Audio addon

Audio types
Setting up audio
Misc audio functions
Voice functions
Sample functions
Sample instance functions
Mixer functions
Stream functions
Audio file I/O

These functions are declared in the following header file. Link with allegro_audio.

#include <allegro5/allegro_audio.h>

Audio types

ALLEGRO_AUDIO_DEPTH

enum ALLEGRO_AUDIO_DEPTH

Sample depth and type, and signedness. Mixers only use 32-bit signed float (-1..+1), or 16-bit signed integers. The unsigned value is a bit-flag applied to the depth value.

ALLEGRO_AUDIO_DEPTH_INT8
ALLEGRO_AUDIO_DEPTH_INT16
ALLEGRO_AUDIO_DEPTH_INT24
ALLEGRO_AUDIO_DEPTH_FLOAT32
ALLEGRO_AUDIO_DEPTH_UNSIGNED

For convenience:

ALLEGRO_AUDIO_DEPTH_UINT8
ALLEGRO_AUDIO_DEPTH_UINT16
ALLEGRO_AUDIO_DEPTH_UINT24

ALLEGRO_AUDIO_PAN_NONE

#define ALLEGRO_AUDIO_PAN_NONE      (-1000.0f)

Special value for the ALLEGRO_AUDIOPROP_PAN property. Use this value to play samples at their original volume with panning disabled.

ALLEGRO_CHANNEL_CONF

enum ALLEGRO_CHANNEL_CONF

Speaker configuration (mono, stereo, 2.1, etc).

ALLEGRO_CHANNEL_CONF_1
ALLEGRO_CHANNEL_CONF_2
ALLEGRO_CHANNEL_CONF_3
ALLEGRO_CHANNEL_CONF_4
ALLEGRO_CHANNEL_CONF_5_1
ALLEGRO_CHANNEL_CONF_6_1
ALLEGRO_CHANNEL_CONF_7_1

ALLEGRO_MIXER

typedef struct ALLEGRO_MIXER ALLEGRO_MIXER;

A mixer is a type of stream which mixes together attached streams into a single buffer.

ALLEGRO_MIXER_QUALITY

enum ALLEGRO_MIXER_QUALITY

ALLEGRO_MIXER_QUALITY_POINT - point sampling
ALLEGRO_MIXER_QUALITY_LINEAR - linear interpolation

ALLEGRO_PLAYMODE

enum ALLEGRO_PLAYMODE

Sample and stream playback mode.

ALLEGRO_PLAYMODE_ONCE
ALLEGRO_PLAYMODE_LOOP
ALLEGRO_PLAYMODE_BIDIR

ALLEGRO_SAMPLE_ID

typedef struct ALLEGRO_SAMPLE_ID ALLEGRO_SAMPLE_ID;

An ALLEGRO_SAMPLE_ID represents a sample being played via al_play_sample. It can be used to later stop the sample with al_stop_sample.

ALLEGRO_SAMPLE

typedef struct ALLEGRO_SAMPLE ALLEGRO_SAMPLE;

An ALLEGRO_SAMPLE object stores the data necessary for playing pre-defined digital audio. It holds information pertaining to data length, frequency, channel configuration, etc. You can have an ALLEGRO_SAMPLE object playing multiple times simultaneously. The object holds a user-specified PCM data buffer, of the format the object is created with.

ALLEGRO_SAMPLE_INSTANCE

typedef struct ALLEGRO_SAMPLE_INSTANCE ALLEGRO_SAMPLE_INSTANCE;

An ALLEGRO_SAMPLE_INSTANCE object represents a playable instance of a predefined sound effect. It holds information pertaining to the looping mode, loop start/end points, playing position, etc. An instance uses the data from an ALLEGRO_SAMPLE object. Multiple instances may be created from the same ALLEGRO_SAMPLE. An ALLEGRO_SAMPLE must not be destroyed while there are instances which reference it.

To be played, an ALLEGRO_SAMPLE_INSTANCE object must be attached to an ALLEGRO_VOICE object, or to an ALLEGRO_MIXER object which is itself attached to an ALLEGRO_VOICE object (or to another ALLEGRO_MIXER object which is attached to an ALLEGRO_VOICE object, etc).

ALLEGRO_AUDIO_STREAM

typedef struct ALLEGRO_AUDIO_STREAM ALLEGRO_AUDIO_STREAM;

An ALLEGRO_AUDIO_STREAM object is used to stream generated audio to the sound device, in real-time. This is done by reading from a buffer, which is split into a number of fragments. Whenever a fragment has finished playing, the user can refill it with new data.

As with ALLEGRO_SAMPLE_INSTANCE objects, streams store information necessary for playback, so you may not play the same stream multiple times simultaneously. Streams also need to be attached to an ALLEGRO_VOICE object, or to an ALLEGRO_MIXER object which, eventually, reaches an ALLEGRO_VOICE object.

While playing, you must periodically fill fragments with new audio data. To know when a new fragment is ready to be filled, you can either directly check with al_get_available_audio_stream_fragments, or listen to events from the stream.

You can register an audio stream event source to an event queue; see al_get_audio_stream_event_source. An ALLEGRO_EVENT_AUDIO_STREAM_FRAGMENT event is generated whenever a new fragment is ready. When you receive an event, use al_get_audio_stream_fragment to obtain a pointer to the fragment to be filled. The size and format are determined by the parameters passed to al_create_audio_stream.

If you're late with supplying new data, the stream will be silent until new data is provided. You must call al_drain_audio_stream when you're finished with supplying data to the stream.

If the stream is created by al_load_audio_stream then it can also generate an ALLEGRO_EVENT_AUDIO_STREAM_FINISHED event if it reaches the end of the file and is not set to loop.

ALLEGRO_VOICE

typedef struct ALLEGRO_VOICE ALLEGRO_VOICE;

A voice represents an audio device on the system, which may be a real device, or an abstract device provided by the operating system. To play back audio, you would attach a mixer or sample or stream to a voice.

Setting up audio

al_install_audio

bool al_install_audio(void)

Install the audio subsystem.

Returns true on success, false on failure.

Note: most users will call al_reserve_samples and al_init_acodec_addon after this.

al_uninstall_audio

void al_uninstall_audio(void)

Uninstalls the audio subsystem.

al_is_audio_installed

bool al_is_audio_installed(void)

Returns true if al_install_audio was called previously and returned successfully.

al_reserve_samples

bool al_reserve_samples(int reserve_samples)

Reserves a number of sample instances, attaching them to the default mixer. If no default mixer is set when this function is called, then it will automatically create a voice with an attached mixer, which becomes the default mixer. This diagram illustrates the structures that are set up:

                              sample instance 1
                            / sample instance 2
voice <-- default mixer <---         .
                            \        .
                              sample instance N

Returns true on success, false on error. al_install_audio must have been called first.

Misc audio functions

al_get_allegro_audio_version

uint32_t al_get_allegro_audio_version(void)

Returns the (compiled) version of the addon, in the same format as al_get_allegro_version.

al_get_audio_depth_size

Return the size of a sample, in bytes, for the given format. The format is one of the values listed under ALLEGRO_AUDIO_DEPTH.

al_get_channel_count

Return the number of channels for the given channel configuration, which is one of the values listed under ALLEGRO_CHANNEL_CONF.

Voice functions

al_create_voice

ALLEGRO_VOICE *al_create_voice(unsigned int freq,
   ALLEGRO_AUDIO_DEPTH depth, ALLEGRO_CHANNEL_CONF chan_conf)

Creates a voice structure and allocates a voice from the digital sound driver. The passed frequency, sample format and channel configuration are used as a hint to what kind of data will be sent to the voice. However, the underlying sound driver is free to use non-matching values. For example it may be the native format of the sound hardware. If you attach a mixer to the voice, the mixer will convert from the mixer's format to the voice format and you do not have to care about this. If you access the voice directly, make sure to not rely on the parameters passed to this function, but query the returned voice for the actual settings.

al_destroy_voice

void al_destroy_voice(ALLEGRO_VOICE *voice)

Destroys the voice and deallocates it from the digital driver. Does nothing if the voice is NULL.

al_detach_voice

void al_detach_voice(ALLEGRO_VOICE *voice)

Detaches the sample or mixer stream from the voice.

al_attach_audio_stream_to_voice

bool al_attach_audio_stream_to_voice(ALLEGRO_AUDIO_STREAM *stream,
   ALLEGRO_VOICE *voice)

Attaches an audio stream to a voice. The same rules as al_attach_sample_instance_to_voice apply. This may fail if the driver can't create a voice with the buffer count and buffer size the stream uses.

An audio stream attached directly to a voice has a number of limitations. The audio stream plays immediately and cannot be stopped. The stream position, speed, gain, panning, cannot be changed. At this time, we don't recommend attaching audio streams directly to voices. Use a mixer in between.

Returns true on success, false on failure.

al_attach_mixer_to_voice

bool al_attach_mixer_to_voice(ALLEGRO_MIXER *mixer, ALLEGRO_VOICE *voice)

Attaches a mixer to a voice. The same rules as al_attach_sample_instance_to_voice apply, with the exception of the depth requirement.

Returns true on success, false on failure.

al_attach_sample_instance_to_voice

bool al_attach_sample_instance_to_voice(ALLEGRO_SAMPLE_INSTANCE *spl,
   ALLEGRO_VOICE *voice)

Attaches a sample to a voice, and allows it to play. The sample's volume and loop mode will be ignored, and it must have the same frequency and depth (including signed-ness) as the voice. This function may fail if the selected driver doesn't support preloading sample data.

At this time, we don't recommend attaching samples directly to voices. Use a mixer in between.

Returns true on success, false on failure.

al_get_voice_frequency

unsigned int al_get_voice_frequency(const ALLEGRO_VOICE *voice)

Return the frequency of the voice, e.g. 44100.

al_get_voice_channels

ALLEGRO_CHANNEL_CONF al_get_voice_channels(const ALLEGRO_VOICE *voice)

Return the channel configuration of the voice.

See also: ALLEGRO_CHANNEL_CONF.

al_get_voice_depth

ALLEGRO_AUDIO_DEPTH al_get_voice_depth(const ALLEGRO_VOICE *voice)

Return the audio depth of the voice.

See also: ALLEGRO_AUDIO_DEPTH.

al_get_voice_playing

bool al_get_voice_playing(const ALLEGRO_VOICE *voice)

Return true if the voice is currently playing.

al_set_voice_playing

bool al_set_voice_playing(ALLEGRO_VOICE *voice, bool val)

Change whether a voice is playing or not. This can only work if the voice has a non-streaming object attached to it, e.g. a sample instance. On success the voice's current sample position is reset.

Returns true on success, false on failure.

al_get_voice_position

unsigned int al_get_voice_position(const ALLEGRO_VOICE *voice)

When the voice has a non-streaming object attached to it, e.g. a sample, returns the voice's current sample position. Otherwise, returns zero.

al_set_voice_position

bool al_set_voice_position(ALLEGRO_VOICE *voice, unsigned int val)

Set the voice position. This can only work if the voice has a non-streaming object attached to it, e.g. a sample instance.

Returns true on success, false on failure.

Sample functions

al_create_sample

ALLEGRO_SAMPLE *al_create_sample(void *buf, unsigned int samples,
   unsigned int freq, ALLEGRO_AUDIO_DEPTH depth,
   ALLEGRO_CHANNEL_CONF chan_conf, bool free_buf)

Create a sample data structure from the supplied buffer. If free_buf is true then the buffer will be freed with al_free when the sample data structure is destroyed. For portability (especially Windows), the buffer should have been allocated with al_malloc. Otherwise you should free the sample data yourself.

To allocate a buffer of the correct size, you can use something like this:

sample_size = al_get_channel_count(chan_conf) * al_get_audio_depth_size(depth);
bytes = samples * sample_size;
buffer = al_malloc(bytes);

al_destroy_sample

void al_destroy_sample(ALLEGRO_SAMPLE *spl)

Free the sample data structure. If it was created with the free_buf parameter set to true, then the buffer will be freed with al_free.

This function will stop any sample instances which may be playing the buffer referenced by the ALLEGRO_SAMPLE.

al_play_sample

bool al_play_sample(ALLEGRO_SAMPLE *spl, float gain, float pan, float speed,
   ALLEGRO_PLAYMODE loop, ALLEGRO_SAMPLE_ID *ret_id)

Plays a sample on one of the sample instances created by al_reserve_samples. Returns true on success, false on failure. Playback may fail because all the reserved sample instances are currently used.

Parameters:

gain - relative volume at which the sample is played; 1.0 is normal.
pan - 0.0 is centred, -1.0 is left, 1.0 is right, or ALLEGRO_AUDIO_PAN_NONE.
speed - relative speed at which the sample is played; 1.0 is normal.
loop - ALLEGRO_PLAYMODE_ONCE, ALLEGRO_PLAYMODE_LOOP, or ALLEGRO_PLAYMODE_BIDIR
ret_id - if non-NULL the variable which this points to will be assigned an id representing the sample being played.

al_stop_sample

void al_stop_sample(ALLEGRO_SAMPLE_ID *spl_id)

Stop the sample started by al_play_sample.

al_stop_samples

void al_stop_samples(void)

Stop all samples started by al_play_sample.

al_get_sample_channels

ALLEGRO_CHANNEL_CONF al_get_sample_channels(const ALLEGRO_SAMPLE *spl)

Return the channel configuration.

See also: ALLEGRO_CHANNEL_CONF.

al_get_sample_depth

ALLEGRO_AUDIO_DEPTH al_get_sample_depth(const ALLEGRO_SAMPLE *spl)

Return the audio depth.

See also: ALLEGRO_AUDIO_DEPTH.

al_get_sample_frequency

unsigned int al_get_sample_frequency(const ALLEGRO_SAMPLE *spl)

Return the frequency of the sample.

al_get_sample_length

unsigned int al_get_sample_length(const ALLEGRO_SAMPLE *spl)

Return the length of the sample in sample values.

al_get_sample_data

void *al_get_sample_data(const ALLEGRO_SAMPLE *spl)

Return a pointer to the raw sample data.

Sample instance functions

al_create_sample_instance

ALLEGRO_SAMPLE_INSTANCE *al_create_sample_instance(ALLEGRO_SAMPLE *sample_data)

Creates a sample stream, using the supplied data. This must be attached to a voice or mixer before it can be played. The argument may be NULL. You can then set the data later with al_set_sample.

al_destroy_sample_instance

void al_destroy_sample_instance(ALLEGRO_SAMPLE_INSTANCE *spl)

Detaches the sample stream from anything it may be attached to and frees it (the sample data is not freed!).

al_play_sample_instance

bool al_play_sample_instance(ALLEGRO_SAMPLE_INSTANCE *spl)

Play an instance of a sample data. Returns true on success, false on failure.

al_stop_sample_instance

bool al_stop_sample_instance(ALLEGRO_SAMPLE_INSTANCE *spl)

Stop an sample instance playing.

al_get_sample_instance_channels

ALLEGRO_CHANNEL_CONF al_get_sample_instance_channels(
   const ALLEGRO_SAMPLE_INSTANCE *spl)

Return the channel configuration.

See also: ALLEGRO_CHANNEL_CONF.

al_get_sample_instance_depth

ALLEGRO_AUDIO_DEPTH al_get_sample_instance_depth(const ALLEGRO_SAMPLE_INSTANCE *spl)

Return the audio depth.

See also: ALLEGRO_AUDIO_DEPTH.

al_get_sample_instance_frequency

unsigned int al_get_sample_instance_frequency(const ALLEGRO_SAMPLE_INSTANCE *spl)

Return the frequency of the sample instance.

al_get_sample_instance_length

unsigned int al_get_sample_instance_length(const ALLEGRO_SAMPLE_INSTANCE *spl)

Return the length of the sample instance in sample values.

al_set_sample_instance_length

bool al_set_sample_instance_length(ALLEGRO_SAMPLE_INSTANCE *spl,
   unsigned int val)

Set the length of the sample instance in sample values.

Return true on success, false on failure. Will fail if the sample instance is currently playing.

al_get_sample_instance_position

unsigned int al_get_sample_instance_position(const ALLEGRO_SAMPLE_INSTANCE *spl)

Get the playback position of a sample instance.

al_set_sample_instance_position

bool al_set_sample_instance_position(ALLEGRO_SAMPLE_INSTANCE *spl,
   unsigned int val)

Set the playback position of a sample instance.

Returns true on success, false on failure.

al_get_sample_instance_speed

float al_get_sample_instance_speed(const ALLEGRO_SAMPLE_INSTANCE *spl)

Return the relative playback speed.

al_set_sample_instance_speed

bool al_set_sample_instance_speed(ALLEGRO_SAMPLE_INSTANCE *spl, float val)

Set the relative playback speed. 1.0 is normal speed.

Return true on success, false on failure. Will fail if the sample instance is attached directly to a voice.

al_get_sample_instance_gain

float al_get_sample_instance_gain(const ALLEGRO_SAMPLE_INSTANCE *spl)

Return the playback gain.

al_set_sample_instance_gain

bool al_set_sample_instance_gain(ALLEGRO_SAMPLE_INSTANCE *spl, float val)

Set the playback gain.

Returns true on success, false on failure. Will fail if the sample instance is attached directly to a voice.

al_get_sample_instance_pan

float al_get_sample_instance_pan(const ALLEGRO_SAMPLE_INSTANCE *spl)

Get the pan value.

al_set_sample_instance_pan

bool al_set_sample_instance_pan(ALLEGRO_SAMPLE_INSTANCE *spl, float val)

Set the pan value on a sample instance. A value of -1.0 means to play the sample only through the left speaker; +1.0 means only through the right speaker; 0.0 means the sample is centre balanced.

A constant sound power level is maintained as the sample is panned from left to right. As a consequence, a pan value of 0.0 will play the sample 3 dB softer than the original level. To disable panning and play a sample at its original level, set the pan value to ALLEGRO_AUDIO_PAN_NONE.

Returns true on success, false on failure. Will fail if the sample instance is attached directly to a voice.

(A sound guy should explain that better; I only implemented it. Also this might be more properly called a balance control than pan. Also we don't attempt anything with more than two channels yet.)

al_get_sample_instance_time

float al_get_sample_instance_time(const ALLEGRO_SAMPLE_INSTANCE *spl)

Return the length of the sample instance in seconds, assuming a playback speed of 1.0.

al_get_sample_instance_playmode

ALLEGRO_PLAYMODE al_get_sample_instance_playmode(const ALLEGRO_SAMPLE_INSTANCE *spl)

Return the playback mode.

al_set_sample_instance_playmode

bool al_set_sample_instance_playmode(ALLEGRO_SAMPLE_INSTANCE *spl,
   ALLEGRO_PLAYMODE val)

Set the playback mode.

Returns true on success, false on failure.

al_get_sample_instance_playing

bool al_get_sample_instance_playing(const ALLEGRO_SAMPLE_INSTANCE *spl)

Return true if the sample instance is playing.

al_set_sample_instance_playing

bool al_set_sample_instance_playing(ALLEGRO_SAMPLE_INSTANCE *spl, bool val)

Change whether the sample instance is playing.

Returns true on success, false on failure.

al_get_sample_instance_attached

bool al_get_sample_instance_attached(const ALLEGRO_SAMPLE_INSTANCE *spl)

Return whether the sample instance is attached to something.

al_detach_sample_instance

bool al_detach_sample_instance(ALLEGRO_SAMPLE_INSTANCE *spl)

Detach the sample instance from whatever it's attached to, if anything.

Returns true on success.

al_get_sample

ALLEGRO_SAMPLE *al_get_sample(ALLEGRO_SAMPLE_INSTANCE *spl)

Return the sample data that the sample instance plays.

Note this returns a pointer to an internal structure, not the ALLEGRO_SAMPLE that you may have passed to al_set_sample. You may, however, check which sample buffer is being played by the sample instance with al_get_sample_data, and so on.

al_set_sample

bool al_set_sample(ALLEGRO_SAMPLE_INSTANCE *spl, ALLEGRO_SAMPLE *data)

Change the sample data that a sample instance plays. This can be quite an involved process.

First, the sample is stopped if it is not already.

Next, if data is NULL, the sample is detached from its parent (if any).

If data is not NULL, the sample may be detached and reattached to its parent (if any). This is not necessary if the old sample data and new sample data have the same frequency, depth and channel configuration. Reattaching may not always succeed.

On success, the sample remains stopped. The playback position and loop end points are reset to their default values. The loop mode remains unchanged.

Returns true on success, false on failure. On failure, the sample will be stopped and detached from its parent.

Mixer functions

al_create_mixer

ALLEGRO_MIXER *al_create_mixer(unsigned int freq,
   ALLEGRO_AUDIO_DEPTH depth, ALLEGRO_CHANNEL_CONF chan_conf)

Creates a mixer stream, to attach sample streams or other mixers to. It will mix into a buffer at the requested frequency and channel count.

The only supported audio depths are ALLEGRO_AUDIO_DEPTH_FLOAT32 and ALLEGRO_AUDIO_DEPTH_INT16 (not yet complete).

Returns true on success, false on error.

al_destroy_mixer

void al_destroy_mixer(ALLEGRO_MIXER *mixer)

Destroys the mixer stream.

al_get_default_mixer

ALLEGRO_MIXER *al_get_default_mixer(void)

Return the default mixer, or NULL if one has not been set. Although different configurations of mixers and voices can be used, in most cases a single mixer attached to a voice is what you want. The default mixer is used by al_play_sample.

al_set_default_mixer

bool al_set_default_mixer(ALLEGRO_MIXER *mixer)

Sets the default mixer. All samples started with al_play_sample will be stopped. If you are using your own mixer, this should be called before al_reserve_samples.

Returns true on success, false on error.

al_restore_default_mixer

bool al_restore_default_mixer(void)

Restores Allegro's default mixer. All samples started with al_play_sample will be stopped. Returns true on success, false on error.

al_attach_mixer_to_mixer

bool al_attach_mixer_to_mixer(ALLEGRO_MIXER *stream, ALLEGRO_MIXER *mixer)

Attaches a mixer onto another mixer. The same rules as with al_attach_sample_instance_to_mixer apply, with the added caveat that both mixers must be the same frequency. Returns true on success, false on error.

Currently both mixers must have the same audio depth, otherwise the function fails.

al_attach_sample_instance_to_mixer

bool al_attach_sample_instance_to_mixer(ALLEGRO_SAMPLE_INSTANCE *spl,
   ALLEGRO_MIXER *mixer)

Attach a sample instance to a mixer. The instance must not already be attached to anything.

Returns true on success, false on failure.

al_attach_audio_stream_to_mixer

bool al_attach_audio_stream_to_mixer(ALLEGRO_AUDIO_STREAM *stream, ALLEGRO_MIXER *mixer)

Attach a stream to a mixer.

Returns true on success, false on failure.

al_get_mixer_frequency

unsigned int al_get_mixer_frequency(const ALLEGRO_MIXER *mixer)

Return the mixer frequency.

al_set_mixer_frequency

bool al_set_mixer_frequency(ALLEGRO_MIXER *mixer, unsigned int val)

Set the mixer frequency. This will only work if the mixer is not attached to anything.

Returns true on success, false on failure.

al_get_mixer_channels

ALLEGRO_CHANNEL_CONF al_get_mixer_channels(const ALLEGRO_MIXER *mixer)

Return the mixer channel configuration.

See also: ALLEGRO_CHANNEL_CONF.

al_get_mixer_depth

ALLEGRO_AUDIO_DEPTH al_get_mixer_depth(const ALLEGRO_MIXER *mixer)

Return the mixer audio depth.

See also: ALLEGRO_AUDIO_DEPTH.

al_get_mixer_quality

ALLEGRO_MIXER_QUALITY al_get_mixer_quality(const ALLEGRO_MIXER *mixer)

Return the mixer quality.

al_set_mixer_quality

bool al_set_mixer_quality(ALLEGRO_MIXER *mixer, ALLEGRO_MIXER_QUALITY new_quality)

Set the mixer quality. This can only succeed if the mixer does not have anything attached to it.

Returns true on success, false on failure.

al_get_mixer_playing

bool al_get_mixer_playing(const ALLEGRO_MIXER *mixer)

Return true if the mixer is playing.

al_set_mixer_playing

bool al_set_mixer_playing(ALLEGRO_MIXER *mixer, bool val)

Change whether the mixer is playing.

Returns true on success, false on failure.

al_get_mixer_attached

bool al_get_mixer_attached(const ALLEGRO_MIXER *mixer)

Return true if the mixer is attached to something.

al_detach_mixer

bool al_detach_mixer(ALLEGRO_MIXER *mixer)

Detach the mixer from whatever it is attached to, if anything.

al_set_mixer_postprocess_callback

bool al_set_mixer_postprocess_callback(ALLEGRO_MIXER *mixer,
   void (*pp_callback)(void *buf, unsigned int samples, void *data),
   void *pp_callback_userdata)

Sets a post-processing filter function that's called after the attached streams have been mixed. The buffer's format will be whatever the mixer was created with. The sample count and user-data pointer is also passed.

Stream functions

al_create_audio_stream

ALLEGRO_AUDIO_STREAM *al_create_audio_stream(size_t fragment_count,
   unsigned int samples, unsigned int freq, ALLEGRO_AUDIO_DEPTH depth,
   ALLEGRO_CHANNEL_CONF chan_conf)

Creates an ALLEGRO_AUDIO_STREAM. The stream will be set to play by default. It will feed audio data from a buffer, which is split into a number of fragments.

Parameters:

fragment_count - How many fragments to use for the audio stream. Usually only two fragments are required - splitting the audio buffer in two halves. But it means that the only time when new data can be supplied is whenever one half has finished playing. When using many fragments, you usually will use fewer samples for one, so there always will be (small) fragments available to be filled with new data.
samples - The size of a fragment in samples. See note below.
freq - The frequency, in Hertz.
depth - Must be one of the values listed for ALLEGRO_AUDIO_DEPTH.
chan_conf - Must be one of the values listed for ALLEGRO_CHANNEL_CONF.

The choice of fragment_count, samples and freq directly influences the audio delay. The delay in seconds can be expressed as:

delay = fragment_count * samples / freq

This is only the delay due to Allegro's streaming, there may be additional delay caused by sound drivers and/or hardware.

al_destroy_audio_stream

void al_destroy_audio_stream(ALLEGRO_AUDIO_STREAM *stream)

Destroy an audio stream which was created with al_create_audio_stream or al_load_audio_stream.

al_get_audio_stream_event_source

ALLEGRO_EVENT_SOURCE *al_get_audio_stream_event_source(
   ALLEGRO_AUDIO_STREAM *stream)

Retrieve the associated event source.

See al_get_audio_stream_fragment for a description of the ALLEGRO_EVENT_AUDIO_STREAM_FRAGMENT event that audio streams emit.

al_drain_audio_stream

void al_drain_audio_stream(ALLEGRO_AUDIO_STREAM *stream)

You should call this to finalise an audio stream that you will no longer be feeding, to wait for all pending buffers to finish playing. The stream's playing state will change to false.

al_rewind_audio_stream

bool al_rewind_audio_stream(ALLEGRO_AUDIO_STREAM *stream)

Set the streaming file playing position to the beginning. Returns true on success. Currently this can only be called on streams created with al_load_audio_stream, al_load_audio_stream_f and the format-specific functions underlying those functions.

al_get_audio_stream_frequency

unsigned int al_get_audio_stream_frequency(const ALLEGRO_AUDIO_STREAM *stream)

Return the stream frequency.

al_get_audio_stream_channels

ALLEGRO_CHANNEL_CONF al_get_audio_stream_channels(
   const ALLEGRO_AUDIO_STREAM *stream)

Return the stream channel configuration.

See also: ALLEGRO_CHANNEL_CONF.

al_get_audio_stream_depth

ALLEGRO_AUDIO_DEPTH al_get_audio_stream_depth(
   const ALLEGRO_AUDIO_STREAM *stream)

Return the stream audio depth.

See also: ALLEGRO_AUDIO_DEPTH.

al_get_audio_stream_length

unsigned int al_get_audio_stream_length(const ALLEGRO_AUDIO_STREAM *stream)

Return the stream length in samples.

al_get_audio_stream_speed

float al_get_audio_stream_speed(const ALLEGRO_AUDIO_STREAM *stream)

Return the relative playback speed.

al_set_audio_stream_speed

bool al_set_audio_stream_speed(ALLEGRO_AUDIO_STREAM *stream, float val)

Set the relative playback speed. 1.0 is normal speed.

Return true on success, false on failure. Will fail if the sample instance is attached directly to a voice.

al_get_audio_stream_gain

float al_get_audio_stream_gain(const ALLEGRO_AUDIO_STREAM *stream)

Return the playback gain.

al_set_audio_stream_gain

bool al_set_audio_stream_gain(ALLEGRO_AUDIO_STREAM *stream, float val)

Set the playback gain.

Returns true on success, false on failure. Will fail if the sample instance is attached directly to a voice.

al_get_audio_stream_pan

float al_get_audio_stream_pan(const ALLEGRO_AUDIO_STREAM *stream)

Get the pan value.

al_set_audio_stream_pan

bool al_set_audio_stream_pan(ALLEGRO_AUDIO_STREAM *stream, float val)

Set the pan value on a sample instance. A value of -1.0 means to play the sample only through the left speaker; +1.0 means only through the right speaker; 0.0 means the sample is centre balanced.

Returns true on success, false on failure. Will fail if the sample instance is attached directly to a voice.

al_get_audio_stream_playing

bool al_get_audio_stream_playing(const ALLEGRO_AUDIO_STREAM *stream)

Return true if the stream is playing.

al_set_audio_stream_playing

bool al_set_audio_stream_playing(ALLEGRO_AUDIO_STREAM *stream, bool val)

Change whether the stream is playing.

Returns true on success, false on failure.

al_get_audio_stream_playmode

ALLEGRO_PLAYMODE al_get_audio_stream_playmode(
   const ALLEGRO_AUDIO_STREAM *stream)

Return the playback mode.

al_set_audio_stream_playmode

bool al_set_audio_stream_playmode(ALLEGRO_AUDIO_STREAM *stream,
   ALLEGRO_PLAYMODE val)

Set the playback mode.

Returns true on success, false on failure.

al_get_audio_stream_attached

bool al_get_audio_stream_attached(const ALLEGRO_AUDIO_STREAM *stream)

Return whether the stream is attached to something.

al_detach_audio_stream

bool al_detach_audio_stream(ALLEGRO_AUDIO_STREAM *stream)

Detach the stream from whatever it's attached to, if anything.

al_get_audio_stream_fragment

void *al_get_audio_stream_fragment(const ALLEGRO_AUDIO_STREAM *stream)

When using Allegro's audio streaming, you will use this function to continuously provide new sample data to a stream.

If the stream is ready for new data, the function will return the address of an internal buffer to be filled with audio data. The length and format of the buffer are specified with al_create_audio_stream or can be queried with the various functions described here. Once the buffer is filled, you must signal this to Allegro by passing the buffer to al_set_audio_stream_fragment.

If the stream is not ready for new data, the function will return NULL.

al_set_audio_stream_fragment

bool al_set_audio_stream_fragment(ALLEGRO_AUDIO_STREAM *stream, void *val)

This function needs to be called for every successful call of al_get_audio_stream_fragment to indicate that the buffer is filled with new data.

al_get_audio_stream_fragments

unsigned int al_get_audio_stream_fragments(const ALLEGRO_AUDIO_STREAM *stream)

Returns the number of fragments this stream uses. This is the same value as passed to al_create_audio_stream when a new stream is created.

al_get_available_audio_stream_fragments

unsigned int al_get_available_audio_stream_fragments(
   const ALLEGRO_AUDIO_STREAM *stream)

Returns the number of available fragments in the stream, that is, fragments which are not currently filled with data for playback.

al_seek_audio_stream_secs

bool al_seek_audio_stream_secs(ALLEGRO_AUDIO_STREAM *stream, double time)

Set the streaming file playing position to time. Returns true on success. Currently this can only be called on streams created with al_load_audio_stream, al_load_audio_stream_f and the format-specific functions underlying those functions.

al_get_audio_stream_position_secs

double al_get_audio_stream_position_secs(ALLEGRO_AUDIO_STREAM *stream)

Return the position of the stream in seconds. Currently this can only be called on streams created with al_load_audio_stream.

al_get_audio_stream_length_secs

double al_get_audio_stream_length_secs(ALLEGRO_AUDIO_STREAM *stream)

Return the length of the stream in seconds, if known. Otherwise returns zero.

Currently this can only be called on streams created with al_load_audio_stream, al_load_audio_stream_f and the format-specific functions underlying those functions.

al_set_audio_stream_loop_secs

bool al_set_audio_stream_loop_secs(ALLEGRO_AUDIO_STREAM *stream,
   double start, double end)

Sets the loop points for the stream in seconds. Currently this can only be called on streams created with al_load_audio_stream, al_load_audio_stream_f and the format-specific functions underlying those functions.

Audio file I/O

al_register_sample_loader

bool al_register_sample_loader(const char *ext,
   ALLEGRO_SAMPLE *(*loader)(const char *filename))

Register a handler for al_load_sample. The given function will be used to handle the loading of sample files with the given extension.

The extension should include the leading dot ('.') character. It will be matched case-insensitively.

The loader argument may be NULL to unregister an entry.

Returns true on success, false on error. Returns false if unregistering an entry that doesn't exist.

al_register_sample_loader_f

bool al_register_sample_loader_f(const char *ext,
   ALLEGRO_SAMPLE *(*loader)(ALLEGRO_FILE* fp))

Register a handler for al_load_sample_f. The given function will be used to handle the loading of sample files with the given extension.

The extension should include the leading dot ('.') character. It will be matched case-insensitively.

The loader argument may be NULL to unregister an entry.

Returns true on success, false on error. Returns false if unregistering an entry that doesn't exist.

al_register_sample_saver

bool al_register_sample_saver(const char *ext,
   bool (*saver)(const char *filename, ALLEGRO_SAMPLE *spl))

Register a handler for al_save_sample. The given function will be used to handle the saving of sample files with the given extension.

The extension should include the leading dot ('.') character. It will be matched case-insensitively.

The saver argument may be NULL to unregister an entry.

Returns true on success, false on error. Returns false if unregistering an entry that doesn't exist.

al_register_sample_saver_f

bool al_register_sample_saver_f(const char *ext,
   bool (*saver)(ALLEGRO_FILE* fp, ALLEGRO_SAMPLE *spl))

Register a handler for al_save_sample_f. The given function will be used to handle the saving of sample files with the given extension.

The extension should include the leading dot ('.') character. It will be matched case-insensitively.

The saver argument may be NULL to unregister an entry.

Returns true on success, false on error. Returns false if unregistering an entry that doesn't exist.

al_register_audio_stream_loader

bool al_register_audio_stream_loader(const char *ext,
   ALLEGRO_AUDIO_STREAM *(*stream_loader)(const char *filename,
      size_t buffer_count, unsigned int samples))

Register a handler for al_load_audio_stream. The given function will be used to open streams from files with the given extension.

The extension should include the leading dot ('.') character. It will be matched case-insensitively.

The stream_loader argument may be NULL to unregister an entry.

Returns true on success, false on error. Returns false if unregistering an entry that doesn't exist.

al_register_audio_stream_loader_f

bool al_register_audio_stream_loader_f(const char *ext,
   ALLEGRO_AUDIO_STREAM *(*stream_loader)(ALLEGRO_FILE* fp,
      size_t buffer_count, unsigned int samples))

Register a handler for al_load_audio_stream_f. The given function will be used to open streams from files with the given extension.

The extension should include the leading dot ('.') character. It will be matched case-insensitively.

The stream_loader argument may be NULL to unregister an entry.

Returns true on success, false on error. Returns false if unregistering an entry that doesn't exist.

al_load_sample

ALLEGRO_SAMPLE *al_load_sample(const char *filename)

Loads a few different audio file formats based on their extension.

Note that this stores the entire file in memory at once, which may be time consuming. To read the file as it is needed, use al_load_audio_stream.

Returns the sample on success, NULL on failure.

al_load_sample_f

ALLEGRO_SAMPLE *al_load_sample_f(ALLEGRO_FILE* fp, const char *ident)

Loads an audio file from an ALLEGRO_FILE stream into an ALLEGRO_SAMPLE. The file type is determined by the passed 'ident' parameter, which is a file name extension including the leading dot.

Note that this stores the entire file in memory at once, which may be time consuming. To read the file as it is needed, use al_load_audio_stream_f.

Returns the sample on success, NULL on failure. The file remains open afterwards.

al_load_audio_stream

ALLEGRO_AUDIO_STREAM *al_load_audio_stream(const char *filename,
   size_t buffer_count, unsigned int samples)

Loads an audio file from disk as it is needed.

Unlike regular streams, the one returned by this function need not be fed by the user; the library will automatically read more of the file as it is needed. The stream will contain buffer_count buffers with samples samples.

The audio stream will start in the playing state. It should be attached to a voice or mixer to generate any output. See ALLEGRO_AUDIO_STREAM for more details.

Returns the stream on success, NULL on failure.

al_load_audio_stream_f

ALLEGRO_AUDIO_STREAM *al_load_audio_stream_f(ALLEGRO_FILE* fp, const char *ident,
   size_t buffer_count, unsigned int samples)

Loads an audio file from ALLEGRO_FILE stream as it is needed.

The file type is determined by the passed 'ident' parameter, which is a file name extension including the leading dot.

The audio stream will start in the playing state. It should be attached to a voice or mixer to generate any output. See ALLEGRO_AUDIO_STREAM for more details.

Returns the stream on success, NULL on failure. On success the file should be considered owned by the audio stream, and will be closed when the audio stream is destroyed. On failure the file will be closed.

al_save_sample

bool al_save_sample(const char *filename, ALLEGRO_SAMPLE *spl)

Writes a sample into a file. Currently, wav is the only supported format, and the extension must be '.wav'.

Returns true on success, false on error.

al_save_sample_f

bool al_save_sample_f(ALLEGRO_FILE *fp, const char *ident, ALLEGRO_SAMPLE *spl)

Writes a sample into a ALLEGRO_FILE filestream. Currently, wav is the only supported format, and the extension must be '.wav'.

Returns true on success, false on error. The file remains open afterwards.

Allegro version 5.0.4 - Last updated: 2011-08-14 04:29:58 UTC