Comcast is considering the purchase of Visible World, a firm that specializes in helping advertisers create and distribute commercials for specific groups of TV viewers, according to a report in the Wall Street Journal, the latest signal that big media companies are trying to gird themselves against new pressure from sponsors to help them reach smaller, better-defined groups of consumers.

The deal is not imminent, the report cautioned, and the two companies could end up forming a partnership instead. The newspaper attributed its information to “people familiar with the matter.”

New York-based Visible World uses technology to help advertisers create commercials tailored to discrete segments of the TV audience, using set-top boxes. The company might help a carmaker alter the copy about the terms of sale in one ad, or change the voiceover or graphic elements in another. Advertisers can use the company to run ads that vary according to the time of day, or even the context in which it appears.

Comcast’s interest in Visible World is indicative of the new ways in which marketers are trying to use TV. Armed with information about consumer habits, advertisers are placing more emphasis on reaching better-defined consumer groups, like first-time car buyers, expectant mothers, or teen soda drinkers. With TV audiences splintering among dozens of new types of viewing behaviors — video-on-demand, video streaming, time-shifting viewing — they are collecting into groups that are more easily targeted, and the ability to reach them with video delivered via broadband means advertisers have more ways to examine their behavior and interests.