Method and apparatus for digitizing a scrambled analog video signal

摘要

An on demand services feature for the provision of video, audio, and data services for a subscription system of the CTV type, or the like. The system comprises a headend coupled to a distribution network having a multiplicity of subscribers. Standard service signals forming scheduled program channels are coupled commonly with on demand service signals forming on demand program channels in a frequency division multiplexed system. The demand services are provided by a demand service processor having an input processor which stores programs for the demand services in a file server or other massive memory and a plurality of output processors which retrieve the programs on demand and convert them to the demand service signals for application to the distribution network. In the illustrated embodiment the input processor scrambles, digitizes and compresses real time or other stored analog programming for storage in the file server. On demand from a subscriber, an output processor reads out a stored program from the file server as a digital data stream, decompresses it and converts it back to an analog scrambled signal. The analog scrambled signal is then modulated on a carrier by the output processor to become an on demand services signal.