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 and store various audio formats, such as CSTM, CWSD, and CWAV.

BCSAR Header

OFFSET	SIZE	DESCRIPTION
0x0	0x4	MAGIC "CSAR"
0x4	0x2	Byte order mark?
0x6	0x1	Length of BCSAR header
0xB	0x1	Version?
0xC	0x4	Length of the entire BCSAR (starting from 0x0)
0x10	0x1	Amount of main partitions in the BCSAR? [STRG + INFO + FILE = 0x03 (= 3)]
0x15	0x1	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.

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

OFFSET	SIZE	DESCRIPTION
0x0	0x4	MAGIC "STRG"
0x4	0x4	Length of STRG partition (also in CSAR header)
0x18	0x4	Count of audio names (since each file should have a name you could also say this is essentially a file count)

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.

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

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.