Walt Disney Studios chairman Dick Cook said Tuesday that as the studio downsizes its film output to 12-13 pictures per year with an emphasis on Disney-branded movies, it is replacing Nina Jacobson, who had headed its live-action film efforts. Oren Aviv, who has been serving as president of marketing and chief creative officer, will take over Disney's film production.

As part of the major corporate shake-up, Disney will reduce its work force by 650 positions worldwide, about 20% of its current work force, Cook said.

Aviv will take on the title of president of production at Walt Disney Pictures. Jim Gallagher, who has been serving as senior vp creative services, will replace Aviv as marketing president.

In addition, the studio is reorganizing its international businesses under two global units. Mark Zoradi, who has overseen international distribution, will add domestic distribution to his portfolio. He has been appointed president of Walt Disney Motion Pictures Group, overseeing the distribution and marketing of all Disney and Touchstone films worldwide through Buena Vista Worldwide Marketing and Distribution. Robert Chapek, who has headed Disney's domestic home video efforts, will now look after international home video as well. He was named president of Buena Vista Worldwide Home Entertainment, overseeing the worldwide distribution and marketing of the studio's films on home entertainment platforms through BVWHE.

Aviv, Zoradi and Chapek will report to Cook. Gallagher will report to Zoradi.

"It's a global business, no longer in L.A. and New York," Cook said of the reorganization. "As emerging markets become more important to us, we have to think about how best to organize and find efficiencies." Thus, it made sense for Cook to merge international and domestic marketing, he said.

The studio has not released details of the impending layoffs, which will cut deep into its worldwide film and home video operations, about 50-50 domestic and international, Cook said. Production is expected to take less of a hit, with cuts spread out through finance, legal, distribution and marketing. Exempted from the cuts are Miramax Films as well as Walt Disney Feature Animation, Pixar Studios, Buena Vista Music Group and Buena Vista Theatrical Prods.

The moves come as Disney is enjoying a record-breaking boxoffice success with "Pirates of the Caribbean: Dead Man's Chest," which has grossed $266 million domestically in 11 days, while also fielding a hit in the Pixar-animated "Cars," which has grossed $221 million domestically. But Disney has stumbled in recent years, ending up in fourth place among the major studios in the 2005 domestic market share race. Under the oversight of Walt Disney Co. CEO Robert Iger and Cook, Disney has been conducting a yearlong review of its operations.

"We've been doing things the same way for years and years," Cook said. "This is not something so appropriate to the entire industry. It's very specific to us. We have a real brand name known around the world. When we started looking at the kind of movies we wanted to make under the Disney umbrella, we had Pixar's 'Cars' rated G, and 'Pirates of the Caribbean' rated PG-13, from (producer) Jerry Bruckheimer. They both live in harmony under the Disney brand."

Building the Disney brand is crucial to the new studio mandate. "What can we do better than anyone else? -- make Disney movies," Cook said. He noted that there is no plan to spend less money on production or to cut any producer deals or deny such star producers as Bruckheimer or Scott Rudin their two or three movies a year. He insisted that "there were no pressures at all" on him to cut staff, though he cited "a ton of support from Bob Iger to do all this. I never had a gun to my head. This came out of internal planning of what we wanted the business to look like for us."

The new plan calls for the studio to produce 10 Disney live-action and animated films per year plus another two or three adult-oriented Touchstone Pictures films.

With Bruckheimer of late concentrating on producing movies like "Pirates," which brandish the Disney label proudly, industry watchers are assuming that New York-based Rudin and other Disney producers will compete for the available Touchstone slots. Rudin, who Jacobson helped bring to the studio, may wind up delivering more projects to Disney specialty subsidiary Miramax as well as rival studios.

Jacobson heard the news at the hospital Tuesday, when partner Jen Bleakley had just given birth to a baby boy, their third child. When she called Cook to share her news, he alerted her to the changes when she asked him what was going on.

"I have a lot of love and admiration for Nina. She's a great colleague and friend. There is no smarter executive," Cook said, adding, "There are times when these things happen, and this one of those times. She leaves a great legacy."

The news blindsided studio employees Tuesday. Many expressed shock and sadness to see Jacobson go. "She's a straight shooter. In good times and bad, she dealt with you straight, which is a rarity," one producer said.

Said Bruckheimer: "I had a great run with Nina. We made some really successful pictures together, the last one being the most successful. And they are difficult to get made, and she fought for us the whole way."

Another insider expressed disillusionment, saying: "She's basically getting fired after the biggest movie of the year. There are no sacred cows in this town anymore."

Aviv has long been interested in playing a larger role in film production and served as exec producer as well as sharing a "story by" credit on 2004's "National Treasure." His leverage at Disney increased last year when he turned down an offer from Paramount Pictures chairman Brad Grey to run production at the Melrose Avenue studio.

"I have been working with Oren since I've been at Disney," Bruckheimer said. "He's creative and smart. He will adapt, I'm not worried about that."

"Oren understands the big idea movie," another Disney producer said. "He is very commercial and is like, 'How can I sell this movie?' "

Aviv's ascension -- like Marc Shmuger's to chairman of Universal Pictures -- is illustrative of the increasing clout marketing execs now have at the studios. "The single most important person at a studio is the marketing person," one producer said. "When they are good, like Aviv and Shmuger, they are irreplaceable. The market is driven by marketing, not quality."

"When you're putting together a team, you always draft for talent, whether they're coming out of marketing or production. Oren has tons and tons of talent," Cook said.

Aviv's appointment also appears to underscore the shift in the kinds of movies the studio will be making. Jacobson, who has been at Disney since 1998 and was promoted to her current position in 2000, is respected for her candor and willingness to fight for projects in which she believes, but she also has cultivated a reputation for nurturing eclectic directors, such as Wes Anderson ("The Royal Tenenbaums," "The Life Aquatic With Steve Zissou") and the Coen brothers, who might not fit Disney's current emphasis on tentpole family films. At the same time, she's also overseen such family-friendly movies as "Princess Diaries" and "Freaky Friday."

But some considered Jacobson vulnerable because she was brought in under former Disney motion picture chairman Joe Roth and had a close relationship with deposed Disney CEO Michael Eisner. Under the new mandate to support the Disney family brand, Aviv's "National Treasure" was deemed closer to the mark than many of Jacobson's artier projects.

"Nina Jacobson is and has always been one of the most talented and passionate advocates of good movies and serious work in our industry," Rudin said. "I love her as a colleague, I love her as a boss, and I love her as a friend."

Jacobson herself was philosophical, saying in a statement: "The studio is undergoing a major reorganization, and there simply isn't room for everyone in the new structure. I love the company, and it has been a great honor to be part of building the Walt Disney brand. I've had the opportunity to work on films that I love, with filmmakers I admire and colleagues I adore. I'm sorry to go, but I am proud of what I've left behind, a vibrant movie studio with major franchises and thriving relationships with some of the most talented filmmakers in the world."

Upcoming releases Jacobson has been shepherding include "The Guardian," starring Kevin Costner and Ashton Kutcher; "The Prestige," directed by Christopher Nolan and starring Hugh Jackman and Christian Bale; "The Santa Clause 3," starring Tim Allen; "Deja Vu," directed by Tony Scott and starring Denzel Washington; and "Invincible," starring Mark Wahlberg and Greg Kinnear.