ba2format.md

BA2 file description

I reverse-engineered the files a bit and took the information from here: https://github.com/digitalutopia1/BA2Lib/blob/master/BA2Lib/BA2.h

• BA2 file description
  • Header
  • File header
    • General file header
    • Texture header
      • Texture header: Chunks
  • Files
  • File name table

Header

Bytes	Type	Description
0x00 - 0x03	char[4]	Magic Number ("BTDX")
0x04 - 0x07	uint32	Version
0x08 - 0x0B	char[4]	Archive format (either "GNRL" or "DX10")
0x0C - 0x0F	uint32	Number of files
0x10 - 0x17	uint64	Offset to file name table

24 Bytes

File header

Each file has a header, starting at 0x18. The byte ranges in this table are relative to the start of a file header.

General file header

This header is used when the format is "GNRL".

Bytes	Type	Description
0x00 - 0x03	uint32	nameHash
0x04 - 0x07	char[4]	File extension (null terminated string)
0x08 - 0x0B	uint32	dirHash
0x0C - 0x0F	uint32	flags
0x10 - 0x17	uint64	offset
0x18 - 0x1B	uint32	Pack size
0x1C - 0x1F	uint32	Full size
0x20 - 0x23	uint32	align

36 Bytes

Texture header

This header is used when the format is "DX10".

Bytes	Type	Description
0x00 - 0x03	uint32	nameHash
0x04 - 0x07	char[4]	File extension (null terminated string)
0x08 - 0x0B	uint32	dirHash
0x0C	uint8	unk8
0x0D	uint8	Number of chunks
0x0E - 0x0F	uint16	chunkHdrLen
0x10 - 0x11	uint16	height
0x12 - 0x13	uint16	width
0x14	uint8	numMips
0x15	uint8	format
0x16-0x17	uint16	unk16

24 Bytes

Texture header: Chunks

Each texture header has one or more chunks. The byte ranges in this table are relative to the end of the texture header.

Bytes	Type	Description
0x00 - 0x07	uint64	offset
0x08 - 0x0B	uint32	Pack size
0x0C - 0x0F	uint32	Full size
0x10 - 0x11	uint16	startMip
0x12 - 0x13	uint16	endMip
0x14 - 0x17	uint32	align

24 Bytes

Files

The file contents.

File name table

Bytes	Type	Description
0x00	uint8	File name length
0x01	uint8	always 0
0x02 - (file name length)	char[n]	File name