But those leisurely stretches of break-free programs could be going away.

PBS officials told member stations at its recent annual meeting in Orlando that beginning this fall, the Wednesday science series “Nature” and “Nova” would contain corporate and foundation sponsor spots, promotional messages and branding within four breaks inside the shows, instead of at the very beginning and end.

The longest period of uninterrupted programming, according to a plan shown to the programmers, would be just under 15 minutes, compared with the current 50 minutes or more. Based on what PBS learns in the fall, the new format would continue to be introduced night by night through the year, officials said.

Even before the plan became public last week, it was being intensely debated among PBS station executives and program producers. While many support testing the new model, others are worried about how viewers and the financial supporters will react, and if PBS can recover should they react badly.

The great unknowns are whether PBS viewers will welcome receiving programming in shorter bites, or rebel against a move they see as more commercial, and if foundation supporters will see the change as an abdication of mission.

“One of the biggest things they have to sell is that they are noncommercial,” said David D. Oxenford, a partner with the law firm Davis Wright Tremaine, who represents some public broadcasters.

“My first reaction is that in any kind of marketing opportunity, if you give up something that is desirable and differentiates you from your competition, it’s too bad, and that’s what this is,” said Alberto Ibargüen, a former PBS board chairman and president and chief executive of the Knight Foundation, which finances some public broadcasting initiatives. But, he added, “the people of PBS would not do this lightly.”

The change is meant to address a serious problem. Currently, the messages that a PBS station broadcasts are packed into a block at the end of each show, which, for hourlong programs, sometimes stretches to nearly eight minutes. Not surprisingly, viewers routinely flee.

“It’s almost as if someone pulled the fire alarm and they scrambled for the exits,” John F. Wilson, the chief programming executive for PBS, told attendees to the annual meeting, while exhibiting a Nielsen ratings chart showing a steep cliff where the audience disappeared between shows. (PBS executives declined to quantify the falloff depicted.)

Such an exodus makes it harder for PBS to build up an audience for the show that follows, Mr. Wilson said.

Under the new plan, there would be no break between shows, a transition known as a “hot switch” used by many cable networks. To accomplish this, the sponsor messages, PBS “Be more” branding spots, and show promotions would run inside programs, in short pods of under two minutes.

Mr. Wilson, in an interview, said viewers would never be more than one minute and 40 seconds away from actual program content. And, he noted, PBS shows would still be “the longest hour in television in terms of content,” with as much as 54 minutes of programming, compared with about 40 minutes for commercial networks.

All shows may not end up being candidates for breaks. “I’d look really carefully at a ‘Masterpiece’ drama, at how we’d do that or how often we’d do that,” he said. But many producers, who now have the luxury of structuring their shows without worrying about where the breaks will come, are likely to have to adapt. PBS is meeting with some concerned producers this week.

Jon Abbott, the president and chief executive of WGBH in Boston, which produces “Nova,” “Masterpiece” and “Frontline,” among others, called it a “missed opportunity” if viewers don’t see the work. He added, however, that “we have a lot of people who care about the work and care about our way of presenting work; that trust, the values that people place in public media are things that we are very attentive to and respectful of.”

The plan is “a fundamental change” likely to elicit viewer complaints, John Boland, the president and chief executive of KQED in San Francisco, said via e-mail. However, in the end, he wrote, “this is not a test of what people say but rather what they do. Do they spend more time or less time watching PBS stations with embedded breaks and a hot switch? There is ample evidence that this strategy has worked for commercial TV, and there is ample evidence that our viewers may be concerned about change but won’t desert us if we provide a reasonable explanation and continue to provide quality programming that simply is not available anywhere else (and certainly not available without interruption).”

PBS told station executives that they should check with their lawyers to make sure that they weren’t violating Federal Communications Commission policy governing noncommercial stations, but Mr. Wilson said he was confident the new policy wa legal. F.C.C. guidelines, he said, allow stations to acknowledge sponsors at “natural breaks,” and shows like “Nova” and “Antiques Roadshow” can be divided into chapters, just as noncommercial NPR programs already do.

“It’s not like this is untested, uncharted territory in some respect,” he said.

Mr. Oxenford said that under F.C.C. rules, announcements and acknowledgements may not interrupt regular programming. But sponsor messages are allowed at the beginning and end of shows, between identifiable segments of longer programs, or during station breaks, “such that the flow of programming is not unduly interrupted.”

Programs like “Antiques Roadshow,” which PBS said was scheduled to move to the new model starting in January, might indeed have identifiable breaks, “between looking at Grandma’s sofa and the 1850s flintlock someone had in their basement,” he said.

Article source: http://feeds.nytimes.com/click.phdo?i=98f44bc70ef0e9d3b5a26d2fc8b2c7fb