Copy prevention method and apparatus for digital video system

• US 5,761,302 A
• Filed: 11/22/1995
• Issued: 06/02/1998
• Est. Priority Date: 11/26/1994
• Status: Expired due to Term

• Current Assignee: LG Electronics, Inc. (LG Corporation)
• Original Assignee: LG Electronics, Inc. (LG Corporation)
• Inventors: Park, Tae Joon
• Primary Examiner(s): CANGIALOSI, SALVATORE A
• Application Number:
  US08/562,042
• Time in Patent Office: 923 Days
• Field of Search: 380/5, 380/20
• US Class Current: 380/201
• CPC Class Codes: H04N 2005/91328 the copy protection signal being a copy management signal, e.g. a copy generation management signal [CGMS]
• CPC Class Codes: H04N 2005/91364 the video signal being scrambled
• CPC Class Codes: H04N 5/913 for scrambling ; for copy protection
• CPC Class Codes: H04N 9/8042 involving data reduction
• CPC Class Codes: H04N 9/8063 using time division multiplex of the PCM audio and PCM video signals
• CPC Class Codes: H04N 9/8205 involving the multiplexing of an additional signal and the colour video signal

Abstract

A copy prevention method and apparatus for a digital video system is disclosed including the steps of: (a) adding a header area of a header start code and key field to a reproduced bit stream; (b) decrypting and transmitting the bit stream to which the header area is added; (c) detecting a key field of the decrypted and transmitted bit stream and detecting copy prevention information; and (d) encrypting the bit stream according to information detected form step (c) and recording it on tape.

Claims

1. A copy prevention method for a digital video system comprising the steps of:

(a) adding a header area of a header start code and key field to a reproduced bit stream;

(b) decrypting and transmitting the bit stream to which the header area is added;

(c) detecting a key field of the decrypted and transmitted bit stream and detecting copy prevention information; and

(d) encrypting the bit stream according to information detected from step (c) and recording it on tape.

2. A copy prevention method for a digital video system as claimed in claim 1, wherein, in step (a), a tape header start code in added to the front of the bit stream and then a key field thereto.

3. A copy prevention method for a digital video system as claimed in claim 1, wherein, in step (c), a key field is detected and corrected if necessary.

4. A copy prevention method for a digital video system as claimed in claim 1, wherein, in step (c), copy prevention information is recorded in an additional copy information field of a DES header.

5. A copy prevention method for a digital video system as claimed in claim 4, wherein, in step (c), the variable position of said additional copy information field is compensated.

6. A copy prevention method for a digital video system as claimed in claim 1, wherein, in step (d), the bit stream is encrypted in units of block.

7. A copy prevention method for a digital video system as claimed in claim 1, wherein, in step (d), the bit stream is encrypted after an additional copy information field.

8. A copy prevention method for a digital video system as claimed in claim 6, wherein, in step (d), the bit stream is encrypted after the additional copy information field.

9. A copy prevention apparatus or a digital video system comprising:

a reproduction block for adding key information to a reproducing bit stream, and decrypting and transmitting it; and

a recording block for searching key information of the bit stream transmitted from said reproducing block to extract copy prevention information, and encrypting and recording the bit stream according to the extracted copy prevention information.

10. A copy prevention apparatus for a digital video system claimed in claim 9, wherein said reproducing block comprises:

reproducing means for reproducing data recorded on tape;

key insertion means or adding key information to the bit stream of said reproducing means; and

decrypting means for decrypting the output of said key insertion means and transmitting it to a recording-side VCR.

11. A copy prevention apparatus for a digital video system as claimed in claim 9, wherein said recording block comprises:

key detecting/correcting means for detracting key information from the transmitted bit stream of a reproducing-side VCR;

copy prevention information detecting means for searching the key information detected form said key detecting/correcting means for detect copy prevention information;

encrypting means for encrypting the bit stream according the copy prevention information of said copy prevention information detecting means;

recording means for recording the bit stream encrypted in said encrypting means.

12. A copy prevention apparatus for a digital video system as claimed in claim 11, wherein said copy prevention information detecting means comprises:

a PES header detecting portion for detecting a PES header from parallel data output from said key detecting/correcting means; and

a copy prevention information extractor enabled by a PES header detecting signal of said PES header detecting portion to detect an additional copy information field.

13. A copy prevention apparatus for a digital video system as claimed in claim 12, wherein said PES header detecting portion comprises:

first delay for delaying said parallel data output from said key detecting/correcting means in synchronization with a clock;

a packet start code detector for searching the input/output data of said first delay to detect a packet start code;

a second delay for delaying the output of said packet start code detector for a predetermined time;

a stream ID detector for searching the output of said second delay to detect a stream ID;

a detection signal dgenerator for logically combining the outputs of said stream ID detector and said second delay and outputting a PES header detection signal.

14. A copy preventing apparatus for a digital video system as claimed in claim 13, wherein said first and second delays are constructed to connect D-flipflops at multi-stages serially.

15. A copy prevention apparatus for a digital video system as claimed in claim 13, wherein said detection signal generator comprises:

an AND gate for logically multiplying the packet start code detecting signal of said packet start code detector and the stream ID code detecting signal of said stream ID code detector; and

a flipflop for holding the output of said AND gate in synchronization with a clock.

16. A copy prevention apparatus for a digital video system as claimed in claim 12, wherein said copy prevention information extractor comprises:

a first flipflop for holding the parallel data output from said PES header detector;

a second flipflop enabled by a CR flag of the output of said first flipflop for holding a voltage;

a third flipflop enabled by a OC flag of the output of said first flipflop for holding a voltage;

a copy prevention information position operator for searching the parallel data output from said PES header detector and calculating the position of an additional copy information field;

a counter for counting the output of said copy information position operator;

a fourth flipflop synchronized with the output of said counter for holding the additional copy information field of the output of said first flipflop; and

a fifth flipflop synchronized with a header detecting signal of said PES header detector for enabling said second, third and fourth flipflops.