Documentation

Use this function to get the number of built-in audio drivers.

This function returns a hardcoded number. This never returns a negative value; if there are no drivers compiled into this build of SDL, this function returns zero. The presence of a driver in this list does not mean it will function, it just means SDL is capable of interacting with that interface. For example, a build of SDL might have esound support, but if there's no esound server available, SDL's esound driver would fail if used.

By default, SDL tries all drivers, in its preferred order, until one is found to be usable.

Returns

the number of built-in audio drivers.

Thread safety

It is safe to call this function from any thread.

See also

sDL_GetAudioDriver

C declaration

SDL_GetNumAudioDrivers, defined at SDL3/SDL_audio.h 478:33

Since: 3.2.0

Use this function to get the name of a built in audio driver.

The list of audio drivers is given in the order that they are normally initialized by default; the drivers that seem more reasonable to choose first (as far as the SDL developers believe) are earlier in the list.

The names of drivers are all simple, low-ASCII identifiers, like "alsa", "coreaudio" or "wasapi". These never have Unicode characters, and are not meant to be proper names.

Returns

the name of the audio driver at the requested index, or NULL if an invalid index was specified.

Thread safety

It is safe to call this function from any thread.

See also

sDL_GetNumAudioDrivers

C declaration

SDL_GetAudioDriver, defined at SDL3/SDL_audio.h 502:42

Since: 3.2.0

Get the name of the current audio driver.

The names of drivers are all simple, low-ASCII identifiers, like "alsa", "coreaudio" or "wasapi". These never have Unicode characters, and are not meant to be proper names.

Returns

the name of the current audio driver or NULL if no driver has been initialized.

Thread safety

It is safe to call this function from any thread.

C declaration

SDL_GetCurrentAudioDriver, defined at SDL3/SDL_audio.h 518:42

Since: 3.2.0

Get a list of currently-connected audio playback devices.

This returns of list of available devices that play sound, perhaps to speakers or headphones ("playback" devices). If you want devices that record audio, like a microphone ("recording" devices), use SDL_GetAudioRecordingDevices() instead.

This only returns a list of physical devices; it will not have any device IDs returned by SDL_OpenAudioDevice().

If this function returns NULL, to signify an error, *count will be set to zero.

Returns

a 0 terminated array of device instance IDs or NULL on error; call SDL_GetError() for more information. This should be freed with SDL_free() when it is no longer needed.

Thread safety

It is safe to call this function from any thread.

See also

sDL_OpenAudioDevice, sDL_GetAudioRecordingDevices

C declaration

SDL_GetAudioPlaybackDevices, defined at SDL3/SDL_audio.h 547:49

Since: 3.2.0

Get a list of currently-connected audio recording devices.

This returns of list of available devices that record audio, like a microphone ("recording" devices). If you want devices that play sound, perhaps to speakers or headphones ("playback" devices), use SDL_GetAudioPlaybackDevices() instead.

This only returns a list of physical devices; it will not have any device IDs returned by SDL_OpenAudioDevice().

If this function returns NULL, to signify an error, *count will be set to zero.

Returns

a 0 terminated array of device instance IDs, or NULL on failure; call SDL_GetError() for more information. This should be freed with SDL_free() when it is no longer needed.

Thread safety

It is safe to call this function from any thread.

See also

sDL_OpenAudioDevice, sDL_GetAudioPlaybackDevices

C declaration

SDL_GetAudioRecordingDevices, defined at SDL3/SDL_audio.h 576:49

Since: 3.2.0

Get the human-readable name of a specific audio device.

WARNING: this function will work with SDL_AUDIO_DEVICE_DEFAULT_PLAYBACK and SDL_AUDIO_DEVICE_DEFAULT_RECORDING, returning the current default physical devices' names. However, as the default device may change at any time, it is likely better to show a generic name to the user, like "System default audio device" or perhaps "default [currently %s]". Do not store this name to disk to reidentify the device in a later run of the program, as the default might change in general, and the string will be the name of a specific device and not the abstract system default.

Returns

the name of the audio device, or NULL on failure; call SDL_GetError() for more information.

Thread safety

It is safe to call this function from any thread.

See also

sDL_GetAudioPlaybackDevices, sDL_GetAudioRecordingDevices

C declaration

SDL_GetAudioDeviceName, defined at SDL3/SDL_audio.h 601:42

Since: 3.2.0

Get the current audio format of a specific audio device.

For an opened device, this will report the format the device is currently using. If the device isn't yet opened, this will report the device's preferred format (or a reasonable default if this can't be determined).

You may also specify SDL_AUDIO_DEVICE_DEFAULT_PLAYBACK or SDL_AUDIO_DEVICE_DEFAULT_RECORDING here, which is useful for getting a reasonable recommendation before opening the system-recommended default device.

You can also use this to request the current device buffer size. This is specified in sample frames and represents the amount of data SDL will feed to the physical hardware in each chunk. This can be converted to milliseconds of audio with the following equation:

ms = (int) ((((Sint64) frames) * 1000) / spec.freq);

Buffer size is only important if you need low-level control over the audio playback timing. Most apps do not need this.

Returns

true on success or false on failure; call SDL_GetError() for more information.

Thread safety

It is safe to call this function from any thread.

C declaration

SDL_GetAudioDeviceFormat, defined at SDL3/SDL_audio.h 636:34

Since: 3.2.0

Get the current channel map of an audio device.

Channel maps are optional; most things do not need them, instead passing data in the order that SDL expects.

Audio devices usually have no remapping applied. This is represented by returning NULL, and does not signify an error.

Returns

an array of the current channel mapping, with as many elements as the current output spec's channels, or NULL if default. This should be freed with SDL_free() when it is no longer needed.

Thread safety

It is safe to call this function from any thread.

See also

sDL_SetAudioStreamInputChannelMap

C declaration

SDL_GetAudioDeviceChannelMap, defined at SDL3/SDL_audio.h 659:35

Since: 3.2.0

Open a specific audio device.

You can open both playback and recording devices through this function. Playback devices will take data from bound audio streams, mix it, and send it to the hardware. Recording devices will feed any bound audio streams with a copy of any incoming data.

An opened audio device starts out with no audio streams bound. To start audio playing, bind a stream and supply audio data to it. Unlike SDL2, there is no audio callback; you only bind audio streams and make sure they have data flowing into them (however, you can simulate SDL2's semantics fairly closely by using SDL_OpenAudioDeviceStream instead of this function).

If you don't care about opening a specific device, pass a devid of either SDL_AUDIO_DEVICE_DEFAULT_PLAYBACK or SDL_AUDIO_DEVICE_DEFAULT_RECORDING. In this case, SDL will try to pick the most reasonable default, and may also switch between physical devices seamlessly later, if the most reasonable default changes during the lifetime of this opened device (user changed the default in the OS's system preferences, the default got unplugged so the system jumped to a new default, the user plugged in headphones on a mobile device, etc). Unless you have a good reason to choose a specific device, this is probably what you want.

You may request a specific format for the audio device, but there is no promise the device will honor that request for several reasons. As such, it's only meant to be a hint as to what data your app will provide. Audio streams will accept data in whatever format you specify and manage conversion for you as appropriate. SDL_GetAudioDeviceFormat can tell you the preferred format for the device before opening and the actual format the device is using after opening.

It's legal to open the same device ID more than once; each successful open will generate a new logical SDL_AudioDeviceID that is managed separately from others on the same physical device. This allows libraries to open a device separately from the main app and bind its own streams without conflicting.

It is also legal to open a device ID returned by a previous call to this function; doing so just creates another logical device on the same physical device. This may be useful for making logical groupings of audio streams.

This function returns the opened device ID on success. This is a new, unique SDL_AudioDeviceID that represents a logical device.

Some backends might offer arbitrary devices (for example, a networked audio protocol that can connect to an arbitrary server). For these, as a change from SDL2, you should open a default device ID and use an SDL hint to specify the target if you care, or otherwise let the backend figure out a reasonable default. Most backends don't offer anything like this, and often this would be an end user setting an environment variable for their custom need, and not something an application should specifically manage.

When done with an audio device, possibly at the end of the app's life, one should call SDL_CloseAudioDevice() on the returned device id.

Returns

the device ID on success or 0 on failure; call SDL_GetError() for more information.

Thread safety

It is safe to call this function from any thread.

See also

sDL_CloseAudioDevice, sDL_GetAudioDeviceFormat

C declaration

SDL_OpenAudioDevice, defined at SDL3/SDL_audio.h 735:47

Since: 3.2.0

Determine if an audio device is physical (instead of logical).

An SDL_AudioDeviceID that represents physical hardware is a physical device; there is one for each piece of hardware that SDL can see. Logical devices are created by calling SDL_OpenAudioDevice or SDL_OpenAudioDeviceStream, and while each is associated with a physical device, there can be any number of logical devices on one physical device.

For the most part, logical and physical IDs are interchangeable if you try to open a logical device, SDL understands to assign that effort to the underlying physical device, etc. However, it might be useful to know if an arbitrary device ID is physical or logical. This function reports which.

This function may return either true or false for invalid device IDs.

Returns

true if devid is a physical device, false if it is logical.

Thread safety

It is safe to call this function from any thread.

C declaration

SDL_IsAudioDevicePhysical, defined at SDL3/SDL_audio.h 760:34

Since: 3.2.0

Determine if an audio device is a playback device (instead of recording).

This function may return either true or false for invalid device IDs.

Returns

true if devid is a playback device, false if it is recording.

Thread safety

It is safe to call this function from any thread.

C declaration

SDL_IsAudioDevicePlayback, defined at SDL3/SDL_audio.h 774:34

Since: 3.2.0

Use this function to pause audio playback on a specified device.

This function pauses audio processing for a given device. Any bound audio streams will not progress, and no audio will be generated. Pausing one device does not prevent other unpaused devices from running.

Unlike in SDL2, audio devices start in an unpaused state, since an app has to bind a stream before any audio will flow. Pausing a paused device is a legal no-op.

Pausing a device can be useful to halt all audio without unbinding all the audio streams. This might be useful while a game is paused, or a level is loading, etc.

Physical devices can not be paused or unpaused, only logical devices created through SDL_OpenAudioDevice() can be.

Returns

true on success or false on failure; call SDL_GetError() for more information.

Thread safety

It is safe to call this function from any thread.

See also

sDL_ResumeAudioDevice, sDL_AudioDevicePaused

C declaration

SDL_PauseAudioDevice, defined at SDL3/SDL_audio.h 805:34

Since: 3.2.0

Use this function to unpause audio playback on a specified device.

This function unpauses audio processing for a given device that has previously been paused with SDL_PauseAudioDevice(). Once unpaused, any bound audio streams will begin to progress again, and audio can be generated.

Unlike in SDL2, audio devices start in an unpaused state, since an app has to bind a stream before any audio will flow. Unpausing an unpaused device is a legal no-op.

Physical devices can not be paused or unpaused, only logical devices created through SDL_OpenAudioDevice() can be.

Returns

true on success or false on failure; call SDL_GetError() for more information.

Thread safety

It is safe to call this function from any thread.

See also

sDL_AudioDevicePaused, sDL_PauseAudioDevice

C declaration

SDL_ResumeAudioDevice, defined at SDL3/SDL_audio.h 833:34

Since: 3.2.0

Use this function to query if an audio device is paused.

Unlike in SDL2, audio devices start in an unpaused state, since an app has to bind a stream before any audio will flow.

Physical devices can not be paused or unpaused, only logical devices created through SDL_OpenAudioDevice() can be. Physical and invalid device IDs will report themselves as unpaused here.

Returns

true if device is valid and paused, false otherwise.

Thread safety

It is safe to call this function from any thread.

See also

sDL_PauseAudioDevice, sDL_ResumeAudioDevice

C declaration

SDL_AudioDevicePaused, defined at SDL3/SDL_audio.h 855:34

Since: 3.2.0

Get the gain of an audio device.

The gain of a device is its volume; a larger gain means a louder output, with a gain of zero being silence.

Audio devices default to a gain of 1.0f (no change in output).

Physical devices may not have their gain changed, only logical devices, and this function will always return -1.0f when used on physical devices.

Returns

the gain of the device or -1.0f on failure; call SDL_GetError() for more information.

Thread safety

It is safe to call this function from any thread.

See also

sDL_SetAudioDeviceGain

C declaration

SDL_GetAudioDeviceGain, defined at SDL3/SDL_audio.h 878:35

Since: 3.2.0

Change the gain of an audio device.

The gain of a device is its volume; a larger gain means a louder output, with a gain of zero being silence.

Audio devices default to a gain of 1.0f (no change in output).

Physical devices may not have their gain changed, only logical devices, and this function will always return false when used on physical devices. While it might seem attractive to adjust several logical devices at once in this way, it would allow an app or library to interfere with another portion of the program's otherwise-isolated devices.

This is applied, along with any per-audiostream gain, during playback to the hardware, and can be continuously changed to create various effects. On recording devices, this will adjust the gain before passing the data into an audiostream; that recording audiostream can then adjust its gain further when outputting the data elsewhere, if it likes, but that second gain is not applied until the data leaves the audiostream again.

Returns

true on success or false on failure; call SDL_GetError() for more information.

Thread safety

It is safe to call this function from any thread, as it holds a stream-specific mutex while running.

See also

sDL_GetAudioDeviceGain

C declaration

SDL_SetAudioDeviceGain, defined at SDL3/SDL_audio.h 913:34

Since: 3.2.0

Close a previously-opened audio device.

The application should close open audio devices once they are no longer needed.

This function may block briefly while pending audio data is played by the hardware, so that applications don't drop the last buffer of data they supplied if terminating immediately afterwards.

Thread safety

It is safe to call this function from any thread.

See also

sDL_OpenAudioDevice

C declaration

SDL_CloseAudioDevice, defined at SDL3/SDL_audio.h 934:34

Since: 3.2.0

Bind a list of audio streams to an audio device.

Audio data will flow through any bound streams. For a playback device, data for all bound streams will be mixed together and fed to the device. For a recording device, a copy of recorded data will be provided to each bound stream.

Audio streams can only be bound to an open device. This operation is atomic all streams bound in the same call will start processing at the same time, so they can stay in sync. Also: either all streams will be bound or none of them will be.

It is an error to bind an already-bound stream; it must be explicitly unbound first.

Binding a stream to a device will set its output format for playback devices, and its input format for recording devices, so they match the device's settings. The caller is welcome to change the other end of the stream's format at any time with SDL_SetAudioStreamFormat(). If the other end of the stream's format has never been set (the audio stream was created with a NULL audio spec), this function will set it to match the device end's format.

Returns

true on success or false on failure; call SDL_GetError() for more information.

Thread safety

It is safe to call this function from any thread.

See also

sDL_BindAudioStreams, sDL_UnbindAudioStream, sDL_GetAudioStreamDevice

C declaration

SDL_BindAudioStreams, defined at SDL3/SDL_audio.h 974:34

Since: 3.2.0

Bind a single audio stream to an audio device.

This is a convenience function, equivalent to calling sDL_BindAudioStreams (devid, &stream, 1).

Returns

true on success or false on failure; call SDL_GetError() for more information.

Thread safety

It is safe to call this function from any thread.

See also

sDL_BindAudioStreams, sDL_UnbindAudioStream, sDL_GetAudioStreamDevice

C declaration

SDL_BindAudioStream, defined at SDL3/SDL_audio.h 995:34

Since: 3.2.0

Unbind a list of audio streams from their audio devices.

The streams being unbound do not all have to be on the same device. All streams on the same device will be unbound atomically (data will stop flowing through all unbound streams on the same device at the same time).

Unbinding a stream that isn't bound to a device is a legal no-op.

Thread safety

It is safe to call this function from any thread.

See also

sDL_BindAudioStreams

C declaration

SDL_UnbindAudioStreams, defined at SDL3/SDL_audio.h 1016:34

Since: 3.2.0

Unbind a single audio stream from its audio device.

This is a convenience function, equivalent to calling sDL_UnbindAudioStreams (&stream, 1).

Thread safety

It is safe to call this function from any thread.

See also

sDL_BindAudioStream

C declaration

SDL_UnbindAudioStream, defined at SDL3/SDL_audio.h 1032:34

Since: 3.2.0

Query an audio stream for its currently-bound device.

This reports the logical audio device that an audio stream is currently bound to.

If not bound, or invalid, this returns zero, which is not a valid device ID.

Returns

the bound audio device, or 0 if not bound or invalid.

Thread safety

It is safe to call this function from any thread.

See also

sDL_BindAudioStream, sDL_BindAudioStreams

C declaration

SDL_GetAudioStreamDevice, defined at SDL3/SDL_audio.h 1053:47

Since: 3.2.0

Create a new audio stream.

Note that src_spec or dst_spec may be NULL, but any attempts to put or get data from an audio stream will fail until it has valid specs assigned to both ends of the stream. Specs can be assigned later through SDL_SetAudioStreamFormat(), or binding the stream to an audio device (which will set the format of only the input or output, depending on what kind of device the stream was bound to).

Returns

a new audio stream on success or NULL on failure; call SDL_GetError() for more information.

Thread safety

It is safe to call this function from any thread.

See also

sDL_PutAudioStreamData, sDL_GetAudioStreamData, sDL_GetAudioStreamAvailable, sDL_FlushAudioStream, sDL_ClearAudioStream, sDL_SetAudioStreamFormat, sDL_DestroyAudioStream

C declaration

SDL_CreateAudioStream, defined at SDL3/SDL_audio.h 1082:47

Since: 3.2.0

Get the properties associated with an audio stream.

The application can hang any data it wants here, but the following properties are understood by SDL:

• sDL_PROP_AUDIOSTREAM_AUTO_CLEANUP_BOOLEAN: if true (the default), the stream be automatically cleaned up when the audio subsystem quits. If set to false, the streams will persist beyond that. This property is ignored for streams created through SDL_OpenAudioDeviceStream(), and will always be cleaned up. Streams that are not cleaned up will still be unbound from devices when the audio subsystem quits. This property was added in SDL 3.4.0.

Returns

a valid property ID on success or 0 on failure; call SDL_GetError() for more information.

Thread safety

It is safe to call this function from any thread.

C declaration

SDL_GetAudioStreamProperties, defined at SDL3/SDL_audio.h 1106:46

Since: 3.2.0

Query the current format of an audio stream.

Returns

true on success or false on failure; call SDL_GetError() for more information.

Thread safety

It is safe to call this function from any thread, as it holds a stream-specific mutex while running.

See also

sDL_SetAudioStreamFormat

C declaration

SDL_GetAudioStreamFormat, defined at SDL3/SDL_audio.h 1127:34

Since: 3.2.0

Change the input and output formats of an audio stream.

Future calls to and SDL_GetAudioStreamAvailable and SDL_GetAudioStreamData will reflect the new format, and future calls to SDL_PutAudioStreamData must provide data in the new input formats.

Data that was previously queued in the stream will still be operated on in the format that was current when it was added, which is to say you can put the end of a sound file in one format to a stream, change formats for the next sound file, and start putting that new data while the previous sound file is still queued, and everything will still play back correctly.

If a stream is bound to a device, then the format of the side of the stream bound to a device cannot be changed (src_spec for recording devices, dst_spec for playback devices). Attempts to make a change to this side will be ignored, but this will not report an error. The other side's format can be changed.

src_spec and dst_spec may each be NULL; a NULL spec signals not to change the current format for that side of the stream.

Returns

true on success or false on failure; call SDL_GetError() for more information.

Thread safety

It is safe to call this function from any thread, as it holds a stream-specific mutex while running.

See also

sDL_GetAudioStreamFormat, sDL_SetAudioStreamFrequencyRatio

C declaration

SDL_SetAudioStreamFormat, defined at SDL3/SDL_audio.h 1167:34

Since: 3.2.0

Get the frequency ratio of an audio stream.

Returns

the frequency ratio of the stream or 0.0 on failure; call SDL_GetError() for more information.

Thread safety

It is safe to call this function from any thread, as it holds a stream-specific mutex while running.

See also

sDL_SetAudioStreamFrequencyRatio

C declaration

SDL_GetAudioStreamFrequencyRatio, defined at SDL3/SDL_audio.h 1183:35

Since: 3.2.0

Change the frequency ratio of an audio stream.

The frequency ratio is used to adjust the rate at which input data is consumed. Changing this effectively modifies the speed and pitch of the audio. A value greater than 1.0f will play the audio faster, and at a higher pitch. A value less than 1.0f will play the audio slower, and at a lower pitch. 1.0f means play at normal speed.

This is applied during SDL_GetAudioStreamData, and can be continuously changed to create various effects.

Returns

true on success or false on failure; call SDL_GetError() for more information.

Thread safety

It is safe to call this function from any thread, as it holds a stream-specific mutex while running.

See also

sDL_GetAudioStreamFrequencyRatio, sDL_SetAudioStreamFormat

C declaration

SDL_SetAudioStreamFrequencyRatio, defined at SDL3/SDL_audio.h 1211:34

Since: 3.2.0

Get the gain of an audio stream.

The gain of a stream is its volume; a larger gain means a louder output, with a gain of zero being silence.

Audio streams default to a gain of 1.0f (no change in output).

Returns

the gain of the stream or -1.0f on failure; call SDL_GetError() for more information.

Thread safety

It is safe to call this function from any thread, as it holds a stream-specific mutex while running.

See also

sDL_SetAudioStreamGain

C declaration

SDL_GetAudioStreamGain, defined at SDL3/SDL_audio.h 1232:35

Since: 3.2.0

Change the gain of an audio stream.

The gain of a stream is its volume; a larger gain means a louder output, with a gain of zero being silence.

Audio streams default to a gain of 1.0f (no change in output).

This is applied during SDL_GetAudioStreamData, and can be continuously changed to create various effects.

Returns

true on success or false on failure; call SDL_GetError() for more information.

Thread safety

It is safe to call this function from any thread, as it holds a stream-specific mutex while running.

See also

sDL_GetAudioStreamGain

C declaration

SDL_SetAudioStreamGain, defined at SDL3/SDL_audio.h 1257:34

Since: 3.2.0

Get the current input channel map of an audio stream.

Channel maps are optional; most things do not need them, instead passing data in the order that SDL expects.

Audio streams default to no remapping applied. This is represented by returning NULL, and does not signify an error.

Returns

an array of the current channel mapping, with as many elements as the current output spec's channels, or NULL if default. This should be freed with SDL_free() when it is no longer needed.

Thread safety

It is safe to call this function from any thread, as it holds a stream-specific mutex while running.

See also

sDL_SetAudioStreamInputChannelMap

C declaration

SDL_GetAudioStreamInputChannelMap, defined at SDL3/SDL_audio.h 1281:35

Since: 3.2.0

Get the current output channel map of an audio stream.

Channel maps are optional; most things do not need them, instead passing data in the order that SDL expects.

Audio streams default to no remapping applied. This is represented by returning NULL, and does not signify an error.

Returns

an array of the current channel mapping, with as many elements as the current output spec's channels, or NULL if default. This should be freed with SDL_free() when it is no longer needed.

Thread safety

It is safe to call this function from any thread, as it holds a stream-specific mutex while running.

See also

sDL_SetAudioStreamInputChannelMap

C declaration

SDL_GetAudioStreamOutputChannelMap, defined at SDL3/SDL_audio.h 1305:35

Since: 3.2.0

Set the current input channel map of an audio stream.

Channel maps are optional; most things do not need them, instead passing data in the order that SDL expects.

The input channel map reorders data that is added to a stream via SDL_PutAudioStreamData. Future calls to SDL_PutAudioStreamData must provide data in the new channel order.

Each item in the array represents an input channel, and its value is the channel that it should be remapped to. To reverse a stereo signal's left and right values, you'd have an array of { 1, 0 }. It is legal to remap multiple channels to the same thing, so { 1, 1 } would duplicate the right channel to both channels of a stereo signal. An element in the channel map set to -1 instead of a valid channel will mute that channel, setting it to a silence value.

You cannot change the number of channels through a channel map, just reorder/mute them.

Data that was previously queued in the stream will still be operated on in the order that was current when it was added, which is to say you can put the end of a sound file in one order to a stream, change orders for the next sound file, and start putting that new data while the previous sound file is still queued, and everything will still play back correctly.

Audio streams default to no remapping applied. Passing a NULL channel map is legal, and turns off remapping.

SDL will copy the channel map; the caller does not have to save this array after this call.

If count is not equal to the current number of channels in the audio stream's format, this will fail. This is a safety measure to make sure a race condition hasn't changed the format while this call is setting the channel map.

Unlike attempting to change the stream's format, the input channel map on a stream bound to a recording device is permitted to change at any time; any data added to the stream from the device after this call will have the new mapping, but previously-added data will still have the prior mapping.

Returns

true on success or false on failure; call SDL_GetError() for more information.

Thread safety

It is safe to call this function from any thread, as it holds a stream-specific mutex while running. Don't change the stream's format to have a different number of channels from a different thread at the same time, though!

See also

sDL_SetAudioStreamOutputChannelMap

C declaration

SDL_SetAudioStreamInputChannelMap, defined at SDL3/SDL_audio.h 1365:34

Since: 3.2.0

Set the current output channel map of an audio stream.

Channel maps are optional; most things do not need them, instead passing data in the order that SDL expects.

The output channel map reorders data that is leaving a stream via SDL_GetAudioStreamData.

Each item in the array represents an input channel, and its value is the channel that it should be remapped to. To reverse a stereo signal's left and right values, you'd have an array of { 1, 0 }. It is legal to remap multiple channels to the same thing, so { 1, 1 } would duplicate the right channel to both channels of a stereo signal. An element in the channel map set to -1 instead of a valid channel will mute that channel, setting it to a silence value.

You cannot change the number of channels through a channel map, just reorder/mute them.

The output channel map can be changed at any time, as output remapping is applied during SDL_GetAudioStreamData.

Audio streams default to no remapping applied. Passing a NULL channel map is legal, and turns off remapping.

SDL will copy the channel map; the caller does not have to save this array after this call.

If count is not equal to the current number of channels in the audio stream's format, this will fail. This is a safety measure to make sure a race condition hasn't changed the format while this call is setting the channel map.

Unlike attempting to change the stream's format, the output channel map on a stream bound to a recording device is permitted to change at any time; any data added to the stream after this call will have the new mapping, but previously-added data will still have the prior mapping. When the channel map doesn't match the hardware's channel layout, SDL will convert the data before feeding it to the device for playback.

Returns

true on success or false on failure; call SDL_GetError() for more information.

Thread safety

It is safe to call this function from any thread, as it holds a stream-specific mutex while running. Don't change the stream's format to have a different number of channels from a a different thread at the same time, though!

See also

sDL_SetAudioStreamInputChannelMap

C declaration

SDL_SetAudioStreamOutputChannelMap, defined at SDL3/SDL_audio.h 1423:34

Since: 3.2.0

Add data to the stream.

This data must match the format/channels/samplerate specified in the latest call to SDL_SetAudioStreamFormat, or the format specified when creating the stream if it hasn't been changed.

Note that this call simply copies the unconverted data for later. This is different than SDL2, where data was converted during the Put call and the Get call would just dequeue the previously-converted data.

Returns

true on success or false on failure; call SDL_GetError() for more information.

Thread safety

It is safe to call this function from any thread, but if the stream has a callback set, the caller might need to manage extra locking.

See also

sDL_ClearAudioStream, sDL_FlushAudioStream, sDL_GetAudioStreamData, sDL_GetAudioStreamQueued

C declaration

SDL_PutAudioStreamData, defined at SDL3/SDL_audio.h 1453:34

Since: 3.2.0

Add external data to an audio stream without copying it.

Unlike SDL_PutAudioStreamData(), this function does not make a copy of the provided data, instead storing the provided pointer. This means that the put operation does not need to allocate and copy the data, but the original data must remain available until the stream is done with it, either by being read from the stream in its entirety, or a call to SDL_ClearAudioStream() or SDL_DestroyAudioStream().

The data must match the format/channels/samplerate specified in the latest call to SDL_SetAudioStreamFormat, or the format specified when creating the stream if it hasn't been changed.

An optional callback may be provided, which is called when the stream no longer needs the data. Once this callback fires, the stream will not access the data again. This callback will fire for any reason the data is no longer needed, including clearing or destroying the stream.

Note that there is still an allocation to store tracking information, so this function is more efficient for larger blocks of data. If you're planning to put a few samples at a time, it will be more efficient to use SDL_PutAudioStreamData(), which allocates and buffers in blocks.

Returns

true on success or false on failure; call SDL_GetError() for more information.

Thread safety

It is safe to call this function from any thread, but if the stream has a callback set, the caller might need to manage extra locking.

See also

sDL_ClearAudioStream, sDL_FlushAudioStream, sDL_GetAudioStreamData, sDL_GetAudioStreamQueued

C declaration

SDL_PutAudioStreamDataNoCopy, defined at SDL3/SDL_audio.h 1530:34

Since: 3.4.0

Add data to the stream with each channel in a separate array.

This data must match the format/channels/samplerate specified in the latest call to SDL_SetAudioStreamFormat, or the format specified when creating the stream if it hasn't been changed.

The data will be interleaved and queued. Note that SDL_AudioStream only operates on interleaved data, so this is simply a convenience function for easily queueing data from sources that provide separate arrays. There is no equivalent function to retrieve planar data.

The arrays in channel_buffers are ordered as they are to be interleaved; the first array will be the first sample in the interleaved data. Any individual array may be NULL; in this case, silence will be interleaved for that channel.

num_channels specifies how many arrays are in channel_buffers. This can be used as a safety to prevent overflow, in case the stream format has changed elsewhere. If more channels are specified than the current input spec, they are ignored. If less channels are specified, the missing arrays are treated as if they are NULL (silence is written to those channels). If the count is -1, SDL will assume the array count matches the current input spec.

Note that num_samples is the number of samples per array. This can also be thought of as the number of sample frames to be queued. A value of 1 with stereo arrays will queue two samples to the stream. This is different than SDL_PutAudioStreamData, which wants the size of a single array in bytes.

Returns

true on success or false on failure; call SDL_GetError() for more information.

Thread safety

It is safe to call this function from any thread, but if the stream has a callback set, the caller might need to manage extra locking.

See also

sDL_ClearAudioStream, sDL_FlushAudioStream, sDL_GetAudioStreamData, sDL_GetAudioStreamQueued

C declaration

SDL_PutAudioStreamPlanarData, defined at SDL3/SDL_audio.h 1583:34

Since: 3.4.0

Get converted/resampled data from the stream.

The input/output data format/channels/samplerate is specified when creating the stream, and can be changed after creation by calling SDL_SetAudioStreamFormat.

Note that any conversion and resampling necessary is done during this call, and SDL_PutAudioStreamData simply queues unconverted data for later. This is different than SDL2, where that work was done while inputting new data to the stream and requesting the output just copied the converted data.

Returns

the number of bytes read from the stream or -1 on failure; call SDL_GetError() for more information.

Thread safety

It is safe to call this function from any thread, but if the stream has a callback set, the caller might need to manage extra locking.

See also

sDL_ClearAudioStream, sDL_GetAudioStreamAvailable, sDL_PutAudioStreamData

C declaration

SDL_GetAudioStreamData, defined at SDL3/SDL_audio.h 1613:33

Since: 3.2.0

Get the number of converted/resampled bytes available.

The stream may be buffering data behind the scenes until it has enough to resample correctly, so this number might be lower than what you expect, or even be zero. Add more data or flush the stream if you need the data now.

If the stream has so much data that it would overflow an int, the return value is clamped to a maximum value, but no queued data is lost; if there are gigabytes of data queued, the app might need to read some of it with SDL_GetAudioStreamData before this function's return value is no longer clamped.

Returns

the number of converted/resampled bytes available or -1 on failure; call SDL_GetError() for more information.

Thread safety

It is safe to call this function from any thread.

See also

sDL_GetAudioStreamData, sDL_PutAudioStreamData

C declaration

SDL_GetAudioStreamAvailable, defined at SDL3/SDL_audio.h 1639:33

Since: 3.2.0

Get the number of bytes currently queued.

This is the number of bytes put into a stream as input, not the number that can be retrieved as output. Because of several details, it's not possible to calculate one number directly from the other. If you need to know how much usable data can be retrieved right now, you should use SDL_GetAudioStreamAvailable() and not this function.

Note that audio streams can change their input format at any time, even if there is still data queued in a different format, so the returned byte count will not necessarily match the number of sample frames available. Users of this API should be aware of format changes they make when feeding a stream and plan accordingly.

Queued data is not converted until it is consumed by SDL_GetAudioStreamData, so this value should be representative of the exact data that was put into the stream.

If the stream has so much data that it would overflow an int, the return value is clamped to a maximum value, but no queued data is lost; if there are gigabytes of data queued, the app might need to read some of it with SDL_GetAudioStreamData before this function's return value is no longer clamped.

Returns

the number of bytes queued or -1 on failure; call SDL_GetError() for more information.

Thread safety

It is safe to call this function from any thread.

See also

sDL_PutAudioStreamData, sDL_ClearAudioStream

C declaration

SDL_GetAudioStreamQueued, defined at SDL3/SDL_audio.h 1678:33

Since: 3.2.0

Tell the stream that you're done sending data, and anything being buffered should be converted/resampled and made available immediately.

It is legal to add more data to a stream after flushing, but there may be audio gaps in the output. Generally this is intended to signal the end of input, so the complete output becomes available.

Returns

true on success or false on failure; call SDL_GetError() for more information.

Thread safety

It is safe to call this function from any thread.

See also

sDL_PutAudioStreamData

C declaration

SDL_FlushAudioStream, defined at SDL3/SDL_audio.h 1699:34

Since: 3.2.0

Clear any pending data in the stream.

This drops any queued data, so there will be nothing to read from the stream until more is added.

Returns

true on success or false on failure; call SDL_GetError() for more information.

Thread safety

It is safe to call this function from any thread.

See also

sDL_GetAudioStreamAvailable, sDL_GetAudioStreamData, sDL_GetAudioStreamQueued, sDL_PutAudioStreamData

C declaration

SDL_ClearAudioStream, defined at SDL3/SDL_audio.h 1720:34

Since: 3.2.0

Use this function to pause audio playback on the audio device associated with an audio stream.

This function pauses audio processing for a given device. Any bound audio streams will not progress, and no audio will be generated. Pausing one device does not prevent other unpaused devices from running.

Pausing a device can be useful to halt all audio without unbinding all the audio streams. This might be useful while a game is paused, or a level is loading, etc.

Returns

true on success or false on failure; call SDL_GetError() for more information.

Thread safety

It is safe to call this function from any thread.

See also

sDL_ResumeAudioStreamDevice

C declaration

SDL_PauseAudioStreamDevice, defined at SDL3/SDL_audio.h 1744:34

Since: 3.2.0

Use this function to unpause audio playback on the audio device associated with an audio stream.

This function unpauses audio processing for a given device that has previously been paused. Once unpaused, any bound audio streams will begin to progress again, and audio can be generated.

SDL_OpenAudioDeviceStream opens audio devices in a paused state, so this function call is required for audio playback to begin on such devices.

Returns

true on success or false on failure; call SDL_GetError() for more information.

Thread safety

It is safe to call this function from any thread.

See also

sDL_PauseAudioStreamDevice

C declaration

SDL_ResumeAudioStreamDevice, defined at SDL3/SDL_audio.h 1767:34

Since: 3.2.0

Use this function to query if an audio device associated with a stream is paused.

Unlike in SDL2, audio devices start in an unpaused state, since an app has to bind a stream before any audio will flow.

Returns

true if device is valid and paused, false otherwise.

Thread safety

It is safe to call this function from any thread.

See also

sDL_PauseAudioStreamDevice, sDL_ResumeAudioStreamDevice

C declaration

SDL_AudioStreamDevicePaused, defined at SDL3/SDL_audio.h 1786:34

Since: 3.2.0

Lock an audio stream for serialized access.

Each SDL_AudioStream has an internal mutex it uses to protect its data structures from threading conflicts. This function allows an app to lock that mutex, which could be useful if registering callbacks on this stream.

One does not need to lock a stream to use in it most cases, as the stream manages this lock internally. However, this lock is held during callbacks, which may run from arbitrary threads at any time, so if an app needs to protect shared data during those callbacks, locking the stream guarantees that the callback is not running while the lock is held.

As this is just a wrapper over SDL_LockMutex for an internal lock; it has all the same attributes (recursive locks are allowed, etc).

Returns

true on success or false on failure; call SDL_GetError() for more information.

Thread safety

It is safe to call this function from any thread.

See also

sDL_UnlockAudioStream

C declaration

SDL_LockAudioStream, defined at SDL3/SDL_audio.h 1815:34

Since: 3.2.0

Unlock an audio stream for serialized access.

This unlocks an audio stream after a call to SDL_LockAudioStream.

Returns

true on success or false on failure; call SDL_GetError() for more information.

Thread safety

You should only call this from the same thread that previously called SDL_LockAudioStream.

See also

sDL_LockAudioStream

C declaration

SDL_UnlockAudioStream, defined at SDL3/SDL_audio.h 1834:34

Since: 3.2.0

Set a callback that runs when data is requested from an audio stream.

This callback is called before data is obtained from the stream, giving the callback the chance to add more on-demand.

The callback can (optionally) call SDL_PutAudioStreamData() to add more audio to the stream during this call; if needed, the request that triggered this callback will obtain the new data immediately.

The callback's additional_amount argument is roughly how many bytes of unconverted data (in the stream's input format) is needed by the caller, although this may overestimate a little for safety. This takes into account how much is already in the stream and only asks for any extra necessary to resolve the request, which means the callback may be asked for zero bytes, and a different amount on each call.

The callback is not required to supply exact amounts; it is allowed to supply too much or too little or none at all. The caller will get what's available, up to the amount they requested, regardless of this callback's outcome.

Clearing or flushing an audio stream does not call this callback.

This function obtains the stream's lock, which means any existing callback (get or put) in progress will finish running before setting the new callback.

Setting a NULL function turns off the callback.

Returns

true on success or false on failure; call SDL_GetError() for more information. This only fails if stream is NULL.

Thread safety

It is safe to call this function from any thread.

See also

sDL_SetAudioStreamPutCallback

C declaration

SDL_SetAudioStreamGetCallback, defined at SDL3/SDL_audio.h 1924:34

Since: 3.2.0

Set a callback that runs when data is added to an audio stream.

This callback is called after the data is added to the stream, giving the callback the chance to obtain it immediately.

The callback can (optionally) call SDL_GetAudioStreamData() to obtain audio from the stream during this call.

The callback's additional_amount argument is how many bytes of converted data (in the stream's output format) was provided by the caller, although this may underestimate a little for safety. This value might be less than what is currently available in the stream, if data was already there, and might be less than the caller provided if the stream needs to keep a buffer to aid in resampling. Which means the callback may be provided with zero bytes, and a different amount on each call.

The callback may call SDL_GetAudioStreamAvailable to see the total amount currently available to read from the stream, instead of the total provided by the current call.

The callback is not required to obtain all data. It is allowed to read less or none at all. Anything not read now simply remains in the stream for later access.

Clearing or flushing an audio stream does not call this callback.

This function obtains the stream's lock, which means any existing callback (get or put) in progress will finish running before setting the new callback.

Setting a NULL function turns off the callback.

Returns

true on success or false on failure; call SDL_GetError() for more information. This only fails if stream is NULL.

Thread safety

It is safe to call this function from any thread.

See also

sDL_SetAudioStreamGetCallback

C declaration

SDL_SetAudioStreamPutCallback, defined at SDL3/SDL_audio.h 1973:34

Since: 3.2.0

Free an audio stream.

This will release all allocated data, including any audio that is still queued. You do not need to manually clear the stream first.

If this stream was bound to an audio device, it is unbound during this call. If this stream was created with SDL_OpenAudioDeviceStream, the audio device that was opened alongside this stream's creation will be closed, too.

Thread safety

It is safe to call this function from any thread.

See also

sDL_CreateAudioStream

C declaration

SDL_DestroyAudioStream, defined at SDL3/SDL_audio.h 1995:34

Since: 3.2.0

Convenience function for straightforward audio init for the common case.

If all your app intends to do is provide a single source of PCM audio, this function allows you to do all your audio setup in a single call.

This is also intended to be a clean means to migrate apps from SDL2.

This function will open an audio device, create a stream and bind it. Unlike other methods of setup, the audio device will be closed when this stream is destroyed, so the app can treat the returned SDL_AudioStream as the only object needed to manage audio playback.

Also unlike other functions, the audio device begins paused. This is to map more closely to SDL2-style behavior, since there is no extra step here to bind a stream to begin audio flowing. The audio device should be resumed with SDL_ResumeAudioStreamDevice().

This function works with both playback and recording devices.

The spec parameter represents the app's side of the audio stream. That is, for recording audio, this will be the output format, and for playing audio, this will be the input format. If spec is NULL, the system will choose the format, and the app can use SDL_GetAudioStreamFormat() to obtain this information later.

If you don't care about opening a specific audio device, you can (and probably should), use SDL_AUDIO_DEVICE_DEFAULT_PLAYBACK for playback and SDL_AUDIO_DEVICE_DEFAULT_RECORDING for recording.

One can optionally provide a callback function; if NULL, the app is expected to queue audio data for playback (or unqueue audio data if capturing). Otherwise, the callback will begin to fire once the device is unpaused.

Destroying the returned stream with SDL_DestroyAudioStream will also close the audio device associated with this stream.

Returns

an audio stream on success, ready to use, or NULL on failure; call SDL_GetError() for more information. When done with this stream, call SDL_DestroyAudioStream to free resources and close the device.

Thread safety

It is safe to call this function from any thread.

See also

sDL_GetAudioStreamDevice, sDL_ResumeAudioStreamDevice

C declaration

SDL_OpenAudioDeviceStream, defined at SDL3/SDL_audio.h 2058:47

Since: 3.2.0

Set a callback that fires when data is about to be fed to an audio device.

This is useful for accessing the final mix, perhaps for writing a visualizer or applying a final effect to the audio data before playback.

The buffer is the final mix of all bound audio streams on an opened device; this callback will fire regularly for any device that is both opened and unpaused. If there is no new data to mix, either because no streams are bound to the device or all the streams are empty, this callback will still fire with the entire buffer set to silence.

This callback is allowed to make changes to the data; the contents of the buffer after this call is what is ultimately passed along to the hardware.

The callback is always provided the data in float format (values from -1.0f to 1.0f), but the number of channels or sample rate may be different than the format the app requested when opening the device; SDL might have had to manage a conversion behind the scenes, or the playback might have jumped to new physical hardware when a system default changed, etc. These details may change between calls. Accordingly, the size of the buffer might change between calls as well.

This callback can run at any time, and from any thread; if you need to serialize access to your app's data, you should provide and use a mutex or other synchronization device.

All of this to say: there are specific needs this callback can fulfill, but it is not the simplest interface. Apps should generally provide audio in their preferred format through an SDL_AudioStream and let SDL handle the difference.

This function is extremely time-sensitive; the callback should do the least amount of work possible and return as quickly as it can. The longer the callback runs, the higher the risk of audio dropouts or other problems.

This function will block until the audio device is in between iterations, so any existing callback that might be running will finish before this function sets the new callback and returns.

Setting a NULL callback function disables any previously-set callback.

Returns

true on success or false on failure; call SDL_GetError() for more information.

Thread safety

It is safe to call this function from any thread.

C declaration

SDL_SetAudioPostmixCallback, defined at SDL3/SDL_audio.h 2149:34

Since: 3.2.0

Load the audio data of a WAVE file into memory.

Loading a WAVE file requires src, spec, audio_buf and audio_len to be valid pointers. The entire data portion of the file is then loaded into memory and decoded if necessary.

Supported formats are RIFF WAVE files with the formats PCM (8, 16, 24, and 32 bits), IEEE Float (32 bits), Microsoft ADPCM and IMA ADPCM (4 bits), and A-law and mu-law (8 bits). Other formats are currently unsupported and cause an error.

If this function succeeds, the return value is zero and the pointer to the audio data allocated by the function is written to audio_buf and its length in bytes to audio_len. The SDL_AudioSpec members freq, channels, and format are set to the values of the audio data in the buffer.

It's necessary to use SDL_free() to free the audio data returned in audio_buf when it is no longer used.

Because of the underspecification of the .WAV format, there are many problematic files in the wild that cause issues with strict decoders. To provide compatibility with these files, this decoder is lenient in regards to the truncation of the file, the fact chunk, and the size of the RIFF chunk. The hints SDL_HINT_WAVE_RIFF_CHUNK_SIZE, SDL_HINT_WAVE_TRUNCATION, and SDL_HINT_WAVE_FACT_CHUNK can be used to tune the behavior of the loading process.

Any file that is invalid (due to truncation, corruption, or wrong values in the headers), too big, or unsupported causes an error. Additionally, any critical I/O error from the data source will terminate the loading process with an error. The function returns NULL on error and in all cases (with the exception of src being NULL), an appropriate error message will be set.

It is required that the data source supports seeking.

Example:

    SDL_LoadWAV_IO(SDL_IOFromFile("sample.wav", "rb"), true, &spec, &buf, &len);
    

Note that the SDL_LoadWAV function does this same thing for you, but in a less messy way:

    SDL_LoadWAV("sample.wav", &spec, &buf, &len);
    

This function returns false if the .WAV file cannot be opened, uses an unknown data format, or is corrupt; call SDL_GetError() for more information.

Returns

true on success. audio_buf will be filled with a pointer to an allocated buffer containing the audio data, and audio_len is filled with the length of that audio buffer in bytes.

When the application is done with the data returned in audio_buf, it should call SDL_free() to dispose of it.

Thread safety

It is safe to call this function from any thread.

See also

SDL_free, sDL_LoadWAV

C declaration

SDL_LoadWAV_IO, defined at SDL3/SDL_audio.h 2230:34

Since: 3.2.0

Loads a WAV from a file path.

This is a convenience function that is effectively the same as:

    SDL_LoadWAV_IO(SDL_IOFromFile(path, "rb"), true, spec, audio_buf, audio_len);
    

This function returns false if the .WAV file cannot be opened, uses an unknown data format, or is corrupt; call SDL_GetError() for more information.

Returns

true on success. audio_buf will be filled with a pointer to an allocated buffer containing the audio data, and audio_len is filled with the length of that audio buffer in bytes.

When the application is done with the data returned in audio_buf, it should call SDL_free() to dispose of it.

Thread safety

It is safe to call this function from any thread.

See also

SDL_free, sDL_LoadWAV_IO

C declaration

SDL_LoadWAV, defined at SDL3/SDL_audio.h 2266:34

Since: 3.2.0

Mix audio data in a specified format.

This takes an audio buffer src of len bytes of format data and mixes it into dst, performing addition, volume adjustment, and overflow clipping. The buffer pointed to by dst must also be len bytes of format data.

This is provided for convenience you can mix your own audio data.

Do not use this function for mixing together more than two streams of sample data. The output from repeated application of this function may be distorted by clipping, because there is no accumulator with greater range than the input (not to mention this being an inefficient way of doing it).

It is a common misconception that this function is required to write audio data to an output stream in an audio callback. While you can do that, SDL_MixAudio() is really only needed when you're mixing a single audio stream with a volume adjustment.

Returns

true on success or false on failure; call SDL_GetError() for more information.

Thread safety

It is safe to call this function from any thread.

C declaration

SDL_MixAudio, defined at SDL3/SDL_audio.h 2302:34

Since: 3.2.0

Convert some audio data of one format to another format.

Please note that this function is for convenience, but should not be used to resample audio in blocks, as it will introduce audio artifacts on the boundaries. You should only use this function if you are converting audio data in its entirety in one call. If you want to convert audio in smaller chunks, use an SDL_AudioStream, which is designed for this situation.

Internally, this function creates and destroys an SDL_AudioStream on each use, so it's also less efficient than using one directly, if you need to convert multiple times.

Returns

true on success or false on failure; call SDL_GetError() for more information.

Thread safety

It is safe to call this function from any thread.

C declaration

SDL_ConvertAudioSamples, defined at SDL3/SDL_audio.h 2332:34

Since: 3.2.0

Get the human readable name of an audio format.

Returns

the human readable name of the specified audio format or "SDL_AUDIO_UNKNOWN" if the format isn't recognized.

Thread safety

It is safe to call this function from any thread.

C declaration

SDL_GetAudioFormatName, defined at SDL3/SDL_audio.h 2345:42

Since: 3.2.0

Get the appropriate memset value for silencing an audio format.

The value returned by this function can be used as the second argument to memset (or SDL_memset) to set an audio buffer in a specific format to silence.

Returns

a byte value that can be passed to memset.

Thread safety

It is safe to call this function from any thread.

C declaration

SDL_GetSilenceValueForFormat, defined at SDL3/SDL_audio.h 2361:33

Since: 3.2.0