SCRAMBLING, DESCRAMBLING AND A SECURED DISTRIBUTION OF AUDIO-VISUAL SEQUENCES FROM DCT-BASED VIDEO DECODERS

摘要

The invention relates to a method and device for securely distributing video sequences according to a digital stream format which is based on a DCT transformation and consists of frames comprising fixed-sized or variable-sized blocks. At least one part of blocks is calculated with the aid of a temporal prediction and a spatial prediction optimised on the basis of adjacent blocks. The prediction mode, segmentation into blocks and decoding and filtering parameters for displaying are given in a binary stream. Said inventive method consists, prior to transmitting to user equipment, in analysing a stream in order to generate a main modified stream comprising the original stream format, complementary information having any format and containing numerical data which makes it possible to reconstruct said modified frames and, afterwards separately transmit said modified main stream and complementary information which are thus generated during a distribution phase from a server to addressed equipment.