Cryptography – Video cryptography – Video electric signal modification
Patent
1998-01-27
2000-06-06
Hayes, Gail O.
Cryptography
Video cryptography
Video electric signal modification
380226, 348441, H04N 7167
Patent
active
060728728
ABSTRACT:
A signal such as an analog scrambled television signal in a cable television network has first scrambling mode data which is compatible with a first decoder population, but not a second decoder population. The scrambled television signal is processed to determine the scrambling mode without recovering the first scrambling mode data. Second scrambling mode data which is compatible with the second decoder population is then provided in the scrambled television signal, for example, in the vertical blanking interval or on an audio subcarrier. During processing to determine the scrambling mode, the television signal is delayed, e.g., by digitizing it and temporarily storing it in memory. The delay compensates for the time required to determine the scrambling mode. The television signal is recovered in the analog domain prior to inserting the second scrambling mode data. The system is compatible with various scrambling modes, including sync suppression and inversion of the active video as well as with dynamic scrambling mode changes.
REFERENCES:
patent: 4598318 (1986-07-01), Robbins
patent: 4790011 (1988-12-01), Bellavia, Jr.
patent: 5138659 (1992-08-01), Kelkar et al.
Coffell, "Tri-Mode Cable-TV Scrambling," Radio Electronics, vol. 58, No. 2, pp. 43-47 and 120, Feb. 1997.
Chang Kevin T.
Stufflet Alfred W.
Coddington Trevor Quick
General Instrument Corporation
Hayes Gail O.
Hoppin Ralph F.
Lipsitz Barry R.
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