JPS6117395B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for transmitting additional information in television signals, and allows the additional information signal to be transmitted and received with a simple circuit configuration without affecting conventional television receivers in any way. The purpose is to do so.

Conventionally, as a means of superimposing other additional information on a television signal, a method has been used in which horizontal and vertical retrace periods are mainly utilized and information is inserted therein.
However, it has been pointed out that this method requires a complicated circuit for information extraction, and that it is difficult to send sufficient data without adversely affecting the image information on the television. On the other hand, attempts have been made to transmit additional information using color burst signals, and a method has been proposed in which an audio PCM signal is transmitted by amplitude modulating a color burst signal, as shown in Figure 1. .

(E.ADLER et.al.; Integration of Sound
Signals into the Video Signal for TV
Transmission, Electrical Communication,
(Vol. 49, No. 31974) However, such a method based on amplitude modulation of color burst signals makes it impossible to correctly reproduce a color image with a general receiver, and is completely incompatible. Furthermore, in the color burst signal shown in Fig. 2b obtained by passing the amplitude-modulated color burst signal shown in Fig. 2a through a limiter circuit, the pulse width of the extracted signal is determined by the amplitude of the superimposed signal. Since the subcarrier changes, there are problems such as not being able to detect the phase with the reference subcarrier as it is, and methods such as amplitude modulation are inappropriate for signals that require minute phase information such as color bursts. You can say that.

The present invention has been devised in consideration of these problems of conventional additional information transmission methods, and provides a means for easily transmitting and receiving additional information without generally affecting the receiver at all. It is. The present invention will be described in detail below based on embodiments with reference to the drawings.

FIG. 3 shows a transmission signal waveform when information is transmitted by modulating the number of color burst signals according to the present invention. First, on the transmitting side, as shown in Figure a, the horizontal synchronizing signal covers almost the entire back porch.
Prepare a 12-cycle standard color burst signal. Next, the last few cycles of the reference color burst signal are deleted using the gate signal G shown in FIG. 2B whose pulse width changes in accordance with the additional information signal, and the modulated color burst signal shown in FIG. A television signal as shown in d of the same figure is transmitted superimposed on the back porch of the synchronization signal. however,
Since the color burst signal must have at least eight cycles, it is the last four cycles of the reference color burst signal that are actually modulated.
The gate signal G corresponding to the additional information signal can be easily obtained by sequentially setting the additional information signal to the input terminal of a preset counter or parallel input shift register. In the embodiments described above, modulation is performed by deleting the rear part of the color burst signal depending on the signal, but it is also possible to perform this on the front part of the color burst signal.

Next, on the receiver side, as shown in Fig. 4, the burst separation amplifier circuit 1
The color burst signal b is extracted and input to the phase detection circuit 2, and at the same time, the level converter 6 obtains a TTL level burst signal c. At this time, the burst gate pulse e applied to the burst separation amplifier circuit 1 must have a pulse width sufficient to extract a maximum of 12 cycles of burst signals. The burst signal c obtained by the level converter 6 is applied to the clock input of a counter 8, and the counter 8 detects the number of cycles of the burst. Since the horizontal synchronizing pulse d converted to TTL level by the level converter 7 is applied to the clear input terminal of the counter 8, the counter 8
The number of cycles of the color burst signal for each horizontal scanning period is output to the parallel output terminal of . The value is held until the next horizontal scanning period (approximately 60 .mu.S), thereby allowing the sent additional information to be obtained. If a binary counter is used as the counter, it is possible to easily detect a change in the number of cycles (5 levels) of a color burst signal of 8 to 12 cycles by simply focusing on the output of the lower 3 bits. Since there are 525×30=15.750 horizontal scanning periods in one second, even if two bits of information are sent in each horizontal scanning period, it is possible to send information equivalent to about 30K bits per second.

The output of the phase detection circuit 2 is applied to a voltage controlled oscillator (VCO) 4 via a filter 3, and the 3.58MHz subcarrier output generated here is applied to a phase shifter 5.
The signal is supplied to each color demodulation circuit as a reference subcarrier for the demodulator through the subcarrier as in a conventional color receiver.

As described above, by using the additional information transmission method according to the present invention, it is possible to obtain information other than images and sounds on a television receiver by simply adding a simple circuit, and it is also possible to obtain information other than images and sounds on a television receiver, and it has no effect on conventional receivers. It does not have any negative effects.

[Brief explanation of the drawing]

Figure 1 is a diagram showing a part of the television signal when the color burst signal is amplitude-modulated, Figure 2 is a partially enlarged diagram of the color burst signal in Figure 1 and a signal extracted from it through a limiter circuit; FIG. 3 is an explanatory diagram of a modulated color burst signal according to the present invention, and FIG. 4 is a block diagram showing an embodiment of a circuit for detecting additional information according to the present invention. 1... Burst separation amplifier circuit, 2... Phase detector, 4... VCO, 6, 7... Level converter, 8
……counter.

Claims (1)

[Claims] 1. An information transmission system using a television signal, characterized in that other information is added to the television signal and transmitted by digitally modulating the number of insertion cycles of a color burst signal in the television signal.