JPS6277730A - Timing information transmission system - Google Patents

Abstract

PURPOSE:To make the descramble start timing accurate at the reception side even when a time deviation is caused to a signal on a transmission line by sending a scramble timing signal in a form of a voice packet frame just after video image frame pulse. CONSTITUTION:A scramble trigger pulse S sent asynchronizingly is latched by using a video frame pulse VF1 and a scramble timing signal is sent to the next packet frame FP1 starting from a packet frame pulse PF1. On the other hand, as to the voice scramble, the packet frame FP2 of the packet frame FP1 on which a timing signal is sent is scrambled. Further, the video scramble is initiated from the video frame starting from the 1st video frame signal VF2. When the reception side receives the scramble timing signal corresponding to the scramble at the transmission side and the voice descramble is started from the next packet frame and the video descramble is started from the video frame just after.

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention provides a method for transmitting a television signal by scrambling the video signal and the audio signal when transmitting the signal via a broadcasting satellite or the like. This invention relates to a method for transmitting a scramble timing signal that indicates the timing of a scramble timing signal.

[Conventional technology] When performing paid broadcasting through television satellite broadcasting, or when transmitting program materials via a satellite communication transmission path, the video and audio signals are scrambled to conceal the program contents. and transmit it.

FIG. 3 shows an overview of a conventionally known scrambling system.

In order to realize a scrambling method that is highly confidential and difficult to restore illegally, a pseudorandom signal (hereinafter referred to as a PN signal) generated by a pseudorandom noise generator 1 (hereinafter referred to as a PN generator) is generally used. ) using
A scrambler 2 scrambles the video signal and audio signal.

On the receiving side, a PN generator 1' similar to that on the transmitting side generates the same PN signal as on the transmitting side, and the PN signal is used to convert scrambled video and audio signals sent from the transmitting side. is descrambled by a descrambler 2' to restore the video signal and audio signal.

PM generators 1 and 1' can generally be configured with a shift register and a feedback circuit, and the initial value of the shift register and
If the initial values are loaded into the registers at the same timing, the same PN signal series will be generated.

Therefore, in order to correctly restore the original video and audio signals on the receiving side, it is necessary for the transmitting side to multiplex the information on the initial value of the PM generator and the load timing onto the broadcast radio wave 3 and send it in real time. be.

In FIG. 3, reference numeral 4 denotes an encryption device, which negotiates information such as the initial value of the PM signal, the broadcasting station, the broadcast date, and the program into an encryption code. 4' is a decryption device corresponding to the encryption device 4, which decodes the encryption code from the transmitting side and sends it to the PM generator 1.
′ is controlled.

The present invention relates to a transmission system for a timing signal that provides this load timing. Conventionally, the timing signal was transmitted in the following manner.

FIG. 4 is a diagram showing an example of a signal format of the PCM audio transmission system in television satellite broadcasting.

In FIG. 4, an independent data area (480 bits) and an empty area where audio is not multiplexed, such as a control area, can be used as data channels for sending various data signals.

The data transmission method on the data channel is as follows:
A packet transmission method with excellent flexibility and expandability.The length of the data packet is, for example, a teletext data packet (272 bits) that is included as is, and 32
It is convenient to use 288 bits, which is a multiple of . When the length of the data packet is 288 bits, the beginning of the data packet and the beginning of the audio frame match every 9 mg no matter what the time width of the data channel area is. The reason for this is that, for example, multiplying the independent data portion's 480 bits by 9 gives 4320 bits, which is 15 times the packet length of 288 bits and is a divisible number.

That is, during period IIIS, 15 data packets can be transmitted while transmitting 9 frames of 9 mg of audio frames containing 2048 bits, and every 9 frames, the first beat 2 of the data packet is the beginning of the independent data area. Located in

Therefore, if a data packet synchronization signal is sent at a timing of every 9 mg so that the beginning of the data packet has a certain positional relationship with the beginning of the audio frame, the beginning of the data packet can be accurately captured. This synchronization signal is defined as a packet frame pulse.

Packet frame pulses can be sent using empty bits among the 16 bits of the control signal in the signal format shown in FIG.

FIG. 5 is a diagram showing the signal format of a 16-bit control signal. In the figure, the 6th bit to the 15th bit of the control signal are not used, so for example, the 15th bit is used as the packet frame. Can be used as a pulse.

The initial value of the data given to the PN generator 1.1', along with program-related information, etc., is sent to the data channel in the 480-bit independent data area shown in Figure 3 in the form of the data packet described earlier. .

On the other hand, a timing signal (hereinafter referred to as scramble timing) for loading initial values into the registers of the PN generators t and t' is multiplexed with the video signal or the audio signal and transmitted. FIG. 6 shows the operation when such a conventional scramble timing signal is multiplexed with a video signal and transmitted.

(1) As shown in Fig. 6, the scramble trigger pulse S sent in an asynchronous state is converted into a video frame pulse VF.
, and place a scramble timing signal within that video frame. The scramble timing signal starts from, for example, one video frame of the signal VF2 in the digital synchronization signal of the video signal.

(3) Scrambling of the audio signal is performed using the packet frame signal PF immediately after the scramble timing signal S'.
Start with 1 packet frame.

When the receiving side receives the scramble timing signal, it starts descrambling the video signal from the next video frame to correspond to the scrambling on the transmitting side, and starts descrambling the audio signal from the packet frame immediately after the timing signal. Start descrambling.

In this conventional method, it is impossible in principle to make a mistake in the start timing of descrambling the video signal on the receiving side. However, for audio signals, when the margin m1 or m2 shown in FIG. An error occurs in which the start timing is shifted earlier or later by one packet period, that is, 9 ms. If there is a strict synchronization relationship between the video signal and audio signal even if they are sent on different channels, this type of error will not occur, but in general, video signal frames and audio signal frames are treated as asynchronous. is being transmitted, and the margins ml and m2 are, in the worst case,
It is possible that it will become zero.

[Problems to be Solved by the Invention] As explained above, the conventional scramble timing signal transmission method ↑ has the drawback that descrambling is started at the wrong timing with respect to the audio signal.

SUMMARY OF THE INVENTION An object of the present invention is to provide a scramble timing signal transmission system that solves the drawbacks of the prior art and allows the receiving side to start descrambling at the correct timing.

[Means for Solving the Problems] In order to eliminate the drawbacks of the conventional example as established above, the present invention provides for scramble timing signals to be transmitted by PC when transmitting video signals and PCM audio signals in a scrambled manner.
The audio signal is scrambled from the packet frame next to the packet frame period, and the video signal is scrambled from the video frame next to the video frame signal in which the scramble timing signal exists. The receiving side receives the scramble timing signal, and the audio signal starts from the next packet frame of the packet frame period in which the scramble timing signal exists, and the video signal starts from the video frame next to the video frame signal in which the scramble timing signal exists. The scramble timing signal is superimposed on the PCM audio signal and transmitted so that the PCM audio signal is descrambled from the PCM audio signal.

[Function] In the present invention, when transmitting a scramble timing signal using one bit in a control code, a scramble trigger signal is once latched with a video frame signal, and then one audio packet frame is latched in the first audio packet frame. By sending out a scramble timing signal for one period, and starting scrambling for an audio signal from the next packet frame, and starting scrambling for a video signal from the first video frame thereafter, the transmission path and signal processing To prevent descrambling start timing from being mistaken on a receiving side even if a time lag occurs between a video signal and an audio signal in a system.

[Example] The present invention will be described in detail below with reference to nine drawings.

FIG. 1 is a diagram showing a timing chart of a transmission method of a scramble start timing signal according to the present invention.

(1) First, as shown in FIG. 1, the scramble trigger pulse S sent in an asynchronous state is latched with the video frame pulse VFl.

(2) Send a scramble timing signal to the next packet frame FPt starting with packet frame pulse PF1. At that time, the scramble timing signal is
By using the empty bits of the control code in the figure, for example, set all the 13th bits of the control code in the packet frame to 1.
Make it. Therefore, in this example, since there are nine audio frames, nine pulses rise.

(3) Audio scrambling is performed on the next packet frame FPs of the packet frame FPs that sent this timing signal.
Start from 2.

(4) Video scrambling starts from the first video frame after this, that is, the video frame starting with the video frame signal VF2.

When the receiving side receives a scramble timing signal corresponding to the scrambling on the transmitting side, it starts audio descrambling from the next packet frame, and starts video descrambling from the video frame immediately after that.

Since descrambling is performed in this manner, in the present invention, there is no possibility that the receiving side will make a mistake in the timing of audio descrambling. Also, regarding the video signal, considering the margins m1 and m2 in Fig. 1, m1 = Fp + x ≧ Fp m2 = Fv - Fp -x ≧ Fv - 2 Fp where, Fv = 33.3 (ms), Fp = 9 (ms)
Therefore, ml≧9 (ms), m2≧15.3 (m
s). ml and m2 are margins for positional deviation of the scramble timing signal due to the time difference between video and audio that occurs in the transmission path and the signal processing system.

Therefore, in the present invention, even if there is a time difference between video and audio, the margin m1. Since the value of m2 is sufficiently large, there is no possibility of making a mistake in the timing of starting video descrambling.

FIG. 2 is a logic circuit diagram showing the configuration of an embodiment of the present invention.

In Figure 2, 11, 12, 13, 14. 15, 11
3, 17, and 18 are D-flip-flops, respectively, and 19 is an AND circuit. In each of the D-flip-flops 11 to 18, GK is a clock input terminal,
CLR is the clear terminal, in is the input terminal, Q is the output terminal,
Wataru is an inverted output terminal. Vcc is a constant voltage input terminal. ! 1 is a scramble trigger input terminal, ■2 is a video frame pulse input terminal, 3 is a packet frame pulse input terminal, ■4 is an audio frame pulse input terminal, Ol is a video scramble timing signal output terminal,
02 is a scramble timing signal output terminal, and 03 is an audio scramble start timing signal output terminal.

Next, this operation will be explained.

First, when the scramble trigger signal S shown in FIG. 1 enters the clock terminal GK of the first D-flip-flop 11 from the scramble trigger signal input terminal It is latched and further supplied from the output terminal Q to the input terminal in of the second D-flip-flop 12.

When the video frame pulse VF shown in FIG. 1 enters the clock terminal GK of the second D-flip-flop 12 from the video frame pulse input terminal 2, the previous scramble trigger signal is synchronized with the video frame pulse VF1. The output terminal Q of the second D-flip-flop 12 is also taken out as a high-level pulse. At the same time, the output of the inverted output terminal Page is applied to the clear terminal CLR of the first D-flip-flop 11,
D-flip-flop 11 is cleared.

The output of the second D-flip-flop 12 is branched, one is latched by the third D-flip-flop 13, and then outputted from the fourth D-flip-flop 14 as a video scramble start timing signal. . This video scramble start timing signal is output from output terminal 0. and supplied to the scrambler 2 shown in FIG.
As shown in FIG. 1, scrambling of the video signal is started.

The other output of the branched second D-flip-flop 12 is latched by the fifth D-flip-flop 15,
Further, it is transferred to the sixth D-flip-flop 1B.

The sixth D-flip-flop 1e is triggered by the packet frame pulse PFI shown in FIG. 1 from the input terminal I3, and outputs an output signal synchronized with the packet frame pulse. 6th D-flip-flop 1B
The output of is supplied to the AND circuit 18, where it is logically ANDed with the audio frame pulse from the input terminal I4 to produce the scramble timing signal shown in FIG. 1, and taken out from the output terminal 02. This scramble timing signal is
For example, it is inserted into the 13th bit of the audio channel control signal and transmitted.

The output signal synchronized with the voice packet frame pulse from the sixth D-flip-flop 1B is further transmitted to the seventh D-flip-flop 1B.
- It is latched in the flip-flop 17 and transferred to the eighth D-flip-flop 1B. In the eighth D-flip-flop 18, the packet frame pulse PF2 is triggered by the packet frame pulse PF2.
An audio scramble start timing signal synchronized with is generated and taken out from the output terminal 03. This audio scrambling start timing signal starts scrambling the audio signal as shown in FIG.

As described above, the generation and transmission of the scramble timing signal of the present invention as shown in FIG. 1 is performed by the circuit shown in FIG. 2.

In the above embodiments of the present invention, an example was explained in which the packet length was 288 bits, but it goes without saying that other packet lengths may be used as long as the values of margins m1 and m2 are sufficiently large.

The method of the present invention can also be used for signal processing other than scrambling both video and audio signals of satellite broadcasting.

[Effect of the invention] In the conventionally considered method, the margin is m1.

There were cases where the value of m2 became zero, and if the transmission path delay or signal processing time was different for video and audio, there was a drawback that the audio descrambling start timing could be easily misjudged.
In the transmission method of the present invention, the scramble timing signal is transmitted in the audio packet frame immediately after the video frame pulse.
For example, since the data is continuously transmitted for 9 seconds, the margin m1. The value of m2 can be made sufficiently large. That is, even if the position of the timing signal is slightly shifted from the video signal on the receiving side, the descrambling start timing will not be incorrect.

Furthermore, according to the present invention, even if the video and audio are asynchronous, it is possible to accurately send the descrambling start timing for both the video and audio using one bit of the control code. Furthermore, the point at which scrambling begins is shifted by a maximum of 24.3 S between video and audio, but this is a sufficiently small value.

[Brief explanation of drawings]

Fig. 1 is a timing chart of an embodiment of the scramble timing information transmission method of the present invention, Fig. 2 is a logic circuit diagram showing an embodiment of the scramble timing information transmission method of the invention, and Fig. 3 is a general scramble system. Figure 4 is a diagram showing the signal format for PCM audio transmission in satellite broadcasting, Figure 5 is a diagram showing the control code format for PCM audio transmission, and Figure 6 is the conventional scramble timing information transmission method. This is a time chart. 1.1'...PN generator, 2.2'...Scrambler, 3...Broadcast radio waves, 4...Encryption device, 4'...Decryption device, 11-18...・D-flip-flop ・18...AND circuit. Patent applicant Japan Broadcasting Association representative
Person Patent Attorney Yoshi Tani - Union] Figure 5 to Tachibana of your sign Figure 6

Claims (1)

[Claims] When transmitting a video signal and a PCM audio signal in a scrambled manner, a scramble timing signal is superimposed on the PCM audio signal and transmitted over one packet frame period,
The audio signal is scrambled and transmitted from the next packet frame of the packet frame period, and the video signal is scrambled and transmitted from the video frame next to the video frame signal in which the scramble timing signal exists, and the receiving side receives the scramble timing signal, The scramble timing is such that the audio signal is descrambled from the next packet frame of the packet frame period in which the scramble timing signal is present, and the video signal is descrambled from the video frame next to the video frame signal in which the scramble timing signal is present. A timing information transmission method characterized by transmitting a signal superimposed on a PCM audio signal.