This is a brief but usuable wrapper for SDL2_Mixer.

The following functions are currently available to the users

• (sdl2-mixer:linked-version): Returns the version number for SDL Mixer 2. Calls Mix_Linked_Version
• (sdl2-mixer:init &rest formats): Initialize the SDL mixer specifying the formats you wish to use. Must be one of these values or a combination thereof :ogg, :wave, :mod, :mp3. Calls Mix_Init.
• (sdl2-mixer:quit) Cleans up SDL Mixer. Calls Mix_Quit.
• (sdl2-mixer:open-audio frequency format channels chunksize): Initialize the mixer specifiying the output sample format, number of output channels (1 mono or 2 for stereo), and bytes used per output sample. format must be one of the following values, :u8, :s8, :u16lsb, :s16lsb, :u16msb, :s16msb, :u16, :s16, :u16sys, :s16sys. Calls Mix_OpenAudio
• (sdl2-mixer:close-audio): Closes the mixer. Calls Mix_CloseAudio
• (sdl2-mixer:query-format): Gets the output format in use by the opened audio device. Calls Mix_QuerySpec
• (sdl2-mixer:load-wav sample-file-name): Loads the sample specified by the sample-file-name. Returns a mix-chunk. sdl2-mixer must be initialized and open-audio must be called prior to. Calls Mix_LoadWav_RW. Please refer to the source comments for more details if you are interested in why it calls Mix_LoadWav_RW as opposed to Mix_LoadWav
• (sdl2-mixer:allocate-channels number-of-channels): Set the number of channels to be mixed. Opening too many channels may result in a segfault. This can be called at any time even while samples are playing. Passing a number lower than previous calls will close unused channels. It returns the number of channels allocated. NOTE: Channels are 0 indexed! Calls Mix_AllocateChannels
• (sdl2-mixer:volume channel volume): Set the volume on a given channel, pass -1 to set the volume for all channels. The volume may range from 0 to 128. Passing in a number higher than the maximum will automatically set it to the maximum while passing in a negatiev will automatically set it to 0. Returns the current volume of the channel. NOTE: Channels are 0 indexed! Calls Mix_Volume
• (sdl2-mixer:play-channel channel mix-chunk loops): Plays the mix-chunk (sound effect) loops+1 times on a given channel. Passing -1 for the channel will play it on the first unreserved channel. Returns the channel the sample is played on. NOTE: Channels are 0 indexed! Calls Mix_PlayChannel
• (sdl2-mixer:halt-channel) Halt the channel or pass -1 to halt all channels. Always returns 0. NOTE: Channels are 0 indexed! Calls Mix_HaltChannel
• (sdl2-mixer:free-chunk chunk) Free memory used for a given chunk. Do not free the chunk while it's being called. CallsMix_FreeChunk
• (sdl2-mixer:load-music music-file-name) Loads music from a file. Returns a mix-music object. Calls Mix_LoadMUS
• (sdl2-mixer:free-music mix-music-object) Free memory used by a music object. Calls Mix_FreeMusic
• (sdl2-mixer:play-music mix-music-object loops) Play music object looping the number of times specified by the loops argument. -1 plays indefinitely. Calls Mix_PlayMusic
• (sdl2-mixer:halt-music) Halts all playing music. Calls Mix_HaltMusic
• (sdl2-mixer:volume-music volume) Sets the music volume to the volume specified. Calls Mix_VolumeMusic

A simple example program has been provided. Ogg support is required to run it however. Press the space bar to play the sound effect/song, the up directional key to increase the volume by 20 and the down directional key to decrease the volume by 20. The current volume is displayed in standard-output.

If you cannot load libSDL2_mixer, please ensure that you have SDL_mixer 2.0, installed and not just 1.2. If you receive errors concerning unknown file types, please ensure that libSDL2_mixer is linked against the appropriate sound library, e.g. libVorbis for ogg support. As of writing (05-31-2015) the SDL_mixer 2.0 provided by brew on OSX does not link libVorbis correctly, please build it from source.

If you are sure all of this is correct, and it still will not load, please file an issue and specify:

• Your platform and architecture
• Your lisp
• The absolute path to your installed .so, .dll, or the appropriate OSX framework