from hackmii.com

As you all know, I’ve been working on libdi (or the DVD Access library) for a while now. We had some problems getting it out to release because of the difficulties we encountered while writing the second part of this topic. The DVDX installer instead will install a small, hidden, channel on your Wii that allows you to read DVDs on an unmodified system. It is not an installer for a patched IOS. You may however need one, depending on your system.

Usage of this package is fairly simple. Run the installer.dol found in the package, follow the onscreen instructions, and you’re done.

Once you’ve done that, you can enjoy the splendor of mplayer. That what started out as a simple proof of concept has rapidly turned into a full-featured media player, under the nourishing hands of dhewg. The main aim of the mplayer project was to get DVDVideo going, but it also supports reading video files off the SD card. (Experimental).

A patch for Wii64, the N64 emulator for the Wii, will also be available shortly. This patch will allow you to read games off a DVD.

Download links:

mplayer
libdi

If you have a modchip, you also need patchmii, in addition to the DVDX stub installer.
patchmii_core

Note that libdi is meant for developers, as it is embedded into applications that use it. End-users only need to grab it to run installer.dol once.

Please note that DVD R (as opposed to DVD-R) discs will need to have their BookType set to DVD-ROM to work properly in Normal mode (if you have no modchip). PatchMii mode does not have this requirement, but requires a modchip.