Subscription television system.

摘要

In a subscription television system, the video signals constituting a specific program has its video portion scrambled in accordance with a predetermined scrambling scheme and a key signal which is used for unscrambling the scrambled video signal is generated in response to the scrambling mode. The key signal is not transmitted until after termination of transmission of the specific program so that correct decoding of the signal in real time is not possible. Various scrambling schemes, including one for the audio part of the video signal are disclosed.