CBS expects broadcast TV's overall ad revenue to remain steady in 2017.

Excluding the effects of the Summer Olympics, broadcast TV ad growth next year will be about 4%, roughly in line with 2016, David Poltrack, chief research officer at CBS, said during the UBS Global Media and Communications Conference in New York Monday morning.

Mr. Poltrack said the TV ad market is showing more stability compared to the last several years, and an increase in GDP growth, an acceleration in consumer spending, wage growth and pickup in retail sales are positives for 2017.

At the same time, Mr. Poltrack lowered his 2016 forecast as more ad spending on the Olympics came from existing budgets thann he had anticipated. He now predicts broadcast ad growth of 8%, down from his previous forecast of 9.5%. Excluding the Olympics, he expects ad growth will be 4%, down from his earlier estimate of a 5% increase.

This is still impressive growth, Mr. Poltrack contended, with ad sales buoyed by a strong upfront as some marketers shifted some money from digital back to TV. Mr. Poltrack said the fourth-quarter scatter market, where advertisers are buying commercial time close to its air date, remains robust and that momentum is carrying over into the first quarter of 2017.

During his presentation, Mr. Poltrack called for the separation of long-form digital video from the likes of TV programmers from the rest of digital advertising.

"Long-form video is a hybrid media extension that belongs as much in the 'television' sector as it does in the 'digital' sector," Mr. Poltrack said. "The dynamics of this unique hybrid media form are much further removed from the dynamics of digital search than they are from the dynamics of the CBS Television Network or of Showtime."

Mr. Poltrack said he expects advertising in long-form video to grow 40% in 2017 compared to an increase of 11% for the rest of the digital sector.