The 3DS uses an SD Card for general storage of additional game data, music and photos taken with the 3DS.
(Most 3DS SD card data is stored under "/Nintendo 3DS/<ID0>/<ID1>", where ID0 is the first 0x10-bytes from a SHA256 hash.
- sdmc/DCIM - Photos/Videos and images downloaded with the Internet Browser. Video feature introduced with 3.0.0-5
- sdmc/Nintendo 3DS/Private
- sdmc/Nintendo 3DS/<ID0>/<ID1>/dbs
- sdmc/Nintendo 3DS/<ID0>/<ID1>/extdata
- sdmc/Nintendo 3DS/<ID0>/<ID1>/title
- sdmc/Nintendo 3DS/<ID0>/<ID1>/Nintendo DSiWare
(the 3D videos are in .avi format and the video frames use MJPG.)
Extdata
Additional game data is stored here:
- /Nintendo 3DS/<ID0>/<ID1>/extdata/00000000
See the extdata page for more extdata info and the extdataIDs list.
All "extra data" under extdata is encrypted. Extdata can't be decrypted with the xorpad fail used for old FLASH saves. All "extra data" files can't be copied to other 3DS SD cards, they are locked to the console.
Private
"Private" data is stored here:
/Nintendo 3DS/Private/<Title ID Low>/
00020400 - Nintendo 3DS Camera 00020500 - Nintendo 3DS Sound
"Private" data for 3DS Sound/Camera are cleartext.
Under the camera priv dir is phtcache.bin, this seems to list the pictures on SD card?
When you want to install and see pictures with 3DS,rename to 8 numbers.mpo and save it on /DCIM .
Under the sound priv dir is: voice/XX/*.m4a. Where XX is 01-10, with sound saved as .m4a.