A system for inserting commercials into an audiovisual bit stream by providing cue commands in response to cue tones in a pre-existing analog signal, and/or in response to control signals from an uplink (/programmer/network) site or headend (/affiliate). Firmware upgrades are provided to a digital encoder...http://www.google.de/patents/US6487721?utm_source=gb-gplus-sharePatent US6487721 - Apparatus and method for digital advertisement insertion in a bitstream
