Multi-media copy management system

• US 5,963,909 A
• Filed: 11/25/1997
• Issued: 10/05/1999
• Est. Priority Date: 12/06/1995
• Status: Expired due to Term

• Current Assignee: Verance Corporation
• Original Assignee: Solana Technology Development Corp. (Verance Corporation)
• Inventors: Lee, Chong U., Moallemi, Kamran, Warren, Robert L.
• Primary Examiner(s): Trammell, James P.
• Assistant Examiner(s): Nguyen, Cuong H.
• Application Number:
  US08/977,719
• Time in Patent Office: 679 Days
• Field of Search: 705/1, 705/14, 380/3, 380/4, 380/49, 380/5, 386/94, 455/26.1, 360/60, 340/825.31, 395/186
• US Class Current: 705/52
• CPC Class Codes: G11B 20/00086 Circuits for prevention of unauthorised reproduction or copying, e.g. piracy indicating unauthorised use of record carriers in general G11B23/28; scrambling for television signal recording H04N5/913; network architectures or network protocols for network security H04L63/00; cryptographic mechanisms or cryptographic arrangements for secret or secure communication H04L9/00
• CPC Class Codes: G11B 20/0021 involving encryption or decryption of contents recorded on or reproduced from a record carrier
• CPC Class Codes: G11B 20/00253 wherein the key is stored on the record carrier
• CPC Class Codes: G11B 20/00333 the key being stored in header data, e.g. in sector headers
• CPC Class Codes: G11B 20/00507 wherein consecutive physical data units of the record carrier are encrypted with separate encryption keys, e.g. the key changes on a cluster or sector basis
• CPC Class Codes: G11B 20/00753 wherein the usage restriction limits the number of copies that can be made, e.g. CGMS, SCMS, or CCI flags
• CPC Class Codes: G11B 20/00768 wherein copy control information is used, e.g. for indicating whether a content may be copied freely, no more, once, or never, by setting CGMS, SCMS, or CCI flags
• CPC Class Codes: G11B 20/00818 wherein the usage restriction limits the signal quality, e.g. by low-pass filtering of audio signals or by reducing the resolution of video signals
• CPC Class Codes: G11B 20/00913 based on a spread spectrum technique
• CPC Class Codes: G11B 20/10 Digital recording or reproducing
• CPC Class Codes: G11B 2220/2545 CDs
• CPC Class Codes: G11B 2220/2562 DVDs [digital versatile discs]; Digital video discs; MMCDs; HDCDs
• CPC Class Codes: G11B 27/034 on discs G11B27/036, G11B27/038 take precedence
• CPC Class Codes: H04B 1/665 using psychoacoustic properties of the ear, e.g. masking effect
• CPC Class Codes: H04H 20/31 using in-band signals, e.g. subsonic or cue signal
• 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 2005/91342 the copy protection signal being an authentication signal
• CPC Class Codes: H04N 2005/9135 by superimposing the spectrally spread copy protection signal onto the video signal
• 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 7/17336 : Handling of requests in head-ends
• CPC Class Codes: H04N 9/8042 : involving data reduction
• CPC Class Codes: H04N 9/8227 : the additional signal being at least another television signal

Abstract

Reproduction of a multi-media data signal which is stored on a source media or distributed via a communication network is controlled by inserting master tag data and control tag data into the data signal. A player/recorder inserts an additional generation of control tag information each time a copy of the media is made. If the number of generations of the control tag information is above a threshold value, reproduction of the data signal may be inhibited. For example, if the data signal comprises video data, the player/recorder may only allow playing of the video signal on a display but will not allow recording. The playing and recording of associated signals, such as an audio signal which accompanies a video signal, may also be controlled. The master tag data and control tag data may be provided as spread spectrum signals which are spectrally shaped and power-adjusted according to the data signal to render them imperceptible in the data signal. With encrypted frames of multi-media data, encryption keys may be carried in a key layer with the encrypted data signal or another data signal for use in decryption on a frame by frame basis.

Claims

1. Apparatus for controlling the reproduction of a multi-media data signal using master tag information embedded therein, and which is adapted to carry control tag information embedded therein, comprising:

a receiver for receiving and detecting said master tag information embedded in said multi-media data signal, detecting said control tag information, if any, embedded in said multi-media data signal, and determining the number of generations of said control tag information;

an encoder for providing an additional generation of control tag information in said multi-media data signal; and

a data output stage responsive to the number of said generations of control tag information for selectively reproducing said multi-media data signal.

2. The apparatus of claim 1, wherein:

said encoder is responsive to said master tag information for providing said additional generation of control tag information; and

in the absence of master tag information in said multi-media data signal, said additional generation of control tag information is not provided.

3. The apparatus of claim 1, wherein said encoder further comprises at least one of:

(a) means for spectrally shaping said control tag information according to said multi-media data signal; and

(b) means for adjusting the power of said control tag information according to said multi-media data signal.

4. The apparatus of claim 1, further comprising:

a master source encoder comprising at least one of;

(a) means for spectrally shaping said master tag information according to said multi-media data signal; and

(b) means for adjusting the power of said master tag information according to said multi-media data signal.

5. The apparatus of claim 4, wherein:

at least one of said spectral shaping and power adjusting means render the master tag information at a desired level in said multi-media data signal.

6. The apparatus of claim 1, wherein:

said data output stage is prevented from reproducing said multi-media data signal when a predetermined number of generations of said control tag information is detected in the multi-media data signal;

said predetermined number being at least one.

7. The apparatus of claim 1, wherein:

said multi-media data signal includes cryptographic data embedded therein to enable the decryption of data packets carried together with said multi-media data signal.

8. The apparatus of claim 1, wherein:

said data signal comprises a plurality of data channels, and said encoder provides said control tag information and said master tag information in different ones of said data channels.

9. The apparatus of claim 1, wherein said multi-media data signal comprises:

at least one frame of multi-media data which is encrypted under an encryption key; and

an encryption key layer with at least one packet containing said encryption key for decrypting said at least one frame of multi-media data frame.

10. The apparatus of claim 1, wherein:

said encoder provides said control tag information as a spread spectrum signal.

11. The apparatus of claim 1, further comprising:

a master source encoder that provides said master tag information in said multi-media data signal as a spread spectrum signal.

12. The apparatus of claim 1, wherein:

said multi-media data signal comprises compressed digital data; and

said encoder provides said additional generation of control tag information without decompressing said compressed digital data.

13. The apparatus of claim 1, wherein:

said master tag information is provided as a spread spectrum signal in accordance with an associated pseudo-random sequence in at least one time segment of said multi-media data signal;

said encoder generates said control tag information as a spread spectrum signal using said associated pseudo-random sequence; and

said encoder provides said control tag information in said multi-media data signal in a time segment which is unaligned relative to said at least one time segment in which said master tag information is carried.

14. The apparatus of claim 1, wherein:

at least one of said master tag information and said control tag information, if any, is provided as a spread spectrum signal in said multi-media data signal; and

said encoder provides said additional generation of control tag information as a spread spectrum signal which is distinguishable from said at least one of said master tag information and said control tag information.

15. The apparatus of claim 1, wherein:

at least one of said master tag information and said control tag information, if any, is provided as a spread spectrum signal in said multi-media data signal in accordance with a first pseudo-random sequence; and

said encoder provides said additional generation of control tag information as a spread spectrum signal in accordance with a second pseudo-random sequence which is distinct from said first pseudo-random sequence.

16. The apparatus of claim 1, wherein:

said encoder provides said control tag information in a plurality of non-adjacent time segments of said multi-media data signal.

17. The apparatus of claim 1, further comprising:

a master source encoder that provides said master tag information in a plurality of non-adjacent time segments of said multi-media data signal.

18. The apparatus of claim 1, wherein said encoder provides said additional generation of control tag information at a level calculated to cumulatively degrade the quality of said multi-media data signal according to said number of generations of control tag information.

19. The apparatus of claim 1, wherein:

auxiliary data is embedded in said multi-media data signal; and

said data output stage is responsive to the number of said generations of control tag information for selectively reproducing said auxiliary data.

20. The apparatus of claim 1, wherein:

a presence of at least one of said master tag information and said control tag information in defined intervals of said multi-media data signal is used to carry information in said multi-media data signal according to a binary signaling scheme.

21. The apparatus of claim 1, wherein:

said multi-media data signal comprises video data.

22. The apparatus of claim 1, wherein:

said number of generations of detected control tag information in said received data signal is at least one.

23. The apparatus of claim 1, wherein:

said encoder provides said additional generation of control tag information in said multi-media data signal such that said additional generation of control tag information replaces said master tag information.

24. The apparatus of claim 1, wherein:

said encoder is operatively associated with said receiver for degrading the quality of said received data signal such that succeeding received and encoded generations of said data signal have an increasingly degraded quality.

25. A method for controlling the reproduction of a multi-media data signal that carries master tag information embedded therein, and which is adapted to carry control tag information embedded therein, comprising the steps of:

(a) retrieving said master tag information embedded in said multi-media data signal;

(b) retrieving said control tag information, if any, embedded in said multi-media data signal;

(c) determining the number of generations of said control tag information in said multi-media data signal;

(d) determining whether the number of said generations of control tag information is below a threshold level; and

;

(i) if so, providing an additional generation of control tag information in said multi-media data signal; and

,

(ii) if not, inhibiting the reproduction of said multi-media data signal.

26. The method of claim 25, comprising the further step of:

determining said threshold level according to said master tag information.

27. The method of claim 25, comprising at least one of the further steps of:

(a) spectrally shaping said additional generation of control tag information according to said multi-media data signal; and

(b) adjusting the power of said additional generation of control tag information according to said multi-media data signal.

28. The method of claim 25, comprising at least one of the further steps of:

(a) spectrally shaping said master tag information according to said multi-media data signal; and

(b) adjusting the power of said master tag information according to said multi-media data signal.

29. The method of claim 25, wherein:

at least one of said spectral shaping and power adjusting steps render said master tag information at a desired level in said multi-media data signal.

30. The method of claim 25, wherein:

said inhibiting step prevents reproduction of said multi-media data signal.

31. The method of claim 25, comprising the further step of:

providing cryptographic data embedded in said multi-media data signal to enable the decryption of data packets carried together with said multi-media data signal.

32. The method of claim 25, wherein said data signal comprises a plurality of data channels, comprising the further step of:

providing said control tag information and said master tag information in different ones of said data channels.

33. The method of claim 25, wherein said multi-media data signal comprises:

at least one frame of multi-media data which is encrypted under an encryption key; and

an encryption key layer with at least one packet containing said encryption key for decrypting said at least one frame of multi-media data frame.

34. The method of claim 25, wherein:

said additional generation of control tag information is provided as a spread spectrum signal.

35. The method of claim 25, wherein:

said master tag information is provided as a spread spectrum signal.

36. The method of claim 25, wherein:

said multi-media data signal comprises compressed digital data; and

said additional generation of control tag information is provided without decompressing said compressed digital data.

37. The method of claim 25, comprising the further steps of:

providing said master tag information as a spread spectrum signal in accordance with an associated pseudo-random sequence in at least one time segment of said data signal;

providing said additional generation of control tag information as a spread spectrum signal using said associated pseudo-random sequence; and

providing said additional generation of control tag information in said multi-media data signal in a time segment which is unaligned relative to said at least one time segment in which said master tag information is carried.

38. The method of claim 25, wherein at least one of said master tag information and said control tag information, if any, is provided as a spread spectrum signal in said multi-media data signal, comprising the further step of:

providing said additional generation of control tag information as a spread spectrum signal which is distinguishable from said at least one of said master tag information and said control tag information.

39. The method of claim 25, wherein at least one of said master tag information and said control tag information, if any, is provided as a spread spectrum signal in said multi-media data signal in accordance with a first pseudo-random sequence, comprising the further steps of:

providing additional generations of control tag information as distinct spread spectrum signals by using different pseudo-random sequences; and

providing said additional generation of control tag information as a spread spectrum signal in accordance with a second pseudo-random sequence which is distinct from said first pseudo-random sequence.

40. The method of claim 25, comprising the further step of:

providing additional generations of control tag information in a plurality of non-adjacent time segments of said multi-media data signal.

41. The method of claim 25, comprising the further step of:

providing said master tag information in a plurality of non-adjacent time segments of said multi-media data signal.

42. The method of claim 25, wherein:

said step (d)(i) provides said additional generation of control tag information at a level calculated to cumulatively degrade the quality of said multi-media data signal according to said number of generations of control tag information.

43. The method of claim 25, wherein auxiliary data is embedded in said multi-media data signal, and the number of said generations of control tag information is not below said threshold level, comprising the further step of:

inhibiting the reproduction of said auxiliary data.

44. The method of claim 25, comprising the further step of:

providing at least one of said master tag information and said control tag information in defined intervals of said multi-media data signal to carry information in said data signal according to a binary signaling scheme.

45. The method of claim 25, wherein:

said multi-media data signal comprises video data.

46. The method of claim 25, wherein:

said number of generations of detected control tag information is at least one.

47. The method of claim 25, wherein:

said step (d)(i) provides said additional generation of control tag information in said multi-media data signal such that said additional generation of control tag information replaces said master tag information.

48. The method of claim 25, comprising the further step of:

degrading the quality of said multi-media signal such that succeeding encoded generations of said multi-media data signal have an increasingly degraded quality.

49. Apparatus for controlling the reproduction of a primary multi-media data signal using an auxiliary multi-media data signal, where master tag information is embedded in at least one of said primary and auxiliary multi-media data signals, and at least one of said primary and auxiliary multi-media data signals is adapted to carry control tag information embedded therein, comprising:

a receiver for receiving and detecting said master tag information embedded in said at least one of said primary and auxiliary multi-media data signals, detecting said control tag information, if any, embedded in said at least one of said primary and auxiliary multi-media data signals, and determining the number of generations of said control tag information;

an encoder for providing an additional generation of control tag information in said at least one of said primary and auxiliary multi-media data signals; and

a data output stage responsive to the number of said generations of control tag information for selectively reproducing said primary multi-media data signal.

50. The apparatus of claim 49, wherein:

said data output stage is responsive to the number of said generations of control tag information for selectively reproducing said auxiliary multi-media data signal.

51. The apparatus of claim 49, wherein:

the master tag information is embedded in said auxiliary multi-media data signal, and said auxiliary multi-media data signal is adapted to carry the control tag information embedded therein.

52. The apparatus of claim 49, wherein:

the master tag information is embedded in said primary multi-media data signal, and said auxiliary multi-media data signal is adapted to carry the control tag information embedded therein.

53. The apparatus of claim 49, wherein:

said encoder provides said additional generation of control tag information in said primary multi-media data signal.

54. The apparatus of claim 53, wherein:

said encoder provides said additional generation of control tag information at a level calculated to cumulatively degrade the quality of said primary multi-media data signal according to said number of generations of control tag information.

55. The apparatus of claim 49, wherein:

said primary and auxiliary multi-media data signals are carried on a common source media.

56. The apparatus of claim 49, wherein:

said encoder is responsive to said master tag information for providing said additional generation of control tag information; and

in the absence of master tag information, said additional generation of control tag information is not provided.

57. The apparatus of claim 49, wherein said encoder further comprises at least one of:

(a) means for spectrally shaping said control tag information according to said at least one of said primary and auxiliary multi-media data signals; and

(b) means for adjusting the power of said control tag information according to said at least one of said primary and auxiliary multi-media data signals.

58. The apparatus of claim 49, further comprising:

a master source encoder comprising at least one of;

(a) means for spectrally shaping said master tag information according to said at least one of said primary and auxiliary multi-media data signals; and

(b) means for adjusting the power of said master tag information according to said at least one of said primary and auxiliary multi-media data signals.

59. The apparatus of claim 49, wherein:

at least one of said spectral shaping and power adjusting means render the master tag information at a desired level.

60. The apparatus of claim 49, wherein:

said data output stage is prevented from reproducing said primary multi-media data signal when a predetermined number of generations of said control tag information is detected in said at least one of said primary and auxiliary multi-media data signals;

said predetermined number being at least one.

61. The apparatus of claim 49, wherein:

said at least one of said primary and auxiliary multi-media data signals includes cryptographic data embedded therein to enable the decryption of data packets carried together with said at least one of said primary and auxiliary multi-media data signals.

62. The apparatus of claim 49, wherein:

said primary multi-media data signal comprises at least one frame of multi-media data which is encrypted under an encryption key; and

said auxiliary multi-media data signal comprises an encryption key layer with at least one packet containing said encryption key for decrypting said at least one frame of the primary multi-media data signal.

63. The apparatus of claim 49, wherein:

said encoder provides said control tag information as a spread spectrum signal.

64. The apparatus of claim 49, further comprising:

a master source encoder that provides said master tag information as a spread spectrum signal.

65. The apparatus of claim 49, wherein:

said at least one of said primary and auxiliary multi-media data signals comprises compressed digital data; and

said encoder provides said additional generation of control tag information without decompressing said compressed digital data.

66. The apparatus of claim 49, wherein:

said master tag information is provided as a spread spectrum signal in accordance with an associated pseudo-random sequence in at least one time segment of said at least one of said primary and auxiliary multi-media data signals;

said encoder generates said control tag information as a spread spectrum signal using said associated pseudo-random sequence; and

said encoder provides said control tag information in a time segment which is unaligned relative to said at least one time segment in which said master tag information is carried.

67. The apparatus of claim 49, wherein:

at least one of said master tag information and said control tag information, if any, is provided as a spread spectrum signal; and

said encoder provides said additional generation of control tag information as a spread spectrum signal which is distinguishable from said at least one of said master tag information and said control tag information.

68. The apparatus of claim 49, wherein:

at least one of said master tag information and said control tag information, if any, is provided as a spread spectrum signal in accordance with a first pseudo-random sequence; and

said encoder provides said additional generation of control tag information as a spread spectrum signal in accordance with a second pseudo-random sequence which is distinct from said first pseudo-random sequence.

69. The apparatus of claim 49, wherein:

said encoder provides said control tag information in a plurality of non-adjacent time segments.

70. The apparatus of claim 49, further comprising:

a master source encoder that provides said master tag information in a plurality of non-adjacent time segments of said at least one of said primary and auxiliary multi-media data signals.

71. The apparatus of claim 49, wherein:

said encoder provides said additional generation of control tag information in said auxiliary multi-media data signal.

72. The apparatus of claim 49, wherein:

a presence of at least one of said master tag information and said control tag information in defined intervals of said at least one of said primary and auxiliary multi-media data signals is used to carry information in said at least one of said primary and auxiliary multi-media data signals according to a binary signaling scheme.

73. The apparatus of claim 49, wherein:

said at least one of said primary and auxiliary multi-media data signals comprises video data.

74. The apparatus of claim 49, wherein:

said number of generations of detected control tag information is at least one.

75. The apparatus of claim 49, wherein:

said encoder provides said additional generation of control tag information in said multi-media data signal such that said additional generation of control tag information replaces said master tag information.

76. The apparatus of claim 49, wherein:

said encoder is operatively associated with said receiver for degrading the quality of said primary multi-media data signal such that succeeding encoded generations of said primary multi-media data signal have an increasingly degraded quality.

77. A method for controlling the reproduction of a primary multi-media data signal using an auxiliary multi-media data signal, where master tag information is embedded in at least one of said primary and auxiliary multi-media data signals, and at least one of said primary and auxiliary multi-media data signals is adapted to carry control tag information embedded therein, comprising the steps of:

(a) retrieving said master tag information embedded in said at least one of said primary and auxiliary multi-media data signals;

(b) retrieving said control tag information, if any, embedded in said at least one of said primary and auxiliary multi-media data signals;

(c) determining the number of generations of said control tag information;

(d) determining whether the number of said generations of control tag information is below a threshold level; and

;

(i) if so, providing an additional generation of control tag information in said at least one of said primary and auxiliary multi-media data signals; and

,

(ii) if not, inhibiting the reproduction of said primary multi-media data signal.

78. The method of claim 77, comprising the further step of:

determining said threshold level according to said master tag information.

79. The method of claim 77, wherein:

the master tag information is embedded in said auxiliary multi-media data signal, and said auxiliary multi-media data signal is adapted to carry the control tag information embedded therein.

80. The method of claim 77, wherein:

the master tag information is embedded in said primary multi-media data signals, and said auxiliary multi-media data signal is adapted to carry the control tag information embedded therein.

81. The method of claim 80, wherein:

said step (d)(i) provides said additional generation of control tag information at a level calculated to cumulatively degrade the quality of said primary multi-media data signal according to said number of generations of control tag information.

82. The method of claim 77, wherein:

said encoder provides said additional generation of control tag information in said primary multi-media data signal.

83. The method of claim 77, wherein:

said primary and auxiliary multi-media data signals are carried on a common source media.

84. The method of claim 77, comprising at least one of the further steps of:

(a) spectrally shaping said additional generation of control tag information according to said at least one of said primary and auxiliary multi-media data signals; and

(b) adjusting the power of said additional generation of control tag information according to said at least one of said primary and auxiliary multi-media data signals.

85. The method of claim 77, comprising at least one of the further steps of:

(a) spectrally shaping said master tag information according to said at least one of said primary and auxiliary multi-media data signals; and

(b) adjusting the power of said master tag information according to said at least one of said primary and auxiliary multi-media data signals.

86. The method of claim 77, wherein:

at least one of said spectral shaping and power adjusting steps render said master tag information at a desired level.

87. The method of claim 77, wherein:

said inhibiting step prevents reproduction of said primary multi-media data signal.

88. The method of claim 77, comprising the further step of:

providing cryptographic data embedded in said at least one of said primary and auxiliary multi-media data signals to enable the decryption of data packets carried together with said at least one of said primary and auxiliary multi-media data signals.

89. The method of claim 77, wherein:

said primary multi-media data signal comprises at least one frame of multi-media data which is encrypted under an encryption key; and

said auxiliary multi-media data signal comprises an encryption key layer with at least one packet containing said encryption key for decrypting said at least one frame of the primary multi-media data signal.

90. The method of claim 77, wherein:

said additional generation of control tag information is provided as a spread spectrum signal.

91. The method of claim 77, wherein:

said master tag information is provided as a spread spectrum signal.

92. The method of claim 77, wherein:

said at least one of said primary and auxiliary multi-media data signals comprises compressed digital data; and

said additional generation of control tag information is provided without decompressing said compressed digital data.

93. The method of claim 77, comprising the further steps of:

providing said master tag information as a spread spectrum signal in accordance with an associated pseudo-random sequence in at least one time segment of said at least one of said primary and auxiliary multi-media data signals;

providing said additional generation of control tag information as a spread spectrum signal using said associated pseudo-random sequence; and

providing said additional generation of control tag information in said at least one of said primary and auxiliary multi-media data signals in a time segment which is unaligned relative to said at least one time segment in which said master tag information is carried.

94. The method of claim 77, wherein at least one of said master tag information and said control tag information, if any, is provided as a spread spectrum signal, comprising the further step of:

providing said additional generation of control tag information as a spread spectrum signal which is distinguishable from said at least one of said master tag information and said control tag information.

95. The method of claim 77, wherein at least one of said master tag information and said control tag information, if any, is provided as a spread spectrum signal in accordance with a first pseudo-random sequence, comprising the further steps of:

providing additional generations of control tag information as distinct spread spectrum signals by using different pseudo-random sequences; and

providing said additional generation of control tag information as a spread spectrum signal in accordance with a second pseudo-random sequence which is distinct from said first pseudo-random sequence.

96. The method of claim 77, comprising the further step of:

providing additional generations of control tag information in a plurality of non-adjacent time segments of said at least one of said primary and auxiliary multi-media data signals.

97. The method of claim 77, comprising the further step of:

providing said master tag information in a plurality of non-adjacent time segments of said multi-media data signal.

98. The method of claim 77, wherein:

said encoder provides said additional generation of control tag information in said auxiliary multi-media data signal.

99. The method of claim 77, comprising the further step of:

providing at least one of said master tag information and said control tag information in defined intervals of said at least one of said primary and auxiliary multi-media data signals to carry information in said at least one of said primary and auxiliary multi-media data signals according to a binary signaling scheme.

100. The method of claim 77, wherein:

said at least one of said primary and auxiliary multi-media data signals comprises video data.

101. The method of claim 77, comprising the further step of:

wherein said number of generations of detected control tag information is at least one.

102. The method of claim 77, wherein:

said step (d)(i) provides said additional generation of control tag information in said at least one of said primary and auxiliary multi-media data signals such that said additional generation of control tag information replaces said master tag information.

103. The method of claim 77, comprising the further step of:

degrading the quality of said primary multi-media data signal such that succeeding encoded generations of said primary multi-media data signal have an increasingly degraded quality.