CA1213972A - Apparatus for scrambling a television signal - Google Patents
Apparatus for scrambling a television signalInfo
- Publication number
- CA1213972A CA1213972A CA000432292A CA432292A CA1213972A CA 1213972 A CA1213972 A CA 1213972A CA 000432292 A CA000432292 A CA 000432292A CA 432292 A CA432292 A CA 432292A CA 1213972 A CA1213972 A CA 1213972A
- Authority
- CA
- Canada
- Prior art keywords
- signal
- key code
- code
- scene change
- program
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
Links
Classifications
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N7/00—Television systems
- H04N7/16—Analogue secrecy systems; Analogue subscription systems
- H04N7/167—Systems rendering the television signal unintelligible and subsequently intelligible
- H04N7/171—Systems operating in the amplitude domain of the television signal
- H04N7/1716—Systems operating in the amplitude domain of the television signal by inverting the polarity of active picture signal portions
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- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
- H04N19/10—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
- H04N19/134—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the element, parameter or criterion affecting or controlling the adaptive coding
- H04N19/142—Detection of scene cut or scene change
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
- H04N19/10—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding
- H04N19/169—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding
- H04N19/179—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using adaptive coding characterised by the coding unit, i.e. the structural portion or semantic portion of the video signal being the object or the subject of the adaptive coding the unit being a scene or a shot
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N19/00—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals
- H04N19/85—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using pre-processing or post-processing specially adapted for video compression
- H04N19/87—Methods or arrangements for coding, decoding, compressing or decompressing digital video signals using pre-processing or post-processing specially adapted for video compression involving scene cut or scene change detection in combination with video compression
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N5/00—Details of television systems
- H04N5/14—Picture signal circuitry for video frequency region
- H04N5/147—Scene change detection
-
- H—ELECTRICITY
- H04—ELECTRIC COMMUNICATION TECHNIQUE
- H04N—PICTORIAL COMMUNICATION, e.g. TELEVISION
- H04N7/00—Television systems
- H04N7/16—Analogue secrecy systems; Analogue subscription systems
- H04N7/167—Systems rendering the television signal unintelligible and subsequently intelligible
- H04N7/1675—Providing digital key or authorisation information for generation or regeneration of the scrambling sequence
Abstract
ABSTRACT OF THE DISCLOSURE
An apparatus for scrambling or encoding a television signal by inverting the latter signal in accordance with a control signal having a predetermined code pattern comprises a detector circuit for detecting a change in a picture scene of the television signal and generating an identification signal in response to detection of the scene change and code generator for generating a key code signal of specific pattern which indicates a particular program of the television signal. According to this invention, the control signal is formed in response to both the identification signal and the key code signal.
An apparatus for scrambling or encoding a television signal by inverting the latter signal in accordance with a control signal having a predetermined code pattern comprises a detector circuit for detecting a change in a picture scene of the television signal and generating an identification signal in response to detection of the scene change and code generator for generating a key code signal of specific pattern which indicates a particular program of the television signal. According to this invention, the control signal is formed in response to both the identification signal and the key code signal.
Description
~39~7;2 B.~CKGROUND OF THE INVENTION
Field of the Invention:
This invention reiates to appara-tus for scrambling information signal, such as television signal, and more particularly, to apparatus for scrambling the television signal in accordance with specified code signal and changes in the scene of the picture of the television signal.
Description of the Prior Art:
A scrambling broadcasting system is conventionally known in which a television signal of a specific program is scrarnbled and transmitted from a broadcasting station and a subscriber who contracts with the broadcasting station and has a decoder can V e~.~J the specific program. In such a system, a broadcasting station transmits a scrambled information signal and a key signal for decoding it. A scrarnbled i.nformation signal is obtained bv inverting a polarity of a television signal or reversing the signal order at a predetermineG period. r non-subscriber is not therefore able to view a correc. image or hear sound even if he can receive the scrambled information signal. ~ccordingly, only subscribers who have contracts with the broadcasting station can unscramble the scrambled information signal in accordance with the key signa] and can view and hear the correc-t image and sound.
In a conventional scramblirlg broadcast,ng system as described above, when a scrambled in_ormation signal is received by a non-subscriber, the received . .
picture mus. be non-sensible. For this purpose, various scrambling methods have been proposed.
~ ne scrambling method is known in which a television signal is inverted at a predetermined field period. According to this method, when a scrambled signal is subject to distortion influence by a transmission system, unscrambling at a receivin~ side may not result in reproduction of an original waveform.
For example, when a polarity-inverted signal is reinverted by a decoder, a level difference may be generated or the waveform may be distorted. When an unscrambled sianal is supplied to a TV receiver, flicker occurs at the polarity-inverted portion of the picture. Such flicker is yarticularly noticeable in the case of a still image. r,7hen a scrambled ~royr m broadcast from a station is recorded bv a VTR, fiicker tends to be caused more rrequently since a VTR is nonlinear in a DC manner as well as in an AC manner.
In order to overcome the aboove-described disacJant_ge, USP 43-0906 discioses improved scrambling system, in which the polarity of the television signal is inverted or reversed when the scene change of the picture in the television signal. According to the system, the flic.~ers in the picture will not be noticeable to the viewers. However, the system has a defect that a scrambling code is easily unscrambled even by viewers who do not contract with the broadcasting station, because the scramDle code is determined only bv the content of the picture in the television signal.
z SU~ARY OF THE INVENTION
_ _ lt is one object of this invention to provide an improved scrambling apparatus which overcomes the above defect.
It is another object of this invention to provide new scrambliny apparatus in which the polarity of the television signal is in~erted or revers2d.
In accordance with an aspect of this invention, the television signal is scrambled b~
invertin~ the television signal in accordance with control signal. The control signal is ~ormed on basis of an identification signal which is generated when a change in the picture scene of the television signaL
and a ~ey code signal which is generated in accordance __ with specific program of the television signal.
BRIEF 3ESCRIPTIO~ OF THE DP~W NGS
Figs. 1A and 1B are timing charts showing an embodlment which performs a scrambling by inverting a polarity of a television signal at a scene change of a picture;
Fig. 2 is a bloc~ diagram of a cLrcuit for practicing the method of Figs. 1A and lB;
Figs. 3A to 3E are timing charts showing an embodiment of the present invention;
Fig. a shows a format of a television signal for a scrambling broadcast;
Flg. 5 shows an arrangement of various codes inserced in the television signal;
Fig. 6 s~ows a format of a program code;
Fig. 7 is a figure for explaining a content '2 of the program code;
~ ig. 8 shows a ~ormat of an address code and the proyram code;
Fig. 9 shows a format of a .~ey code;
Fig~ 10 shows formats of other codes;
Fig. 11 is a block diagram showing an embodi-ment of an apparatus for performing scramblingi Fig. 12 is a block diagram showing an embodi-ment of an apparatus for performing unscrambling;
Fig. 13 is a figure for e~plaining a mode of operation of a memory of the apparatus for performing unscrambling in recording mode for an unscrambled broad-cast hy a VTR; and Fig. 14 is a figure for explaining a mode of operation of the memory in reproduction mode bY the VTR.
DETAILED 3ESCRIPTION OF T~E PREFERRED E~BODIME~TS
Fig. l sho~-s an embodiment wherein the polarity or a television signal is inverted at a scene change of a picture. A scene change identification slgnal SC as shown in Fig. lA is prepared upon ~letection of a scene change portion in a television signal of a given program. In accordance with the scene change identification signal SC thus obtained, a scrambling pattern Pl' for instructing polarity inversion as shown in Fig. lB is generated.
When the pattern Pl' is at high level, for example, polarity inversion of the television signal is performed. In practice, the video signal period of the television signal alone is polarity~inverted, and the blan~ing period is not inverted. When polarity inversion is performed at a scene change, flicker attrlbutable to a level difference or the like as described above occurs simultaneously with a scene change, so that it may be neglected.
Fig. 2 shows an example of a block diagram of a circuit for practicing the method as descrioed above.
A television signal Sv received at an input terminal 101 is supplied to a scrambler 102 as well as to a scene change detector 103 which detects a scene change. Detection of a scene change is performed by differentiating a waveform obtained by integration of the signal Sv. In accordance with a detection output from the detector 103, an IDl generator 104 supplies a scene change identification signal SC to the scrambler 102 Upon reception of each signal SC the scrambler 102 inverts the polarity or the input television signal Sv, e~cep-t for a blanking period, in accordance with the scra~bling pattern Pl' as shown in Fig. lB. The scrambled signal from the scrambler 102 is supplied to an adder 105, and the signal SC is inserted therein. A
scran~bled signal Svs from the adder 105 appears at an output terminal 106. Note that the adder 105 inserts the scene change identification signal SC in a vertical blanking period BL~ or the scrambled signal. At the receiving side, the inserted signal is extrac-ted ~y a decoder and is used for unscrambling. In order to identify the polarity of the signal during unscrambling, the signal SC may include polarity information ~y means of a level di_ference, a pulse width difference or the like.
According to the embodiment as described above, since poLarit-~ inversion of the television signal is performed only upon detection of a scene change, unscrambling by a non-subscriber is too easy and only a less efLective secret transmission system can be provided.
Tne present invention has been provided to solve the above problems with the scrambling method using pola~ity inversion. The present invention will now be described with reference to the accompanying drawings.
Referring to Fig. 3A, a predetermined period T (e.g., 60 seconds) of a television signal of a specific program to be scrambled is preset by an inde~
signal ID. A scene change of such a program is detected so as to obtain a scene change identification signal SC. Then, a key signa~ paltern Pl which concludes within the predetermined period T as shown in Fig. 3B
is prepared. The leading and trailing edges of the pattern Pl coincide with the field ?er~od. In accordance with the signals ID and SC and the pattern Pl as described above, one of scrambling patterns P2, P3 and P4 (Figs. 3C, 3D and 3E) is generated which determines the timing of the polarity inversion.
Scrambling is performed by inverting the polarity of a video signal period of a television signal of a specific program in accordance with the pattern P2, P3 or P4. The key signal pattern Pl lS repeated at period T.
7~
The pattern P2 is obtained by A~Ding the signals ID and SC and the pat-tern Pl and inverting the polarity of the AND product. The pattern P3 rises with the signals ID and SC and falls at the trailing edge of the pattern P1. The pattern P4 rises wlth the ~\~D
product of the signals ID and SC and the pattern Pl and falls at the signal SC.
Various other scrambling patterns for determining the timing of the polarity inversion may also be formed in accordance with the signals ID and SC
and the pattern P1, in addition to those described above.
According to this embodiment, since polarity inversion is always performed at the time of a scene shange, flicker may be neglected. Furthermore, since polarity inversion is performed by comhining a scene change and a key signal pat-tern Pl, high scrambling effects may be obtained. The present invention also makes unscrambling difficult, and is therefore secure.
The signals ID and SC and the pattern P1 are coded to have a predetermined number of bits and are inserted at predetermined positions of the television signal for broadcasting, as will be described later.
At this time, note that the pattern Pl is inserted as a key code signal. The decoder at the receiving side detects the signals ID and SC and the pattern Pl and decodes the scrambling pa-ttern. The decoder unscrambles the signal; it restores the polarity of the 97~, polarity-inverted signal in accordance with the scrambling pattern.
Various signals to be transmitted from a broadcasting station together ~ith the scrambled specific program and a method for transmitting such signals will now be described.
Fig. 4 shows the format of a television signal for scrambling a broadcast from a broadcasting station.
In a video signal period, a scrambled specific program, an address code, a program code and a key code are transmitted in the order named. In the vertical blanking period, the program code, codes of I3 and SC, an address mode code, a key mode code, a sto~
code and the like are transmitted in the order named.
. .
In the sound channel, a scrambled program is transmitted. The sound signal may be scrambled by various methods in accordance with the scrambling patterns as described above. Each code is transmit_ed after NR2 modulatiGn of a binarv signal or a predetermined number of bits.
The address code is obtained by coding a number assigned to each subscriber and has a regular mode and a special mode. In the regular mode, the station transmits a number code o~ a subscriber (e.g., a su~scriber who has not payed the prescribed charge) who may not receive an ordinary scrambled program.
When the decoder of such a subscriber receives a number code corresponding to itself, it is rendered inoperative and cannot perform unscrambling. In the special modQ, only a numbe~ code of each subscriber who has contracted to receive a special program ls transmitted. The decoder of a subscriber which receives the number code corresponding to itself can unscramble the program.
The key code is a decoding key code for unscrambling a scrambled signal and has a code for designating, for example, the pattern P1 shown in Fig. lB. According to this embodiment of the present invention, the key code is added at the end of the program. Thus, the scra~bled broadcast may not be unscrambled unless it is once recorded by a VTR or the like. Thus, a scrambled broadcast is recorded on a tape by a VTR and a key code is recorded at the end of the program. The key code is stored in a memorv or the like and the reproduced signal is unscrambled in accordance with the key code. When the key code is added at the end of the program, the program may not be watched in real time. Alternatively, the key code may be added at the start of the program or may be added both at the start and end of the program. Still alternatively, the key code may be added at the start of the program, and may be fetched in the memory after a predetermined period of time from detection of the key code (e.g., after most of the program has been broadcast).
The program code will now be described.
A program code is a code which designates the key code. In order to prevent decoding of a program by non-subscribers, the key code is changed for each year, 12~ ;:397Z
month, week, day, program or the like. Accordingly, when a plurality of programs are recorded on a tape or when a plurality of tapes are to '~e reproduced, various key codes are stored in a memory. A program code has contents of a corresponding program. The memory stores each pair of a program code and a key code corresponding to each other. Accordingly, a key code corresponding to a program may be selected by a program code reproduced during reproduction of the program. In the embodiment of the present invention, the program code is expressed by the date of the broadcast and the program number.
The program code is inserted in the vertical blanking period as shown in Fig. 5 together with ~Ae c^des of he signals ID and SC described above. The program code and the codes of ID and SC are inserted in the 1~1th and 15th horizontal scanning periods (to be referred to as 14H and 15H hereinafter) of the vertical blanking period.
Referring to Fig. S, prog~am codes ~C are inserted for a 70V (V: field period) at intervals of about 20 seconds. In other words, a program code PC is inserted in each 14H and lSH; this is repeated every 20 seconds. Codes of ID and SC are irserted in 14H and 1SH;
this is repeated until the end of the program. When the code of PC and the codes of ID and SC coincide, one of them may be given a priority over the other, which is then deviated from the original position. In this case, it is preferable that the code of PC is deviated.
As may be seen from Fig. 4, a program code is -- 1 o --t.ansmit~ed lOV before the program. During this lOV
period, ~he receiving side detects reception of a scrambled broadcast and the decoder is rendered operative.
When program codes are added during the entire period of the program broadcast as described above, the program code may be immediately detected and the corresponding key code may be designated irrespective of .he reproduction start position of the program. Accordingly, unscrambling may be started immediately even if a pause, FF or RW operation is performed during reproduction.
The address mode code is transmitted during the transmission period of the address code; it represents that the address code is currentlv being transmitted, and also represents one of the regular and special modes. The address mode code is also inserted in 14H and lSH.
The ke~ mode code represents that the key code is ~eing '_ransmitted; it is inserted in 14H and 15-~.
The stop code represents ~hat the scrambling broadcast has been ~rminated; it is inser.ed in 14H and 15H.
The data formats of the respective codes as described a~,ove will ncw be described.
Fig. 6 shows the format or a program oode. The program o~de consists or 24 bits of do to d2~ and represents the broadcastLng date and the ~rogram num~er. Each bit of a program oode is assigned as shown in Fig. 7 in accordance with t~.e oorresponding oontent. Referring to Fig. 6, each of t~.e 14~ and 15H periods of a video signal S is divided into five 7~
subdivided periods, and one bit is assigned to each subdivided period. Note that reference symbol HD
represents a horizontal sync period and SB represents a color burst signal. A guide code representing a program code is added in 14~ and 15H of the first field V1. In the subsequent six fields V2 to V7, bits do to d23 are added as shown in the figure together with error correction codes ~0 to ~4 and "0" bits. The fields V1 to V7 are defined as one pac.~, and are repeated for 70V period (10 packs) at intervals of about 20 seconds, as shown in Fig. 5.
Fig. 8 shows the format of the address code.
In the scrambling broadcasting system according to this embodiment of the present invention, the number of subscribers is designQd to be, for example, several hundred thousands to one million and several hundred thousands. Accordilgly, it is impossible to represent all the subscriber numbers with a limi~ed number of bits. According to this embodimen~
of the present invention, all subscribers are dividea into a plurality of groups and each group is assigned a corresponding number. Accordingly, each subscriber has a subscriber number which consists OL- a group number and his number within the group. In this embodiment, the group number comprises a g-oup code of 20 bits: d to d20. Fifty subscribers are assigned to each group or group number. ~'he fifty subscribers of each group are represented by a home code of 50 bits; 1 bit is assigned to each subscriber in the group. For example, the fifth subscriber within a group identified by a set 12~ Z
of bits dl to d20 may be dl,..., d20, 00". In other words, the fifth bit of the 50-bit home code is set at "1" and the remaining bits are set at "0". Such an address code is inserted in the video signal period together with the program code after the end of the program.
Referring to Fig. 8, the bits dl to d20 representing the group code are inserted in the 30H to 34H period of the signal S. Reference symbols Ml and M2 inserted in 30EI are codes which designate the scrambling broadcasting, for eYample, a broadcasting channe1. El to E50 of a 50-bit home code are divided into two groups which are separately inserted in the 39H to 43H period and in the 43H to 53H period. Note that bit E50 is inserted in 34H, and E~9 is inserted in 35H. Reference symbols C0 to C4 and P denote error correction bits obtained bv tne Hamming coding method.
The "0" bit in each of the 36H to 38E~ period, the 45H to 47H period, and the 54H _o 57H period is a blank time period which is incorporated i!l view of the operation time o. the mic~ocor.puter.
In this manner, the 30H to 56H period represents 50 subscribers of a given group which is designated as group A-l. The codes of the group A-l are inverted to provide an inverted group A-l which is inserted in the 57H to 83H period. The group A-l is used for error correction. The ne.Yt 50 subscribers are grouped to provide a group ~-2 which is inserted in the 8~H to llOH period, and an inverted group A-2 group is inserted. Similarl~, groups A-3, A-3, A-4 and A-4 are Z
similarlS~ inserted to represent a further 200 subscrib~rs. Subse~[uently, together with the bits 80 to 84, tne program code PC as described above is inserted _n he 2~16~ o 251E~ perlod, and "O" blts are inser.ed in .he 252H ~3 254H. An inverted ccde ~C of the o~de PC is inserted ln .he 256H ~ 261H period, and "O" bits are inserted in ~rle 252H t~ 26~H
period. ~he obtained data is defined as one pack ~hich is about one field. The above operation is thererore repeated for each of the even and odd fields. Thus, each pac~ of different 200 subscribers is repeated, and all the subscribers may be represented by a total of N
fields. The first to Nth fields are then repeated wi~h the identical contents for four times I to IV to complete transmission of the address code. The same cc>ntents are transmitted four times so as to prevent detectioa errors or the like by the decoder.
The key code will now be described with referenc~ to Fig. 9.
A key code is transmitted in the video signal period after transmission of ~he address code. A kev code consists of a code of bits dl to d23 each five bits of ~Thich are inserted in the 30H to 38H period, error correction codes C0 to C4, and P. A combination of such a key code with a 3H period of a no signal period (all 'iO" period) is defined as one pack. Data of one pack corresponding to a 9H period is repeated for a lO~ period.
The codes of ID and SC, the address mode code, the key n~de code, and the stop code will now be describe~ with reference to Fig. lO.
~Zl;~7~
Each of these codes is inserted in the 14H to 15H period of the vertical blanking period. Five bits are assigned to each of the 14H and lSH periods, and these codes are inserted in these five bits in a predetermined code pattern.
A transmitter, a decoder at the receiving side of a scrambled broadcasting signal having codes of the formats as described above, and a scrambled program will now be described.
Fig. 11 shows an embodiment of a scrambler ror performing scrambling at the transmitting side.
~ video signal S of a specific program to be scrambled is applied to an input terminal 1, and a sound signal Sa of the program is applied to an input terminal 2. The signal S is sup~lied to a video scrambler 3 as well as to a scene change detector 4 which detects a scene change and produces a scene change identification signal SC as shown in Fig. 3.
A sync separator 5 separates horizontal and vertical syr.c signals HD and VD from the signal S. In accordance with the separated signals HD and VD, a timing generator 6 generates a sync signal and a blanking signal BLK so as to drive a controller 7 and a data insertion circuit 8. In accordance with a command from the controller 7, the data insertion circuit 8 produces data of the respective codes shown in Fig. 4 at predetermined timings. The controller 7 forms a key code pattern P1 shown in Fig. 3 and supplies it to the video scrambler 3 as well as to a sound scrambler 9.
On the basis of the signal SC and the pattern P1, the 9~2 video scramb]er 3 prepares a scrambling pattern P2, P3 or ?4 shown in Fig. 1 and scrambles the signal S
according -to this pattern.
A data/video mixer 10 mi~es the scrambled program with the respective codes and supplies a scrambled video signal Ss to an output terminal 11.
The sound scrambler 3 scrambles the signal S and produces a scrambled sound signal SaS at an output terminal 12.
Fig. 12 shows an embodiment of a decoder at the receiving side. The decoder is connected between a ~TR and a TV monitor.
When a scrambled broadcast program is recorded on a tape by a VTR, the program code and the kev code are stored in a nonvolatile memory 13 in correspondence with each other. The mode of operation of the memory 13 will now be described.
When reproduction from the tape is performed, the reproduced signal Ss is supplied to a video disc urscra~bler 15 through an input terminal 14, while the reproduced signal Sas is supplied to a sound unscrambler 17 through an input terminal 16. A sync separator 1~ separates signals HD and VD from the signal Ss and drives a controller 19 serving also as a code detector and unscramblers 15 and 17. A data separator 20 separates the data of the res?ective codes from the signal Ss and supplies it to the controller 19.
The controller 19 detects codes of ID and SC as well as the program code so as to read out the corresponding key code from the memory 13. The controller 19 then supplies the res?ective codes to an unscrambling pattern generator 21. In accordance with the respective codes, the generator 21 recovers the original scrambling pattern and supplies a resultant unscrambling pattern to the unscramblers 15 and 17.
The unscrambler 15 inverts the polarity or the signal Ss in accordance with the unscrambling 2attern so as to obtain the original signal S, which is then supplied to an output terminal 22. The unscrambler 17 restores the signal Sas to the original signal Sa, which is then supplied at an output terminal 23. The output signals S and Sa are supplied to line-in terminals of the TV
set. It is also possible to convert the frequencies of the signals S and Sa to the empty channel frequency of the TV set by an RF modulator 24, and to supply such converted signals to an antenna e~minal of the TV se-t through an output terminal 25.
Fig. 13 is for e.~plaining the mode of operation of the memory 13 in the recording mode, while Fig. 1~ shows the same in the reproduction mode.
In the recording mode, a code discriminator 27 shown in Fig. 13 detects an address code and an address mode code from a signal supplied from a VTR.
In this mode, the VTR is set in the E-E mode, and a monitoring siynal is supplied to a decoder. In the regular mode, when a decoder address (subscriber number) corresponding to the decoder is included in the received address code, an address coincidence discriminator 28 detects such an address coincidence and stops a write control circuit 29 and a write 7 ~
counter 30. Thus, the memory 13 does not s.ore a key code. When the corres?ondina decoder address is not included in the address code, the discriminator 27 stores the program code and the key code in the memory 13. Accordingly, when a plurality of programs are recorded, program codes PCl to PCN and key codes KYl to XYN are stored in the memory 13 in correspondence ~Jith each other. In the special mode, the codes are stored in the memory 13 only when the decoder address is included in the address code.
In the reproduct~on mode, a code discri~ina~or 31 shown in Fig. ~4 detects the program oode from the reproduced data and supplies it to a PC coincidence discriminator 33. A read counter 32 sequentlally reads out t~e pro~ram o~des PCI to P~ form 'he m~mory 13 and supplies them to the coincidence discriminator 33. When the reproduced program code coincides the readout program code, the corresponding key code is read out. A ROM 34 stores, ~or example, 30 types of unsc~ambling patterns. Data corresponding to the readout key code is read out from the ROM 34. The readout data from the ROM 34 is supplied to the unscrambling pattern generator 21 shown in Fig. l0.
Field of the Invention:
This invention reiates to appara-tus for scrambling information signal, such as television signal, and more particularly, to apparatus for scrambling the television signal in accordance with specified code signal and changes in the scene of the picture of the television signal.
Description of the Prior Art:
A scrambling broadcasting system is conventionally known in which a television signal of a specific program is scrarnbled and transmitted from a broadcasting station and a subscriber who contracts with the broadcasting station and has a decoder can V e~.~J the specific program. In such a system, a broadcasting station transmits a scrambled information signal and a key signal for decoding it. A scrarnbled i.nformation signal is obtained bv inverting a polarity of a television signal or reversing the signal order at a predetermineG period. r non-subscriber is not therefore able to view a correc. image or hear sound even if he can receive the scrambled information signal. ~ccordingly, only subscribers who have contracts with the broadcasting station can unscramble the scrambled information signal in accordance with the key signa] and can view and hear the correc-t image and sound.
In a conventional scramblirlg broadcast,ng system as described above, when a scrambled in_ormation signal is received by a non-subscriber, the received . .
picture mus. be non-sensible. For this purpose, various scrambling methods have been proposed.
~ ne scrambling method is known in which a television signal is inverted at a predetermined field period. According to this method, when a scrambled signal is subject to distortion influence by a transmission system, unscrambling at a receivin~ side may not result in reproduction of an original waveform.
For example, when a polarity-inverted signal is reinverted by a decoder, a level difference may be generated or the waveform may be distorted. When an unscrambled sianal is supplied to a TV receiver, flicker occurs at the polarity-inverted portion of the picture. Such flicker is yarticularly noticeable in the case of a still image. r,7hen a scrambled ~royr m broadcast from a station is recorded bv a VTR, fiicker tends to be caused more rrequently since a VTR is nonlinear in a DC manner as well as in an AC manner.
In order to overcome the aboove-described disacJant_ge, USP 43-0906 discioses improved scrambling system, in which the polarity of the television signal is inverted or reversed when the scene change of the picture in the television signal. According to the system, the flic.~ers in the picture will not be noticeable to the viewers. However, the system has a defect that a scrambling code is easily unscrambled even by viewers who do not contract with the broadcasting station, because the scramDle code is determined only bv the content of the picture in the television signal.
z SU~ARY OF THE INVENTION
_ _ lt is one object of this invention to provide an improved scrambling apparatus which overcomes the above defect.
It is another object of this invention to provide new scrambliny apparatus in which the polarity of the television signal is in~erted or revers2d.
In accordance with an aspect of this invention, the television signal is scrambled b~
invertin~ the television signal in accordance with control signal. The control signal is ~ormed on basis of an identification signal which is generated when a change in the picture scene of the television signaL
and a ~ey code signal which is generated in accordance __ with specific program of the television signal.
BRIEF 3ESCRIPTIO~ OF THE DP~W NGS
Figs. 1A and 1B are timing charts showing an embodlment which performs a scrambling by inverting a polarity of a television signal at a scene change of a picture;
Fig. 2 is a bloc~ diagram of a cLrcuit for practicing the method of Figs. 1A and lB;
Figs. 3A to 3E are timing charts showing an embodiment of the present invention;
Fig. a shows a format of a television signal for a scrambling broadcast;
Flg. 5 shows an arrangement of various codes inserced in the television signal;
Fig. 6 s~ows a format of a program code;
Fig. 7 is a figure for explaining a content '2 of the program code;
~ ig. 8 shows a ~ormat of an address code and the proyram code;
Fig. 9 shows a format of a .~ey code;
Fig~ 10 shows formats of other codes;
Fig. 11 is a block diagram showing an embodi-ment of an apparatus for performing scramblingi Fig. 12 is a block diagram showing an embodi-ment of an apparatus for performing unscrambling;
Fig. 13 is a figure for e~plaining a mode of operation of a memory of the apparatus for performing unscrambling in recording mode for an unscrambled broad-cast hy a VTR; and Fig. 14 is a figure for explaining a mode of operation of the memory in reproduction mode bY the VTR.
DETAILED 3ESCRIPTION OF T~E PREFERRED E~BODIME~TS
Fig. l sho~-s an embodiment wherein the polarity or a television signal is inverted at a scene change of a picture. A scene change identification slgnal SC as shown in Fig. lA is prepared upon ~letection of a scene change portion in a television signal of a given program. In accordance with the scene change identification signal SC thus obtained, a scrambling pattern Pl' for instructing polarity inversion as shown in Fig. lB is generated.
When the pattern Pl' is at high level, for example, polarity inversion of the television signal is performed. In practice, the video signal period of the television signal alone is polarity~inverted, and the blan~ing period is not inverted. When polarity inversion is performed at a scene change, flicker attrlbutable to a level difference or the like as described above occurs simultaneously with a scene change, so that it may be neglected.
Fig. 2 shows an example of a block diagram of a circuit for practicing the method as descrioed above.
A television signal Sv received at an input terminal 101 is supplied to a scrambler 102 as well as to a scene change detector 103 which detects a scene change. Detection of a scene change is performed by differentiating a waveform obtained by integration of the signal Sv. In accordance with a detection output from the detector 103, an IDl generator 104 supplies a scene change identification signal SC to the scrambler 102 Upon reception of each signal SC the scrambler 102 inverts the polarity or the input television signal Sv, e~cep-t for a blanking period, in accordance with the scra~bling pattern Pl' as shown in Fig. lB. The scrambled signal from the scrambler 102 is supplied to an adder 105, and the signal SC is inserted therein. A
scran~bled signal Svs from the adder 105 appears at an output terminal 106. Note that the adder 105 inserts the scene change identification signal SC in a vertical blanking period BL~ or the scrambled signal. At the receiving side, the inserted signal is extrac-ted ~y a decoder and is used for unscrambling. In order to identify the polarity of the signal during unscrambling, the signal SC may include polarity information ~y means of a level di_ference, a pulse width difference or the like.
According to the embodiment as described above, since poLarit-~ inversion of the television signal is performed only upon detection of a scene change, unscrambling by a non-subscriber is too easy and only a less efLective secret transmission system can be provided.
Tne present invention has been provided to solve the above problems with the scrambling method using pola~ity inversion. The present invention will now be described with reference to the accompanying drawings.
Referring to Fig. 3A, a predetermined period T (e.g., 60 seconds) of a television signal of a specific program to be scrambled is preset by an inde~
signal ID. A scene change of such a program is detected so as to obtain a scene change identification signal SC. Then, a key signa~ paltern Pl which concludes within the predetermined period T as shown in Fig. 3B
is prepared. The leading and trailing edges of the pattern Pl coincide with the field ?er~od. In accordance with the signals ID and SC and the pattern Pl as described above, one of scrambling patterns P2, P3 and P4 (Figs. 3C, 3D and 3E) is generated which determines the timing of the polarity inversion.
Scrambling is performed by inverting the polarity of a video signal period of a television signal of a specific program in accordance with the pattern P2, P3 or P4. The key signal pattern Pl lS repeated at period T.
7~
The pattern P2 is obtained by A~Ding the signals ID and SC and the pat-tern Pl and inverting the polarity of the AND product. The pattern P3 rises with the signals ID and SC and falls at the trailing edge of the pattern P1. The pattern P4 rises wlth the ~\~D
product of the signals ID and SC and the pattern Pl and falls at the signal SC.
Various other scrambling patterns for determining the timing of the polarity inversion may also be formed in accordance with the signals ID and SC
and the pattern P1, in addition to those described above.
According to this embodiment, since polarity inversion is always performed at the time of a scene shange, flicker may be neglected. Furthermore, since polarity inversion is performed by comhining a scene change and a key signal pat-tern Pl, high scrambling effects may be obtained. The present invention also makes unscrambling difficult, and is therefore secure.
The signals ID and SC and the pattern P1 are coded to have a predetermined number of bits and are inserted at predetermined positions of the television signal for broadcasting, as will be described later.
At this time, note that the pattern Pl is inserted as a key code signal. The decoder at the receiving side detects the signals ID and SC and the pattern Pl and decodes the scrambling pa-ttern. The decoder unscrambles the signal; it restores the polarity of the 97~, polarity-inverted signal in accordance with the scrambling pattern.
Various signals to be transmitted from a broadcasting station together ~ith the scrambled specific program and a method for transmitting such signals will now be described.
Fig. 4 shows the format of a television signal for scrambling a broadcast from a broadcasting station.
In a video signal period, a scrambled specific program, an address code, a program code and a key code are transmitted in the order named. In the vertical blanking period, the program code, codes of I3 and SC, an address mode code, a key mode code, a sto~
code and the like are transmitted in the order named.
. .
In the sound channel, a scrambled program is transmitted. The sound signal may be scrambled by various methods in accordance with the scrambling patterns as described above. Each code is transmit_ed after NR2 modulatiGn of a binarv signal or a predetermined number of bits.
The address code is obtained by coding a number assigned to each subscriber and has a regular mode and a special mode. In the regular mode, the station transmits a number code o~ a subscriber (e.g., a su~scriber who has not payed the prescribed charge) who may not receive an ordinary scrambled program.
When the decoder of such a subscriber receives a number code corresponding to itself, it is rendered inoperative and cannot perform unscrambling. In the special modQ, only a numbe~ code of each subscriber who has contracted to receive a special program ls transmitted. The decoder of a subscriber which receives the number code corresponding to itself can unscramble the program.
The key code is a decoding key code for unscrambling a scrambled signal and has a code for designating, for example, the pattern P1 shown in Fig. lB. According to this embodiment of the present invention, the key code is added at the end of the program. Thus, the scra~bled broadcast may not be unscrambled unless it is once recorded by a VTR or the like. Thus, a scrambled broadcast is recorded on a tape by a VTR and a key code is recorded at the end of the program. The key code is stored in a memorv or the like and the reproduced signal is unscrambled in accordance with the key code. When the key code is added at the end of the program, the program may not be watched in real time. Alternatively, the key code may be added at the start of the program or may be added both at the start and end of the program. Still alternatively, the key code may be added at the start of the program, and may be fetched in the memory after a predetermined period of time from detection of the key code (e.g., after most of the program has been broadcast).
The program code will now be described.
A program code is a code which designates the key code. In order to prevent decoding of a program by non-subscribers, the key code is changed for each year, 12~ ;:397Z
month, week, day, program or the like. Accordingly, when a plurality of programs are recorded on a tape or when a plurality of tapes are to '~e reproduced, various key codes are stored in a memory. A program code has contents of a corresponding program. The memory stores each pair of a program code and a key code corresponding to each other. Accordingly, a key code corresponding to a program may be selected by a program code reproduced during reproduction of the program. In the embodiment of the present invention, the program code is expressed by the date of the broadcast and the program number.
The program code is inserted in the vertical blanking period as shown in Fig. 5 together with ~Ae c^des of he signals ID and SC described above. The program code and the codes of ID and SC are inserted in the 1~1th and 15th horizontal scanning periods (to be referred to as 14H and 15H hereinafter) of the vertical blanking period.
Referring to Fig. S, prog~am codes ~C are inserted for a 70V (V: field period) at intervals of about 20 seconds. In other words, a program code PC is inserted in each 14H and lSH; this is repeated every 20 seconds. Codes of ID and SC are irserted in 14H and 1SH;
this is repeated until the end of the program. When the code of PC and the codes of ID and SC coincide, one of them may be given a priority over the other, which is then deviated from the original position. In this case, it is preferable that the code of PC is deviated.
As may be seen from Fig. 4, a program code is -- 1 o --t.ansmit~ed lOV before the program. During this lOV
period, ~he receiving side detects reception of a scrambled broadcast and the decoder is rendered operative.
When program codes are added during the entire period of the program broadcast as described above, the program code may be immediately detected and the corresponding key code may be designated irrespective of .he reproduction start position of the program. Accordingly, unscrambling may be started immediately even if a pause, FF or RW operation is performed during reproduction.
The address mode code is transmitted during the transmission period of the address code; it represents that the address code is currentlv being transmitted, and also represents one of the regular and special modes. The address mode code is also inserted in 14H and lSH.
The ke~ mode code represents that the key code is ~eing '_ransmitted; it is inserted in 14H and 15-~.
The stop code represents ~hat the scrambling broadcast has been ~rminated; it is inser.ed in 14H and 15H.
The data formats of the respective codes as described a~,ove will ncw be described.
Fig. 6 shows the format or a program oode. The program o~de consists or 24 bits of do to d2~ and represents the broadcastLng date and the ~rogram num~er. Each bit of a program oode is assigned as shown in Fig. 7 in accordance with t~.e oorresponding oontent. Referring to Fig. 6, each of t~.e 14~ and 15H periods of a video signal S is divided into five 7~
subdivided periods, and one bit is assigned to each subdivided period. Note that reference symbol HD
represents a horizontal sync period and SB represents a color burst signal. A guide code representing a program code is added in 14~ and 15H of the first field V1. In the subsequent six fields V2 to V7, bits do to d23 are added as shown in the figure together with error correction codes ~0 to ~4 and "0" bits. The fields V1 to V7 are defined as one pac.~, and are repeated for 70V period (10 packs) at intervals of about 20 seconds, as shown in Fig. 5.
Fig. 8 shows the format of the address code.
In the scrambling broadcasting system according to this embodiment of the present invention, the number of subscribers is designQd to be, for example, several hundred thousands to one million and several hundred thousands. Accordilgly, it is impossible to represent all the subscriber numbers with a limi~ed number of bits. According to this embodimen~
of the present invention, all subscribers are dividea into a plurality of groups and each group is assigned a corresponding number. Accordingly, each subscriber has a subscriber number which consists OL- a group number and his number within the group. In this embodiment, the group number comprises a g-oup code of 20 bits: d to d20. Fifty subscribers are assigned to each group or group number. ~'he fifty subscribers of each group are represented by a home code of 50 bits; 1 bit is assigned to each subscriber in the group. For example, the fifth subscriber within a group identified by a set 12~ Z
of bits dl to d20 may be dl,..., d20, 00". In other words, the fifth bit of the 50-bit home code is set at "1" and the remaining bits are set at "0". Such an address code is inserted in the video signal period together with the program code after the end of the program.
Referring to Fig. 8, the bits dl to d20 representing the group code are inserted in the 30H to 34H period of the signal S. Reference symbols Ml and M2 inserted in 30EI are codes which designate the scrambling broadcasting, for eYample, a broadcasting channe1. El to E50 of a 50-bit home code are divided into two groups which are separately inserted in the 39H to 43H period and in the 43H to 53H period. Note that bit E50 is inserted in 34H, and E~9 is inserted in 35H. Reference symbols C0 to C4 and P denote error correction bits obtained bv tne Hamming coding method.
The "0" bit in each of the 36H to 38E~ period, the 45H to 47H period, and the 54H _o 57H period is a blank time period which is incorporated i!l view of the operation time o. the mic~ocor.puter.
In this manner, the 30H to 56H period represents 50 subscribers of a given group which is designated as group A-l. The codes of the group A-l are inverted to provide an inverted group A-l which is inserted in the 57H to 83H period. The group A-l is used for error correction. The ne.Yt 50 subscribers are grouped to provide a group ~-2 which is inserted in the 8~H to llOH period, and an inverted group A-2 group is inserted. Similarl~, groups A-3, A-3, A-4 and A-4 are Z
similarlS~ inserted to represent a further 200 subscrib~rs. Subse~[uently, together with the bits 80 to 84, tne program code PC as described above is inserted _n he 2~16~ o 251E~ perlod, and "O" blts are inser.ed in .he 252H ~3 254H. An inverted ccde ~C of the o~de PC is inserted ln .he 256H ~ 261H period, and "O" bits are inserted in ~rle 252H t~ 26~H
period. ~he obtained data is defined as one pack ~hich is about one field. The above operation is thererore repeated for each of the even and odd fields. Thus, each pac~ of different 200 subscribers is repeated, and all the subscribers may be represented by a total of N
fields. The first to Nth fields are then repeated wi~h the identical contents for four times I to IV to complete transmission of the address code. The same cc>ntents are transmitted four times so as to prevent detectioa errors or the like by the decoder.
The key code will now be described with referenc~ to Fig. 9.
A key code is transmitted in the video signal period after transmission of ~he address code. A kev code consists of a code of bits dl to d23 each five bits of ~Thich are inserted in the 30H to 38H period, error correction codes C0 to C4, and P. A combination of such a key code with a 3H period of a no signal period (all 'iO" period) is defined as one pack. Data of one pack corresponding to a 9H period is repeated for a lO~ period.
The codes of ID and SC, the address mode code, the key n~de code, and the stop code will now be describe~ with reference to Fig. lO.
~Zl;~7~
Each of these codes is inserted in the 14H to 15H period of the vertical blanking period. Five bits are assigned to each of the 14H and lSH periods, and these codes are inserted in these five bits in a predetermined code pattern.
A transmitter, a decoder at the receiving side of a scrambled broadcasting signal having codes of the formats as described above, and a scrambled program will now be described.
Fig. 11 shows an embodiment of a scrambler ror performing scrambling at the transmitting side.
~ video signal S of a specific program to be scrambled is applied to an input terminal 1, and a sound signal Sa of the program is applied to an input terminal 2. The signal S is sup~lied to a video scrambler 3 as well as to a scene change detector 4 which detects a scene change and produces a scene change identification signal SC as shown in Fig. 3.
A sync separator 5 separates horizontal and vertical syr.c signals HD and VD from the signal S. In accordance with the separated signals HD and VD, a timing generator 6 generates a sync signal and a blanking signal BLK so as to drive a controller 7 and a data insertion circuit 8. In accordance with a command from the controller 7, the data insertion circuit 8 produces data of the respective codes shown in Fig. 4 at predetermined timings. The controller 7 forms a key code pattern P1 shown in Fig. 3 and supplies it to the video scrambler 3 as well as to a sound scrambler 9.
On the basis of the signal SC and the pattern P1, the 9~2 video scramb]er 3 prepares a scrambling pattern P2, P3 or ?4 shown in Fig. 1 and scrambles the signal S
according -to this pattern.
A data/video mixer 10 mi~es the scrambled program with the respective codes and supplies a scrambled video signal Ss to an output terminal 11.
The sound scrambler 3 scrambles the signal S and produces a scrambled sound signal SaS at an output terminal 12.
Fig. 12 shows an embodiment of a decoder at the receiving side. The decoder is connected between a ~TR and a TV monitor.
When a scrambled broadcast program is recorded on a tape by a VTR, the program code and the kev code are stored in a nonvolatile memory 13 in correspondence with each other. The mode of operation of the memory 13 will now be described.
When reproduction from the tape is performed, the reproduced signal Ss is supplied to a video disc urscra~bler 15 through an input terminal 14, while the reproduced signal Sas is supplied to a sound unscrambler 17 through an input terminal 16. A sync separator 1~ separates signals HD and VD from the signal Ss and drives a controller 19 serving also as a code detector and unscramblers 15 and 17. A data separator 20 separates the data of the res?ective codes from the signal Ss and supplies it to the controller 19.
The controller 19 detects codes of ID and SC as well as the program code so as to read out the corresponding key code from the memory 13. The controller 19 then supplies the res?ective codes to an unscrambling pattern generator 21. In accordance with the respective codes, the generator 21 recovers the original scrambling pattern and supplies a resultant unscrambling pattern to the unscramblers 15 and 17.
The unscrambler 15 inverts the polarity or the signal Ss in accordance with the unscrambling 2attern so as to obtain the original signal S, which is then supplied to an output terminal 22. The unscrambler 17 restores the signal Sas to the original signal Sa, which is then supplied at an output terminal 23. The output signals S and Sa are supplied to line-in terminals of the TV
set. It is also possible to convert the frequencies of the signals S and Sa to the empty channel frequency of the TV set by an RF modulator 24, and to supply such converted signals to an antenna e~minal of the TV se-t through an output terminal 25.
Fig. 13 is for e.~plaining the mode of operation of the memory 13 in the recording mode, while Fig. 1~ shows the same in the reproduction mode.
In the recording mode, a code discriminator 27 shown in Fig. 13 detects an address code and an address mode code from a signal supplied from a VTR.
In this mode, the VTR is set in the E-E mode, and a monitoring siynal is supplied to a decoder. In the regular mode, when a decoder address (subscriber number) corresponding to the decoder is included in the received address code, an address coincidence discriminator 28 detects such an address coincidence and stops a write control circuit 29 and a write 7 ~
counter 30. Thus, the memory 13 does not s.ore a key code. When the corres?ondina decoder address is not included in the address code, the discriminator 27 stores the program code and the key code in the memory 13. Accordingly, when a plurality of programs are recorded, program codes PCl to PCN and key codes KYl to XYN are stored in the memory 13 in correspondence ~Jith each other. In the special mode, the codes are stored in the memory 13 only when the decoder address is included in the address code.
In the reproduct~on mode, a code discri~ina~or 31 shown in Fig. ~4 detects the program oode from the reproduced data and supplies it to a PC coincidence discriminator 33. A read counter 32 sequentlally reads out t~e pro~ram o~des PCI to P~ form 'he m~mory 13 and supplies them to the coincidence discriminator 33. When the reproduced program code coincides the readout program code, the corresponding key code is read out. A ROM 34 stores, ~or example, 30 types of unsc~ambling patterns. Data corresponding to the readout key code is read out from the ROM 34. The readout data from the ROM 34 is supplied to the unscrambling pattern generator 21 shown in Fig. l0.
Claims (16)
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. In an apparatus for scrambling a television signal by inversion thereof in response to a control signal, the combination comprising:
means for detecting a change in the scene represented by the television signal during a specific program thereof and generating a scene change identification signal in response thereto;
means for generating a key code signal having a predetermined pattern independent of any content of said television signal and associated with said specific program of the television signal; and means for combining said scene change identification signal and said key code signal to produce said control signal having a control pattern indicative of said scene change identification signal and said key code signal only in combination, said television signal being inverted in accordance with said control pattern so as to be reproducible without noticeable flicker.
means for detecting a change in the scene represented by the television signal during a specific program thereof and generating a scene change identification signal in response thereto;
means for generating a key code signal having a predetermined pattern independent of any content of said television signal and associated with said specific program of the television signal; and means for combining said scene change identification signal and said key code signal to produce said control signal having a control pattern indicative of said scene change identification signal and said key code signal only in combination, said television signal being inverted in accordance with said control pattern so as to be reproducible without noticeable flicker.
2. An apparatus according to claim 1, in which said key code signal generating means controls said predetermined pattern of said key code signal to repeat at a predetermined interval.
3. An apparatus according to claim 2, in which said key code signal generating means comprises means for producing a key code identification signal at every said predetermined interval, said key code identification signal being inserted in a vertical blanking period of said television signal.
4. An apparatus according to claim 3, in which said scene change and key code identification signals have specific code patterns, respectively, which are inserted into a predetermined horizontal period of said vertical blanking period.
5. An apparatus according to claim 4, in which said combining means comprises an AND circuit receiving said scene change identification signal and said key code signal, whereby said scene change identification signal gated by said key code signal is said control signal.
6. An apparatus according to claim 4, in which said combining means comprises means for forming said control signal in response to said scene change and key code identi-fication signals and starting and the starting and trailing edges of said key code signal.
7. An apparatus according to claim 6, in which said control signal comprises a rectangular signal which is set by one of said scene change identification signal and said key code identification signal in combination therewith, and which is reset by said trailing edge of the key code signal.
8. An apparatus according to claim 6, in which said control signal comprises a rectangular signal which is set by one of said scene change identification signal and said key code identification signal gated by said key code signal, and which is reset by said scene change identification signal.
9. An apparatus according to claim 3, wherein said means for producing said key code identification signal includes mixing means for inserting said key code identifica-tion signal into said vertical blanking period in response to said control signal from said combining means.
10. An apparatus according to claim 1, in which said television signal has a video signal component; and wherein said means for combining includes video scrambler means for scrambling said video signal component in response to said control signal.
11. An apparatus according to claim 1, in which said television signal has an audio signal component; and further comprising audio scrambler means for scrambling said audio signal component in response to said key code signal.
12. An apparatus for descrambling a television signal of a specific program thereof scrambled in accordance with a transmitted key code signal selected from said specific program and independent of the content thereof together with a scene change identification signal indicative of a change in the scene represented by the television signal during said specific program, said scene change identification signal and a program code identifying said specific program being added to said scrambled television signal and transmitted therewith, said apparatus comprising:
memory means for storing said transmitted key code signal;
code detector means for detecting said program code and said scene change identification signal transmitted with the scrambled television signal;
means for retrieving said key code signal from said memory means in response to the detecting of said program code; and means employing said key code signal retrieved from said memory means in combination with said scene change identifi-cation signal for descrambling said scrambled television signal so as to reproduce the same without noticeable flicker.
memory means for storing said transmitted key code signal;
code detector means for detecting said program code and said scene change identification signal transmitted with the scrambled television signal;
means for retrieving said key code signal from said memory means in response to the detecting of said program code; and means employing said key code signal retrieved from said memory means in combination with said scene change identifi-cation signal for descrambling said scrambled television signal so as to reproduce the same without noticeable flicker.
13. The apparatus of claim 12; wherein said means employing said key code signal includes descramble pattern generator means for generating a descramble pattern signal in response to said key code signal means, video descrambler means for descrambling the video portion of said scrambled television signal in response to said descramble pattern signal, and audio descrambler means for descrambling the audio portion of said scrambled television signal in response to said descramble pattern signal.
14. The apparatus of claim 13; and further comprising sync signal separating means for separating horizontal and vertical sync signals included in said scrambled television signal and supplying said sync signals to said code detector means and said audio and video descrambler means.
15. The apparatus of claim 13; and further comprising RF modulating means for receiving the descrambled audio and video portions of said scrambled television signal from said audio and video descrambler means and converting said signals to predetermined television channel frequency signals.
16. The apparatus of claim 12; and further comprising code separating means for separating said program code and key code signals from said scrambled television signal and supplying the seperated program and key code signals to said code detector means.
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Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| EP83304084A EP0131663B1 (en) | 1983-07-13 | 1983-07-13 | Apparatus for scrambling a television signal |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1213972A true CA1213972A (en) | 1986-11-12 |
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| CA000432292A Expired CA1213972A (en) | 1983-07-13 | 1983-07-12 | Apparatus for scrambling a television signal |
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| US (1) | US4700388A (en) |
| EP (1) | EP0131663B1 (en) |
| AU (1) | AU567879B2 (en) |
| CA (1) | CA1213972A (en) |
| DE (1) | DE3378247D1 (en) |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JPS6016083A (en) * | 1983-07-07 | 1985-01-26 | Sony Corp | Television signal transmission system |
| JPS6016082A (en) * | 1983-07-07 | 1985-01-26 | Sony Corp | Transmission system of scramble television signal |
| GB2180127B (en) * | 1985-09-04 | 1989-08-23 | Philips Electronic Associated | Method of data communication |
| US4942466A (en) * | 1985-12-24 | 1990-07-17 | British Broadcasting Corporation | Bandwidth compression for television signals |
| GB2185664B (en) * | 1986-01-17 | 1989-10-25 | Philips Electronic Associated | Teletext transmission systems |
| FR2621204B1 (en) * | 1987-09-24 | 1994-07-01 | Aeta | METHOD AND DEVICE FOR ANALOGUE ENCRYPTION / DECRYPTION OF AN ANALOGUE VIDEO SIGNAL |
| US5003590A (en) * | 1989-12-18 | 1991-03-26 | Eidak Corporation | Encoding an optical video disc to inhibit video tape recording |
| US5091938B1 (en) * | 1990-08-06 | 1997-02-04 | Nippon Denki Home Electronics | Digital data cryptographic system |
| EP0619677A3 (en) * | 1993-04-09 | 1995-03-08 | Matsushita Electric Ind Co Ltd | System for scrambling a digital video signal. |
| US5617149A (en) * | 1994-11-22 | 1997-04-01 | Electronics And Telecommunications Research Institute | Apparatus and method for detecting scene changes using the difference of mad between image frames |
| JP3692838B2 (en) * | 1999-06-22 | 2005-09-07 | 日本ビクター株式会社 | Recording method, reproducing method, reproducing apparatus and recording medium |
| US20070180130A1 (en) * | 2006-02-01 | 2007-08-02 | Arnold William C | Method and apparatus for multi-protocol digital communications |
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| GB841627A (en) * | 1956-12-20 | 1960-07-20 | Rank Organisation Ltd | Improvements in or relating to television systems |
| CH540613A (en) * | 1970-12-08 | 1973-08-15 | Gretag Ag | Method and device for encrypted message transmission |
| US4075660A (en) * | 1972-02-18 | 1978-02-21 | Teleglobe Pay-Tv System, Inc. | Pay television system with synchronization suppression |
| US3919462A (en) * | 1973-08-15 | 1975-11-11 | System Dev Corp | Method and apparatus for scrambling and unscrambling communication signals |
| US4340906A (en) * | 1980-05-14 | 1982-07-20 | Oak Industries Inc. | Video signal coding by video signal polarity reversal on the basis of brightness level comparison |
| AU562395B2 (en) * | 1981-09-10 | 1987-06-11 | Sony Corporation | Subscription television system |
| US4454543A (en) * | 1981-11-06 | 1984-06-12 | Oak Industries Inc. | Dynamic video scrambling |
| US4484027A (en) * | 1981-11-19 | 1984-11-20 | Communications Satellite Corporation | Security system for SSTV encryption |
| US4514761A (en) * | 1982-08-23 | 1985-04-30 | Zenith Electronics Corporation | Data encryption technique for subscription television system |
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1983
- 1983-07-12 CA CA000432292A patent/CA1213972A/en not_active Expired
- 1983-07-13 DE DE8383304084T patent/DE3378247D1/en not_active Expired
- 1983-07-13 EP EP83304084A patent/EP0131663B1/en not_active Expired
- 1983-07-15 AU AU16874/83A patent/AU567879B2/en not_active Ceased
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1986
- 1986-08-25 US US06/899,798 patent/US4700388A/en not_active Expired - Fee Related
Also Published As
| Publication number | Publication date |
|---|---|
| EP0131663A1 (en) | 1985-01-23 |
| DE3378247D1 (en) | 1988-11-17 |
| AU567879B2 (en) | 1987-12-10 |
| EP0131663B1 (en) | 1988-10-12 |
| AU1687483A (en) | 1985-01-17 |
| US4700388A (en) | 1987-10-13 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| MKEX | Expiry | ||
| MKEX | Expiry |
Effective date: 20031112 |