Unit sdl2_mixer

Dynamically change the number of channels managed by the mixer. If decreasing the number of channels, the upper channels are stopped. This function returns the new number of allocated channels.

Close the mixer, halting all playing audio *

Change the expiration delay for a particular channel. The sample will stop playing after the 'ticks' milliseconds have elapsed, or remove the expiration if 'ticks' is -1

Fade in music or a channel over "ms" milliseconds, same semantics as the "Play" functions *

Halt a channel, fading it out progressively till it's silent The ms parameter indicates the number of milliseconds the fading will take.

Query the fading status of a channel *

Free an audio chunk previously loaded *

Get the Mix_Chunk currently associated with a mixer channel Returns NULL if it's an invalid channel, or there's no chunk associated.

Get a pointer to the user data for the current music hook *

Find out the music format of a mixer music, or the currently playing music, if 'music' is NULL.

Get a list of chunk/music decoders that this build of SDL_mixer provides. This list can change between builds AND runs of the program, if external libraries that add functionality become available. You must successfully call Mix_OpenAudio() before calling these functions. This API is only available in SDL_mixer 1.2.9 and later.

// usage... int i; const int total = Mix_GetNumChunkDecoders(); for (i = 0; i < total; i++) printf("Supported chunk decoder: [%s]\n", Mix_GetChunkDecoder(i));

Appearing in this list doesn't promise your specific audio file will decode...but it's handy to know if you have, say, a functioning Timidity install.

These return values are static, read-only data; do not modify or free it. The pointers remain valid until you call Mix_CloseAudio().

Finds the first available channel in a group of channels, returning -1 if none are available.

Attach a tag to a channel. A tag can be assigned to several mixer channels, to form groups of channels. If 'tag' is -1, the tag is removed (actually -1 is the tag used to represent the group of all the channels). Returns true if everything was OK.

Assign several consecutive channels to a group *

Returns the number of channels in a group. This is also a subtle way to get the total number of channels when 'tag' is -1

Finds the "most recent" (i.e. last) sample playing in a group of channels *

Finds the "oldest" sample playing in a group of channels *

Halt playing of a particular channel *

Add your own music player or additional mixer function. If 'mix_func' is NULL, the default music player is re-enabled.

Loads dynamic libraries and prepares them for use. Flags should be one or more flags from MIX_InitFlags OR'd together. It returns the flags successfully initialized, or 0 on failure.

This function gets the version of the dynamically linked SDL_mixer library. it should NOT be used to fill a version structure, instead you should use the SDL_MIXER_VERSION() macro.

Load a music file from an SDL_RWop object assuming a specific format *

Load a music file from an SDL_RWop object (Ogg and MikMod specific currently) Matt Campbell (matt@campbellhome.dhs.org) April 2000 *

Load a wave file or a music (.mod .s3m .it .xm) file *

Open the mixer with a certain audio format *

Pause/Resume a particular channel *

Pause/Resume the music stream *

Play an audio chunk on a specific channel. If the specified channel is -1, play on the first free channel. If 'loops' is greater than zero, loop the sound that many times. If 'loops' is -1, loop inifinitely (˜65000 times). Returns which channel was used to play the sound.

The same as above, but the sound is played at most 'ticks' milliseconds *

Check the status of a specific channel. If the specified channel is -1, check all channels.

Find out what the actual audio device parameters are. This function returns 1 if the audio has been opened, 0 otherwise.

Load raw audio data of the mixer format from a memory buffer *

Load a wave file of the mixer format from a memory buffer *

Unloads libraries loaded with Mix_Init *

Register a special effect function. At mixing time, the channel data is copied into a buffer and passed through each registered effect function. After it passes through all the functions, it is mixed into the final output stream. The copy to buffer is performed once, then each effect function performs on the output of the previous effect. Understand that this extra copy to a buffer is not performed if there are no effects registered for a given chunk, which saves CPU cycles, and any given effect will be extra cycles, too, so it is crucial that your code run fast. Also note that the data that your function is given is in the format of the sound device, and not the format you gave to Mix_OpenAudio(), although they may in reality be the same. This is an unfortunate but necessary speed concern. Use Mix_QuerySpec() to determine if you can handle the data before you register your effect, and take appropriate actions. You may also specify a callback (Mix_EffectDone_t) that is called when the channel finishes playing. This gives you a more fine-grained control than Mix_ChannelFinished(), in case you need to free effect-specific resources, etc. If you don't need this, you can specify NULL. You may set the callbacks before or after calling Mix_PlayChannel(). Things like Mix_SetPanning() are just internal special effect functions, so if you are using that, you've already incurred the overhead of a copy to a separate buffer, and that these effects will be in the queue with any functions you've registered. The list of registered effects for a channel is reset when a chunk finishes playing, so you need to explicitly set them with each call to Mix_PlayChannel*(). You may also register a special effect function that is to be run after final mixing occurs. The rules for these callbacks are identical to those in Mix_RegisterEffect, but they are run after all the channels and the music have been mixed into a single stream, whereas channel-specific effects run on a given channel before any other mixing occurs. These global effect callbacks are call "posteffects". Posteffects only have their Mix_EffectDone_t function called when they are unregistered (since the main output stream is never "done" in the same sense as a channel). You must unregister them manually when you've had enough. Your callback will be told that the channel being mixed is (MIX_CHANNEL_POST) if the processing is considered a posteffect.

After all these effects have finished processing, the callback registered through Mix_SetPostMix() runs, and then the stream goes to the audio device.

DO NOT EVER call SDL_LockAudio() from your callback function!

returns zero if error (no such channel), nonzero if added. Error messages can be retrieved from Mix_GetError().

Reserve the first channels (0 -> n-1) for the application, i.e. don't allocate them dynamically to the next sample if requested with a -1 value below. Returns the number of reserved channels.

Set the "distance" of a channel. (distance) is an integer from 0 to 255 that specifies the location of the sound in relation to the listener. Distance 0 is overlapping the listener, and 255 is as far away as possible A distance of 255 does not guarantee silence; in such a case, you might want to try changing the chunk's volume, or just cull the sample from the mixing process with Mix_HaltChannel(). For efficiency, the precision of this effect may be limited (distances 1 through 7 might all produce the same effect, 8 through 15 are equal, etc). (distance) is an integer between 0 and 255 that specifies the space between the sound and the listener. The larger the number, the further away the sound is. Setting (distance) to 0 unregisters this effect, since the data would be unchanged. If you need more precise positional audio, consider using OpenAL for spatialized effects instead of SDL_mixer. This is only meant to be a basic effect for simple "3D" games.

Setting (channel) to MIX_CHANNEL_POST registers this as a posteffect, and the distance attenuation will be done to the final mixed stream before passing it on to the audio device.

This uses the Mix_RegisterEffect() API internally.

returns zero if error (no such channel or Mix_RegisterEffect() fails), nonzero if position effect is enabled. Error messages can be retrieved from Mix_GetError().

We'll use SDL for reporting errors *

Stop music and set external music playback command *

Set the current position in the music stream. This returns 0 if successful, or -1 if it failed or isn't implemented. This function is only implemented for MOD music formats (set pattern order number) and for OGG, FLAC, MP3_MAD, MP3_MPG and MODPLUG music (set position in seconds), at the moment.

Set the panning of a channel. The left and right channels are specified as integers between 0 and 255, quietest to loudest, respectively.

Technically, this is just individual volume control for a sample with two (stereo) channels, so it can be used for more than just panning. If you want real panning, call it like this:

Mix_SetPanning(channel, left, 255 - left);

...which isn't so hard.

Setting (channel) to MIX_CHANNEL_POST registers this as a posteffect, and the panning will be done to the final mixed stream before passing it on to the audio device.

This uses the Mix_RegisterEffect() API internally, and returns without registering the effect function if the audio device is not configured for stereo output. Setting both (left) and (right) to 255 causes this effect to be unregistered, since that is the data's normal state.

returns zero if error (no such channel or Mix_RegisterEffect() fails), nonzero if panning effect enabled. Note that an audio device in mono mode is a no-op, but this call will return successful in that case. Error messages can be retrieved from Mix_GetError().

Set the position of a channel. (angle) is an integer from 0 to 360, that specifies the location of the sound in relation to the listener. (angle) will be reduced as neccesary (540 becomes 180 degrees, -100 becomes 260). Angle 0 is due north, and rotates clockwise as the value increases. For efficiency, the precision of this effect may be limited (angles 1 through 7 might all produce the same effect, 8 through 15 are equal, etc). (distance) is an integer between 0 and 255 that specifies the space between the sound and the listener. The larger the number, the further away the sound is. Using 255 does not guarantee that the channel will be culled from the mixing process or be completely silent. For efficiency, the precision of this effect may be limited (distance 0 through 5 might all produce the same effect, 6 through 10 are equal, etc). Setting (angle) and (distance) to 0 unregisters this effect, since the data would be unchanged.

If you need more precise positional audio, consider using OpenAL for spatialized effects instead of SDL_mixer. This is only meant to be a basic effect for simple "3D" games.

If the audio device is configured for mono output, then you won't get any effectiveness from the angle; however, distance attenuation on the channel will still occur. While this effect will function with stereo voices, it makes more sense to use voices with only one channel of sound, so when they are mixed through this effect, the positioning will sound correct. You can convert them to mono through SDL before giving them to the mixer in the first place if you like.

Setting (channel) to MIX_CHANNEL_POST registers this as a posteffect, and the positioning will be done to the final mixed stream before passing it on to the audio device.

This is a convenience wrapper over Mix_SetDistance() and Mix_SetPanning().

returns zero if error (no such channel or Mix_RegisterEffect() fails), nonzero if position effect is enabled. Error messages can be retrieved from Mix_GetError().

Causes a channel to reverse its stereo. This is handy if the user has his speakers hooked up backwards, or you would like to have a minor bit of psychedelia in your sound code. :) Calling this function with (flip) set to non-zero reverses the chunks's usual channels. If (flip) is zero, the effect is unregistered.

This uses the Mix_RegisterEffect() API internally, and thus is probably more CPU intensive than having the user just plug in his speakers correctly. Mix_SetReverseStereo() returns without registering the effect function if the audio device is not configured for stereo output.

If you specify MIX_CHANNEL_POST for (channel), then this the effect is used on the final mixed stream before sending it on to the audio device (a posteffect).

returns zero if error (no such channel or Mix_RegisterEffect() fails), nonzero if reversing effect is enabled. Note that an audio device in mono mode is a no-op, but this call will return successful in that case. Error messages can be retrieved from Mix_GetError().

Set/Get/Iterate SoundFonts paths to use by supported MIDI backends *

Synchro value is set by MikMod from modules while playing *

You may not need to call this explicitly, unless you need to stop all effects from processing in the middle of a chunk's playback. Note that this will also shut off some internal effect processing, since Mix_SetPanning() and others may use this API under the hood. This is called internally when a channel completes playback. Posteffects are never implicitly unregistered as they are for channels, but they may be explicitly unregistered through this function by specifying MIX_CHANNEL_POST for a channel. returns zero if error (no such channel), nonzero if all effects removed. Error messages can be retrieved from Mix_GetError().

You may not need to call this explicitly, unless you need to stop an effect from processing in the middle of a chunk's playback. Posteffects are never implicitly unregistered as they are for channels, but they may be explicitly unregistered through this function by specifying MIX_CHANNEL_POST for a channel. returns zero if error (no such channel or effect), nonzero if removed. Error messages can be retrieved from Mix_GetError().

Set the volume in the range of 0-128 of a specific channel or chunk. If the specified channel is -1, set volume for all channels. Returns the original volume. If the specified volume is -1, just return the current volume.

This macro can be used to fill a version structure with the compile-time version of the SDL_mixer library.

"The following type designates an unsigned integer type [or signed respectivly] with the property that any valid pointer to void can be converted to this type, then converted back to a pointer to void, and the result will compare equal to the original pointer: uintptr_t" Source: https://pubs.opengroup.org/onlinepubs/000095399/basedefs/stdint.h.html

Add your own callback when a channel has finished playing. NULL to disable callback. The callback may be called from the mixer's audio callback or it could be called as a result of Mix_HaltChannel(), etc. do not call SDL_LockAudio() from this callback; you will either be inside the audio callback, or SDL_mixer will explicitly lock the audio before calling your callback.

The internal format for an audio chunk *

This is a callback that signifies that a channel has finished all its loops and has completed playback. This gets called if the buffer plays out normally, or if you call Mix_HaltChannel(), implicitly stop a channel via Mix_AllocateChannels(), or unregister a callback while it's still playing.

DO NOT EVER call SDL_LockAudio() from your callback function!

This is the format of a special effect callback:

myeffect(int chan, void *stream, int len, void *udata);

(chan) is the channel number that your effect is affecting. (stream) is the buffer of data to work upon. (len) is the size of (stream), and (udata) is a user-defined bit of data, which you pass as the last arg of Mix_RegisterEffect(), and is passed back unmolested to your callback. Your effect changes the contents of (stream) based on whatever parameters are significant, or just leaves it be, if you prefer. You can do whatever you like to the buffer, though, and it will continue in its changed state down the mixing pipeline, through any other effect functions, then finally to be mixed with the rest of the channels and music for the final output stream.

DO NOT EVER call SDL_LockAudio() from your callback function!

The different fading types supported *

Set a function that is called after all mixing is performed. This can be used to provide real-time visual display of the audio stream or add a custom mixer filter for the stream data.

// Removed in SDL2_mixer 2.0.2 MIX_INIT_MODPLUG = $00000004; MIX_INIT_FLUIDSYNTH = $00000020;

The internal format for a music chunk interpreted via mikmod *

Add your own callback when the music has finished playing or when it is stopped from a call to Mix_HaltMusic.

Data types for all compilers

Values

• MIX_NO_FADING
• MIX_FADING_OUT
• MIX_FADING_IN

Values

• MUS_NONE
• MUS_CMD
• MUS_WAV
• MUS_MOD
• MUS_MID
• MUS_OGG
• MUS_MP3
• MUS_MP3_MAD_UNUSED
• MUS_FLAC
• MUS_MODPLUG_UNUSED
• MUS_OPUS

The default mixer has 8 simultaneous mixing channels *

Special Effects API by ryan c. gordon. (icculus@icculus.org) *

Good default values for a PC soundcard *

Backwards compatibility *

Printable format: "%d.%d.%d", MAJOR, MINOR, PATCHLEVEL *