Warner Brothers is to release high definition films only in Sony's Blu-ray format, in a blow to rivals in the long-running format war.
Warner was the only major studio still releasing films both in the competing Blu-ray and HD DVD formats.
Five studios now back Blu-ray solely. Only Universal Pictures and Paramount Pictures favour HD DVD.
The backers of HD DVD deny their format is dead but admitted disappointment with the Warner decision.
Walt Disney, Twentieth Century Fox, Metro-Goldwyn-Mayer and Sony Pictures are the other studios that only release in Blu-ray format.
Both formats deliver high definition pictures and sound and work with HD televisions, but they are not compatible with each other and neither will play on older DVD players.
Warner said it had opted for Blu-ray because 60% of its US high-definition sales last year had been in that format.
Warner Home Video will stop releasing new titles on HD DVD at the end of May.
The announcement forced a swift reaction from the HD DVD Promotional Group.
The organisation cancelled all the meetings it had scheduled with journalists at high profile Consumer Electronics Show (CES) in Las Vegas and called off a press conference booked for Sunday evening.
In a statement the HD DVD group said: ""While Warner's decision is a setback for HD DVD, the consumer has benefited from HD DVD's commitment to quality and affordability - a bar that is critical for the mainstream success of any format.
"We believe widespread adoption of a next generation format will ultimately be determined by the consumer," it added.
Rich Greenfield at Pali Capital predicted that HD DVD would now "die a quick death" and predicted that would be good news for DVD sales.
"While we still expect overall consumer spending on DVDs to decline at least 3% in 2008, the risk of an even worse 2008 DVD environment has most likely been avoided by Warner's early 2008 decision," he said.
Toshiba, a founding partner of the HD DVD standard, denied that its format was dead, with Akiyo Ozaka, president of Toshiba America Consumer Products saying that HD DVD "has not lost".
"We were very disappointed with Warner Brothers' announcement," he admitted at CES.
But he added: "Sales of HD DVD were very good last year, especially in October to December."