JPS5810030B2 - Vertical blanking period program switching control method for broadcasting satellites - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a satellite broadcasting system in which program radio waves are sequentially transmitted from a plurality of program transmitting stations at different locations, and the transmitted radio waves are relayed by a broadcasting satellite to broadcast a television program. The present invention relates to a program switching control method within a vertical blanking period for broadcasting satellites that controls station switching.

In recent years, many countries around the world have begun trying out TV program distribution services using geostationary satellites.

However, the program switching control methods in these systems have to minimize the signal break to an extremely small level because a break in the broadcast radio waves (hereinafter referred to as a signal break) occurs when switching programs, and the synchronization signals for the previous and subsequent programs are different. However, the problem was that vertical distortion occurred on the TV screen.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a program switching control system within a vertical blanking period for broadcasting satellites that can eliminate signal breaks and vertical screen disturbances that occur on a television screen when switching programs.

In the vertical blanking period program switching control system for broadcasting satellites according to the present invention, the next program transmitting station determines whether the next program transmitting station The vertical alignment is determined according to the radio wave propagation time TB between the satellite and the broadcasting satellite.

Next, the previous program transmitting station transmits a program end notice signal (hereinafter referred to as a cue signal) a predetermined time Ds in advance so that the transmission stops immediately after the vertical synchronization signal,
The next program transmitting station receives this cue signal via the broadcasting satellite, and when the time Dr (=Ds - 2TB)) determined according to the radio wave propagation time Ts between the broadcasting satellite and the broadcasting satellite has elapsed, the next program is transmitted. Program radio waves are transmitted immediately after the vertical synchronization signal.

Next, the present invention will be described in detail with reference to the drawings showing one embodiment of the present invention.

Referring to FIG. 1, one embodiment of the present invention is comprised of a broadcasting satellite 10 and two program transmitting stations 20 and 30, where program transmitting station A 20 is the previous program transmitting station and program transmitting station 8 Station 30 will be described as a next program transmitting station.

The transmitting stations 20 and 30 have the same configuration, but for simplicity, the control system for transmitting station A 20 starts transmitting radio waves, while the control system for transmitting station A 30 stops transmitting radio waves. Each system is omitted.

In the transmitting station A 20, the television signal from the program transmitting source 21 is converted into an extremely high frequency band, for example, 14 GHz, and is transmitted from the antenna 22 toward the broadcasting satellite 10.

This signal is relayed by the satellite 10, for example 12GH
Since it is retransmitted by z, 8 transmitting stations 30 and 0 receiving stations 4
0, you can receive the program.

When ending the previous program from the transmitting station A 20, one cue signal is applied to the cue signal generator 23 before the end of the program.

The cue signal from the cue signal generator 23 is added to the cue signal superimposing section 24 and superimposed on the television signal from the program transmission source 21.

Various methods can be adopted as the format of the cue signal and the method of superimposing it on the television signal, but in this embodiment, 21H and 284H of the vertical blanking period of the television video signal are respectively erased and A method is adopted in which an FS format cue signal is superimposed on a combination of frequencies.

The cue signal superimposed on the television signal is detected by the cue signal detection section 25 and supplied to the Ds delay circuit 26.

Since the Ds delay circuit 26 has a delay time Ds, the queue signal is delayed by the time Ds and sent to the transmission switch 2.
7.

As a result, the program transmission from the transmitting station A 20 is stopped.

That is, the cue signal trigger is supplied and the time Ds actually elapses after the cue signal is superimposed on the television signal.
After the elapsed time, program transmission from the sending station A 20 is stopped.

The value of the delay time Ds is determined so that the program transmission is stopped immediately after the vertical synchronization signal of the television video signal.

That is, the cue signal is the television video signal 21H.
and 284H, the value of Ds is 2
The time from 1H and 284H to immediately after the vertical synchronization signal is determined to satisfy equation (1).

However, M is an integer of M≦1, and FH is the horizontal synchronization signal frequency.On the other hand, the television signal on which the cue signal is superimposed is relayed by the broadcasting satellite 10, and its frequency is, for example, 12
It is converted to GHz and retransmitted.

The retransmitted signal is sent to the next program transmitting station, transmitting station 30.
is received by the antenna 31 of.

The received signal is supplied to the cue signal detection section 32, where the cue signal is detected.

The detected cue signal is supplied to the Dr variable delay circuit 33, delayed by the delay time Dr, and sent to the transmission switch 3.
The next program television from the program transmission source 35 is driven by the synchronization signal of the synchronization signal generator 36, which is genlocked with a ψ phase delay with respect to the vertical synchronization signal of the television signal supplied to and received in advance. control to start transmitting the John signal.

At the beginning of transmission, the genlock control trigger
The genlock for the synchronization signal generator 36 is removed, and the synchronization signal generator 36 switches to the internal oscillator while maintaining the locked phase to generate a synchronization signal.

A method of setting the delay time Dr of the Dr variable delay circuit 33 will be explained with reference to FIG. 2.

Now, if the radio wave propagation times between the broadcasting satellite 10 and the transmitting stations 20 and 30 are TA and TB, respectively, then the transmitting station 2
In order for the time points of the stop of the transmitting radio waves from 0 and the start of the transmitting radio waves from the transmitting station 30 to coincide at the position of the broadcasting satellite 10, Dr=Ds-2Ts...・・・・・・
...(2) must hold true.

Equation (2) shows that by setting the delay times Dr and Ds based on the radio wave propagation time between the next program transmitting station 30 and the broadcasting satellite 10, overlapping (double illumination) and signal breaks occur when switching programs. It shows that there is no

That is, double illumination and signal breaks do not occur in the signal received at the receiving station 40.

Delay time Ds of the Ds delay circuit 26 of the previous program transmitting station 20
is set to a predetermined value so as to satisfy equation (1), and the delay time (Dr) of the Dr town variable extension circuit 33 of the next program transmitting station 30 is set as the delay time (Dr) from Ds to the transmitting station 3.
It is sufficient to set the value by subtracting the round-trip radio wave propagation time of 2 TB between 0 and the satellite 10.

Therefore, in the embodiment shown in FIG. 1, a radio wave propagation time generator 39 is mechanically connected to the antenna 31 and generates a signal representing a round trip radio wave propagation time of 2 TB according to the elevation angle value of the antenna 31. is provided.

The signal from this generator 39 is supplied to the Dr data generator 38, where the value of Dr is calculated from equation (2).

The calculated Dr value is set in the Dr variable extension circuit 33 from the Dr data generation section.

Next, a method for setting the vertical synchronization phase delay ψ will be explained with reference to FIG.

Now, if the phase delay of the vertical synchronization signal for the transmitting television signal with respect to the vertical synchronizing signal of the received television signal of the transmitting station B 30 is ψ, then since the transmitting station B 30 detects the cue signal, there is a Dr time delay. In order to cause the transmission to start immediately after the vertical synchronization signal of the transmitted television signal, the following must hold.

Rearranging equation (3) using equation (1) and mourning (2), where K is an integer of K=M-N>O, and ψ is the broadcasting satellite 1
By setting based on the radio wave propagation time TB between 0 and 0, it is shown that the vertical synchronization signals of the previous program and the next program are connected at the time of program switching.

That is, the receiving station 40 can receive a signal without screen holes even when switching programs.

The vertical synchronization phase delay ψ is 16.6
7m5. 16.68m5 for NTSC color signal)
A signal from the radio wave propagation time generator 39 that calculates the round trip radio wave propagation time of 2 TB between the transmitting station B 30 and the broadcasting satellite 10 is supplied to the ψ data generator 37, where ψ The data are calculated according to equation (4).

The calculated value of ψ is supplied from the ψ data generation section 37 to the synchronization signal generation section 36.

Based on the supplied value of ψ, the synchronization signal generator 36
A synchronization signal with a vertical synchronization phase delay ψ is generated with respect to the received television signal.

In the embodiment described above, the delay time Dr and the vertical synchronization phase delay ψ are used as the position information of the transmitting station B, and the satellite 1
The values of Dr and ψ are set based on the radio wave propagation time obtained from the elevation angle value of the antenna 31 with respect to 0. However, when the local station receives the cue signal transmitted by the own station, the values of Dr and ψ are determined based on the time difference, that is, the round-trip radio wave propagation time. It is also possible to determine and set the value.

In addition, the cue signals are 21- and 234H in the embodiment.
However, it may be superimposed at any position within the vertical retrace period.

Furthermore, although the phase synchronization of the next program transmitter was performed on a field-by-field basis, it may also be performed on a frame-by-frame basis.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram of an embodiment of the present invention, FIG.
FIG. 3 is a time chart for explaining the operation of the embodiment.

Claims (1)

[Claims] 1 In the satellite broadcasting system, in which radio waves are transmitted sequentially from the first and second program broadcasting stations at different points, and the transmitted radio waves are relayed by a broadcasting satellite to broadcast a television program, the first program broadcasting station uses a vertical synchronization signal. A program end notice signal is multiplexed and transmitted a predetermined time Ds to stop immediately after, transmission is stopped after the time Ds, and the second program transmitting station transmits the signal via the broadcasting satellite. Based on the synchronization signal from the first program transmitting station sent, the vertical synchronization phase delay ψ (ψ - same frequency N: integer, Ts: radio wave between the second program transmitting station and the broadcasting satellite) The program transmission source is operated based on the synchronization signal synchronized with the propagation time of
After receiving the program end notice signal from the program transmitting station,
A program switching control system within a vertical blanking period for broadcasting satellites, characterized in that transmission of the next program is started after a time Dr (Dr-Ds-2TB).