be used in the processing circuit for writing and pushing out. 11 is a readout clock generation circuit for the main memory 12; 12 is a main memory that stores one screen worth of image information (color code CC and pattern data PD) in the received additional image information signal; 13 is a readout output of the main memory 12; and the output of the processing circuit 4, and 14 is a cathode ray tube (CRT) for display.The main parts of this apparatus will be explained with reference to FIG.

Note that parts corresponding to those in FIG. 1 are given the same reference numerals. Reference numeral 15 denotes a sampling circuit in the write/read processing circuit 10 of FIG. 1, which samples the data signal of the received information signal and converts it into an 8-bit parallel data signal for each byte. The latch memory 16 launches these 8 bits at once. The load pulse φ2 of the launch memory 16 is obtained by dividing the sampling clock φ1 applied from the write clock generation circuit 9 to the sampling circuit 1 into %, as shown in Figure 4. It is a frequency thing. The output of the latch memory 16 is used as the address of the 266-bit×6 ROM of the error correction circuit 17. Data in this ROM is written in correspondence with predetermined transmission data, and when an additional image information signal is received, 4-bit error correction output data is output, and 1-bit error correction output data is output when there is a data error. error detection output φ
Make sure to take out 3. The error correction data and the 8-bit received data from the 18th latch memory are sent to the R/
The control code signal is applied to the W processing circuit 10 and the main memory 12, the control code signal is decoded and processed, and the pattern data is written to the main memory 12.

Now, in the write clock generation circuit 9, the color subcarrier f8c
, and the received additional image information signal P shown in Fig. 4.
A sampling clock φ1 formed from the chronocline signal CRI up to T1 in O2 (however, the ringing waveform is used from T1 to T2) is used. At the 8th bit of the framing code FC, the FC detection circuit 18
(Performs 1-bit error matching. φ1 in Fig. 4 is T
The slight shift in phase before and after 2 indicates the result of this phase matching. The frequency dividing circuit 18 has a detection output φ.

After ' becomes high level, the clock pulse φ1 is frequency-divided by 8 to create load pulses φ2 and φ4.

The error detection output φ3 from the error correction circuit 17 is transmitted to the NAND gate 20 when there is a reception error in the received control code signal. These φ4゜φ. ' is at a high level, and the reception control signal M, which remains at a high level for 1H, is added from the R/W processor 10 as a program match detection output or a packet extraction instruction output, then the NAND
An error rate detection pulse φ6 is obtained as the output of the gate 20.

Therefore, the counter 21 counts this pulse φ5 by 4 m. In order to determine the counting time, the FC detection pulse φ. ′
The timer 22 counts 24 sub-periods during which the reception control signal φ6 is at a high level after one occurrence of , and the counter 21 is enabled to count only during that period. If a predetermined number or more, for example 10 or more, of error rate detection pulses are generated during that time, it is detected that the error rate of the received signal is greater than a predetermined value.

At that time, a clear output is generated and transmitted to the R/W processing circuit 1o to clear the contents of the main memory 2, so that the image information that is hard to see due to the received additional image information signal with many errors is not displayed on the screen.

-e, in the case of pattern transmission, the above-mentioned error rate of about 5×10 −3 is said to be the practical limit.

Although this pattern data PD itself is not error-corrected, the various control code signals J1''' (SI/IN, DI, , DI2, etc.) in each packet are error-corrected as described above. Considering the degree of improvement due to correction, it is said that even for received signals with the same S/N, the error rate after error correction is several tenths of one.

Therefore, if the load pulse φ is generated only for each SI/IN, DI, . If a code signal having error correction function is received, and ten error detection outputs are generated in the received code signal, this means that in bit units, 10 error detection outputs are generated.
/72x8=1. The error rate is η10. This is the value after error correction, and is 10% without error correction.
The error rate would be higher than 1.7 x 10-1, which is more than twice as high, and the result would be a malicious screen that is absolutely unbearable to look at. Such screens should not be displayed as described above. It is desirable.

Note that in the above example, the average value of the reception error rate over multiple fields of the superimposed additional image information signal is detected, but the same applies to the reception error rate of only 1 d of received signals, that is, one packet. can be detected.

For example, up to the data identification signal DI including the framing code signal FC, a maximum of four error detection outputs can be obtained for each node. Among them, the error detection output of the framing code signal FC includes the above-mentioned SI/IN and D.
The loading means may use a ROM as in the case of the I, DI, and signals, but it may also be constructed using a gate circuit as shown in FIG. That is, 8 8-person NAND gates 2
3 to 3o, originally aoa1a2a3a4a6a
6a7=11100101, the data of the received framing code signal that should be "1" is inverted one bit at a time, and is inputted from the sampling circuit 15, and these N
If any of the AND gates 123 to 30 generates an output of 1, it indicates that a 1-bit reception error has occurred.
If a 1" output is output, it means that a reception error of 2 or more bits has occurred. In this case, FC detection cannot be performed using the FC signal, which only has a 1-bit error correction function, and the packet cannot be detected. frame synchronization is not established, so this is out of the question.

Therefore, the output of the negative logic OR gate 31 is considered to be a 1-bit reception error, and the error detection output φ3 from the error correction circuit 17 is
The OR gate 32 forms a logical sum with the above, and the counter 21 counts the logical sum as described above. In this case, the output φ6 of the R/W processing circuit 10 is not supplied to the NAND gate 20, but is determined for all packets, and a total of four codes (FC, SI /IN
, Dll, DI, ), the output of the counter 21 is transmitted to the R/W processing circuit 1o, and the pattern data of the packet is controlled not to be written to the main memory 12. Also, each control code signal is not rewritten to the control code memory in the R/W processing circuit 10. Note that the counter 21 is controlled by the output of the flip-flop 33, which is cleared at the leading edge of each horizontal pulse and set at the trailing edge, and is cleared every horizontal period, so that the additional image information signal A count output is obtained only within the horizontal period in which the signals are superimposed. By doing the above, it is possible to reduce the erroneous display of data packets in the horizontal period in which the error rate is high in the received signal due to the additional image information signal, and it is possible to avoid displaying an image information screen that is difficult to see.

As described above, according to the present invention, it is possible to easily detect the reception error rate of the additional image information signal transmitted superimposed on the television signal, and the reception error rate can be easily detected when the electric field is weak or when there are many ghost signals. When the error rate of the received signal is higher than a predetermined value under bad conditions, display based on the received signal can be prohibited, thereby preventing low-quality and difficult-to-read displays that often result in erroneous displays. It is.

[Brief explanation of drawings]

FIG. 1 is a waveform diagram showing the transmission mode of teletext broadcasting. FIG. 2 is a block diagram of a teletext broadcasting receiving device according to an embodiment of the present invention. FIGS. 3 and 5 are detailed circuit diagrams of the same device. Fourth
The figure is the 11111th waveform diagram for explaining the operation. 1...Tuner, 2...VIF circuit,
3...Video detection circuit, 4...Chroma...
Video processing circuit, 8... Waveform shaping circuit, 9...
...Write clock generation circuit, 10...Write/read processing circuit, 11...Read clock generation circuit, 12...Main memory, #Reference= 13...
...Mixing/switching circuit, 14...CRT, 15.
... Sampling circuit, 16 ... Latte memory, 17 ... Error correction circuit, 18 ...
...Frequency divider circuit, 19...FC detection circuit, 20.
...NAND gate, 21...Counter, 22...Timer, 23-30...
NAND gate, 31...Negative logic OR gate,
32...OR gate, 33...Flip-flop. Name of agent: Patent attorney Toshio Nakao and one other person o-
c size ≧ ψ

Claims (2)

[Claims] (1) It is possible to receive an additional image information signal superimposed on a television signal by binary coding and transmitted, store the image information in a memory, and read it from the memory to display the image information. and a detection circuit for detecting the number of errors in the coded signal having an error correction function included in the received additional image information signal, and when the number of errors within a certain period of time exceeds a predetermined number. and a display prohibition circuit for prohibiting display of the image information being received. (2) As the detection circuit, a circuit that detects the number of errors in the additional image information signal for one horizontal period that is transmitted superimposed on the television signal is used, and as the display prohibition circuit, the number of errors mentioned above in one horizontal period is used. Claim 1 is characterized in that, when the number of images exceeds a predetermined number, the display based on the image information received during the horizontal period is prohibited.
Teletext broadcasting receiving device as described in .