GDI/CDI formats

GDI/CDI Formats

Dreamcast disc images come in two common formats, and knowing the difference helps you build a library that loads reliably and looks its best.

GDI

GDI images preserve the original GD-ROM track layout faithfully. A GDI is typically a small text file plus separate track data, and because it mirrors the source disc closely, it tends to be the most accurate and compatible option for an ODE. If you want the truest reproduction of a game, GDI is the format to prefer.

CDI

CDI packs an image into a single convenient file. This makes CDI handy for distribution and for burning to CD-R via the MIL-CD method. The trade-off is that converting to CDI can be lossy, sometimes trimming content to fit, so a CDI may not always match the original perfectly.

Which to use

• For an ODE library, prefer GDI for accuracy.
• For burning to CD-R, CDI is often the practical choice.
• Much homebrew is distributed ready-made in one of these formats.

With your images in the right format, see SD card preparation and Loading games to put them to use.