Comcast (News - Alert) is planning to start limited tests for a new hybrid TV service that brings YouTube-like online video capabilities to its X1 cable set-top boxes.

The No. 1 cable MSO told GigaOm that trials should start by the end of the year.

The experiment will involve a dedicated app that’s accessible via the STB; and “content creators” can upload their own videos to the server to make them available to viewers. Producers will likely be able to wrap in advertising or use a transactional fee model, but the company is “still evaluating its options.”

The service will differ drastically from YouTube (News - Alert), however, in the fact that user-generated content will not be a piece of the picture. This is unsurprising given the overhead that would be involved in policing the portal for pirated or inappropriate content; there’s only so far that a cable operator is willing to go to bring the ‘Net to the television.

However, while professionally produced video will be the focus, the gambit will be a showcase for long-tail Web content and multilingual fare. Taking a streaming video approach allows Comcast to unburden itself from the requirement to monetize less-viewed content via the traditional advertising model.

Today’s traditional linear TV model is geared to encourage cablecos to embrace only the more popular content. More eyeballs and ratings equals higher CPMs for commercials, which need to be high to pay for skyrocketing programming costs.

Offering a streaming option allows Comcast to circumvent that treadmill, and can be an entry point for Comcast to find “new” audiences and improve customer retention.

Speaking of monetization, debuting a streaming portal also gives Comcast a way to experiment with new technology. In March, Comcast purchased the video advertising technology firm FreeWheel, which is one of the biggest platforms that TV networks and online content producers use to serve ads inside Web video content, with clients including FOX, AOL, Viacom (News - Alert) and Turner Sports. It’s a specialist in addressable advertising, which is something that thus far, Comcast has not gotten into.