JPS6117436B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a receiving device that receives multiplex broadcasting in which information such as characters and graphics are inserted during the vertical retrace period, and the present invention relates to a receiving device that receives multiplex broadcasting in which information such as characters and graphics is inserted in the vertical retrace period. The aim is to stably receive multiplexed signals even for

In general, character multiplex transmission is known, in which information such as characters is multiplexed and transmitted during one horizontal scanning period of the vertical blanking period of a television signal, and the receiving side extracts that part and displays it on the television screen. There is. An example of this multiplexed information is shown in FIG. In the figure, during the one horizontal scanning period, Rum-in, which is the basic clock component of the information shown in Figure 2A, a code signal consisting of a fleming code (FC) indicating the beginning of information, and multiplexed information are transmitted. A service identification code (IDC) that specifies whether to be displayed on the same line on the television display screen, a pattern signal that is a combination of the check bit (IB) and information data, and a program code (PC) shown in FIG. Line code (RC) indicating which line of information it is,
Control signals such as color codes (CC) are appropriately combined and multiplexed. When receiving multiplex television signals such as characters, recording them in memory, etc., and displaying them on a monitor TV, the code of the multiplexed signal is detected after slicing the video signal to a constant width and then continuing. There is a method of recording information for a certain period of time, or a method of extracting only the multiplexed information part of the video signal and slicing it, detecting a code signal and recording the information. However, in the former case, there is a risk of a malfunction in which a general video signal is mistakenly detected and recorded as a code signal.
In addition, in the latter case, if the S/N is poor in a weak electric field,
Alternatively, if the amplitude fluctuations in the synchronization portion of the video signal are large, the circuit that generates the synchronization signal may not operate properly and the position of the pulse for extracting the multiplexed signal may fluctuate, resulting in the multiplexed signal not being extracted.

The present invention eliminates these drawbacks and provides a receiving device that can stably receive multiplexed signals. This will be explained below along with examples. In FIG. 1, 1 is a synchronization signal generation circuit, 2 is a clock generation circuit, 3 is a display timing generation circuit, 4 is a multiplexed signal extraction circuit, 5 is an S-P conversion circuit, 6 is a code signal detection circuit, 7 is a counter, 8
1 is a gate circuit, 9 is an input terminal to which a television video signal is input, and 10 is an output terminal to which data is output.

Next, the operation of this embodiment will be explained. Input terminal 9
As shown in Fig. 3a, the television video signal applied to
(Naturally, n = 20 is used as a natural number.)
Signals such as characters, figures, codes, etc. are multiplexed during the horizontal scanning period. This TV video signal is applied to the synchronization signal generation circuit 1, where the synchronization signal is separated, horizontal synchronization signal HD, vertical synchronization signal VD, and subcarrier.
SC is generated and output to the clock generation circuit 2 and display timing generation circuit 3. A clock generating circuit 2 synchronizes with the subcarrier and generates a clock having a frequency corresponding to the minimum bit of the multiplexed signal. In addition, the display timing generation circuit 3 is reset at the falling edge of the vertical synchronization signal, and is counted from the beginning of the equivalent pulse obtained by counting the horizontal synchronization signal (n-α).
th to (n+β)th (α, β are 0, 1, 2,...
The horizontal scanning period of .
Figure 3c shows that the clocks obtained by counting the clocks are at the "H" level during the period when multiplexed information exists within the horizontal scanning period.
A gated signal as shown in FIG. 3d is applied to the multiplexed signal extraction circuit 4 and used to extract the multiplexed signal. Here, the width of the pulse b is set to include a plurality of horizontal periods including an information multiplexing period in order to eliminate synchronization signal sampling errors. After slicing the signals such as characters outputted from the sampling circuit 4, the signal is sent to the S-P conversion circuit 5, where it is converted into an 8-bit parallel signal, and the code signal detection circuit 6 detects the signal at the beginning of the multiplexed signal within the horizontal scanning period. It detects a certain code and outputs a pulse that sets the counter 7. Furthermore, the counter 7 counts the pulses from the display timing generation circuit 3 and holds it at the "H" level until it reaches a certain pulse, and after the certain pulse is input, it keeps it at the "L" level until the code is detected again. Hold the level. The gate circuit 8 outputs the information from the S-P conversion circuit 5 only while the output of the counter 7 is "H". Therefore, after detecting the code that is the beginning of information, a certain number of bits of information such as characters and figures that follow are extracted. Therefore, all information can be output by making the counter constant slightly longer than the information bit.

As is clear from the above embodiments, according to the present invention, the multiplexed signal sampling period is set to a plurality of horizontal scanning periods before and after the horizontal scanning period in which multiplexed information exists. Even if the synchronization signal is slightly deleted due to the deterioration of /N, there is little error in extracting multiplexed information. Further, even if the phases of the vertical synchronizing signal and the horizontal synchronizing signal obtained from the synchronizing separation circuit change due to temperature changes or voltage fluctuations, and the sampling position of the multiplexed signal shifts between odd and even fields, it is not affected. Furthermore, by appropriately selecting the sampling position, it is possible to prevent the code signal and the video signal from being mistaken.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the main parts of a multiplex broadcast receiving apparatus according to an embodiment of the present invention, FIG. 2 is a schematic diagram of a multiplex broadcast signal, and FIG. 3 is a signal waveform diagram. 1...Synchronization signal generation circuit, 3...Display timing generation circuit, 4...Multiple signal extraction circuit, 8...
gate circuit.

Claims (1)

[Claims] 1. Receiving a signal in which information such as characters and figures is multiplexed together with a code signal indicating the start of such information in the n-th horizontal scanning period within the vertical blanking period of a television video signal. In the multiplex broadcast receiving apparatus, which has a separating means for separating a synchronization signal in the video signal and a extracting means for extracting a multiplexed signal, and displays the extracted multiplexed information on a screen.
A timing generating means is provided for generating a sampling pulse over the horizontal scanning period from the α)th horizontal scanning period to the (n+β)th horizontal scanning period, and the sampling means is controlled by the sampling pulse to separate the multiplexed information. Features of multiplex broadcast receiving device. 2. A signal sampling circuit that gates a television video signal using a sampling pulse obtained from a timing generating means as a sampling means, a detection circuit that detects a code signal indicating the beginning of information included in the signal, and a detection circuit that is controlled by this code signal to perform the sampling. 2. The multiplex broadcast receiving apparatus according to claim 1, further comprising a gate circuit for extracting only the information contained in the received signal.