By Andy Trott, DCE Satellite Communications and Michael E. Long, Zenith Cable Products
Many systems currently exist to scramble a composite video television picture, but most suffer from both technical and commercial flaws which can seriously compromise performance and security. Most recently, digital compression and transmission of NTSC, PAL or SECAM video has been envisioned as the ultimate answer to video scrambling and protection from theft of service, but the cost of implementation is high. This paper presents an alternative analog scrambling system with the benefits of video digital processing for hard security and concealment without the high costs associated with full digital compression.
A line-shuffling analog video scrambling system, compatible with NTSC, PAL or SECAM systems, is presented which randomly displaces video lines in a video field to render the resulting television image unviewable but capable of being transmitted and received with standard equipment. By utilizing special memory addressing techniques, only one block of memory is required to continuously scramble successive blocks of video, thereby reducing system components and cost. A fully encrypted conditional access system is also included to provide protection against piracy without the need for "smart-cards" to renew security.