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Article contents:== Outdated egg! This is an egg for CHICKEN 4, the unsupported old release. You're almost certainly looking for [[/eggref/5/sdl-mixer|the CHICKEN 5 version of this egg]], if it exists. If it does not exist, there may be equivalent functionality provided by another egg; have a look at the [[https://wiki.call-cc.org/chicken-projects/egg-index-5.html|egg index]]. Otherwise, please consider porting this egg to the current version of CHICKEN. [[tags: egg sdl-mixer]] == sdl-mixer [[toc:]] === Introduction This egg provides a schemely wrapper around the libsdl-mixer library. The original library documentation can be found at [[http://www.libsdl.org/projects/SDL_mixer/docs/SDL_mixer.html|the libsdl website]]. === Author [[/users/christian-kellermann|Christian Kellermann]] === Requirements sdl-mixer headers and libraries must be present. Versions prior to 0.6 also needed the SDL egg. === API ==== Overview Opening and closing the audio device <procedure>(open-audio #!key sampling-rate sample-format channels chunk-size)</procedure> 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: ; sampling-rate : 44100 ; sample-format : AUDIO_S16SYS ; channels : 2 ; chunk-size : 1024 ''Note:'' The sdl-init and mix-init procedures will be called only once. <procedure>(close-audio)</procedure> Closes the audio device and shuts down the mixer library. No procedure should access libsdl-mixer or sdl audio procedures after calling ''close-audio''. ==== Playing samples in channels <procedure>(load-sample filename) => sample</procedure> 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''. <procedure>(play-sample sample #!key channel repeat fadein duration)</procedure> 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. <procedure>(pause-channel #!optional channel)</procedure> <procedure>(resume-channel #!optional channel)</procedure> Will pause or resume all channels or the given ''channel''. <procedure>(halt-channel #!optional channel #!key fadeout)</procedure> 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. <procedure>(channel-finished proc)</procedure> 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. <procedure>(channel-playing? channel)</procedure> <procedure>(channel-paused? channel)</procedure> Predicates indicating whether ''channel'' is in playing or paused state. ==== Playing music <procedure>(load-music filename) => music</procedure> 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''. <procedure>(play-music music #!key repeat fadein volume)</procedure> 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'. <procedure>(halt-music #!key fadeout)</procedure> Halts the currently played music, optionally with a fade out set to ''fadeout'' milliseconds. <procedure>(pause-music)</procedure> <procedure>(resume-music)</procedure> <procedure>(rewind-music)</procedure> Pauses, resumes or rewinds the currently played music. <procedure>(music-finished thunk)</procedure> Calls ''thunk'' whenever the currently played music is finished. <procedure>(music-type music)</procedure> Returns the type of ''music''. The return value is a symbol, and can be: ''wav'', ''mp3'', ''mod'', ''midi'', ''ogg'' or ''user-specific''. <procedure>(music-volume #!optional new)</procedure> Returns or sets the current volume level for music. <procedure>(music-playing?)</procedure> Returns ''#t'' if music is playing. '''Note:''' A paused state is considered playing for libsdl-mixer... ==== Errors The procedures in this extension raise a composite condition with the properties: ((exn message msg) (sdl) (mixer)) === Example <enscript language="scheme"> (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) </enscript> === License The wrapper is licensed as [[https://www.gnu.org/licenses/lgpl-3.0.txt|LGPL]] as is the original libsdl-mixer. === Version history ; 0.1 : dev release ; 0.2 : bugfix to appease salmonella ; 0.3 : callbacks added ; 0.4 : defaults of open-audio, pause-channel, halt-channel, rewind-channel changed ; 0.5 : basically broken ; 0.6 : bugfix release with working callbacks and without the need to install the SDL egg Description of your changes:

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