EP0105906A1 - Dispositif de brouillage audio utilisant un canal auxiliaire pour la synchronisation du dipsositif de debrouillage - Google Patents

Dispositif de brouillage audio utilisant un canal auxiliaire pour la synchronisation du dipsositif de debrouillage

Info

Publication number
EP0105906A1
EP0105906A1 EP19830901503 EP83901503A EP0105906A1 EP 0105906 A1 EP0105906 A1 EP 0105906A1 EP 19830901503 EP19830901503 EP 19830901503 EP 83901503 A EP83901503 A EP 83901503A EP 0105906 A1 EP0105906 A1 EP 0105906A1
Authority
EP
European Patent Office
Prior art keywords
audio signal
digital
signal
scrambled
generate
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.)
Withdrawn
Application number
EP19830901503
Other languages
German (de)
English (en)
Inventor
Leslie D. Thomas
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
CBS Corp
Original Assignee
Westinghouse Electric Corp
Priority date (The priority date 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 date listed.)
Filing date
Publication date
Application filed by Westinghouse Electric Corp filed Critical Westinghouse Electric Corp
Publication of EP0105906A1 publication Critical patent/EP0105906A1/fr
Withdrawn legal-status Critical Current

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
    • H—ELECTRICITY
    • H04—ELECTRIC COMMUNICATION TECHNIQUE
    • H04K—SECRET COMMUNICATION; JAMMING OF COMMUNICATION
    • H04K1/00—Secret communication
    • H04K1/02—Secret communication by adding a second signal to make the desired signal unintelligible
    • 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
    • H04N7/169—Systems operating in the time domain of the television signal
    • H04N7/1696—Systems operating in the time domain of the television signal by changing or reversing the order of active picture signal portions

Definitions

  • the invention relates generally to audio trans ⁇ mission systems and more specifically to an audio trans- mission system in which the audio is first converted to a digital signal which is then scrambled and reconverted to an audio signal for transmission with the descrambler at the utilization point being synchronized using data trans ⁇ mitted via an auxiliary channel.
  • the invention comprises a method and apparatus for scrambling an audio signal. Scrambling is accomplished by sampling and digitizing the audio to produce digital numbers to which a random digital code is added. The digital numbers are then reconverted to an audio signal to produce a scrambled analog audio signal. This analog audio signal is then transmitted over a normal audio channel of limited bandwidth, for example, 15 KHZ. Synchronization at the receiving station for purposes of descrambling is accomplished utilizing a parallel auxiliary channel of high bandwidth such as a TV video channel. In an exemplary system, a digital number specifying the starting point of the random number gener- ator is transmitted during an unused video line of the vertical blanking interval.
  • Descrambling is accomplished by separating the digitial number specifying the starting point of the random number generator from the TV signal and utilizing _this number to set the starting point of a random number generator.
  • the audio is sampled to generate a series of digital numbers which are subtracted from the random number to descramble the digitized audio signal.
  • the digital numbers are then converted to analog and filtered to reproduce the original audio signal.
  • Figure 1 is a generalized block diagram of the invention
  • Figure 2 is a block illustrating the scrambling technique as applied to a TV signal
  • Figure 3 is a diagram illustrating the transmis ⁇ sion of the synchronization code during the vertical blanking interval of the TV video signal
  • Figure 4 is a block diagram illustrating another embodiment of the invention in which a broad band channel is utilized to synchronize descrambling of an independent audio channel.
  • FIG. 1 is a diagram illustrating a firs embodiment of the invention.
  • the basic scrambler digitizes the audio signal and combines the digitized audio signal with digital pseudo-random numbers.
  • Synchronizatio signals and a digital pseudo-random signal for scrambling the audio signal are provided by a scrambler synchroniza ⁇ tion generator 10.
  • Synchronizing data from the scrambler synchronization generator 10 is coupled to the input of a multiplexer 12 and combined with a data signal to generate a composite signal comprising the data signal and the synchronizing code.
  • the synchronization code contains relatively high frequency components in order to adequately synchronize descrambling of the audio signal.
  • the composite output signal of the multiplexer 12 which includes a data signal combined with the synchronization code, is coupled to a transmitter 14 for transmission to a remote location. It is contemplated that the composite signal will be transmitted to a remote location by modu ⁇ lating a radio frequency carrier. Transmission is accom ⁇ plished by coupling the composite signal to modulate an exemplary transmitter 14. .
  • the pseudo-random digital numbers from the scrambler synch generator 10 are coupled to the input of an audio scrambler 16.
  • the audio scrambler 16 digitizes the audio signal and combines the digitized audio signal with the pseudo-random numbers from the synchronization generator 10 to produce a scrambled digital signal.
  • the scrambled digital audio signal is converted to a scrambled analog audio signal for transmission. Since the synchro ⁇ nizing code is transmitted over an independent broadband channel, the scrambled analog audio signal does not include any information for synchronizing the receiving station descrambler with the scrambler.
  • a conventional radio frequency analog transmit ⁇ ter 18 receives as an input the scrambled analog audio signal for transmission to the remote location. In most applications it is contemplated that transmission will be accomplished by modulating a radio frequency carrier with the scrambled audio signal. However, other transmission techniques are usable.
  • a radio frequency receiver 20 detects the modulated radio frequency signal, recovers and couples the scrambled analog audio signal to a de ⁇ scrambler 22.
  • a synchronization signal receiver 24 detects the output signal of the high bandwidth transmitter 14 and recovers from this signal the synchronization code which was originally generated by the scrambler and sync gener- ator 10. This synchronization code is coupled to the descrambler 22 and utilized to synchronize a pseudo-random number generator to generate a pseudo-random signal which is utilized by the audio descrambler 22 to reproduce the descrambled audio signal.
  • This system can be assembled using well known circuit techniques and apparatus.
  • De ⁇ scrambling is the inverse of the scrambling previously described.
  • the above-described system is most conveniently applied in situations where the data signal to the multi- plexer 12 contains some unused time portions which may be utilized, to transmit the synchronizing code.
  • Typical examples of such a signal is a standard TV signal in which the unused lines of the vertical blanking interval can be conveniently used to transmit the synchronizing code.
  • FIG 2. Another embodiment of the invention, as applied to a standard TV signal, is illustrated in Figure 2.
  • the standard TV signal is generated by a conventional color TV camera 26, for example.
  • the com ⁇ posite video signal, including the video and all the normal TV synchronization signals, is coupled to a coding circuit 28 where the random number generator synchronizing code is inserted in the vertical blanking interval of the
  • Synchronization signals from the camera 2 are coupled to an analog-to-digital converter 30 to syn chronize this circuit such that the audio input signal i sampled at a rate which is synchronized with the TV syn signals including the color burst.
  • Pseudo-random digita numbers are sequentially generated by a random numbe generator 32. These pseudo random numbers are also syn chronized with the TV sync signals, including the colo burst. Scrambling of the audio signal is accomplished b coupling the digital output signals from the analog-to- digital converter 30 and the pseudo-random numbers fro the pseudo-random number generator 32 to the inputs of a digital adder 3.4.
  • the output signals of the adder 34 are coupled as in input to a digital-to-analog converter 36 to generate at the output of the analog-to-digital converter 36 the scrambled audio signal.
  • Communication means 38 a standard TV transmitting system for example, receives as an input the scrambled audio and video signals for trans ⁇ mission to a remote location. Coding means may also include conventional apparatus for scrambling the video signal, if desired.
  • both the audio and video signals are coupled to a video audio separation circuit of 40.
  • the video signal if scrambled, is descrambled using conventional techniques and coupled to a display 42 and to a synchronization separation circuit 44.
  • the display 42 may simply be a conventional TV type display, for example.
  • Sync separation- circuit 44 -separates- the horizontal and vertical synchronizing pulses of the TV signal and the codes used to synchronize the random number generator 32.
  • the horizontal synchronizing pulses, the vertical synchro ⁇ nizing pulses and the color burst signal are coupled to.
  • an analog-to-digital converter 46 to synchronize this circuit to sample the scrambled audio si-gnal from the video audio separating circuit 40 at precisely the same rate that the audio signal was sampled at the point of origination.
  • the digital numbers generated by the analog-to-digital con- verter 46 and the pseudo-random numbers generated by the random number generator 48 are coupled as inputs to an adder 50.
  • the adder 50 performs an inverse operation to the adder 34 to generate at the output of this circuit a 5 digital, but descrambled audio signal.
  • the descrambled audio signal is coupled to the input of a digital-to- analog converter 52 to generate a descrambled audio signal which is filtered by a filter circuit 54 to reproduce the original audio.
  • Figure 3 is a diagram illustrating the prior art technique used for coding the television signal for secur ⁇ ity purposes and for transmitting the synchronizing codes for the random number generators. This is the same tech ⁇ nique used for coding the video signals as more fully
  • the video signal is digitized to generate a digital number which is stored in a memory.
  • R is a random number which is determined by a random number generator. This results in the transmitted video signal being scrambled. At the receiver the process is reversed to recreate the original video signal.
  • r QMP transmit synchronizing codes permitting the random co generator at the point of use to be synchronized to t similar generator at the point of origination.
  • Th synchronization code can be conveniently transmitt during the last line of the vertical blanking interval illustrated in line 3 of Figure 3.
  • Line 4 indicates typical synchronizing code which is transmitted during t
  • Th technique can be used to transmit the sync codes for t random number generator illustrated in Figure 3. As obvious from the above description the remainder of t lines of the vertical blanking interval are available f other uses.
  • FIG. 4 illustrates another embodiment of t invention in which an independent audio signal is scra bled and descrambled using synchronizing signals tran mitted over an independent high bandwidth channel such a TV video channel.
  • a standard conve tional TV signal is generated by a video signal generato 56.
  • the video signal generator 56 also generates t conventional TV synchronizing signals which are coupled t a random number generator 58.
  • the random number generato 58 is in turn coupled to a video combiner 60 to combin the synchronizing code _for the random number generato with the TV signal.
  • the TV audio signal in this embodi ment is generated by the audio section 62 and in thi embodiment is coupled directly to the TV transmitter 6 and transmitted"without • scrambling.
  • the video signal including the random numbe generator sync code and the unscrambled audio signal ar coupled to conventional TV transmitting apparatus 64 fo transmitting to a remote location.
  • An independent audio source 66 which is no associated in any way with the TV signal is generated b an audio source 66.
  • This audio signal and random number from the random number generator 58 are coupled to th inputs of an audio scrambler circuit 68 of the type pre
  • the scrambled audio signal of the audio scrambler 68 is transmitted to a remote location by an audio transmitting apparatus 70.
  • the television signal is received by a sync receiving circuit 72 and decoded to recover the synchronizing code and the TV sync pulses to synchronize the descrambling apparatus 74 as described in the previous embodiment.
  • the second input to the descrambler 74 is the scrambled audio signal.
  • the descrambler 74 descrambles the audio signal using techniques previously described with reference to other embodiments. This embodiment permits an audio scrambler to be synchronized by information transmitted over the non-related high bandwidth signal.

Landscapes

  • Engineering & Computer Science (AREA)
  • Signal Processing (AREA)
  • Multimedia (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Two-Way Televisions, Distribution Of Moving Picture Or The Like (AREA)
  • Synchronisation In Digital Transmission Systems (AREA)

Abstract

Mode de réalisation à titre d'exemple de l'invention utilisant le canal vidéo d'un signal de télévision pour transmettre des codes de synchronisation pour un dispositif de brouillage audio (34). Le brouillage du signal audio est obtenu en numérisant ce signal audio et en additionnant (34) à chaque échantillon un nombre numérique pseudo-aléatoire. Les nombres numériques résultants sont convertis sous une forme analogique pour la transmission. Un signal numérique spécifiant le point de départ du générateur de nombres pseudo-aléatoires est inséré (28) dans la portion vidéo d'une ligne de l'intervalle d'effacement vertical du signal de télévision. Au poste récepteur, le nombre numérique spécifiant le point de départ du générateur de nombre pseudo-aléatoires est utilisé pour fixer le point de départ d'un générateur de nombres pseudo-aléatoires (48) qui produit les nombres qui sont utilisés pour débrouiller (50) le signal audio.
EP19830901503 1982-04-08 1983-03-23 Dispositif de brouillage audio utilisant un canal auxiliaire pour la synchronisation du dipsositif de debrouillage Withdrawn EP0105906A1 (fr)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
US36662482A 1982-04-08 1982-04-08
US366624 1982-04-08

Publications (1)

Publication Number Publication Date
EP0105906A1 true EP0105906A1 (fr) 1984-04-25

Family

ID=23443804

Family Applications (1)

Application Number Title Priority Date Filing Date
EP19830901503 Withdrawn EP0105906A1 (fr) 1982-04-08 1983-03-23 Dispositif de brouillage audio utilisant un canal auxiliaire pour la synchronisation du dipsositif de debrouillage

Country Status (4)

Country Link
EP (1) EP0105906A1 (fr)
CA (1) CA1204162A (fr)
IE (1) IE55744B1 (fr)
WO (1) WO1983003731A1 (fr)

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
GB2140656A (en) * 1983-05-13 1984-11-28 Philips Electronic Associated Television transmission system
DE3343307A1 (de) * 1983-11-30 1985-06-05 Blaupunkt-Werke Gmbh, 3200 Hildesheim Verfahren zum verschluesseln und entschluesseln von analogen signalen, sowie schaltungsanordnung zur durchfuehrung des verfahrens
US4599646A (en) * 1984-05-18 1986-07-08 D-Tec Industries, Inc. Method and apparatus for identifying unauthorized or defective converter/decoder boxes in CATV system

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3746799A (en) * 1971-09-27 1973-07-17 Us Navy Method and apparatus for encoding and decoding analog signals
US4086435A (en) * 1976-09-17 1978-04-25 Biosystems Research Group Ii Method of and means for scrambling and descrambling speech at audio frequencies
US4221931A (en) * 1977-10-17 1980-09-09 Harris Corporation Time division multiplied speech scrambler
US4215366A (en) * 1977-10-19 1980-07-29 Feature Film Services Subscriber-limited reception television broadcast security encoder-decoder system
US4295223A (en) * 1979-04-25 1981-10-13 Westinghouse Electric Corp. Digital signal/noise ratio amplifier apparatus for a communication system
US4318125A (en) * 1979-04-25 1982-03-02 Westinghouse Electric Corp. Solid state digital audio scrambler system for teletransmission of audio intelligence through a television system

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
See references of WO8303731A1 *

Also Published As

Publication number Publication date
CA1204162A (fr) 1986-05-06
WO1983003731A1 (fr) 1983-10-27
IE830565L (en) 1983-10-08
IE55744B1 (en) 1991-01-02

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Effective date: 19840312

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Inventor name: THOMAS, LESLIE D.