BCSAR

Overview

The BCSAR (CTR Sound ARchive) format is the 3DS's equivalent of the Wii's BRSAR format. They're not the same structures, though, but they do have the same purpose.

BCSAR are located in the RomFS, this is usually stored under "romfs:/sound/<name>.bcsar". This contains various audio formats, such as CSTM, CWSD, and CWAV.

BCSAR Header

OFFSET	SIZE	DESCRIPTION
0x0	0x4	MAGIC "CSAR"
0x4	0x2	Byte order mark (0xFEFF = Big Endian, 0xFFFE = Little Endian)
0x6	0x2	Length of BCSAR header
0x8	0x4	Version
0xC	0x4	Length of the entire BCSAR (starting from 0x0)
0x10	0x4	Amount of main partitions in the BCSAR [STRG + INFO + FILE = 0x03 (= 3)]
0x14	0x4	Partition header length [same for each partition? (ie STRG,INFO,and FILE header lengths)]
0x18	0x4	Location of STRG partition
0x1C	0x4	Length of STRG partition
0x20	0x4	Unknown (always 0x01200000?)
0x24	0x4	Location of INFO partition
0x28	0x4	Length of INFO partition
0x30	0x4	Location of main FILE partition
0x34	0x4	Length of main FILE partition
0x38	0x4	Reserved for 4th main partition location?
0x3C	0x4	Reserved for 4th main partition length?

Partitions

STRG

STRG contains the names of the audio files in the BCSAR.

Header

OFFSET	SIZE	DESCRIPTION
0x0	0x4	MAGIC "STRG"
0x4	0x4	Length of STRG partition (also in CSAR header)
0x8	0x4	String table type magic (always 0x2400)
0xC	0x4	This + 8 points to the string table (always 0x10)
0x10	0x4	String table lookup type magic (always 0x2401)
0x14	0x4	This + 8 points to the string lookup table
0x18	0x4	Filename count
0x1C	0xC * count	String offset table

String offset table entry

OFFSET	SIZE	DESCRIPTION
0x0	0x4	Type of the node (should be 0x1F01)
0x4	0x4	Offset to data from the end of the STRG header (sizeof 0x18)
0x8	0x4	Length of the data buffer (includes NUL terminator)

Then every filename is rawly setted. You can set up a dictionary that contains, using a simple counter, the size of every filename in order. Then, using the same type of counter, get the values of the size of the filename in a correct order.

String lookup table

Header

OFFSET	SIZE	DESCRIPTION
0x0	0x4	Index of the root entry
0x4	0x4	Entry count
0x8	0x14 * count	Lookup entry

Entry

OFFSET	SIZE	DESCRIPTION
0x0	0x2	Nonzero if contains data
0x2	0x2	Bit test condition (index = (this >> 3), bit = (~this & 7)), -1 if unused
0x4	0x4	Fail condition leaf index (-1 if unused)
0x8	0x4	Success condition leaf index (-1 if unused)
0xC	0x4	String lookup table index (-1 if unused)
0x10	0x3	3-byte Resource ID, Little Endian (-1 if unused)
0x13	0x1	Resource type (01=sound, 02=sound list, 03=sound bank, 04=sound player name?, 06=sound group, FF=unused)

INFO

INFO presumably contains information on the audio files? Possibly used to connect names from STRG to data from FILE?

For now I only know some information in the header for this partition, but I'm working on figuring the rest out.

Header

OFFSET	SIZE	DESCRIPTION
0x0	0x4	MAGIC "INFO"
0x4	0x4	Length of INFO partition (also in CSAR header)
0x8	0x4	Unknown magic 0x2100
0xC	0x4	This + 8 points to unknown
0x10	0x4	Unknown magic 0x2104
0x14	0x4	This + 8 points to unknown
0x18	0x4	Unknown magic 0x2101
0x1C	0x4	This + 8 points to unknown
0x20	0x4	Unknown magic 0x2103
0x24	0x4	This + 8 points to unknown
0x28	0x4	Unknown magic 0x2105
0x2C	0x4	This + 8 points to unknown
0x30	0x4	Unknown magic 0x2102
0x34	0x4	This + 8 points to unknown
0x38	0x4	Unknown magic 0x2106
0x3C	0x4	This + 8 points to unknown
0x40	0x4	Unknown magic 0x220B
0x44	0x4	This + 8 points to unknown

Blocks

Every offset in the header points to data similar to this:

• 4byte length
• length array of the below struct
  • u32 type
  • u32 offset relative to the address of the length field (beginning of the block)

The data the offset points to is dependent on the type of the above struct:

0x2200

OFFSET	SIZE	DESCRIPTION
0x0	0x4	Unknown
0x4	0x4	Sound player ID
0x8	0x4	Unknown
0xC	0x4	Type of the extended info
0x10	0x4	Offset to extended info *relative to the beginning of this struct*
0x14	???	Unknown...

0x2204

OFFSET	SIZE	DESCRIPTION
0x0	0x4	First Sound ID in this sequence set
0x4	0x4	Last Sound ID in this sequence set
0x8	0x4	Type of the extended info
0xC	0x4	Offset to extended info *relative to the beginning of this struct*
0x10	0x4	Type of the extended info
0x14	0x4	Offset to extended info *relative to the beginning of this struct*
0x18	0x4	Unknown
0x1C	0x4	Unknown

0x2206

OFFSET	SIZE	DESCRIPTION
0x0	0x4	Unknown
0x4	0x4	Type of the extended info
0x8	0x4	Offset to extended info *relative to the beginning of this struct*
0xC	0x4	Unknown
0x10	0x4	Unknown

FILE

FILE contains all of the audio data in the BCSAR.

OFFSET	SIZE	DESCRIPTION
0x0	0x4	MAGIC "FILE"
0x4	0x4	Length of FILE partition (also in CSAR header)

There isn't a whole lot else I can document about the FILE partition, since the data in it will most definitely vary depending on the game. (since audio is more than likely to change in each game)

There is no table in FILE so a different partition (presumably INFO) must be used to connect the data in FILE with the names from STRG.

After some more research, there are multiple FILE partitions, but only 1 of them is the 'main' FILE partition (it's the one you get from the BCSAR header). The 'main' FILE partition contains all of the other sub FILE partitions.

Tools

• vgmtoolbox's Advanced Cutter/Offset Finder tool can extract BCWAVs without filenames