By many accounts, Chiariglione has played a key role in holding together the loose coalition of record companies, consumer-electronics manufacturers and computer companies that is seeking technology standards aimed at preventing widespread digital piracy.
The group will look for another director to serve as Chiariglione's replacement as he phases out responsibilities over the next few months, a representative said. That could add another delay to a group criticized by many for being too slow.
Group members said Chiariglione's loss would be felt but that SDMI would be able to continue without him.
"It's obviously not good news. But it's not detrimental to the point where SDMI falls apart," said Gregg Moskowitz, vice president of business development at Blue Spike, a company with technology being reviewed by SDMI. "It's up to all the factions in the group to come together on their own."
Chiariglione, who also helped found the Moving Pictures Expert Group (MPEG) that produced the MP3 music format, has been a consistent and testy critic of SDMI's opponents, which charge the group with trying to exert too much control over how music is used and distributed. He has said critics want to create an "inquisition" that would weed out technology that wasn't to their liking.
His stewardship saw the quick development of an early version of a technology standard for copyright protection. But few companies have supported that standard in their devices or software, and a more ambitious version has been long delayed.
"I think he has done a very good job," Moskowitz said. "But everyone has had (their) own agenda, and there's only so much one person can do."
Chiariglione is withdrawing because of increased responsibilities at his job at Telecom Italia research division CSLET, a representative said.