Maintaining accurate channel line-up by persistently monitoring availability of accessible channels

摘要

A channel updater. The channel updater maintains an accurate channel line-up by automatically testing accessible channels to determine if those channels are available for viewing. Available channels are added to the channel line-up, and unavailable channels are subtracted from the channel line-up. The updater persistently retests the channels so that changes in channel availability are reflected in the channel line-up.