{"id":3335,"date":"2011-05-23T22:50:02","date_gmt":"2011-05-24T05:50:02","guid":{"rendered":"http:\/\/multimedia.cx\/eggs\/?p=3335"},"modified":"2011-05-24T10:52:03","modified_gmt":"2011-05-24T17:52:03","slug":"dreamcast-archival","status":"publish","type":"post","link":"https:\/\/multimedia.cx\/eggs\/dreamcast-archival\/","title":{"rendered":"Dreamcast Archival"},"content":{"rendered":"

Console homebrew communities have always had a precarious relationship with console pirates. The same knowledge and skills useful for creating homebrew programs can usually be parlayed into ripping games and cajoling a console into honoring ripped copies. For this reason, the Dreamcast homebrew community tried hard to distance itself from pirates, rippers, and other unsavory characters.<\/p>\n


\n\"Lot<\/a>
\n<\/center><\/p>\n

Funny how times change. While I toed the same line while I was marginally a part of the community back in the day, now I think I’m performing a service for video game archivists and historians by openly publishing the same information. I know of at least one solution already. But I think it’s possible to do much better.<\/p>\n

Pre-existing Art<\/strong>
\nFamed Japanese game hacker BERO (FFmpeg contributors should recognize his name from a number of Dreamcast-related multimedia contributions including CRI ADX and SH-4 optimizations) crafted a program called dreamrip based on KOS’s precursor called libdream. This is the program I used to extract 4XM multimedia files<\/a> from Alone in the Dark: The New Nightmare<\/a>.<\/p>\n

Fun facts: The Sega Dreamcast used special optical discs called GD-ROMs. The GD stands for ‘GigaDisc’ which implied that they could hold roughly a gigabyte of data. How long do you think it takes to transfer that much data over a serial cable operating at 115,200 bits\/second (on the order of 11 Kbytes\/sec)? I seem to recall entire discs requiring on the order of 27-28 hours to archive.<\/p>\n

If only I possessed some expertise in data compression which might expedite this process.<\/em><\/p>\n

KallistiOS’ Unwitting Help<\/strong>
\nThe KallistiOS (KOS) console-oriented RTOS<\/a> provides all the software infrastructure necessary for archiving<\/strong> (that’s what we’ll call it in this post)<\/em> Dreamcast games. KOS exposes the optical disc’s filesystem via the \/cd<\/code> mount point on the VFS. From there, KOS provides functions for communicating with a host computer via ethernet (broadband adapter) or serial line (DC coder’s cable). To this end, KOS exposes another mount point on the VFS named \/pc<\/code> which allows direct access to the host PC’s filesystem.<\/p>\n

Thus, it’s pretty straightforward to use KOS to access the files (or raw sectors) of the Dreamcast disc and then send them over the communication line to the host PC. Simple.<\/p>\n

Compressing Before Transfer<\/strong>
\nRight away, I wonder about compiling 3 different compression libraries: libz, libbz2, and liblzma. The latter 2 are exceptionally CPU-intensive to compress. Then again, it doesn’t really matter how long the compressor takes to do its job as long as it can average better than 11 Kbytes\/sec on a 200MHz Hitachi SH-4 CPU. KOS can be set up in a preemptive threading mode which means it should be possible to read sectors and compress them while keeping the UART operating at full tilt.<\/p>\n

A 4th compression algorithm should be in play here as well: FLAC. Since some of these discs contain red book CD audio tracks that need archival, lossless audio compression should be useful.<\/p>\n

This post serves as a rough overview for possible future experiments. Readers might have further brainstorms.<\/p>\n","protected":false},"excerpt":{"rendered":"

Brainstorming better methods for archiving Dreamcast discs<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[221],"tags":[],"class_list":["post-3335","post","type-post","status-publish","format-standard","hentry","category-sega-dreamcast"],"aioseo_notices":[],"aioseo_head":"\n\t\t\n\t\n\t\n\t\n\t\n\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t\n\t\t