Apparatus for scrambled transmission of video signals

摘要

PCT No. PCT/GB92/01786 Sec. 371 Date Jun. 13, 1994 Sec. 102(e) Date Jun. 13, 1994 PCT Filed Sep. 29, 1992 PCT Pub. No. WO93/07718 PCT Pub. Date Apr. 15, 1993Video signals are sampled at 4Fsc locked onto sub-carrier phase and frequency. The active picture lines of each field are divided into 6 blocks of 47 lines and the active line periods of those lines scrambled on a block by block basis by line order shuffling. The shuffling algorithm is generated by a line shuffling permutator driven by a PRBS generator (controls 36, 38). Active line period samples for one block are written in unscrambled form into a first memory block (32) and samples from the previous block are read out in scrambled form from a second memory block (34) for transmission. The complementary process takes place in the decoder.