MS explains how HD-DVD works
More gruelling than Gears?
Xbox 360's HD-DVD player took more work than you might imagine, with the software-based player pushing the system harder than any game besides Gears of War.
That's according to software engineer Shaheen Gandhi, who's been explaining the sort of work that went into the console's latest peripheral (due out this month) on the programming side.
"All six of Xbox 360's hardware threads are hard at work while playing back an HD-DVD," Shaheen writes on Microsoft's developer network blogs. "At the moment, the player software pushes Xbox 360 harder than any other (save, perhaps, Gears of War during some particularly busy parts of the game)."
But how does it work? "The Xbox 360 HD DVD Player, for the most part, is an entirely software based implementation," we're told.
"Other players on the market have specialized chips (called DSPs) that decode things like H.264, MPEG, VC1, DTS, Dolby Digital, and other codecs. Much like how backwards compatibility for Xbox 1 works on Xbox 360, the heavy parts of HD DVD are all done on Xbox 360's triple-core CPU."
"If DVD is an audio/video pipeline with some navigation data (go to the menu, start playing, etc.), HD-DVD can be considered a runtime environment where audio/video playback is just one major feature," the engineer adds.
But as well as video and audio codecs, the 360 also needs to worry about the HD-DVD runtime engine, the graphics device interface, the media foundation framework borrowed from Windows Vista and encryption - in other words, a lot of work was required, particularly to get code written for Windows PCs to function optimally on Xbox 360.
There are also some quirks to bear in mind: "Unlike DVD, where typical players pass the audio data from the disc through to your receiver, HD-DVD requires that players mix sounds from menus and such in with the audio being played for the movie," the explanation goes.
"The 360 player software decodes all the above codecs in software, mixes anything that needs to go together, re-encodes it into Dolby Digital and then sends that to your receiver. So, don't be alarmed when your receiver still says 'Dolby Digital' even if you've selected DTS in the menus."
The Xbox 360 HD-DVD add-on, designed exclusively for movies, is due out this month priced EUR 199.99 / GBP 129.99.