This egg provides a schemely wrapper around the libsdl-mixer library. The original library documentation can be found at the libsdl website.
sdl-mixer headers and libraries must be present. Versions prior to 0.6 also needed the SDL egg.
Opening and closing the audio device
- open-audio #!key sampling-rate sample-format channels chunk-sizeprocedure
Opens the audio device and initialises libsdl-mixer. Needs to be called at least once. It will close and reopen the device if it has been opened before.
The defaults for the keyword arguments are:
Note: The sdl-init and mix-init procedures will be called only once.
Closes the audio device and shuts down the mixer library. No procedure should access libsdl-mixer or sdl audio procedures after calling close-audio.
- load-sample filenameprocedure
Loads the sample from filename. Raises an exception if the sample cannot be loaded or the sample format is not supported by sdl-mixer. Returns a pointer representing the sample which can be used by play-sample.
- play-sample sample #!key channel repeat fadein durationprocedure
Takes a sample pointer, which has been loaded with load-sample and plays it on channel. By default this is the next available channel. The sample will be repeated repeat times, which by default is #f, the sample will be played once only.
fadein and duration control how long the sample is played and the time that is used to fade in the sample to the channel. Both values represent milliseconds.
- pause-channel #!optional channelprocedure
- resume-channel #!optional channelprocedure
Will pause or resume all channels or the given channel.
- halt-channel #!optional channel #!key fadeoutprocedure
Halts channel channel or all channels by default. If the fadeout parameter is set, this will be used to fade out the channel(s). fadeout is given in milliseconds.
- channel-finished procprocedure
Sets a handler to be called when a channel has finished playing. The proc is expected to take an argument for the channel number that has finished.
- channel-playing? channelprocedure
- channel-paused? channelprocedure
Predicates indicating whether channel is in playing or paused state.
- load-music filenameprocedure
Loads a file filename and returns a music object. A condition is raised if the format of the file is not supported by libsdl-mixer. It returns a pointer representing the music which can be used by play-music.
- play-music music #!key repeat fadein volumeprocedure
Plays music, optionally repeating it repeat times (by default it is played once), using a fade in of fadein milliseconds with a volume value set to ''volume'.
- halt-music #!key fadeoutprocedure
Halts the currently played music, optionally with a fade out set to fadeout milliseconds.
Pauses, resumes or rewinds the currently played music.
- music-finished thunkprocedure
Calls thunk whenever the currently played music is finished.
- music-type musicprocedure
Returns the type of music. The return value is a symbol, and can be: wav, mp3, mod, midi, ogg or user-specific.
- music-volume #!optional newprocedure
Returns or sets the current volume level for music.
Returns #t if music is playing.
Note: A paused state is considered playing for libsdl-mixer...
The procedures in this extension raise a composite condition with the properties:
((exn message msg) (sdl) (mixer))
(use sdl-mixer) (open-audio) (channel-finished (lambda (c) (printf "Channel ~a finished~%" c))) (play-music (load-music "background.mp3")) (let ((s (load-sample "noise.wav"))) (play-sample s)) (close-audio)
The wrapper is licensed as LGPL as is the original libsdl-mixer.
- dev release
- bugfix to appease salmonella
- callbacks added
- defaults of open-audio, pause-channel, halt-channel,
- basically broken
- bugfix release with working callbacks and without the need to install the SDL egg