Process for the transmission and reception of conditional access programmes with a reduced programme switching time

摘要

A process for the transmission and reception of scrambled conditional access programs, which are synchronously transmitted with entitlement control messages (ECM), with a reduced program switching time. The entitlement control messages (ECM) have check words, which are changed after a period of time called a phase, for descrambling the conditional access programs. The process includes transmitting main check messages (ECMp) for a main access program at a first frequency (Fp) and transmitting secondary check messages (ECMs) for secondary programs at a lower, second frequency (Fs). The secondary check messages (ECMs) are transmitted between two successive transmission of the main check messages (ECMp) such that all of the secondary check messages (ECMs) for each of the secondary programs are transmitted in a single phase. Therefore, a check word for any program is quickly acquired and program switching time is reduced.