Chrono Cross File Structure

Chrono Cross, released late in the PlayStation's life, was subject to clever obfuscation by Square. Obfuscation—the art of hiding data—means at the simplest level that, if you put Chrono Cross in your hard drive, you can't browse directories and view individual assets, like character models and textures. Instead, the game disc is compiled as a unified whole with an index file at the beginning which the PlayStation / Chrono Cross read to find files and operate. Halkun of QHIMM.com explains by narrating Square's probable process for creating Final Fantasy VII.

1. All uncompressed data was preloaded in a particular data structure (like how it was originally).
2. Compiling - The executables are built and the compiled structure's length is recorded. These can be dynamic; my theory is that there's no sector data here.
3. PSX data creation - The ANI, TIM, RSD, HRC, and all the other PSX data is created from source assets.
4. Compression - Pass 1 - GZIP - All the files that are not sector critical are GZipped. Compressed and uncompressed lengths are recorded.
5. Compression - Pass 2 - LZS - All the files that are going to be sector critical are compressed in LZS and their lengths recorded.
6. Concentration - Headers are made for all the files that need to be stuck together. They are then done so. Sector locations are kept blank.
7. File finalization - All files are manifested in their final form, minus sector information.
8. Cool preburn - A disk image is created on a blank hard drive. Blank indexes are written first. Then, when a file is copied to this image, sector information is written in the files that need it, and recorded in the master index. Each file gets this treatment.
9. Burn - The disk is mastered.

The most location-important files accumulate at the beginning of the data, and the index is usually first (or perhaps last on a disc). In 2002, Terminus Traduction (specifically, Yazoo, Nemesis, and Manz) successfully audited Chrono Cross and wrote a set of utilities for extracting its data.

Debug Mode

With the room modifier code 8007E6E8 000E enabled, ZeaLitY restored a savestate in ePSXe immediately following the defeat of the Time Devourer on a new game plus in disc one. The game shifted to the Hydra Marshes, but strangely, this savestate (and only this savestate) booted the location with a debug mode menu active. Thanks to this completely accidental discovery, the game's debug mode is being mapped. Here is the Time Devourer battle savestate (to be used with that room modifier code):

Savestate Image

Here is a savestate with the debug mode enabled:

Savestate Image

Menu Layout

Adjust Screen's RGB
	Start Changes
	   "Mode: 00
		R: 0
		G: 0
		B: 0"
		Input Red: 000

		Next
		Input Red again!
			(If >255) "Max is 255, stupid!"
		~
		Input Green again!
			(If >255) "Max is 255, silly!"
		~
		Input Blue again!
			(If >255) "Max is 255, dope!"
		~
		Select Mode: 000
			(If >3) "Range is 0 to 3!"
		End
		Select Mode again!
	Default
	Return
	Quit
Adjust Underwater RGB
	Start Changes
	   "Mode: 00
		R: 0
		G: 0
		B: 0"
		Input Red: 000

		Next
		Input Red again!
			(If >255) "Max is 255, stupid!"
		~
		Input Green again!
			(If >255) "Max is 255, silly!"
		~
		Input Blue again!
			(If >255) "Max is 255, dope!"
	Default
	Return
	Quit
Adjust Chara.'s RGB
	Start Changes
	   "Mode: 00
		R: 0
		G: 0
		B: 0"
		Input Red: 000

		Next
		Input Red again!
			(If >255) "Max is 255, stupid!"
		~
		Input Green again!
			(If >255) "Max is 255, silly!"
		~
		Input Blue again!
			(If >255) "Max is 255, dope!"
	Default
	Return
	Quit
Adjust Chara.'s rot
	Start Changes
	   "Current Values...
		X:0
		Z:0
		Y:0"
		Set rotx = 0000
			(If >4096) "Max is 4096!"
		~
		Next
		Set rotx again
		~
		Set rotz again
		~
		Set roty again
	Default
	Return
	Quit
Adjust Chara.'s scale
   "Scale what?"
	All
		00/10
			(If 0 "A number other than 0!")
	X
	Z
	Y
	Cancel
Set Rect.
	Rect. Size
		rectsizeX 0000
		~
		rectsizeZ 0000
	Go away!
Return
	YOU'RE AT MAP NO. 9!
		Map Jump
		This Map
		Before Jump
		Next Map
		Previous Map
		Planners' Rooms
		Special
		Exit Menu/Return
Quit

From: Games
From: Modification

Thanks to halkun for explanation of Square practices