Systems and methods for retrofitting electronic appliances to accept different content formats

Systems and methods are disclosed for using an arbitrary fixed channel to carry third-party information. In one embodiment, the present invention provides systems and methods for enabling existing content rendering devices to accept content encoded in a proprietary format, such as an encoding format used by a digital rights management system. The encoded content is rendered by the device in the normal manner, and decoded by a retrofitting appliance connected to the device's output. The retrofitting appliance may apply decoded rules and controls to the decoded content, thereby managing use of the content.