GDI format

Sega Dreamcast GD-ROM images are most commonly using the GDI file format.

Example GDI taken from Crazy Taxi:

3
1 0 4 2352 track01.bin 0
2 600 0 2352 track02.raw 0
3 45000 4 2352 track03.bin 0

The first line is the total number of tracks in the image. Each subsequent line describes each track of the disc. All GD-ROMs are at least 3 tracks. The format of each line is as follows:

[Track Number] [Beginning LBA] [Track Type] [Sector Size] [Filename] [Offset]

The track type is always 4 for data tracks, and 0 for audio tracks. Sector size is 2352 for raw data tracks containing error correction, as well as audio tracks. 2048 is used for tracks with error correction stripped. The offset field should always be 0.

Tracks 1 and 2 are the standard density CD-ROM tracks accessible by standard drives. The first track may contain goodies for the owner, like wallpapers or screensavers. The second is an audio track usually warning the user not to play the disc in an audio CD player. The high density region starts with track 3. Track 3 always starts at an LBA of 45000. On games with no audio tracks, there will only be 3 tracks total. On games with audio tracks, track 3 will be the ISO9660 header, followed by all of the data tracks, and finally the last track will contain the actual file data pointed to by the ISO9660 filesystem within track 3.

Example GDI taken from Quake III Arena:

20
1 0 4 2352 track01.bin 0
2 756 0 2352 track02.raw 0
3 45000 4 2352 track03.bin 0
4 240811 0 2352 track04.raw 0
5 253507 0 2352 track05.raw 0
6 265334 0 2352 track06.raw 0
7  281311 0 2352 track07.raw 0
8 296397 0 2352 track08.raw 0
9 310270 0 2352 track09.raw 0
10 324436 0 2352 track10.raw 0
11 339323 0 2352 track11.raw 0
12 355185 0 2352 track12.raw 0
13 368487 0 2352 track13.raw 0
14 382523 0 2352 track14.raw 0
15 392248 0 2352 track15.raw 0
16 402684 0 2352 track16.raw 0
17 412416 0 2352 track17.raw 0
18 423159 0 2352 track18.raw 0
19 430167 0 2352 track19.raw 0
20 437360 4 2352 track20.bin 0

In this case, the disc contains 20 tracks. Track 1 is the CD-ROM data track, track 2 is the audio warning track, track 3 is a high density ISO9660 filesystem, tracks 4 through 19 are audio tracks used within the game, and track 20 contains actual file data described by the filesystem in track 3.

The last track is always a data track, and the game's binary is always the last file on the disc.