Scramble methods and apparatus for packetized digital video signal in conditional access system
First Claim
1. A method of scrambling a data stream, comprising:
- encoding a plurality of video frames to generate a compressed bitstream;
generating a stream of transport packets to transport the compressed bitstream, wherein each transport packet has a fixed length and comprises (i) a header and (ii) a payload having data from the compressed bitstream;
selecting every n-th transport packet in said stream of transport packets for scrambling processing, where n is a positive integer;
in each selected transport packet, scrambling a first portion of the payload while leaving at least a second portion of the payload unscrambled to generate a corresponding scrambled transport packet; and
transmitting a stream of transport packets having the generated scrambled transport packets from a transmitter of a conditional access system.
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Accused Products
Abstract
A conditional access scrambling or encryption technique for a packetized digital data stream, e.g., a MPEG-2 bitstream, (1) by scrambling or encrypting the data payload of selective transport payload packets (e.g., every nth packet); (2) by scrambling or encrypting only a portion (e.g., a central portion) of the data payload of every transport payload packets; or (3) by both scrambling or encrypting the data payload of every nth packet and scrambling or encrypting only a portion of the data payload of every transport payload packet. With advance knowledge by the subscriber'"'"'s descrambler of which payload packets are being scrambled, and/or of which portion of which payload packets, descrambling can be performed with minimal processing and without the need to first recreate the underlying image and/or audio.
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Citations
27 Claims
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1. A method of scrambling a data stream, comprising:
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encoding a plurality of video frames to generate a compressed bitstream; generating a stream of transport packets to transport the compressed bitstream, wherein each transport packet has a fixed length and comprises (i) a header and (ii) a payload having data from the compressed bitstream; selecting every n-th transport packet in said stream of transport packets for scrambling processing, where n is a positive integer; in each selected transport packet, scrambling a first portion of the payload while leaving at least a second portion of the payload unscrambled to generate a corresponding scrambled transport packet; and transmitting a stream of transport packets having the generated scrambled transport packets from a transmitter of a conditional access system. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14)
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15. Apparatus for scrambling a data stream, comprising:
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means for encoding a plurality of video frames to generate a compressed bitstream; means for generating a stream of transport packets to transport the compressed bitstream, wherein each transport packet has a fixed length and comprises (i) a header and (ii) a payload having data from the compressed bitstream; means for selecting every n-th transport packet in said stream of transport packets for scrambling processing, where n is a positive integer; and means for scrambling a first portion of the payload in each selected transport packet while leaving at least a second portion of the payload unscrambled.
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16. A descrambling method, comprising:
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receiving, at a receiver of a conditional access system, a stream of transport packets that transports a compressed bitstream, wherein; each transport packet has a fixed length and comprises (i) a header and (ii) a payload having data from the compressed bitstream; and the compressed bitstream encodes a plurality of video frames; selecting every n-th transport packet in said stream of transport packets for descrambling processing, where n is a positive integer; in each selected transport packet, descrambling a first portion of the payload while not subjecting at least a second portion of the payload to descrambling; and reconstructing the compressed bitstream using the descrambled first portions of the selected transport packets. - View Dependent Claims (17, 18, 19, 20, 21, 22, 23, 24, 25, 26)
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27. A receiver, comprising:
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means for receiving a stream of transport packets that transports a compressed bitstream, wherein; each transport packet has a fixed length and comprises (i) a header and (ii) a payload having data from the compressed bitstream; and the compressed bitstream encodes a plurality of video frames; means for selecting every n-th transport packet in said stream of transport packets for descrambling processing, where n is a positive integer; means for descrambling a first portion of the payload in each selected transport packet and not subjecting at least a second portion of the payload to descrambling; and means for reconstructing the compressed bitstream using the descrambled first portions of the selected transport packets.
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Specification