Dreamcast: Difference between revisions

Revision as of 19:16, 28 October 2005

Revision as of 20:43, 28 October 2005

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The optical drive in the Dreamcast works in CAV ([[Constant Angular Velocity]]) mode, which spins the disc at a constant speed regardless of the laser's position. This is different from a normal CD-ROM drive, which spins the disc in CLV ([[Constant Linear Velocity]]) mode, where the disc spins progressively slower as the laser moves further away from the disc's center. CLV exists because the diameter of the data ring on the disc becomes wider as the disc progresses, and the data becomes less densely packed. Therefore, to receive the data at a constant speed, the drive must slow the disc down as the data ring enlarges. But since the Dreamcast works in CAV mode, occasionally, when there was space to spare on the CD-R, Dreamcast game pirates would fill the disk image on which the game was distibuted with empty space at the beginning, so the disk image size would be about 700 MB. Therefore, when burned, the data would be pushed further outward on the disc, mimicking the layout of an actual GD-ROM. This practice is called "dummying." They do this because CD-Rs are written in CLV mode, and the Dreamcast will not read data from them very fast if the data is close to the inner edge. Therefore, the data should, optimally, be as close to the outer edge of the disk as possible, for the fastest loading times. Some pirated games do not have this trait, presumably because they need the empty space, and therefore have longer loading times and choppy music and video (because the data cannot be loaded fast enough).

The curious thing about how pirates managed to copy games stored on a GD-ROM, which can supposedly hold about 1.2 gigabytes of data, to a CD-R, which commonly holds 700 megabytes of data (though 870 megabyte discs exist, butthey are extremely uncommon) was that many games simply did not use the maximum capacity of a GD-ROM, and therefore fit on a standard CD-R with no modification. Games that did take advantage of the GD-ROM's extra capacity required some tinkering from hackers; the most common method was to [[encode|downgrade]] the video and audio portions of the disc to a lower [[bitrate]], so they would take up less space. Although this method is usually successful, a few games, most noticebly ''[[Shenmue II]]'' and ''[[Sonic Adventure]]'', are missing sound and sometimes video on pirated versions. This may be due to the process of "ripping", different from the alternate definition of copying the contents of a CD to a hard drive. "Ripping" in the Dreamcast piracy context means to completely remove some parts of game audio and video, since they are simply too large to downgrade with any success.

The Dreamcast continues to have a modest [[Hack (technology slang)|hacking]] enthusiast community. The availability of [[Windows CE]] [[software development kit]]s on the Internet, as well as ports of [[Linux]] [http://linuxdc.net/] and [[NetBSD]]/Dreamcast [http://www.netbsd.org/Ports/dreamcast/] operating systems, gave programmers a selection of familiar development tools to work with. A homebrew minimal operating system named [[KallistiOS]] offers good hardware support (though does not provide [[computer multitasking|multitasking]], which is generally unimportant for games anyway). Many emulators and other tools such as [[MP3]] and [[DivX]] players and image viewers have been ported to or written for the console, taking advantage of the relative ease with, which a home user can burn a CD which is bootable by an unmodified Dreamcast.