JPH05176319A - System for descrambling scrambled television signal - Google Patents

Abstract

PURPOSE:To prevent scrambled data from being easily descrambled by a person other than a specific contractor by extracting a synchronous(SYN) pattern signal during the period of a compressed vertical SYN signal and forming a horizontal SYN signal extracting window from the prescribed position of the extracted signal up to a position covering at least a horizontal SYN signal. CONSTITUTION:A SYN width information signal/SYN pattern information signal checking circuit is activated by a scrambling signal 1 and a horizontal SYN signal extracting window is generated from a horizontal SYN signal extracting window generating circuit (t1) 8 through a horizontal SYN signal extracting window position generating circuit 3 to execute descrambling operation. On the other hand, a descrambling signal is inputted to a horizontal SYN signal extraction detecting circuit 5 as an AND input together with an output from the circuit 3 to check whether a horizontal, SYN signal is or not. When the signal is not extracted yet, an output from the circuit 5 is inputted to the circuit 3 through circuits 6, 7 to determine the succeeding window position. The output of the circuit 5 is also inputted to a horizontal SYN timing signal generating circuit 9 and timing is generated from the circuit 9 and inputted to a horizontal SYN signal extracting window signal (t2) generating circuit to generate a signal (t2).

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a descramble system for scrambled cable television (CATV) information.

[0002]

2. Description of the Related Art In recent years, the services of general terrestrial television broadcasting have been unable to meet the recent diversification of the needs of viewers because their channels are limited by the width of the broadcasting band. The number of viewers who subscribe to a CATV system using a cable network is increasing.

The current CATV system is an urban CAT.
The market is expanding centering around a system called V system, and in this system, pay service is provided only to a specific contractor. The problem with paid services is that they are highly confidential, and for that reason image information is scrambled.

Next, an example of a conventional scramble descramble system will be described with reference to FIG. The CATV system of this conventional example shows, as an example, a CATV system in which a transmitting side and a receiving terminal side are connected by a cable network.

In the conventional example, a synchronous compression system (sync suppress system) scramble for compressing and transmitting the synchronization information in the standard television signal, that is, the horizontal synchronization signal and the vertical synchronization signal is adopted. FIG. 7 shows a waveform during a vertical blanking period of a television signal subjected to sync suppress. As shown in FIG. 7, the sync width information signal and the sync pattern information signal are inserted in the vertical blanking period of the sync suppressed television signal. The key data signal is omitted because it is not directly related to the present invention.

First, the sync width information signal A, which continues for a minute time from the compressed horizontal sync signal, is a specific sine wave signal having a video band frequency, and its time length is set to be constant.

A synchronization pattern information signal B (detected by the window W ₁ ) is provided after a slight time from the synchronization width information signal A (detected by the band pass filter). The first bit signal B'of this synchronization pattern information signal
Is used as a marker signal, and the compressed horizontal synchronizing signal after T ₁ is detected using the marker signal as a reference point. Also,
By comparing the synchronization pattern extracted from this synchronization pattern information signal with the data stored in the receiving terminal side, this information is distinguished from noise and other video signals, and it is determined that there is no error in the synchronization information. Technically, it is also possible to reproduce the sync signal only by the sync width information without the sync pattern information signal. However, in this case, it is necessary that the fluctuation of the synchronization width information signal on the time axis can be regarded as substantially zero. Further, in FIG.
₂ is the regular sync signal interval.

[0008]

However, in the above-described conventional example, since the position of the signal B'of the leading bit of the synchronization pattern information signal B is constant, the position of the signal B'of the leading bit is once. Is detected, the disadvantage of being relatively easy to create a descrambled system is unavoidable.

An object of the present invention is to eliminate this drawback and to provide a scramble descrambling method in which a person other than a specific contractor is more difficult to descramble than the conventional example.

[0010]

In order to solve the above-mentioned problems, the present invention forms a window by extracting a sync pattern information signal by detecting a sync width information signal during a compressed vertical sync signal period and performing synchronization. The horizontal synchronization signal is detected by extracting the pattern information signal and forming a horizontal synchronization signal extraction window from the predetermined position to at least a position covering the horizontal synchronization signal.

Further, the horizontal sync signal sampling window is slid to detect the position of the horizontal sync signal, and the relatively long one window in which only one horizontal sync signal is included in the horizontal sync signal sampling window is used. The position of the horizontal synchronizing signal is detected.

[0012]

On the receiving side, a window for extracting the synchronization pattern information signal by detecting the synchronization width information signal in the compressed vertical synchronization is formed to extract the synchronization pattern information signal, and at least the horizontal synchronization signal is extracted from the predetermined position. Since the horizontal sync extraction window is formed up to the cover position, even if the position of the marker signal of the first bit in the sync pattern information signal is slightly shifted forward or backward on the transmitting side to enhance the confidentiality of the scrambled TV signal, It can be descrambled reliably on the side.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows an embodiment of the present invention, and is an operation diagram in which a waveform diagram of a scrambled television signal is also shown. In this embodiment, the vertical and horizontal sync signals are compressed from the standard television signal to superimpose or insert the sync width information signal a and the sync pattern information signal b, and the marker signal B '( This is carried out when the position of the horizontal synchronizing signal of the scrambled television signal is slightly moved back and forth (see FIG. 7).

FIG. 2 is a flow chart for explaining the detection of the horizontal synchronizing signal position with reference to the lower part of FIG. 1, and the operation of this chart will be described below with steps abbreviated as S and written in parentheses. First, as shown in FIG. 1, a sync width information signal a is detected and detected from a scrambled television signal on which the sync width information signal a is superimposed by using a bandpass filter or the like, and a sync signal having the same width is detected. Create a pulse (S1),
As a result, a sync pattern information signal sampling window is generated (S2), and the sync pattern information signal is sampled (S3).
If the synchronization pattern information signal is reliably extracted (S
4) Generate a horizontal synchronization signal sampling window H _W (FIG. 1) of width t ₁ (S5), and if the horizontal synchronization signal can be sampled (S6), the horizontal synchronization signal extracted for 1 horizontal time after counting the T _'2, it is generated in the same manner and S5 windows withdrawal horizontal synchronizing signal (S7).

When the position of the horizontal synchronizing signal extracted in S6 is inappropriate for the descrambling position, the counter value for determining the horizontal synchronizing signal extracting window position is also shown in the lower part of FIG. The number is increased along with the image field (S8), and the operation from S1 is repeated until the horizontal synchronizing signal is extracted. Thereafter, as described above, T 'after _two counts,
A horizontal synchronization signal sampling window t ₂ is generated (S7).

FIG. 3 is a block diagram of an apparatus for detecting the horizontal synchronizing signal position as described above by sliding the sampling window. The synchronization width information signal / synchronization pattern information signal check circuit 2 is operated by the scramble signal 1,
After passing through the horizontal sync signal sampling window position generation circuit 3,
The horizontal synchronizing signal sampling window is generated in the horizontal synchronizing signal sampling window generating circuit 8 to perform the descrambling operation. On the other hand, the descramble signal 4 is AND-inputted to the output of the horizontal sync signal sampling window position generating circuit 3 and the horizontal sync signal sampling detection circuit 5, and it is confirmed whether the horizontal sync signal can be sampled by the descramble processing. If the horizontal sync signal is not detected, it is input to the horizontal sync signal sampling window position generation circuit 3 via the horizontal sync signal sampling window slide amount generation circuit 6 and the horizontal sync signal sampling window preset counter 7. The window position in the next field is determined by increasing the window slide amount or the number of counts by a certain amount. The output of the horizontal sync signal sampling detection circuit 5 is input to the horizontal sync timing signal generation circuit 9 to generate timing (T ' ₂ ) and to the horizontal sync signal sampling window generation circuit 10 to generate t ₂ . To do.

FIG. 4 is an operation diagram additionally showing a waveform diagram for explaining another embodiment of the present invention. This embodiment, the time from the trailing edge of the synchronization pattern information signals by way of example a narrow window width t ₁ of FIG. 1 to the first horizontal synchronizing signal, a horizontal synchronizing signal position by sliding the window width t ₁ while determining the width t _'1 in which the first-th horizontal synchronizing signals so long as only comprising one as a window width, except for creating a horizontal synchronizing signal extraction window, others 1 The description of is used.

FIG. 5 is a flowchart of FIG. 4, in which the sync width information signal is detected (S11), a sync pattern information signal sampling window is generated (S12), and the sync pattern information signal is sampled (S13). ), when it is done correctly (S14), t _'1 for setting the horizontal synchronizing signal extraction window (S15), extraction of the horizontal synchronizing signal (S16), if not better sampling repeated operation of S1 to , If the horizontal sync signal is extracted well, after that, as in FIG.
After counting T ″ ₂ , a horizontal sync signal sampling window of t ′ ₂ is generated (S17).

FIG. 6 is a block diagram of the apparatus of the second embodiment. The scramble signal 12 is applied to the horizontal sync signal sampling window (t ′ ₁ ) generation circuit 14 via the sync width information signal / sync pattern information signal check circuit 13 to create the horizontal sync signal sampling window t ′ ₁ . It becomes the horizontal sync signal sampling window. Window t sampling a horizontal synchronization signal _'1 is and input to descrambling signal 15 and horizontal synchronizing signal extraction detecting circuit 16, via a time T _"2 horizontal synchronizing timing generation circuit 17, sampling a horizontal synchronization signal window (t' ₂ ) was added to the generating circuit 18 'generates a _second window, the window t sampling a horizontal synchronization' t is output as _2.

The present invention detects the horizontal synchronizing position as described above.

[0021]

As is apparent from the above description, the present invention is attracting attention in the information society because the horizontal sync signal position of scrambled television information is detected with an extremely simple structure. C that needs to be kept secret
It is extremely effective in descramble processing of ATV signals and the like.

[Brief description of drawings]

FIG. 1 is a waveform diagram showing a first embodiment of the present invention.

FIG. 2 is a flowchart showing an operation of the first embodiment.

FIG. 3 is a configuration diagram of the device.

FIG. 4 is a waveform diagram showing another embodiment of the present invention.

FIG. 5 is a flowchart showing the operation of the same embodiment.

FIG. 6 is a configuration diagram of the same device.

FIG. 7 is a waveform diagram showing an example of a conventional television signal scramble process.

[Explanation of symbols]

a ... Sync width information signal, b ... Sync pattern information signal,
T ... Horizontal sync signal sampling window.

Continued Front Page (72) Inventor Harumasa Kajita 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (3)

[Claims] 1. A descrambling method of a scrambled television signal in which a sync signal is compressed and a sync width information signal, a sync pattern information signal and a key data signal are superimposed, and the sync width is in a compressed vertical sync signal period. Horizontal synchronization is performed by forming a window for detecting the information signal and extracting the synchronization pattern information signal, extracting the synchronization pattern information signal, and forming a horizontal synchronization signal extraction window from the predetermined position to at least a position covering the horizontal synchronization signal. A descrambling scheme for scrambled television signals, characterized by detecting the signal. 2. The descrambling method of the scrambled television signal according to claim 1, wherein the horizontal sync signal sampling window is slid to detect the horizontal sync signal position. 3. The scrambled television signal according to claim 1, wherein the horizontal sync signal position is detected by a relatively long window in which only one horizontal sync signal is included in the horizontal sync signal sampling window. Descrambling method.