As Apple rolls out the public preview of QuickTime 6 today, Microsoft continues work on its next-generation digital media player, code-named Corona. Microsoft has yet to commit to supporting MPEG-4 in Corona, as Apple has done with QuickTime 6, instead opting to use its own codecs. Microsoft also isn’t planning a Mac release of Corona at this point. “Our focus right now for the Corona time frame is Windows XP and other versions of Windows, Jonathan Usher, director of the Windows Digital Media Division at Microsoft told c|net.