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US 5,177,485 AGranted
Method of scrambling PAL, SECAM and NTSC composite video signals and decoder of signals scrambled by this method
AssigneeLaboratoire Europeen de Recherches Electroniques Avancees
InventorsPatrick Daniel, Jean-Claude Guillon
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Abstract
The method of the invention consists in shifting (a) the start of the scrambled section of a composite video line of a television image with respect to the start of the useful part of that line.
Claims7
A method of processing PAL and SECAM composite video signals, comprising the steps of:
- scrambling the composite video signals by line permutation controlled by a pseudo-random sequence, wherein the pseudo-random sequence is based on a control word with an encoded value incorporated in the composite video signals, the scrambling comprising the step of shifting a start of a scrambed zone of a video signal segment of each line of the composite video signals with respect to a start of each line so that a beginning of video information is not subject to scrambling;
- descrambling the scrambled composite video signal by using the pseudo-random sequence which is identical and synchronized with the pseudo-random sequence used in the scrambling step.
A decoder for an image transmission system comprising:
- a receiver for receiving scrambled composite video signals;
- a descrambler for descrambling the scrambled composite video signals, the descrambler comprising in a parallel connection:
- two FIFO queues each acting as a delay line and having write/read counters and zero reset inputs, wherein the write/read counters are only accessible by the zero reset inputs;
- and
- a buffer register.
2 more elements
Dependencies are inferred from the claim text.