Comcast is continuing to expand its On Demand Online portal for streaming TV shows, although the service will only be available to the company's own broadband subscribers, according to the Associated Press. The web-based content is said to eventually match the on-demand capabilities available through certain set-top boxes.

Cable subscribers initially will be forced to watch shows and movies from their home computers. Comcast is working on a verification system for each home computer, while the streams will be barred from any system utilizing a broadband modem from another company.

The initial restrictions will effectively prevent Comcasct subscribers from accessing the On Demand Online shows from cellphones, or even at home if they use a separate provider for Internet service.

Despite the lack of compatibility as the service is first launched, the company is reportedly working to extend the streaming capabilities to other platforms. As the company refines its verification methods, Online On Demand will be accessible away from home and eventually from cellphones. A recent report suggests the company may launch its own WiMAX-based voice service, however, instead of offering the streaming content through other carriers such as AT&T and Verizon.

The Online On Demand service is currently being trialed with a limited number of subscribers. The formal roll-out is expected by the end of the year.