A digital video conversion system housing multiple converter chains of units in a single main box chassis. A preferred embodiment uses only a single conditional access unit to authorize decryption of premium channels in response to a smartcard. The conversion system allows a single converter box sharing consolidated decryption (access control) circuitry and a single remote control receiver to provide video output for multiple television sets on the subscriber's premises. In addition to reducing the subscriber's hardware costs per television set, a common access control allows the video service provider to grant a multiple-set discount on a single smartcard.