Category Archives: Sega Dreamcast

Dreamcast Operating Systems

The Sega Dreamcast was famously emblazoned with a logo proudly announcing that it was compatible with Windows CE:



It’s quite confusing. The console certainly doesn’t boot into some version of Windows to launch games. Apparently, there was a special version of CE developed for the DC and game companies had the option to leverage it. I do recall that some game startup screens would similarly advertise Windows CE.

Once the homebrew community got ahold of the device, the sky was the limit. I think NetBSD was the first alternative OS to support the Dreamcast. Meanwhile, I have recollections of DC Linux and LinuxDC projects along with more generic Linux-SH and SH-Linux projects.



DC Evolution hosts a disc image available for download with an unofficial version of DC Linux, assembled by one Adrian O’Grady. I figured out how to burn the disc (burning DC discs is a blog post of its own) and got it working in the console.

It’s possible to log in directly via the physical keyboard or through a serial terminal provided that you have a coder’s cable. That reminds me– my local Fry’s had a selection of USB-to-serial cables. I think this is another area that is sufficiently commoditized that just about any cable ought to work with Linux out of the box. Or maybe I’m just extrapolating from the experience of having the cheapest cable in the selection (made by io connect) plug and play with Linux.



Look! No messy converter box in the middle as in the Belkin case. The reason I went with this cable is that the packaging claimed it was capable of up to 500 Kbits/sec. Most of the cables advertised a max of 115200 bps. I distinctly recall being able to use the DC coder’s cable at 230400 bps a long time ago. Alas, 115200 seems to be the speed limit, even with this new USB cable.

Anyway, the distribution is based on a 2.4.5 kernel circa 2001. I tried to make PPP work over the serial cable but the kernel doesn’t have support. If you’re interested, here is some basic information about the machine from Linux’s perspective, gleaned from some simple commands. This helps remind us of a simpler time when Linux was able to run comfortably on a computer with 16 MB of RAM.

Debian GNU/Linux testing/unstable dreamcast ttsc/1

dreamcast login: root
Linux dreamcast 2.4.5 #27 Thu May 31 07:06:51 JST 2001 sh4 unknown

Most of the programs included with the Debian GNU/Linux system are
freely redistributable; the exact distribution terms for each program
are described in the individual files in /usr/share/doc/*/copyright

Debian GNU/Linux comes with ABSOLUTELY NO WARRANTY, to the extent
permitted by applicable law.

dreamcast:~# uname -a
Linux dreamcast 2.4.5 #27 Thu May 31 07:06:51 JST 2001 sh4 unknown

dreamcast:~# cat /proc/cpuinfo  Continue reading →

Dreamcast Anniversary Programming

This day last year saw a lot of nostalgia posts on the internet regarding the Sega Dreamcast, launched 10 years prior to that day (on 9/9/99). Regrettably, none of the retrospectives that I read really seemed to mention the homebrew potential, which is the aspect that interested me. On the occasion of the DC’s 11th anniversary, I wanted to remind myself how to build something for the unit and do so using modern equipment and build tools.



Background
Like many other programmers, I initially gained interest in programming because I desired to program video games. Not content to just plunk out games on a PC, I always had a deep, abiding ambition to program actual video game hardware. That is, I wanted to program a purpose-built video game console. The Sega Dreamcast might be the most ideal candidate to ever emerge for that task. All that was required to run your own software on the unit was the console, a PC, some free software tools, and a special connectivity measure.

The Equipment
Here is the hardware required (ideally) to build software for the DC:

  • The console itself (I happen to have 3 of them laying around, as pictured above)
  • Some peripherals: Such as the basic DC controller, the DC keyboard (flagship title: Typing of the Dead), and the visual memory unit (VMU)


  • VGA box: The DC supported 480p gaming via a device that allowed you to connect the console straight to a VGA monitor via 15-pin D-sub. Not required for development, but very useful. I happen to have 3 of them from different third parties:


  • Finally, the connectivity measure for hooking the DC to the PC.
    Continue reading →

Sofdec Support

FFmpeg now includes support for the Sofdec middleware format thanks to Aurel Jacobs and Mans Rullgard, as well as everyone who has made FFmpeg’s MPEG video decoding what it is today. Sonic the Hedgehog salutes you:



Sonic Adventure 2: Battle
Sonic Adventure 2: Battle

Sofdec is a multimedia middleware format that was used heavily on the Sega Dreamcast. Indeed, if you booted a DC game, there might have been a 50/50 chance that you would see Sofdec’s technology insignias among the many obligatory corporate logos. Sofdec still survives to this day and is seen on various GameCube games (often developed by Sega’s subsidiary houses). It probably runs on all the other consoles as well. In fact, I see that MobyGames maintains a game group for CRI-using games.

The thing about Sofdec files is that they are fundamentally MPEG files with MPEG-1 video. The only thing special about them is that they are packaged with a custom ADPCM format called CRI ADX. I checked out the new FFmpeg support with files from a variety of games. One of the biggest problems is blocky output. On files from certain games (for example, F-Zero GX, Resident Evil 4, and Starfox Assault), it almost appears that only DC data is being decoded. FFmpeg does not report any decoding problems. The result is something like this:


Blocky GameCube logo

I am pretty sure that the above is supposed to be the official GameCube logo, which looks like this:


Nintendo GameCube Logo

There are also a few videos from Resident Evil: Code Veronica X on the GameCube that display as a square 320×320 frame, which is not correct:


Resident Evil: Code Veronica X-- Claire Redfield, square aspect ratio

I wonder if aspect ratio information is stored inside this file format, or if perhaps the data is in some other place in the game’s data. Not all of the videos in the game are like this, though.

Many new samples are available in the usual place.

New Filesystem Ideas

I really like FUSE, the filesystem in userspace that facilitated the creation of gcfuse. I think the killer app for FUSE is sshfs. It’s a minor miracle that if you have an SSH server running on a machine you can use sshfs to mount a filesystem from another machine. Authentication, encryption, all taken care of. None of that NFS or Samba configuration hassle.

I started wondering what else I might be able to use FUSE for. There is the small issue of Sega Dreamcast disc images. These games contain a lot of multimedia encoded with Sofdec’s middleware tools. For the most part, these discs use an ISO-9660-like filesystem that’s just a little different and doesn’t operate with Linux’s ISO-9660 module. Perhaps a FUSE/ISO-9660 module that can also handle the modified Dreamcast variant? Actually, I see that the big FUSE app directory lists an app appropriately named fuseiso which can load an ISO-9660 filesystem. It might be worth a look.

Thinking bigger, what about a FUSE module that mounts a DVD and presents it in some interesting manner? For starters, it will transparently decrypt the data. Then, present the contents of the DVD as a series of chapters or tracks or menu options. Since a DVD is not necessarily a strict hierarchy, perhaps organize the different viewing options in different directories. Or a /proc-like special filesystem that allows tinkering with the audio and subtitle options. It’s late and I’m just tossing out ideas here. Feel free to jump in.