Advanced Sound Library

From GameBrew - a wiki dedicated to Video Game Homebrew.

Advanced Sound Library

The Advanced Sound Library (ASlib) is a new sound library for the NDS.


  • MP3 engine
  • Audio engine

User guide

MP3 engine:

mp3 is decoded on the arm7, so use nearly no CPU time on the arm9
stereo & surround modes available (surround works even for mono mp3s)
up to 44Khz/stereo/96Kbps, though I recommend using 32Khz/stereo/80Kbps max, which is enough for the DS and works great with up to +25%/-100% pitching
support real-time pitching (changing the playing speed of the mp3)
support real-time volume and panning change
the mp3 can be paused and restarted
the mp3 can be set to loop automatically
support playing from RAM and streaming from FAT or EFS
you can disable the mp3 engine if you want, to get 2 more channels

Audio engine:

can use the whole 16 DS channel or only the first half (so you can use an external mod player, for example)
support standard or surround/fx mode (16 channels in standard mode (-2 if mp3), 8 in surround/fx mode (-1 if mp3))
simple sound playing using a priority system: if no channel is available, stop a sound that has less priority than the new one to play it, or skip it if all sounds have more priority.
possibility to reserve a particular channel so it won’t be used in the channel pool by the priority playing system. You can then manage the reserved sound channels manually.
surround or pseudo-reverb can be activated per sound (works great with mono sounds)
support real-time volume, panning and pitch modifications for each sound
support sound looping

The lib comes with a template and a example of what you can do with it.

Known issues

This library build using a way old DKP version: devkitPro r21 and libnds 20071023, newer version may not compile it because the IPC system was removed.


IPC sound system and streaming is based on cold_as_ice streaming example.

Audio stream filling / mp3 decoding based on ThomasS mp3 decoding example.

ASM stereo desinterleave function was made by Thoduv.