JPH0193275A - Transmission and reception method for television control signal - Google Patents

Abstract

PURPOSE:To send a control signal to identify the television system with simple hardware constitution by sending a control signal to identify the TV system at a sufficiently lower transmission speed in comparison with that of a pseudo random signal series for a prescribed period of a pseudo random signal series so as to eliminate ghost. CONSTITUTION:A signal for one horizontal vertical blanking period is extracted by a signal extraction circuit 9 after a television signal is demodulated by a demodulation circuit 4. A ghost extraction circuit 8 uses a pseudo random signal series to eliminate the ghost. A shift register 22 is operated by the clock in the same frequency as the transmission speed of the control signal by a frequency divider circuit 21. The P/S flip-flop 23 is set by the detection of a start bit 1 and the control signal is outputted to a serial/parallel conversion circuit 25 through an AND gate 24. The flip-flop 23 is reset by the detection of stop bit 1 and the output to the conversion circuit 25 is finished. The control signal is outputted from the latch circuit 26 in the reset timing.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is a method for removing group delay distortion, frequency amplitude characteristic distortion, ghost, etc. that occur during the transmission of television signals, and at the same time for identifying television systems. The present invention relates to a television control signal transmission/reception method for transmitting control signals.

Conventional technology A ghost removal method using a pseudo-random signal sequence superimposed on the vertical retrace period of a television signal as a reference signal for ghost removal (hereinafter referred to as an OCR signal) will be described with reference to FIG. 31 is a pseudo-random signal train generation circuit;
32 is a signal superimposition circuit, 33 is a transmission system, and 34 is a ghost removal device. The pseudorandom signal string is sent to the signal superimposition circuit 3
2, it is superimposed on the vertical retrace period of the television signal. . The ghost removal device 34 uses this pseudo-random signal sequence to detect group delay distortion, frequency amplitude characteristic distortion, and ghosts generated in the transmission system 33, and performs ghost removal by determining the opposite transmission characteristics. This method has the feature that it can be used for digital data transmission using the pseudo-random signal sequence itself at the same time as ghost removal.

Problems to be Solved by the Invention By the way, a new television system (EDTV) is being considered that aims to improve image quality while maintaining compatibility with the current television system (NTSC).

In order to achieve high image quality, this E'D TV
Since it is desirable to perform ghost removal on the receiver side, it is necessary to send the above-mentioned OCR signal. Also, this EDT
Since V is transmitted on the same channel as current television broadcasting, it is a control signal for identifying whether it is EDTV or NTSC.

must be sent. Various methods can be considered for transmitting the above control signal, but the vertical retrace period It is considered most rational to insert the above control signal into the . - On the other hand, we have already inserted teletext signals, VITS signals, etc. during the vertical retrace period, and the above-mentioned OCR signal is also scheduled to be inserted, so we hope to make even more effective use of the vertical retrace period in the future. It is desired.

Therefore, simply inserting only the above control signal into the IH of the vertical blanking period cannot be said to be an effective use of the vertical blanking period. A method of inserting it into the period is being considered. In this method of using a pseudo-random signal string as the OCR signal, it is possible to allocate a part of the pseudo-random signal string to the control signal. However, in order to perform sufficient ghost removal over the entire signal component band of a television signal, a transmission speed that is at least twice as high as the highest frequency component is required. On the other hand, from the perspective of transmission quality, as the transmission speed increases, problems during data reproduction increase due to deterioration of the eye pattern caused by code amount interference, clock jitter, etc., and measures such as error correction and waveform equalization are required. This increases the burden on the hardware on the receiving side due to data reproduction. As a result, the data reproducing circuit becomes complicated. Currently, EDTV control signals require the equivalent of 5 to 7 bits, and it is reasonable for the hardware on the receiving side to be large and complex in order to reproduce data from control signals with this number of bits. Not.

Furthermore, in a receiving circuit that does not have a ghost removal means, the hardware for reproducing data of this control signal is required to be as simple as possible.

Means for Solving the Problems In order to solve the above problems, the television control signal transmission/reception method of the present invention superimposes a pseudorandom signal sequence as G C, R signals in the vertical retrace period of the television signal. In the ghost removal method, a control signal for identifying the television system is transmitted for a certain period of time at a transmission rate sufficiently lower than that of a pseudo-random signal sequence.

Effect of the Invention The present invention uses the above means to transmit a control signal for identifying a television system at a transmission rate sufficiently lower than that of a pseudo-random signal string for a certain period of time of a pseudo-random signal string superimposed on the vertical retrace period of a television signal. By doing so, it is possible to eliminate ghosts and at the same time transmit a control signal for identifying the television system with a simple hardware configuration without requiring means such as error correction and waveform equalization.

Embodiment FIG. 1 is a circuit diagram showing an embodiment of the television control signal transmission/reception method of the present invention. In Figure 1, 1 is a signal superimposition circuit, 2 is a modulation circuit, 3 is a transmission line, 4 is a demodulation circuit, 5 is a pseudo-random signal train generation circuit, 6 is a control signal generation circuit, 7 is a switching circuit, and 8 is a ghost removal circuit. 9 is a signal extraction circuit, 10 is a clock regeneration circuit, and 1) is a control signal regeneration circuit. The operation will be described below when the control signal has a fixed pattern. Pseudo-random signal string generation circuit 5
, the signal generated from the control signal generation circuit 6 is sent to the switching circuit 7.
are synthesized as a signal within one horizontal period according to the timing of . An example of this combined signal waveform is shown in FIG. This signal is superimposed on the vertical retrace period of the television signal by a signal superimposition circuit 1, modulated by a modulation circuit 2, and then sent to a transmission line 3. In this transmission path, the television signal is subjected to distortions such as group delay distortion, frequency amplitude characteristic distortion, and ghosting.

After this television signal is demodulated by a demodulation circuit 4, a signal of one horizontal period of the vertical retrace period is extracted by a signal extraction port 9. The ghost removal circuit 8 uses this pseudo-random signal sequence to perform ghost removal. - The force control signal is regenerated in the control signal regeneration circuit 1) at the clock timing regenerated by the clock regeneration circuit 10. FIG. 3 shows an embodiment of the control signal reproducing circuit in the case where the control signal is composed of 5 bits. A start bit "1" and a stop bit "1" are added before and after the control signal for synchronization. In FIG. 3, 21 is a frequency dividing circuit, 22 is a shift register, 23 is an R/S flip-flop, 24 is an AND gate, 25 is a serial/parallel conversion circuit, and 26 is a latch circuit. A control signal superimposed on the vertical retrace period is input from the signal sampling circuit 9 to the shift register 22 . The shift register 22 is operated by the frequency dividing circuit 21 using a clock having the same frequency as the transmission speed of the control signal.

Upon detection of the start bit "1", the R/S flip-flop 23 is set, and the control signal is outputted to the serial/parallel conversion circuit 25 through the AND gate 24. R/S flip-flop 2 upon detection of stop bit “1”
3 is reset and the output to the serial/parallel conversion circuit 25 is completed, and a control signal is output from the latch circuit 26 at the timing of this reset.

FIG. 4 shows, as a second embodiment, a control signal reproducing circuit in which the control signal is modulated using an M sequence. In FIG. 4, 27 is an identification circuit, 28 is a decoding circuit, and 29 is a dark value setting circuit. A dark value setting circuit 29 sets a dark value for determination. The control signal is compared with this dark value in the identification circuit 27 and binarized. Clock regeneration is performed in the clock regeneration circuit 10 using this binary output. The decoding circuit 28 operates with a clock having the same frequency as the transmission rate of the control signal from the frequency dividing circuit 21, decodes the M-sequence code, and outputs a control signal.

Next, the transmission speed of control signals will be explained.

This transmission speed is N/M of the transmission speed of the pseudo-random signal train.
(N, M: natural numbers), the sampling clock obtained in the ghost removal circuit 8 can be used for clock recovery of the control signal, and the clock recovery circuit 1
0, the configuration of the frequency dividing circuit 21 becomes simple.

As described above, according to this embodiment, control signals can be reproduced without increasing the scale of the hardware.

Effects of the Invention As described above, the present invention provides a ghost removal method in which a pseudo-random signal train is superimposed as an OCR signal during the vertical retrace period of a television signal, and the transmission rate is sufficiently lower than that of the pseudo-random signal train for a certain period of the signal. By transmitting a control signal for controlling the television, it is possible to remove ghosts and at the same time transmit and reproduce the control signal without complicating the hardware configuration for data reproduction on the receiving side. Although the control signal for identifying EDTV and NTSC has been described, it goes without saying that the present invention is not limited to this method, and the same applies to other methods.

[Brief explanation of the drawing]

Fig. 1 is a circuit configuration diagram of a television control signal transmitting/receiving circuit according to an embodiment of the present invention, Fig. 2 is a signal waveform diagram of a control signal and a pseudo-random signal train, and Fig. 3 is an embodiment of a control signal reproducing circuit. FIG. 4 is a circuit diagram of a second embodiment of the control signal reproducing circuit, and FIG. 5 is a circuit diagram of a conventional ghost removal method. ■...Signal superposition circuit, 2...Modulation circuit, 3...Transmission line, 4...Demodulation circuit, 5
...Pseudo-random signal string generation circuit, 6...
...Switching circuit, 7...Control signal generation circuit, 8.
... Ghost removal circuit, 9 ... Signal extraction circuit, 10 ... Clock regeneration circuit, 1) ...
...Control signal regeneration circuit, 21... Frequency division circuit,
22...Shift register, 23...R
/S flip-flop, 24...AND gate, 25...serial-parallel conversion circuit, 26
......Latch circuit, 27...Identification circuit,
28...Decoding circuit, 29...Threshold value setting circuit. Name of Agent: Patent Attorney Toshio Nakao Haka 1 Collection 2 Figure 3 Figure 1/ Figure 4/1 Figure 5

Claims (4)

[Claims] (1) A pseudo-random signal sequence is superimposed as a reference signal for ghost removal during the vertical retrace period of a television signal, and the transmission speed of the pseudo-random signal sequence is sufficiently lower than that of the pseudo-random signal sequence for a certain period of time to allow the television system to A television control signal transmission/reception method characterized by transmitting a control signal for identification. (2) The television control signal transmission/reception method according to claim (1), wherein the control signal has a fixed pattern. (3) The television control signal transmission/reception method according to claim (1), wherein the control signal is modulated using an M sequence or the like. (4) The television control according to claim (1), wherein the transmission rate of the control signal is N/M (N, M: natural numbers) of the transmission rate of the pseudo-random signal sequence. How to send and receive signals.