Simplify the following text for a Grade 8 native English-speaking person.
Original: Blu-ray Disc is a high-density optical disc format similar to DVD . Blu-ray is the type of disc used for Playstation 3 games and for playing high-definition ( HD ) movies .
Simplified: On January 4 , 2008 , a day before CES 2008 , Warner Bros. ( the only major studio still releasing movies in both HD DVD and Blu-ray Disc format ) announced that it would release only in Blu-ray Disc after May 2008 .