RKG (File Format)

RKG is the format of Time Trial ghost data. This format is common between ghosts saved in the saved file, staff ghosts and ghosts stored on Time Trial servers. In a savefile all ghosts are saved in the rksys file.

The file consists of a header describing the settings of the ghost such as vehicle and character, as well as the driver information such as the Mii, controller type and drift type. The header also contains metadata such as finishing time of the ghost. The main contents of the file is then the sequence of controller inputs made by the player, which can be used to replay the ghost. This may be compressed or raw. Following the ghost input data is a CRC-32 which the game uses to verify the file has not corrupted.

If the game is perfectly deterministic, the same controller inputs should always yield the same finishing time. In practice however, Mario Kart Wii is not quite able to recreate the circumstances in which the ghost was recorded leading to the rare Wiggler Glitch. This causes the ghost to descynchronise from the original Time Trial, often failing to finish.

File Header

An RKG file begins with the 0x88 byte header.

Header of RKG file

Offset	Size	Description
0x00	4	"RKGD" in ASCII; Revolution Kart Ghost Data file identifier.
0x04	7 bits	Minutes field of finishing time.
0x04.7	7 bits	Seconds field of finishing time.
0x05.6	10 bits	Milliseconds field of finishing time.
0x07	6 bits	Track ID.
0x07.6	2 bits	Unknown. Probably padding.
0x08	6 bits	Vehicle ID used by the ghost.
0x08.6	6 bits	Character ID used by the ghost.
0x09.4	7 bits	Year that the ghost was set, stored relative to the year 2000.
0x0A.3	4 bits	Month that the ghost was set.
0x0A.7	5 bits	Day that the ghost was set.
0x0B.4	4 bits	Controller ID; 0 for Wii Wheel, 1 for Wiiremote + Nunchuck, 2 for Classic controller, 3 for GabeCube controller.
0x0C	4 bits	Unknown. Always 0?
0x0C.4	1 bit	Compressed flag; 1 for compressed, 0 for raw.
0x0C.5	2 bits	Unknown. Always 0?
0x0C.7	7 bits	Ghost type; 0x01 typical, 0x25 normal staff ghost, 0x26 expert staff ghost.
0x0D.6	1 bit	Drift type; 1 for automatic, 0 for manual.
0x0D.7	1 bit	Unknown. Probably padding.
0x0E	2	Input data length, measured when decompressed and without padding.
0x10	1	Lap count; total laps driven by ghost.
0x11	3 × 5	Lap split times. Stored in the same 7 bit, 7 bit, 10 bit format as the finish time at offset 0x4. Unused split times are set to 0.
0x20	0x14	Unknown, probably unused. The game attempts to store lap splits beyond the 5th here, but the internal data structures do not store that many splits, so RAM trash is stored instead when the lap count is greater than 5 (notably the finish time in the 6th split).
0x34	1	Country code or 0xff if sharing location disabled.
0x35	1	State code or 0xff if sharing location diabled.
0x36	2	Unknown. 0x0000 typically, 0xffff if sharing location disabled.
0x38	4	Unknown. 0x00000000 typically.
0x3C	0x4A	Driver's Mii Data.
0x86	2	CRC16-CCITT of Mii.
0x88	End of this header; start of data

Controller Input Data

The header is then followed by the input data. For compressed input data, the first 4 bytes are the length of the compressed data, followed by YAZ1 compressed data (including the YAZ1 header). The comrpessed data is always padded with zeros to a multiple of 4 bytes in length. Compressed data is used in the online rankings and in staff ghosts, uncompressed data is used in the save file. In a compressed ghost the compressed data (including YAZ1 header) must be less than or equal to 0x2774 bytes in length. For both compressed and uncompressed ghosts, the uncompressed input data must also be less than 0x2774 in length. In uncompressed files the input data is padded to exactly 0x2774 bytes in length. The length of the input data in the header always refers to the input data without padding.

CRC

Following the data is a CRC-32 of the file up to that point. For compressed files, this is a CRC of the compressed data not the decompressed data.