.BCSTM File Extension
What is a BCSTM file?
A BCSTM file is an audio file used by various Nintendo 3DS games. It contains audio such as a sound effect or background music that is looped during gameplay.
BCSTM files must be transported to a PC before they can be opened by programs such as BrawlBox or foobar2000. BrawlBox can be used to convert BCSTM files to the more common .WAV file format. BCSTM files can also be created from WAV, .MP3, .OGG, or .FLAC files using Brawl Custom Song Maker.
The BCSTM file typically is never accessed by the average user. It is most likely only seen by users looking to modify 3DS gameplay and change the audio.