Method for scrambling a television signal and method and apparatus for descrambling a scrambled television signal

• US 5,113,441 A
• Filed: 02/20/1990
• Issued: 05/12/1992
• Est. Priority Date: 04/21/1989
• Status: Expired due to Fees

• Current Assignee: Pioneer Electronics (USA) Incorporated (Pioneer Corporation)
• Original Assignee: Pioneer Electronics Corporation (Pioneer Corporation)
• Inventors: Harada, Kimihito
• Primary Examiner(s): Tarcza, Thomas H.
• Assistant Examiner(s): Cain, David
• Application Number:
  US07/481,270
• Time in Patent Office: 812 Days
• Field of Search: 380/10, 380/20, 380/15, 380/19, 380/20
• US Class Current: 380/223
• CPC Class Codes: H04N 7/1675 Providing digital key or authorisation information for generation or regeneration of the scrambling sequence pseudo-random number generators in general G06F7/58
• CPC Class Codes: H04N 7/1713 by modifying synchronisation signals

Abstract

A method of scrambling a television signal and a method of and apparatus for descrambling a television signal is provided. An audio signal is used on which a key signal containing compression information and information concerning the position of a vertical blanking interval is superimposed on a portion of the audio signal corresponding to a horizontal blanking interval. In addition, a pseudo-key signal is superimposed on the audio signal at a portion which corresponds to a vertical blanking interval, so that the vertical blanking interval cannot be detected through the detection of the audio signal. As a result, an expansion signal for expanding the signal in the horizontal blanking interval and vertical blanking interval compressed by scrambling cannot be formed in its normal position. Thus, unauthorized access is difficult. Descrambling can be performed by detecting the vertical blanking interval based on the information concerning the position of the vertical blanking interval contained in the key signal, and decoding the information for the position which is transmitted in the form of out-band data. Compression information can then be extracted from the key signal based on the detected vertical blanking interval, and an expansion signal for expanding the signal in the horizontal and vertical blanking periods can be generated.

Claims

1. A method for scrambling a television signal in which a television signal is compressed in a horizontal blanking interval and in a vertical blanking interval, and a key signal containing information concerning the compression is superimposed on an audio signal during said horizontal blanking interval, said method comprising the steps of:

superimposing a pseudo-key signal, which is a pulse signal similar to said key signal, on said audio signal during said vertical blanking interval; and

making said key signal contain information concerning a position of said vertical blanking interval.

14. The method as claimed in claim 1 further comprising the steps of:

compressing said television signal such that compression rates of said horizontal and vertical blanking intervals are changed with time independently of each other; and

providing in said key signal information concerning both of said compression rates.

2. A method for descrambling a television signal scrambled by compressing said television signal in a horizontal blanking interval and in a vertical blanking interval, said television signal being transmitted with an audio signal on which a key signal containing information concerning said compression and information concerning a position of said vertical blanking interval is superimposed at a portion of said audio signal corresponding to said horizontal blanking interval and on which a pseudo-key signal is superimposed at a portion of said audio signal corresponding to said vertical blanking interval, said method comprising the steps of:

detecting said vertical blanking interval based on said information concerning said position of said vertical blanking interval contained in said key signal;

extracting said information concerning said compression and contained in said key signal, based on the thus detected vertical blanking interval;

generating an expansion signal for expanding said television signal in said horizontal blanking interval and said vertical blanking interval based on said extracted information concerning said compression; and

expanding said television signal in said horizontal blanking interval and said vertical blanking interval based on said expansion signal to thereby descramble said television signal.

3. An apparatus for descrambling a television signal scrambled by compressing said television signal in a horizontal blanking interval and in a vertical blanking interval, said television signal being transmitted with an audio signal on which a key signal containing information concerning said compression and information concerning a position of said vertical blanking interval is superimposed at a portion of said audio signal corresponding to said horizontal blanking interval and on which a pseudo-key signal is superimposed at a portion of said audio signal corresponding to said vertical blanking interval, said apparatus comprising:

vertical blanking interval detection means for detecting said vertical blanking interval based on said information concerning said position of said vertical blanking interval contained in said key signal;

information extracting means for extracting said information concerning said compression and contained in said key signal, based on said detected vertical blanking interval detected by said vertical blanking interval detection means;

expansion signal generation means for generating an expansion signal for expanding said television signal in said horizontal blanking interval and said vertical blanking interval based on said information concerning said compression extracted by said information extraction means; and

descrambling means for expanding said television signal in said horizontal blanking interval and said vertical blanking interval based on said expansion signal generated by said expansion signal generation means to thereby descramble said television signal.

4. A method for scrambling a television signal in which a television signal is compressed in a horizontal blanking interval and in a vertical blanking interval, and a key signal containing information concerning said compression is superimposed on an audio signal during said horizontal blanking interval, comprising the steps of:

superimposing a pseudo-key signal on said audio signal during said vertical blanking interval;

making said key signal contain information concerning a position of said vertical blanking interval; and

transmitting in the form of out-band data information to be used in decoding said information concerning said position.

5. A method for descrambling a television signal which is scrambled by compressing a television signal in a horizontal blanking interval and in a vertical blanking interval, based on a key signal superimposed on a portion of an audio signal corresponding to said horizontal blanking interval and containing information concerning said compression and information concerning a position of said vertical blanking interval in the form of in-band data, and based on information transmitted in the form of out-band data and used in decoding said information concerning said position of said vertical blanking interval, said audio signal containing a pseudo-key signal superimposed on a portion thereof corresponding to said vertical blanking interval, said method comprising the steps of:

decoding said information concerning said position of said vertical blanking interval and contained in said key signal, based on said information transmitted in the form of out-band data;

detecting said vertical blanking interval based on said decoded information;

extracting said information concerning said compression and contained in said key signal, based on said detected vertical blanking interval;

generating an expansion signal for expanding said television signal in said horizontal blanking interval and said vertical blanking interval based on said extracted information concerning said compression; and

expanding said television signal in said horizontal blanking interval and in said vertical blanking interval based on said expansion signal to thereby descramble said television signal.

6. An apparatus for descrambling a television signal which is scrambled by compressing a television signal in a horizontal blanking interval and in a vertical blanking interval, based on a key signal superimposed on a portion of an audio signal corresponding to said horizontal blanking interval and containing information concerning said compression and information concerning a position of said vertical blanking interval in the form of in-band data, and based on information transmitted in the form of out-band data and used in decoding said information concerning said position of said vertical blanking interval, said audio signal containing a pseudo-key signal superimposed on a portion thereof corresponding to said vertical blanking interval, said apparatus comprising:

decoding means for decoding said information concerning said position of said vertical blanking interval and contained in said key signal, based on said information transmitted in the form of out-band data;

vertical blanking interval detection means for detecting said vertical blanking interval based on said decoded information;

information extracting means for extracting said information concerning said compression and contained in said key signal, based on said vertical blanking interval detected by said vertical blanking interval detection means;

expansion signal generating means for generating an expansion signal for expanding said television signal in said horizontal blanking interval and said vertical blanking interval based on said information concerning said compression and extracted by said information extracting means; and

descrambling means for expanding said television signal in said horizontal blanking interval and said vertical blanking interval based on said expansion signal to thereby descramble said television signal.

7. A CATV center-side apparatus comprising:

video and audio source means for providing a video signal and an audio signal;

modulator means for covering said video signal and said audio signal into intermediate frequency (IF) signals, respectively;

encoding means for compressing said video IF signal from said modulator means in a horizontal blanking interval and in a vertical blanking interval at a predetermined compression rate and for superimposing key and pseudo-key signals on said audio IF signal, respectively, at portions corresponding to said horizontal blanking interval and said vertical blanking interval; and

up-converter means for converting said video and audio IF signals to a predetermined frequency for transmission.

8. A CATV center-side apparatus as claimed in claim 7, wherein said encoding means comprises:

synchronizing signal separating means, receiving an input video signal, for extracting a horizontal synchronizing signal and a vertical synchronizing signal from said video signal;

first and second pulse generating means, having as inputs said horizontal synchronizing signal and said vertical synchronizing signal, for generating pulses;

control means for controlling said first and second pulse generating means and for establishing said predetermined compression rate corresponding to a predetermined number of said vertical synchronizing signals counted by said control means; and

first and second switching means, responsive to said first and second pulse generating means, for compressing signals input thereto by predetermined amounts.

9. A CATV terminal apparatus for descrambling a transmitted signal comprising:

converter means, responsive to said transmitted signal, for selecting a specific channel and for frequency converting a signal in said specific channel to form an IF signal;

filter means connected to said converter means for filtering said IF signal into a high-band video IF signal and a low-band audio IF signal;

expansion circuit means connected to said filter means for descrambling said high-band video IF signal;

branching means connected to said filter means for branching said low-band audio IF signal into first and second parts;

key signal detecting means, having as an input said first part of said low-band audio IF signal, for extracting a key signal superimposed on said audio IF signal;

in-band data detecting means connected to an output of said key signal detecting means for detecting in-band data contained in said key signal and for generating expansion pulses for use by said expansion circuit means; and

mixing means for mixing said video IF signal descrambled by said expansion circuit means and said second part of said audio IF signal.

10. In a method for scrambling a television signal in which a television signal is compressed during a horizontal blanking interval and during a vertical blanking interval, and a key signal containing information concerning the compression is superimposed on an audio signal during said horizontal blanking interval, the improvement comprising:

providing in said key signal information concerning the position of said vertical blanking interval.

15. The method as claimed in claim 10 further comprising the steps of:

compressing said television signal such that compression rates of said horizontal and vertical blanking intervals are changed with time independently of each other; and

providing in said key signal information concerning both of said compression rates.

11. An apparatus for descrambling a television signal scrambled by compressing said television signal during a horizontal blanking interval and during a vertical blanking interval, said television signal being transmitted with an audio signal on which a key signal containing information concerning said compression and information concerning the position of said vertical blanking interval is superimposed at a portion of said audio signal corresponding to said horizontal blanking interval, said apparatus comprising:

vertical blanking interval detection means for detecting said vertical blanking interval based on said information concerning said position of said vertical blanking interval contained in said key signal;

information extracting means for extracting said information concerning said compression and contained in said key signal, based on said detected vertical blanking interval detected by said vertical blanking interval detection means;

expansion signal generation means for generating an expansion signal for expanding said television signal in said horizontal blanking interval and said vertical blanking interval based on said information concerning said compression extracted by said information extraction means; and

descrambling means for expanding said television signal in said horizontal blanking interval and said vertical blanking interval based on said expansion signal generated by said expansion signal generation means to thereby descramble said television signal.

12. A method for scrambling a television signal in which a television signal is compressed during a horizontal blanking interval and during a vertical blanking interval, and a key signal containing information concerning said compression is superimposed on an audio signal during said horizontal blanking interval, comprising the steps of:

providing in said key signal information concerning the position of said vertical blanking interval; and

transmitting in the form of out-band data information to be used in decoding said information concerning said position.

13. A CATV center-side apparatus comprising:

video and audio source means for providing a video signal and an audio signal;

modulator means for converting said video signal and said audio signal into intermediate frequency (IF) signals, respectively;

encoding means for compressing said video IF signal from said modulator means during a horizontal blanking interval and during a vertical blanking interval at a predetermined compression rate and for superimposing a key signal on said audio IF signal at a position corresponding to said horizontal blanking interval; and

up-converter means for converter said video and audio IF signals to a predetermined frequency for transmission.