Video scene change detection

• US 20030152224A1
• Filed: 10/18/2002
• Published: 08/14/2003
• Est. Priority Date: 01/02/2002
• Status: Active Grant

• Current Assignee: Sony Corporation (Sony Group Corp.), Sony Electronics Inc. (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.), Sony Electronics Inc. (Sony Group Corp.)
• Inventors: Candelore, Brant L., Pedlow, Leo M. Jr., Derovanessian, Henry
• Granted Patent: US 7,292,690 B2
• Time in Patent Office: Days
• US Class Current: 380/210
• CPC Class Codes: H04L 63/0428 wherein the data content is protected, e.g. by encrypting or encapsulating the payload
• CPC Class Codes: H04N 21/23476 by partially encrypting, e.g. encrypting the ending portion of a movie
• CPC Class Codes: H04N 21/23608 Remultiplexing multiplex streams, e.g. involving modifying time stamps or remapping the packet identifiers
• CPC Class Codes: H04N 21/2362 Generation or processing of Service Information [SI]
• CPC Class Codes: H04N 21/2365 Multiplexing of several video streams
• CPC Class Codes: H04N 21/23897 by partially encrypting, e.g. encrypting only the ending portion of a movie
• CPC Class Codes: H04N 21/25875 involving end-user authentication restricting access to computer systems by authenticating users using a predetermined code G06F21/33; arrangements for secret or secure communication including means for verifying the identity or authority of a user of the system H04L9/32; networks authentication protocols H04L63/08; authentication in wireless network security H04W12/06
• CPC Class Codes: H04N 21/26606 for generating or managing entitlement messages, e.g. Entitlement Control Message [ECM] or Entitlement Management Message [EMM] arrangements for conditional access to broadcast information or to broadcast-related services H04H60/14
• CPC Class Codes: H04N 21/4344 Remultiplexing of multiplex streams, e.g. by modifying time stamps or remapping the packet identifiers
• CPC Class Codes: H04N 21/4345 Extraction or processing of SI, e.g. extracting service information from an MPEG stream
• CPC Class Codes: H04N 21/4347 Demultiplexing of several video streams
• CPC Class Codes: H04N 21/43607 Interfacing a plurality of external cards, e.g. through a DVB Common Interface [DVB-CI]
• CPC Class Codes: H04N 21/44055 by partially decrypting, e.g. decrypting a video stream that has been partially encrypted
• CPC Class Codes: H04N 21/4408 involving video stream encryption, e.g. re-encrypting a decrypted video stream for redistribution in a home network
• CPC Class Codes: H04N 21/4516 involving client characteristics, e.g. Set-Top-Box type, software version or amount of memory available
• CPC Class Codes: H04N 21/454 Content or additional data filtering, e.g. blocking advertisements
• CPC Class Codes: H04N 21/4623 Processing of entitlement messages, e.g. ECM [Entitlement Control Message] or EMM [Entitlement Management Message] arrangements for conditional access to broadcast information or to broadcast-related services H04H60/14
• CPC Class Codes: H04N 21/631 Multimode Transmission, e.g. transmitting basic layers and enhancement layers of the content over different transmission paths or transmitting with different error corrections, different keys or with different transmission protocols
• CPC Class Codes: H04N 5/913 for scrambling ; for copy protection
• CPC Class Codes: H04N 7/162 Authorising the user terminal, e.g. by paying; Registering the use of a subscription channel, e.g. billing
• CPC Class Codes: H04N 7/167 : Systems rendering the television signal unintelligible and subsequently intelligible
• 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 9/8042 : involving data reduction

Abstract

A selective encryption encoder consistent with certain embodiments of the invention has vertical and/or horizontal stripes encrypted. In one embodiment, packets are examined in the digital video signal to identify a specified packet type, the specified packet type being packets carrying data representing a video slice wherein the video slice contains a larger amount of data than a threshold (or a subsequent slice). The packets identified as being of the specified packet type are encrypted using a first encryption method to produce first encrypted packets. These first encrypted packets are then used to replace the unencrypted packets in the digital video signal to produce a partially encrypted video signal. The packets of the specified type can also be multiple encrypted and replaced in the data stream to produce a multiple encrypted video data stream.

Claims

1. A method of detecting a scene change in a digital video signal, comprising:

examining a slice of the digital video signal;

determining if the slice contains a greater amount of data than a threshold amount of data; and

if the slice contains a greater amount of data than the threshold, determining that the slice forms a part of a scene change.

2. The method according to claim 1, further comprising encrypting intra-coded data at a start of the scene change.

3. The method according to claim 1, further comprising encrypting the slice of video data.

4. The method according to claim 1, further comprising encryption a slice header of the slice of video data.

5. The method according to claim 1, further comprising encrypting a subsequent slice of video data.

6. The method according to claim 1, further comprising encrypting a slice header for a subsequent slice of video data.

7. The method according to claim 1, wherein determining if the slice contains a greater amount of data than the threshold amount of data comprises counting a number of packets carrying the slice and determining if the number of packets is greater than a threshold number of packets.

8. The method according to claim 1, wherein determining if the slice contains a greater amount of data than the threshold amount of data comprises counting a number of intra-coded macroblocks in the slice and determining if the number of intra-coded macroblocks is greater than a threshold number of intra-coded macroblocks.

9. A computer readable medium storing instructions which, when executed on a programmed processor, carry out the method of scene change detection according to claim 1.

10. The computer readable medium of claim 9, wherein the medium comprises one of an electronic storage medium and a carrier wave.

11. A method of partially dual encrypting a digital video signal, comprising:

examining unencrypted packets of data in the digital video signal to identify a specified packet type, the specified packet type comprising packets carrying data representing a video slice wherein the video slice contains a larger amount of data than a threshold amount of data;

encrypting packets identified as being of the specified packet type using a first encryption method to produce first encrypted packets;

encrypting the packets identified as being of the specified packet type using a second encryption method to produce second encrypted packets; and

replacing the unencrypted packets of the specified packet type with the first encrypted packets and the second encrypted packets in the digital video signal to produce a partially dual encrypted video signal.

12. The method according to claim 11, wherein determining if the slice contains a greater amount of data than the threshold amount of data comprises counting a number of packets carrying the slice and determining if the number of packets is greater than a threshold number of packets.

13. The method according to claim 11, wherein determining if the slice contains a greater amount of data than the threshold amount of data comprises counting a number of intra-coded macroblocks in the slice and determining if the number of intra-coded macroblocks is greater than a threshold number of intra-coded macroblocks.

14. A computer readable medium storing instructions which, when executed on a programmed processor, carry out the method of encrypting a digital video signal according to claim 11.

15. The computer readable medium of claim 14, wherein the medium comprises one of an electronic storage medium and a carrier wave.

16. An electronic transmission medium carrying an encrypted digital video signal encrypted by the method according to claim 11.

17. A selective encryption encoder, comprising:

a packet identifier that identifies packets of a specified packet type, the specified packet type comprising packets carrying data representing a video slice wherein the video slice contains a larger amount of data than a threshold amount of data;

a packet duplicator that duplicates the identified packets to produce first and second sets of the identified packets;

means for sending and receiving packets to and from a primary encryption encoder to encrypt the first set of identified packets under a first encryption method; and

a secondary encrypter for encrypting the second set of identified packets under a second encryption method.

18. The selective encryption encoder according to claim 17, wherein the packet identifier determines if the slice contains a greater amount of data than the threshold amount of data comprises counting a number of packets carrying the slice and determining if the number of packets is greater than a threshold number of packets.

19. The selective encryption encoder according to claim 17, wherein the packet identifier determines if the slice contains a greater amount of data than the threshold amount of data comprises counting a number of intra-coded macroblocks in the slice and determining if the number of intra-coded macroblocks is greater than a threshold number of intra-coded macroblocks.

20. A method of partially encrypting a digital video signal, comprising:

examining unencrypted packets of data in the digital video signal to identify a specified packet type, the specified packet type comprising packets carrying data representing a video slice wherein the video slice contains a larger amount of data than a threshold amount of data;

encrypting packets identified as being of the specified packet type using a first encryption method to produce first encrypted packets; and

replacing the unencrypted packets of the specified packet type with the first encrypted packets in the digital video signal to produce a partially encrypted video signal.

21. The method according to claim 20, wherein determining if the slice contains a greater amount of data than the threshold amount of data comprises counting a number of packets carrying the slice and determining if the number of packets is greater than a threshold number of packets.

22. The method according to claim 21, wherein determining if the slice contains a greater amount of data than the threshold amount of data comprises counting a number of intra-coded macroblocks in the slice and determining if the number of intra-coded macroblocks is greater than a threshold number of intra-coded macroblocks.

23. A computer readable medium storing instructions which, when executed on a programmed processor, carry out the method of encrypting a digital video signal according to claim 20.

24. The computer readable medium of claim 23, wherein the medium comprises one of an electronic storage medium and a carrier wave.

25. An electronic transmission medium carrying an encrypted digital television signal encrypted by the method according to claim 20.

26. A method of partially dual encrypting a digital video signal, comprising:

examining unencrypted packets of data in the digital video signal to identify a specified packet type, the specified packet type comprising packets carrying data representing a video slice wherein a preceding video slice contains a larger amount of data than a threshold amount of data;

encrypting packets identified as being of the specified packet type using a first encryption method to produce first encrypted packets;

encrypting the packets identified as being of the specified packet type using a second encryption method to produce second encrypted packets; and

replacing the unencrypted packets of the specified packet type with the first encrypted packets and the second encrypted packets in the digital video signal to produce a partially dual encrypted video signal.

27. The method according to claim 26, wherein determining if a preceding slice contains a greater amount of data than the threshold amount of data comprises counting a number of packets carrying the slice and determining if the number of packets is greater than a threshold number of packets.

28. The method according to claim 26, wherein determining if a preceding slice contains a greater amount of data than the threshold amount of data comprises counting a number of intra-coded macroblocks in the slice and determining if the number of intra-coded macroblocks is greater than a threshold number of intra-coded macroblocks.

29. A computer readable medium storing instructions which, when executed on a programmed processor, carry out the method of encrypting a digital video signal according to claim 26.

30. The computer readable medium of claim 29, wherein the medium comprises one of an electronic storage medium and a carrier wave.

31. An electronic transmission medium carrying an encrypted digital television signal encrypted by the method according to claim 26.

32. A selective encryption encoder, comprising:

a packet identifier that identifies packets of a specified packet type, the specified packet type comprising packets carrying data representing a video slice wherein a preceding video slice contains a larger amount of data than a threshold amount of data;

a packet duplicator that duplicates the identified packets to produce first and second sets of the identified packets;

means for sending and receiving packets to and from a primary encryption encoder to encrypt the first set of identified packets under a first encryption method; and

a secondary encrypter for encrypting the second set of identified packets under a second encryption method.

33. The selective encryption encoder according to claim 32, wherein the packet identifier determines if the preceding slice contains a greater amount of data than the threshold amount of data comprises counting a number of packets carrying the slice and determining if the number of packets is greater than a threshold number of packets.

34. The selective encryption encoder according to claim 32, wherein the packet identifier determines if the preceding slice contains a greater amount of data than the threshold amount of data comprises counting a number of intra-coded macroblocks in the slice and determining if the number of intra-coded macroblocks is greater than a threshold number of intra-coded macroblocks.

35. A method of partially encrypting a digital video signal, comprising:

examining unencrypted packets of data in the digital video signal to identify a specified packet type, the specified packet type comprising packets carrying data representing a video slice wherein a preceding video slice contains a larger amount of data than a threshold amount of data;

encrypting packets identified as being of the specified packet type using a first encryption method to produce first encrypted packets; and

replacing the unencrypted packets of the specified packet type with the first encrypted packets in the digital video signal to produce a partially encrypted video signal.

36. The method according to claim 35, wherein determining if the preceding slice contains a greater amount of data than the threshold amount of data comprises counting a number of packets carrying the slice and determining if the number of packets is greater than a threshold number of packets.

37. The method according to claim 35, wherein determining if the preceding slice contains a greater amount of data than the threshold amount of data comprises counting a number of intra-coded macroblocks in the slice and determining if the number of intra-coded macroblocks is greater than a threshold number of intra-coded macroblocks.

38. A computer readable medium storing instructions which, when executed on a programmed processor, carry out the method of encrypting a digital video signal according to claim 35.

39. The computer readable medium of claim 38 wherein the medium comprises one of an electronic storage medium and a carrier wave.

40. An electronic transmission medium carrying an encrypted digital television signal encrypted by the method according to claim 35.

41. A method of partially dual encrypting a digital video signal, comprising:

examining unencrypted packets of data in the digital video signal to identify a specified packet type, the specified packet type comprising packets carrying data representing a video slice header for a video slice that contains a larger amount of data than a threshold amount of data;

encrypting packets identified as being of the specified packet type using a first encryption method to produce first encrypted packets;

encrypting the packets identified as being of the specified packet type using a second encryption method to produce second encrypted packets; and

replacing the unencrypted packets of the specified packet type with the first encrypted packets and the second encrypted packets in the digital video signal to produce a partially dual encrypted video signal.

42. The method according to claim 41, wherein determining if the slice contains a greater amount of data than the threshold amount of data comprises counting a number of packets carrying the slice and determining if the number of packets is greater than a threshold number of packets.

43. The method according to claim 41, wherein determining if the slice contains a greater amount of data than the threshold amount of data comprises counting a number of intra-coded macroblocks in the slice and determining if the number of intra-coded macroblocks is greater than a threshold number of intra-coded macroblocks.

44. A computer readable medium storing instructions which, when executed on a programmed processor, carry out the method of encrypting a digital video signal according to claim 41.

45. The computer readable medium of claim 44, wherein the medium comprises one of an electronic storage medium and a carrier wave.

46. An electronic transmission medium carrying an encrypted digital television signal encrypted by the method according to claim 41.

47. A selective encryption encoder, comprising:

a packet identifier that identifies packets of a specified packet type, the specified packet type comprising packets carrying data representing a video slice header for a video slice that contains a larger amount of data than a threshold amount of data;

a packet duplicator that duplicates the identified packets to produce first and second sets of the identified packets;

means for sending and receiving packets to and from a primary encryption encoder to encrypt the first set of identified packets under a first encryption method;

a secondary encrypter for encrypting the second set of identified packets under a second encryption method.

48. The selective encryption encoder according to claim 47, wherein the packet identifier determines if the slice contains a greater amount of data than the threshold amount of data comprises counting a number of packets carrying the slice and determining if the number of packets is greater than a threshold number of packets.

49. The selective encryption encoder according to claim 47, wherein the packet identifier determines if the slice contains a greater amount of data than the threshold amount of data comprises counting a number of intra-coded macroblocks in the slice and determining if the number of intra-coded macroblocks is greater than a threshold number of intra-coded macroblocks.

50. A method of partially encrypting a digital video signal, comprising:

examining unencrypted packets of data in the digital video signal to identify a specified packet type, the specified packet type comprising packets carrying data representing a video slice header for a video slice that contains a larger amount of data than a threshold amount of data;

encrypting packets identified as being of the specified packet type using a first encryption method to produce first encrypted packets; and

replacing the unencrypted packets of the specified packet type with the first encrypted packets in the digital video signal to produce a partially encrypted video signal.

51. The method according to claim 50, wherein determining if the slice contains a greater amount of data than the threshold amount of data comprises counting a number of packets carrying the slice and determining if the number of packets is greater than a threshold number of packets.

52. The method according to claim 50, wherein determining if the slice contains a greater amount of data than the threshold amount of data comprises counting a number of intra-coded macroblocks in the slice and determining if the number of intra-coded macroblocks is greater than a threshold number of intra-coded macroblocks.

53. A computer readable medium storing instructions which, when executed on a programmed processor, carry out the method of encrypting a digital video signal according to claim 50.

54. The computer readable medium of claim 53, wherein the medium comprises one of an electronic storage medium and a carrier wave.

55. An electronic transmission medium carrying an encrypted digital television signal encrypted by the method according to claim 50.

56. A method of partially dual encrypting a digital video signal, comprising:

examining unencrypted packets of data in the digital video signal to identify a specified packet type, the specified packet type comprising packets carrying data representing a video slice header for a slice following a preceding video slice that contains a larger amount of data than a threshold amount of data;

encrypting packets identified as being of the specified packet type using a first encryption method to produce first encrypted packets;

encrypting the packets identified as being of the specified packet type using a second encryption method to produce second encrypted packets; and

replacing the unencrypted packets of the specified packet type with the first encrypted packets and the second encrypted packets in the digital video signal to produce a partially dual encrypted video signal.

57. The method according to claim 56, wherein determining if a preceding slice contains a greater amount of data than the threshold amount of data comprises counting a number of packets carrying the slice and determining if the number of packets is greater than a threshold number of packets.

58. The method according to claim 56, wherein determining if a preceding slice contains a greater amount of data than the threshold amount of data comprises counting a number of intra-coded macroblocks in the slice and determining if the number of intra-coded macroblocks is greater than a threshold number of intra-coded macroblocks.

59. A computer readable medium storing instructions which, when executed on a programmed processor, carry out the method of encrypting a digital video signal according to claim 56.

60. The computer readable medium of claim 59, wherein the medium comprises one of an electronic storage medium and a carrier wave.

61. An electronic transmission medium carrying an encrypted digital television signal encrypted by the method according to claim 56.

62. A selective encryption encoder, comprising:

a packet identifier that identifies packets of a specified packet type, the specified packet type comprising packets carrying data representing a video slice header for a slice following a preceding video slice that contains a larger amount of data than a threshold amount of data;

a packet duplicator that duplicates the identified packets to produce first and second sets of the identified packets;

means for sending and receiving packets to and from a primary encryption encoder to encrypt the first set of identified packets under a first encryption method;

a secondary encrypter for encrypting the second set of identified packets under a second encryption method.

63. The selective encryption encoder according to claim 62, wherein the packet identifier determines if the preceding slice contains a greater amount of data than the threshold amount of data comprises counting a number of packets carrying the slice and determining if the number of packets is greater than a threshold number of packets.

64. The selective encryption encoder according to claim 62, wherein the packet identifier determines if the preceding slice contains a greater amount of data than the threshold amount of data comprises counting a number of intra-coded macroblocks in the slice and determining if the number of intra-coded macroblocks is greater than a threshold number of intra-coded macroblocks.

65. A method of partially encrypting a digital video signal, comprising:

examining unencrypted packets of data in the digital video signal to identify a specified packet type, the specified packet type comprising packets carrying data representing a video slice header for a slice following a preceding video slice that contains a larger amount of data than a threshold amount of data;

encrypting packets identified as being of the specified packet type using a first encryption method to produce first encrypted packets; and

replacing the unencrypted packets of the specified packet type with the first encrypted packets in the digital video signal to produce a partially encrypted video signal.

66. The method according to claim 65, wherein determining if the preceding slice contains a greater amount of data than the threshold amount of data comprises counting a number of packets carrying the slice and determining if the number of packets is greater than a threshold number of packets.

67. The method according to claim 65, wherein determining if the preceding slice contains a greater amount of data than the threshold amount of data comprises counting a number of intra-coded macroblocks in the slice and determining if the number of intra-coded macroblocks is greater than a threshold number of intra-coded macroblocks.

68. A computer readable medium storing instructions which, when executed on a programmed processor, carry out the method of encrypting a digital video signal according to claim 65.

69. The computer readable medium of claim 68, wherein the medium comprises one of an electronic storage medium and a carrier wave.

70. An electronic transmission medium carrying an encrypted digital television signal encrypted by the method according to claim 65.

71. A method of selective encryption of a digital video signal, comprising:

detecting a scene change in the digital video signal; and

encrypting at least a portion of the digital video signal carrying data representing a first image associated with the scene change.

72. The method according to claim 71, wherein the detecting comprises determining if a video slice contains a greater amount of data than a threshold amount of data, and if the video slice contains a greater amount of data than the threshold, determining that the video slice forms a part of a scene change.

73. The method according to claim 71, wherein the encrypting comprises encrypting the video slice.

74. The method according to claim 71, wherein the encrypting comprises encrypting a slice header of the video slice.

75. The method according to claim 71, wherein the encrypting comprises encrypting a subsequent video slice.

76. The method according to claim 71, wherein the encrypting comprises encrypting packets forming a part of the first image using a first encryption method to produce first encrypted packets.

77. The method according to claim 76, further comprising encrypting a duplicate of the packets forming a part of the first image using a second encryption method to produce second encrypted packets.

78. The method according to claim 77, further comprising replacing unencrypted packets with the first encrypted packets and the second encrypted packets in the digital video signal to produce a partially dual encrypted video signal.

79. The method according to claim 71, wherein the encrypting comprises encrypting intra-coded data in a first image associated with the scene change.

80. The method according to claim 71, wherein the encrypting comprises encrypting a video slice header in a first image associated with the scene change.

81. The method according to claim 71, wherein the detecting comprises counting a number of packets carrying a video slice and determining if the number of packets is greater than a threshold number of packets.

82. The method according to claim 71, wherein the detecting comprises counting a number of intra-coded macroblocks in a video slice and determining if the number of intra-coded macroblocks is greater than a threshold number of intra-coded macroblocks.

83. The method according to claim 71, wherein the detecting comprises determining if an image contains a greater amount of data than a threshold amount of data, and if the image contains a greater amount of data than the threshold, determining that the image forms a part of a scene change.

84. The method according to claim 83, wherein the image comprises a frame of video.

85. A computer readable medium storing instructions which, when executed on a programmed processor, carry out the method of encrypting a digital video signal according to claim 71.

86. The computer readable medium of claim 85, wherein the medium comprises one of an electronic storage medium and a carrier wave.

87. An electronic transmission medium carrying an encrypted digital television signal encrypted by the method according to claim 71.

88. A television set-top box, comprising:

a receiver receiving a digital television signal comprising;

a plurality of unencrypted packets; and

a plurality of encrypted packets, wherein certain of the encrypted packets carry data representing a first image associated with the scene change;

a decrypter that decrypts the encrypted packets; and

a decoder that decodes the unencrypted packets and the decrypted packets to produce a signal suitable for play on a television set.

89. A selective encryption decoder, for decrypting and decoding a selectively encrypted digital video signal, comprising:

a demultiplexer that receives packets of digital video, certain of the packets being unencrypted and certain of the packets being encrypted, wherein certain of the encrypted packets carry data representing a first image associated with the scene change;

the unencrypted packets having a first packet identifier (PID) and the encrypted packets having a second packet identifier (PID);

a decrypter receiving the encrypted packets having the second PID and decrypting the encrypted packets using a first encryption method to produce decrypted packets;

a PID remapper that changes at least one of the first and second PIDs so that the unencrypted packets and the decrypted packets have the same PID; and

a decoder that decodes the unencrypted and decrypted packets to produce a decoded video signal.

90. A method of decrypting and decoding a selectively encrypted digital video signal, comprising:

receiving packets of digital video, certain of the packets being unencrypted and certain of the packets being encrypted, wherein certain of the encrypted packets carry data representing a first image associated with the scene change;

the unencrypted packets having a first packet identifier (PID) and the encrypted packets having a second packet identifier (PID);

decrypting the encrypted packets having the second PID to produce decrypted packets;

remapping at least one of the first and second PIDs so that the unencrypted packets and the decrypted packets have the same PID; and

decoding the unencrypted and decrypted packets to produce a decoded video signal.

91. A computer readable medium carrying instructions which, when executed on a programmed processor, carry out the method of decrypting and decoding a digital television signal according to claim 90.

92. The computer readable medium of claim 91, wherein the medium comprises one of an electronic storage medium and a carrier wave.

93. A computer readable medium that carries instructions that when executes on a programmed processor to facilitate operation of a video receiver device to decrypt and decode a selectively encoded digital video signal wherein the instructions comprise:

a code segment that controls a demultiplexer that receives packets of digital video, certain of the packets being unencrypted and certain of the packets being encrypted, wherein certain of the encrypted packets carry data representing a first image associated with the scene change, the unencrypted packets having a first packet identifier (PID) and the encrypted packets having a second packet identifier (PID);

a code segment that controls decryption of the encrypted packets to produce decrypted packets;

a code segment that controls remapping at least one of the first and second PIDs so that the unencrypted packets and the decrypted packets have the same PID; and

a code segment that controls decoding the unencrypted and decrypted packets to produce a decoded video signal.

94. The computer readable medium of claim 93, wherein the medium comprises one of an electronic storage medium and a carrier wave.

95. A selectively encrypted digital video signal embodied in a carrier wave, comprising:

a stream of packets of video data, wherein the stream of packets when not encrypted represent a segment of video content;

certain of the packets being unencrypted and certain of the packets being encrypted, wherein certain of the encrypted packets carry data representing a first image associated with the scene change;

a first segment of code that identifies the unencrypted packets by a first packet identifier (PID); and

a second segment of code that identifies the encrypted packets by a second packet identifier (PID).

96. A selectively encrypted digital video signal embodied in a computer readable medium, comprising:

a sequence of packets of video data, wherein the sequence of packets when not encrypted represent a segment of video content;

wherein certain of the packets are unencrypted;

wherein certain of the packets have been produced by decrypting encrypted packets;

wherein certain of the encrypted packets carry data representing a first image associated with the scene change; and

a segment of code that identifies the unencrypted packets by a first packet identifier (PID); and

a segment of code that identifies the encrypted packets by a second packet identifier (PID).