JP2857413B2 - Television signal scrambling method and descrambling method and apparatus - Google Patents

Description

Description: FIELD OF THE INVENTION The present invention relates to a method for scrambling a television signal and a scrambled television for disabling viewing by a subscriber other than a specific viewing subscriber in a CATV system. The present invention relates to a descrambling method and apparatus for descrambling a John signal.

[Conventional technology]

In CATV, a viewing subscriber who has a contract for receiving a paid program pays a monthly fee for each program or channel. For this reason, a countermeasure must be taken such that viewing is not possible for those who have not subscribed to the service or who intend to view the content in a stolen manner. Therefore, in the case of CATV, a television signal to be transmitted is processed by a method called scrambling that disturbs an image by compressing a synchronization signal in a television signal at a different compression ratio, for example, every 15 V (frame) period, and descrambling on a receiving side. Unless the processing is performed, normal video cannot be viewed to prevent eavesdropping.

FIG. 11 shows a conventional television signal scrambling method, in which a baseband television signal shown in FIG. 11A is converted into a television IF signal as shown in FIG. , (C), the horizontal synchronizing section including the horizontal blanking portion of the video signal and the vertical blanking interval (VBI) are compressed at the same compression ratio, and as shown in (d), the audio IF signal is compressed. Transmits a key signal including data relating to the compression ratio of the television signal in synchronization with the horizontal synchronization section of the video signal.

In a CATV terminal having a function of descrambling a television signal scrambled in this manner, a transmitted key signal is detected, compressed data is extracted and decoded, and an extension pulse having an amplitude based on the decoded data is extracted. Is generated at the timing of a key signal, and the synchronizing signal portion in the television signal compressed on the transmission side is expanded by using the expansion pulse so that a normal video can be viewed.

[Problems to be solved by the invention]

However, in the case of a television signal that has been scrambled by the above-described scramble method, it is possible to descramble to a certain extent even if the television signal is not a regular CATV terminal, and to steal and watch.

For example, the key signal is AM-modulated to the audio signal and is superimposed on each horizontal blanking (HBI) section, but is not superimposed on the VBI section. Therefore, the key signal is passed through an integration circuit after AM detection. Detect VBI section by method. By detecting a video signal obtained by extending the VBI section based on the detected section and performing synchronization decomposition, a synchronization signal in the VBI section is obtained, and thereafter, the self-running timing generator is operated in synchronization with the synchronization signal. The amplitude of the pulse generated by the self-running timing generator is adjusted based on the integration level of the synchronization signal in the VBI section to form an extension pulse of the horizontal synchronization section, so that descrambling is performed, so that eavesdropping can be easily performed. it can.

Accordingly, an object of the present invention is to provide a method of scrambling a television signal that cannot be easily stolen and viewed in view of the above-mentioned conventional problems.

Another object of the present invention is to provide a method and apparatus for descrambling a television signal scrambled by the above method.

[Means for solving the problem]

In order to solve the above-mentioned problems, a television signal scrambling method according to the present invention compresses a horizontal synchronization section and a vertical blanking section of a television signal and compresses the audio signal corresponding to the horizontal synchronization section into an audio signal. A method for scrambling a television signal, comprising superimposing a key signal including information on a key signal, wherein a pseudo key signal is superimposed on an audio signal corresponding to the vertical blanking section in synchronization with the horizontal synchronization section. It is characterized in that the signal includes information about the position of the vertical blanking interval, and information for decoding the information about the position is transmitted as out-band data.

In order to solve the above-mentioned problem, a descrambling method for a television signal according to the present invention includes a television signal in which a horizontal synchronization section and a vertical blanking section are compressed and scrambled, and the television signal is compressed in the vertical blanking section. The information related to the compression and the position of the vertical blanking section superimposed on the part corresponding to the horizontal synchronization part as in-band data on the audio signal in which the pseudo key signal is superimposed on the corresponding part in synchronization with the horizontal synchronization part. A descrambling method based on a key signal including information on the position of the vertical blanking section transmitted as out-band data, and information for decrypting information on the position of the vertical blanking interval, which is included in the key signal. Information about the position of the vertical blanking interval is transmitted as the out-band data. The vertical blanking interval is detected based on the decoded information, and information on the compression included in the key signal is extracted based on the detected vertical blanking interval, and the extracted compression is extracted. Generating a decompression signal for expanding the horizontal synchronizing unit and the vertical blanking interval based on the information regarding the horizontal synchronizing unit and the vertical blanking interval, and descrambling the television signal by expanding the horizontal synchronizing unit and the vertical blanking interval based on the expanded signal. And

Further, a descrambling device for a television signal according to the present invention for solving the above-mentioned problem is characterized in that a horizontal synchronizing unit and a vertical blanking interval are compressed and scrambled, and the television signal is transmitted to the vertical blanking interval. The information on the compression superimposed on the portion corresponding to the horizontal synchronization portion as the in-band data on the audio signal in which the pseudo key signal is superimposed in synchronization with the horizontal synchronization portion on the portion corresponding to An apparatus for descrambling based on a key signal including information on a position and information for decoding information on a position of the vertical blanking section transmitted as out-band data, the apparatus comprising: Information about the position of the vertical blanking interval is transmitted as the out-band data. Decoding means for decoding based on the information, a vertical blanking interval detecting means for detecting the vertical blanking interval based on the decoded information, and a vertical blanking interval detected by the vertical blanking interval detecting means. Information extracting means for extracting the information on the compression included in the key signal, and an expansion for generating an expansion signal for expanding the horizontal synchronization section and the vertical blanking section based on the information on the compression extracted by the information extracting means. A signal generating means, and a descrambling means for descrambling a television signal by expanding the horizontal synchronizing section and the vertical blanking section by an expansion signal generated by the expansion signal generating means.

[Action]

In the above configuration, since the pseudo key signal is superimposed on the portion corresponding to the vertical blanking interval of the audio signal in synchronization with the horizontal synchronizing unit, the presence of the pseudo key signal allows the audio signal to be detected even in the VBI interval. Cannot be detected separately from the horizontal synchronization unit. Therefore, there is no reference for generating a decompression signal for extending the VBI section, and the VBI section cannot be decompressed and the synchronization signal cannot be obtained. Cannot operate the self-running timing generator that generates That is, it is not possible to form a decompression signal for decompressing the horizontal synchronizing unit and the VBI section compressed by scrambling, which makes it difficult to eavesdrop.

In addition, since the key signal includes information on the position of the VBI section and information for decoding the information on the position is transmitted as out-band data, the VBI section cannot be detected without both information. , Making stealing more difficult.

Further, in the descrambling method and device of the present invention, the pseudo key signal is superimposed on a portion corresponding to the VBI section of the audio signal transmitted together with the television signal scrambled from the center, but is included in the key signal. VB
VB using information decoded based on information transmitted as out-band data
Detecting the I section, extracting the compression-related information included in the key signal based on the detected VBI section, and extracting the expanded signal for expanding the horizontal synchronization section and the VBI section based on the extracted compression-related information. The expanded signal causes the horizontal synchronizing section and the VBI section to be expanded so that the television signal can be descrambled.

〔Example〕

 Hereinafter, embodiments of the present invention will be described with reference to the drawings.

1 (a) to 1 (f) and 2 (a) to 2 (f)
FIG. 3 is a timing chart showing video signals at the beginning of field 1 and field 2 and the trailing end of the previous field, and a key signal, a compressed signal, and an expanded signal corresponding to the video signal, respectively. The television signal scrambling method and descrambling method according to the present invention will be described with reference to FIG.

In the method of scrambling a television signal according to the present invention, a horizontal synchronizing signal and a VBI section are compressed by a compressed signal as shown in FIG. 1C and FIG. 2C, and FIG. 1A and FIG. And (b) as shown in FIG.
A pseudo key signal is inserted into the section of the audio signal corresponding to the I section at the same cycle as the key signal of the other section, and the position data of the VBI section is added to the key signal as in-band data by encrypting, and Decryption data for decrypting the encrypted position data is transmitted as out-band data. The key signal and the pseudo key signal are superimposed on the audio signal by AM modulation in synchronization with the horizontal synchronizing signal, similarly to the conventional key signal.

The correspondence between the in-band data and the video sync is shown in FIG. 3. For convenience of explanation, the video sync of the video signal is numbered from 1 to 525 in order from the VBI section of the previous fret. The band data are numbered D0 to D260 corresponding to video sync Nos. 23 to 283, and D'0 to D'262 corresponding to video syncs No. 284 to No. 22, respectively.

Then, the in-band data D152 to D167 and D'153
The start frame indicating the head of the data insertion position by D ′ to D′ 169 is D168 to D175, D′ 170 and D′ 177.
The encrypted VBI start data indicating the position of the VBI is represented by DBI to D183 and D′ 178 to D′ 185. , D184
To D191 and D'186 to D'193, the compressed data is superimposed on the audio signal and transmitted.

In addition to the above data, timing mode data (representing the time from the key timing of the key signal to the horizontal synchronizing signal, for example, 0, 4, 8, 12 or
16 μsec, which is the data for notifying the terminal of which time was set), multi-mode data (representing the mode of the compression level), tag data,
In-band data such as IPPV (impulse pay-per-view) event data is also superimposed on the audio signal and transmitted.

The encrypted VBI start data is switched for each program, and information for decrypting the encrypted VBI start data is transmitted as out-band data at the beginning of each program.

The video signal compressed and scrambled by the above-described compressed signal shown in FIG. 1 (c) and FIG. 2 (c) is received by the terminal and decoded by the decoding information previously received as out-band data. In in-band data
Based on the VBI start data and the compressed data, a decompression signal as shown in (d) to (f) of FIG. 1 and FIG. 2 is generated to perform descrambling.

In the start frame in the in-band data, at least 16 consecutive "1s" are detected, and then a point in time when "0" is detected is defined as a start frame. The VBI start data is composed of 8 bits including the first "0", and its value is temporarily set to L. The VBI reflection field data is information indicating how many fields later the arithmetic processing for detecting the VBI position is to be performed using the VBI start data. The compressed data is data indicating the compression level of the horizontal synchronization section and the VBI section.

The out-band data is an operation code value sent out-of-band, and this is assumed to be M.

Then, the terminal receiving these data sets the start of the VBI interval to 8H (H is the horizontal sync time) × L + M × H
8H × L + M after start frame detection
× H hours later. Also, VB
Using the I reflection frame data N, ｛(8H × L + M ×
H) + N fields｝ time later. Since this operation is performed for each field, VBI
The position of the section will acquire a strong confidential ability.

As described above, the start position of the VBI section is obtained, and an extension signal is generated which lasts for 22 hours in field 1 and 21 hours in field 2. The level of the decompressed signal is set to 0 dB, 6 dB, or 10 dB according to the compressed data, so that the television signal received by the decompressed signal is decompressed and the television signal is descrambled.

FIGS. 4 to 8 show examples of the configuration of a center-side device for performing the above-described television signal scrambling method according to the present invention and a terminal for performing the descrambled television signal descrambling method by the above-described scrambling method. It will be described with reference to FIG.

4 to 6 show an example of the configuration of a CATV center-side device (head end). In FIG. 4, an existing broadcasting station receives radio waves from an existing broadcasting station using a VHF antenna, a UHF antenna, and a BS antenna. Is input to a channel processor 12 of the head end 1, where it is processed and converted into a predetermined RF frequency, and then mixed in a mixer 13 via a transmission line 14 for a number of subscribers (not shown). CA
Sent to TV terminal.

The head end 1 has a video camera, a video tape recorder (VTR), and the like as video source sources for broadcasting an independent broadcast program.
One is selected under the control of the headend processor 15,
A video signal from the selected video source is sent to modulator 16 and encoder 17. The modulator 16 converts the video signal from the video source into a frequency of a specific channel, and the frequency-converted signal is input to the mixer 13 after the frequency is further increased by the up-converter 18.

The head-end processor 15 automatically switches broadcast programs by, for example, selecting a video source according to the broadcast schedule of the program, controls the encoding method by the encoder 17, and controls the encoding of the pay program. The FSK transmitter 19 sends out the viewing permission / non-permission data and the decryption data related to the scramble, etc., and uses this as out-band data from the mixer 13 via the transmission path 14 through the CA.
Controls transmission to the TV terminal.

5 and 6 show examples of the configuration of the modulator 16 and the encoder 17. In FIG. 5, the modulator 16 receives an audio signal from a video source source such as a video tape recorder or a video disk player. The video signal is input to the video input IN of the encoder 17 that performs scrambling,
Part of it goes through encoder 17 and its video output OU
From T is input to the video input IN of the modulator 16. Modulator 16
Converts the video signal input to the video input IN and the audio signal input to the audio input IN into IF signals.

The television IF signal Fv and the audio IF signal Fa converted by the modulator 17 are returned to the encoder 17, where the television IF signal Fv is compressed by a compressed signal as shown in FIG. 1 and FIG. Horizontal sync and vertical blanking (VBI)
1 and 2 are compressed at a predetermined compression rate, and the audio IF signal Fa includes a video signal portion and a VBI interval as shown in FIG. 1 and FIG. 2 (b). The key signal and the pseudo key signal are respectively superimposed in synchronization with the video sync of the signal.

The television IF signal Fv in which the horizontal synchronizing unit and the VBI section are compressed as described above, and the audio IF signal Fa in which the key signal and the pseudo key signal are superimposed, are transmitted from the encoder 17 to the modulator 16.
Where the television IF signal Fv and the audio IF signal
Fa is output after being mixed.

As the encoder 17, for example, one having a configuration shown in FIG. 6 is used. In FIG. 6, a video signal from a video source input to a video input IN is a sync separation circuit.
The horizontal synchronization signal H and the vertical synchronization signal V are separated and extracted from the television signal in the video signal. The television IF signal Fv input from the modulator 16 is
Audio returned to the modulator 16 via the 10 dB RF switch 17b, the amplifier 17c and the 6dB RF switch 17d, and input from the modulator 16
IF signal Fa is returned to modulator 16 via 5.5 dB RF switch 17e.

The 10 dB RF switch 17 b and the 6 dB RF switch 17 d are
Generates Fv pulse generator 17g operating under control of 17f
It is turned on / off by Fv pulse, and the horizontal sync part and VBI section of the television IF signal Fv are turned on by 10 dB and 6 dB.
Compress each. On the other hand, the 5.5 dB RF switch 17e is
F generated by the Fa pulse generator 17h operating under the control of 7f
It is turned on / off by a pulse, and the audio IF
5.5dB insertion period of key signal and pseudo key signal of signal Fa
Compress.

The CPU 17f operates according to a predetermined program, outputs in-band data having the above-described predetermined arrangement shown in FIG. 3 according to the vertical synchronization signal V input from the synchronization separation circuit 17a, and outputs the in-band data to the Fa pulse generator 17h. To supply. The Fa pulse generator 17h to which the in-band data has been supplied receives a third signal between the key signal synchronized with the horizontal synchronization signal H and the video sync based on the vertical synchronization signal V and the horizontal synchronization signal H from the synchronization separation circuit 17a. A Fa pulse corresponding to the in-band data is generated so that the relationship shown in the figure is established, and this is generated.
Input to 5.5dB RF switch 17e to turn on / off. This allows the audio to pass through the 5.5dB RF switch 17e
A key signal including in-band data and a pseudo key signal are superimposed on the IF signal Fa by AM modulation.

Also, the CPU 17f counts the vertical synchronization signal V input from the synchronization separation circuit 17a, and sets the compression ratio of the horizontal synchronization section and the VBI section to 10 dB, 6 dB, or 0 dB according to the input of the predetermined number of vertical synchronization signals V. Then, the data relating to the set compression ratio is used when generating the in-band data, and is supplied to the Fv pulse generator 17g.

The Fv pulse generator 17g receives the horizontal synchronizing signal H and the vertical synchronizing signal V from the sync separation circuit 17a,
An Fv pulse for turning on the 10 dB RF switch 17 b or the 6 dB RF switch 17 d in the horizontal synchronizing section of the television IF signal Fv and the VBI period is generated based on the data on the compression ratio from U17f. This allows the 10dB RF switch 17b and 6dB RF
The horizontal synchronization section and the VBI section of the television IF signal Fv passing through the switch 17d are compressed at a predetermined compression rate.

Next, the configuration of a CATV terminal that receives a signal scrambled on the CATV center side described above with reference to FIGS. 4 to 6 and that is transmitted through the transmission line 14 and descrambles the signal will be described with reference to FIG. This will be described below.

In FIG. 7, a signal transmitted through a transmission line is input to a converter 21 through an input terminal IN, and is split at an entrance portion by a splitter 21a, a part of which is an FSK for extracting out-band data. Input to the receiver 22. The converter 21 selects a specific channel, converts the frequency of the signal of the selected channel, and outputs an IF signal to its output. The IF signal obtained at the output of converter 21 is HPF and LPF
And is separated into a high-frequency television IF signal Fv and a reduced audio IF signal Fa. Prior to the switching of the broadcast program, the FSK receiver 22 transmits the decryption data relating to the scramble transmitted from the FSK transmitter 19 of the head end 1 together with the viewing permission / non-permission data related to both of the pay programs. And the like, and input this to the CPU.

The television IF separated by the filter circuit 23
The signal Fv is input to the expansion circuit 24, where it is descrambled. On the other hand, the audio IF signal is demultiplexed by the demultiplexer 25, a part of which is input to the key signal detector 26, and the key signal superimposed on the audio IF signal is extracted by the envelope detection means or the like. The key signal extracted by the key signal detector 26 is input to the in-band data detection circuit 27, where the in-band data included in the key signal is detected. Some of the detected in-band data is used to generate 6 dB and 10 dB elongation pulses, while another is input to CPU 28, which operates according to a predetermined program, where the out-of-band signal from FSK receiver 22 is sent. Processed with data. CPU2 that input in-band data and out-band data
Numeral 8 inputs the decoded data of the data input as out-band data from the FSK receiver 22 to the in-band data detection circuit 27 as control data, and also generates various control signals.

The in-band data detection circuit 27 which receives the key signal from the key signal detector 26 uses the control data from the CPU 28 to generate 6 dB at the timing synchronized with the horizontal synchronization section and the VBI section.
Alternatively, a 10 dB extension pulse is generated, and these signals are input to the extension circuit 24. The expansion circuit 24 expands and descrambles the compressed horizontal synchronizing section and vertical blanking section of the television IF signal by using an expansion pulse having an amplitude corresponding to the expansion rate, and returns to the television IF signal before scrambling. .

Descrambled television IF signal and duplexer 25
The signal is mixed with the audio IF signal that has passed through the mixer 29 and output from the output terminal OUT.

FIG. 8 shows a specific circuit example of the in-band data detection circuit 27. In FIG. 8, reference numeral 27a denotes a clock generator 27b.
And an in-band data edge detection circuit that operates on the basis of a clock signal from the key signal detector 26. The circuit detects a rising edge of a key signal composed of a key and data input from the key signal detector 26 via an AND gate 27c. The function of this circuit is stopped during that time by the VBI mask signal which is inverted and input to one input of the AND gate 27c.

Reference numeral 27d denotes a VBI mask end edge detection circuit for detecting the end of the VBI mask period. The circuit includes an in-band data edge detected by the in-band data edge detection circuit 27a and a VBI mask end detected by the circuit 27d. The edge generates a reset signal for resetting a timing signal generator 27e described later.

27e operates on the basis of the clock for timing generation from the clock generator 27b, and includes an OR gate 27f and an AND gate.
A timing signal generator which is reset and initially started by a reset signal generated by the VBI mask end edge detection circuit 27d inputted through 27g,
The circuit includes a data edge mask signal for preventing edge reset due to data, a data latch clock, a data window signal and a data clock for capturing data, a clock for generating an extended pulse, and the like in each part in the in-band data detection circuit 27. Generate

27h is a key / data discriminator for discriminating between the key and the data constituting the key signal. In this discriminator, attention is paid to the fact that the transmission time between the key and the data is, for example, 19 μsec apart. Is 63.5 μsec, (6
3.5-19)> 63.5 / 2 ≒ 32 μsec, so 32 μsec after the reset of the timing signal generator 27e due to the in-band data edge, it recognizes that the next is a key signal and generates a discrimination signal. Controls the AND gate 27i. The discrimination in the discriminator 27h is performed once at the start of data acquisition in each field.

27j is a data fetch circuit that operates based on a data fetch clock from the clock generator 27b, and is opened by a data window signal generated by the timing signal generator 27e according to a discrimination signal from the key / data discriminator 27h. The data is taken in 1H units through the AND gate 27k.

27l is a data shift register that operates based on the data clock from the timing signal generator 27e, and this shift register is 1H by the data fetch circuit 27j.
Data fetched in units is shifted, and is accessible in 8-bit units.

27m is a VBI start frame detection circuit that monitors data from the data shift register 27l, and detects when at least 16 pieces of data are continuously “1” and the next data becomes “0” as a start frame. The start frame detection signal output from the circuit is latched for a period of about 1 V until reset by a 1 V signal generated by a 1 V timer 27p described later.

Reference numeral 27n denotes a VBI start position detection circuit that operates based on the data clock from the timing signal generator 27e, and this circuit shifts the data in accordance with the input of the start frame detection signal from the VBI start frame detection circuit 27m. VBI start data, which is in-band data, and subsequent VBI reflection field data are fetched and latched from the register 27l based on the data clock. The VBI start position detection circuit calculates the VBI start position according to these data and the decoded data as the control data from the CPU 28, and calculates the VBI mask based on the data clock at the VBI start position obtained by the calculation. A start signal is generated and input to a VBI mask signal generator 27o described later.

27o is a VBI mask signal generator that operates based on the VBI mask generation clock from the clock generator 27b,
The circuit generates a VBI mask signal having a predetermined time length in response to the input of the VBI mask start signal from the VBI start position detection circuit 27n.

27p is a 1V timer that operates based on the VBI mask generation clock from the clock generator 27b, and starts operating in response to the input of the start frame detection signal from the VBI start frame detection circuit 27m. In addition,
The timer length is set to, for example, a 196H period shorter than the data “1” for the next start frame is sent.

27q is a data decoder for timing mode, and 27r is a data decoder for decompression level, which are stored in the data shift register 27l based on the decompression mode latch clock and the timing mode latch clock from the timing signal generator 27e. The data for the timing mode and the data for the expansion level are respectively extracted from the corresponding part of the band data, and the extracted data is input to the expansion pulse generator 27s described later.

Reference numeral 27s denotes an extension pulse generator. The circuit includes an extension pulse generation clock and a VBI start signal from the timing signal generator 27e, a timing mode signal from the timing mode data decoder 27q, and the extension level data. Based on the extension level signal from the decoder 27r, 6 dB and 10 dB extension pulses are generated at predetermined timing.

The operation of the in-band data detection circuit 27 having the above configuration will be described below with reference to the timing chart of FIG.

The timing signal generator 27e, the data shift register 27l, the key / data discriminator 27h, and the VBI start frame detection circuit 27m are reset in an initial state. In such a state, the absence of the VBI mask signal
The gate 27c is open, and in-band data (signals shown in FIGS. 1 and 2 (b)) as shown in FIG. 9 (a) is passed through the AND gate 27c. , Where the rising edge of the key or data of the key signal is detected. The in-band data edge detection circuit 27a outputs an edge signal as shown in FIG. 9 (b) at its output in response to the edge detection. In the example of FIG. 9, the edge signal input first is due to the key of the key signal, and this is input to the AND gate via the OR gate 27f.
Entered in 27g. Since the key / data discriminator 27h is reset and there is no discrimination signal, the output of the AND gate 27i is at the L level and is in an open state. The signal is input to the timing signal generator 27e via the input terminal.

The edge signal input to the timing signal generator 27e resets the timing signal generator 27e and is counted therein. Based on the count result, the timing mode latch clock, the expansion mode latch clock, the VBI expansion start signal, etc. Used to generate

Due to the reset, the timing signal generator 27e outputs a data edge mask signal as shown in FIG. 9C after a predetermined time (for example, 16 μsec). At this time, the key /
Since the discrimination signal from the data discriminator 27h is at the L level as shown in FIG. 9 (d) and the AND gate 27g is in the open state, the edge signal based on the next data is also output from the AND gate 27g.
To the timing signal generator 27e. However, the timing signal generator 27e outputs a 32 μsec elapsed signal 32 μsec after the input of the first edge signal, and in response thereto, the key / data discriminator 27h generates a discrimination signal as shown in FIG. 9 (d). Therefore, thereafter, each time a data edge mask signal is generated, the AND gate 27g is closed, and no edge signal due to data is input to the timing signal generator 27e. Note that the above-mentioned discrimination signal is a VBI mask signal generator 27o.
Key / data discriminator 27h by VBI mask signal generated
Hold H level until is reset.

As described above, the timing signal generator 27e to which the edge signals corresponding to the keys are sequentially input outputs a data window signal and a data clock at a predetermined timing for each input. The data window signal is input to the AND gate 27k as an open signal, and the data clock is input to the data shift register 27l and the VBI start position detection circuit 27n. When the AND gate 27h is opened by the data window signal, the data following the key is
The data passes through the D gate 27h and is captured by the data capturing circuit 27j. The data fetched by the data fetch circuit 27j is immediately output and input to the data shift register 27l. The data shift register 27l inputs the data supplied to the input based on the input of the data clock and shifts sequentially.

As described above, the data shift register 27l holds the latest data of at least 8 bits, and discards the oldest one sequentially. However, the held data is stored in the VBI start frame detection circuit 27m and the VBI start position detection circuit 27n. ,
It is constantly output to the timing mode data decoder 27q and the expansion level data decoder 27r.

The VBI start frame detection circuit 27m constantly monitors data input from the data shift register 27l,
A VBI start frame is detected by detecting that the bit has become “0” after “1” continuously for a bit, and a start frame detection signal is output in response to the detection. This start frame detection signal resets the VBI start position detection circuit 27n and the 1V timer 27p.

The reset VBI start position detection circuit 27n
The VBI start data and VBI reflection field data following the start frame are sequentially fetched from the data shift register 27l by the data clock, and the fetched VBI start data "L" and VBI reflection field data "N"
And the decryption data “M” input as control data from the CPU 28, and calculates ｛(8H × L + M ×
H) A VBI mask start signal is output after + N fields {time}. The VBI mask start signal is input to a VBI mask signal generator 27o, and the corresponding VBI mask signal generator 27o outputs a VBI mask signal.

The VBI reflection field data "N" is "0"
Then, the VBI mask signal may be generated 8H × L + M × H time after the detection of the start frame.

The VBI mask signal is input to the AND gate 27c to mask the pseudo key signal inserted in the VBI section and closes it, and is input to the key / data discriminator 27h to reset it, and The falling edge is input to the VBI mask end edge detection circuit 27d and detected. Due to the closing of the AND gate 27c, the in-band data is supplied to the in-band data edge detection circuit during a certain period of the VBI mask signal.
No input is made to 27a and the AND gate 27k. At this time, since the period edge signal of the VBI mask signal is not input to the timing signal generator 27e, the timing signal generator 27e
27e can know that the period is the VBI mask period.

Then, after a lapse of time, when the VBI mask signal falls,
In response to this, the VBI mask end detection circuit 27d detects the end of the VBI mask and generates an edge signal. This edge signal is input to the AND gate 27g via the OR gate 27f. At this time, since the key / data discriminator 27h is reset and the discrimination signal is not output, the AND gate 27g is in the open state, so that the VBI mask end detection circuit 27d outputs the output edge signal to the timing signal generator 27e. This resets the timing signal generator 27e.

The operation after reset of the timing signal generator 27e is performed in the same manner as the operation described with reference to the timing chart of FIG. However, subsequent operations are
As shown in FIG. 10, since the timing is performed based on the end of the VBI mask signal, the timing signal generator 27e generates a decompression pulse generation clock, a VBI decompression start signal, a decompression mode latch clock, and a timing generated at a predetermined timing. The mode latch clock is generated at a normal position, and a predetermined data latch operation and a predetermined extension pulse generation operation are performed.

As described above, the use of the in-band data detection circuit 27 shown in FIG. 8 makes it possible to descramble the television signal scrambled on the center side even if the pseudo key signal is inserted in the VBI section.

〔effect〕

As described above, in the scramble method of the present invention,
Since the pseudo key signal is superimposed on the portion corresponding to the vertical blanking interval of the audio signal in synchronization with the horizontal synchronizing section, the presence of this pseudo key signal causes the VB signal to be detected even if the audio signal is detected.
Since the I section cannot be detected separately from the horizontal synchronizing section, an expanded signal for expanding the horizontal synchronizing section and the vertical blanking section compressed by scrambling cannot be formed at a regular position, and the content is stolen. In addition to this, information on the position of the VBI section is included in the key signal, and information for decoding the information on the position is transmitted as out-band data. Can make it more difficult to steal.

In the descrambling method and apparatus according to the present invention, the vertical blanking interval is detected based on the information on the position of the vertical blanking interval included in the key signal and the decoding information of the position information transmitted as out-band data. Extracting the information related to the compression included in the key signal based on the detected vertical blanking interval, and generating an expanded signal for expanding the horizontal synchronization unit and the vertical blanking interval based on the extracted information related to the compression. Then, the horizontal synchronizing section and the vertical blanking section are expanded by the expansion signal so that the television signal can be descrambled.

In this example, the start frame data is fixed. However, it is also possible to notify the start frame pattern out-of-band and execute the same.

[Brief description of the drawings]

1 and 2 are explanatory diagrams for explaining a method of scrambling and descrambling a television signal according to the present invention, FIG. 3 is a diagram showing a relationship between a video sync and in-band data, and FIGS. Is a block diagram showing the configuration of a CATV center that performs scrambling using the method of the present invention; FIG. 7 is a block diagram showing the configuration of a CATV terminal that descrambles a signal scrambled by the method of the present invention; 9 is a block diagram showing a specific configuration of a part of the circuit in FIG. 7, FIGS. 9 and 10 are timing charts used to explain the operation of the circuit in FIG. 8, and FIG. FIG. 11 is an explanatory diagram for describing a conventional scrambling method. Fv: TV IF signal, Fa: Audio IF signal, 2 ...
Encoder, 2b ... 10dB RF switch, 2d ... 6dB RF switch, 2e ... 5.5dB RF switch, 2g ... Fv pulse generator, 2h ... Fa pulse generator, 17 ... In-band data detection circuit, 17e ... Timing Signal generator, 17m VBI start frame detection circuit, 17n VBI start position detection circuit, 17o VBI mask signal generator (vertical blanking interval detection means), 17r Data decoder for expansion level (information extraction Means), 17s ... Expansion pulse generator (expansion signal generation means), 14 ... Expansion circuit (descrambling means).

Claims (3)

(57) [Claims] 1. A television signal in which a horizontal synchronizing part and a vertical blanking interval of a television signal are compressed and a key signal including information on the compression is superimposed on an audio signal corresponding to the horizontal synchronizing part. In the scrambling method, a pseudo key signal is superimposed on an audio signal corresponding to the vertical blanking section in synchronization with the horizontal synchronizing section, information on a position of the vertical blanking section is included in the key signal, and A method for scrambling a television signal, comprising: transmitting information for decoding information regarding the information as out-band data. 2. A pseudo key signal is superimposed on a portion of a television signal which has been compressed and scrambled by compressing a horizontal synchronizing portion and a vertical blanking interval in synchronization with the horizontal synchronizing portion at a portion corresponding to the vertical blanking interval. The key signal including the information on the compression and the information on the position of the vertical blanking section superimposed on the portion corresponding to the horizontal synchronizing unit as in-band data in the audio signal, and transmitted as out-band data. In a method for descrambling based on information for decoding information on the position of a vertical blanking interval, information on the position of the vertical blanking interval included in the key signal is added to information transmitted as the out-band data. And detects the vertical blanking interval based on the decoded information. Extracting information on the compression included in the key signal based on the detected vertical blanking interval, and generating an expansion signal for expanding the horizontal synchronization section and the vertical blanking interval based on the extracted information on compression. And descrambling the television signal by extending the horizontal synchronizing section and the vertical blanking section with the decompression signal. 3. A television signal in which a horizontal synchronization section and a vertical blanking section are compressed and scrambled, and a pseudo key signal is superimposed on a portion corresponding to the vertical blanking section in synchronization with the horizontal synchronization section. The key signal including the information on the compression and the information on the position of the vertical blanking section superimposed on the portion corresponding to the horizontal synchronizing unit as in-band data in the audio signal, and transmitted as out-band data. In a method for descrambling based on information for decoding information on the position of a vertical blanking interval, information on the position of the vertical blanking interval included in the key signal is added to information transmitted as the out-band data. Decoding means for decoding based on the decoded information, and the vertical blankin based on the decoded information. Vertical blanking interval detecting means for detecting an interval; information extracting means for extracting information related to the compression included in the key signal based on the vertical blanking interval detected by the vertical blanking interval detecting means; Expansion signal generation means for generating an expansion signal for expanding the horizontal synchronization section and the vertical blanking section based on the information on the compression extracted by the extraction means; and the horizontal synchronization section based on the expansion signal generated by the expansion signal generation means. A descrambling device for descrambling a television signal by extending a vertical blanking interval, comprising: a descrambling device for a television signal.