UPDATE 1-Global set-top box market to jump in Q4 -- study

(Adds details on set-top market)

HELSINKI, Dec 11 (Reuters) - Global set-top box market is set for strong Christmas sales after contracting in the third quarter when cable operators in the United States sold down inventories, research firm Dell'Oro Group said on Tuesday.

The value of global set-top box market declined 2 percent and volumes fell 7 percent in the third quarter sequentially, the market research firm said, as U.S. cable operators built up inventories of mostly standard set-tops in the January-June period as they strived to convert analog subscribers to digital.

Set-top boxes is a $10.9 billion industry this year, Dell'Oro said, with France's Thompson Group (TMS.PA) and Motorola Inc (MOT.N), the largest players in the world.

Dell'Oro forecast the global market would grow 21 percent in the forth quarter from the previous three-month period, boosted by holiday sales. Market volume is set to grow 18 percent from the third quarter, with average price increasing.

"Holiday sales of televisions lead consumers to upgrade or change their television service," said Greg Collins, vice president at Dell'Oro.

"We also expect that there will be a higher percentage of set-top sales that include high definition and/or digital video recording (DVR) functionality during the quarter," he said. (Reporting by Tarmo Virki; Editing by Andre Grenon)