BCSAR

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Overview[edit]

The BCSAR (Binary 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, CSEQ, and CWAV.

BCSAR Header[edit]

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 STRG partition reference ID? (Always 0x2000)
0x18 0x4 Location of STRG partition
0x1C 0x4 Length of STRG partition
0x20 0x4 INFO partition reference ID? (Always 0x2001)
0x24 0x4 Location of INFO partition
0x28 0x4 Length of INFO partition
0x2C 0x4 Main FILE partition reference ID? (Always 0x2002)
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[edit]

STRG[edit]

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

Header[edit]

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[edit]

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[edit]

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

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[edit]

OFFSET SIZE DESCRIPTION
0x0 0x4 MAGIC "INFO"
0x4 0x4 Length of INFO partition (also in CSAR header)
0x8 0x4 Audio Table Reference ID (0x2100)
0xC 0x4 This + 8 points to the Audio Table
0x10 0x4 Set Table Reference ID (0x2104)
0x14 0x4 This + 8 points to the Set Table
0x18 0x4 Bank Table Reference ID (0x2101)
0x1C 0x4 This + 8 points to the Bank Table
0x20 0x4 WAV Archive Table Reference ID (0x2103)
0x24 0x4 This + 8 points to the WAV Archive Table
0x28 0x4 Group Table Reference ID (0x2105)
0x2C 0x4 This + 8 points to the Group Table
0x30 0x4 Player Table Reference ID (0x2102)
0x34 0x4 This + 8 points to Player Table
0x38 0x4 FILE Table Reference ID (0x2106)
0x3C 0x4 This + 8 points to the FILE Table
0x40 0x4 Unknown Table Reference ID (0x220B)
0x44 0x4 This + 8 points to unknown

Blocks[edit]

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[edit]
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[edit]
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[edit]
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
Table IDs[edit]
ID NAME
0x2200 Audio Table
0x2204 Set Table
0x2206 Bank Table
0x2207 WAV Archive Table
0x2208 Group Table
0x2208 Player Table
0x220A FILE Table

FILE[edit]

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[edit]

  • vgmtoolbox's Advanced Cutter/Offset Finder tool can extract BCWAVs without filenames
  • 3DSUSoundArchiveTool reference implementation of CSAR extraction