Convert ISO to CDI

Some legacy burning programs and Dreamcast-era workflows accept Padus DiscJuggler .cdi images but not a plain .iso. The conversion is only useful when the target explicitly requires CDI; it cannot add disc tracks, boot data, or sessions absent from the source.

What ISO represents

An ISO file is an optical-disc image commonly used for software installers, bootable media, data CDs, DVDs, and archival copies. The name usually refers to an ISO 9660-style data-disc image, although files called ISO can also contain UDF or other filesystem data.

ISO is widely handled by Windows and Linux mounting tools, installers, virtual drives, disc-burning software, and emulators. A typical single-file ISO represents one data track, usually as 2,048-byte user-data sectors; it does not inherently preserve CD audio, pregaps, multiple tracks, sessions, or raw sector details.

What CDI represents

CDI is the proprietary disc-image format of Padus DiscJuggler. Unlike a simple data-track ISO, a CDI can describe CD track modes, multiple tracks, sessions, and disc-writing information.

CDI is most often encountered in older Dreamcast homebrew, backup, and CD-R workflows. It is not a complete representation of an original Dreamcast GD-ROM: a retail GD-ROM dump is normally stored as GDI or CHD, while a CDI commonly represents a CD-R-compatible rebuild.

Convert a standard data ISO

Padus DiscJuggler is the appropriate desktop tool when a receiving application specifically needs a CDI container. It is discontinued, so use a legitimate copy on a compatible older Windows system or virtual machine; modern disc tools often read CDI but cannot create it.

1. Keep an unchanged copy of the source .iso on a local drive.
2. In DiscJuggler, use its image-copy or image-conversion workflow, select the ISO as the source image, and select DiscJuggler/CDI image as the output. Do not create a data-disc project and add the ISO as a file; that produces a disc containing file.iso, not a converted image.
3. Set the destination name, for example disc.cdi, and confirm that the detected source is a single data track before writing the image.
4. Open the completed CDI in DiscJuggler or test it in the intended program before removing the source ISO.

DiscJuggler menu names differ by release, but the required operation is conversion or copying from an image source to a CDI output, not file extraction and rebuilding.

For prepared Dreamcast CD images, the hobby utility cdi4dc can create a CDI from a correctly mastered Dreamcast ISO. Use the syntax documented by the specific release, usually shown by cdi4dc --help or in its bundled README. It is not a repair tool: the input must already have the required Dreamcast boot and track layout.

No reputable browser-based converter is a good choice for CDI creation. Web converters generally cannot validate DiscJuggler track metadata or Dreamcast boot structure, and uploading multi-hundred-megabyte disc images is slow and exposes potentially private or licensed data.

Dreamcast and compatibility limits

Renaming game.iso to game.cdi changes only the filename extension. A valid CDI must be written in DiscJuggler-compatible image format.

A converted one-track ISO remains a one-track data disc. Conversion cannot recreate CD-DA audio tracks, a second session, raw-sector data, copy-protection information, GD-ROM high-density data, or Dreamcast self-boot support missing from the source.

If the target is Dreamcast emulation, check the emulator's documented formats before converting. Current Flycast-based emulators commonly support GDI, CDI, and CHD; CHD is usually the better archival format when created from a complete, verified GDI or BIN/CUE dump because it preserves the represented track layout while reducing storage use.

For a physical Dreamcast CD-R, use a source prepared for CD-R and verify MIL-CD compatibility with the specific console. Many later Dreamcast units do not boot MIL-CD media. Start from GDI or BIN/CUE when the original disc has multiple tracks or audio; a standalone ISO lacks the layout needed to reconstruct them.