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 | 0x4 | Length of BCSAR header |
| 0xA | 0x2 | 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) |
| 0x18 | 0x4 | Count of audio names (since each file should have a name you could also say this is essentially a file count) |
Then for each name:
| OFFSET | SIZE | DESCRIPTION |
|---|---|---|
| 0x0 | 0x4 | Type of the file...? |
| 0x4 | 0x4 | Offset of the filename |
| 0x8 | 0x4 | Size of the filename |
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.