| 摘要 |
<p>The method is applicable in particular to scrambling television signals by modifying the order of the lines. The method permutes the lines blockwise, each block consisting of N successive active video data lines. The device enabling the method to be implemented comprises: a picture memory (10) provided with an input (12) for receiving incoming data, an output (14) for outgoing data and an addressing input (18); means (20) for managing the permutations, provided in order to supply a list of addresses describing the permutation to be applied to the next block to be permuted, a permutation memory (42) intended to store the permutation list to be effected at successive addressable locations, two address memories (44, 46) whose data inputs and outputs are looped back to one another, one of the address memories (44) having an addressing input which can be connected to the output of the permutation memory and a data output provided for connection to the addressing input of the picture memory (10) during permutations whilst the said memory operates in read mode, the other address memory operating in write mode and in read mode and; a line-index counter (30) incremented at the rate at which lines appear. <IMAGE></p> |
