DVDX is a homebrew application that installs a hidden "channel" which can be used by other homebrew applications to access home burned and factory pressed DVD content without the need for a modchip. This does not modify any IOS in any way, making it very safe.
Installation is simple - just run the DVDX stub installer (Pre-Oct 23 update for system menu 3.3 and older, or Post-Oct 23 update for system menu 3.4)). If you have a modchip, you may need to install PatchMii core before installing DVDX. Then, when asked for the installation mode, select PatchMii. Please note that the post-Oct 23 version does not have the PatchMii and advanced modes. That means that some modchip users cannot install it.
Q: What type of DVD should I use?
A: Pressed DVD-ROM video discs of course work. For recordables, DVD-R media is recommended. However, DVDX has been confirmed working with various DVD media, including DVD+R/RW and DVD-R/RW discs. Particular brands (lower quality discs) may be problematic, and different Wii drives have different levels of compatibility. Please note that DVD+R/RW 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.
Q: Why does my Wii not read my DVDs?
A: Be sure that you properly install DVDX, and that the application that you are trying to use supports it. If you are using a burned disc, make sure it is burned correctly. Try re-burning the DVD on a DVD-R if it is not already. If you are using one of Tantric's apps (the GX emulators), try using an older version, as many times in the past he has accidently broken DVD support.
Q: Could I put different things on other than a certain app (for example, DVD-SNES9xGX-ROMS-Earthbound. DVD-VBAGX-ROMS-WarioWare Twisted ?
Homebrew developers looking to add DVD support to their applications will need to use libdi, which has been added to libogc. libdi requires the DVDX stub.